The pilot project will validate the commercial viability of storing renewable energy in liquid hydroxide salts. Sulzer is a member of the project consortium investing DKK 24.7m (£2.85m) in the technology, which has the potential to save 32,000 tonnes of CO2 emissions annually for each 1 GWh of capacity.
Power generation from renewable sources is transient, with varying sunlight and wind speeds resulting in fluctuating supply. Shortfalls in renewable power output to the grid must often be met with thermal powerplants, which are carbon intensive. MOSS aims to solve this by storing renewable energy for up to two weeks in molten hydroxide salts at temperatures of 700°C, which can be used to create steam and drive a turbine. This ensures that during periods of high renewable power generation, excess energy can be stored and deployed when output from windfarms and solar plants falls or electricity demand spikes.
Arrigo Beretta, Vice President of Global Technology at Sulzer, said: “Working with our consortium partners, we are actively demonstrating how our pump technology can contribute to reducing carbon emissions.”
The solution will pump 700°C molten salt from a hot storage tank to a heat exchanger that generates steam. The pilot plant will offer a charge/discharge capacity of 200 kW, but is designed for scalability, with the end goal to build a commercial plant with storage for 1 GWh of power. A facility with this capacity is projected by the consortium to deliver a CO2 saving of 32’000 tonnes annually.
Benoît Martin, Advance Engineering Manager & Pump Application Technical Advisor at Sulzer, said: “Due to the lower flow, only a few meters per hour, at the pilot plant, we specified our VNY vertical mixed-flow molten salt pump. While the hydraulic design is mostly standard, a custom design for the 700°C temperature, upgraded shaft seals and a special material are incorporated.
“At higher temperatures, salt becomes more corrosive, but building a pump to operate at 700°C isn’t a big jump for us. We’ve been providing molten salt pumps since the 1950s, and our work for Generation 3 CSP plants means we can accommodate salts at this temperature. We’re familiar with ensuring proper clearances, good temperature management, right materials and robust performance. Despite the extreme conditions, this is a relatively normal application for us.”
Consortium partner Hyme Energy provided its own corrosion protection system and selected the materials required for the pump. Sulzer had previous experience working with these materials, which expedited the project.
According to Sulzer, the pump offers scalability. If higher flow rates are required, the VEY pump offers the same hydraulics and potential specialisations, so any verified specification on the VNY pump can be transferred directly to the larger model when the time comes to expand the project.
The pilot plant is under construction in the town of Esbjerg. As well as support from organisations in the consortium, including Aalborg University, Alfa Laval Aalborg, DIN Forsyning, Energy Cluster Denmark, Kirt X Thomsen, Seaborg – the project is partly funded by the Danish Energy Agency’s Energy Technology Development and Demonstration Program (EUDP). Completion is expected by 2024, with a successful pilot hopefully leading to a fully-fledged commercial operation.