Renewable Energy Technology Selection for Hotel Buildings: A Systematic Approach Based on AHP and VIKOR Methods

Abstract

This study provides an assessment of renewable energy technology utilization in hotel buildings, which are significant structures in terms of energy consumption. The aim of the study is to determine suitable renewable energy technologies (RETs) for hotel buildings by defining criteria for evaluating RETs, assessing the relative importance of these criteria, and proposing a multi-criteria decision-making framework to solve the problem of selecting the most appropriate RETs during the design stage. The alternatives for RETs and the criteria for their evaluation are gathered through a literature review and expert consultations. Eight fundamental RETs used in hotel buildings (such as heat pumps, solar panels, biomass boilers, etc.) are examined, and nine selection criteria are analyzed. According to the weights determined by the Analytic Hierarchy Process (AHP) method, the initial investment cost is the most influential decision criterion, with a weight of 0.314. As a result of applying the AHP and VIKOR (Multi-Criteria Optimization and Compromise Solution) methods for technology selection, photovoltaic panels emerge as the top-ranked choice. This comprehensive evaluation provides stakeholders in the building production process of hotel buildings with detailed analyses and multi-criteria decision-making methods for selecting RETs.

1. Introduction

Energy consumption, environmental pollution, and the depletion of natural resources emerge as critical issues, especially within the construction sector. The building industry bears substantial responsibility for these environmental problems, and the use of renewable energy technologies is becoming increasingly important. The European Union’s 2030 targets and commitments under the Paris Agreement [1,2] highlight the necessity for buildings to achieve near-zero energy consumption and mandate the integration of renewable energy technologies [3].

The tourism sector, a vital component of the global economy with rising energy demands, includes energy-intensive hotel buildings, which represent significant consumers and must address environmental impacts in terms of sustainability and energy efficiency [4,5,6]. The integration of renewable energy alternatives in these buildings is essential [7,8,9,10], given that energy costs constitute the largest expenditure after personnel costs [5]. Fluctuations in energy prices can significantly impact hotel operating costs [8]. Renewable energy offers an economic advantage by reducing energy procurement costs and enhancing potential revenue from electricity generated by renewable sources [5]. Energy consumption in hotel buildings is notably concentrated in areas such as heating, cooling, lighting, ventilation, cooking, hot water, and electrical equipment [11,12].

The increasing energy demands of hotel buildings necessitate efficient and sustainable solutions. However, there are some challenges in the technology decision-making process regarding the use of RETs in hotel buildings. During the decision-making phase, many stakeholders may choose RETs within the framework of environmental awareness and legal regulations. As with any technological decision, the perspective of the actors involved influences this choice. The actors in this process have different viewpoints and priorities, and the final decision is a collective agreement among them. This study aims to provide a systematic approach for these actors in selecting these technologies by focusing on RET decisions during the design phase. In this way, an appropriate RET can be determined to contribute to sustainability goals by shifting energy consumption in hotel buildings toward renewable sources. To this end, integrated AHP and VIKOR methods, which allow for the evaluation of both personal judgments and quantitative data, are utilized. Within this scope, RET options that can be preferred in the hotel building design process are analyzed based on usage criteria. The analysis and selection of RETs in hotel buildings are critical for achieving the goal of net-zero energy buildings. While the literature contains various studies on RETs and their integration into buildings, these studies predominantly focus on residential and commercial buildings. Studies addressing the specific requirements and constraints of hotel buildings are limited. Previous studies often overlook certain criteria and technologies specific to hotel buildings. A search conducted in the MDPI and Science Direct databases revealed only a few studies that do not include comprehensive analysis and decision-making methods. Consequently, there is a critical need for extensive research on the analysis of RETs within the architectural design process of hotel buildings, the development of selection methodologies, and the promotion of these technologies to achieve net-zero energy targets.

The tourism sector has experienced significant expansion over the last 60 years, leading to increased energy consumption and making environmentally friendly consumption habits more important [13,14,15,16]. Environmentally sustainable hotel designs not only enhance environmental protection and reduce energy consumption but also instill a sense of environmental responsibility in visitors, thereby attracting tourists [13,17,18]. This study is designed to address the problem of RET selection decisions in hotel buildings and to fill the gap in the literature regarding the lack of studies that provide a detailed analysis of the subject by experts involved in RET decision-making during the building production process. The novelty of the study lies in the application of a new combination of methods to solve the RET selection decision problem in hotel buildings.

2. Materials and Methods

RET selection, akin to other decision-making processes in building production, is a complex, multi-stakeholder process involving both qualitative and quantitative data. A literature review identifies existing problems and gaps, revealing that RET selection is influenced by information, technology, value systems, regulations, policies, and multiple actors. Consequently, a combination of literature review and expert interviews is utilized to identify technology alternatives and determine influencing criteria. Technologies such as heat pumps, solar panels, biomass boilers, micro-hydropower, and small-scale wind turbines are evaluated based on economic, environmental, and technological criteria. In the building production process, the criteria for selecting RETs are assessed from the perspectives of all stakeholders, which is why the expert group includes representatives from all relevant parties. The significance and relevance of these criteria vary among stakeholders. In the building sector, evaluation is defined as the deliberate identification of the interactions between value systems of groups such as property owners and users. For scientifically based assessments in this sector, benefit-based methods, cost-based methods, and multi-criteria decision-making (MCDM) approaches are utilized. This study opts for MCDM to provide a comprehensive evaluation. The integrated AHP and VIKOR method is chosen for its ability to incorporate both subjective and objective thoughts of the actors, to logically integrate the decision-makers’ knowledge, experience, and intuition, and to facilitate the decision-making process with simple mathematical calculations. The AHP method is applied to compare and rank technologies according to the determined criteria, and technologies are subsequently ranked and solutions identified using AHP and VIKOR. The study methodology is summarized in

Table 1. Research methodology.

	Research Steps	Methodology
Qualitative Research	Problem identification	Literature review
	Objectives definition	Expert group interviews
	Scope determination	Observations
	Determination of the research method
	Research design
Quantitative Research	Determination of RETs	Field study
	Creation of scenarios with different RETs for the hotel building	Field study
	Determination of the renewable energy technology criteria	Field study
	Solving the problem of selecting RETs for the hotel building	Multi-criteria decision-making framework
	Determination of criteria weights	AHP
	Decision-making	AHP-VIKOR

.

In the first stage of the study, the literature is reviewed; in the second stage, consultations with an expert group are conducted; and finally, the decision-making proposal is implemented.

2.1. Literature Review

This section contains theoretical information on RETs used in hotel buildings and the criteria influencing the decision-making process for technology selection.

2.1.1. Renewable Energy Technologies for Hotel Buildings

Renewable energy sources are considered “clean” energy, ensuring sustainable production and minimal primary energy use. Implementing RETs in buildings is the most sustainable, environmentally friendly, and economically beneficial method to meet energy needs. Recent global awareness highlights the significance of RETs, especially in isolated areas where utilizing locally available resources is optimal [10,19,20,21]. Focusing on renewable energy reduces the consumption of limited fuel resources and limits greenhouse gas emissions [15]. Technologies such as solar, wind, biomass, marine, and hydro are now preferred over traditional energy sources [22]. Commonly integrated renewable energy types in buildings aiming for net-zero energy or emissions include solar, wind, geothermal, and biomass [23]. Hybrid renewable energy technologies provide reliable, green systems for isolated areas [24]. To meet hotels’ energy needs like heating, cooling, hot water, and lighting, equipment such as heat pumps, solar thermal panels, photovoltaic panels, solar-powered absorption chillers, biomass boilers, micro-hydro-electric systems, and small-scale wind turbines are utilized [12].

The development of renewable energy sources like biomass, soil, water, air, and algae–bacteria consortia each has unique advantages and disadvantages. Biomass energy supports waste management by converting organic materials into energy. Hydroelectric energy, while sustainable, has controversial environmental impacts. Wind and solar energy are clean but require storage systems due to intermittency. Wind energy has high installation but low operational costs, while geothermal energy is reliable and continuous. Using algae and bacteria for biofuel production represents an innovative approach that is still in the research stage [25].

Net-Zero Energy Buildings (NZEBs) utilize solar, wind, geothermal, and biomass to meet energy demands, with hybrid systems integrating multiple renewable sources to address supply and demand disparities. Solar energy is favored for its availability and diverse integration methods [23]. Technologies like rooftop PV installations, renewable systems with hydrogen storage, and systems with reversible solid oxide cells offer economic benefits while reducing energy crisis risk and public grid stress [5]. Solar, bioenergy, and wind turbines are prominent for reducing carbon emissions and energy consumption, enhancing energy security through grid integration and hybrid systems [15]. For hotel electrification, hybrid PV, wind, battery, and diesel systems are described [26]. The feasibility of coastal zero-energy hotels supported by hybrid wind–wave systems shows the potential for wave and wind integration [27].

In the hotel sector, photovoltaic panels and solar water heating systems are popular, with additional technologies like tidal wave energy, rooftop and ground-mounted solar panels, wind turbines, heat pumps, and anaerobic digestion for waste biomass [28]. Hybrid systems with wind–PV generators and batteries [29], integrated geothermal and solar systems for seasonal demand [30], and net-zero energy tourist facilities using wind–PV systems supported by wood gasification, battery, and hydrogen storage [31] demonstrate various approaches. Tidal current generators [32] and increased use of geothermal energy and biofuel applications are also explored to promote sustainable tourism development [33].

