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

Alexander E Cagle,Alona Armstrong,Giles Exley,John Sherwin,Steven M Grodsky,Jordan Macknick,Rebecca R Hernandez

doi:10.3390/su12198154

Abstract

Floating photovoltaic solar energy installations (FPVs) represent a new type of water surface use, potentially sparing land needed for agriculture and conservation. However, standardized metrics for the land sparing and resource use efficiencies of FPVs are absent. These metrics are critical to understanding the environmental and ecological impacts that FPVs may potentially exhibit. Here, we compared techno-hydrological and spatial attributes of four FPVs spanning different climatic regimes. Next, we defined and quantified the land sparing and water surface use efficiency (WSUE) of each FPV. Lastly, we coined and calculated the water surface transformation (WST) using generation data at the world’s first FPV (Far Niente Winery, California). The four FPVs spare 59,555 m2 of land and have a mean land sparing ratio of 2.7:1 m2 compared to ground-mounted PVs. Mean direct and total capacity-based WSUE is 94.5 ± 20.1 SD Wm−2 and 35.2 ± 27.4 SD Wm−2, respectively. Direct and total generation-based WST at Far Niente is 9.3 and 13.4 m2 MWh−1 yr−1, respectively; 2.3 times less area than ground-mounted utility-scale PVs. Our results reveal diverse techno-hydrological and spatial attributes of FPVs, the capacity of FPVs to spare land, and the utility of WSUE and WST metrics.

Highlights

Floating solar photovoltaic installations (FPVs) represent a new type of water surface use, with unique characteristics and water surface impacts relative to other types of water surface uses
The locations of the four FPVs investigated in this study demonstrate a wide range of operational climates and environments (Figure 1)
We found that the mean direct water surface use efficiency (WSUE) of FPVs is 94.5 ± 20.1 W m−2 and the greatest WSUE we observed at the two most recently constructed FPVs (Windsor, CA, and Walden, CO), suggesting that improvements in direct WSUE via design may be increasing

Summary

Introduction

Floating solar photovoltaic installations (FPVs) represent a new type of water surface use, with unique characteristics and water surface impacts relative to other types of water surface uses. Global deployment of FPVs has increased over the past decade, due, in part, to increased demand for renewable energy generation and beneficial land sparing outcomes associated with locating solar photovoltaic (PV) atop pre-existing water bodies [1,2]. Deploying solar energy over pre-existing water bodies may spare land for other purposes, such as agriculture and conservation. The estimated potential for electrical generation from domestic FPVs on constructed (i.e., human-made) water bodies within the United States (US) is over 10% of total US energy demand [4]

Objectives

Methods

Results

Discussion

Conclusion