The researchers' new battery is made of wood, lemon and coconut


Published 1 April 2023 at 13.16

Domestic. KTH researchers have produced a transparent, thermal battery consisting of three natural components, which can store heat and cold. Currently, one hundred kilograms of the material can save around 2.5 kWh per day in heating or cooling if it were to be used in house construction, given that the ambient temperature is around 24 degrees Celsius.

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– The wood provides strength, the lemon-based polymer enables transparency, and the coconut-based component stores heat energy, says Céline Montanari, researcher at the Department of Biocomposites at KTH.

The new battery has led to a new scientific publication in the journal Small. The researchers have created the material that the battery is made of by removing the lignin from the wood, which makes the wood material resemble paper. In that state, they then add a building block from lemon (the limonene) together with a molecule from coconuts (lauryl alcohol).

– When heat is applied, the lemon building block is transformed into a cross-linked bio-based plastic material around and inside the porous wood structure, which elegantly captures the coconut building blocks in the material, says Peter Olsén, researcher at the Department of Biocomposites at KTH, in a press release.

The coconut-based molecule in the transparent wood material can transition from solid to liquid by melting, absorbing energy, or liquid to solid by crystallizing (releasing energy). Like when water melts and freezes at 0 degrees Celsius.

The coconut molecule absorbs heat at a slightly more comfortable 24 degrees Celsius. Above 24 degrees, the molecule melts and absorbs heat that is stored for later use. When the temperature drops below 24 degrees Celsius, the molecule begins to crystallize and releases the previously stored heat to the surroundings.

– More specifically, the amount of energy in this transition for our materials is 87 J/g. If we have 100 kilos of this material at home, we save approximately 2.5 kWh per day in heating or cooling if the temperature varies in this range, says Céline Montanari.

The researchers have given some thought to possible areas of use. One is as a future building material for both transparency and energy saving.

– Why not as a future material in greenhouses? When the sun shines, it becomes transparent and lets in more energy, while at night it becomes cloudy and releases the heat stored during the day, says Peter Olsén.