2.1.2. Criteria Related to Renewable Energy Technologies

The selection of RETs for hotel buildings is based on specific criteria encompassing economic, environmental, and technological factors. Economic criteria include initial investment costs, which refer to the initial setup and equipment costs associated with the technology [25,34,35,36,37], with lower capital costs being advantageous [15]. Component replacements, necessary throughout the project lifecycle [36], and operation and maintenance costs, related to regular maintenance and operational expenses such as electricity costs over the year [25,30], are also considered. Low operation and maintenance costs contribute to long-term economic benefits [15]. Fuel costs associated with the technology when required [36] and the payback period, or the time it takes for the investment to pay for itself [34,35,36], are critically important for economic sustainability. Short payback periods ensure rapid returns on investment [15], which is particularly beneficial for high-energy-consuming hotel buildings [35].

Technological criteria focus on the performance and efficiency of RETs, which are crucial for meeting the energy demands of high-energy-consuming hotel buildings [15,25,36]. The capacity of technologies to provide sufficient and reliable power significantly influences decision-making [36], and the reliability of the energy supply is vital for hotel operations [15]. High-capacity production technologies are selected to meet significant energy needs [36], with some hotels achieving 100% self-sufficiency with appropriate PV power and storage capacity [3]. The durability and lifespan of technologies, typically 25–30 years [15,25,34], enhance investment returns and economic sustainability [15]. Technologies should also have low failure rates, be user-friendly, require minimal maintenance, and be easy to manage [34].

Environmental criteria consider the potential risks to the ecosystem, visual disturbances, and noise from the energy system [25]. The impact on carbon emissions, waste management, and natural resource consumption is crucial for environmental sustainability [15]. Sustainable hotel operations require appropriately planned and designed environmental protection practices [33]. Global and local policies, government subsidies, and loans significantly influence the adoption of RETs [34]. High government incentives and grid electricity costs encourage hotels to adopt these technologies [38,39]. Hotels should focus on being environmentally friendly and implementing eco-friendly practices to promote sustainable tourism development [33]. Evaluating these criteria is essential for determining the most suitable RETs for hotel buildings.

2.2. Expert Group Interviews

To determine the criteria and technology alternatives addressed in the study, expert group interviews are conducted. Through this method, a comprehensive framework for RET implementation in hotel buildings is developed during the design phase, and selection criteria are established by analyzing the perspectives of all stakeholders influencing the decision-making process. This method is critical due to the involvement of numerous actors and the significant impact of their perspectives on the final outcomes. Participants are selected from among architects, investors, employers, engineers, consultants, hotel technical teams, and RET producers involved in hotel building development, as detailed in

Table 2. Participants ınterviewed in-depth discussions.

	Role in RET System	Profession	Experience	Company
A1	Designer	Architect	20 year	Private
A2	Designer and builder	Architect	15 year	Public
E1	Designer and builder	Engineer (Mech.)	20 year	Private
E2	Designer and builder	Engineer (Mech.)	25 year	Public
E3	Designer and builder	Engineer (Elec.)	20 year	Private
E4	Designer and builder	Engineer (Elec.)	15 year	Private
I1	Investor	Hotel investor	30 year	Private
I2	Investor	Hotel investor	25 year	Private
C1	Designer and builder	Consultant	20 year	Private
C2	Designer and builder	Consultant	25 year	Private
M1	Designer and builder	RET system manufacturer	20 year	Private
M2	Designer and builder	RET system manufacturer	25 year	Private
T1	Occupant	Hotel maintenance staff	15 year	Private
T2	Occupant	Hotel maintenance staff	20 year	Private

. Selection criteria include having at least 10 years of experience in the sector, involvement in international projects, experience with hotel operations, and expertise in RET design and implementation for hotel buildings. Experiences and recommendations related to the use of RETs in hotels, as well as insights into current implementations and encountered challenges, are being gathered to provide valuable insights.

Within the scope of expert focus group discussions, the use of various RETs in hotel building construction and their role in incorporating these technologies are analyzed by all relevant stakeholders. Following the expert interviews and literature review, a comprehensive analysis of the technologies is conducted to identify the criteria that are significant in evaluating RETs for hotel buildings. According to the experts, the primary criterion influencing the decision to adopt RETs in hotel projects is cost. The installation and equipment costs of RETs are considered initial investment costs, and it is noted that high initial investment costs can make it difficult to persuade investors. However, in hotel buildings, where the investor and user are typically the same individual, it is highlighted that minimizing operational costs could motivate investors, as opposed to residential projects developed on a build-and-sell basis where the investor and user are different. For hotel investors, these technology investments are sometimes preferred despite high initial costs because they can eventually turn into a revenue source.

According to the experts, photovoltaic panels and solar thermal panels are associated with high initial investment costs due to the expenses of solar panels, inverters, and installation. In contrast, technologies with moderate initial investment costs include heat pumps, biomass boilers, micro-hydropower, and small-scale wind turbines. Installation costs for solar thermal panels vary depending on the system’s complexity and size. Heat pumps generally have lower installation and equipment costs compared to solar systems. Biomass boiler costs vary based on the boiler type and biomass source, while installation costs for micro-hydropower depend on site conditions and system size. The costs for small-scale wind turbines are influenced by turbine size and local wind conditions. Additionally, one of the motivating factors for investors is the decreasing payback periods for technologies, particularly in recent times for photovoltaic (PV) technologies. Heat pumps and biomass boilers generally moderate payback periods, typically around 5 to 10 years, depending on system/boiler efficiency and energy/biomass costs. Micro-hydropower period varies widely (5 to 15 years) based on site conditions and installation costs. Small-scale wind turbines offer a long payback period, generally between 7 and 12 years, dependent on wind conditions and turbine efficiency. The payback period indicates how long it takes for the technology to recoup its costs. On the other hand, the long lifespan of renewable energy systems makes them advantageous for hotel buildings, which are long-lasting structures. The system lifespan indicates the operational duration of the technology, which typically ranges from 25 to 30 years for many technologies. Experts have highlighted that some photovoltaic panel projects implemented 25 years ago are still operating with minimal efficiency loss and limited maintenance/repair. Maintenance and repair costs are also a crucial criterion in the selection of RETs. Operational and maintenance costs include the regular maintenance and operational costs of the technology. For hotels, minimizing maintenance costs and ensuring that the system is as easy to manage as possible are crucial for investors, especially considering the high personnel costs associated with hotel operations. For example, if maintenance of a technology can be performed by one person instead of seven or eight, it significantly reduces personnel costs, which are one of the largest expenses in hotels. In this regard, ease of maintenance and requirements are also important evaluation criteria. The regular maintenance requirements of the technology are related to the number of personnel needed and its manageability. Many technology systems can be made intelligent with automation, which affects their ease of maintenance and manageability. For example, the performance of each installed panel can be monitored and controlled remotely. In the event of a malfunction, alerts are sent to a computer or phone screen. The ‘smartness’ of the technology is thus a crucial factor. The maintenance requirements of the technologies, the regular maintenance and repair needs of the technology, the ease of performing this maintenance, the number of personnel required for maintenance work, access to technical support and spare parts, and whether the technology is user-friendly are all critical aspects. Having a small number of personnel required to manage the technology (operation and maintenance of the energy system) and its ease of management is highly advantageous for investors and operators. In the hotel sector, the ability to create the right operational program based on these criteria provides a competitive edge. In this context, the selected technology’s ability to provide sufficient and reliable power is also influential. Renewable energy technology can reduce the dependence and stress on the grid for the hotel’s energy needs. However, if the entire energy requirement is to be met by the renewable energy system, choosing a system that provides sufficient and reliable power is advantageous for ensuring the continuous and uninterrupted supply of energy. Reliable systems are critical for the continuity of hotel operations. The energy production capacity and efficiency of renewable energy technology systems vary. In this context, the energy production efficiency suitable for the region’s climatic conditions should be analyzed.

In the context of climate change and environmental issues, experts have also evaluated the environmental impacts of technologies. Architects, in particular, are sensitive to the environmental effects of these technologies and consider potential risks to the surrounding ecosystem due to the installation and operation of energy systems. Many RETs involve the use of natural resources. In this regard, the consumption impact of the technology on natural resources is crucial. Reduced use of natural resources supports environmental sustainability. Photovoltaic panels and solar thermal panels use sunlight with minimal additional resource consumption during operation. Solar-powered absorption chillers use solar energy with minimal additional resource requirements. Heat pumps use ambient air, ground, or water as heat sources, with electricity required for operation. Biomass boilers require a continuous supply of biomass (wood, agricultural residues), impacting local resources. Micro-hydropower depends on consistent water flow, which can impact local water resources and ecosystems. Small-scale wind turbines use wind energy with negligible ongoing resource consumption. Integrated systems (photovoltaic + heat pump) combine the low resource use of PV panels with the moderate resource use of heat pumps.

