Keeping the lights on with liquid air

 By Michael Belfiore

More than 25% of the world’s electricity now comes from renewable sources, with the percentage growing at a rapid clip, according to the International Energy Agency (IEA). That’s the good news…

The United Nation’s Intergovernmental Panel on Climate Change warns that avoiding catastrophic climate change depends on reducing, and even reversing, carbon emissions. Moving to renewable sources of energy helps by replacing carbon-rich fossil fuels for electricity production.
There’s just one problem: renewable energy isn’t available all the time. But a UK-based startup called Highview Power says it has a solution based on liquid air. “We call it a cryogenic battery“, says the company’s CEO Javier Cavada.

The storage problem

The fastest-growing renewable source of electricity for the grid is solar panels, followed by wind power, according to the IEA. But each of those sources is intermittent. Solar panels don’t feed the grid when the sun isn’t shining, and windmills don’t turn when the wind isn’t blowing. For these sources to become truly viable, the grid needs storage – a way to bank electricity for later use.

Dealing with the intermittency of renewable sources has always been tricky

Pumped hydro – water pumped uphill and then released downhill to power generators – along with lithium batteries are currently the storage options of choice for the grid. But pumped hydro is limited by the availability of water and hills, and lithium batteries can economically store only enough energy to keep the lights on for four hours or so before running down. A renewable energy-powered grid will need storage that lasts longer without depending on surrounding geography.
Enter cryogenic energy storage from Highview Power.

Liquid air storage

A Highview Power cryogenic battery looks like any number of other industrial processing plants, complete with outdoor plumbing, insulated storage tanks and cooling fans. That’s by design. It uses standard industrial components, making it easy to build where needed and to the scale as required.
The system stores energy and sends electricity back to grid in three steps. First, grid electricity powers an industrial liquefier, which alternately compresses and expands air it until it gets cold enough to turn to liquid.
“It’s industrial refrigeration”, explains Cavada. “It’s the same process you use to liquefy natural gas and make LNG (Liquefied Natural Gas)”.
Next, the liquefied air, 800 times denser than ordinary air, gets pumped into insulated tanks.
“In a way, what you are doing is creating a reservoir of water like the Hoover Dam in Nevada”, says Cavada. “But instead of water, what you’re getting is liquid air“.

The cryogenic energy storage system (

Power from liquid air

Even with all the equipment needed to liquefy and store air, the cryogenic battery still occupies 100th the volume of a comparable pumped hydro system, says Cavada. “You could say that you have pumped hydro in a suitcase”.
There the liquefied air remains until power is needed, for example at night when solar energy isn’t available.
“You can store it in tanks as long as you need it”, says Cavada. “You can store it for hours, days, weeks or months because it’s so cold that you don’t need high pressure to keep it inside of the tanks. It’s just a normal insulated tank”.
To generate electricity, the system uses ambient air to warm liquid air drawn from the tanks. The liquid air expands, returning to a gaseous state under pressure. The pressurized air then drives an off-the-shelf turbine generator.
“Instead of steam, you are using air”, says Cavada. “It’s as simple as that”.
The system uses no fossil fuels to generate electricity. The only exhaust is air, actually cleaner than when it went in, says Cavada.

One of the Highview Power's cryogenic energy storage plants (

The future of grid storage

Highview Power isn’t the only company with a solution for the grid storage problem. Toronto-based Hydrostor has a system for storing energy in the form of compressed air. Gravitricity in Edinburgh proposes raising and lowering 3,000-ton weights in mine shafts. Gravity Power in California wants to store energy in pressurized water. And Energy Vault in Switzerland plans to stack concrete blocks with robotic cranes and lower them to generate electricity.
But Highview Power’s cryogenic batteries are among the most developed solutions for long-lasting storage that can be situated anywhere it’s needed.
Working with $50 million in private financing, the company has built five plants in its home country, with several more in the works. It also plans to begin construction of a plant in the United States to store energy from a wind farm in the Midwest in 2020, slated to begin operation in 2022. In July, the company engaged Tenaska, a leading energy management company, to develop up to four more projects in the United States.
“We can do everything that the pump hydro can do, but you don’t need the water and you don’t need the valley,” says Cavada. The system also generates electricity for at least 12 hours at a time – three times longer than typical lithium battery setups.
All of which means that Highview Power’s cryogenic batteries may just have what it takes to help combat climate change with 100% renewable energy.

READ MORE: Turning to intelligent battery energy storage by Andrew Burger

about the author
Michael Belfiore