Use of Triboelectric Nanogenerators in Advanced Hybrid Renewable Energy Systems for High Efficiency in Sustainable Energy Production: A Review

Abstract

Renewable energy is the best choice for clean and sustainable energy development. A single renewable energy system reveals an intermittent disadvantage during the energy production process due to the effects of weather, season, day/night, and working environment. A generally hybrid renewable energy system (HRES) is an energy production scheme that is built based on a combination of two or more single renewable energy sources (such as solar energy, wind power, hydropower, thermal energy, and ocean energy) to produce electrical energy for energy consumption, energy storage, or a power transmission line. HRESs feature the outstanding characteristics of enhancing energy conversion efficiency and reducing fluctuations during the energy production process. Triboelectric nanogenerator (TENG) technology transduces wasted mechanical energies into electrical energy. The TENG can harvest renewable energy sources (such as wind, water flow, and ocean energy) into electricity with a sustainable working ability that can be integrated into an HRES for high power efficiency in sustainable renewable energy production. This article reviews the recent techniques and methods using HRESs and triboelectric nanogenerators (TENGs) in advanced hybrid renewable energy systems for improvements in the efficiency of harvesting energy, sustainable energy production, and practical applications. The paper mentions the benefits, challenges, and specific solutions related to the development and utilization of HRESs. The results show that the TENG is a highly potential power source for harvesting energy, renewable energy integration, application, and sustainable energy development. The results are a useful reference source for developing HRES models for practical applications and robust development in the near future.

1. Introduction

Energy is an indispensable element of our social development, from cooking to industrial consumption. Traditional energy is increasingly exhausted because fossil energy resources are limited, and their exploitation causes harmful effects to our environment. Renewable energy (RE) has a crucial mission in facing the problems of a lack of energy and protecting the natural environment all over the world [1,2,3,4,5,6,7]. Renewable energy contributes to technology, solutions, and national policies leading toward the sustainability of energy utilization, economic–social development, environmental protection, and industrialization strategies [8,9,10,11,12,13,14,15,16,17,18,19,20]. Traditional renewable energy resources include solar energy, hydropower, ocean energy, wind power, bioenergy, geothermal energy, and hydrogen energy, as shown in Figure 1. Renewable energy (RE) is the best solution for exploiting, developing, and consuming energy to repel carbon dioxide (CO₂) emissions to the index of zero carbon for sustainable development [21,22,23,24,25]. The global carbon dioxide emission shows a worrying number with the high data of 37 × 109 tonnes (t) recorded in 2022. With the rapid development of renewable energy, the Net-Zero Roadmap (NZR) was planned by the International Energy Agency (IEA) with the strategy of maintaining the global warming temperature of 1.5 °C until 2030 and attaining net-zero carbon dioxide emissions by 2050. With the net-zero emissions (NZEs) scenario, emissions will be reduced by about 80% by 2030 with the speeding up of renewable energy development, energy efficiency, methane emission reductions, and energy conversion technologies. Carbon dioxide emissions will decrease by about 35% by 2030 in comparison to the value in 2022 in the NZEs scenario, with the appearance of clean energy and renewable energy. The share of the global implementation of clean energy technologies from China and other advanced economies was recorded during the period of 2010 to 2022, with a contribution of over 95% from global electric vehicles and heat pumps, as well as about 85% from the contribution of wind and solar energy capacity from 2015 to 2022 [26].

Table 1. Renewable energy generation (TWh) in the world and some critical areas.

		2010	2021	2022	2030 with the NZEs Scenario	2050 with the NZEs Scenario
In the world	RG (TWh)	4209	7964	8599	19,295	55,057
	Comparison with 2010	-	89.21%	104.3%	358.42%	1208.08%
North America	RG (TWh)	856	1374	1497	3538	9261
	Comparison with 2010	-	60.51%	74.88%	313.32%	981.89%
Central and South America	RG (TWh)	752	896	1018	1428	3768
	Comparison with 2010	-	19.15%	35.37%	89.89%	401.06%
Europe	RG (TWh)	954	1601	1620	3438	6834
	Comparison with 2010	-	67.82%	69.81%	260.38%	616.35%
Africa	RG (TWh)	116	201	210	711	3453
	Comparison with 2010	-	73.28%	81.03%	512.93%	2876.72%
Eurasia	RG (TWh)	226	287	277	380	844
	Comparison with 2010	-	26.99%	22.56%	68.14%	273.45%
Asia Pacific	RG (TWh)	1287	3568	3932	9568	28,321
	Comparison with 2010	-	177.23%	205.52%	643.43%	2100.54%
China	RG (TWh)	782	2448	2681	6419	14836
	Comparison with 2010	-	213.04%	242.84%	720.84%	1797.19%
European Union	RG (TWh)	653	1081	1085	2407	4720
	Comparison with 2010	-	65.54%	66.16%	268.61%	622.82%
United States	RG (TWh)	441	867	973	2087	7683
	Comparison with 2010	-	96.60%	120.63%	373.24%	1642.18%
Brazil	RG (TWh)	437	508	594	732	1378
	Comparison with 2010	-	16.25%	35.93%	67.51%	215.33%

shows the rapid increase in renewable generation (RG) around the world, with 4209 terawatt hours (TWh) in 2010, 7964 TWh in 2021, and 8599 TWh in 2022, as well as estimations of 19295 TWh in 2030 and about 55057 TWh in 2050 with the NZEs scenario, respectively. The table shows increases in renewable generation of about 89.21%, 104.3%, 358.42%, and 1208.08% in comparison to the value of renewable energy generation in 2010, respectively. The table also shows renewable generation in critical areas of North America, Central and South America, Europe, Africa, Eurasia, and the Asia Pacific with outstanding aggregations. North America shows impressive numbers with 856 TWh in 2010, 1374 TWh in 2021, and 1497 TWh in 2022, as well as estimations of 3538 TWh in 2030 and about 9261 TWh in 2050 with the NZEs scenario, respectively. The increases in renewable generation in this area are statistical values of about 60.51%, 74.88%, 313.32%, and 981.89% in comparison with the value of renewable energy generation in 2010, respectively. Central and South America shows recorded values of about 752 TWh in 2010, 896 TWh in 2021, and 1018 TWh in 2022, as well as estimations of 1428 TWh in 2030 and about 3768 TWh in 2050 with the NZEs scenario, respectively. In the area, renewable generation increases are counted at about 19.15%, 35.37%, and 89.89% and then rapidly increased to 401.06% in comparison with the value of renewable energy generation in 2010, respectively. Europe has recorded positive values with 954 TWh in 2010, 1601 TWh in 2021, and 1620 TWh in 2022, as well as estimations of 3438 TWh in 2030 and about 6834 TWh in 2050 with the NZEs scenario, respectively. The RG increases in Europe were evaluated with numbers of about 67.82%, 69.81%, and 260.38%, and a remarkable number of 616.35% in comparison with the value of renewable energy generation in 2010, respectively. Africa has the effective development of renewable generation with 116 TWh in 2010, 201 TWh in 2021, and 210 TWh in 2022, as well as estimations of 711 TWh in 2030 and about 3453 TWh in 2050 with the NZEs scenario, respectively. The area receives growth values of about 73.28%, 81.03%, and 512.93%, and an intense increase of 2876.72% in comparison with the value of renewable energy generation in 2010, respectively. Eurasia shows good RG values with 226 TWh in 2010, 287 TWh in 2021, and 277 TWh in 2022, as well as estimations of about 380 TWh in 2030 and 844 TWh in 2050 with the NZEs scenario, respectively. The area achieved growth numbers of about 26.99%, 22.56%, 68.14%, and 273.45% in comparison with the value of renewable energy generation in 2010, respectively. The Asia Pacific contributes to the outstanding RG numbers with 1287 TWh in 2010, 3568 TWh in 2021, and 3932 TWh in 2022, as well as estimations of 9568 TWh in 2030 and about 28321 TWh in 2050 with the NZEs scenario, respectively. This area records excellent increases of about 177.23%, 205.52%, 643.43%, and 2100.54% in comparison with the value of renewable energy generation in 2010, respectively. The table also shows remarkable results of renewable energy generation from different countries and combines those which have positive strategies in the development of renewable energy generation such as China, the European Union, the United States, and Brazil [27].

