Big batteries or bust?

How to store energy for a net zero UK in 2050?

Courtesy of Drax and Cruachan Power Station

At the moment, in fossil fuel, antiquated Britain, the government currently stores 4-5 days of natural gas for the country’s needs. The Netherlands has 9 times that capacity and Germany 16 times. It used to store a lot more at the Rough storage facility, owned by Centrica, but that was closed down in 2017 to save on a costly maintenance programme. When Michael Fallon, the Energy Secretary took the decision in 2013, he was probably expecting the fracking industry to be booming by now. If that didn’t work, we could continue to top-up with frictionless, cross-border trading for gas with our European neighbours.

Gas is not the future

The natural kind which we love to dig out of the North Sea certainly won’t be. And even though the pitiful 4-day store of natural gas, ensures the UK is more susceptible to market price hikes during a cold snap than it ought to be, we’ll all have to make do with an extra layer and a cuddle on the sofa. Or take comfort in the fact that battery storage capacity is increasing.

By December 2019, operational storage capacity was 0.7 gigawatt (GW). Currently, this has increased to 1.1 GW, spread across 729 projects. 1 GW is enough electricity to power 1 million homes for an hour, which doesn’t sound much. A lot more is planned in the future.

Let’s talk batteries

Storing electricity is becoming vital, as the UK’s dependence on renewables continues to grow. Unlike a gas-fired power station, the sun and wind are not always available. The National Grid will no longer have the luxury of balancing consumer and industrial demand with consistent fossil fuel generated electricity. In order to get to a net zero UK economy by 2050, with renewable energy at the heart of the strategy, big storage capacity becomes essential, which means batteries.

M. Stanley Whittingham, a UK scientist, described the concept of the Lithium-ion battery in the 1970s and finally received the Nobel Prize in Chemistry for his work in 2019. Lightweight and compact, with a higher energy density, they were first used commercially by Sony in 1991 in their consumer camcorders. Most electric vehicles use some form of these batteries including Tesla, who use their own lithium - nickel - manganese - cobalt chemistry.

Battery energy storage systems, based on similar chemistry, can store a lot of electricity and are super smart. They coordinate energy production, decide when to store in reserve or release to the grid, which helps to keep costs down and electricity flowing. The majority of these larger-scale batteries still only provide power for 30-90 minutes

Another issue is the chemicals needed for these batteries. Mining is focused on countries like the Democratic Republic of the Congo, which raises question marks about social responsibility and the damage being done to the environment.

This might be less of an issue if the Lithium-ion batteries favoured now are replaced by solid-state batteries in a decade or more, as currently predicted. They use solid electrolytes (rather than liquid) and are even more energy dense. That’s all potentially good news. But there are already alternative ways to store energy which don’t require battery technology at all.

Gravity Storage

Cruachan in Scotland (see picture above), is a tourist attraction I visited at the insistence of my mother, whilst on a caravanning holiday as a young teenager. The weather was typically Scottish, so why not visit a hydroelectric power station which they’d nicknamed the Hollow Mountain?

It was an engineering master feat and well worth the visit. The water stored in the dammed reservoir at the top of the mountain is released through big bore pipes tunnelled through the mountain to 3 turbines at the bottom which generate electricity for immediate use on the grid. It was designed to ease excess demand on the network, but is just as relevant today for the intermittency issues from renewable energy sources. When the wind is blowing hard, the water from the lake at the bottom is pumped back up to the top again, all the potential energy restored. It can reach full load in 30 seconds and maintain maximum power production for 16 hours and you wouldn’t even know it was there.

Why didn’t they make lots of these hydroelectric schemes? Cost was certainly an issue and there aren’t any handy mountains in many parts of the UK. But that is about to change. Hundreds of sites in the UK could be opened up and would be a lot cheaper to build than traditional hydropower dams like Cruachan. To do this, water is replaced with a mineral-rich fluid which is two and a half times denser. The same amount of electricity could then be produced from slopes half as high - foothills, rather than mountains.

Courtesy of Energy Vault

Energy Vault, a Swiss company has also used gravity to store energy. Their pilot scaled 1:4 demo at Castione, is a multi-armed crane which lifts two 35-ton concrete blocks high into the air on each crane before dropping them. As they descend, the motors that lifted them spin in reverse. The electricity generated in the 30 second descent generates one megawatt, enough electricity for a thousand homes.

Gravitricity, a Scottish company has a similar idea but is brilliantly using old mine shafts to eventually store and supply electricity to the National Grid.

Green hydrogen

Did you know there are 6 different hydrogen colours dependent on how it’s manufactured? I’ve mentioned Blue Hydrogen before, which BP are getting super excited about. That manufacturing process requires carbon capture because of the CO2 produced. Don’t even ask about Turquoise.

ITM Power, a Sheffield based company and home to the world’s largest electrolyser factory with a 1GW capacity, believe they have the answer to storage without any carbon hangover. Batteries are only good for hours, but using ITM’s electrolyses, over capacity from renewables could be stored for weeks or months. This gets around the issue of the UK’s electrical system’s operator having to pay energy developers to switch off their solar farm or wind turbines.

Water (H2O) and renewable electricity, combined with those electrolytes, enables hydrogen to be captured. The only bi-product is oxygen.

ITM has a number of partnerships including the Green Hydrogen for Scotland Consortium, responsible for the 20MW electrolyser at Whitelee Wind Farm near Glasgow, the UK’s largest onshore wind farm.

Cryogenic batteries

When air is turned into a liquid at a rather chilly -196 degrees C, it can be stored easily in big, low pressure tanks. Exposure to ambient temperatures again and it expands 700 fold in volume, which is more than enough to drive one turbine, creating electricity to power 200,000 homes for 5 hours (50 MW capacity or 250 MWh), without so much as a spark. This cryobattery will be located at their Carrington facility at Trafford Park, outside Manchester. They also have expansion plans in the US and Spain.

Thermal energy storage

Courtesy of SolarPaces

High in the Nevada desert, 200 miles northwest of Las Vegas is Crescent Dunes, a sophisticated solar power plant. The cheapest way to store all that solar energy when the sun goes down is a molten salt storage. It is heated to a balmy 560 degrees C where it is then stored in a large tank, converted to electricity through a conventional steam turbine when needed for the 75,000 Nevada homes it currently serves. The molten salt only loses 1 degree of heat per day, so it can be topped up and the heat maintained for months.

Green technology companies already demonstrating how they can be relied upon to do their part in our net-zero future.