The balancing of power networks at any given time is one of the major challenges for the future energy supply, in particular in order to be able to stabilize the grid with an increasing amount of fluctuating electricity production out of renewable sources such as sun and wind. It was therefore obvious to investigate the potential for load shifting amongst the largest electricity consumers in the communities, i.e. the wastewater treatment plants (WWTP), the public water suppliers and the waste incineration plants (WIP). The analyses on each two to three concrete case studies showed that the potential for load shifting is indeed considerable but that the operators in the light of their main tasks, namely, the supply and disposal of water, wastewater and waste, cannot turn on and off arbitrarily their power generators and consumers.
The projection for 2012 showed a potential for all these infrastructure facilities for 1 hour the provision of 140 MW positive and 233 MW negative regulating power on an annual average. In the future it will have risen by the year 2050 to around 198 or 290 MW respectively. With regard to the provision of positive regulating power the turning off of the electricity consumers contributes slightly more than half and with regard to the negative regulating power the power generation contributes about two-third to the potential. The potentials rise still slightly for regulating power for more than 15 minutes and they decrease to nearly the half for the regulating power for more than 2 hours, with the exception of the negative regulating power 2050.
Of the total potential of the approximately 3900 infrastructure facilities in Switzerland the 40 biggest sewage treatment plants, 30 water provision facilities and 30 incinerations plants can offer together already today around 100 MW of positive and around 200 MW negative regulation power and in the future up to 150 and 250 MW respectively, facilitating the possible yield of these potentials. Even though these figures have a certain uncertainty range, they nevertheless evidence that the potential is remarkable; it is about half a gas combined cycle power plant.
Additionally, the WWTPs and WIPs can make a contribution to the seasonal load shifting of around 250 GWh/a today and approximately 350 GWh/a in the year of 2050 respectively with the costs being still quite high. The WIPs can produce more electricity during winter time by utilizing the excess capacity and the storage of waste in bales. The WWTPs can use the digester gas for the maximum power production in winter and in summer they can feed the digester gas into the natural gas grid (for example, for fuel) and they can heat the digester tower with waste heat pumps.