Renewable energy utilization contributes to the protection of our living environment and fossil energy resources [28]. The Renewables 2024 Global Status Report (GSR 2024) was conducted by the Renewable Energy Policy Network for the 21st Century (REN21) with the impressive number of renewable power capacity of 473 gigawatts (GW) corresponding to the increase of 36% in power capacity added in 2023 and the contribution of 151 countries to the development strategy of net-zero targets [29]. The global energy demand increased by about 1.3% in 2022 according to the International Energy Agency (IEA). The Stated Policies Scenario (STEPS) also gives an overview of the latest policies regarding areas such as energy, industry, and climate for countries over the world. The STEPS suggests that the contribution of renewable energy to power capacity should be increased of about eighty per cent by 2030 in the effort of reducing carbon dioxide emissions [27].

The renewable energy (RE) has been received many attentions for excavation, development, and application such as planning environmental protection strategies using renewable energy [30], constructing pathways of deep decarbonization with the benefits of environment protection and economic control [31], developing energy legislation for countries to promote the replacement of traditional energy with renewable energy to help solve the problem of global warming and the lack of energy [32], investigating the evidence of a positive influence on economic growth with the use of renewable energy [33], and using renewable energy sources to achieve net-zero energy for buildings [34].

A triboelectric nanogenerator (TENG) is an emerging technology for transforming wasted mechanical energy into electricity for many practical applications [35]. The TENG shows many advantages of modern renewable energy technology with outstanding characteristics of green energy, lightweight, simple structure, and sustainable energy source [36]. TENG technology can convert wasted mechanical energies by, for example, transducing water wave energy, motions, oscillations, and vibrations [37,38,39,40,41,42,43], kinetic energy from the ocean [44,45,46,47], and biomechanical energy from bio-object movement [48], into electrical energy. TENG technology is a strong candidate for renewable and sustainable energy generation as it converts renewable energy sources into electricity such as wind energy, water wave energy, and ocean energy. The TENG has outstanding features, including that it produces no gas emissions, is eco-friendly, and is a form of clean energy [49,50,51]. The TENG meets the following criteria of sustainable development goal 7 (SDG-7): providing everyone access to energy services using modern, affordable, and reliable energy resources by 2030 (Target 7.1), increasing the share of global renewable energy (Target 7.2), doubling the energy efficiency improvement (Target 7.3), promoting access to clean energy via research actions, technology applications, and capital investment (Target 7a), and expanding sustainable energy access for developing countries via services, technology, and infrastructure development (Target 7b) [52].

A single renewable energy system (SRES) is generally represented as a renewable energy conversion technology that utilizes a single renewable energy source such as solar energy, hydropower, ocean energy, wind power, bioenergy, geothermal energy, or hydrogen energy. Intermittent energy generation is the biggest disadvantage of SRESs which rely on natural environment conditions such as weather, season, day/night, and working environment [53]. This directly influences the energy conversion performance of renewable energy systems such as their efficiency, power, and continuity features. A hybrid renewable energy system (HRES) is an energy production model that is built by a combination of two or more single renewable energy systems. HRESs convert renewable energy sources into electrical energy for electrical consumption devices, energy storage systems, and power transmission lines. HRESs are the best solution to the intermittent energy supply problem; because they consist of different single renewable energy systems, they can harvest many types of renewable energy sources at difference times [54]. HRESs show outstanding characteristics of high power efficiency and sustainable renewable energy production [55]. HRESs are one of the best methods to enhance output performance and reduce fluctuation during the energy generation process. HRESs are an effective supporting method for energy generation in remote communities with wonderful characteristics such as low energy cost and environmental protection. HRESs have been studied by many research groups who have applied techniques and methods such as artificial intelligence, hybrid algorithms, and computer tools to develop HRES models for practical applications [56,57,58,59].

Hybrid renewable energy systems can be integrated into a hybrid energy storage system to improve the benefits of a power system by, for example, decreasing the capital cost, enhancing the efficiency, extending the system life, or balancing the output power [60]. Figure 2 shows the structure of a hybrid energy system integrated with energy storage modules to improve the performance of a power system [61]. The model consists of basic components including nonrenewable energy resources, renewable energy resources, converters, energy storage modules, an energy management hub, alternative current (AC)–direct current (DC), AC–AC, DC–DC, and DC–AC converters, a bidirectional converter, AC–DC buses, AC–DC loads, and an electrical grid. The energy resources include nonrenewable and renewable energy types that supply the input power to the system. The energy storage module has the role of storing electrical energy for long-term use and balancing the input signal of electricity with the electrical equipment. The AC–DC, AC–AC, DC–DC, and DC–AC converters are used to change an alternative current (AC) to a direct current (DC), an AC to an AC, a DC to an AC, and a DC to an AC, respectively. The bidirectional converter is used to make an interface between a low-voltage storage unit and a high-voltage bus. The AC and DC buses are used to couple the power sources integrated into the hybrid energy system. The electrical load uses the AC or DC power to drive the actions of the electrical equipment. The power grid is used to transmit electricity to areas that lack electrical energy.

