The Land Sparing, Water Surface Use Efficiency, and Water Surface Transformation of Floating Photovoltaic Solar Energy Installations

Aquatic environment impacts of floating photovoltaic and implications for climate change challenges

With the aggravation of global warming and the increasing demand for energy, the development of renewable energy is imminent. Floating photovoltaic (FPV) is a new form of renewable energy generation. However, the impact of FPV on the aquatic environment is still unclear. By long-term empirical monitoring and data analysis, this paper reveals the shading effect of large-scale FPV power station on aquatic environment for the first time. The results show that: (1) Compared with the non-photovoltaic (NP) zone, FPV only significantly reduces the concentration of dissolved oxygen in the photovoltaic (P) zone. (2) The concentration of chlorophyll a, nitrate nitrogen and total phosphorus increase, while pH and ammonia nitrogen decrease. FPV only causes an effect of the same order of magnitude as the initial concentration, and has no significant adverse effects on the nutritional status of the water body at a coverage ratio less than 50%. (3) FPV has a cooling effect on the water body during the daytime and a thermal insulation effect at night, with the most pronounced impact on peak water temperature (Tw). The heating and cooling process of Tw in P zone usually lags behind the NP zone by 1-3 h. The diurnal fluctuation and vertical difference of Tw as well as the stability of water body are reduced under the shading of FPV, alleviating the influence of climate change on Tw and water body stratification. (4) If 10% of the water area larger than 1 km2 in China are used to develop FPV, more than 900 million tons of CO2 emissions can be reduced, and about 5 billion m3 water can be saved, which is significant in the context of climate change. In general, this paper provides a reference for the future aquatic environmental impact assessment of FPV and the formulation of related policies.

Floating solar panels on reservoirs impact phytoplankton populations: A modelling experiment

Floating solar photovoltaic (FPV) deployments are increasing globally as the switch to renewable energy intensifies, representing a considerable water surface transformation. FPV installations can potentially impact aquatic ecosystem function, either positively or negatively. However, these impacts are poorly resolved given the challenges of collecting empirical data for field or modelling experiments. In particular, there is limited evidence on the response of phytoplankton to changes in water body thermal dynamics and light climate with FPV. Given the importance of understanding phytoplankton biomass and species composition for managing ecosystem services, we use an uncertainty estimation approach to simulate the effect of FPV coverage and array siting location on a UK reservoir. FPV coverage was modified in 10% increments from a baseline with 0% coverage to 100% coverage for three different FPV array siting locations based on reservoir circulation patterns. Results showed that FPV coverage significantly impacted thermal properties, resulting in highly variable impacts on phytoplankton biomass and species composition. The impacts on phytoplankton were often dependent on array siting location as well as surface coverage. Changes to phytoplankton species composition were offset by the decrease in phytoplankton biomass associated with increasing FPV coverage. We identified that similar phytoplankton biomass reductions could be achieved with less FPV coverage by deploying the FPV array on the water body's faster-flowing area than the central or slower flowing areas. The difference in response dependent on siting location could be used to tailor phytoplankton management in water bodies. Simulation of water body-FPV interactions efficiently using an uncertainty approach is an essential tool to rapidly develop understanding and ultimately inform FPV developers and water body managers looking to minimise negative impacts and maximise co-benefits.

Energy performance analysis of tracking floating photovoltaic systems

Floating photovoltaic systems (FPV) are an innovative technology, in which photovoltaic modules are installed on water surfaces with the aim of reducing land occupation and at the same time increasing its efficiency and creating synergies with aquaculture and hydroelectric plants. The purpose of this study is to evaluate the energy performance on an annual basis of a fixed G/FPV (ground/floating photovoltaic) system, with vertical, horizontal or two-axis tracking, with mono or bifacial modules. The simulated data for FPV (floating PV) systems are compared with those of a GPV (ground PV) system through performance indexes. The analysis of the energy output is carried out depending on the geometric variables of the plant. The energy production of PV systems is highly dependent on the local climate. Therefore, the study was developed for two locations characterised by different components of diffuse solar radiation, one at high latitudes and the other at mid-latitudes. The two locations are: Anapo Dam in Sicily (Italy) and Aar Dam in the Lahn-Dill district (Germany).

As for the gain due to the bifaciality of the systems with bifacial modules, it can be stated that for the analyzed configurations, a gain greater than 3% can be obtained for Anapo Dam in Sicily and greater than 4% for Aar in Germany.

