Impact on water evaporation
One of FPV’s economic benefits is its potential to reduce water evaporation.[30] Solar panels reduce the amount of sunlight reaching the water and block wind from sweeping the water surface.[44]
This double effect reduces the amount of evaporated water, important for warmer climates with water availability issues, potentially worsening because of climate change[30].
Several methods used to calculate evaporation reduction due to shading and coverage are also used to measure evaporation reduction due to floating coverage. These include evaporation pan, the water budget method, and empirical formulas like the Penman method.[46][47][48]
Studies on evaporation reduction
A study by Abd-Elhamid et al[45] examines strategies to mitigate evaporation from Lake Nasser, a crucial water source in Egypt fed by the Nile. The study used annual evaporation rates calculated by the bulk aerodynamic approach using meteorological data from 2009 to 2020.
Results showed considerable loss of water, averaging 12.00 billion m3/year, or 22% of Egypt's share of the Nile. This was compounded by the Great Renaissance Dam's impact from Ethiopia. The study suggested using FPV to cover shallow portions of the lake, saving a significant amount of water and producing renewable electricity.
The best water savings are achieved by covering shallow depths up to 1.0m, saving 1.9 billion m3 annually. FPV is in line with Egypt's environmental objectives, offering sustainable initiatives and renewable energy.
In Jordan, Abdelal et al[46] installed an experimental FPV system with 100% coverage in a semi-arid region. They found FPV reduced evapotranspiration by about 60% compared to an uncovered setup in the same location. Improvements in nitrate and chlorophyll concentrations were also observed.
Bontempo Scavo et al[47] developed numerical evaporative models (EVMfree and EVMFPV) to analyze the impact of FPV plants on water basin evaporation. Comparison with existing literature models and experimental measurements showed FPV covering 30% of the basin area resulted in a 49% reduction of evaporation.
And in Brazil, Lopes et al[49] examined regions with semi-arid climates. They concluded that FPV coverage scenarios of 21.2%, 50%, and 70% could reduce evaporation from reservoirs by 15.3%, 37%, and 55.2% respectively. This is important for increasing cities’ resilience in this type of climate, especially during periods of drought.