Seasonal pumped hydropower storage (SPHS) — an already established, yet rarely used technology — could be used to store water and energy providing a provide much-needed affordable way to store renewable energy, according to a new paper published on 19 February in Nature Communications (1).
Fossil fuels are exacerbating climate change and Nonetheless, the renewable energy sector has yet to become a viable competitor to oil and gas. At present, wind and solar power are the most promising low-carbon energy options. Wind and solar farms have been popping up across the globe with many countries promising a switch to 100 per cent renewables.
However, despite improvements in both performance and cost over the past few years, as well as improved energy storage batteries, the intermittency of renewable energy sources make it difficult to match supply with demand, necessitating methods to reduce and shift the timing of demand for electricity.
Without energy storage, wind and solar technologies are limited to minimal annual capacity and adoption. But how can renewable energy be stored in a viable cost-effective way?
Lithium-ion batteries might provide a short-term solution to intermittency issues, but the high cost coupled with the need for raw materials lithium, nickel, manganese, cobalt, and graphite creates yet another set of problems. Therefore, long-term solutions are still needed to overcome seasonal variation. Lead author Dr Julian Hunt of the International Institute for Applied Systems Analysis (IIASA) explained in a statement:
“The energy sectors of most countries are undergoing a transition to renewable energy sources, particularly wind and solar generation. These sources are intermittent and have seasonal variations, so they need storage alternatives to guarantee that the demand can be met at any time”.
“Short-term energy storage solutions with batteries are underway to resolve intermittency issues, however, the alternative for long-term energy storage that is usually considered to resolve seasonal variations in electricity generation is hydrogen, which is not yet economically competitive”.
The technology works by pumping water into a deep storage reservoir that is built parallel to a major river when the water flow is high or energy demand is low. Then, when water is scarce or energy demand increases, water in the reservoir is released to generate electricity. Since the reservoirs are parallel to the river, the environmental impact is much lower than traditional hydropower dams.
In their analysis, the team at IIASA assessed the potential and costs of SPHS technology on a global scale. They looked at various scenarios using data on topography, river networks and hydrology, and infrastructure costs to identify technically feasible candidate sites.
Based on their results, Hunt and colleagues estimate a total global energy storage potential of 17.3 PWh, which is equivalent to almost 80 per cent of the world’s electricity consumption (based on 2017 figures) at a cost of 50 US$/MWh.
More specifically: water storage costs would vary from 0.007 to 0.2 US$/m3; long-term energy storage costs from 1.8 to 50 US$/MWh; and short-term energy storage costs from 370 to 600 US$/KW of installed power generation capacity, considering dam, tunnel, turbine, generator, excavation, and land costs.
The authors also found that the technology would be particularly effective in the Himalayas, the Andes, Alps, and the Rocky Mountains, as well as mountainous regions in the Middle East, Brazil, Asia, and Russia, and many other locations around the world.
Hunt added: “With the need for a transition to a more sustainable world with lower CO2 emissions, renewable energies and energy storage will play a major role in the near future. Given the vast untapped and cheap potential of SPHS, it will soon play an important role in storing energy and water on a yearly basis”.
(1) Hunt, J.D. et al. Global resource potential of seasonal pumped hydropower storage for energy and water storage. Nature Communications (2020). DOI: 10.1038/s41467-020-14555-y