Flexibilitätsoptionen der Strom- und Wärmeerzeugung mit Geothermie in einem von volatilem Stromangebot bestimmten Energiesystem

Deep geothermal energy is an important part of the heat shift and can also make a significant contribu-tion to the provision of electrical energy. So far, the question to what extent geothermal based power-heat-systems can be used to flexibly cover the electricity demand in particular to provide operating reserve without negative impacts on the heat supply, is to date insufficiently researched. This study shows from a hydrogeochemical standpoint that a flexible operation of the thermal water cycle is largely harmless for plant components and the reservoir, especially in the Molasse Basin.The technical analysis and simulations of the geothermal plants show that the technical potential for a permanent provision of positive and negative operating reserve is small for almost all technical flexi-bility options, especially for existing plants. An exception builds the technical flexibility potential to provide positive control reserve through the use of boilers or thermal water storage systems. In this connection, the technical potential can be ranked as medium to large, however the technical effort also increases. On the contrary, the technical potential to provide positive and negative control reserve with limited temporal availability (i.e. offering slots) is medium to large for nearly all flexibility op-tions. Therefore, the limited temporal availability significantly increases the potential to provide oper-ating reserve within the offering slot. The overall potential to offer control reserves remains on a low level and the technical costs increase with regard to larger storage volumes.Compared with conven-tional combined heat and power (CHP), geothermal energy has a very variable power to heat ratio, which ensures a very high degree of flexibility between electricity and heat generation. Furthermore, CO2 emissions per unit of energy generated are more positive than with fossil CHP.Based on the current price levels and use of technical flexibility options, the economical assessments show that plants can only conditionally supply control reserves based on the current price levels and use of technical flexibility options. Existing plants, with the support of peak-load-heating-systems, can already make (small) profits by providing positive secondary operating reserve. This is not the case for existing plants without modification or extension through heat-storage. The reduction of the ap-plied value/price for electricity from geothermal would enhance the exploitation of the flexibility po-tential and therefore economic benefit. Existing plants and plants with peak-load-heating-systems can then provide economically viable negative and positive secondary control reserve. Without additional incentives, a provision of flexibility through deep geothermal plants whose electricity production is compensated by a feed-in-tariff, is therefore not expected in the near future.A temporal decoupling of the power production from the heat demand with the help of heat storage enables a more electricity-price-oriented mode of operation of the heating plant. The more flexible en-ergy system reduces the total cost by means of maximizing revenues thanks to feeding power into the power supply system at times of high electricity prices. Additional electric heat generators (such as a heat pump in this study) are used for heat recovery at very low residual load and associated low elec-tricity costs.In summary, it can be stated that the provision of control power through geothermal-based electricity and heat systems is currently possible with restrictions from a hydrogeochemical and technical point of view. The profits to be generated are low. Due to the (so far) small number of geothermal-based electricity and heat systems, the system benefit can also be classified as low.