From the perspective of environmental sustainability, having a low carbon footprint is also highly important. In terms of the technology’s impact on carbon emissions, it has been noted that solar panels and wind turbines have an almost zero carbon footprint during energy production. However, heat pumps may have indirect emissions if the electricity used is sourced from fossil fuels. Many implementations minimize carbon footprints by sourcing electricity from renewable energy resources. Biomass boilers can have a carbon footprint due to the production and transportation processes of biomass, but they are considered more environmentally friendly compared to fossil fuels. The noise level of some technologies can create problems for hotels. The potential harm of noise from the energy system’s operation to both the environment and hotel guests should be evaluated. A low noise level contributes to a comfortable environment for hotel guests. During interviews, architects also discussed the aesthetic impacts of integrating systems such as rooftop-mounted wind and solar energy technologies into buildings. Some technology systems can be concealed; however, the aesthetic integration of technologies that cannot be hidden should be considered during the design phase.

Experts have also highlighted the importance of policies and regulations. Local legal frameworks and mandates can significantly influence the preference for RETs. In the countries where the experts operate, there are instances where the use of certain renewable energy sources compatible with local climatic conditions is legally mandated. Examples include the mandatory use of solar energy for water heating and electricity generation in some Mediterranean countries and the compulsory implementation of biomass in rural areas. Policies and regulations are crucial for the widespread adoption of RETs. However, since they do not equally affect the decision-making process among different technology options, they are not included in the decision-making criteria table.

Based on expert interviews and the literature review, the criteria for evaluating RETs in hotel buildings have been identified (

Table 3. Criteria for evaluating renewable energy technologies in hotel buildings.

	Criteria	Description
Economic Criteria	Initial Investment Cost (C1) [15,25,36,37]	This criterion includes the initial setup and equipment costs of the technology [15,25,36].
	Operating and Maintenance/Repair Cost (C2) [25,36,37]	These are the regular maintenance and operational costs of the technologies [15,36]. This includes operating expenses such as the electricity costs required to run the equipment for a year [25].
	Payback Period (C3) [15,36]	This criterion refers to the time it takes for the investment in renewable energy technology to pay for itself through savings and returns [15,36].
Technological Criteria	Energy Production Capacity (C4) [25,36]	Capacity to meet the energy demands of hotel buildings and the ability to provide sufficient power [25,36].
	Maintenance Ease and Simple Management (C5)	Regular maintenance requirements of the technology, user-friendliness, ease of management, and access to technical support and spare parts.
	Reliability (C6) [15]	The technology’s capability to provide a continuous power supply to ensure uninterrupted hotel operations [15].
Environmental Impact Criteria	Noise Level (C7) [25]	The potential noise generated by the energy systems and its effects [25].
	Natural Resource Utilization (C8) [15]	The technology’s impact on the consumption of natural resources [15].
	Carbon Footprint (C9) [15]	The effect of the technology on carbon emissions [15].

). These criteria are as follows.

The evaluation of these criteria is crucial for determining which renewable energy technologies are most suitable for hotel buildings. In discussions with experts, renewable energy technologies are examined within the framework of these criteria. The experts have focused on solar, wind, geothermal, biomass, hydrogen, and hydroelectric sources.

During group discussions with the experts, technology producers have highlighted that heat pumps are widely used in hotel buildings across many countries. They have emphasized that the system operates more efficiently in thermal regions where underground hot water or heat sources are close to the surface, resulting in high temperatures. In areas with thermal water at 30 degrees Celsius, ground heating can be applied. Thermal waste heat or the residual heat from thermal pools can be utilized for heating purposes. The system is found to be efficient for heating in thermal facilities or preparing hot water. In Germany, where they extensively apply heat pumps, the general approach is to use them for low-temperature heating and high-temperature cooling. Additionally, ground heat recovery through basic piping systems is noted as an efficient technology. In isolated areas such as mountain hotels, biological treatment can be implemented. For coastal hotels, the importance of flowing water for water-source heat pumps is emphasized. Negative aspects of the technology include the growth of mussel larvae and algae within the system, which can lead to clogging. These issues can be addressed using ultraviolet light or by drilling a well and filtering sand. When evaluating the suitability of technologies for hotels, experts consider environmental factors such as the hotel’s location, size (capacity), energy demand, and climatic conditions. For example, if biomass is to be used for heating and hot water, the hotel’s location, distance to raw material sources, and the region’s biomass potential should be assessed. If there are no nearby raw materials, biomass storage and transportation can be costly. In regions with geothermal resources, heat pumps can be used to enhance energy efficiency. Micro hydroelectric systems for hotels also require proximity to water sources. Small-scale wind turbines are more effective in areas with high wind potential. The developing algae–bacteria consortium technology examined in the literature is excluded from consideration as its use in hotels is not yet widespread. The renewable energy technology alternatives for hotel buildings are listed in

Table 4. The renewable energy technology alternatives for hotel buildings.

Renewable Energy Technologies	Description
Photovoltaic Panels	Solar panels that convert solar energy into electrical energy.
Solar Thermal Panels	Systems that use solar energy to provide efficiency in water heating systems.
Solar-Powered Absorption Chiller	Systems that use solar energy for cooling.
Heat Pumps	Heat pumps that meet the heating and cooling needs of hotel buildings with low energy consumption.
Micro-Hydropower	Small-scale hydroelectric systems that convert the kinetic energy of water into electrical energy.
Small-Scale Wind Turbines	Small-scale wind turbines that generate electricity by converting kinetic energy into electrical energy.
Biomass Boilers	Boilers that produce heat by burning biomass.
Integrated Systems (Photovoltaic + Heat Pump) [37]	Systems that integrate photovoltaic panels and heat pumps.

.

In the next step, the MCDM methods suitable for technology selection based on the criteria and alternatives identified in the expert group interviews are described.

2.3. Renewable Energy Technology Selection: AHP and VIKOR Methods

AHP and VIKOR allow for the use of both quantitative and qualitative decision criteria in evaluating and selecting alternatives. The hotel building production process is a complex, multi-stakeholder process involving numerous criteria and a mix of qualitative and quantitative data. For this reason, the application of AHP and VIKOR methods is chosen. These methods employ different approaches and processes. AHP organizes the decision problem within a hierarchical structure and uses pairwise comparisons between criteria and alternatives. Decision-makers evaluate the relative importance of each criterion or alternative on a scale from 1 to 9. The relative priorities (weights) of the criteria and alternatives are then calculated based on these comparisons, which are used to determine the best alternative. AHP also checks the consistency of the decision-makers’ comparison matrices and places significant emphasis on the relative importance of criteria, evaluating alternatives according to these importance levels.

The VIKOR method, on the other hand, focuses on finding the best compromise solution under multiple conflicting criteria. It helps decision-makers find the most acceptable solution rather than the absolute best solution. VIKOR identifies the ideal (best) and anti-ideal (worst) solutions and calculates the distance of alternatives from these solutions. It uses a Q index to rank alternatives, considering their proximity to the ideal solution and distance from the anti-ideal solution. VIKOR is particularly used to achieve consensus among decision-makers. This method aims to provide an acceptable solution despite differing opinions and preferences among decision-makers. It seeks to find a balanced solution among conflicting criteria. While AHP is used to determine the relative weights of each criterion based on stakeholder judgments, VIKOR is employed to find a compromise solution using relevant performance metrics. The application steps for the AHP and VIKOR methods used in the study are described sequentially below. MS Excel 2016 is used for the calculations in the application.

2.3.1. AHP

The Analytic Hierarchy Process (AHP), developed by Thomas L. Saaty in the 1970s, is one of the multi-criteria decision-making methods. AHP is used as a decision-making tool in situations involving multiple criteria and decision-makers, where choices must be made among numerous alternatives under conditions of certainty or uncertainty. In such cases, AHP provides a comprehensive framework to incorporate both rational and irrational preferences, as well as intuitions, into the decision-making process [40]. The Analytical Hierarchy Process (AHP) can be defined as a method for representing complex, unstructured situations in a hierarchical framework, assigning quantitative values to personal judgments regarding the relative importance of each alternative, and synthesizing these judgments to determine the priority levels of the variables based on the results obtained [41]. Based on the criteria and technologies identified through expert group interviews, an AHP model is established, and a hierarchical structure is created. The weight of each criterion is determined based on the information obtained from the experts. The identified RETs are evaluated under each criterion. The steps of the AHP model are provided in

Table 5. Steps of the AHP method.

Steps	Substeps	Description
1. Problem Definition and Hierarchy Structure	Problem Definition and Goal	Identification of the decision-making problem and specification of the main objective.
	Criteria Identification	Determination of the criteria required to achieve the goal.
	Alternatives Identification	Listing of alternatives that will be evaluated under each criterion.
	Hierarchy Visualization	Creation of a hierarchical structure with the goal at the top, followed by criteria, sub-criteria, and alternatives.
2. Pairwise Comparisons and Matrix Construction	Criteria Pairwise Comparison	Evaluation of criteria in pairs to assess their relative importance.
	Saaty’s Scale Application	Use of a scale from 1 to 9 (1: equal importance, 9: extreme importance) to conduct comparisons.
	Comparison Matrix Construction	Development of a pairwise comparison matrix based on these evaluations.
3. Calculation of Weights Using Comparison Matrix	Column Summation	Summation of the values in each column of the comparison matrix.
	Matrix Normalization	Division of each element by the sum of its column to create a normalized matrix.
	Weights Calculation	Computation of the average of each row in the normalized matrix to determine the weights of the criteria.
4. Consistency Ratio Calculation	Consistency Verification	Ensuring that comparisons are consistent by calculating the Consistency Ratio (CR).
	Threshold Compliance	Checking that the CR is below a specified threshold (0.10).
	Comparison Revision	Reviewing and adjusting pairwise comparisons if the CR exceeds the threshold.
5. Pairwise Comparison of Alternatives	Alternatives Evaluation	Identification of the decision-making problem and specification of the main objective.
	Comparison Matrices Development	Determination of the criteria required to achieve the goal.
	Normalization and Weights Calculation	Listing of alternatives that will be evaluated under each criterion.
6. Calculation of Final Scores	Alternatives Weighting	Multiplication of the weights of the alternatives by the criteria weights.
	Score Aggregation	Summation of these products to compute the overall score for each alternative.
	Alternatives Ranking	Ranking of the alternatives based on their final scores.
7. Decision-Making	Best Alternative Selection	Selection of the alternative with the highest score as the optimal solution.