As for the gain due to the natural cooling of the modules, it can be stated that for the analyzed configurations, a gain of more than 5% can be obtained for Anapo Dam in Italy and greater than 4% for Aar in Germany.

If the overall gain due to bifaciality tracking and cooling is considered, the following gains are obtained for the two locations Anapo and Aar respectively: 16.9% and 14.4% for Horizontal E-W system; 27.6% and 23.3% for Horizontal N–S system; 31.3% 27.8% for One Axis Vertical system; 47.4% and 42.5% for Dual axis system.

Evaluation of Reference Evapotranspiration Estimation Methods for the Assessment of Hydrological Impacts of Photovoltaic Power Plants in Mediterranean Climates

Large-scale photovoltaic (PV) power plants may affect the hydrological cycle in all its components. Among the various components, evapotranspiration is one of the most important. As a preliminary step for assessing the impacts of PV plants on evapotranspiration, in this study, we performed an evaluation study of methods for estimating reference evapotranspiration (ETo). FAO and ASCE recommend the Penman–Monteith (PM) method for the estimation of ETo when the data for all involved variables are available. However, this is often not the case, and different empirical methods to estimate ETo, requiring mainly temperature data, need to be used. This study aimed at assessing the performance of different temperature- and radiation-based empirical ETo estimation methods against the standardized PM ETo method in an experimental photovoltaic power plant in Piazza Armerina, Sicily, Italy, where a meteorological station and a set of sensors for soil moisture were installed. The meteorological data were obtained from the Lab from July 2019 to end of January 2022. By taking the ETo estimations from the PM method as a benchmark, the study assessed the performance of various empirical methods. In particular, the following methods were considered: Hargreaves and Samani (HS), Baier and Robertson (BR), Priestley and Taylor (PT), Makkink (MKK), Turc (TUR), Thornthwaite (THN), Blaney and Criddle (BG), Ritchie (RT), and Jensen and Haise (JH) methods, using several performance metrics. The result showed that the PT is the best method, with a Nash–Sutcliffe efficiency (NSE) of 0.91. The second method in order of performance is HS, which, however, performs significantly worse than PT (NSE = 0.51); nevertheless, this is the best among methods using only temperature data. BG, TUR, and THN underestimate ETo, while MKK, BG, RT, and JH showed overestimation of ETo against the PM ETo estimation method. The PT and HS methods are thus the most reliable in the studied site.

Site Selection of Offshore Solar Farm Deployment in the Aegean Sea, Greece

Offshore solar energy presents a new opportunity for low-carbon energy transition. In this research, we identify and rank suitable Offshore Solar Farm (OSF) sites in the Aegean Sea, Greece, considering various constraints and assessment criteria. The methodology includes two distinct phases. In the first phase, Geographic Information Systems (GIS) are used to spatially depict both incompatible and compatible marine areas for OSF deployment, while in the second phase, two models based on different combinations of multi-criteria decision-making methods are deployed to hierarchically rank the eligible areas for OSF deployment. The first model (Objective Model—OM) attributes weights to assessment criteria using an entropy-based weight method, while the second model (Subjective Model—SM) utilizes the pairwise comparison of the Analytical Hierarchy Process (AHP) method. Both models use TOPSIS (Technique for Order of Preference by Similarity to Ideal Solution) to prioritize the suitable OSF sites. The results indicate the existence of nine suitable OSF marine areas in the Greek marine environment (total surface area of 17.25 km2) and a different ranking of these sites depending upon the deployed model (OM or SM). The present approach provides useful guidelines for OSF site selection in Greece as well as in other countries.

Ecohydrological effects of photovoltaic solar farms on soil microclimates and moisture regimes in arid Northwest China: A modeling study

