From a windswept sea wall on Englandâs north Kent coast, Marie King points to miles of empty marshy farmland where there will soon be thousands of solar panels and one of the countryâs largest battery installations.
A mile from the village of Graveneyâs Norman church, hundreds of shipping containers full of battery cells will help deliver power to the UK grid. It will provide a service essential to managing the increasing use of wind and solar power, the supply of which fluctuates with the weather, and delivering on politiciansâ promises of a greener future.
âItâs the scale of this project that worries me,â Ms King, a retiree who used to work in financial services in London, says. âWeâre not against renewable energy â we just think it needs to be in the right place.â
Such battery plants are set to become a familiar sight across the UK and elsewhere. Renewables such as wind and solar are becoming cheaper than fossil fuels in most parts of the world, but they need storage to be a viable, stable source of energy.Â Last week, UK prime minister Boris Johnson vowed to install enough wind turbines to power every home by 2030, but that will require solutions to manage the intermittent supply of energy.Â
That is where batteries â devices which store electricity as chemical energy â fit in. Lithium-ion batteries, used in mobile phones and Tesla electric cars, are currently the dominant storage technology and are being installed from California to Australia, and most likely Kent, to help electricity grids manage surging supplies of renewable energy. Elon Musk, Teslaâs chief executive, has said he expects the companyâs energy business â including the supply of solar and huge lithium-ion batteries for the grid â to be as big as its car business in the long term.
But along with lithium-ion batteries, cheaper, longer-duration storage technologies â most of which are not yet cost effective â will be required to fully replace fossil-fuelled power plants and allow for the 100 per cent use of renewable energy. At the moment, gas-fired power plants bridge the gap from renewables to provide stable supplies of energy for longer than current batteries can.
Part of the UK governmentâs green industrial revolution launched last week is a ÂŁ1bn energy innovation fund to help commercialise new low-carbon technologies. These include a liquid air battery being built by Highview Power outside Manchester.Â
Without storage it will be harder for countries to significantly reduce their use of gas and coal-fired power plants and decrease the harmful effects of climate change, from rising sea levels to extreme weather conditions.Â
From battery technologies that use abundant raw materials to volcanic rocks, tanks full of liquid air, and systems that lower weights down abandoned mine shafts, companies are racing to develop the next breakthrough that will unlock large-scale renewable energy by mid-century. Itâs a quest backed by several prominent business leaders, including Microsoft founder Bill Gates and SoftBankâs Masayoshi Son.Â
âIf we want full decarbonisation then all these technologies will be required,â says Rory McCarthy, an analyst at the energy consultancy Wood Mackenzie. âBut the scale of investment you need to make a dent on anything is billions of dollars.â
Every day electricity grids must constantly match supply with demand â a feat that becomes much harder when you strip out coal and gas-fired plants that provide a reliable, steady supply of energy. Donald Sadoway, a Canadian chemistry professor at the Massachusetts Institute of Technology, likens the grid to the âworldâs largest supply chain, with zero inventoryâ.
In the first quarter, renewables provided a record 47 per cent of the UKâs electricity. Yet that success created a problem just weeks later when energy demand fell by as much as 20 per cent after the first national coronavirus lockdown in March. The National Grid’s job becomes more difficult when electricity generation from renewablesÂ reaches about 50 per cent of the total â it needs the help of big spinning turbines of fossil fuel plants to moderate volatility in the system.Â
With demand falling it meant the renewables share of the energy mix went above half and the engineers at the National Grid’s control centreÂ were forced to perform aÂ delicate balancing act, part of which involvedÂ increasing the use ofÂ storage â vindicating, say advocates, expansion of the technology.
It proved to be a test case for how the grid will look in the future, when there is a greater share of renewable energy, says Peter Kavanagh, chief executive of Harmony Energy, which provides power to the grid from six Tesla lithium-ion batteries in Poole on Englandâs south coast.
