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Technology

The Green Power Plant is an offshore storage facility located at 20-40 m sea depth. The energy is stored as pumped hydro storage, where the lower reservoir is constructed from prefabricated wall elements and the upper reservoir is the surrounding sea. The prefabricated wall elements are constructed by serial production and ferried from the onshore manufacturing yard to the installation site and installed in an innovative process, reducing both installation time and costs.

Water is pumped from inside the reservoir to the surrounding sea to store energy. When energy is needed, valves control the flow of water back into the lower reservoir, thereby spinning the pump-turbines to generate electricity. The reaction time of the pumped hydro storage is very fast and the facility can provide both primary and secondary frequency control as well as regulating power.
Pumped storage hydropower is generally regarded as the most efficient way of storing energy at large scale, with a proven roundtrip efficiency of 80%. The Green Power Plant offers pumped hydro storage integrated with renewable energy production, thereby removing the geographical constraint and the large impact on local environment of conventional pumped hydro power.

Schematic illustration of a Green Power Plant


The GPP has a very unique scalability as the costs scale linearly with the diameter whereas the storage capacity scales with the diameter squared - if the reservoir diameter is doubled, the wall costs increase with a factor two, whereas the storage capacity increases with a factor four. This means that the bigger the GPP, the cheaper the unit price of the energy storage.

It is possible to integrate both wind power, wave power and solar power with the offshore pumped storage reservoir. This results in several synergetic effects, including an larger and more stable production of renewable energy.

Summing up, the Green Power Plant has several unique features, making it perfectly suited for the future power system:
  • Unique scalability the larger the reservoir, the lower the unit cost of storage
  • Integration with renewable offering multiple synergies and cost efficiency
  • Multiple advantages for the power system
    • Ancillary services
    • Regulating power
    • Peak power
    • Reduced backup generation capacity
    • Facilitate higher share of intermittent renewable energy
  • Fast deployment
    • Mature technologies
    • No NIMBY effect
    • Prefabrication of wall elements
    • Simple and fast installation, even on a sloping seabed


Seahorn Energy Aps Vesterbrogade 90 4. sal, 1620 Kbh. V. jms@seahorn.dk