HRESs have contributed to a reduction in net present costs and carbon dioxide emissions [62,63]. HRESs have led to the development of technologies and methods to expand the practical applications of renewable energy; these include the development of algorithms to optimize the autonomous service of powering residential buildings [64], the introduction of thermochemical conversion technology to turn waste into electricity [65], the use of algorithm-based fuzzy logic tools to select a suitable location for HRES facilities [66], and the creation of charging stations for electric vehicles [67]. TENG technology is emerging as an effective solution which can be integrated into HRESs to boost the efficiency, power output, and integrity of the power system [68,69]. This paper reviews the recent techniques and methods of developing hybrid renewable energy systems to improve the energy conversion efficiency, output performance, and continuity of renewable energy conversion systems. The integration of a triboelectric nanogenerator (TENG) in an advanced hybrid renewable energy system (HRES) is proposed for harvesting renewable energy with the ability to improve efficiency and produce sustainable energy, among other practical applications. This paper addresses the benefits, challenges, and solutions for strengthening the efficiency, utilization, and development of HRESs. The results reveal that triboelectric nanogenerators have great potential as a harvesting technology for energy generation, renewable energy integration, application, and sustainable energy development, eliminating the disadvantages of intermittency and variability that single renewable energy systems have stumbled upon. The results hope to support the development of HRES models for practical applications and robust energy development in the near future.

2. Single Renewable Energy Systems

A single renewable energy system (SRES) is an energy conversion system that is used to convert a renewable energy resource into useful energy, such as photovoltaic systems converting solar energy into electricity, wind energy systems changing wind power into electricity, triboelectric nanogenerator systems turning wasted mechanical energy into electrical energy, and hydropower systems transforming hydropower into electricity. Single renewable energy systems are developed using mathematical models to address the output performance of the system.

2.1. Photovoltaic System

A photovoltaic system (PVS) is a solar energy system that converts solar energy into electricity. The total solar radiation is the input energy for PVSs. The total solar radiation can be estimated using Equation (1) [70]:

$${\mathrm{I}}_{\mathrm{T}}={\mathrm{I}}_{\mathrm{b}}{\mathrm{R}}_{\mathrm{b}}+{\mathrm{I}}_{\mathrm{d}}{\mathrm{R}}_{\mathrm{d}}+{(\mathrm{I}}_{\mathrm{b}}+{\mathrm{I}}_{\mathrm{d}}{)\mathrm{R}}_{\mathrm{r}}$$

(1)

where

${\mathrm{I}}_{\mathrm{T}}$ is the total solar radiation (kW h/m²);

${\mathrm{I}}_{\mathrm{b}}$ is the direct normal solar radiation;

${\mathrm{I}}_{\mathrm{d}}$ is the diffuse solar radiation;

${\mathrm{R}}_{\mathrm{d}}$ is the tilt factor of the diffuse of the solar radiation;

${\mathrm{R}}_{\mathrm{r}}$ is the tilt factor of the reflection of the solar radiation.

The power output of PVSs can be calculated using Equation (2):

$${\mathrm{P}}_{\mathrm{s}\mathrm{i}}={\mathrm{I}}_{\mathrm{T}\mathrm{i}}\mathrm{\eta }{\mathrm{A}}_{\mathrm{P}\mathrm{V}\mathrm{S}}$$

(2)

where

${\mathrm{P}}_{\mathrm{s}\mathrm{i}}$ is the power output of the PVS;

${\mathrm{A}}_{\mathrm{P}\mathrm{V}\mathrm{S}}$ is the area of the PVS (m²);

η is the system efficiency.

η can be calculated using Equation (3):

$$\mathrm{\eta }={\mathrm{\eta }}_{\mathrm{m}}{\mathrm{\eta }}_{\mathrm{p}\mathrm{c}}{\mathrm{P}}_{\mathrm{f}}$$

(3)

where

${\mathrm{\eta }}_{\mathrm{p}\mathrm{c}}$ is the power condition efficiency;

${\mathrm{P}}_{\mathrm{f}}$ is a packing factor;

${\mathrm{\eta }}_{\mathrm{m}}$ is module efficiency.

This value can be calculated by Equation (4):

$${\mathrm{\eta }}_{\mathrm{m}}={\mathrm{\eta }}_{\mathrm{r}}(1-\mathsf{\beta }\left({\mathrm{T}}_{\mathrm{c}}-{\mathrm{T}}_{\mathrm{r}}\right))$$

(4)

where

${\mathrm{\eta }}_{\mathrm{r}}$ is the module reference efficiency;

β is the temperature coefficient;

${\mathrm{T}}_{\mathrm{c}}$ is the monthly average temperature;

${\mathrm{T}}_{\mathrm{r}}$ is the reference temperature.

The monthly average temperature can be calculated using Equation (5):

$${\mathrm{T}}_{\mathrm{c}}={\mathrm{T}}_{\mathrm{a}}+{\displaystyle \frac{\mathsf{\alpha }\mathsf{\tau }}{{\mathrm{U}}_{\mathrm{L}}}}{\mathrm{I}}_{\mathrm{T}}$$

(5)

where

${\mathrm{T}}_{\mathrm{a}}$ is the instantaneous ambient temperature.

$${\displaystyle \frac{{\mathrm{U}}_{\mathrm{L}}}{\mathsf{\alpha }\mathsf{\tau }}}={\displaystyle \frac{{\mathrm{I}}_{\mathrm{T},\mathrm{N}\mathrm{T}}}{{(\mathrm{N}\mathrm{T}-\mathrm{T}}_{\mathrm{a},\mathrm{N}\mathrm{T}})}}$$

(6)

NT is the normal operation cell temperature. In normal conditions, ${\mathrm{T}}_{\mathrm{a},\mathrm{N}\mathrm{T}}$ is 20 degrees centigrade, ${\mathrm{I}}_{\mathrm{T},\mathrm{N}\mathrm{T}}$ is 800 watts (W), and the wind speed is 1 m per second (m/s).

2.2. The Wind Energy System (WES)

Wind energy systems produce electricity by using a wind turbine generator to change wind energy into electric energy with a power output P calculated by Equation (7) [71,72]:

$${\mathrm{P}}_{\mathrm{w}}={\displaystyle \frac{1}{2}}\mathsf{\rho }{\mathrm{A}}_{\mathrm{w}}{\mathrm{V}}^3$$

(7)

where

P_w is the power output of the WES;

A_w is the swept area of the wind turbine;

V is the velocity of the air.

