Why Don’t We Have Floating Solar on DC’s Reservoirs?
By: 2022 DC Fellow Averie Thomas
Contributing Researchers: Katie Burke, Chuyan Cheng, and Kaly Moot
Note: Subject matter experts interviewed are kept anonymous, per their request
Installing floating solar on DC’s major reservoirs would be a symbolic and impactful climate victory in the nation’s capital.
It is hard to overstate the impending threat of climate change. With almost daily news reports of hurricanes, floods, dry rivers, species extinctions, and heat waves, it has become abundantly clear that swift action is needed to rapidly decarbonize our economy.
The DC region met its goal to cut 20% of greenhouse gases by 2020, but a recent report by the Metropolitan Washington Council of Governments signals that the hardest part of decarbonization lies ahead, as most of the “low-hanging fruit” has already been accomplished. One of DC’s ambitious goals is to increase renewable electricity to 100% by 2032.
One major challenge of expanding renewable energy is land use: wind and solar generation require around 10 times as much land per unit of power produced than coal- or natural gas-fired power plants. This land-intensiveness of renewables presents a real challenge to DC’s ambitious climate goals with land in DC already relatively scarce and expensive.
But, what if utility-scale renewables didn’t have to be on land? If DC is serious about its climate goals, its largest reservoirs should be used for floating solar generation. Not only could this bring a significant amount of clean energy to the city, but also it would be a symbolic victory to have this type of project in the nation’s capital.
Putting solar panels on water makes a lot of sense in DC. First, floating solar is more efficient: utility-scale solar farms usually require 5–10 acres of land per MW of solar power produced, while floating solar only requires 2 acres of land to produce the same amount of power. Second, floating solar frees up land for uses like agriculture and housing. In cities like DC, where land is already often too scarce and expensive for utility-scale projects, and where rooftop solar can be less economical and potentially subject to regulatory headwinds, floating solar presents an attractive alternative. Third, floating solar on reservoirs reduces unwanted evaporation and limits the growth of algae blooms that kill marine life and contaminate water quality.
While floating solar panels have been associated with higher up-front costs, operation and maintenance costs have been cheaper for floating solar due to lower land upkeep costs. And, since the cooling effect of the water makes the panels 5–15% more efficient, energy production and the subsequent revenue streams are thus improved. Overall, floating solar has been inching closer to price parity with land-based solar.
There are three major reservoirs in DC that are ideal for floating solar installations: the Dalecarlia Reservoir, the Georgetown Reservoir, and the McMillan Reservoir (photos of the Dalecarlia Reservoir below). Several subject matter experts suggested that the floating solar could be installed as standalone projects on each reservoir or they could be developed with adjacent plants that would add further capacity. The author and contributing researchers modeled floating solar installations at these three reservoirs. Our results show these three installations could add 40–55MW of clean electricity to DC, which currently only has about 161 MWs installed.
According to two subject matter experts and our own modeling in Helioscope, this project would have favorable economics (including NPVs ranging from $60–100 million), even before factoring in the IRA’s new tax credits. Additionally, DC has some of the most generous SRECs (solar renewable energy credits) in the country that would bring additional revenues to this project.
So, why hasn’t any developer started this project? These reservoirs are owned and operated by the Washington Aqueduct, a division of the U.S. Army Corps of Engineers (USACE), under the Baltimore Division. The Washington Aqueduct is tasked with producing drinking water for one million citizens in the DC and Arlington County area. Unfortunately, the mission of this USACE division does not include generating clean electricity, and the organization is not set up in a way where they could profit from energy sales. The lack of financial incentives, coupled with the fact that installed floating solar panels could complicate reservoir maintenance, makes it unlikely that Washington Aqueduct would independently allow these reservoirs to be developed for floating solar.
While Washington Aqueduct does not have the incentive to allow this project, its organization must comply with orders from USACE. If any USACE Baltimore Division leaders were passionate about decarbonization (like recently appointed Colonel Estee Pinchasin), or any USACE political appointees (like Assistant Secretary of the Army, Michael Connor) were looking for a project to support the Biden administration’s decarbonization goals, it is very likely that they could direct this project to happen.
One potential way to implement this project would be to have DC Water as the off-taker for the electricity. Most of Washington Aqueduct’s revenues already come from DC Water, so this arrangement could ease the payment mechanics of the project. Further, DC Water uses enormous amounts of energy to pump water throughout DC and has its own ambitious climate goals that it is attempting to meet. Finally, DC Water’s AAA credit rating suggests that they could be involved in the financing of the project, or give another investor confidence in offtake secured by a credit-worthy counterparty.
Getting serious about tackling climate change will mean that we must figure out ways to build out more clean energy. In a place like DC where land is scarce, putting solar on waterways represents an enormous and economically feasible opportunity to achieve clean energy goals on a larger scale without the usual slew of negative externalities. Hopefully, DC can find the political will to get it done.
