Wood and other bio-based materials have been used for energy throughout the history of humankind. In the modern age, we could still use these materials for energy production – beyond using them as fuel. These materials can be employed in advanced energy technologies, such as solar cells. If we make a simple calculation that a solar panel weights about 10 kg/m2 and produces more than 100 W/m2, we can see that solar panels produce about 10 W/kg. As fuel, the energy content of wood is 4 kWh/kg. Thus, if we have wood-based materials in solar panels, in about 4 months at Nordic levels of solar irradiation, they have produced as much energy as they would provide as a fuel. Since solar cells are expected to last for decades wood-based materials could produce several times more their energy in solar cells compared to using them as a fuel. And, if you want, you can burn the device at the end of its lifetime. Actually, that can be a very smart thing to do to retrieve the valuable metals for their economically viable reuse.
This is a good in theory, but would it work in practice? Bio-based materials could be used for virtually all the tasks in a solar cell. Is the bio-based alternative always a smart choice? No. Are there promising bio-based alternatives for some use? Yes. For instance, bio-based carbons with their natural nanostructuring, which are high performing and stable based on our initial testing. Thus, categorizing all natural materials into simply either good or bad is flawed. Instead, to get a balanced view, we must identify the applications where their properties can easily be utilized and where perhaps more research is needed, but the potential gains justify the work.
Exploring bio-based materials and what they have to offer is important to find materials solutions that not only replace conventional materials but more importantly find new functionalities that cannot be reached with conventional materials. If it was easy, it would already be done. But like all things worth doing, this too requires effort. It requires multidisciplinary collaboration from the energy engineering side as well as from biomaterials development. In developing such insight, platforms like the FinnCERES Flagship are very important. These communities should also expand to maximize their impacts on society. This is not only a biased view from a researcher soon moving to another institution, but also a view that FinnCERES has mapped as a way for greater impact and has already taken steps in this direction.
Kati Miettunen Academy Research Fellow, Aalto University Professor of Materials Science and Engineering, University of Turku (1.4.2020 onwards)