Berne going green

Within the framework of a 5th semester GIS class project at the University of Zurich, we analyzed potential sites for wind and hydropower in the canton of Berne, Switzerland. Nowadays, nuclear power plants (NPP) are criticized since unsolved questions such as the long-term storage and the disposal of radioactive waste or the reactor safety are ubiquitous. Thus, renewable energy as alternative source of power are on the rise.

The nuclear power plant Muehleberg in Berne was shut down on the 20th of December 2019. It reached an annual power production of 3066 GWh. In October 2019 we started our project and were determined to figure out how the demand for electricity can be covered otherwise. We asked ourselves what alternatives there are and decided to focus on wind and hydropower.

Where are possible sites for wind and hydropower? How much power can be produced with these alternative energy sources and do they cover the power production of the Muehleberg nuclear power plant?

In order to find possible sites, various site criteria were defined and assessed using a multi-criteria analysis and further analyzing tools. After we excluded areas which cannot be used for wind or hydropower plants, for example nature reserves, we defined criteria to assess site suitability.

The defined criteria are wind speed, slope and distance to settlements, roads and high-voltage power lines. To work with these criteria in a reasonable way, we used fuzzy logic, a method which provides results close to reality. In the fuzzy logic a value range was assigned to each criterion (see table). The real data were then normalized according to so called memberships, for example linear or gaussian membership.

As an example, wind speeds of 7.5 m/s are optimal, the further away from this value the less suitable. This is best represented by a gaussian distribution, so that wind speeds of 7.5 m/s have the highest suitability values, while lower and higher wind speeds were given lower suitability values or were rejected.

The defined criteria for hydropower are slope, runoff (flow accumulation) and distance to roads and high-voltage power lines.

The real data of these criteria were normalized linearly and weighted using the analytic hierarchy process (AHP, see table). This method allows a pairwise comparison of all criteria and provides a more formal basis for assigning weights. For example, flow accumulation (column) is four times more important than distance to roads (row).

After executing the different methods, we visualized our results in maps, which are presented here.

Today, wind power plants already exist in the canton of Berne. The wind farm Juvent for example is the largest wind park in Switzerland. Potential sites for new wind power plants are in the Chasseral region, in the eastern part of the canton as well as in small areas in the southern part.

According to our experience, fuzzy logic is an appropriate method for site analysis of wind power. However, due to the complexity of the method good knowledge of the requirements for wind power is needed. Further, depending on the chosen weights, the results can differ strongly. A profound literature research is thus essential.

At present, there are numerous hydropower plants in the canton of Berne, varying in size. We would like to point out two existing hydropower plants - Aarberg (1) and Felsenau (2) - and compare the actual and calculated power production.

For a next analysis, geodata of the discharge of rivers should be included so that the total power production can be calculated. The AHP method is applicable for our research questions. Detailed information about weighting values could not be found in literature so that the weightings are partly inferred. Differences in weighting may lead to a slightly altered result.

• Optimal sites mainly in the north-west (Chasseral), east and south-west (Stockhorn)
• Power generation of the NPP Muehleberg could be covered (8488 GWh/a)
• High-altitude sites as a question of feasibility and profitability
• Fuzzy logic as a suitable method for our research questions

• Optimal sites mainly in the city of Berne and south of lake Biel
• Power generation of 221 GWh/a at five selected sites
• Geodata about discharge of rivers is needed to make a final conclusion about power production
• Exact suggestions about weighting of factors could not be found in literature
• AHP as an appropriate method for our research questions