By developing a method for calculating the carbon footprint of energy used in Switzerland on an hourly basis rather than as a yearly average, EPFL researchers have shed important light on an otherwise obscure industry.
Despite recent advances in power grid technology, engineers still struggle to measure the carbon footprint of one kilowatt-hour (kWh) of energy used in Switzerland. That’s because of the many different variables that must be taken into account. The carbon footprint of the country’s energy use is currently calculated as a yearly average - even though it varies considerably throughout the day.
EPFL researchers have now succeeded in performing a more granular calculation using a pan-European database of hourly power generation figures by country over the course of a given year (2015-2016). This breakthrough can give electricity suppliers and consumers more detailed information on how they use this important resource.
The EPFL study shows that the carbon footprint of electricity generated at certain times of day is up to five times higher than estimated. And that’s not all: "Thanks to this data, I know that if I charge my smartphone in the afternoon, for example, I’m more likely to draw on a renewable energy source than if I charge it in the evening," says Didier Vuarnoz, a co-author of the study along with Thomas Jusselme - both members of Building 2050, a research group at the Smart Living Lab in Fribourg. They just published their data in the open-access journal Data in Brief , so that engineers and businesses can use them freely. An initial summary of their research appeared in the 24 July 2018 issue of Energy.
New European database
Switzerland makes some of its own electricity and imports and exports it with France, Germany, Austria and Italy. That makes it hard to know which country the energy used at any given time comes from. Vuarnoz and Jusselme had the idea of using the pan-European database, called the ENTSO-E Transparency Platform, to ascertain this information. Launched in 2015, the database contains hourly records of the electricity flowing between European countries.
The researchers converted the kWh from the database into a carbon equivalent based on the entire life cycle of the electricity source (nuclear, carbon, hydraulic, etc.). Each kWh generated was assigned a certain number of carbon emissions based on whether it originates from fossil fuels or renewable energy. Then they developed a series of graphs that engineers can use to quickly see what kind of energy is consumed in Switzerland on an hourly basis over the course of a year.
However, the idea is not to encourage everyone to shift their energy consumption to times of the day when renewable sources predominate - as that would just transfer the problem. Rather, the goal is to develop new strategies for electricity use. Vuarnoz, Jusselme and their colleagues from the smart living lab used their data to publish an article in the August issue of Sustainable Cities and Society that takes the example of a building producing some of its own energy. By walking readers through their example, they illustrate the benefits of having access to hourly energy consumption information.
"I could program my washing machine to run in the afternoon instead of at night, for instance, if I know that my apartment building draws on solar energy in the afternoon," says Jusselme. "An hour-by-hour view lets you know when you should use the battery-stored power at a building in order to fully leverage the carbon benefits of that energy. For example, if at night you use clean energy stored in a battery instead of power generated at a German coal-fired plant, you can shrink your carbon footprint," adds Vuarnoz.
The researchers hope their method will prompt consumers and businesses to be more intelligent in when they turn on the power switch. But they still believe more efforts are needed to encourage grid operators to provide more transparent information, so that their method can be improved further.
Similar studies were carried out in France, Belgium, Sweden, and Finland between 2013 and 2015 but using other databases. Vuarnoz and Jusselme’s method is tailored specifically to Switzerland’s intricate electricity-trading system. The next step will be to automate the process of downloading power generation and consumption data in real time, so that trends can be identified from one year to the next and engineers can make reliable carbon-footprint forecasts - much like meteorologists do with weather forecasts.
All this matters because if Switzerland wants to become a 2,000-watt society by 2050 and support the energy transition, its engineers need accurate, reliable methods for calculating the country’s environmental impact and implementing alternatives to fossil fuels. "Our new method promises to be highly effective in helping Switzerland meet its 2050 energy goals. And the limitations of our method highlight the important work that is still needed to better understand Switzerland’s energy-related carbon footprint," says Jusselme.
Vuarnoz, D. Jusselme, T. " Dataset concerning the hourly conversion factors for the cumulative energy demand and its non-renewable part, and hourly GHG emission factors of the Swiss mix during a one year period (2015-2016) ", Data in Brief, 26 October 2018.
Vuarnoz, D. and Jusselme, T. "Temporal variations in the primary energy use and greenhouse gas emissions of electricity provided by the Swiss grid," Energy, 24 July 2018.
Vuarnoz, D., Cozza, S., Jusselme, T., Magnin, G., Schafer, T., Couty, P. and Niederhauser, E.-L., "Integrating hourly life-cycle energy and carbon emissions of energy supply in buildings," Sustainable Cities and Society, 29 August 2018.