Floating PV for Saving Water

By Lotus Shaheen.

Climate change is rapidly influencing all areas of our lives. From aggregating forest wildfires in the United States to the verified recent decrease in the Arctic sea ice, the hazards imposed upon our ecosystem are grave and alarming. Floating solar power plants offer an innovative energy solution that not only caters our energy demands but also grants numerous environmental benefits, one of which is saving valuable water resources.

Comparative satellite images of Lake Chad in the year 1972 and 2007. 50% of shrinkage has been attributed to climate change (source)

Evaporation of large water bodies such as oceans, natural and artificial lakes is inevitable. In fact, it is an essential part of our planet’s water cycle. That said, too much evaporation is a serious environmental danger. Over the past two decades, Earth has witnessed the driest and hottest summer seasons since the early twentieth century. A research paper by Yale School of Forestry and Environmental Studies suggests that evaporation of large water masses will increase by 16 percent by the end of the century, which can consequently alter regional climate trends and cause increased precipitation. A simple analogy to grasp the consequences of such abnormality is to imagine the Earth’s water cycle as a dysfunctional water pump that instead of transporting water from high to low pressure, it does exactly the opposite. In other words, rain is transported from drier to more humid regions.

Temperature and precipitation over the last two decades indicate that the hottest and the driest summers since 1895 occured in the last 20 years (source)

Natural water masses, such as oceans, are less prone to over evaporation compared to artificial lakes. This is due to their typically turbulent air-sea interface, which may hinder the evaporation process. On the other hand, artificial lakes are directly at risk of drying out in the case of extreme weather conditions due to their increased water surface area and its stagnancy. A geo-referenced database by the Food and Agriculture Organisation illustrates the rise in accumulated water evaporation to about 350 km3 as of the year 2015. Although this analysis is intended as a rough estimation only built upon the available collected data, it reflects how water loss in dam lakes has increased drastically since 1950.

Cumulative global dam evaporation in km3 from 1900 to 2015 as modeled in AQUASTAT (source)

Floating PV Technologies

Floating PV technologies provide elimination measures against evaporation of artificial lakes. Acting as a shield, the offshore PV platforms can protect the water body against direct sunlight. Moreover, given their stable nature, dam lakes offer favorable installation conditions for the emerging technology. In an experimental study set in northern Chile, floating PV reduced water evaporation by 90% compared to an uncovered condition, all while yielding up to 68 Wp/m2 equivalent of electric power. The remarkable water savings have also been noted as a possible solution to save the US’s great lakes from drying out.

To sum up, floating PV demonstrates a great potential to save our planet’s water cycle from climate change driven disturbances.

[1] National Geographic, Environment. See how a warmer world primed California for large fires. Published November 15, 2018. URL: https://www.nationalgeographic.com/environment/2018/11/climate-change-california-wildfire/

[2] IPCC. 2018. Special Report: Global Warming of 1.5°C, Chapter 00: Summary for Policy Makers.. URL: https://www.ipcc.ch/sr15/chapter/summary-for-policy-makers/b/

[3] Our World, United Nations University (UNU). Sucking Dry an African Giant. By Mark Notaras and Obijiofor Aginam. Published online March 23, 2009. URL: https://ourworld.unu.edu/en/sucking-dry-an-african-giant

[4] EU WATCH (Water and Global Change) project – Centre for Ecology and Hydrology, Wallingford, UK. Evaporation. URL: http://www.waterandclimatechange.eu/evaporation

[5] Yale School of Forestry & Environmental Studies. Climate change will boost global lake evaporation – with ‘extreme’ consequences: Evaporation will rise by 16 percent by end of century. Science Daily, 2 May 2018.  URL: https://www.sciencedaily.com/releases/2018/05/180502115951.htm

[6] Woods Hole Oceanographic Institution. Calculating Evaporation from the Ocean: Scientists strive to unravel a mix of dynamic factors. Oceanus Magazine. By Lonny Lippsett, published online October 12, 2012. URL: http://www.whoi.edu/oceanus/feature/evaporation

[7] FAO. 2016. AQUASTAT website. Food and Agriculture Organization of the United Nations (FAO). URL: http://www.fao.org/nr/water/aquastat/dams/

[8] M.E. Taboada et al., Solar water heating system and photovoltaic floating cover to reduce evaporation: Experimental results and modeling. Renewable Energy, V.105, pp 601-615, 2017. https://doi.org/10.1016/j.renene.2016.12.094

[9] Alina Wang. Floating solar is a win-win energy solution for drought-stricken US lakes. Blog post published on January 4, 2019. URL: https://www.linkedin.com/pulse/floating-solar-win-win-energy-solution-us-lakes-alina-wang/

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