As the cost of renewable energy continues to decline and intermittent clean power sources such as wind and solar gain ever an ever larger foothold in the global energy mix, the ability to store energy that can be quickly dispatched when needed has become as important as the development of renewables themselves.
Robust storage options could allow for greater integration of intermittent renewables, as they facilitate flexible capacity-building that relies far less on coal and gas-fired plants for baseload generation, meaning energy storage is a key step in the journey to wean the world off its fossil fuel addiction.
But cracking the energy storage conundrum is no easy feat. Advanced flow and lithium-ion batteries with storage capability hold great promise, but costs are high and technical aspects are complex as these technologies develop. Pumped-storage hydroelectricity – or ‘pumped hydro’ – is currently the world’s highest-capacity and most efficient energy storage method, but this option, which uses off-peak electricity to pump water from a lower-elevation reservoir to a higher one and then releases the water through turbines during high-demand hours, is limited by the geographical and infrastructure requirements involved.
US-based start-up Quidnet Energy is hoping to fill a gap in the market with an underground pumped hydro concept. The company, co-founded by energy entrepreneur Aaron Mandell and former Saudi Aramco petroleum engineer Howard Schmidt, is currently using rock formations in abandoned oil and gas wells to store pressurised water, which can later be run through a turbine to feed electricity back into the grid.
Quidnet has its first field demonstration plant up-and-running in Erath County, Texas, which has produced good results indicating that the concept is technically workable, and building a commercial-scale demonstration plant in 2017 is the next step. Further down the line, the company intends to drill its own reservoirs separate from the oil and gas sector’s leftover wells, and even integrate solar generation to create baseload solar power plants.
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