The availability of energy plays a very important role in the economic growth and sustainable development of a society and nation. Around 10% of the world’s population (789 million people), especially in remote areas, live without electricity [1
]. Some of the reasons behind this include the high financial cost of the extension of a grid network to such areas, low population density, and several other cultural and social aspects. Most of the people in these regions depend on fossil fuel and locally available traditional fuels, such as wood and animal waste, to meet their energy demand, due to its easy availability. However, there are several problems associated with using fossil fuel, such as high variability in the prices, environmental degradation, and health issues. One of the solutions to overcome the drawbacks of fossil fuel and provide clean and easy electricity in these regions is using available renewable energy sources in that region [2
]. This also results in economic development, an improved ecological balance and human development [3
]. However, the intermittent and unpredicted power output of renewable sources results in a non-viable power supply and creates the need for a methodology for obtaining reliable energy from renewable energy sources. For an uninterruptible and viable power supply, various energy sources can be integrated to meet the electricity demand. Such systems are called hybrid renewable energy systems (HRESs), and usually consist of two or more renewable energy sources. Some of the advantages of HRESs include (i) the optimum utilization of renewable sources, (ii) improved controllability, (iii) increased load matching and (iv) the lower operational cost.
Different techniques have been developed and used by researchers to find the most appropriate size for a HRES. Tito et al. [4
] suggested that the configuration of the HRES can be considered as optimized if it can minimize the overall system cost or the cost of energy with no unmet demand left over for all the classified socio-demographic load profiles of the site. Jamshidi et al. [5
] estimated the optimal size of a Wind-PV-Diesel generator-based HRES using polynomial regression and support vector regression models. Alberizzi et al. [6
] used a mixed Integer Linear Programming (MILP)-based optimization algorithm to find the optimal size of an HRES for a place located in South Tyrol, Italy. Martin-Arroyo et al. [7
] investigated a stand-alone PV-Wind-based hybrid system using the smart spinning reverse management method. Similarly, Das et al. [8
] used metaheuristic optimization techniques to find the optimal economical configuration to meet the electrical demand of a radio transmitter station in India. The results show that the optimal configuration includes a 69.2 kW PV panel, a 16 kW biogas generator, a converter size of 30 kW, 21 battery bank units, and an upper reservoir volume of 2081.5 m3
, with a total net present cost (NPC) of USD 0.813 million. Rezzouk and Mellit [9
] carried out the techno-economic feasibility and sensitivity analysis of a PV-Diesel-Battery-operated HRES, with the penetration of PV varying from 0% to 100%. From the results, it can be observed that system stability and optimum performance can be achieved with 25% PV penetration. A sensitivity analysis showed that global radiation has a significant effect on the NPC and CoE of the system. Rahman et al. [10
] showed that biogas and solar systems can be integrated to develop a hybrid energy system that can meet both electrical load and thermal (cooking) demands, and can efficiently replace conventional facilities. The results also show that monetary savings worth USD 309 to 412 per year can be achieved by using the proposed hybrid renewable energy system. Considering climate diversity and the energy efficiency of buildings, Mokhtara et al. [11
] investigated the optimal sizing and mapping of hybrid renewable energy systems for an off-grid building at seven different locations in Algeria. The results show that climate zone and the energy performance of the building have significant effects on the optimal sizing of the HRES. The study makes recommendations related to efficient energy management between energy sources, stored energy and load demand for the optimization of the overall HRES. Baruah et al. [12
] carried out techno-economic feasibility analyses of an HRES for the academic township in Sikkim, India, using HOMER. The results show that the optimum system is a PV-Wind-Biogas-Syngas-Hydrokinetic-Battery-based system with an LCOE of USD 0.095/kWh. Al-bonsrulah et al. [13
] carried out an analysis of a hybrid system for the Bahr Al-Najaf region. The results show that the energy contributions of fuel cell, wind turbine and PV are 4.38%, 26.3% and 69.3%, respectively. Katsivelakis et al. [14
] performed a techno-economic analysis of a hybrid renewable energy system on Donoussa Island, Greece, by varying the contributions (20%, 50% and 100%) of renewable energy resources. The results show that with a 50% renewable energy contribution, a system can be obtained with 0% excess energy, an NPC of EUR 4,031,102.3 and a COE of EUR 0.2401/kWh. Kanase-Patil et al. [15
] showed that an HRES with micro hydropower, biomass, biogas, solar energy, wind and energy plantation, with individual contributions of 44.99%, 30.07%, 5.19%, 4.16%, 1.27% and 12.33%, respectively, can provide for the electrical and cooking needs of seven off-grid villages in Uttarakhand, India. The results also showed that the optimal HRES system had 0.95 energy index ratio, at the optimized cost of Rs 19.44 lacs and a COE of Rs 3.36 per unit.