.

The primary goal of the decision-making process is to determine the most suitable renewable energy technology for hotel buildings. The decision problem is structured into a hierarchical model with three levels:

1—Goal: Selection of the most suitable renewable energy technology for hotel buildings.

2—Criteria: The criteria against which the options will be evaluated (e.g., initial investment cost, operational cost, carbon footprint, etc.). Economic, environmental, and technical criteria include the following:

C1: Initial Investment Cost;

C2: Operating and Maintenance/Repair Cost;

C3: Payback Period;

C4: Energy Production Capacity;

C5: Maintenance Ease and Simple Management;

C6: Reliability;

C7: Noise Level;

C8: Natural Resource Utilization;

C9: Carbon Footprint.

3—Alternatives: The different options or solutions to be compared (e.g., solar PV, wind turbines, biomass, etc.). The renewable energy technologies considered are as follows:

A1: Photovoltaic Panels;

A2: Solar Thermal Panels;

A3: Solar-Powered Absorption Chillers;

A4: Heat Pumps;

A5: Micro-Hydropower;

A6: Small-Scale Wind Turbines;

A7: Biomass Boilers;

A8: Integrated Systems (Photovoltaic + Heat Pump).

The hierarchical model for selecting the most suitable renewable energy technology for hotel buildings is illustrated in Figure 1.

Once the hierarchical structure is established, pairwise comparison matrices for the determined criteria are developed. Ten pairwise comparison matrices are obtained, consisting of the comparison of main criteria and the comparison of technologies according to these criteria. Decision-makers are asked to compare these criteria pairwise. While making pairwise comparisons, the decision-makers used Saaty’s 1–9 importance scale, as proposed by Saaty [42]. This scale is provided in

Table 6. Saaty scale.

Relative Importance	Definition	Explanation
1	Equal importance	Two activities contribute equally to objective
3	Weak importance	Experience and judgment slightly favor one activity over another
5	Strong importance	Experience and judgment strongly favor one activity over another
7	Demonstrated importance	One activity is strongly favored and demonstrated in practice
9	Extreme importance	The evidence favoring one activity over another is of the highest possible order of affirmation
2, 4, 6, 8	İntermediate values	When compromise is needed between two adjacent judgments

.

Each element of the pairwise comparison matrix for the criteria represents the relative importance of one criterion over another. The pairwise comparison matrix for the main criteria is presented in

Table 7. The pairwise comparison matrix for the main criteria.

	C1	C2	C3	C4	C5	C6	C7	C8	C9
C1	1	5	3	3	5	5	5	5	5
C2	0.2	1	0.33	0.2	1	0.33	1	0.33	1
C3	0.33	3	1	0.33	1	1	1	3	3
C4	0.33	5	3	1	3	3	3	3	3
C5	0.2	1	1	0.33	1	1	3	3	3
C6	0.2	3	1	0.33	1	1	3	5	3
C7	0.2	1	1	0.33	0.33	0.33	1	3	3
C8	0.2	3	0.33	0.33	0.33	0.2	0.33	1	1
C9	0.2	1	0.33	0.33	0.33	0.33	0.33	1	1
Total	2.860	23.000	10.990	6.180	12.990	12.190	17.660	24.330	23.000
CR = 0.08

.

The pairwise comparison matrix is normalized by dividing each element by the sum of its column, as shown in

Table 8. The normalized weights of the pairwise comparison matrix for the main criteria.

	C1	C2	C3	C4	C5	C6	C7	C8	C9
C1	0.350	0.217	0.273	0.485	0.385	0.410	0.283	0.206	0.217
C2	0.070	0.043	0.030	0.032	0.077	0.027	0.057	0.014	0.043
C3	0.115	0.130	0.091	0.053	0.077	0.082	0.057	0.123	0.130
C4	0.115	0.217	0.273	0.162	0.231	0.246	0.170	0.123	0.130
C5	0.070	0.043	0.091	0.053	0.077	0.082	0.170	0.123	0.130
C6	0.070	0.130	0.091	0.053	0.077	0.082	0.170	0.206	0.130
C7	0.070	0.043	0.091	0.053	0.025	0.027	0.057	0.123	0.130
C8	0.070	0.130	0.030	0.053	0.025	0.016	0.019	0.041	0.043
C9	0.070	0.043	0.030	0.053	0.025	0.027	0.019	0.041	0.043

.

Then, the average of each row is computed to obtain the priority vector, representing the relative weights of the criteria in Figure 2.

Using the AHP method, the relative importance weights of criteria for decision-making in renewable energy technologies are as follows: initial investment cost (0.314), energy production capacity (0.185), reliability (0.112), payback period (0.096), maintenance ease and simple management (0.093), noise level (0.069), natural resource utilization (0.048), operating and maintenance/repair cost (0.044), and carbon footprint (0.039).

All pairwise comparison matrices are checked for consistency. The Consistency Ratio of all matrices is less than 0.10. To ensure consistency in the pairwise comparisons, the Consistency Index ($CI$ and the Consistency Ratio ($CR$) are calculated using the following formulas [43]:

$$CI={\displaystyle \frac{{\lambda }_{\max }-n}{n-1}}$$

(1)

$$CR={\displaystyle \frac{CI}{RI}}$$

(2)

To calculate the Consistency Ratio ($CR$), the random index ($RI$) values corresponding to the number of decision alternatives are provided in

Table 9. Random index ($RI$) values.

n	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15
RI	0.00	0.00	0.58	0.90	1.12	1.24	1.32	1.41	1.45	1.49	1.51	1.48	1.56	1.57	1.59

[43].

If the Consistency Ratio ($CR$) is below 0.10, the consistency level of the pairwise comparison matrix is considered acceptable, indicating that the relative importance of each element is meaningful. However, if the $CR$ exceeds 0.10, it suggests inconsistency in the decision-makers’ judgments. In such cases, the comparisons need to be reviewed and refined to improve the consistency of the judgments [44].

Technology alternatives are compared according to the criteria. For each criterion, the alternatives are evaluated through pairwise comparisons to determine their relative weights, as shown in Figure 3. All these pairwise comparison tables are provided in Appendix A.

The overall priority of each alternative is calculated by combining the local priority vectors and the criteria weights. This is performed by multiplying the local priority vectors of the alternatives by the weights of the respective criteria and summing up the results for each alternative. This process yields the best alternative according to the decision-makers’ judgments.

The alternatives are ranked based on their overall priority as follows: photovoltaic panels, heat pumps, solar thermal panels, micro-hydropower, integrated systems, small-scale wind turbines, biomass boilers, and solar-powered absorption chillers (

Table 10. Final scores.

	C1	C2	C3	C4	C5	C6	C7	C8	C9	Final Score	Rank
A1	0.021	0.012	0.015	0.055	0.024	0.021	0.016	0.009	0.007	0.179	1
A2	0.021	0.012	0.032	0.029	0.024	0.021	0.016	0.009	0.007	0.171	3
A3	0.010	0.002	0.006	0.014	0.008	0.008	0.016	0.009	0.007	0.080	8
A4	0.106	0.005	0.015	0.006	0.008	0.021	0.007	0.003	0.002	0.175	2
A5	0.051	0.005	0.003	0.013	0.008	0.021	0.003	0.003	0.007	0.115	4
A6	0.049	0.002	0.003	0.007	0.008	0.008	0.002	0.009	0.007	0.094	6
A7	0.046	0.002	0.015	0.006	0.003	0.004	0.003	0.002	0.001	0.082	7
A8	0.010	0.004	0.006	0.055	0.008	0.008	0.007	0.003	0.002	0.105	5

).

By following these steps, the study systematically evaluates various renewable energy technologies and identifies the most suitable option for hotel buildings based on a comprehensive set of criteria. Among the main criteria, the most influential factor in deciding on technologies is the initial investment cost. The alternative with the highest overall priority is identified as the most preferred option. The most preferred technology for hotel buildings is photovoltaic panels.

Initially, the ranking of technology alternatives is determined by calculating the weights of the criteria using the AHP method. Following this stage, the VIKOR method, which is an important option to enhance the effectiveness of AHP, is applied as an alternative method. The VIKOR method is used to rank the alternatives based on the criteria weights obtained from AHP, and the rankings are compared.