2.3. Triboelectric Nanogenerator (TENG)

The triboelectric nanogenerator (TENG) has recently emerged as a new renewable and clean energy source. The TENG can convert wasted mechanical energy into electrical energy. The TENG’s working mechanism is based on the triboelectrification effect of coupled tribomaterials during contact-separate cycles [73]. TENGs have more outstanding characteristics, including being lightweight and low cost, using easy-to-find materials, having a simple structure [74], and generating sustainable power [75,76]. Due to these outstanding characteristics, TENGs have received much attention and have been used for numerous practical applications such as transforming blue energy into electricity [77,78,79,80], developing biomedical sensors, healthcare devices, therapeutic applications, and implantable biomedical applications [81,82,83,84,85], constructing micro-electro-mechanical systems (MEMSs) equipment [86], self-powered sensing in temperature sensors, healthcare sensors, pressure sensors, humidity sensors, force sensors, accelerating sensors, self-powered active sensors for hydrogen detection, multifunctional sensors, human–machine interface sensing, and self-powered sensing devices [87,88,89,90,91,92,93,94,95], harvesting biomechanical energy to sustainably power wearable bioelectronics systems and self-powered wearable electronics [96,97,98], monitoring the marine pipeline, the ocean wave, and the environmental potential of hydrogen [99,100], introducing cellulose materials to drive self-powered sensors [101], converting mechanical energy for self-powered electronics, smart devices, Internet of Things (IoT), and lighting LEDs [102,103,104], constructing electrocatalytic systems with a self-powered source [105], developing multifunctional self-powered electronics, sensors, portable electronics devices, functional devices, and biomedical devices [106,107,108,109], developing sustainable power [110,111], creating human–machine interface applications [112], combining with wood to create self-powered sensors [113], and developing a self-powered device for lighting purposes [114]. Many other methods have been researched to develop advanced triboelectric nanogenerators (ATENGs) such as introducing carbon material with low-dimensional features to improve output performance [115], developing chemical modification methods to enhance output performance [116], and constructing ATENGs using technologies from electrochemical systems [117].

Figure 3 shows the working mechanism of the TENG with five basic stages (initial, contacting, separating, released, and contacting again states) to produce electric energy. Figure 3a shows noncharges in the initial state. Figure 3b shows the adverse charges that were generated as the two triboelectric surfaces made contact with each other. Figure 3c shows the potential unbalance as the two tribomaterials are released from each other. An electric current moves via the external load. Figure 3d shows the neutral state as the two tribomaterials are released from each other. Figure 3e shows the potential unbalance as the two tribomaterials are pressed together again. An electrical current flows through the external load. The TENG produces an electric current with the open-circuit voltage (V_OC) expressed by Equation (8) [118]:

$${\mathrm{V}}_{\mathrm{O}\mathrm{C}}=-{\displaystyle \frac{\mathsf{\sigma }\mathrm{d}}{{\mathsf{\epsilon }}_0}}$$

(8)

where

${\mathrm{V}}_{\mathrm{O}\mathrm{C}}$ is the open-circuit voltage;

$\mathsf{\sigma }$ is the triboelectric charge density;

$\mathrm{d}$ is the distance between the two contact surfaces;

${\mathsf{\epsilon }}_0$ is the vacuum permittivity.

Figure 3. The working mechanism of the TENGs. (a) The initial state. (b) The contacting state. (c) The releasing state, in which a current (I) flows via an external load. (d) The released state. (e) The pressing state, in which a current (I) runs through an external load.

Figure 3. The working mechanism of the TENGs. (a) The initial state. (b) The contacting state. (c) The releasing state, in which a current (I) flows via an external load. (d) The released state. (e) The pressing state, in which a current (I) runs through an external load.

The TENG shows good serving ability in hybrid energy systems, improving the efficiency of the hybrid energy system with a TENG and a piezoelectric nanogenerator [119], providing a self-powering feature for a smart system based on hybrid energy using an ATENG and an electromagnetic generator [120] and a self-powering source for an Internet of Things (IoT) system using a hybrid energy system comprising a TENG and a pyroelectric nanogenerator [121], and integrating a TENG, solar cells, and an electromagnetic generator into an HRES to harvest the ocean’s energy for practical applications [122].

3. Hybrid Renewable Energy System (HRES)

A hybrid renewable energy system (HRES) is constructed from two or more types of single renewable energy systems. Advanced hybrid renewable energy systems support the production of energy, especially in remote areas, with many advantages such as their use of cheap and sustainable energy sources. HRESs can penetrate into the power grid or act alone to supply energy to a specific area. New methods and technologies have been focused on using HRESs to convert renewable energy sources into electricity such as investigating an HRES model to transduce hydropower and thermal energy into electricity in Ukraine [123] and developing an HRES based on triboelectric nanogenerators, thermoelectric nanogenerators, piezoelectric nanogenerators, electromagnetic nanogenerators, and solar cells to improve the efficiency of energy conversion [124]. Figure 4 shows the proposal of a hybrid renewable energy system with the contribution of a photovoltaic energy system, a wind energy system, and a triboelectric nanogenerator to produce electric energy for electrical lines, electric consumption equipment, and energy storage systems [125,126,127]. Figure 4a shows a solar photovoltaic energy system with photovoltaic energy conversion technology that is used to change solar energy into electricity. Figure 4b shows a wind power system that uses wind power technology to convert wind energy to electrical energy for energy consumption, storage, and integration. Figure 4c shows a triboelectric nanogenerator system that uses triboelectric generator technology to convert mechanical energy into electricity for the purposes of electricity integration, energy storage, and providing power to electric consumption equipment. Figure 4d shows an electrical line that has the duty of transmitting electric energy to distant areas. Figure 4e shows how energy from HRESs is used in electrical consumption devices. Figure 4f shows the energy storage system that is used to store energy for long-time use, transport energy to remote areas, and power portable devices. The model consists of three different kinds of energy transduction systems to improve renewable energy conversion efficiency. Specifically, solar photovoltaic energy systems produce electricity via the photovoltaic effect principle. Photovoltaic cells are generally semiconductor devices that convert solar energy into electricity [128,129]. Figure 5 shows an equivalent circuit representing a solar photovoltaic cell. I_ph is the current source of the photocurrent of the PV cell. The current source is linear dependency relation on the solar irradiance. I_d represents the reverse saturating current of the diode. R_sh is the PV intrinsic shunt resistance. R_s is the PV series resistance related to energy losses via the assembly technique of solder bonds, junctions, and wires. Single PV cells can be connected to form an array of PVs for more generation efficiency. The output current of the PV array can be expressed by Equation (9):

$$I=N_p{I}_{pn}-N_p{I}_d\left[exp\left({\displaystyle \frac{qV}{{kTAN}_s}}-1\right)\right]$$

(9)

where I is the output current of the PV array. $N_p$ represents the module numbers connected in parallel. $I_{pn}$ is the photocurrent. $I_d$ represents the reverse saturation current of the PV cell. $q$ represents the electron charge. $V$ represents the output voltage of the PV array. $k$, $T$, $A$, and $N_s$ are the Boltzmann constant, the temperature of the PV cell, the deviation of the pn junction feature of the PV cell, and the number of PV cells connected in series, respectively. The wind power system produces electricity from wind energy via wind turbines, as mentioned in Section 2.2. The triboelectric nanogenerator produces electricity from mechanical energy via triboelectric effect, as mentioned in Section 2.3. By using different energy sources of solar, wind, and mechanical energy, HRESs can produce electricity at all times for practical applications. This ensures a high efficiency of energy transduction in HRESs. In the case of a lack of input triggers of solar, wind, or mechanical energy, the energy storage unit will become an electrical generator to supply electricity to the consumption equipment.

