Pros and Cons of Hybrid PV-Wind Energy Systems

The switch to hybrid solar-wind energy system reduces carbon emission and electricity bills for homeowners. The system can also provide US Residential Renewable Energy Tax Credit. This benefit provided a 30% incentive tax credit for wind, solar, and hybrid residential energy systems, with no cap limit, for systems installed by 12/31/19. After that date, the tax credit remains in place but is reduced to 26% for systems installed by the end of 2020 and 22% for those installed before January 1, 2022. With these incentives in place, the savings on your monthly energy bill will quickly offset the cost of installing a renewable energy system. Furthermore, with grid-connected system, one can reduce electricity bill zero or make some profit from utility company. The investment of the capital cost for installation can be a negative for solar-wind hybrid energy. Depending on location, you may not be able to recover this cost rapidly. While rooftop solar panels generally require very little maintenance, wind turbines need regularly scheduled maintenance so they can perform optimally. For off-grid operation, sufficient storage capacity is necessary in order to avoid waste of excess energy generated by the hybrid system.

Theoretical Case Studies for PV-Wind Hybrid Energy System

Carefully thought through management strategies are important for hybrid wind- solar system. Stroe et al. [135] evaluated two power and energy management strategies for a hybrid residential PV-wind system with battery energy storage for Denmark. The solar PV total installed capacity in Denmark has exponentially increased in the last years. According to the International Renewable Energy Agency, the cumulative solar PV capacity increased from 17 MW in 2011 to 399 MW in 2012, reaching 790.4 MW by the end of 2016 [136]. The vast majority of the installations (approx. 95%) are represented by residential roof-top PV systems with power levels below 6kW. This trend is expected to continue as by 2020 the aim is to generate 5% of electricity from residential solar PV systems [137]. Furthermore, Denmark has always been a leader in the wind power production sector. Nowadays, approximately 33% of the installed wind turbines have a rated power below 25 kW and most of the times they are connected to the low-voltage grid [138]. These renewables’ grid integration trends combined with the presence of new loads such as heat pumps and electric vehicles are threatening the stable and reliable operation of low-voltage grids causing voltage unbalances, neutral point displacement, voltage flickers, etc. The aforementioned issues can be mitigated using battery energy storage [138,139]. Among the available storage technologies, lithium-ion batteries represent an obvious solution because of their characteristics (e.g., high efficiency, long lifetime, low self-discharge) combined with rapid price decrease [140,141]. Nevertheless, the installations of such systems should be accompanied by the availability of a power and energy management system, which will control and optimize the power flow by providing different services to the grid and/or to the end-user (e.g., power smoothing, peak shaving, selfconsumption maximization, etc.) [142].

The aim of the study by Stroe et al. [135] was to investigate different power and energy management strategies for a hybrid residential PV-wind system using a lithium-ion battery energy storage. It is well known that the performance of lithium- ion batteries is very sensitive to the operating conditions (i.e., load current, temperature, state-of-charge, state-of-health). Thus, in order to develop accurate power and energy management strategies, a lithium-ion battery electric model was developed and parameterized based on extensive laboratory tests. Furthermore, the study developed simple and robust performance models for a small wind turbine and solar PV panels. In order to perform realistic study cases, the study has used real-life data for PV generation, wind power generation, and residential household consumption with a one-second resolution. The behavior of the hybrid energy system was evaluated for power smoothing and energy blocks applications for two different scenarios (i.e., a summer day and a winter day). For the power smoothing application, an moving average functionality (MAF) was considered with two averaging time windows of 5 and 15 minutes. In both cases, the desired smoothing effect was achieved, while the battery was subjected to approx. 3.4 and 1.5 full cycles, for a summer and winter day, respectively. Furthermore, the battery was used to maximize the usage of the renewable energy and minimize the electricity bill, by minimizing the energy bought from the utility grid. This was achieved by computing a 15-minutes average power curve for an entire day, by considering the load profile of the house and the produced renewable energy. The difference between the computed curve and the overall house power curve was charged/discharged from the battery. For the considered size of the battery (i.e., 6kW), the maximum power of the battery was never reached while the Li-ion battery was subjected to 3.75 full cycles during a summer day and 1.75 full cycles during a winter day.

Numerous other theoretical studies for PV-Wind with and without storage for home electricity and heating and cooling need have been reported in the literature [14,143,144]. Nakomcic-Smaragdakis and Dragutinovis [144] analyzed the application of PV-Wind system for electricity and heat supply of a typical household in Serbia, as well as the cost-effectiveness of the proposed system. The influence of feed-in tariff change on the value of the investment was analyzed. Small, grid- connected hybrid system (for energy supply of a standard household), consisting of geothermal heat pump for heating/cooling, solar PV panels, and small wind turbine for power supply was analyzed as a case study. System analysis was conducted with the help of RETScreen software. Results of techno-economics analysis showed that investing in geothermal heat pump and PV panels is cost-effective, while that is not the case with small wind turbine. Bakic et al. [143] examined technical and economic analysis of grid-connected PV/Wind energy stations in the Republic of Serbia under varying climatic conditions. The technical and economic data, of the various grid-connected PV/wind hybrid energy systems for three different locations: Novi Sad, Belgrade and Kopaonik, using the transient simulations software TRNSYS and HOMER were obtained. The results obtained in this paper showed that locations and technical characteristics of the energy systems have an important influence on the amount of delivering electrical power to the grid. The CO, emissions reductions, obtained on the basis of delivered electrical power to distribution networks, were also analyzed. Economic analysis was carried out using life cycling cost method. The adoption and implementation of feed-in tariffs have a significant role in enhancing the implementation of technologies that use renewable energy resources. Many other similar studies are described in my previous book [14].