Photovoltaic technology plays an important role in the sustainable development of clean energy, and arid areas are particularly ideal locations to build large-scale solar farms, all over the world. Modifications to the energy balance and water availability through the installation of large-scale solar farms, however, fundamentally affect the energy budget, water, and biogeochemical cycles. In-situ field observations, though, fail to draw definitive conclusions on how photovoltaic panels (PVs) affect the ambient environment, or how microclimates and soil moisture evolve under the long-term, continuous, cumulative influence of PVs. Here, we designed a synthetic model, integrating processes of energy budget and water cycle, to quantify the ecohydrological effects of PVs on soil microclimate and moisture regimes at different locations (zones) near individual PVs. Simulations run with a stochastically generated 100-year climate time series were examined to capture the evolutionary trends of soil microclimate and soil moisture. The results indicate that soil moisture content was increased by 59.8% to 113.6% in the Middle and Front zones, and soil temperature was decreased by 1.47 to 1.66 °C in all the sheltered zones, mainly because there was 5- 7 times more available water and ~27% less available radiation there, compared with the control zone. On the other hand, if the ground clearance of the PVs is too low, turbulence beneath hot PVs will have a significant influence on not only soil temperature but also soil moisture content. The innovative contribution of this study lies in reinforcing existing theoretical patterns for the development of soil microclimate and moisture dynamics influenced by PVs, and can be used to provide reliable insights into the hydrological and biogeochemical processes on Earth and the sustainable management of large-scale solar farms in arid ecosystems.

FPV for Sustainable Electricity Generation in a Large European City

There is a huge interest worldwide related to continuously increasing the use of renewable energy sources (RES) for electricity generation. Romania, at this moment, even though it has to attain a share of 30.7% of RES from total energy consumption by 2030, does not have any major investment project of this kind in the near future. Photovoltaic (PV) is one of the most promising technologies, with decreasing prices for PV panels but with the disadvantage of large, needed surfaces. This study presents a solution to install PV panels where there is a need for electricity, in a large city, by using the surface of a reservoir. “Lacul Morii” Reservoir in Bucharest is the choice for the case study. The insolation and the possibility to install floating PV, as well as electricity generation, benefits for water quality and carbon dioxide (CO2) emissions reduction are assessed, and even the installation of charging stations for electric bikes and cars. The results are very promising, and the main conclusion is that, after its realization, the floating photovoltaic (FPV) plant on “Lacul Morii” Reservoir will be a source of clean electricity and a demonstration project on how to benefit from solar energy to produce electricity in large cities where there are reservoirs.

Current site planning of medium to large solar power systems accelerates the loss of the remaining semi-natural and agricultural habitats

The global transition to renewable energy sources has accelerated to mitigate the effects of global climate change. Sudden increases in solar power facilities have caused the physical destruction of wildlife habitats, thereby resulting in the decline of biodiversity and ecosystem functions. However, previous assessments have been based on the environmental impact of large solar photovoltaics (PVs). The impact of medium-sized PV facilities (0.5-10 MW), which can alter small habitat patches through the accumulation of installations has not been assessed. Here, we quantified the amount of habitat loss directly related to the construction of PV facilities with different size classes and estimated their siting attributes using construction patterns in Japan and South Korea. We identified that a comparable amount of natural and semi-natural habitats were lost due to the recent installation of medium solar facilities (approximately 66.36 and 85.73% of the overall loss in Japan and South Korea, respectively). Compared to large solar PVs, medium PV installations resulted in a higher area loss of semi-natural habitats, including secondary/planted forests, secondary/artificial grasslands, and agricultural lands. The siting attributes of medium and large solar PV facilities indicated a preference for cost-based site selection rather than prioritizing habitat protection for biodiversity conservation. Moreover, even conservation areas were developed when economic and topological conditions were suitable for energy production. Our simulations indicate that increasing the construction of PVs in urban areas could help reduce the loss of natural and semi-natural habitats. To improve the renewable energy share while mitigating the impacts on biodiversity, our results stress the need for a proactive assessment to enforce sustainable site-selection criteria for solar PVs in renewable energy initiatives. The revised criteria should consider the cumulative impacts of varied size classes of solar power facilities, including medium PVs, and the diverse aspects of the ecological value of natural habitats.

In-Situ Water Quality Observations under a Large-Scale Floating Solar Farm Using Sensors and Underwater Drones

The rapid implementation of large scale floating solar panels has consequences to water quality and local ecosystems. Environmental impacts depend on the dimensions, design and proportions of the system in relation to the size of the surface water, as well as the characteristics of the water system (currents, tidal effects) and climatic conditions. There is often no time (and budget) for thorough research into these effects on ecology and water quality. A few studies have addressed the potential impacts of floating solar panels, but often rely on models without validation with in situ data. In this work, water quality sensors continuously monitored key water quality parameters at two different locations: (i) underneath a floating solar park; (ii) at a reference location positioned in open water. An underwater drone was used to obtain vertical profiles of water quality and to collect underwater images. The results showed little differences in the measured key water quality parameters below the solar panels. The temperature at the upper layers of water was lower under the solar panels, and there were less detected temperature fluctuations. A biofouling layer on the floating structure was visible in the underwater images a few months after the construction of the park.

