A major development in sustainable architecture has enabled researchers to convert ordinary timber into an advanced thermal reservoir. In this case, lignin is removed from wood through chemical modification and phase change materials are added, giving rise to a new product that has been termed ‘solar battery,’ which stores solar energy collected by a building during the day as latent heat. Traditional solar systems have variables such as intermittence. Still, because of the nature of the bio-based materials used, the thermal conditions of these solar batteries are stable and release their stored energy until long after the sun goes down.This discovery is based on Advanced Materials Science and will allow us to achieve zero carbon emissions when heating our homes or controlling the temperature inside them. By utilising the natural porous structure of wood, this new technology will provide a bridge between energy harvesting and long-term storage, using the actual walls of our homes as insulated heat batteries.
Wooden solar battery works even in total darkness
A chemical delignification process is being used to create a new type of battery. Researchers at KTH Royal Institute of Technology have successfully removed lignin from wood and filled the resulting holes in the wood with polyethene glycol (PEG) to create a thermal battery. When the sun shines on the wood and heats it, the PEG will melt and absorb a large amount of heat energy to store it. At night, when temperatures drop, the PEG will crystallise and release the stored heat into your home. The total amount of heat that can be stored is around 760 kilojoules per kilogram (kJ/kg), which means that this new building material can act as a climate control system without requiring any electricity.
How Wood’s hierarchical structure captures photons
To maximise the absorption of solar radiation, scientists have advanced the concept by embedding plasmonic nanoparticles directly into the micro-channels of the wood as per the story published in Science Advances. These metallic particles are engineered to resonate with the solar spectrum, effectively trapping and converting photons into thermal energy with an efficiency rate reaching nearly 99 per cent. The natural hierarchical structure of these wooden fibres acts as a light trap, forcing sunlight to bounce repeatedly within the porous channels until it is entirely absorbed as heat. This concentrated thermal energy can elevate the material’s temperature to over 82 degrees Celcius (180 degrees Fahrenheit) in a matter of minutes. This efficiency makes the wood not only suitable for space heating but also for intensive applications such as solar-driven steam generation and water purification.
Decarbonising the grid with bio-based thermal storage
According to the US Department of Agriculture, residential energy consumption is one of the main sources of carbon emissions, and using engineered wood in modern construction can help solve this pressing problem. Engineered wood will help buildings reduce their reliance on the electrical grid and HVAC systems by being a source of passive thermal regulation through thermal mass. It also serves as a carbon sink, locking away atmospheric carbon for the building’s lifespan. Unlike synthetic batteries and mechanical systems that hoard energy, thermal batteries made from wood are biodegradable. They come from forests managed with sustainability in mind, offering an eco-conscious option that aligns with the construction industry’s global decarbonisation goals.