1. Introduction
Cooling has become an essential necessity, particularly in regions known for hot climates, such as tropical and equatorial countries. Elevated temperatures and humidity levels can significantly influence daily life in these regions. Global warming is also affecting regions worldwide, with a resultant increase in the mean temperatures all over the planet [
1]. Also, population growth and rising living standards are driving an additional need for cooling and air conditioning systems, which are becoming increasingly common [
2], particularly compression cooling systems, due to their notable efficiency and comparatively affordable cost. However, these systems consume a significant portion of worldwide electricity, primarily generated by burning fossil fuels [
3]. Therefore, compression-based cooling systems have harmful environmental effects, contributing to increasing global carbon emissions. The International Institute of Refrigeration (IIR) estimated that the electrical energy consumed by refrigeration systems represents approximately 20% of the global electrical power consumption [
4]. Specifically, air-conditioning units consume about 8.5% of the world’s total electricity, emitting one gigaton of carbon dioxide into the atmosphere [
5].
Therefore, there is a need for sustainable and renewable cooling systems, particularly those powered by renewable and clean energy resources. The Gulf Cooperation Council (GCC) countries have abundant access to solar energy. For instance, the United Arab Emirates (UAE) has an average annual solar radiation of 2285 kWh/m
2, with a daily sunshine duration of 10 h, while Kuwait has an average yearly solar radiation of 2150 kW/m
2, with an average daily sunshine duration ranging from 7 to 12 h, and the yearly average solar radiation for Saudi Arabia has a value of 2200 kWh/m
2 [
6]. This availability makes solar energy a viable and environmentally friendly renewable source in these regions. Hence, the ideal solution for the cooling demand problem in these regions is the implementation of systems that can not only fulfill the necessary cooling capacity, but also generate electrical energy. Solar-powered multigenerational systems, rather than conventional ones, have emerged as one of the most effective methodologies to address this issue.
As a part of the proposed system, adsorption cooling systems powered by renewable sources offer the benefit of using natural refrigerants for cooling purposes, which have no negative effects on global warming and may be driven by low-temperature solar energy sources [
1,
7]. Additionally, they have a lifespan of around 25 years, can operate at temperatures above 50 °C, require less maintenance as they do not have moving parts, and do not experience crystallization or corrosion issues [
8]. However, these systems have comparatively low coefficients of performance (COP). Adsorption chillers driven by renewable energy have recently received much interest for their use in heating and cooling generation [
9]. Moreover, using clean and renewable energy sources, such as solar, to power these systems reflects the long-term answer to this issue [
10,
11,
12]. Due to their capacity to simultaneously produce electricity and deliver solar thermal energy, photovoltaic-thermal (PVT) collectors have been gaining popularity in different research areas [
13,
14]. In the PVT collectors, high electrical efficiency can be attained compared to the conventional PV modules due to the temperature reduction of the PV modules in the PVT collectors. Therefore, PVT collectors show higher overall solar energy conversion.
Many researchers have studied different configurations of multi-generation and hybrid solar-powered adsorption-based systems [
1,
15]. For instance, Mohammadi et al. [
16] reviewed the different configurations of solar-powered multigeneration systems, including adsorption chillers. Hassan et al. [
17] theoretically evaluated the performance of five distinct multi-generation system configurations. Additionally, a techno-economic evaluation of a solar-powered adsorption cooling system was carried out [
18]. A multigeneration system was investigated by Calise et al. [
19] utilizing a PVT collector, an adsorption cooling system, and a solar-assisted heat pump. The PVT collector’s efficiency was 49%, the adsorption chiller’s COP was 0.55, and the heat pump’s COP was 4, according to the findings. In El-Sharkawy et al. [
20], the potential use of solar-driven adsorption chillers using the Middle East’s climate conditions was theoretically studied. A two-bed system using silica gel and water was driven by a compound parabolic solar collector. The performance of this proposed setup was explored theoretically. Furthermore, in Papoutsis et al. [
21], a theoretical analysis was performed on three unique solar-driven cooling systems. The first system employs a standard electric chiller powered by different PV panels. The second system utilizes a solar-driven adsorption cooling mechanism. Meanwhile, the third system is a hybrid model that combines adsorption and electric chillers, powered by PVT collectors. Mostafa et al. [
22] formulated a mathematical representation for a solar-powered adsorption cooling system tailored for cold storage applications. A monthly evaluation of the system’s performance metrics was conducted together with an economic analysis. The research showed the system’s proficiency in hot and dry weather conditions. It was observed that both the performance factor and the initial energy ratio excelled in such climates. In hot and arid conditions, the cooling cost averaged USD 0.203/kWh, while in humid regions, it stood at USD 0.485/kWh.