âSolar and wind are the cheapest form of generation in multiple countries, but you need that storage to make it work once you have got the renewable penetration to a certain size of your energy mix, like we saw during Covid,â he says. âCovid hasâ.â.â. proven the business case [for battery storage] five years in advance.â
More than 97 per cent of the worldâs energy storage is currently done by using electricity to pump water up to a high reservoir and then releasing it, which drives a turbine to create even more electricity, so-called âpumped hydroâ. The reservoir of water acts as a way of storing energy. But these systems are challenged by geography and could be limited by increasing water scarcity in the future.
The advantage of lithium-ion batteries is that they can be placed anywhere and can provide power to the grid very quickly, as they do in electric cars. They can respond in milliseconds and generally provide up to four hours of storage, helping grids deal with sudden outages in electricity generation, but are less cost effective in the longer term. In the UK, the majority of large-scale lithium-ion batteries provide energy for 30-90 minutes.
And local residents such as Ms King worry about their safety, after a spate of battery fires over the past few years. There were 33 fires at installations in South Korea between 2017 and 2018 alone, and there have been more recent incidents in the UK and US.
Alternative technologies could enable safer storage of large amounts of energy for longer periods of time, which would allow even greater integration of wind and solar. But they need to be scaled up quickly in order to meet rising demand and become cost competitive.
In January, the California Energy Commission, the US stateâs primary energy policy and planning agency, issued a call for long-duration energy storage â defined as providing energy for over 10 hours â enough to store a dayâs worth of solar energy for overnight use.Â
One of the winners of the tender was Invinity Energy Systems, a company that uses large batteries based on vanadium, a raw material used by the steel industry to increase the metalâs strength. These so-called Redox flow batteries â first developed by Nasa in the 1970s â use large tanks of separately charged electrolytes to store energy, which makes it easier to expand capacity than conventional batteries.
Matt Harper, the companyâs chief operating officer, says vanadium batteries can store eight to 10 hours of renewable energy during the day and deploy it during peak demand, or overnight, helping to put a floor under power prices. They are also âmore likely to put out a fire than start one,â he says, because they use a water-based electrolyte. They also last longer than lithium-ion cells â and can go for 30 years.
In the centre of Dalian, north-east China, Rongke Power is building the worldâs biggest vanadium battery. At 800 megawatt-hours, it would be more than three times the size of the worldâs largest lithium-ion battery installation in California. It would help Liaoning provinceâs electricity grid better integrate wind power.Â
âWe would not be allowed to install a large-scale lithium-ion battery in the city centre, [due to safety concerns],â says Li Bin, Rongkeâs marketing director. âThe safety issues in lithium-ion batteries have not been solved.âÂ
Yet vanadium prices are highly volatile and surged to $127 per kilogramme in November 2018 before falling to $25 per kg today, which could have an impact on the cost of production.
MITâs Prof Sadoway believes that technologies need to be based on more abundant metals than those used in lithium-ion and vanadium batteries such as aluminium, sulphur, calcium and antimony. In 2005 he helped develop a liquid metal battery that uses calcium and antimony and a molten salt electrolyte. The company that developed it, Ambri, was backed from the beginning by Mr Gates, who invested in it after watching Mr Sadowayâs chemistry lectures online.
Ambriâs battery aims to store energy for longer than six hours and Mr Sadoway believes that its cost can go below $150 a kilowatt-hour when it is deployed at scale, which would make it cheaper than current lithium-ion systems. âWe want to undercut lithium-ion,â he says.
The company has yet to find a large commercial customer and Mr Sadoway warns over the long timeline for developing new battery chemistries: âThis is tough tech, itâs heavy industry, itâs not like writing code,â he says. âThis is really hard.â
Others looking for storage options are avoiding batteries altogether and trying natural and physical solutions similar to pumped hydro â which can store energy for up to 20 hours â but without the need for natural reservoirs.
Outside the German city of Hamburg, a large grey concrete windowless building has the words âWelcome to the new stone ageâ written on the front in purple letters. The plant is run by Siemens Gamesa, the worldâs second-largest wind turbine manufacturer, and uses 1,000 tonnes of volcanic rock from Norway to store 130 MWh of energy in the form of heat, providing enough energy for about 3,000 German households, or roughly 750 electric cars.