2.3.2. VIKOR

The VIKOR method, named after the Serbian phrase “VIseKriterijumsa Optimizacija I Kompromisno Resenje” (Multi-Criteria Optimization and Compromise Solution), was first proposed by Opricovic and Tzeng for the optimization of multi-criteria problems [45]. VIKOR is highly effective in multi-criteria optimization and compromise solutions, providing a balanced and comprehensive assessment when used alongside AHP. The VIKOR method, proposed for the optimization of multi-criteria problems, aims to determine a compromise ranking and achieve a compromise solution under specified weights. By ranking alternatives under conflicting criteria, the method facilitates the selection of the most suitable options, addressing a multi-criteria ranking index based on proximity to the ideal solution. The VIKOR method provides the best solution by balancing different criteria, which is particularly useful in situations where criteria may conflict with each other. The VIKOR method aims to maximize the group benefit of the majority while minimizing the individual regret of the competitors. Its calculations are quite simple and straightforward [46]. The foundations of the compromise solution are established by Yu [47]. A compromise solution is the one closest to the ideal solution, and compromise involves reaching an agreement on a common acceptance [45]. The VIKOR method addresses the selection of one alternative or ranking of alternatives in the presence of conflicting criteria [48]. Assuming that each alternative is evaluated for each criterion, proximity values to the ideal alternative are compared to achieve a compromise ranking [49]. The basis for compromise ranking in multi-criteria measurement is the $L_p$ norm used as a summation function in compromise programming [47].

When $j$ alternatives are expressed as $A_1,A_2,\mathrm{\dots }{A}_J$, the evaluation result of alternative $A_j$ according to criterion $i$ is denoted as $f_{ij}$. The basis of the VIKOR method is the following form of the $L_p$ norm [47]:

$$L_{pj}={\left\{{\displaystyle \sum _{i=1}^n{\left[w_i\left(f_i^{\ast }-f_{ij}\right)/(f_i^{\ast }-f_i^{-}\right]}^p}\right\}}^{1/p}$$

(3)

$$1\le p\le \infty \mathrm{j}=1,2,\dots ,\mathrm{J}$$

$n$ denotes the number of criteria.

In the VIKOR method, $L_{ij}$ (from Equation (6), denoted as $S_j$) and $L_{\infty j}$ (from Equation (7), denoted as $R_j$) are used to create the ranking criteria. The maximum group benefit is represented by the result obtained from ${\min }_j{S}_j$, and the minimum individual regret is represented by the result obtained from ${\min }_j{R}_j$. The compromise solution $F^c$ is the most suitable solution closest to the ideal solution $F^{\ast }$. The term “compromise” refers to mutual acceptance, and as shown in Figure 4, it is expressed as $\mathrm{\Delta }{f}_1=f_1^{\ast }-f_1^c$ and $\mathrm{\Delta }{f}_2=f_2^{\ast }-f_2^c$ [45].

The steps of the VIKOR compromise ranking algorithm are shown in

Table 11. The steps of the VIKOR.

Steps	Definition
1. Decision Matrix Determination	Matrix Construction Determining Cost and Benefit Criteria Best and Worst Value Determination for Each Criterion Among the Alternatives Normalization of the Decision Matrix Weighting of the Matrix
2. Utility Measure and Regret Measure Calculation	$S_j$$\mathrm{and} R_j$ Calculation $\mathrm{Utility} \mathrm{Measure} (S_j$): It reflects the total distance of an alternative from the best value $\mathrm{Regret} \mathrm{Measure} (R_j$): It indicates the maximum distance of an alternative from the best value in any criterion
3. VIKOR Index ($Q_j$) Computation	Calculation of Qj Ranking of the Values
4. Alternative Ranking	Alternative Ranking $S_j$$, R_j$$, \mathrm{and} Q_j$ Values Ranking Rank the alternatives based on the Q values. The alternative with the smallest Q value is considered the best
5. Condition Satisfaction and Decision-Making	Ensuring Conditions for Selecting the Alternative with the Best Q (min) Value After Ranking Q Values from Smallest to Largest Condition 1: Acceptable benefit condition Condition 2: Acceptable decision reliability Decision-making

[45].

The performance of alternatives based on the criteria has been determined using Saaty’s 1–9 scale. The initial investment cost, operating and maintenance/repair cost, payback period, noise level, natural resource utilization, and carbon footprint are cost criteria, while energy production capacity, maintenance ease, and simple management and reliability are benefit criteria.

The best ($f_i^{\ast }$) and the worst $(f_i^{-}$) values for each criterion are determined [45].

$$f_i^{\ast }={\max }_j{f}_{ij} f_i^{-}={\min }_j{f}_{ij} \mathrm{benefit}\mathrm{criteria}$$

(4)

$$f_i^{\ast }={\min }_j{f}_{ij} f_i^{-}={\max }_j{f}_{ij} \mathrm{cost}\mathrm{criteria}$$

(5)

Based on the decision matrix provided in

Table 12. Decision matrix.

wi	0.314	0.044	0.096	0.185	0.093	0.112	0.069	0.048	0.039
	Min	Min	Min	Max	Max	Max	Min	Min	Min
	C1	C2	C3	C4	C5	C6	C7	C8	C9
A1	3	3	3	7	5	5	3	3	3
A2	5	3	1	5	5	5	1	3	1
A3	3	5	5	3	3	3	5	1	1
A4	3	3	5	5	3	5	3	3	3
A5	3	3	7	3	3	5	5	3	1
A6	3	5	7	1	3	3	7	1	1
A7	3	5	5	3	1	3	5	5	5
A8	7	3	5	7	3	3	3	3	3
fi* (best value)	3	3	1	7	5	5	1	1	1
fi- (worst value)	7	5	7	1	1	3	7	5	5

, the best and worst values for each performance measurement criterion are determined. After these values are established, the decision matrix is transformed into a normalized decision matrix. Using the normalized decision matrix, a weighted normalized matrix is obtained to reflect the criteria weights in the evaluation of technology alternatives. Using the weighted normalized matrix, the values for $S_j$ (maximum group benefit), $R_j$ (minimum regret), and $Q_j$ (final score of the alternatives) are determined for each alternative.

The values $S_j$ and $R_j$ are calculated for j = 1, 2, 3, …, J. The $S_j$ and $R_j$ values represent the average and worst group scores for the j. decision alternative. The weights wi represent the relative importance of the criteria. The measure of utility and regret can be calculated using the formula provided below [49]:

$$S_j={\displaystyle \sum _{i=1}^n{w}_i(f_i^{\ast }-f_{ij})/(}{f}_i^{\ast }-f_i^{-})$$

(6)

$$R_j={\max }_i\left[w_i(f_i^{\ast }-f_{ij})/(f_i^{\ast }-f_i^{-})\right]$$

(7)

The $Q_j$ values are calculated for all j = 1, 2, …, J. $Q_j$ can be calculated using the formula provided below [49]:

$$Q_j=v(S_j-S^{\ast })/(S^{-}-S^{\ast })+(1-v)(R_j-R^{\ast })/(R^{-}-R^{\ast })$$

(8)

$$S^{\ast }={\min }_j{S}_j, S^{-}={\max }_j{S}_j, R^{\ast }={\min }_j{R}_j, R^{-}={\max }_j{R}_j$$

The “v” value represents the weight of the majority of criteria (maximum group benefit). In other words, the “v” value expresses the weight of the strategy that provides the maximum group benefit, while (1 − v) represents the weight for the minimum regret of opposing opinions [49]. Consensus can be achieved with a “majority vote” (v > 0.5), “consensus” (v = 0.5), or “veto” (v < 0.5).

The $S_j$, $R_j$, and $Q_j$ values are ordered from smallest to largest to determine the ranking among the alternatives. As a result, three ranking lists are created. The results of the VIKOR ranking of the technology alternatives obtained from the analysis are shown in

Table 13. Sj, Rj, and Qj values ranking.

	Sj	Rj	Qj	Sj Ranking	Rj Ranking	Qj Ranking
A1	0.099	0.032	0.000	1	1	1
A2	0.243	0.157	0.286	3	4	3
A3	0.436	0.123	0.669	5	3	5
A4	0.239	0.064	0.278	2	2	2
A5	0.336	0.123	0.470	4	3	4
A6	0.553	0.185	0.900	6	5	6
A7	0.569	0.123	0.933	7	3	7
A8	0.603	0.314	1.000	8	6	8

. (Here, v has been set to 1).

When the following two conditions are satisfied, the alternative $(A^{(1)})$ ranked best according to the Q (minimum) values is proposed as the compromise solution.

Condition 1: Acceptable benefit condition

$$Q(A^{(2)})-Q(A^{(1)})\ge DQ$$

(9)

$(A^{(2)})$ represents the alternative ranked second in the given ordering, and J denotes the number of alternatives, $DQ=1/(J-1)$.

According to the data in

Table 14. Condition matrix.

	Qj (v = 0.00)	Qj (v = 0.25)	Qj (v = 0.50)	Qj (v = 0.75)	Qj (v = 1.00)
$Q(A^{(2)})$	0.113	0.155	0.196	0.237	0.278
$Q(A^{(1)}$)	0	0	0	0	0
$Q(A^{(2)})-Q(A^{(1)}$)	0.113	0.155	0.196	0.237	0.278
DQ = 1/(J − 1)	0.143	0.143	0.143	0.143	0.143
Condition 1	Not satisfied	Satisfied	Satisfied	Satisfied	Satisfied
Condition 2	Satisfied	Satisfied	Satisfied	Satisfied	Satisfied

, the technology alternatives meet the first condition, making them acceptable. In other words, these alternatives satisfy Equation (9) mentioned above.

