Power Innovation companions with the impartial nonprofit Aspen World Change Institute (AGCI) to supply local weather and vitality analysis updates. The analysis synopsis beneath comes from AGCI’s Tanya Petach. A full record of AGCI’s updates is out there on-line.
Aerial view of floating photovoltaic panels on a lake. Picture credit score: Photo voltaic AquaGrid
In arid river basins across the globe, substantial water provide is misplaced by evaporation. A current estimate of worldwide reservoir evaporative losses discovered that annual water quantity loss was equal to 70 % of all world municipal water withdrawals in 2010. Practically one-third of all reservoirs evaporative losses on the planet happen in Canada and the US. Evaporation charges in the US are particularly excessive, due partially to the truth that the 2 largest U.S. reservoirs (Lake Powell and Lake Mead) are situated within the sizzling, dry deserts of the Southwest. And evaporation doesn’t simply affect reservoirs—it additionally desiccates irrigation canals, ditches, and holding ponds.
Lake Powell and Lake Mead, each on the Colorado River, have skilled long-term drying developments for the reason that flip of the millennium. Resulting from a mix of extended drought, water overuse, and warming temperatures, these reservoirs misplaced 61 % of their full storage quantity from January 2000 to April 2023. Whereas this yr’s hefty Rocky Mountain snowpack helped alleviate the impacts of the final 23 years of drought, one good snow yr isn’t sufficient to bail the Colorado River out of long-term drought.
Lake Mead water elevation from 1970 to current. The vertical purple line represents the beginning of the Millennium Drought in 2000. Lake Mead reached peak capability in 1983; in August 2023, Lake Mead was 33 % full at 1,061 ft. Knowledge supply: Bureau of Reclamation.
As water availability decreases within the Colorado River Basin, water use is extra extremely scrutinized. Alongside municipal, agricultural, and industrial customers, evaporation is a stealth water shopper. The Southern Nevada Water Authority just lately estimated that roughly 12 % of the Colorado River’s whole annual circulate is misplaced to evaporation and different system components (e.g., infiltration into ditch banks). In a water-stressed basin the place the federal authorities pays billions of {dollars} for modest water financial savings, 12 % loss provides as much as plenty of water. At present, these losses aren’t effectively accounted for within the Decrease Colorado River, however some consultants are urging policymakers to just do that.
Whereas reservoir evaporation contributes to water shortage within the Colorado River and different arid river basins, water managers are starting to concentrate on mitigating evaporative losses. One strategy to attenuating this loss is to cowl reservoirs and irrigation ditches in shading supplies such because the 96 million “shade balls” that have been deployed in 2015 to shade Los Angeles Reservoir in California. In recent times, focus has shifted to shading reservoirs and irrigation infrastructure in dual-purpose supplies akin to photovoltaics, or PV. Pairing PV with water infrastructure has centered round two strategies: floating PV and PV-covered irrigation canals.
Floating photovoltaics contain the set up of photo voltaic panels on high of froth, buoys, and different constructions that float on the floor of reservoirs, lakes, and ponds. These programs have a tendency to supply vitality extra effectively than land-based PV, due largely to the cooler temperatures of PV over water our bodies than on land. Because of this, pairing PV with water infrastructure has gained momentum in current many years as a method to lower reservoir evaporation and improve renewable vitality manufacturing.
Floating photovoltaics are thriving in Asia, which hosts 97 % of worldwide put in floating PV, primarily in China, Japan, and Korea. This win-win know-how is attractive to reservoir operators, energy firms, and municipalities. Venture places embrace Alicante, Spain, the place seven % of a small irrigation reservoir was lined in floating PV to offset agricultural energy wants; the United Kingdom, the place six % of the Queen Elizabeth II reservoir was lined in floating PV for municipal energy technology; and Colorado, the place the city of Walden is utilizing floating PV to offset energy necessities for water remedy.
These vegetation are comparatively new, so vitality yields and water financial savings are far beneath their full world potential. Theoretically, masking 30 % of the 100,000 reservoirs across the globe with floating PV has the potential to yield 9,434 terawatt-hours yearly, in keeping with a Nature Sustainability article by Yubin Jin and colleagues revealed earlier this yr—the equal of roughly 40 % of world electrical energy use in 2021. Since reservoirs are sometimes situated close to communities and metropolitan areas, floating photovoltaics have the potential to supply giant portions of energy near vitality shoppers. This co-location technique can lower transportation and line losses, rising the general effectivity of the system. Jin and colleagues estimate that over 150 metropolitan areas may turn out to be self-sufficient with native floating PV vegetation. Globally, producing vitality with floating PV on reservoirs may probably save 106 cubic kilometers of water from evaporative losses annually, a quantity equal to nearly 25 % of annual family water use in the US.
The 2 main reservoirs within the Decrease Colorado River stay a part of this theoretical future yield. Neither Lake Powell nor Lake Mead has but tapped into floating PV to curb reservoir evaporation—although research counsel that 10 % protection of Lake Mead may yield sufficient water financial savings and energy manufacturing for Las Vegas and Reno mixed.
Whereas the sunny Southwest is gradual to undertake floating PV on reservoirs, there’s a wholesome urge for food for PV-covered irrigation canals. Impressed by a College of California, Merced examine by Brandi McKuin and colleagues that highlighted potential water financial savings and vitality manufacturing from PV-covered irrigation canals within the area, the Turlock Irrigation District in California’s Central Valley is poised to interrupt floor on a mission deploying PV over its irrigation canals this fall. The Turlock Irrigation mission is a partnership between the irrigation district, a non-public photo voltaic firm (Photo voltaic AquaGrid), the California Division of Water Sources, and a analysis group on the College of California, Merced. In the same vein, the Gila River Indian Neighborhood in central Arizona obtained funding this yr from the Bureau of Reclamation for water conservation infrastructure, together with PV-covered ditches and canals. And the urge for food for PV-covered irrigation infrastructure is way from sated. A letter to the Secretary of the Inside in July, 2023, from quite a lot of advocacy organizations, requested pressing motion to deploy extra photovoltaics over irrigation canals.
Rendering of future photovoltaic-covered canal within the Turlock Irrigation District, California. (Picture Supply: Photo voltaic AquaGrid)
Whereas the potential from floating PV on reservoirs and PV-covered canals is very large, the know-how stays comparatively unproven. Environmental issues embrace steel leaching, ecosystem impairment, and decreased gentle depth in aquatic ecosystems underneath the installations. Outcomes from a pilot examine on Oostvoornse Lake within the Netherlands present that floating photovoltaics scale back gentle depth by 70 to 100% underneath installations, with potential cascading impacts on lake ecosystems. But researchers word that conventional PV installations additionally trigger appreciable environmental impacts, and direct comparisons are advanced. Along with environmental dangers, floating photovoltaics have greater set up prices and lift extra upkeep issues than land-based photo voltaic.
Regardless of these challenges, pairing PV and water infrastructure has huge potential to assist re-stabilize water provides within the Colorado River and different drought-stricken areas across the planet. Within the arid Southwest, intensified scrutiny on evaporative losses, requests for elevated federal curiosity for paired water infrastructure-PV programs, and daring exemplar tasks just like the PV-covered canal programs within the Turlock Irrigation District and Gila River Indian Neighborhood are ushering in a brand new strategy to water administration, with huge potential for enlargement. As reservoir evaporation continues to squander giant portions of water in arid areas worldwide, it’s time to maintain the momentum shifting ahead towards next-generation sustainable options on the water-energy nexus.