Benefits and Critical Knowledge Gaps in Determining the Role of Floating Photovoltaics in the Energy-Water-Food Nexus

Floating solar photovoltaic (FPV) systems have become an increasingly attractive application of photovoltaics (PV) because of land-use constraints, the cost of land and site preparation, and the perceived energy and environmental co-benefits. Despite the increasing interest in FPV systems, a robust validation of their suggested co-benefits and impacts on the nexus of energy, water, and food (EWF) systems is lacking. This information gap makes it challenging for decision makers to justify its adoption—potentially suppressing FPV deployment. To address this gap and to help de-risk this PV deployment opportunity, we (1) review the suggested co-benefits of FPV systems with a focus on the impacts that could alleviate pressures on EWF systems and (2) identify areas where further research is needed to reduce uncertainty around FPV system performance. Our review reveals that EWF nexus-relevant co-benefits, such as improved panel efficiency and reduced land usage, are corroborated in the literature, whereas others, such as water quality impacts, lack empirical evidence. Our findings indicate that further research is needed to quantify the water-related and broader economic, environmental, social, sustainability, justice, and resilience co-benefits and impacts of FPV systems.

Study on the Impact of Industrial Agglomeration on Ecological Sustainable Development in Southwest China

Southwest China is a fragile terrestrial ecosystem restricted by its geological background, which leads to a contradiction between its industrial economic development and the ecological environment. In this study, to explore the influence and mechanisms of the three industrial agglomeration modes, namely, specialization, related diversification, and unrelated diversification, on the eco-efficiency of the region, linear and nonlinear regression models were applied to the data of five Southwest provinces from 2006 to 2018. Specialization agglomeration had a significant negative impact on the eco-efficiency of four provinces outside Tibet in Southwest China. With the decrease of industrial specialization, their eco-efficiency improved. The effects of related diversification agglomeration on the ecological efficiency of four provinces outside Tibet in Southwest China showed a “U” curve. The degree of industrial diversification in these provinces exceeded the critical value of 1.46, and the effect on eco-efficiency was shown. The unrelated diversification agglomeration had a negative effect on the ecological efficiency of the four provinces outside Tibet in Southwest China. The degree of industrial-unrelated diversification in Guizhou Province increased slightly, which was not conducive to the improvement of local eco-efficiency. Additionally, it decreased significantly in other provinces, which caused the improvement of local eco-efficiency. The conclusion provides a theoretical basis for industrial green transformation path selection and related policy formulation in Southwest China.

Solar Energy Potential in the Yangtze River Delta Region—A GIS-Based Assessment

Decarbonization of electrical power generation is an essential necessity in the reduction of carbon emissions, mitigating climate change and attaining sustainable development. Solar energy as a substitution for fossil fuel-based energy sources has the potential to aid in realizing this sustainable future. This research performs a geographic information systems (GIS)-based assessment of the solar energy potential in the Yangtze River Delta region (YRDR) of China using high-resolution solar radiation data combined with geographical, social, environmental and cultural constraints data. The solar energy potential is evaluated from the geographical and technical perspective, and the results reveal that the YRDR is endowed with rich solar energy resources, with the geographical potential in the suitable areas ranging from 1446 kWh/m2 to 1658 kWh/m2. It is also estimated that the maximum solar capacity potential could be up to 4140.5 GW, illustrating the high potential available for future capacity development in this region. Realizing this significant potential as an alternative for fossil fuel-based electricity generation would result in a substantial mitigation of CO2 emissions in this region, where air pollution is severe. Potential evaluations found that Jiangsu and Anhui provinces provide the most optimal areas for the development of solar photovoltaics (PV) installations, as they have the highest geographical and technological solar energy potential. Further, findings of the case study undertaken at a solar PV plant show disparities between actual generated power and technical solar potential, highlighting the significance of utilizing solar radiation data from local ground-based meteorological stations. This study provides policy makers and potential investors with information on solar energy potential in the Yangtze River Delta region that would contribute to solar power generation development.