Sand Batteries: A New Technology to Store Renewable Energy as Heat



The Russia-Ukraine conflict continues to affect different parts of the world in diverse ways. Since Russia is one of the major energy producers, the conflict has resulted in energy prices across the world soaring, especially for oil and natural gas. In the aftermath, the food costs have jumped up to 30 percent in multiple regions. Energy is the most spillover channel for Europe, as Russia is a critical source of natural gas imports, and this has disrupted the supply chain widely. This also led to fuel price inflation, slowing down the recovery from the pandemic. 

The energy stations that are just working for a few hours in the wintertime, when it is the coldest, will be extremely expensive. But sometimes, the best solutions come out of dire predicaments. The researchers from Finland have come up with a new concept to mitigate the energy situation in the country due to not getting the gas from Russia. They have built a sand battery, which has the potential to store the green energy for months. The new technology that could be used worldwide was developed by the young Finnish engineers from a small town called Tampere, Tommi Eronen, and Markku Ylönen, founders of Polar Night Energy. This will help solve the country's year-round battery supply problem. “We were talking about how - if we had the liberty to design a community for ourselves - how could we solve the energy problem in such a confined environment? Then quite quickly, especially here in the north, you run into the problem of energy storage if you're trying to produce the energy as cleanly as possible,” Markku says.

How to Build Sand Batteries and How does it Work?

The duo used low-grade sand to build the batteries, which can be charged with heat from electricity generated using solar or wind energy. Sand stores the heat at around 500°C. The process is called Resistive heating, also known as Joule heating or Ohmic heating. The hot air generated will be circulated to the sand through a heat exchanger. Since sand is a very effective medium for storing heat and loses little over time, researchers believe the sand battery could keep sand at 500 degrees Celsius for several months. Therefore, when energy prices increase, the battery can discharge the hot air. This air could warm the water for the heating system across homes, offices, and the local swimming pool. 

Markku says, “There’s really nothing fancy there. The complex part happens on the computer; we need to know how the energy, or heat, moves inside the storage, so that we know all the time how much is available and at what rate we can discharge and charge.”


Is Sand a Sustainable Material?

The large battery installed at the Vatajankoski power plant (Kankaanpää, Finland) uses sand from a sandpit from the nearby locality. Demand for the construction material is set to soar by 45 percent in the next 40 years while sand is typically extracted from rivers and lakes, and sand pirates are speeding up the extraction, causing harm to the ecosystem. Researchers used builder’s sand for the prototype to limit transport emissions, but sand batteries work with any kind of material with a high enough density within certain thermodynamic parameters. For instance, recently, a team of scientists from Hiroshima University used a combination of milling, heat treatments, and chemical etching to process the rice husk silica. They milled rice husks and extracted silica (SiO2) powders by burning off organic compounds of milled rice husks. Then they heated the resulting silica powder in an electric furnace to obtain Si powders via a reduction reaction. With 3nm crystalline particles, it produces SiQDs that are luminescent in the orange-red range with a high luminescence efficiency of over 20 percent.

However, the focus is less on the sand and is all about helping the wind and solar sectors grow. Researchers think that it is just one of the key components to making society with a really high production of wind and solar power

Industries Using Sand Batteries

There are a few challenges to using these sand batteries as well. One of them is whether the technology can be scaled up and it can really make a difference. On the other hand, according to the researchers, when the sand is used to return power to the electricity grid, the electricity falls dramatically. 

However, the major benefit of sand batteries is that they can be used for storing green energy as heat lasts for a longer period. It will significantly help the food and beverage, textiles, and pharmaceutical industries, wherein they generate heat by burning fossil fuels.  

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