Condition 2: Acceptable decision reliability

This condition must be satisfied to claim that the compromise solution is reliable in the obtained ranking. According to this condition, the alternative with the best Q value must also have at least one of the best $S$ or $R$ values. If both conditions are met, it is concluded that the obtained VIKOR ranking is reliable and usable.

Alternative $(A^{(1)})$ should be the best option in terms of the rankings for $S$ or $R$ values. In the study, among the technology alternatives, photovoltaic panels achieve the highest score in both $S$ and $R$ rankings, thus meeting the second condition (stability) and emerging as the best alternative.

The value of “v” in Equation (8) plays a crucial role in ranking the technology alternatives. By assigning different “v” values ranging from 0 to 1, the changes in the ranking of technology alternatives can be examined. The results of this analysis are presented in

Table 15. Different ranking results for various values of “v”.

	Qj Ranking	Qj (v = 0.00)	Qj Ranking	Qj (v = 0.25)	Qj Ranking	Qj (v = 0.50)	Qj Ranking	Qj (v = 0.75)	Qj Ranking	Qj (v = 1.00)
A1	1	0.000	1	0.000	1	0.000	1	0.000	1	0.000
A2	4	0.443	4	0.404	4	0.365	3	0.325	3	0.286
A3	3	0.324	5	0.410	5	0.496	5	0.582	5	0.669
A4	2	0.113	2	0.155	2	0.196	2	0.237	2	0.278
A5	3	0.324	3	0.361	3	0.397	4	0.434	4	0.470
A6	5	0.543	7	0.632	7	0.721	7	0.811	6	0.900
A7	3	0.324	6	0.476	6	0.629	6	0.781	7	0.933
A8	6	1.000	8	1.000	8	1.000	8	1.000	8	1.000

. As shown in Table 14, the condition is satisfied for all “v” values except 0.

3. Results and Discussion

The results obtained from the AHP and VIKOR methods are discussed in this section, focusing on the analysis of technology alternatives and criteria. According to the analyses conducted using the AHP and VIKOR methods, the most suitable technology for use in hotel buildings, as shown in

Table 16. Ranking of technologies using AHP and VIKOR methods.

Renewable Energy Technology Alternatives	VIKOR	AHP
Photovoltaic Panels	1	1
Solar Thermal Panels	3	3
Solar-Powered Absorption Chiller	5	8
Heat Pumps	2	2
Micro-Hydropower	4	4
Small-Scale Wind Turbines	6	6
Biomass Boilers	7	7
Integrated Systems (Photovoltaic + Heat Pump)	8	5

, is photovoltaic panels. Solar energy is the most popular energy source due to its high availability, accessibility, and various integration methods (such as PV panels, building-integrated PV systems, solar collectors, and floating PV panel systems) [23].

The evaluation of eight renewable energy technology alternatives for hotel buildings using both VIKOR and AHP methods provides a comprehensive perspective on their relative merits. Both methods consistently rank photovoltaic panels as the top choice, highlighting their effectiveness in energy production, low maintenance requirements, and minimal environmental impact. Heat pumps also rank highly, demonstrating their reliability and efficiency, with reasonable initial investment and operational costs. Solar thermal panels are ranked third in both methodologies, indicating their efficiency in sunny regions for hot water production and heating, coupled with low maintenance costs and moderate payback periods. Micro-hydropower systems hold a middle position, offering significant energy production capacity but with high dependency on site-specific conditions and varying environmental impacts. The rankings diverge for solar-powered absorption chillers, with VIKOR placing them higher than AHP. This suggests that while these systems may involve higher initial costs and complexity, they perform better when multiple criteria are considered, particularly in regions with high cooling demands. Small-scale wind turbines and biomass boilers are ranked lower, reflecting their higher maintenance needs and dependency on specific environmental conditions. Integrated systems, combining photovoltaic panels and heat pumps, are rated differently by the two methods, indicating their potential when both technologies’ benefits are considered, as well as their complexity and higher initial investment. Overall, the analysis underscores photovoltaic panels and heat pumps as the most suitable options for hotel applications, balancing performance across economic, technological, and environmental criteria. The consistently high rankings of these technologies affirm their viability in meeting the diverse energy needs of hotel buildings.

3.1. Analysis of Technologies Based on Criteria

Using the AHP method, the relative importance weights of criteria for decision-making in renewable energy technologies are as follows: initial investment cost (0.314), energy production capacity (0.185), reliability (0.112), payback period (0.096), maintenance ease and simple management (0.093), noise level (0.069), natural resource utilization (0.048), operating and maintenance/repair cost (0.044), and carbon footprint (0.039). The results obtained using the AHP method reveal the prioritization of various criteria in decision-making for renewable energy technologies.

The highest weight is assigned to the initial investment cost (0.314), indicating its significant impact on the decision-making process. This emphasizes the importance of upfront financial considerations, particularly for stakeholders who must justify the initial expenditure. The initial investment cost of renewable energy technologies is a critical factor for hotel buildings in developing countries with limited financial resources. High upfront costs pose significant challenges, such as difficulties in securing funding, accessing affordable credit, and prioritizing budgets toward essential needs. Additionally, the burden of long-term debt complicates the feasibility of these projects. Therefore, renewable energy solutions with lower initial costs and shorter payback periods become more attractive and viable options for hotel buildings in these regions. These options allow hotels to balance sustainability goals with economic constraints by providing quicker returns on investment and reducing financial risks. Following this, energy production capacity (0.185) is the second most critical criterion, underscoring the necessity for technologies to meet the energy demands of hotel buildings efficiently. Reliability (0.112) ranks third, highlighting the need for consistent and dependable energy supply systems, which are crucial for the continuous operation of hotel facilities. The payback period (0.096) also holds considerable weight, reflecting the economic sustainability perspective, where a quicker return on investment is desirable. Maintenance ease and simple management (0.093) show that operational simplicity and minimal maintenance requirements are important for seamless integration and ongoing operation. Other criteria, such as noise level (0.069), natural resource utilization (0.048), operating and maintenance/repair cost (0.044), and carbon footprint (0.039), while relatively lower in weight, still contribute to the overall decision-making framework. These factors collectively influence the selection of renewable energy technologies by balancing economic, operational, and environmental considerations.

The importance of reducing the carbon footprint in hotel buildings cannot be overstated, particularly in light of increasing EU regulations and associated sanctions aimed at curbing carbon emissions. Although carbon footprint reduction ranked lower in the selection criteria, it remains a crucial aspect of sustainability efforts. As the hospitality industry faces growing pressure to adopt environmentally friendly practices, reducing carbon emissions not only helps combat climate change but also aligns with regulatory compliance and enhances the hotel’s market reputation. Implementing renewable energy technologies that significantly lower carbon footprints can lead to long-term cost savings through reduced energy consumption and potential incentives for green practices. Therefore, prioritizing carbon footprint reduction is essential for hotel buildings to meet current and future regulatory requirements, avoid potential penalties, and contribute to global sustainability goals.

In conclusion, the AHP method effectively highlights the multifaceted nature of decision-making in renewable energy technology selection for hotel buildings, where initial investment cost, energy production capacity, and reliability play pivotal roles. This comprehensive approach ensures that the chosen technologies align with both financial constraints and sustainability goals, thereby supporting the broader objective of achieving energy-efficient and environmentally friendly hotel operations.

The divergence in results between the AHP and VIKOR methods, despite using the same criteria and alternatives, underscores the importance of evaluating different computational mechanisms in the decision-making process. AHP provides a ranking of each alternative based on weighted criteria, reflecting their relative importance. In contrast, VIKOR may prioritize alternatives that are closer to the ideal solution. AHP is sensitive to small changes in the pairwise comparison matrix, potentially producing varying rankings based on differences in expert judgments. VIKOR, on the other hand, focuses on the proximity of alternatives to the ideal solution, prioritizing relative performance. While AHP ranks alternatives according to overall priorities, VIKOR seeks to find the best compromise solution, which may not align with a simple prioritization.

3.1.1. Initial Investment Cost

Based on the findings of the study, expert group consultations, and the existing literature, the initial investment cost plays a crucial role in decision-making for selecting renewable energy technologies [15,25,34,36,37]. When the initial investment cost is high, convincing investors can be challenging, especially if the investor and user are not the same, such as in public housing. However, in hotel buildings, where the investor is usually also the user, minimizing operational costs can be a motivating factor. Furthermore, when these technologies are viewed as a revenue source, they may be preferred despite high initial investment costs in some cases.

