Saving Hoover Dam by Majdi & Manaugh

Response to Judges’ Comments Comment 1 – More details on the type of floating panels that the authors are suggesting be used for this project. Response 1 – To provide more details on the proposed floating solar PV farm we have added text to the original description in the “What actions do you propose?” section and we have included (a) a photo of an installed floating solar PV farm in Kato City, Hyogo Prefecture, Japan and (b) a schematic diagram of the floating modules with specification provided by the French manufacturer Ciel & Terre. *** Comment 2 – Also, there is not enough discussion about how a floating PV solar farm would avoid obvious dangers (think storms, the technologies interacting with water, sea life, birds, people who are in the vicinity). Response 2 – In the additional description of the floating solar PV farm (see response to previous comment) we report that the connected floating modules are engineered to withstand extreme physical stress, including typhoon conditions with winds up to 118 mph. The floating modules are made of high-density polyethylene (HDPE). This material is 100% recyclable, UV and corrosion resistant, and drinking-water compliant. We expect the installation will include a security cordon and standard maritime traffic signage to alert and keep away nearby boat traffic. *** Comment 3 – I also think there is not enough discussion about the challenges that come with multi-state/federal involvement with projects of this magnitude. Response 3 – Multi-jurisdictional projects pose great challenges. However, states in the Western U.S. have made a tremendous amount of progress toward establishing a unified front in dealing with the impact of climate change. We have added text in the “Who will take these actions?” section to discuss how the Western Governors’ Association (WGA) is helping to create a cooperative environment for collective action to deal with critical issues in the Western U.S. Some of the WGA initiatives are: • Weather and climate risk • Energy and transmission • Forest health and wildfire • Clean, reliable water supply • Wildlife corridor and crucial habitat *** Comment 4 – A more detailed and practical proposal would also clarify the solution being presented in regards to the energy-water nexus. The principal issue is the economics. We do not see how this could possibly cost $1.2b. The value of the water saved and energy produced is very much less than that. Response 4 – We have revised the project cost estimate to $837 million. The original estimate included a 50% surcharge for work performed on water; similar surcharges are usually needed for off-shore installations. After consulting with experts, we came to realize that none of the specialized equipment or additional effort required for off-shore installations would be needed for deploying the floating solar PV farm on Lake Mead. The cost of a similar installation in Japan for a 92-MW solar PV plant is $290 million (2015). Extrapolating, without taking into account economies of scale, yields $879 million for a 279-MW solar PV plant. So, $837 million is a reasonable estimate. The final cost at implementation time is expected to be lower as PV panel costs keep going down and efficiency keeps going up. ***