Based on the previously mentioned viewpoints, many past studies have concentrated on utilizing either solar thermal collectors or thermal photovoltaic collectors to power adsorption chillers. However, the system that we introduce here presents a new setup that leverages the optimal combination of PVT and evacuated tube collectors (ETCs), both to drive an adsorption chiller and generate electricity. This amalgamation was determined by investigating five configurations of PVT/ETC arrangements conducted in one of our previous studies [
17]. This system’s performance when operated under the weather conditions of the GCC countries was theoretically investigated. Three cities in the GCC countries were selected for this study: Sharjah in the UAE, Riyadh in Saudi Arabia, and Kuwait City in Kuwait. This research was undertaken during the summer months, specifically June, July, and August, of these cities. The cooling was generated through a single-stage, dual-bed adsorption cooling system powered by solar thermal energy and employing a silica gel/water pair. The dynamic performance of the proposed system was analyzed using a prepared MATLAB code. To generate electricity throughout the year and harness solar thermal energy, commercially certified ETCs and PVT collectors were used.
2. Description of the Proposed System
Figure 1 displays the layout of the system proposed in this study. The system comprises (i) ETCs, (ii) PVT collectors, and (iii) a single-stage, dual-bed adsorption cooling unit that employs a silica gel/water pair. The PVT module generates electricity for both the building and system pumps, while the ETCs are used to drive the adsorption cooling system. The technical specifications for the ETCs and PVT collectors were obtained from the Apricus company in the USA and FOTOTHERM in Italy, respectively [
23,
24].
Table 1 summarizes the technical details of these collectors.
The adsorption cooling unit is driven by thermal energy generated by the PVT/ETC solar collector arrangement. A hot water storage tank is implemented between the solar collector arrangement and adsorption chillers to reduce the negative impacts of solar energy fluctuations (see
Figure 1). It should be highlighted that water flows through the PVT collectors, and the ETCs are in a parallel scheme. The water exits from both the PVT and the solar collectors and is then directed to the storage tank.
The adsorption cooling unit’s operation comprises four main modes, which can be summarized as follows:
Mode (A): In this mode, bed (1) is connected to the evaporator through valve V(1), and disconnected from the condenser by closing valve V(3). The water vapor, the refrigerant, flows from the evaporator to the adsorber heat exchanger (bed (1)) and is adsorbed by the silica gel (silica gel). The heat of adsorption is rejected by the cooling water that flows through bed (1). In this process, the cooling load is generated inside the evaporator due to the evaporation of water vapor. Simultaneously, bed (2) is connected to the condenser through valve V(4) and disconnected from the evaporator by closing valve V(2). Hot water flows through bed (2), where the refrigerant is regenerated and flows to the condenser where condensation occurs. The condensed refrigerant runs to the evaporator through a throttling valve.
Mode (B): In this mode, both beds are disconnected from the evaporator and the condenser. Hot water flows to bed (1), where its pressure increases from the pressure of the evaporator to that of the condenser, in a process named the pre-heating process. Simultaneously, cooling water flows through bed (2), where its pressure drops from the condenser pressure to the evaporator pressure, in a process named the pre-cooling process.
Mode (C): This mode can be considered as the reverse of mode (A), wherein bed (1) is linked to the condenser while being separated from the evaporator. Bed (2) is connected to the evaporator and disconnected from the condenser.
Mode (D): This mode is the opposite of mode (B).