Pumped hydro as a battery will be part of the renewable energy disruption. These will be both onshore and offshore. Hydropower is about 1/6th of the global energy supply with about 1,200GW. Hydro generation is nearly 60% higher than nuclear energy and greater than all other renewables combined, including wind, solar PV, bioenergy and geothermal. The opportunity is to change to wind and solar, and use hydro as a battery and reuse the limited water and sites for dam construction and environment challenges.
What is Pumped Hydro
Short-term off-river pumped hydro energy storage (“STORES”) sites require pairs of reservoirs at different altitudes, typically ranging from 10 hectares to 100 hectares, in hilly terrain and joined by a pipe with a pump and turbine. Water is pumped uphill when wind and solar energy is plentiful, and electricity is available on demand by releasing the stored water through a turbine. Pumped hydro simply relies on gravity and water and does the opposite of existing hydroelectric power stations. Sometimes the water turbines and generators are specialised to have bi-directional, and sometimes different mechanical systems – one for hydro generation and one for using electricity to pump back uphill. New ones are likely to be a single unit.
Energy in gravitational storage is very low. To get the amount of energy stored in a single AA battery, we would have to lift 100 kg to 10 m to match it. Or for 1litre of petrol, need 4 tons of water one kilometre high! So hydro needs height and storage. E.g. The Kidston pumped hydro is 250MW for 8 hours with 2 reservoirs of 50ha and 218m elevation.
In a study from Australia National University in 2017 lead researcher Professor Andrew Blakers said the short-term off-river pumped hydro energy storage (STORES) sites combined had a potential storage capacity of 67,000 Gigawatt-hours (GWh) – much more than the capacity required for a zero-emissions grid. “Australia needs only a tiny fraction of these sites for pumped hydro storage – about 450 GWh of storage – to support a 100 per cent renewable electricity system,” said Professor Blakers from the ANU Research School of Engineering.
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Ocean Pumped Hydro
Ocean Grazer has developed a proof of concept pumped hydro, modular that fits on and under the seafloor making it ideal for offshore windfarms. It uses a clean water reservoir and a bladder system with the pump / generator connecting the two. To store energy, the system pumps water from the rigid reservoirs into the flexible bladders on the seabed. Now the energy is stored as potential energy in the form of water under high pressure. When there is demand for power, water flows back from the flexible bladders to the low-pressure rigid reservoirs. Driving multiple hydro turbines to generate electricity.
They envisage these to be paired with each wind turbine and provide 80% efficiency.
Hydro Power Globally
The challenge for more hydro power is the social and environment challenges to flood new valleys. But using natural sites such as old mine sites or changing existing hydro to become bi-directional is the challenge. Check out this report on global hydro.