When Kyoto Group first created the Heatcube — its groundbreaking technology for thermal energy storage — it was meant to introduce sustainable practices for the tea industry in rural Africa.
"The challenge was that farmers were using a good portion of their land to cultivate forests to grow enough wood to burn for drying the tea tree leaves," Kyoto Group CCO Tim de Haas said. "The idea was to make a simple solution that doesn't cost much: a mini CSP [concentrating solar power] plant."
Once the Norwegian startup realized the Heatcube's efficiency and effectiveness in storing heat, it redirected its focus to maximize that potential.
The Heatcube uses surplus electricity from whatever source is the cheapest option at the time, whether it's the grid or solar and wind power, and stores that energy in three types of molten salts contained in a series of modular tanks.
The mechanism relies on resistance heating, similar to how an electric kettle boils water, and can vary the temperature of the salts from 170 to 500 degrees Celsius (from 338 to 932 degrees Fahrenheit).
"The benefit of these three salts is we have a lower solidification level," De Haas explained. "Compared to the salts from CSP that solidify at about 290°C, our salts won't solidify until they get down to 131°C. So we can deliver at a much lower temperature than the salts in CSP, which means we can use different materials for the tanks, so our steel is less expensive, and we reach a broader range of customers."
When energy is required, the thermal exchanger can produce the heat as steam, hot air, or thermal oils. All these adaptable characteristics mean the Heatcube can be utilized in everything from cooking and refrigeration to steel and cement production.
It can recharge and discharge simultaneously for over 25 years while mostly relying on renewable energy without emitting carbon dioxide, making it unmatched in durability, availability, cost-efficiency, and eco-friendliness.
This has made thermal energy storage an attractive alternative to dirty energy sources. A Bill Gates-backed startup has replaced molten salt with liquid tin for its process, while another company utilizes sulfur, which has a higher energy density than molten salt.
"The main markets for us actually are in Germany and Spain. Germany has the largest requirements for industrial heat in Europe. And today, the industry uses a lot of gas to produce that heat," De Haas said. "So our main focus is to replace industrial gas boilers, helping industry reach targets for reducing CO2 emissions by replacing gas boilers with renewable energy delivered on a 24-hour basis."
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