A hybrid system, such as solar and wind, may be more successful than nonhybrid systems in accelerating the transition from conventional to renewable power sources. These new energy sources have several challenges, such as intermittency, storage capacity, and grid stability.
1. Introduction
Solar and wind energies are domestic and free energy sources and some of the best local solutions for increasing energy demand. According to the Fraunhofer Institute for Solar Energy Systems photovoltaics report, worldwide installed photovoltaic (PV) capacity increased to more than 515 gigawatts, supplying approximately two percent of global electricity demand
[1]. In addition, 60.4 gigawatts of wind energy capacity were installed globally in 2019, a 19 percent increase
[2].
Sustainable renewable energy is considered a green energy source. However, it is not a fully green source due to the production of renewable-energy system parts and components that are often manufactured in factories and facilities powered by nongreen energy. In addition, the transportation of these systems’ parts and components usually depends on conventional fuels. Moreover, greenhouse-gas (GHG) emissions are undesirable, causing pollution in the atmosphere. The primary greenhouse gases are water vapor (H
2O), carbon dioxide (CO
2), methane (CH
4), nitrous oxide (N
2O), and ozone (O
3). Conventional energy sources such as coal and other fossil fuels are significant sources of GHGs
[3][4][5]. The burning of these fuels contributes to the well-known global-warming phenomena in which the earth’s atmosphere warms by absorbing solar energy and retaining it in the atmosphere
[6].
Renewable energy is the best choice for providing clean, reliable, and sustainable energy. The electricity generated from clean sources improves quality of life and enhances economic growth. In addition, replacing conventional energy sources like fossil fuels with renewable-energy sources helps mitigate world climate change due to greenhouse-gas emissions. While renewable energy is a domestic source, it faces limitations due to high initial cost, intermittency, and geographic boundaries
[7].
Annual energy consumption growth is 1% for developed countries and 5% for developing countries
[8]. In Jordan, the need for electricity increases each year, with the primary energy sources for 2018 (the most recent data from the Ministry of Energy and Mineral Resources) reported as imported oil and natural gas, with a share of 87% of total energy consumption (9712 kt), followed by renewable energy at 7%
[9][10]. The transportation sector consumes 49% of Jordan’s total national energy demands, while the second-highest share is 21.5% from residential consumption, according to the last data report from Jordan’s National Electric Power Company
[11]. One of Jordan’s most significant energy challenges is that increasing energy costs contribute to slower economic growth since most of its energy is imported. Buildings in general use approximately 20–40% of the total energy demand in developed countries
[12], where conventional energy sources are still the dominant sources. Among active solar solutions, photovoltaic systems are intensely studied thanks to the aesthetical and technical opportunities offered in the last years as well as to the publication of clear design criteria and recommendations
[13].
Renewable-energy system electrical grids need to be more flexible and dynamic than conventional grids to increase their contribution to total energy generation and overcome the challenges of intermittency and varying availability at specific locations. Using decentralized power-generation concepts such as microgrids, smart grids, and standalone (off-grid) power systems can increase the share of renewable energy. Green buildings that depend on sustainable sources of energy such as solar and wind can help the environment and the consumer by replacing conventional energy sources with accessible, domestic, and green-energy sources
[14].
The design of grid-connected hybrid energy systems, shown in Figure 1, involves and determines factors such as the most suitable components, their sizes, and power management (PM) while considering the location and load demand.
Figure 1. Grid-connected hybrid renewable-energy systems.
2. Hybrid Renewable-Energy System for Green Buildings
Addressing the design and simulation of hybrid renewable-energy systems, Suresh et al.
[15] optimized an off-grid hybrid energy system through the control, sizing, and choice of components. They considered a cost-effective power solution for electrifying villages in the Kollegal block of the Chamarajanagar district in India. The aim was to reduce the system’s net present cost (NPC), cost of energy (COE), unmet load scenario, and CO
2 emissions, which were computed using a genetic algorithm and also using the HOMER Pro Software. The results of the two methods were compared for four HRES configurations. The simulations suggested that the combination of biogas, solar, wind, and fuel cells with battery was the optimal solution with zero unmet loads and the least energy cost at USD 0.163 per kWh.
Bagheri et al.