Based on the initial investment costs, the ranking of the technologies is as follows: heat pumps, biomass boilers, small-scale wind turbines, micro-hydropower, solar thermal panels, photovoltaic panels, integrated systems, and solar-powered absorption chillers. When analyzing technologies based on their initial investment costs, solar-powered absorption chillers, and integrated systems are seen as high-cost options. Solar-powered absorption chiller systems require significant investment in both solar collectors and absorption chiller units. While chillers are expensive, cooling represents the highest cost in hotels, making their implementation necessary, especially in hot climates where cooling costs are high. Countries with low cooling demands may not prefer these systems, but they are favored in hot climates. Integrated systems, which combine photovoltaic panels and heat pumps, also have high overall costs; however, they are efficient systems. During the decision-making process, experts can persuade investors by explaining the various advantages of the technologies and the benefits they bring during the usage phase despite the initial investment cost. According to the experts, photovoltaic panels and solar thermal panels are associated with high initial investment costs due to the expenses of solar panels, inverters, and installation; however, they are the most preferred systems [25].

3.1.2. Operating and Maintenance/Repair Cost

According to experts, since room rates for hotels of certain standards are similar, high operational costs mean incurring losses. Therefore, reducing operating and maintenance/repair costs is of utmost importance. Based on the operating and maintenance/repair cost, the ranking of the technologies is as follows: solar thermal panels, photovoltaic panels, heat pumps, micro-hydropower, integrated systems, biomass boilers, small-scale wind turbines, and solar-powered absorption chillers.

Photovoltaic panels require minimal maintenance, mostly periodic cleaning and occasional checks for wiring issues, making them an attractive option for hotels looking to minimize operational disruptions and maintenance costs. Solar thermal panels, similar to photovoltaic panels, require periodic cleaning and system checks, indicating their suitability for regions with ample sunlight and low maintenance capabilities. Heat pumps require regular maintenance for optimal performance, including filter changes and system checks. This highlights the need for a dedicated maintenance team or service contract, which can be an additional cost but ensures the efficiency and longevity of the system. Micro-hydropower systems require regular maintenance, including cleaning of intake screens and periodic mechanical inspections. These systems are ideal for hotels located near water sources but necessitate a commitment to ongoing maintenance to prevent performance degradation. Small-scale wind turbines demand moderate to high maintenance, including regular inspections and upkeep of moving parts, such as bearings and blades. The reliance on mechanical components makes them more prone to wear and tear, necessitating frequent checks to ensure reliability. Integrated systems that combine photovoltaic panels and heat pumps necessitate the maintenance needs of both systems, resulting in slightly higher overall costs. However, the combined benefits of these technologies can offer substantial energy savings and environmental benefits, making the higher maintenance costs justifiable for many hotels. Solar-powered absorption chillers have higher maintenance needs due to the complexity of their solar and absorption components. This complexity can lead to higher operational costs and the need for specialized technicians, which may be a deterrent for some hotels. Biomass boilers need regular cleaning, ash removal, and inspection of moving parts. While these tasks can be labor-intensive, biomass boilers offer a sustainable energy source, especially in regions where biomass is readily available.

Despite the study results showing that maintenance and repair costs are not significant factors in decision-making, selecting the most appropriate renewable energy technology for hotels involves careful consideration of these maintenance and repair costs, ensuring both economic efficiency and operational sustainability. Hotels must weigh the long-term benefits of each technology against the immediate and ongoing maintenance requirements to make an informed decision that aligns with their operational goals and sustainability objectives [25,36,37].

3.1.3. Payback Period

The payback period is a crucial factor when investing in renewable energy technologies, as it determines how quickly the initial investment will be recovered through energy savings. For hotel buildings, where operational costs are a significant concern, selecting technologies with favorable payback periods is essential for financial viability [15,34,35,36].

Based on the payback period, the ranking of the technologies is as follows: solar thermal panels, photovoltaic panels, heat pumps, biomass boilers, solar-powered absorption chillers, integrated systems, micro-hydropower, and small-scale wind turbines. The payback periods for investments in renewable energy technologies vary depending on the type of building. For example, photovoltaic panels typically have a longer payback period in residential buildings compared to hotel buildings [35]. In buildings with high energy consumption, the payback period tends to be shorter due to greater energy savings [34]. According to the study results, while solar-powered absorption chillers are not the most preferred technologies based on payback period criteria, they are particularly favored in hot climates with high cooling loads, as indicated by expert group consultations. This preference underscores the importance of tailoring energy solutions to the specific needs of the building type and its location. When selecting renewable energy technologies for hotels, it is crucial to consider both the payback period and the unique energy demands of the building. Technologies such as solar-powered absorption chillers, despite their longer payback periods, offer significant advantages in specific contexts, such as in hot climates where cooling requirements are high. This highlights the need for a nuanced approach in decision-making, ensuring that the chosen technologies align with both economic considerations and operational needs. Solar thermal panels offer quick payback periods influenced by installation costs and energy savings. Photovoltaic panels offer quicker payback periods depending on installation costs and local energy prices [35]. According to experts, the payback period for heat pumps depends on system efficiency and energy costs. For biomass boilers, the payback period is influenced by boiler efficiency and biomass costs. Small-scale wind turbines tend to have longer payback periods but may be particularly beneficial in regions with favorable wind conditions. This analysis underscores the importance of matching technology choices with specific operational and climatic requirements to achieve optimal long-term benefits and operational efficiency.

3.1.4. Energy Production Capacity

Hotel investors may opt for renewable energy technologies to either fully meet their energy requirements or adhere to regulatory mandates, such as the obligation for certain buildings to implement renewable energy solutions in specific jurisdictions [34]. Achieving net-zero buildings necessitates the utilization of renewable energy sources and mitigating the mismatch between variable supply and demand [23]. Research indicates that renewable energy technologies can reduce net resource consumption for hotels to nearly negligible levels [13]. Consequently, the energy production capacity of the selected technology becomes a critical factor in decision-making [25,36].

Based on the energy production capacity, the hierarchical ranking of technologies is as follows: photovoltaic panels, integrated systems, solar thermal panels, solar-powered absorption chillers, micro-hydropower, small-scale wind turbines, heat pumps, and biomass boilers. The energy production capacities of renewable energy technologies for hotels vary widely, influencing their suitability for different applications. Photovoltaic and solar thermal panels stand out for their high energy production capacities, leveraging sunlight effectively to provide electricity and hot water, respectively. In the literature, there are hotel buildings that have achieved nearly full efficiency using photovoltaic panels. Solar-powered absorption chillers also offer a high level of energy production, though their performance is contingent upon solar energy availability for cooling purposes. Heat pumps and integrated systems exhibit moderate to high energy production capabilities, with heat pumps relying on temperature differentials and integrated systems combining the strengths of photovoltaic panels and heat pumps to provide comprehensive energy solutions. Biomass boilers and micro-hydropower systems offer moderate energy production, with biomass availability and water flow conditions playing critical roles. Small-scale wind turbines provide moderate energy production, dependent on local wind conditions. This assessment underscores the importance of aligning energy production capacities with specific hotel needs and environmental conditions to optimize energy use and sustainability.

3.1.5. Maintenance Ease and Simple Management

The largest expenditure in hotels is personnel costs [5]. The ease of maintenance for technologies and the ability to carry out maintenance with minimal staff are crucial for reducing personnel expenses in hotels [34].

Based on the maintenance ease and simple management, the ranking of the technologies is as follows: photovoltaic panels, solar thermal panels, integrated systems, solar thermal panels, solar-powered absorption chillers, micro-hydropower, small-scale wind turbines, heat pumps, and biomass boilers.

The ease of maintenance and manageability of renewable energy technologies significantly impacts their feasibility for hotel applications. Photovoltaic and solar thermal panels emerge as the easiest to maintain. They require minimal intervention beyond occasional cleaning and inspection to ensure optimal performance. Cleaning solar panels is crucial for maintaining their efficiency but can significantly impact water resources and environmental sustainability. Implementing more sustainable cleaning practices and exploring innovative technologies can help mitigate these effects and support the broader environmental benefits of solar energy. Solar-powered absorption chillers and heat pumps fall into the moderate maintenance category. These systems demand regular upkeep, such as filter changes and system checks, to maintain efficiency. Solar-powered absorption chillers, in particular, require moderate maintenance due to the complexity of maintaining both solar and chiller components. Micro-hydropower and small-scale wind turbines also require moderate maintenance, with tasks including cleaning intake screens, mechanical inspections, and upkeep of moving parts. Integrated systems, which combine photovoltaic panels and heat pumps, exhibit a moderate ease of maintenance, reflecting the combined requirements of both technologies. Biomass boilers, however, present the greatest maintenance challenges. They require frequent attention for cleaning, ash removal, and mechanical inspections, making them the least favorable in terms of maintenance ease among the evaluated technologies.

3.1.6. Reliability

High energy-consuming hotel buildings’ capacity to meet their energy needs from renewable energy technologies is crucial for ensuring the continuity of hotel operations [15]. The ability of these technologies to provide sufficient and reliable energy is a critical factor in decision-making processes, according to study results, the literature, and expert opinions [15,25,36]. When hotels cannot fully meet their energy requirements, they need to rely on the grid or other sources for support [3]. Furthermore, the efficient utilization of energy by these technologies for the system is also highly important [25].

Based on reliability, the ranking of the technologies is as follows: photovoltaic panels, solar thermal panels, heat pumps, micro-hydropower, solar-powered absorption chillers, small-scale wind turbines, integrated systems, and biomass boilers. The most reliable renewable energy technologies for hotel buildings are heat pumps, photovoltaic panels, solar thermal panels, and micro-hydropower systems. Solar-powered absorption chillers, small-scale wind turbines, and integrated systems offer moderate to high reliability, while biomass boilers are deemed moderately reliable. This ranking provides a comprehensive understanding of which technologies offer the most dependable performance, aiding in the selection of suitable renewable energy solutions for hotel applications.

