Positive energy buildings are typically thought of as new and energy-efficient buildings with innovative technologies. The latter often implies complex equipment and systems that are difficult to repair and recycle, and with a significantly shorter lifespan compared to the structural system. For example, PV systems are known to have a lifetime of roughly 25-30 years.
Professor in Sustainable Architecture at NTNU, Tommy Kleiven, is a guest speaker in the podcast De store spørsmålene (The big questions) together with Professor Edgard Hertwich and Heidi Rapp Nilsen, hosted by Anne Sliper Midling. In the episode they discuss the importance of bringing a circular economy into the building industry, and three key points pointed out as solutions:
- Build less and smaller: Flexible use of spaces allows for several functions to happen in the same space at different times or simultaneosly. Sharing of common spaces are another strategy to utilize each squaremeter more efficiently.
- Reuse of building materials and components: It is challenging and needs to be used for a fitting purpose. The end of life phase needs to be considered early in the building process to allow for future disassembly and reuse.
- Do not build new buildings, rather transform and renovate: This requires creative solutions when the existing conditions are not ideal for a traditional design, but alternative solutions might allow for transformation into new functions and create interesting spaces.
I recommend tuning in and listening to the podcast!
But back to the question, can circular economy and positive energy buildings live in a symbiosis? This is a topic that I constantly have at the back of my mind. It is urgent to move the building industry into a circular economy to reduce the environmental impact, especially from the extraction of resources and production of new materials. PV panels have arrays of photovoltaic cells, and the cells consist of semiconductors. A semiconductor is a material that partly conducts current, with material properties in between that of a conductor and an insulator. They are made of crystals, typically silicon crystals. Silicon does not exist in pure form in nature, but is extracted from other materials, such as quartz. In Norway there are several quartz-mines. Silicon is the second most common element in the earth’s crust, and it is not harmful for our health or to the environment. However, due to the soldering in the PV panels they contain small amounts of led, which is a harmful material and without a substitute at the moment. The panels are classified as electrical waste, and shall be recycled accordingly at the end of life.
According to Solenergiklyngen, the largest contributor to the greenhouse gas emissions from PV panels is the energy use during the production stage, and the transportation is of significance as well. Therefore, PV cells produced in Norway result in very low emissions compared to other countries due to a greener energy mix.
The solar expert Professor Harald N. Røstvik at Stavanger University (UiS) says that there are projects with solar systems for which the lifetime has exceeded 30 years, and been in use for up to 50 years. This is a good prognosis for solar energy. However, we need to be able to reuse and recycle the components of PV and PVT panels when they no longer function properly.
In the current practice PV panels are considered waste and in best case recycled. However, the recycling process can recover around 95 % of the panel. Recycling in itself is downcycling the material, and therefore it is more beneficial to be able to reuse and repair the panels. CIRCUOL estimated that 50 % of the current PV waste could be repaired and continue to provide renewable electricity instead. There exist initiatives, but the market for end of life services for PV panels has not been large enough to make it economically feasible.
Technical innovations to improve the environmental impact from PV panels are ongoing, for example to eliminate the use of led. With the increasing number of PV installations, a larger market for PV repairs and reuse will develop and allow for more economically feasible solutions focused on a circular economy. The industry is not there yet, but initiatives and innovations are leading the way.
So to answer my initial question, YES – circularity in plus energy buildings is possible!
Sources:
Anne Sliper Midling, De store spørsmålene , NTNU, URL: https://shows.acast.com/de-store-sporsmalene, accessed: 22.03.2022
Doug Lowe, Electronics Basics: What Is a Semiconductor?, Electronics All-in-One For Dummies, 2nd Edition, URL: http://www.dummies.com/article/technology/electronics/general-electronics/electronics-basics-what-is-a-semiconductor-180018, accessed: 23.02.2022
Solenergiklyngen, Solcellepaneler – miljøpåvirkning gjennom levetiden, 05.03.2020, URL: https://www.solenergiklyngen.no/2020/03/05/http-solenergiklyngen-kunnskapsbyen-no-2020-03-05-solcellepaneler-miljopavirkning-gjennom-levetiden/, accessed: 23.02.2022
Kurt Lekanger, Slik utvinnes silisium til elektronikk og solceller, 15.06.2015, URL: https://www.tek.no/nyheter/nyhet/i/GGnnRB/slik-utvinnes-silisium-til-elektronikk-og-solceller
Tsanakas, Heide, A., Radavičius, T., Denafas, J., Lemaire, E., Wang, K., Poortmans, J., & Voroshazi, E. (2020). Towards a circular supply chain for PV modules: Review of today’s challenges in PV recycling, refurbishment and re‐certification. Progress in Photovoltaics, 28(6), 454–464. https://doi.org/10.1002/pip.3193