The TENG can be assembled with other harvesting energy systems to form an HRES by, for example, integrating the TENG with the photovoltaic effect to form a hybrid energy harvester for sustainable power generation [130], developing a hybrid harvesting energy system-based TENG and a piezoelectric nanogenerator to improve the energy harvesting efficiency [131], or designing a hybrid energy system using a TENG and glucose biofuel energy to convert energy from multiple sources of biomechanical and biochemical energies into electricity [132]. TENGs can effectively harvest many wasted energies from our environment when it is used in hybrid energy systems such as harvesting vibration energy by a HES of TENG and an electromagnetic generator [133], collecting vibration energy by a HRES of TENGs and EMGs [134].

Many research groups have been developed the advanced hybrid renewable energy systems for different purposes such as producing energy by a HRES for remote areas and small communities [135], improving efficiency, and conductivity by introducing thermal energy storage techniques [136], promoting sustainable development by implementing optimization and control methods to improve the energy efficiency conversion [137], and improving the power quality for isolated areas using an optimization technique for hydropower and photovoltaic energy systems [138].

4. High Energy Conversion Efficiency, Renewable Energy Integration, Application, and Sustainable Energy Production

4.1. High Energy Conversion Efficiency (HECE)

Energy conversion efficiency (ECE) is the most important index of RESs [139,140,141]. Many solutions are applied to enhance the ECE of single renewable energy systems, such as applying new materials to improve the ECE of photovoltaic systems [142], building theoretical efficiency relationships to improve the ECE [143], investigating the effect of the structure of energy harvesting systems to improve the ECE of the output performance [144,145], and optimizing parameters to improve the ECE of the energy conversion [146,147]. However, single renewable energy systems have faced many problems that constrain the melioration of the energy conversion efficiency such as seasons, day/night time, rain time, economy, and the degree of input triggers [148,149]. The hybrid renewable energy system (HRES) is a good solution to these issues, with outstanding characteristics that improve the energy conversion efficiency of the system [150,151]. HRESs have high energy conversion efficiency performance as they avoid the limitations of single renewable energy systems by, for example, reducing the effects of temperature and solar radiation to improve the energy conversion efficiency of HRESs [152], enabling cost-effectiveness by optimizing the size of HRESs [153], and achieving high energy conversion efficiency in HRESs by incorporating an energy storage unit [154].

The high energy conversion efficiency (HECE) is really important throughout all steps of the process, including the ideas of HRESs, the designing procedure, the construction stage, the operating procedure, and during other estimations such as economic and environmental impacts [155,156]. The economy is a crucial factor for obtaining capital investment during the development of the HRESs. Net present value (NPV) has generally been used to assess capital investment into HRESs. NPV can be determined using Equation (10) [157]:

$$\stackrel{\wedge }{E}={\displaystyle \sum _t\left(R_t-Z_t\right)}{\left(1+d\right)}^{-t}$$

(10)

where

Rt is the outcome of the hybrid project;

Zt is the cost of the hybrid system in a year;

d is the discount rate.

The energy cost is crucial when evaluating the capital investment efficiency factor. A hybrid renewable energy system has the highest cost efficiency if it has the minimum energy cost. The energy cost can be estimated using Equation (11):

$$p={{\displaystyle \frac{{\displaystyle \sum _t{Z}_t(1+d)}}{{\displaystyle \sum _t{Q}_t{(1+d)}^{-t}}}}}^{-t}$$

(11)

where

Qt = Rt/pt;

Qt is the sale volume in one year;

pt is the energy price.

Many research groups have been focused on improving the efficiency of energy harvesting by applying technologies, techniques, and methods. Ensuring high efficiency and sustainable energy production in hybrid renewable energy systems has been the source of much concern for certain research groups, who have developed a THRES using a TENG and an EMG to achieve high energy conversion efficiency [158], developed a THRES using a TENG and photoelectric conversion to boost the efficiency of the energy conversion [159], constructed a THRES using a TENG and solar cells to achieve high energy conversion efficiency for sustainable agricultural development [160], composed THRESs using triboelectric nanogenerators and piezoelectric nanogenerators to enhance the power conversion efficiency for sensing applications [161], and improved power conversion efficiency by introducing a THRES composed of TENG and EMG technologies for a marine monitoring sensor [162].

The energy conversion efficiency (ECE) of a single renewable energy system is generally governed by Equation (12) [163]:

$${\eta }_{sl}={\displaystyle \frac{E_{OUT(total)}}{E_{IN(sl)}}}$$

(12)

where

η_sl is the energy conversion efficiency of a single renewable energy system;

E_in is the input energy of the SRES;

E_out is the output energy of the SRES.

The efficiency of the SRES is strongly dependent on the input trigger. For example, the efficiency of a solar photovoltaic system increases as the sun rises and decreases as the sun goes down. The energy conversion is intermittent as the night time comes. The energy conversion efficiency of a single renewable energy system can also be disadvantaged by dust accumulation [164]. To improve the energy conversion efficiency of renewable energy systems, many research groups have focused on developing new technologies, methods, materials, and conversion models, such as using Culn1-xGaxSe2 material to enhance the efficiency of a solar cell system [165], and integrating some renewable energy conversion technologies utilizing wind power, solar cells, and rainwater to enhance the energy conversion efficiency of an HRES [166]. However, single renewable energy systems still undergo prominent issues due to input trigger conditions such as weather conditions, day/night time, and sunny/raining conditions that negatively influence the efficiency of the system. Hybrid renewable energy is the best solution to the challenge of weather conditions as it absorbs all of the input triggers to achieve high energy conversion efficiency. High energy conversion efficiency refers to the ability of a system to convert as much input energy as possible into output energy. Almost all hybrid renewable energy systems have the feature of high energy conversion efficiency because HRESs consist of more than one single renewable energy system, so they can harvest more renewable energy resources in different weather conditions. To demonstrate this more clearly, a mathematical model is proposed to describe the total energy conversion efficiency of hybrid renewable energy systems:

$${\eta }_{HRES}={\displaystyle \frac{E_{OUT(total)}}{E_{IN(total)}}}$$

(13)

where

η_HRES is the energy conversion efficiency of a hybrid renewable energy system;

E_OUT(total) is the total output energy that is produced by the HRES;

E_IN(total) is the total input energy that will be processed by the HRES.

