Rebekka Koch
The building and housing sector will be one of the greatest levers, not only in creating sustainable cities and communities, but also in mitigating the current climate crisis. Rethinking buildings as power stations and constructing them as power plants offers an impactful way to steer the sector towards a more sustainable future.
Avoiding emissions in one of the most emitting industries
The average person spends 90% of their lifetime in buildings. The shelter they provide is fundamental to humanity, providing us with space to grow, educate and live. Unfortunately, these buildings come with a cost. The construction and housing sector accounts for around 38% of global yearly energy-related CO2 emissions (Braun, 2021). Buildings need energy to cool, heat and illuminate just to name a few. As of now, this energy does not stem from only renewable sources, making buildings responsible for more than a third of global greenhouse gas emissions.
There are three kinds of CO2 emissions from buildings: The direct, the indirect and the embodied carbon. Direct emissions come from fossil fuel combustion in the house. They make up 9% of all global energy-related carbon dioxide emissions. All emissions related to quarrying, manufacturing, and transportation of construction materials, as well as building renovation and end-of-life contribute to “embodied carbon” and they account for 10% of global emissions. Finally, 19% of global emissions are indirect, meaning emissions from the use of electricity and commercial heat (Abergel, 2021). To reach Net Zero emissions by 2050, major changes need to happen in all these processes.
Knowing the categories of emissions caused by buildings, there are many possibilities to make buildings and housing more sustainable. One of them is planning and constructing new buildings in a way that energy is generated, stored, and used by the building itself. This concept is called “Buildings as Power Stations”. Instead of simply being a passive consumer, every building, however small, can play an active role in the electric power system (Coma & Jones, 2015). The idea of a building as a power plant is a part of the previous concept and describes a building that produces the same amount or more energy than it consumes, also called “Zero Energy Building”. Some of those buildings already exist as examples, and new ones are built around the world. But it is important that this standard becomes more accessible and widespread.
How can a building be a power plant?
The underlying concept of buildings as power stations is quite intuitive. First, the building will generate energy from renewable sources, such as solar power or wind. This energy directly covers demand. Generating the energy directly in the building, rather than exporting and importing it to the grid, reduces costs, increases reliability, and improves the system’s efficiency. In case of excess renewable energy generation, the energy will be stored in the building’s energy storage system for later use. Oppositely, when generation and storage cannot cover the demand, electricity will come from the grid. This basic concept applies to individual buildings, but it can also be upscaled to fit communities or even cities (Coma & Jones, 2015).
Figure 1. Illustration of the energy flow paths (Coma, 2015)
Housing associations are promoting variations of this concept with different labels. One widely acknowledged label is by the German Sustainable Building Council (DGNB) called “Klimapositiv” which translates into climate positive. A building can receive this label, when the amount of CO2 emissions avoided through the method described above is greater than the amount of emissions generated by the building. Meaning the building would have a negative yearly CO2 balance. This label is only valid for one year. To keep the label, buildings need to prove their CO2 balance again in the following year. Lemaitre, managing director of the DGNB, explains this philosphy: “Climate positive is not a building trait, it is dependent on the operation of the building, thus regular checks and evaluations are needed and sensible.” In 2019, the first buildings were awarded with this label (DGNB, 2019).
One example of a building as a power plant is the city hall of Freiburg, Germany. The DGNB awarded it with the climate positive label in 2019, thereby being one of the first buildings to receive the label. It is one of Europe’s biggest surplus energy houses designed by Inghoven Architects. The building has a very efficient heat protection. It therefore only needs low temperature for heating and it can be cooled with low energy cooling systems. The ventilation system with heat recovery reduces the need of energy further. The roof and sunlit areas of the facade are equipped with highly effective photovoltaic collectors, which provide sun protection at the same time. The building produces more energy than it uses, but it exports the excess energy to the grid instead of storing it in batteries (DGNB, 2019).
Figure 2: City Hall, Freiburg, (HGEsch and Hennef, 2019)
Not only new buildings can be carbon negative, but existing buildings can also be renovated to emit less CO2. A prime example situated in Mühltal, Germany, was also awarded climate positive by the DGNB. The house, originally built in the 70s, was renovated in 2011. During the renovation, they drastically improved the energy efficiency of the house and installed photovoltaic generators on its roof. It now produces more energy than it consumes (DGNB, 2019).
Figure 3: Renovated house from the 70s, Mühltal, (diephotodesinge, 2019)
The actions we need to take and our leadership role
The building and construction industry must become a climate leader by moving towards net-zero construction. According to a recent report by the United Nations Environment Programme (UNEP), this industry must cut 50% of its emissions by 2030 for building stock to be carbon-free by 2050. For that to happen we need collaboration across diverse sectors involving stakeholders along the whole building and supply chain. Braun (2021) estimated that 2.5 billion more people will move to cities, mainly in Asia and Africa, meaning that in the next three decades, 60% of buildings required by 2050 still must be built. Considering this, the building sector now has the chance to promote and research zero-carbon building designs, making it easier for future goals to be met. But our focus should not only concern new buildings, to make ends meet we also need to work on existing buildings.
Oslo, Copenhagen, and Stockholm pledged to take a leadership role in the decarbonization of the building industry. Oslo for example announced, that all city owned machinery and municipally or owned construction sites will operate with zero emissions by 2025. Raymond Johansen, Governing Mayor of Oslo stated: “New kindergartens, schools, sports halls will in future be built emissions-free and with low climate materials. The building industry is our closest ally and an enthusiastic supporter. We are confident that by 2030 Oslo’s air will be cleaner, emissions lower and the environment healthier thanks to the actions we are taking today.” (C40 Org, 2019). This attitude should be applied to cities world-wide, including Swiss cities.
As discussed above, it is possible to build and renovate buildings to make them act as small power plants. These buildings could solve the energy shortage problem, they also make living healthier and by intelligent design more comfortable. “At the core we want to think of new constructions as power plants and promote renewable energy generation everywhere.” (DGNB, 2020), stated the DGNB. This summarizes the direction of where the building and construction industry should be heading in the future.
References
Abergel, T. (2021). Decarbonizing the Building Sector: Why your home cannot stay the same. Brink. https://www.brinknews.com/decarbonizing-the-building-sector-why-your-home-cannot-stay-the-same/
Braun, S. (2021). 5 Things to know about carbon-free construction. Made for minds. https://www.dw.com/en/5-things-to-know-about-carbon-free-construction/a-52747374
C40 Org. (2019, October 7). Mayors of Copenhagen, Oslo and Stockholm commit to clean construction. C40 Cities.
DGNB. (2019). Klimapositiv ausgezeichnete Gebäude. DGNB. https://www.dgnb.de/de/themen/klimapositiv/ausgezeichnete-projekte/
Esther Coma, P. P. (2015). ‘Buildings as Power Stations’: An Energy Simulation Tool for Housing. Cardiff: Elsevier
https://doi.org/10.1016/j.proeng.2015.08.404
DGNB. (2020). Bauen für eine bessere Welt. Stuttgart: DGNB.