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Electricity is used to first heat the volcanic rocks to at least 600C. The energy can be stored for up to a week, but the target is to dispatch power overnight. The system can be installed in coal-fired power plants that are closing and use their turbines, according to Hasan Oezdem, head of innovation projects at Siemens Gamesa.
âYou can turn them into giant storage facilities,â he says. âThe biggest utilities are looking desperately for a second life option as you canât sell them â nobody is buying coal-fired power plants. We offer to keep it running with a green purpose.â
On the outskirts of Manchester, a similar project is taking shape at the site of a decommissioned power plant â using vessels of liquid air rather than volcanic rock. Highview Power broke ground on its 250 MWh plant at Trafford Energy Park in November after winning a ÂŁ10m grant from the UK Department for Business, Energy and Industrial Strategy.
âLithium-ion is great technology, but itâs too small for the challenges the grid is seeing,â Javier Cavada, the companyâs chief executive, says. âThe business model of long duration [storage] is to make sure all the wind and solar generation is utilised.â
Despite their various advantages, these technologies will find it hard to beat the manufacturing scale of lithium-ion, which has been driven by the surge of investment in electric cars over the past decade. The price of lithium-ion batteries fell 87 per cent in real terms between 2010 and last year, to about $156/kWh, according to Bloomberg New Energy Finance.
That price is likely to fall further. Globally, battery installations for grid storage are set to rise to 741 gigawatt-hours by 2030, most of it lithium-ion, led by the US and China, according to Wood Mackenzie. One GWh is enough to power 1m homes for an hour.
In addition, hydrogen, which is produced through the electrolysis of water using electricity, could emerge as a competitive solution for storing energy for longer periods of time. Hydrogen can be stored in underground caverns or depleted oil and gasfields.Â
Hive Energy, which is planning the Cleve Hill solar and storage site near Graveney, is deciding which technology to use for its battery but is likely to opt for lithium-ion, the companyâs managing director Hugh Brennan says.
âItâs like trying to not buy an iPhone,â he says. âItâs also more profitable to provide short-term energy storage to take advantage of differing power prices.â The company plans to install at least 200 MWh of batteries, he says.
In Graveney, however, placards stand outside the church and alongside the road with pictures of gas masks and the slogan âNo solar power plant!â Ms King and other residents say they are not against the expansion of renewable energy, but they hope that another storage technology will be used for the site.
âFor all the risk itâs not giving them a huge ability to store energy,â Ms King says. âIf there was different technology that was safer, clearly we would welcome it.âÂ
Additional reporting by Nathalie Thomas in Edinburgh
Storage of renewable energy requires low-cost technologies that have long cycle lives â where they can be charged and discharged many times â are safe and can store enough energy cost effectively to match demand.
Vanadium redox-flow batteries use two tanks containing positive and negatively charged liquid vanadium electrolytes that are pumped past a membrane in a cell. The batteries have less degradation than lithium-ion and a longer cycle life.
Liquid air is cooled to minus 196C, after which it is stored in tanks. It is then heated, which drives a turbine to generate power. An alternative uses heated compressed air to store energy in purpose-built caverns.
Gravity storage involves lifting heavy blocks up and down abandoned mine shafts as a way to store and generate energy.
Thermal energy storage Matla, a company backed by Bill Gatesâ Breakthrough Energy Ventures, stores energy as heat in the form of molten salts. The company says the technology can last longer than 20 years and is suitable for six-plus hours of storage.
Liquid metal batteries uses metals that naturally separate when heated to form a cathode and anode separated by a salt electrolyte. Once initially heated the battery maintains its high operating temperature by generating heat on discharge and charge.
Low-cost batteries using cheap raw materials such as iron, sulphur and zinc offer alternatives to lithium-ion battery technology. Zinc-based battery developer EOS, for instance, says its battery has capacity to discharge energy over three to 12 hours. Form Energy, a start-up backed by Bill Gates, says its battery can store energy cost effectively for up to 150 hours
Hydrogen using electricity to produce hydrogen is a way of storing energy, but there is a substantial loss of energy in the process, making it less efficient than batteries.