[16] focused their research on proposing a systematic approach to optimal planning of hybrid renewable energy for neighborhoods. They studied the impact of system economics on the life-cycle cost analysis of the optimal proposed hybrid renewable systems for Vancouver, Canada. Wind energy was found to be an uneconomical choice, while biomass appeared to be the optimal hybrid system. System configurations, capital investment, and operating costs controlled the economic decision. The results showed that the optimized proposed systems’ net present costs (NPCs) were USD 59 M, USD 116 M, and USD 290 M. The study suggests a framework for local governments and planners to integrate neighborhood-scale hybrid renewable-energy systems in their jurisdictions. Therefore, introducing biomass waste as a renewable-energy resource can effectively enhance the techno-economic performance of urban regions’ hybrid renewable-energy systems, limit landfill waste, and create green jobs for the community. The authors also develop a new model of the hybrid energy system using the HOMER algorithm that optimizes techno-economic and environmental performance.
Olatomiwa et al.
[17] suggest a solution for healthcare centers or clinics in remote areas using an off-grid hybrid renewable-energy system. They conducted an analysis of wind and solar sources for a selected rural location in Nigeria based on meteorological data with an optimal technical and economical design. Sizing hybrid renewable-energy system components such as wind, PV, battery, and inverter using the HOMER software, they studied each site’s solar and wind data. They showed that the PV–wind–diesel–battery hybrid system configuration was optimal for a health center in the rural Iseyin site, with an NPC of USD 102,949 and a COE of USD 0.311/kWh.
In an economic assessment of hybrid renewable-energy systems, Ali and Jang
[18] proposed a model for an off-grid HRES for remote Deokjeok-do Island in South Korea using daily mean-load electricity-consumption data for one year (24,720 kWh). They collected the average annual wind speed and the daily solar radiation values of 3.6 m/s and 4.13 kWh/m
2, respectively. A total of 8760 simulations were needed to compute the hourly load demand using the HOMER software. The disadvantages found for this system were the surplus and electricity deficit. To find the most suitable HRES, the authors investigated criteria such as leveled cost of energy (LCOE) and net present cost (NPC). The total estimated cost for a wind-energy system was USD 11.3 M. However, the estimated cost was USD 17.6 M for a solar energy system, and its LCOE was USD 0.1594/kWh. Both systems consisted of one STX 93/2000 wind turbine and 2504 kW PV panels (for system one) and 3157 kW PV panels (for system two). They have also designed a pumped hydro storage (PHS) system to mitigate the surplus and deficit of electricity for the two systems and conducted an economic comparison between the PHS and a battery which indicated that the PHS could be a less expensive choice.
Odou et al.
[19] also included a battery as a storage system and analyzed a case study of the village of Fouay in the Republic of Benin from a techno-economic perspective. They suggested a hybrid PV–diesel generator (DG)–battery system as the best choice to electrify the village. Their study showed that it has the lowest net present cost, provides a reliable power supply, and reduces battery storage cost since its battery requirement is only 30% of a standard PV–battery standalone system. The PV–DG–battery system has the shortest payback period of 3.45 years and a 33.3% internal rate of return (IRR). The results suggested that the off-grid hybrid PV–DG–battery system with a COE of USD 0.207/kWh was a suitable technology to sustainably electrify the village as projected in the county’s master rural electrification plan. The research recommends this system for electrification projects in Benin in the future.
The ability to use biomass energy depends on location and the available raw material, as discussed by Kasaeian et al.
[20]. They conducted a techno-economic investigation to evaluate the optimal HRES consisting of a hybrid PV, biomass, and DG for Bandar Dayyer, Iran. The simulation results using the HOMER software showed that the total amount of electricity production by these systems was equal to 470,176 kW, with 22,409 kW produced by a PV–generic system and 447,767 kW produced by a PV–diesel–generic system. The economic analysis result implies that the NPC for the PV–wind system is USD 23,148.84, ensuring the benefits of using an HRES over a PV–diesel–generic system
[20][21].
Karunathilake et al.
