Amid the rising temperatures, it is imperative to find alternate-sustainable solutions to keep our homes cool. Air conditioning systems emit millions of tons of heat-trapping carbon dioxide into the atmosphere each year.

To find an alternative solution, a team of researchers from KTH Royal Institute of Technology in Stockholm has developed an eco-friendly material that can be used to cool and even heat our homes. 

This one-of-a-kind material could be a potential game changer in eco-friendly construction.

The novel building material

The group created a building material out of coconuts, lemons, and modified wood. These renewable resources serve as a “wood composite thermal battery”. The results have been published in the journal Small.

When used in housing construction, this novel material is capable of capturing both heat and cold. Given an ambient temperature of 24°C, the team estimates that 100 kilos of this material can save about 2.5 kWh per day in heating or cooling.

The process begins with removing lignin from wood, which opens pores in the wood as well as strips the colour – resulting in transparent wood. The wood gaps are then filled with citrus (limonene acrylate) and coconut-based molecules.

When heated, limonene acrylate molecules transform into a bio-based polymer, restoring the wood's strength along with allowing light to permeate. As a result, the coconut molecules can become trapped inside the material, facilitating energy storage and release. 

“The elegance is that the coconut molecules can transition from a solid-to-liquid which absorbs energy; or from liquid-to-solid which releases energy, in much the same way that water freezes and melts,” said Céline Montanari, one of the authors of this study, in a statement. 

We can use this transition method to heat or cool our immediate surroundings as needed, the authors note. Furthermore, this building material is particularly useful for saving energy. 

Describing the material's applications, Peter Olsén added: “Why not as a future material in greenhouses? When the sun shines, the wood becomes transparent and stores more energy, while at night it becomes cloudy and releases the heat stored during the day. That would help reduce energy consumption for heating and at the same time provide improved growth.”