Wind and solar are the best options for producing low-carbon energy on a large scale. And as wonderfully clean as those choices are, there is one thing that fossil fuels provide which wind and solar do not – consistency. Fossil fuels may be dirty, but those power plants can control how much electricity they produce at all times. With wind and solar power, it all depends on how much the wind is blowing and the sun shining. Meaning, a power grid that relies on such fluctuating sources can struggle to match supply and demand.
There is one way to deal with this problem – large-scale electricity storage technologies. When a wind or solar farm generates excess electricity, the system stores it. Then, when the farms aren’t producing enough to meet demands, the stored power is released. There are several versions of this technology already in use. Still, they are either costly, complicated or are limited due to geographical requirements (such as hydro dams requiring mountains or compressed air energy storage requiring underground caverns). And any method for storage requires enormous amounts of electricity.
Fortunately, now there’s a new option – pumped thermal electricity storage (TES), also known as Electrical Thermal Energy Storage (ETES). The technology has been around for around ten years. However, it hasn’t been put to the test until just last year by Siemens Gamesa in Germany.
TES works by converting electricity into heat with a large-scale heat pump. The heat produced gets stored in a medium, such as water or gravel (in the case of Siemens pilot plants, its volcanic rock) stored inside a large insulated tank. The electricity is stored there in the medium as heat until it is needed, upon which a heat engine is used to convert the heat back into power. The system utilizes the principle of thermodynamic cycles.
TES Advantages:
- The time required to design and build a TES facility is shortened because the system relies on conventional technology and uses components that are already widely used in the power and processing industries – such as turbines, compressors, heat exchangers, and electrical generators.
- All of the options for medium (the substance that absorbs the heat in the tank) are environmentally friendly – chemical and toxin-free.
- The medium that fills the storage tank consists of materials that are abundant and inexpensive – such as molten salts, water, or gravel.
- A facility can be installed anywhere in the world, regardless of geography.
- It can be scaled up or down to meet the location’s grid storage needs.
- The technology can store more energy in a given volume (has a higher energy density) than pumped hydro dams. On that note, it also requires less space for a given amount of energy stored, meaning the environmental footprint of the facility is smaller. For instance, ten times more electricity can be recovered from 1 kilogram of water stored at 100°C, compared to 1 kilogram of water stored at the height of 500 meters in a pumped hydro plant.
- The components have a long lifetime – they last for decades before needing to be replaced.
TES could significantly help societies around the world transition towards a low carbon future. Once the technology matures and is fully commercialized, it will be able to compete with other storage technologies. The faster TES spreads, the cheaper it will become, and the more it will be able to help the world tackle the climate crisis and transition to a low-carbon energy system.
