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Finland's New Way to Store Energy

One of the biggest hurdles in the viability of renewable energy has been energy availability and demand. It is not always going to be sunny or windy when you need energy from solar panels or windmills. Although, not all the energy these generate is used. The Current measures to store renewable energy are batteries, pumped hydro energy storage, and pumped thermal energy storage, among others. However, those measures are limited in their own ways. Batteries lose efficiency over time and are expensive and unsustainable to manufacture. Pumped hydro energy storage consists of placing a reservoir into, or near a river or ocean. They use the excess energy to pump water up into the reservoir and release it back down through turbines to regenerate the energy. This comes at an environmental impact and it is not 100% efficient either. Hydro storage has an efficiency of around 75% to 85%, according to the 2020 World Energy Council report. There is a similar story for pumped thermal energy storage, but a recent development might change this dilemma.

Earlier this month, a sand battery was installed at the Vatajankoski power plant in Kankaanpää, Finland by Polar Night Energy. This is a type of pumped thermal energy storage, where the excess energy from renewables is used to heat up sand in an insulated tank. This heat can then be used later when there is an energy demand. Earlier versions of pumped thermal energy storage used gravel or other inexpensive materials. Sand is similarly abundant, inexpensive, and capable of insulating and retaining heat up to 1000 degrees Celsius. Polar Night Energy explains the mechanism on their website,

“Inside the sand we build our heat transfer system that enables effective energy transportation to and from the storage. Proper insulation between the storage and environment ensures long storing periods, up to months, with minimal heat losses.”

Their website also claims these sand batteries are able to store 20 GWh at 99% efficiency. Meaning that for every 20GWh of energy stored only 0.2 GWh are lost to entropy. This eclipses other former variations of pumped thermal energy storages. which were only capable of around 70% efficiency at the high end. On top of this, these sand battery tanks can store energy for months and have a lifespan of 10s of years as opposed to current solar batteries that only last 5-15 years.

In last month’s C Change newsletter we read that Finland vowed to beat the Paris Agreement’s net-zero emissions pledge by being net-zero by 2035 instead of 2050. This month a Finnish company has rolled out a viable solution to storing renewable energy at a high efficiency. The country has been dependent on Russia for most of its gas and energy. With the current war in Ukraine demanding energy, it seems Finland is responding by going more sustainable. This sand battery is a big step in the right direction, and may be the spark that renewable energy has needed to gain an edge over our dependency on fossil fuels.


1. “Climate change: 'Sand battery' could solve green energy's big problem” BBC News.

2. “Store Wind and Solar Power as Heat in Sand” Polar Night Energy.

3. “How to store renewable energy” LiveScience.

4. “Five Steps to Energy Storage” World Energy Council.

5. “An Analysis of Pumped Thermal Energy Storage With De-coupled Thermal Stores” Frontiers.


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