3.1.7. Noise Level [25]

The noise criterion is important in the evaluation of technologies. Both the environment and hotel guests should not be disturbed. Based on the noise level, the technologies are ranked as follows: photovoltaic panels and solar thermal panels are rated highest, followed by solar-powered absorption chillers and heat pumps, integrated systems, micro-hydropower, biomass boilers, and small-scale wind turbines.

The evaluation of noise levels associated with various renewable energy technologies for hotel buildings reveals distinct characteristics that can guide selection based on environmental comfort. Photovoltaic panels, solar thermal panels, and solar-powered absorption chillers demonstrate the lowest noise levels, operating quietly with minimal disturbance due to their passive or silent mechanisms. Heat pumps and integrated systems, combining PV panels with heat pumps, exhibit a moderate noise level, primarily from compressors and fans. Biomass boilers and micro-hydropower systems are categorized with a moderate noise level, attributable to their combustion and turbine operations. Conversely, small-scale wind turbines rank highest in noise levels due to the mechanical noise from rotating blades and components. This ranking underscores the importance of noise considerations in choosing renewable energy technologies for hotel applications, ensuring an environment conducive to both environmental sustainability and guest comfort.

3.1.8. Natural Resource Utilization

The natural resource usage of renewable energy technologies for hotels varies significantly, reflecting their operational demands and resource dependencies [15]. Photovoltaic and solar thermal panels, along with solar-powered absorption chillers, demonstrate low natural resource usage as they predominantly harness sunlight, requiring minimal additional resources during operation. Small-scale wind turbines are noted for their low resource consumption, utilizing wind energy with minimal ongoing impact. Heat pumps and integrated systems, while still relatively resource-efficient, exhibit moderate resource usage due to their reliance on ambient air, ground, or water sources and the need for electricity. Biomass boilers and micro-hydropower systems, however, have higher resource demands; biomass boilers require a continuous supply of biomass, impacting local resources, while micro-hydropower depends on consistent water flow, which can affect local water resources and ecosystems. This comparison highlights the necessity of considering both resource efficiency and the potential environmental impact of each technology to ensure sustainable and responsible energy solutions for hotel operations.

3.1.9. Carbon Footprint

A low carbon footprint is important in terms of environmental sustainability [15]. When assessing the impact of technology on carbon emissions, solar panels and wind turbines exhibit a zero carbon footprint during energy generation. Heat pumps do not directly emit carbon as they operate on electricity; however, if the electricity originates from fossil fuels, indirect emissions may occur. However, if the electricity comes from fossil fuels, there can be indirect emissions. Opting for electricity sourced from renewable energy minimizes the carbon footprint. Micro-hydropower systems do not produce carbon emissions during energy production. There may be low emissions during construction and maintenance processes, but the overall carbon footprint is very low. Biomass boilers have a relatively higher carbon footprint due to the production and transportation processes of biomass. However, they are more environmentally friendly compared to fossil fuels. The choice of technologies used in energy production can have a direct impact on carbon emissions, and these choices are crucial for environmental sustainability.

3.2. Renewable Energy Technologies

This section discusses the findings related to alternative renewable energy technologies evaluated for use in hotel buildings within the scope of the study.

3.2.1. Photovoltaic Panels

Photovoltaic panels demonstrate strong performance in power generation, with numerous examples showcasing their ability to provide up to 100% of energy needs [3,23]. Their reliability is generally high, though it is contingent on weather conditions. The initial investment cost is moderate, and they remain efficient even after long durations, such as 30 years [34,35]. Maintenance and repair costs for photovoltaic panels are low, contributing to their economic attractiveness. Environmentally, they have a minimal impact due to their low natural resource usage and carbon footprint. The operational complexity is low, requiring minimal personnel for maintenance and offering straightforward manageability. Photovoltaic panels are a cost-effective and sustainable choice for energy generation in various applications, including hotel settings.

3.2.2. Solar Thermal Panels

Solar thermal panels exhibit high power generation capacity, making them an effective solution for harnessing solar energy to provide significant heating and hot water. While their reliability is moderate and dependent on weather conditions, their overall performance remains strong. The initial investment required for solar thermal panels is low, and the payback period is reasonable, making them a cost-effective option over time. The longevity of these systems further enhances their value, as they offer a long operational life with low maintenance and repair costs. Environmentally, solar thermal panels have a minimal impact, with low carbon emissions and efficient use of natural resources. They require minimal personnel for operation and are straightforward to manage. Solar thermal panels offer a practical, efficient, and sustainable option for renewable energy in hotel applications.

3.2.3. Solar-Powered Absorption Chiller

Solar-powered absorption chillers are highly appropriate for locations with significant cooling requirements and hot climates, providing both economic and environmental benefits. Their power generation capacity is efficient, and they are reliable under varying weather conditions. Despite the high initial investment, the payback period is reasonable, making them a cost-effective solution over time for hot climates. The initial investment required for solar-powered absorption chillers is high, but they offer a reasonable payback period, balancing the cost over their extended system life. The systems are durable, providing long-term service with moderate maintenance and repair costs. Environmentally, they have a low impact, contributing minimally to carbon emissions. Operationally, they require minimal personnel and offer moderate manageability.

3.2.4. Heat Pumps

Heat pumps provide a reliable and efficient solution for heating and cooling in hotel buildings. They offer moderate power generation capacity and high reliability, making them suitable for various operational conditions. The initial investment is moderate, with a payback period that is also reasonable, reflecting a balance between cost and performance. Heat pumps have a long system life, low maintenance and repair costs, and minimal environmental impact. They require only a small number of personnel for operation and are straightforward to manage. Heat pumps are an excellent choice for hotels seeking an effective, economical, and environmentally friendly heating and cooling solution.

3.2.5. Micro-Hydropower

Micro-hydropower systems are highly effective for power generation in hotel settings, providing significant and reliable energy output. Despite the high initial investment and long payback period, their long system life and low maintenance costs contribute to their overall efficiency. The environmental impact is moderate, but the benefits in terms of sustainability and reliability often outweigh these concerns. Micro-hydropower systems require minimal personnel and are relatively easy to manage, making them a viable option for hotels with access to suitable water resources.

3.2.6. Small-Scale Wind Turbines

Small-scale wind turbines offer moderate power generation capabilities for hotel buildings, with their effectiveness dependent on local wind conditions. The initial investment and payback period are both moderate, but the long system life makes them an attractive option. With low environmental impact and minimal personnel requirements, small-scale wind turbines are relatively easy to manage, making them suitable for hotels in regions with consistent wind resources. Their performance and efficiency are closely linked to the availability and consistency of wind, which should be a key consideration in their deployment.

3.2.7. Biomass Boilers

Biomass boilers provide high power generation capacity and reliability, making them a robust choice for energy needs in hotel buildings. Their complexity and the need for regular fuel supply and management should be carefully considered when integrating them into hotel energy systems. Despite challenges such as potential odor emissions, these can be effectively managed through proper fuel selection and combustion techniques. Moreover, biomass boilers contribute to sustainability by utilizing waste materials for energy generation, thereby supporting environmentally responsible waste disposal practices.

3.2.8. Integrated Systems (Photovoltaic Panels + Heat Pumps)

Integrated systems combining photovoltaic panels and heat pumps offer a high energy production capacity and reliability, effectively addressing the energy needs of hotel buildings. Despite the high initial investment and extended payback period, these systems are advantageous due to their long operational life and minimal environmental impact.

4. Conclusions

This study provides a comprehensive evaluation framework for guiding renewable energy decisions in the hotel sector, addressing the urgent need for sustainable energy solutions in hotel buildings. Additionally, it explores the feasibility, existing challenges, and opportunities related to these technologies. The integrated AHP and VIKOR approach aims to facilitate decision-making processes regarding the adoption of RETs in hotel buildings. It offers a reliable and comprehensive methodology for RET selection, allowing for more informed and balanced decisions by considering all relevant factors. Given the diverse perspectives and priorities of stakeholders in RET selection, the VIKOR method’s capacity to provide a consensus-based solution is particularly valuable. Proposing a decision-making method to decision-makers contributes to the adoption and widespread use of RETs in the hotel sector, supports the development of environmentally friendly technologies, and promotes the preference for clean energy sources, thereby simplifying the selection of RETs. It provides decision-makers with valuable insights into the economic, technological, and environmental impacts of systems. Additionally, it informs renewable energy technology producers about the strengths and weaknesses of their systems, enabling improvements based on decision-maker preferences. Furthermore, it offers guidance to hotel maintenance personnel on potential technical and economic issues. This study addresses a gap in the literature by offering detailed analysis and comparison of RET specifically for hotel buildings, emphasizing the benefits of integrating RETs into hotel operations for sustainable development. There are very few studies using decision-making methods for selecting RETs in hotel buildings, and no other studies have combined AHP and VIKOR methods. For future research, the developed framework can be effectively applied to similar decision-making challenges in other sectors. Alternatively, it can be adapted to national conditions by incorporating various renewable energy technology alternatives and criteria and by employing different MCDM methods to further refine the decision-making processes.