E_IN(total) can be expressed by Equation (14):

$$E_{IN(total)}={\displaystyle \sum _1^n{E}_i}$$

(14)

where

n is the number of single renewable energy systems that are assembled into the HRES;

E_i is the energy of the ith single renewable energy system.

The total input renewable energy (E_IN(total)) includes n single renewable energy sources that are available in the survey environment for the proposed Equation (14). The total input renewable energy can be expressed by Equation (15):

$$E_{IN(total)}=E_{1(IN)}+E_{2(IN)}+E_{3(IN)}+E_{others(IN)}$$

(15)

where it is estimated that

E_1(IN) is solar energy (J);

E_2(IN) is wind energy (J);

E_3(IN) is the wasted mechanical energy (J) that is used by the TENG to produce electricity;

E_others(IN) is other energy (J) gathered from E_others(IN)i energies when ith = 1 to n.

The total output energy can be expressed by Equation (16):

$$E_{OUT(total)}=E_{1(OUT)}+E_{2(OUT)}+E_{3(OUT)}+E_{others(OUT)}$$

(16)

where it is estimated that

E_1(OUT) is solar photovoltaics energy (J);

E_2(OUT) is wind energy (J);

E_3(OUT) is the wasted mechanical energy (J) that is used by the TENG to produce electricity;

E_others(OUT) is other output energy (J) that is produced by E_others(OUT)i energies when ith = 1 to n.

Therefore, Equation (10) can be expressed by Equation (17):

$${\eta }_{HRES}={\displaystyle \sum _1^n{\eta }_i}={\eta }_1+{\eta }_2+{\eta }_3+{\eta }_{others}$$

(17)

where

η_i is the energy conversion efficiency of the ith single renewable energy system;

η₁ is the energy conversion efficiency of the solar photovoltaic energy system;

η₂ is the energy conversion efficiency of the wind power system;

η₃ is the energy conversion efficiency of the triboelectric nanogenerators;

η_others is the energy conversion efficiency of the other single renewable energy systems.

This reveals that a single renewable energy system is used to convert a part of the total input renewable energy; the single energy conversion efficiency is smaller than that of the HRES. The equations prove that HRESs have high energy conversion efficiency (HECE).

4.2. Renewable Energy Integration (REI)

Renewable energy integration (REI) is a process of energy processing used to incorporate renewable energy into the power grid and other industrial applications [167]. REI is the best solution to reducing carbon dioxide emissions that are produced by the transformation of fossil sources into other energies [168]. REI has been developed for multigeneration purposes such as electricity, cooling, drying, and heating products [169,170,171]. REI shows good service ability in energy grids for smart sites [172]. Many research groups have been focused on developing technologies and methods to integrate hybrid renewable energy systems into the power grid, smart grid, and multigeneration systems by, for example, optimizing a sustainable HRES model (from wind, biomass, and solar energies) to integrate into the power grid to improve the sustainability indexes of economy and environment in a petroleum refinery plant [173], developing HRESs that integrate hydrogen energy to meet the objectives of economy, technology, environmental, and social development [174], integrating HRESs into the microgrid for applications in industrial manufacturing and residential consumption with the contribution of photovoltaic power [175], improving the energy sustainability of the power grid by integrating HRESs into the electrical grid with the contribution of hydrogen energy storage units [176], using a hybrid model of the genetic algorithm particle and swarm optimization algorithm (GA-PSO) to optimize the design and management of an HRES for energy cost reduction and energy loss avoidance [177], applying artificial intelligence (AI) to integrate hybrid renewable energy systems into the microgrid to enhance the performance of the power grid [178], penetrating the HRES into the microgrid system in a high electrical consumption area with the aim of having positive impacts on the economy, environment, and technology [179], analyzing strategies to improve REI for developing countries [148], developing compensation technologies to decrease the influence of transmission line compensation on REI in the power grid to improve stability, power balance, and voltage regulation of the system [180], building an REI system for a small area of a university campus to achieve sustainable development with collective self-consumption ability [181], and incorporating a neural network (NN) to manage the power of REI in a direct current microgrid for effective operation of the system [182].

4.3. Applications

The TENG is a clean and renewable energy harvester that converts wasted mechanical energy into electrical energy. TENGs can stand alone when generating electricity or integrate into a hybrid renewable energy system. The TENG-based HRES (THRES) shows many crucial applications. Figure 6 shows applications of TENG-based HRESs such as self-charging power systems, self-powered biomedical complexes, self-powered wearable electronics, self-powered monitoring systems, smart electronics, human healthcare monitoring, and self-powered sensors. Table 2 shows some successful hybrid renewable energy systems constructed to harvest energy that have real-life daily applications. Some successful applications include energy harvesting, self-charging power systems, self-powered biomedical systems, self-powered monitor systems, self-powered wearable electronics, smart electronics, and self-powered sensors.

Energy harvesting (EH) is the biggest duty of THRESs; they convert renewable energy sources into useful energy for many further applications. Researchers have developed a THRES by combining a TENG and a piezoelectric nanogenerator (PENG) to harvest energy from rotational and axial motion types [183], constructed a THRES using a TENG and a PENG to harvest energy for a walking sensor [184], fabricated a THRES using a TENG and an EMG to harvest biomechanical energy [185], developed a THRES using a TENG and an electromagnetic generator (EMG) to harvest biomechanical energy [186], developed a THRES to harvest biomechanical energy [187], and established a THRES using a TENG and an EMG to garner energy [188].

Self-charging power systems (SCPSs) are an outstanding structure in THRESs that integrate a TENG and other pyroelectric, photovoltaic, thermoelectric, and piezoelectric harvesters for many practical applications; these include sustainably driving electronic devices [189], building TENGs and THRESs for self-charging electronic devices [38], supplying sustainable power sources for essential applications of portable electronics and the Internet of Things (IoT) [190], developing THRES-based textiles to provide self-charging power for artificial intelligence applications [191], constructing green THRESs for self-powering portable electronic devices [192,193], composing a THRES using a TENG and an electromagnetic generator to support the high performance efficiency of a self-charging power system for Internet of Things (IoT) applications [194], and developing a THRES using a TENG and photovoltaic panels to set up an SCPS for charging and driving the electrolysis of seawater by converting hybrid energies from the ocean and solar power [195].

Self-powered biomedical systems (SPBSs) are an important application of THRESs that use renewable energy to monitor human healthcare and help treat diseases by powering the medical electronic devices; for example, researchers have built a THRES using a TENG and an electromagnetic generator (EMG) to monitor healthcare systems [196], constructed a THRES using a TENG and a nonlinear electromagnetic generator to harvest biomechanical energy to power portable healthcare monitor machines and portable electronics [197], developed THRESs using a TENG and a piezoelectric generator (PEG) for implantable biomedical applications [198], and composed a THRES by combining a TENG and a PEG for a flexible biosensor device [199,200].

