Emerging technologies and energy storage

Among the top ten of last year’s most promising emerging technologies, according to Scientific American, is the development of utility-scale energy storage. The world is undergoing a rapid transition in terms of electricity production, with wind and solar technology increasingly taking over from carbon-dependent energy systems. Eurostat estimations are that in the European Union renewable energy increased by two thirds in the period 2007-2017. This means that in 2017 renewable energy represented 17,5% of energy consumed in the EU, with the 2020 target being 20%. The situation in the United States is comparable, with renewable energy sources accounting for about 11% of total US energy consumption and about 17% of electricity generation in 2018, according to the US Energy Information Administration.

Despite the progress in expanding renewable ways to generate electricity, the intermittent nature of solar and wind energy means that the energy needs to be stored. Advances in technology and materials have greatly improved the reliability of modern battery systems and reduced their cost. Batteries, which have come a long way since being invented by Alessandro Volta in 1800, are on the basic level devices “consisting of one or more electrochemical cells that convert stored chemical energy into electrical energy”. Energy-storage technology, in particular lithium-ion batteries, has made such progress in the last decade that they now account for more than 80 percent of the US’s utility-scale battery-storage power capacity. Scientific American expects that “lithium-ion batteries will likely be the dominant technology for the next five to 10 years … and continuing improvements will result in batteries that can store four to eight hours of energy—long enough, for example, to shift solar-generated power to the evening peak in demand”.

However, energy storage at longer timescales will mean moving beyond lithium-ion batteries, whose principle downside is that they lose capacity the more they are charged and discharged – thus ultimately needing replacement. There are several potential candidates to complement lithium-ion batteries, including flow batteries, hydrogen fuel cells and pumped-storage hydropower.

While flow batteries have lately attracted the attention of many investors, commentators have also noted that these batteries seem to be losing momentum. Explaining that “flow batteries are seen as ideal for large-scale, long-duration storage because they can store large amounts of energy using scalable tanks of relatively cheap electrolyte”, they also point out that nobody seems to need this long-duration capacity just yet.

Energy can also be stored by converting it into hydrogen fuel. The magazine Science describes the process whereby electricity from solar and wind power is used to split water into oxygen and hydrogen gas, a carbon-free fuel. In a next step, so-called fuel cells can convert that hydrogen back to electricity.

Finally, pumped-storage hydropower is mentioned as a candidate to supplement lithium-ion batteries. This method, which relies on gravity, is cheap once installed but expensive to build and allows adjustments to periods of high electricity demand and low demand. During periods of high demand the water that is stored in the upper reservoir is released, while the same reservoir is recharged using lower-cost electricity during periods of low demand.

Edited by: Dr. Olivier Vonk