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Subsea pumped storage tech secures funding from US, German governments

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    Comment box Scope: information, personal perspective Tone: neutral, intrigued Opinion: not really Sarcasm/humor: none Pumped hydro storage is a way to store potential energy using the Earth's...
    Comment box
    • Scope: information, personal perspective
    • Tone: neutral, intrigued
    • Opinion: not really
    • Sarcasm/humor: none

    Pumped hydro storage is a way to store potential energy using the Earth's gravity and a couple bodies of water. When you have excess energy, pump water high up; when you need energy, use gravity to drop the water to a lower elevation and spin a turbine, like a typical hydro plant. This is a simple and fairly cheap alternative to electrical batteries.

    Normally pumped hydro storage is accomplished in mountainous areas on land, but this novel approach does it underwater.

    Deep sea pumped hydro storage is a novel approach towards the realization of an offshore pumped hydro energy storage system (PHES), which uses the pressure in deep water to store energy in hollow concrete spheres. The spheres are installed at the bottom of the sea in water depths of 600 m to 800 m.

    An empty sphere corresponds to a fully charged storage unit. Opening the controllable valve enables water to flow through the technical unit into the sphere. The inflowing water drives a turbine and a generator that feeds electricity into the grid. This represents the discharging phase of the storage system. Recharging is achieved by pumping the water out of the sphere against the surrounding water pressure using energy from the grid.

    The techno-economic assessment showed that the StEnSea system is cost competitive with conventional pumped hydro energy storage (PHES). While the exploitation of PHES often raises environmental issues due to land demand and its impact on the water regime, there are no major restrictions expected for the StEnSea technology. Another advantage is the modular set up that is achieved by combining several StEnSea units to a plant. This increases the flexibility of the plant and therefore the range of possible applications.

    The news here is that the technology has gotten funding from governments. It seems like it is pretty feasible if it's actually cost-competitive with pumped hydro storage.

    US-based Sperra has been awarded a $4 million grant by the from the US Department of Energy Water Power technologies Office to advance innovation in pumped storage hydropower technologies.

    The US funding unlocks a parallel grant on the opposite side of the Atlantic from the German Ministry for Economic Affairs and Climate Action (BMWK) amounting to $3.7 million (EUR 3.4 million).

    The collaborative work aims to develop a low-cost, long-duration, subsea energy storage technology that supports electrical grid decarbonization. The partners are aiming for the system off Long Beach near Los Angeles to be put into operation by the end of 2026 at the latest.

    According to Sperra, the US is the largest market for marine-pumped hydroelectric storage with over 7.5 TW/75 TWh of net technical potential in the Atlantic, Pacific and Gulf of Mexico, which is more than two times the US closed-loop pumped storage hydropower technical potential onshore (3.5 TW and 3,500 TWh).

    For reference, the US currently has something like 1.1 TW of nameplate electricity generating capacity. As we electrify further, that will increase, but we don't need as much as you think. We do not need that much battery storage, but we will need a lot. As long as this solution is cost-competitive, it seems like there is plenty of potential.

    I legitimately had not considered using pumped storage entirely underwater. If it works, it works. Seems like an innovative solution with relatively minimal environmental impact. I would be curious to see if this can be deployed in 2026 as intended and whether it can scale up to support more grid energy storage as part of the switch to renewable energy.