Energy storage and its combination with electric network ancillary services is a major issue in electric networks with a high percentage of variable renewables. The current project aimed to evaluate a method that combines electrolytic energy storage with existing steam power plants, with the goal to provide primary and secondary control reserves. Key component is a steam generator that combusts stoichiometric mixtures of H2 and O2 to produce steam that is in turn injected directly in the cycle of a steam power plant. The project concentrated on the technical validation and adaptation of a H2 - O2 combustion system and its economic and market evaluation.
The experimental part of the project aimed to demonstrate that the combustor and its control systems can burn stoichiometric mixtures of H2/O2 and generate steam that conforms to the specifications of steam power plants. The flow field and the mixing properties of the combustion system have been analyzed in a water channel. On a second step, its operational maps, the temperatures at its exit and the flame positions were measured in a new combustor rig. For the measurement of the gases remaining in the product steam a ZrO2 sensor and gas chromatography were employed.
An in depth market analysis has been performed in the fields of network ancillary services and energy storage systems. The available technical solutions, the market size and the expected development of the two markets in the coming 10 - 15 years were analyzed. It was found that the increasing renewable generation share in the European power grid has already started to increase the demand for primary control reserve. Moreover, the demand for positive secondary reserve is expected to increase in the next 10 years in Germany by 40%, whereas the negative by 10%. The presence of varying renewable generation is expected to put further pressure on the existing fossil fuel units in terms of their operational flexibility. In fact, the residual load hourly ramps in the next decade in many European countries will exceed 10% of the system load at the respective hour. Furthermore, the projected penetration of renewable generation in Europe in the next decade will frequently lead to more negative residual loads, thus increasing the need for fast and reliable energy storage facilities. The detailed economic study has shown that the main parameters affecting the financial performance of the system are the primary control and electricity prices. The use of the existing power plant infrastructure and the relatively low investment costs, could make this system attractive for power generation facilities. At the same time the system store energy in the vicinity of existing steam power plants and limit costly ad time consuming electrical grid extensions.
These results supported the initial assumptions of the project team, which subsequently contacted several utility companies in Germany and Europe. The main takeaways can be summarized as follows:
• Power generation companies face considerable financial problems in Europe, mainly due to the extra power capacity inserted to the system through renewables. This issue has led to a considerable excess in capacity and mothballing of expensive and very efficient power plants. Utility companies are reluctant for new investments and currently try to compensate for the losses from the current market conditions.
• Utility companies and TSOs are using plant dispatching methods to compensate for current fluctuations in generation.
• Energy storage and control reserves are the focus of future planning in the European electric system, all other possibilities will be exhausted before storage is applied in large scale.
• During the discussions, no arguments were raised against the capability of the proposed system to offer primary control reserve, but also operate as a power arbitrage system efficiently.
Based on these findings it is concluded that the proposed system will be able to simultaneously address all issues on energy storage, operational flexibility and ancillary services in a very efficient and cost effective manner. The team will thus continue to develop the technology.