[22] presented an optimized HRES at the building level to achieve the net-zero level goals of Canada and British Columbia. The study considers factors to develop an optimized model, such as minimizing energy system cost and life cycle environmental impacts and maximizing operational cost savings. The results indicated that ground sources such as heat pumps and solar sources such as photovoltaics were the optimal energy choices for multiunit residential buildings for the selected site location in British Columbia, Canada. The best energy system combination supplied 44% of the building’s energy demand through the renewable-energy system. However, reduced emissions and operational costs can also be achieved with an HRES. The overall life-cycle impacts could be reduced by 11.4%, and annual carbon emissions could be decreased by 21.70%. For the optimal solution, the levelled cost of energy does not vary more than ±0.05% from the standard grid electricity price, and the system will pay for itself within 22–23 years. The authors state that the proposed system’s per capita annual energy cost saving was USD 7. While renewable-energy systems can promote environmental and energy security, they carry an economic burden, particularly for small communities and neighborhood-level applications.
Another study on large buildings was conducted by Islam, Md Shahinur
[23], who presented a techno-economic analysis on a grid-connected HRES for a large office building in France. The data was collected from the study location, and the HOMER simulation software was used to compute the technical, economic, and environmental parameters of the PV–Grid system. The economic evaluation parameters considered in the analysis were the NPC, COE, and energy payback time (EPT). The results show that the PV–Grid system was the most cost-effective system configuration and minimizes more than 90% of emissions compared to the existing emissions at the study site. Furthermore, the system performs reasonably well with the variation in electric load and solar insolation. The HRES will be most competitive during rising electricity prices with a COE of USD 0.087/kWh. Furthermore, the results also indicate the superiority of the HRES if a carbon tax is imposed in the future.
In literature related to mathematical modeling, Mayer et al.
[24] studied the optimization of an HRES and indicated that the previous studies do not consider life-cycle environmental impacts other than GHG emissions. For factual life-cycle bases using the environmental footprint corresponding to the NPC as an objective function, the research includes the complete set of commercially available renewable-energy systems handling heating and electricity demand at the household level. Renewable energy was better than fossil fuels even when considering life-cycle impacts. However, renewable-energy systems are not emission-free and have some adverse environmental profiles, and there is no universal solution for reducing their effects. Their study used a genetic algorithm to solve and ecodesign the economic and ecological multisizing problem of a building-sized microgrid. The result of the life-cycle assessment for an HRES design provides a framework for practical applications such as supporting consumer decisions or policymaking.
The choice of an optimal system by cost effectiveness was studied by Wang et al.
[25] using a two-stage optimal framework to solve the design problem for an HRES in a seaport area. They focus on finding the best renewable-energy subsystems with a specific installed capacity to ensure the lowest investment cost and minimize operation costs by considering stochastic characteristics of wind-energy production and energy demands. The result confirms the desirability of maintaining constraints such as power balances, capacity limitations, and emission regulations. They found that the choice of the optimal wind–storage–onshore hybrid power system for a container seaport with different emission limitations and wind speeds can be applied to achieve optimal installation capacity and cost effectiveness.
Fulzele and Daigavane
[26] researched the design and optimization of an HRES consisting of a solar photovoltaic (PV), wind generator, and battery with a converter. They used an improved hybrid optimization genetic algorithm (IHOGA) simulation developed in the electric department of the University of Zaragoza. The effect of variables such as global solar radiation, wind speed, and PV panel cost was considered. The results showed that economic viability should be prioritized over technical considerations. In developing countries, poor economic conditions are a limitation for high-cost hybrid renewable energy.
Focusing on the environmental effects of a base system and a new system that they proposed, Jeong et al.
[27] conducted a technical design and analyzed the use of renewable-energy sources to supply green buildings. They combined three types of buildings in different regions to find the optimal design for minimum cost and reduced carbon dioxide emissions compared with the standard conventional energy sources. The case study found that the most significant power consumption was from diesel generators, and the solar PV system works as a buffer for temporal balance. However, they suggested that if the building has enough area to install a wind turbine, it would be a promising solution for realizing the goal of green buildings. The estimated COE for the HRES was six times more than the electricity price, though the HRES system shows better environmental performance with less CO
2 emission than a conventional system. Although the system in this research was not economical, it can still be helpful as a guideline for stakeholders and the government.
This entry is adapted from the peer-reviewed paper 10.3390/su15097529