Elavarasan et al. [16
] carried out a study on the demand-side management of three different configurations of energy source, considering user satisfaction. The analysis showed that, overall, the traffic in the load can be reduced significantly by reductions in summer and winter peak load demands of 6.33% and 11.5%, respectively. Kumar et al. [17
] carried out a techno-economic and environmental study of a residential community in South India, considering the SDG7 goals by integrating different system configurations of a photovoltaic/wind turbine/diesel generator/battery energy storage system (PV/WT/DG/BESS). The results show that a hybrid renewable energy system with PV + DG + BESS is the most cost-effective configuration for the location of the study. Li et al. [18
] carried out a techno-economic feasibility study of a hybrid renewable system used to meet the load demand of a house in Urumqi, China, using different configurations of energy source. The result shows that the total net present cost (NPC) of the system can be reduced by 9% and 11% compared with a PV/battery and wind/battery power system if a hybrid system is used employing PV/wind/battery. The sensitivity study performed by the authors also shows that the total PV module generation of a hybrid system combined with a tracking system is greater than that of a system with an optimized PV module tilt angle.
Wu et al. [19
] carried out the multi-objective optimization of an HRES integrating biomass CHP, PV and a heat storage system, considering economic and environmental emissions. The result shows that the optimized system with percentage contributions from CHP, PV and grid of 51.22%, 1.54% and 47.24%, respectively, can facilitate a trade-off between economic factors and emissions. Suleman et al. [20
] developed an HRES employing solar and geothermal energy for multigeneration applications. The result shows that by combing these two energy sources, the overall energy and exergy efficiency of the system can reach 54.7% and 76.4%, respectively. Chang et al. [21
] studied a bio-hydrogen-based renewable system (BHIRES), which integrates the hydrogen generation of biomass fermentation, renewable energy power generation, and electrolysis, for hydrogen production and its further storage, and uses fuel cells for heat and power generation. The analysis showed that the BHIRES is cost-effective as compared to wind/PV/hydrogen, and reduces the cost of energy of the system by 9.6% from USD 1.005 kWh to USD 0.908 kWh. The result also shows that the BHIRES system reduces the final cost of the system by 11.6% as compared to a wind/PV/hydrogen system.
The experiment conducted by Karthick et al. [22
] on an integrated PV-PCM system at Kovilpatti, Tamil Nadu, India, using glauber salt (Na2
O) as the PCM, showed that the electrical efficiency of the PV panel was increased by 10% due to a reduction in its operating temperature by 8 °C. Stropnik and Stritih [23
] showed that, with PCM, the surface temperature of the PV panel can be lowered by a maximum of 35.6 °C, resulting in 9.2% additional power compared to a conventional PV panel. Khanna et al. [24
] analyzed a finned PCM integrated PV panel, showing that the power produced by the PV panel in a warmer climate increases in the range of 10.1% to 12.1%, and in colder climates it increases in the range of 5.4% to 6.7%, as compared to the reference PV panel.
From the literature review, it can be observed that several researchers have optimized a hybrid renewable energy system using different technologies and methodologies. However, no work has been found in the literature where a phase change material has been integrated with a PV and hybrid renewable energy system. Phase change materials have the ability to cool down the PV [25
] and store huge amount of energy in a latent form, consequently increasing the PV electrical efficiency [26
]. The present study investigates how the integration of a phase change material with a PV panel will affect the optimization of the HRES, which thus has the potential to reduce the cost of energy. The mathematical modeling and optimization of the system have been carried out.
A hybrid energy system usually consists of two or more renewable energy sources used together to provide increased system efficiency. For uninterruptible and viable power supply, various cost effective energy sources, such as solar, wind, hydro, and biogas, can be integrated together to meet the electric load demand in a reliable manner. There are various advantages to a hybrid renewable energy system (HRES): (i) better utilization of renewable energy, (ii) better load matching, (iii) better controllability, and (iv) lower operational and maintenance cost.
In the present study, the performance of a hybrid renewable energy system consisting of PV, PCM, a biogas generator, wind and battery has been investigated. It can be observed that due to the ability of the PCM to absorb the heat from the photovoltaic panel, the performance of the PV panel increases, which results in a reduction in the net present cost and the cost of energy of the overall system. For the PV-Wind-Biogas generator-Battery-based off-grid system, the integration of a phase change material with a PV panel results in a saving of USD 0.22 million in terms of net present cost, and reduces the cost of the energy of the system from USD 0.099/kWh to USD 0.094/kWh. Similarly, for another off-grid HRES configuration of PV-Wind-Battery, the integration of a phase change material with the photovoltaic panels results in a saving of USD 0.17 million, and also reduces the cost of energy of the system from USD 0.12/kWh to USD 0.105/kWh.
The present work can be expanded by integrating the PV-PCM with other renewable energy systems for different geographical locations. The PCM-based energy system can also be integrated with a cogeneration energy system for enhanced system efficiency and a lower cost of energy.