Self-powered monitor systems (SPMSs) have many meaningful practical applications as they have the outstanding features of automation and sustainability; for example, researchers have developed a THRES using a TENG and a PENG for sport monitoring operations [201], constructed a THRES by combining a TENG-EMG and a solar cell to create a self-powered compact sensor network to monitor natural disasters [202], and controlled air quality using a THRES constructed using a TENG and an EMG [203].

Self-powered wearable electronics (SPWEs) are also effective applications of the THRESs which are mobile, lightweight, and sustainable; for example, researchers have developed a THRES using a TENG and an EMG to power sustainable wearable electronics [204], and structured a THRES by combining a TENG and solar cells for wearable electronics [205]. Smart electronics (SEs) also receive a lot of attention from research groups, who have developed a THRES using a TENG and an EMG to scavenge biomechanical energy for smartphones, smartwatches, and Bluetooth devices [206].

Self-powered sensors (SPSs) use TENGs and THRESs in sensing applications and they are lightweight, have tiny dimensions, and are simple structures. Researchers have developed a THRES using a PEG and a TENG for self-powered sensors [207], built THRESs for biosensors [208], used a THRES comprising a TENG and an EMG to drive a self-powered speed sensor [209], developed a THRES using a TENG and a piezoelectric nanogenerator (PENG) for a healthcare monitoring sensor [210], used a THRES comprising a TENG and a PENG for a self-powered sensing network [211], and composed a THRES by combining a TENG and a piezoelectric nanogenerator for a self-powered human behavior sensor [212].

Table 2. Some successful hybrid renewable energy systems and their applications.

THRES	Hybrid Type	Performance	Application	Ref.
TCO-HG	PENG–TENG	Driving 60 LEDs	Harvesting energy, charging, and lighting.	[183]
PTNG	TENG–PENG	70 µW	Harvesting energy, and walking sensor.	[184]
THRES	TENG–EMG	630 mA	Harvesting energy, charging, and wireless power transmission.	[188]
UHO-TEHG	TENG and EMG	1.02 W	Human healthcare monitoring and self-powering portable electronics.	[196]
EINR-HG	TENG and EMG	131.4 mW	Portable healthcare monitoring machines and portable electronics.	[197]
PEDOT	TENG and PENG	1.71 mW	Sport monitoring operations, healthcare applications, and smart home devices.	[201]
THRES	TENG–EMG	6 W	Harvesting biomechanical energy and sustainable development.	[186]
HMI-HBNG	TENG–EMG	185 W/m2	Harvesting biomechanical energy, self-powered systems, and smart electronics.	[206]
RSHG	TENG–EMG	48 V, 1 mA	Harvesting energy, lighting LEDs, and driving electric watch.	[158]
FHNG	TENG–PENG	-	Healthcare monitoring sensor and self-powered devices.	[210]
HTEPENG	TENG–PENG	3.7 W/m2	Self-powered sensing network and portable electronics.	[211]
PSC/TENG	TENG–Solar cells	2.62 Wm−2	Renewable power generation and agricultural application.	[160]

Table 2. Some successful hybrid renewable energy systems and their applications.

THRES	Hybrid Type	Performance	Application	Ref.
TCO-HG	PENG–TENG	Driving 60 LEDs	Harvesting energy, charging, and lighting.	[183]
PTNG	TENG–PENG	70 µW	Harvesting energy, and walking sensor.	[184]
THRES	TENG–EMG	630 mA	Harvesting energy, charging, and wireless power transmission.	[188]
UHO-TEHG	TENG and EMG	1.02 W	Human healthcare monitoring and self-powering portable electronics.	[196]
EINR-HG	TENG and EMG	131.4 mW	Portable healthcare monitoring machines and portable electronics.	[197]
PEDOT	TENG and PENG	1.71 mW	Sport monitoring operations, healthcare applications, and smart home devices.	[201]
THRES	TENG–EMG	6 W	Harvesting biomechanical energy and sustainable development.	[186]
HMI-HBNG	TENG–EMG	185 W/m2	Harvesting biomechanical energy, self-powered systems, and smart electronics.	[206]
RSHG	TENG–EMG	48 V, 1 mA	Harvesting energy, lighting LEDs, and driving electric watch.	[158]
FHNG	TENG–PENG	-	Healthcare monitoring sensor and self-powered devices.	[210]
HTEPENG	TENG–PENG	3.7 W/m2	Self-powered sensing network and portable electronics.	[211]
PSC/TENG	TENG–Solar cells	2.62 Wm−2	Renewable power generation and agricultural application.	[160]

4.4. Sustainable Energy Production (SEP)

Sustainable energy production (SEP) plays a large role in achieving net-zero goals and sustainable development in our society. Figure 7 shows a basic diagram of sustainable energy development accompanied by environmental and economic development. The figure demonstrates the relationship between energy, economy, and social development for the purpose of sustainable energy production [213]. There have been a lot of studies concerned with developing technologies, methods, and national policies that focus on building sustainable energy production strategies; these studies have synthesized nanomaterials for sustainable energy production [214], developed national energy policies to enable SEP in Turkey [215], developed green SEP in China by tracing garden waste biomass sources [216], constructed a theoretical framework for hybrid renewable energy using photovoltaic energy and hydro-energy for SEP [217], projected long-term SEP in Saudi Arabia until 2030 [218], developed an SEP strategy by pursuing sustainable development goal 7 (SDG 7) criteria including access to affordable modern energy services, sustainable energy consumption, sustainable energy supply, and one more criterion of energy security [219], applied an energy optimization form to accomplish SEP with reduction strategies to alleviate the environmental impact of pollution and emissions in Pakistan [220], provided national policies to help decrease emissions and planned strategies to accomplish SEP in Turkey [221], developed solar energy and biomass energy for SEP in Nigeria [222], outlined a plan to achieve sustainable energy development by using renewable energy sources and making national policies for SEP in Azerbaijan [213], and determined the impact of globalization on sustainable energy production by developing and using strategies of renewable energy.

5. Benefits, Challenges, and Solutions

5.1. Benefits

Hybrid renewable energy system have many benefits such as providing clean energy for everyone with high availability and low cost [223], increasing power penetration approaches, decreasing the intermittency of renewable energy sources, enhancing the reliability of research and development into renewable energy resources, promoting the electrification of remote and rural areas, encouraging the exploitation of new energy harvesting techniques [224,225], bringing the circular economy benefit to rural areas [226], achieving the rural health benefits of cost-effectiveness and greenhouse gas emissions reduction [227], contributing to the net-zero energy area by using solar power, thermal energy storage, and heat pump units [228], enhancing the efficiency and stability of energy systems [229], accomplishing cost reduction and efficiency improvement [230], improving the reliability of power systems [231], decreasing carbon dioxide emissions [232], improving socioeconomic development issues regarding healthcare, education, and economy in local areas [233], combining single renewable energy systems into one HRES to increase the electrification of countries and territories [234], driving a multigeneration system [235], contributing to sustainable development all over the world [236], effectively using waste for net-zero purposes [237], having outstanding characteristics of reliable, clean, and affordable energy for sustainable development [238], avoiding the intermittence resulting from a single renewable energy [239], and providing an affordable energy source for low-income households [240].

