ORC steam expansion engine utilises waste heat for the highly efficient generation of electricity
|Project plan||Further development and optimisation of the ORC steam expansion engine, development of 4 field test systems with partners for demonstrating the recovery of waste heat from different waste heat flows in industry and in combination with renewable energy sources. As part of the joint project, new organic fluids will also be developed along with a heat exchanger concept for highly polluted exhaust gases. The operational modes and results of the continual operation tests will be monitored and analysed.|
|Developer, organizer||DeVeTec GmbH, Steag New Energies, Evonik Industries AG|
The efficient and economic use of available energy sources for producing electricity is one of the most important challenges facing us in the future. Approximately 75% of the primary energy used is lost for further utilisation in the form of waste energy. Companies that recover waste heat flows produced during industrial processes instead of releasing it unused into the environment can already make a considerable contribution to protecting the climate and environment.
In order to utilise this potential, DeVeTec has developed a new steam expansion engine, which – integrated within an ORC system – enables waste heat to generate directly usable electricity.
As part of a field-testing programme, the ORC steam expansion engine will be tested in continual operation, the motor components and the heat transfer system will be optimised and the engine will be driven in various operational modes. Further project tasks include the development of new organic media for temperature ranges above 400°C and less than 200°C as well as the development of a heat exchanger for strongly polluted exhaust gases.
The focus of the newly developed ORC system is on generating electricity from heat produced by renewable energy sources and from low-temperature heat (< 400°C) produced during industrial processes that previously could not be sensibly used. For this purpose a new kind of steam expansion engine was developed. This acts as the processing machine in a steam power cycle, whereby it uses an organic fluid instead of water. At low temperatures this fluid has considerably better thermodynamic properties than water. This therefore enables directly usable electricity to be generated from the low-temperature waste heat.
In a nutshell, waste heat becomes high-quality and CO2-neutral electricity, whereby the heat flows show different characteristics in terms of their constant availability and amount of exhaust gas as well as their contamination with pollutants and temperature.
In order to be able to use the many decentralised heat sources with thermal capacities of less than 4 MW, this requires new solutions for capacity ranges between 50 and 300 kWel. For this purpose an ORC module was developed that can be operated in a capacity range between 100 and 200 kWel. A piston engine is used as the processing machine, which in terms of its efficiency, adjustability to different waste heat parameters and use of discontinuous heat flows, has clear advantages over the turbines usually used in the ORC process.
Ethanol is used as the working fluid, which has excellent thermodynamic properties for temperatures greater than 300°C and achieves a high overall electrical efficiency. Directly vaporising the organic medium also makes it possible to reduce the components for the ORC process and thus achieve cost savings. The resulting reduction in the payback time to between 4 and 6 years in accordance with the application therefore also makes the ORC process suitable for industrial applications.
The project is being financed with funding from the industrial partners, with funding as part of the EnEff:Wärme initiative and with funds and risk capital from DeVeTec, the project manager.
In the period between 2009 and 2013, four field test systems with the new type of ORC steam expansion engine are being developed together with industrial partners. A particular feature is that the heat flows have different exhaust gas/waste heat qualities, pollutants, temperature levels and availability. For example, in addition to the steam expansion engine itself, the respective optimum combination of heat transfer system and working fluid is being looked for, whereby the standard fluid ethanol is being used for temperatures greater than 280°C. The systems will be installed in a biogas plant, chemical park, glass foundry and metal processing company.
In addition to conducting tests and the continual operation, the aim of the field test is to ensure the economic feasibility of ORC systems in a capacity output range between 100 and 200 kW and, depending on the application case, to achieve payback times between 3 and 5 years, whereby it is planned to develop a model for contracting with energy service providers as well as a model for self-use by industrial companies.
The system developed during the course of the field test programme on various waste heat sources will be analysed in a downstream, 4-year observation and monitoring phase.