Molten salt and human sweat: the weird batteries that could store renewable energy | Renewable energy

A sprawling land in the deserts of the United Arab Emirates clean energy projectSpanning an area the size of approximately 12,600 football fields, the project will break new ground by enabling solar energy to power the equivalent of half a million homes overnight.

The Gulf nation is steadily combining 5.2 GW of solar capacity with 19 GWh of battery storage to create the largest battery scheme in the world.

Meanwhile, about 7,500 miles away, at the US’s National Renewable Energy Laboratory facility in Colorado, researchers and engineers are producing some of the smallest batteries the world has ever seen. These batteries, a fraction of the size of utility-scale lithium-ion batteries used to store renewable energy, are designed to power electronic tags that will track 3-inch-long (about 7.5 cm) fry of salmon and eel species.

While traditional lithium-ion batteries are pushing the boundaries in terms of size and scale, alternative battery types can provide the same vital role in harnessing low-carbon energy; but it can do so without the scramble for critical minerals such as lithium, cobalt and nickel, which raises concerns for environmental protection and vulnerable communities.

Unlike lithium-ion batteries, which have a limited number of charge/discharge cycles, many of these alternative battery technologies can be used indefinitely and can be recycled when the units reach the end of their 20-year service life.

Developers are already turning to a wide range of materials to store renewable electricity when it becomes available and use it to power everything from wearable technology to heating networks to factories and missiles.

Here are some of the notable energy storage innovations.

liquid air

Late last year, Greater Manchester’s former mayor marked the start of construction of a long-awaited energy storage project on the site of a former coal power station in Trafford that could lead to the “re-industrialisation” of the borough.

Andy Burnham said the development of the Trafford green cluster, which includes the Carrington “liquid air” cryobattery, could mean “this decade is the most exciting for Greater Manchester since the Victorian era”.

In simple terms, the Carrington project developed by the British startup High Appearance StrengthIt aims to capture renewable energy when it is abundant and store it as liquid air. Theoretically, a “cryobattery” can store energy for hours, days or even weeks.

The science is more complex: Carrington uses excess renewable energy to cool the air to -196°C, reducing it to a liquid of one-700th its volume. It can be kept in this state until renewable energy runs low and market prices begin to rise. The liquid is then allowed to become a gas once again and rapidly expands through a turbine, producing electricity without the emissions typically seen in gas-fired power plants.

The project has faced a number of delays, but when it is scheduled to be operational by the end of the year, it will provide 300 MWh of storage and 50 MW of generation for six hours, or enough clean, renewable energy to power almost half a million homes.

molten salt

While energy is stored at sub-zero temperatures in Manchester, the opposite approach is followed in the Nevada desert.

Here, 10,000 panels generate electricity for the Crescent Dunes project, which has used solar energy to heat a reservoir of potassium and sodium nitrate to 560°C over the past 10 years.

This temperature can be maintained for 10 hours after sunset before the stored thermal energy is converted into electricity using the heat to drive a conventional rotating turbine. The system effectively stores clean electricity as heat in a process known as molten salt storage.

These molten salt batteries provide primary power sources for most modern guided missiles and nuclear weapons, acting as “backup batteries” that retain energy until the pyrotechnic heat generated when the weapon is launched activates the release of the energy.

In the 2020s, Denmark proved that molten salt storage technology could also provide an answer to the dilemma of decarbonizing heavy industry. The leading wind energy country announced earlier this year a 1GWh large-scale molten salt battery project that can store up to two weeks of clean electricity by heating the salts to around 600C. When needed, hot salt is circulated through a generator that produces high-temperature steam that can be used directly in industrial processes.

Sand

Just as renewable electricity can be stored by heating salt, clean energy can be stored in sand.

In the small town of Pornainen in southern Finland, thousands of tons of sand help store energy used to heat schools, libraries and town halls. This will allow the region to completely eliminate the use of oil in the local heating network and reduce the use of sawdust by approximately 60%.

sand battery It uses approximately 2,000 tonnes of crushed soapstone to store clean energy in the form of heat to provide 1 MW of thermal power and 100 MWh of storage capacity.

In summer, the sand battery, approximately 13 meters high and 15 meters wide (43 ft x 49 ft), can meet Pornainen’s heat demand for almost a month, and in winter for close to a week. It is nearly 10 times larger than the previous version launched in the country in 2022, underlining the potential for sand batteries to play a larger role in reducing emissions across the country.

sweat technology

In Japan, researchers at Tokyo University of Science are investigating how human sweat could be a suitable energy source to power wearable technologies.

By treating the body as an energy source that can provide constant power, researchers hope to solve the problem of how to fuel the sensors that power wearable devices without tiny batteries that make them bulky and need to be constantly charged.

In response, they developed a thin, wearable patch that generates electricity directly from human sweat. It uses an enzymatic biofuel cell to capture chemical compounds released in sweat (specifically lactate) and convert them into power. When sweat comes into contact with the cell, enzymes embedded in the patch trigger a biochemical reaction, releasing electrons.

This means electricity can be generated during daily activities such as walking, exercising, or running errands without needing any external power source.