In order to combat the devastating effects of climate change and ensure a clean future for coming generations, massive investments and research are being undertaken in renewable energy solutions. Arguably, numerous advances have been made in solar and wind power – but these systems have a major drawback: they are most effectively used when the sun is shining or the wind is blowing.

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This brings us to the biggest challenge the sector has to tackle: effective ways to store that energy for longer, so it can be used when the sun and wind are not available. Mass-scale energy storage does exist, but it is dominated by just one technology: pumped hydro, where excess electricity is used to pump water into a reservoir, and that stored water is in turn used to run turbines to generate extra power when needed. There are other technologies, such as batteries, electrochemical storage, etc., but these make up a small percentage of total capacity (less than 5% of the total, according to policy group REN21).

This gap hasn’t gone unnoticed: some of the biggest companies and several top investors are funneling money into research on mass-scale energy storage. And this is a market that will continue to grow as renewable energy as well as battery costs are set to drop further in coming years.

Read more: Forbes