District heating

Life-cycle environmental impacts of geothermal heating networks in Geneva

20.05.2021

Operated in closed-loop systems, geothermal heating has zero direct carbon emissions, but little is known about its indirect environmental impacts that occur throughout the life cycle. A life-cycle assessment study analyzed the environmental impacts of six configurations of heating networks in Geneva using shallow and medium-depth geothermal systems.

Space heating in buildings in the State of Geneva significantly contributes to climate change due to the use of fossil fuels that supply around 87% of the heat demand (DIT, 2020). Recently, the State set an objective to reduce greenhouse gas emissions by 60% in 2030 compared to the level in 1990, and geothermal heating is one of the key solutions (République et canton de Genève, 2020). Geothermal heat from shallow to medium depth, exploited directly or with heat pumps, is expected to grow and cover around 30% of the heating demand in 2050 (République et canton de Genève, 2020).

A life-cycle assessment study carried out by Renewable Energy Systems group at the University of Geneva, in collaboration with Service industriels de Genève and the State of Geneva under GEothermies program, analyzed the environmental impacts of six configurations of heating networks in Geneva using shallow and medium-depth geothermal systems. As shown in the figure, the six configurations were defined by coupling four categories of well depths (10-100 m, 350-1600 m, 1800-2300 m, and 2300-4000 m) and three types of heating networks (connected decentralized heat pumps in a low-temperature grid, and centralized district heating in a high-temperature grid with or without heat pump). The study compared the impacts of these six configurations with those of other heating technologies that are popular in Switzerland.

In sum, geothermal district heating networks are suitable options for decarbonizing the heating sector in the State of Geneva and in Switzerland more generally. In addition to relatively low life-cycle greenhouse gas emissions, most other environmental impacts are relatively low too, except for impact on mineral resource scarcity. The latter can be minimized with careful design to reduce the use of steel-based network pipes and to increase the heat pump efficiency.

To the article «Life-cycle environmental impacts of geothermal heating networks in Geneva» on the blog of the university of Geneva (Institut des Sciences de l’Environnement)

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