One of the challenges with renewable energy is that it’s not always windy or sunny, so wind turbines or solar panels aren’t always generating energy. If the energy that they produce can be stored, though, it can be used as a back-up power source when the sun isn’t shining. So being able to store energy is important to support the growth of renewable energy.
Beyond that, it’s a factor in the development of the UK’s smart grid. Energy storage means that the grid can be more responsive. For example, if there is unexpected demand or failure in supply, then the stored energy can be used to supplement the existing amount available.
Methods of energy storage
The last couple of years have seen real growth and innovation in the area of energy storage, as it begins to attract more investment. 2018 saw the world’s first liquid air storage and the world’s first project using ammonia to store energy.
These store electrical charge by passing it through liquid electrolytes stored in tanks. The electrolytes have their electrons removed and are then returned to the tank. When the energy needs to be used, the electrons are added back to the electrolytes. It’s a very scalable process because the amount of power that can be stored simply depends on the size of the tanks used.
Until recently, flow batteries were dependent on the metal vanadium, which is rare and expensive. But in late 2018, researchers at Utah State University came up with a potential alternative. They found a way to manage the removal and addition of the electrons using ammonium. The science is in its early stages but looks promising in terms of offering good operational lifetime without environmental risks.
Liquid air energy storage (LAES)
Highview Power opened the world’s first LAES plant in Bury, Manchester in June 2018. LAES works by converting air to a liquid, then back to a gas. That process releases energy to drive a turbine and the turbine then produces electricity. The hope is that the plant will prove that LAES is a viable method for storing energy over the longer term. The stored energy can be fed into the grid when needed.
The plant in Bury can store 15 MWh of energy, which is 15000 kWh. That’s enough to power 15000 laptops for a day.
Green ammonia energy storage
In 2018, Siemens opened its Green Ammonia Energy Storage demonstrator site. The site aims to show the lifecycle of energy from generation to storage to use. To do that, the plant uses renewable energy, creates hydrogen by means of water electrolysis and then draws nitrogen from the air. Combining hydrogen and nitrogen creates ammonia, and the overall process is carbon neutral. The ammonia can be easily stored or transported for use as fertiliser. As well, it can be used to power gas turbine engines to generate electricity. Finally, it can also be split back into hydrogen and nitrogen, with the hydrogen then used in the fuel cells for electric vehicles.
The potential of all these energy storage options is in their ability to maximise the use of renewable energy, helping the UK and the world hit carbon reduction targets.
 ‘Ammonia storage plants and vertical farms: The best green innovations of the week’. 6 July 2018. https://www.edie.net/news/8/best-green-innovations-of-the-week-July-6-18–/.
 ‘New generation of flow batteries could eventually sustain a grid powered by the sun and wind’. 31 October 2018. https://www.sciencemag.org/news/2018/10/new-generation-flow-batteries-could-eventually-sustain-grid-powered-sun-and-wind.
 ‘Siemens develops world’s first energy storage demonstrator to deliver carbon-free power of the future’. June 2018. https://www.siemens.co.uk/en/news_press/index/news_archive/2018/siemens-develops-worlds-first-energy-storage-demonstrator-to-deliver-carbon-free-power-of-the-future-.htm.