Solution
The water district selected 1898 & Co., a part of Burns & McDonnell, to study the options and make recommendations. Our renewable energy development consultants collaborated with water and environmental specialists inside Burns & McDonnell to evaluate the costs and possibilities thoroughly.
The team began by examining the feasibility of installing floating solar, an application that involves mounting PV panels on buoyant structures that float on calm waters. Although it is less common than ground-mounted solar, it is gaining traction as an option. We found that the reservoir could support a decent amount of solar production, and the cost would not be much higher than putting in ground-mounted panels. We calculated the reservoir could support up to 73.3 MWdc of floating solar capacity.
Even more significant, the study found that the panels could reduce water evaporation by a fairly substantial amount. Evaporation reduction from a 10-MW floating array was estimated to save up to 47 acre-feet of water annually. These savings could serve as a counterbalance to the cost of installing the system.
The green hydrogen initiative was found to be not feasible. The overall cost for an electrolyzer and a water treatment plant to prepare the reservoir water would be too high and would require too long of a payback period. It also would defeat the purpose of saving water through evaporation mitigation to use water for green hydrogen production.
One of the most significant factors in the team’s evaluation was whether and where the floating PV system would interconnect with the grid. The water district had two options, both entailing additional expenses that would be likely to impact feasibility negatively:
- If it interconnected with the local co-operative utility, the floating PV system would need to stay under 10 MWac because of the co-op’s capacity limitations. Installation and surrounding system upgrades would increase costs.
- The water district could pursue a system as large as 20 MW by interconnecting with a nearby transmission provider through a Small Generator Interconnection Agreement, but this would require additional studies and upgrades, impacting the economics of the arrangement.
The local co-op requires any project over 25 kW that is looking to interconnect to the grid to either use all of the power it generates or to sell it all back. With relatively little power demand from the water district, the floating PV system would generate more power than the district could offset. Electricity payback rates in the area are too low to sell back excess capacity feasibly.
Results
The study was completed less than four months after it was awarded. The final report summarized our team’s findings. These included cost estimates, schedules, and calculations for return on investment and net present values.
Because of the specific limitations on the size of the system that could be installed, as well as options for managing excess power, the economic feasibility of the project was limited. However, it also identified strong potential for other floating solar projects. The similar cost of installation compared to ground-based solar — after combining with the significant value of reduced evaporation losses — presents water utilities with fresh opportunities to drive cost savings and potentially generate revenues.
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