Carbon Flows in the Energy Transition

Authored by SCCER BIOSWEET partners at EPFL (Theodoros Damartzis, Xiang Li, François Maréchal)

In the project “Carbon Flows in the Energy Transition”, a methodology is developed to monitor and assess the energy and carbon flows in the energy system of Switzerland. As the flows of carbon, either in the form of released CO2 or stored in chemicals, are linked to the form and operation of the energy system, the design of the latter is crucial. Since the defossilization of the energy system is an important part to reach climate agreement goals, emphasis is given in renewables and biogenic carbon-containing resources, such as various forms of biomass and waste.
The potential of carbon and energy sources in Switzerland are evaluated in the first part of the project. In Switzerland, there is a yearly potential of 3.2 Mt wood (dry substance) and 3.1 Mt non-woody biomass (dry substance) for energetic use. Another carbon source is carbon dioxide from air or flue gases. While air has a small carbon dioxide content of 410 ppm, industrial sources provide flue gases with higher concentrations: cement plants (3.29 MtCO2/y), waste incineration plants (4.25 MtCO2/y) and sewage-treatment and biogas plants (1.1 MtCO2/y). Renewable energy sources are restricted as well. The above mentioned potential of wood corresponds to 14 TWh/y. The energy strategy from the Swiss Federal Office of Energy (SFOE) calculates with a potential of 38.6 TWh/y hydro power and 4.3 TWh/y wind power. A newly published study shows a potential for PV and thermal solar energy of totally 67 TWh per year, installed on roofs and building faces.
In the first part the demand in heat, mobility and electricity is evaluated as well. In the year 2017, the demand in space heating was 66.4 TWh/y, in hot water 12.7 TWh/y, in high temperature process heat 26.5 TWh/y and the demand in electricity was 40.9 TWh/y. Passengers travelled in total 132′ 200 Mpkm, and freight was transported over 44’000 Mtkm. The demand in electricity was covered by hydro dams (20.72 TWh/y), running river hydro plants (15.95 TWh/y), nuclear power plants (19.50 TWh/y), combined heat and power plants, incl. waste incineration (2.80 TWh/y), PV (2.28 TWh/y) and wind power plants (0.22 TWh/y). Heat and mobility was covered by fossil fuels: Light fuel oil (35.54 TWh), Natural gas (33.03 TWh), diesel (31.82 TWh), gasoline (27.67 TWh) and jet fuels (21.10 TWh). Wood provided with 13.73 TWh also a large amount of energy. Heat pumps produced 4.64 TWh, and 0.69 TWh heat was provided by thermal solar.
In the second part of the project, energy and carbon conversion technologies (around 120 in total) were evaluated. These technologies include power plants, technologies for heating, cogeneration, mobility and transport, as well as biomass technologies, power-to-X-technologies and others.
The resulting data is incorporated into the existing infrastructure of Swiss EnergyScope (SES), an optimization algorithm for the design of energy systems and applied for the case of Switzerland. Using a formulation to account for the carbon content of the various streams within the energy system, both the energy and carbon flows can be tracked during the design of different scenarios related to future energy policies. A selected number of indicative scenarios are presented that can be used to investigate the necessary future actions towards nuclear phasing-out, defossilization and CO2 taxation to name a few, with regard to the energy and carbon emissions profile of Switzerland.

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