Rapid, global development of renewable energy, especially solar energy, is increasingly playing a pivotal role in mitigating climate change and meeting both national and global decarbonization goals. While transitioning from fossil fuels to renewable energy is necessary to address climate change and adhere to international climate accords, solar energy can have impacts—both positive and negative—on the environment and require large amounts of land. As such, novel solar energy applications, such as floating solar energy photovoltaics (FPV), have been gaining traction globally as the technology increases accessibility to solar energy to land-limited populations and also may provide non-energy benefits to the host water body. However, FPV technology is still relatively new, with little understanding of the technology on environmental and hydrological conditions. Additionally, there is a dearth of understanding towards how FPV installations relate to ground-mounted PV technologies in terms of performance and land use. The main goal of this dissertation is ultimately to explore the land use implications of solar energy technologies and, more specifically, investigate the environmental and hydrological implications of floating solar photovoltaics. While this dissertation mainly focuses on the hydrological, environmental, and land-use impacts associated with floating solar photovoltaic energy installations, it also evaluates the impact of ground-mounted solar energy-land-use interactions to form a comprehensive understanding of the interplay between solar energy and the environment. As such, this research consists of four portions:
1. Using a systematic literature review on solar energy-land use metrics to propose a standardized suite of metrics for communicating solar energy-land interactions,
2. Evaluating the land sparing benefits of floating solar energy installations and propose metrics for communicating the spatial footprint of FPVs,
3. Investigating the impacts of FPV on continuous water temperature and dissolved oxygen dynamics at multiple locations across the United States,
4. Investigating the impacts of FPV on major water quality parameters and algae growth dynamics at multiple FPV locations across unique climatic zones.
In the first chapter, a systematic literature review is conducted that evaluates the current state of solar energy-land use metrics across disciplines. Specifically, this chapter focuses on the disconnect between the metric term and associated units across studies and how this disconnect leads to the inaccurate dissemination of findings across studies. This review quantifies metric term and unit usage and uses these findings to propose standardized metrics in three distinct categories: capacity-based, generation-based, and population-based solar energy-land use metrics. By doing so, the goal of this chapter is to minimize the use of an unnecessary number of unique metrics to define identical parameters and, ultimately, aid in the accurate dissemination of findings across disciplines.
In the second chapter, an evaluation of the land sparing aspects of floating solar installations along with quantifying the water surface use efficiency and water surface transformation of four FPV installations across the United States is conducted. Metrics for both generation-based and capacity-based surface use by FPV installations is proposed following similar naming mechanisms identified in chapter 1 for ground-mounted installations. The two metrics are then calculated for the four sites in this study and compared to ground-mounted installations on a per-unit of PV area basis. The results of this study indicate that the four FPVs in this study are more efficient on a per m2 of installation basis in both generation and capacity. While these findings demonstrate the technical benefits of FPVs, the chapter also provides a path for future comparative studies between FPV and other renewable energy technologies.
In chapter three, a one-year field study is conducted that continuously monitors water temperature and dissolved oxygen at three FPV locations across the United States. The study compares water column temperature at multiple depths and near-surface dissolved oxygen below the FPV compared to open water locations of the same host water body. The results of this study indicate that high-coverage FPV installations compared to the water surface area can have significantly lower temperatures beneath the FPV installation than in the open water body. Dissolved oxygen is also found to be less beneath all FPV installations. Additionally, this study identifies ways in which FPVs shift the temperature range of the water column on a diel basis and shifts warming patterns towards later in the day. These findings can better inform future modeling efforts of FPV installations, specifically on shallow bodies of water, and help elucidate the impact FPV could have at helping mitigate the impacts of warming urban waterways due to climate change and urbanization.
In the final chapter, a seasonal spot sampling field campaign is conducted that evaluates water quality parameters and algal growth dynamics below FPV installations compared to open water portions of the host water body. Specifically, temperature, dissolved oxygen, pH, phycocyanin, chlorophyll-a, and conductivity measurements were collected via handheld sonde over the course of four seasons from 2021-2022. Each season consisted of four days of twice-daily campaigns, one in the morning and one in the late afternoon. The findings from this study indicate that FPVs may not have a significant impact on algal growth within the host water body and further validate findings from chapter three on dissolved oxygen concentrations being lower beneath the FPV. The findings of this chapter demonstrate the need for further, continuous monitoring of water quality parameters at FPV installations and greater access to pre-FPV construction data in order to fully grasp trends that may be occurring as a response to FPV deployments.
