Evaluation of Combined Heat and Power (CHP) concepts for improved integration into future energy system

Within ReMaP Task 3.5, two options to improve the flexibility and exergy efficiency of a conventional CHP system are investigated with simulations. The more promising option is further tested with hardware in the loop (HIL) experiments on the ReMaP platform. Preliminary simulations show that a steam methane reformer (SMR) CHP concept is to be favoured against the concept of combining the CHP with a ground thermal storage system and a heat pump. Even though the latter has an infinite potential for flexibility, its efficiency suffers massively from thermal losses through diffusion in the ground. The SMR-CHP concept increases the degree of self-sufficiency in electricity demand by 30.7% and the exergy efficiency by 8.6% over the course of a one year simulation compared to the conventional CHP system.

A standard heat-led control concept for conventional CHP systems is improved by also considering economic aspects and using linearized models of the investigated systems to optimize control parameters. For the conventional and the SMR-CHP system, the operating costs are reduced by 1.9% and 2.1% while the degree of electrical self-sufficiency is increased by 9.1% and 2.9% at the cost of reducing the exergy efficiency by 0.6% and 1.3% respectively. Both hardware and software components are integrated into the ReMaP platform (Simulation Framework) successfully. Subsequent HIL experiments with real demand data from the NEST building at Empa prove that the optimized control concepts for both the conventional and the SMR-CHP system are working in practice when applying a moving average filter to the electricity demand.

A prototype SMR-CHP plant is sized, designed and built on the basis of the Aladin II mCHP plant (see [1]). First experiments show that the chosen SMR components are not able to withstand the pulsations of the exhaust gases in combination with the very high temperatures of up to 750°C. Three constructive and operational improvements of the system are identified during the experiments.

For more information contact Philipp Buchecker.