Investigation of a Demand Side Management Potential in the Water Supply Industry for the Integration of Renewable Energies
With the ongoing growth of electricity generation from renewable energy in Germany, the changed power generation structure is challenging the power supply system and industrial consumers. The fluctuating feed-in of solar and wind electricity into the grid and its regional distribution requires adjustment of all future electricity supply system generators and consumers. Consumer-related measures to enhance flexibility help integrating renewable energies into the electricity grid. Due to the delay in grid development, bulk consumers in southern Germany play a major role, because of their capability of short-term load shedding. Caused by their specific structure, supra-regional water supply systems, such as the Bodensee-Wasserversorgung, may in case of a necessary water elevation, consume a vast amount of energy. Hitherto, the pumping regime is solely based on the water demand of the supply system and the well-known framework of peak and off-peak tariffs. However, it hardly considers the availability of renewable energies or the overall power demand.
Fig. 1: Elevated tank Büttnau at the entrance of the Alb-tunnel
There is a large potential for demand site management especially in energy-intensive systems of the water supply sector. By organizing the pumps´ operating time in a flexible manner, their usage can be adapted to the volatile wind and solar energy feed-in and thus raise the overall share of the power consumption generated by renewable energies. Simultaneously, the security of water supply at a shortage of electricity is heightened and the flexible operation linked to cost-effective electricity procurement, resulting in a sustainable energy supply. The research project: “enWasser - Investigation of a Demand Side Management Potential in the Water Supply Industry for the Integration of Renewable Energies” focusses on the power supply of supra-regional and long-distance water supply systems. In this interdisciplinary joint project, the energy supply by renewable energies only is examined and what necessary measures need to be taken accordingly.
The focus of the collaborative project lies on water storage capacities and all further actions in order to expand the storage capability. With the integration of water reservoirs the pumps´ electricity consumption can be adapted to the energy generation and can in terms of time be uncoupled from the water demand. In the course of the exploitation of a demand side management potential of this sort, the own and external generation of renewable energies can be used and the volatile electricity prices taken advantage of. The storage of large quantities of untreated and clean water out of energetic purposes raises new challenges, which are not state of the art in the conventional water storage sector. So far, water reservoirs aimed at guaranteeing a sufficient supply of water, while in the future, they can be used similarly to pump storage plants. Hence, the project´s approach needs to find a balance between both the requirements for the water supply and the energy efficiency. When dimensioning and using water storages, many aspects need to be considered, such as the energy-economic benefit, a possible water quality degradation, the structural expenditure and the technical capabilities of the equipment. It is the initiative´s objective to create a sound basis for the energetic and water management related assessment of the demand side management potential in large-scale water systems as well as their implementation. Due to the interdisciplinary approach, the mandatory requirements are defined from various perspectives and the demand side management potential evaluated accordingly.
Fig. 2: Water treatment plant on top of the Sippling hill
One focal point lies on the development of energy supply concepts for the water supply system of the Bodensee-Wasserversorgung and supply systems experiencing similar challenges. Included in this work package is the development of measures in order to realise the demand side management of the pumps and the corresponding dimensioning of water storage capacities. In doing so, the operation of the water supply system can be implemented by an electricity supply of largely renewable energies. The concepts are then economically evaluated by means of future energy supply scenarios. An additional priority lies in the examination of the necessary technical measures that need to be taken for a flexible operation of the plant in dependency of the availability of renewable energies. At this point, the requirements concerning especially the water treatment with storages between different treatment stages as well as the pumping technology are thoroughly investigated. Building on those achievements, an integrated plant concept is developed, that contains all relevant constraints concerning the pumps, pipes, water treatment, water storage capacities and the corresponding measures. Within the context of preliminary planning, the costs for the developed measures are estimated. Furthermore, the energy supply concepts of the water treatment plant are examined by a simulation of the plant-operation in the course of a year for their energy efficiency. For this purpose, plant models are designed that optimize the operation of the aggregates over time of the power supply, the water availability and the water withdrawal in the distribution grid. In conclusion, the compiled measures for the demand side management and the energy supply by renewable energies are evaluated with regards to their cost-benefit ratio and their risks.