There are tremendous benefits to introducing triboelectric nanogenerators into hybrid renewable energy systems because of the outstanding characteristics of TENGs such as their flexible structure [241], self-powered source [242], lightweight nature, use of easy-to-find materials, simple structure, renewable energy resource [243], and use as a sustainable energy source [244]. A triboelectric nanogenerator can easily integrate into the power grid. In summary, renewable energy is the answer for reducing carbon dioxide emissions, protecting the environment, and pushing sustainable development. HRESs bring about many benefits, for example, decreasing fluctuations in RE, improving the output performance of energy systems, enhancing energy conversion efficiency, and optimizing energy transduction.

5.2. Challenges

There are lots of challenges that HRESs face during all the procedures of designing, building, and operating the system, such as technology and technique problems. Renewable energy systems need a large area. RES sources are often affected by the environment. Climate conditions, such as the day/night period, sun/raining time, and windy conditions, have directly affected RES performance [245]. By integrating HRESs into the power grid, there are many challenges that research groups have had to overcome, such as enhancing economic effectiveness, improving energy storage technologies [246], finding methods and techniques to solve problems of reliability in the systems [247], seeking technologies to solve the problems of optimization and effectiveness of the system [248], finding a way to improve the reliability of the power system in an HRES [249], researching methods and technologies to achieve multi-objective optimization of HRESs [250], facing the problems of computation, finance, and environment in rural areas when deploying HRESs [251], facing prominent problems from policies, regulations, and institutions when implementing HRESs [252], controlling excess electricity from HRESs [253], facing technology differences during the integration of HRESs with SRESs [254], determining the parameters required to penetrate an single renewable energy into an HRES [255], problem of high costs when constructing, exploiting, and operating HRESs [256], building mathematical models to optimize the size of HRESs [257], and facing many problems with the stability, quality, reliability, and operation of HRESs [258]. To briefly summarize, there still remain challenges that TENGs will encounter before they can be used in HRESs because the input sources are exposed to natural fluctuation and weather conditions. The output performance of TENGs and HRESs are small in comparison with the energy needed for human development. The limitations of technologies, materials, and working mechanisms are big problems during the integration of TENGs into HRESs and the power grid. The different distribution of renewable energy sources, which can cause disadvantage problems for establishing the infrastructure of the HRESs.

5.3. Solutions

To overcome these challenges and gain even more benefits from HRESs, there are many solutions that have been developed by research groups, such as applying an optimization method in the management and modeling of HRESs to control the output performance of HRESs [259], using a distributed energy resource customer adoption tool to optimize the size of HRESs for a microgrid [260], promoting the benefit sharing strategy to obtain maximal benefits of HRESs with minimal electrical cost and minimal carbon dioxide emissions [261], using a hybrid optimization tool to optimize HRESs for the criteria of efficiency, electrical cost, environmental protection, emission problems, and lifetime of the hybrid system [262], using innovative technologies of machine learning and the advanced inverter to solve challenges of sustainability, intermittency, optimization, power storage, and management of the system [263], building frameworks for integrating RESs into the power grid with the benefits of effective energy management, real-time power management, and power forecasting ability [264], using the HOMER Pro tool to optimize HRESs and enhance their advantages, such as decreased gas emissions, reduced electrical costs, utilization of RES resources, and effective combination of renewable energy units of biogas, photovoltaic energy, and energy storage systems [265], focusing on designing and optimizing HRESs to achieve sustainable development, green transportation, clean hydrogen energy, cost-effectiveness, and rural electrification [266], supporting frameworks to help with the selection of an HRES for sustainable development [267], using a hybrid optimization model for electric renewable software to achieve investment reduction and size optimization for HRESs [268], using a receding horizon optimization method with predictive control algorithms to optimize the operation of HRESs [269], using battery storage systems to enhance the reliability of HRESs [270,271], using a multiobjective optimization model to deal with the problems of economy, environmental impact, and carbon dioxide emission reductions [272], introducing a particle swarm optimization (PSO) to optimize HRESs with the objectives of social–political improvements [273], applying a mixed-integer linear programming tool to determine the high energy demand area [274], using artificial intelligence technology (AI) to solve problems with efficiency, complexity, and reliability in HRESs [275], using a hybrid meta-heuristic optimization technology to ensure reliability and accomplish the multiobjective goals of HRESs [276], using artificial neural networks (ANNs) to predict the energy generation needed for sustainable energy production [277], and using simulation tools to optimize HRESs with reliability indicators of financial cost optimization, excess energy minimization, and load protection [278]. In brief, there are solutions to fight the challenges of HRESs that include using energy storage units to store energy, reusing energy during periods where there is a lack of input trigger or bad weather conditions, and using more and more renewable energy transduction systems to optimize the energy conversion efficiency. The development of new technologies, methods, and materials to improve the output performance of HRESs are still needed. The utilization of optimization methods when identifying the distribution of renewable energy sources for siting infrastructure of HRESs is encouraged to achieve the highest possible energy conversion efficiency.

6. Conclusions

Renewable energy is crucial for sustainable energy development given the rapidly increasing energy demand in the world. A single renewable energy system has limitations to its stable generation due to the influences of weather conditions, seasons, day/night time, and working conditions. Triboelectric nanogenerators produce electricity by converting mechanical energies that exist prominently in the surrounding environment such as motion, walking, vibrations, water flow, sounds, and ocean energy. Triboelectric nanogenerators are potential for renewable energy transduction systems because they can convert many renewable energy sources (such as wind and ocean energy) into electricity. Hybrid renewable energy systems can improve output performance, enhance efficiency, and decrease fluctuation during energy generation procedures. This paper reviews recent methods and techniques of developing HRESs to enhance energy transduction efficiency, output performance, and sustainability of HRESs. Introducing triboelectric nanogenerators into HRESs brings many benefits such as energy conversion efficiency improvement, sustainable energy generation, and other practical applications. This paper mentions the advantages, challenges, and solutions offered by HRESs to improve its efficiency, development, and applications. The results show that TENGs are a prospective technology that can be integrated into HRESs to solve the problems of intermittency and variability in RE systems. The results hope to motivate the development of hybrid renewable energy systems for practical applications and sustainable energy development in the near future.