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International Conference on Innovative Applied Energy    

E-Proceedings ISBN: 978-1-912532-05-6

14-15 March 2019, Oxford, United Kingdom



Experimental assessment of a novel system control logic for an MCHP system incorporating an electric energy storage



Felix Gackstatter, Georg Heyer and Tim Roediger

University of Applied Sciences Landshut, Technology Center Energy (TCE), 1st Wiesenweg 1, Germany



Paper Abstract

Decentralized energy supply concepts for residential buildings will play a decisive role in future energy systems. In particular, the intelligent coupling of a photovoltaic system (PV), a mini/micro-combined heat and power plant (CHP) and an electrical energy storage (EES) offers systemically challenging perspectives. Research on such hybrid decentralized energy systems in the residential sector, especially with both electric and thermal storage systems is sparse and lacks experimentally validated system modelling. Based such a systems approach, a new control strategy is developed for hybrid systems with enhanced degree of electrical self-sufficiency (DSS).

The novel control strategy incorporates the levels (state of charge) of the thermal and electric energy storage. The so-called electric storage-following (ESF) strategy was developed by Matlab-based energy system modelling and simulation in order to improve the characteristics of grid demand and feed-in of the system compared to the conventional, thermal-load following control strategies (TLF). In the case of an eight family dwelling, the grid export from the CHP could be reduced by about 99%, the export from the PV-system to the grid by about 55% and the DSS can be rised by about 8% (from 74.5% to 82.5%) (yearly average) for the same energy system only by changing the operating strategy from TLF to ESF. The increased DSS in combination with minimal grid feed-in lead to a noticeable economical improvement of the energy system.

The performance of the ESF-strategy is not only confirmed by detailed theoretical simulations, but also by realistic measurements on an experimental cogeneration and storage test rig at TCE in the case of multi-family dwellings. The test set-up is composed of an CHP unit (a two-cylinder, natural gas fuelled internal combustion engine, with a built-in asynchronous generator, 12 kWth, 4 kWel), a thermal storage system, (0.96 m3, sensible heat storage tank), an electrical storage system (a lithium ion phosphate battery, 10 kWhel), a PV (10 kWpeak, el) and a thermal load emulator to generate appropriate load profiles for space heating and hot water. The control strategy incorporates a forecast for the PV output throughout the day, coupled with a daily electric load projection. Detailed daily and yearly simulations and experimental data will be shown.

It can be seen that the ESF-specific daily scheduling of the CHP leads to enhanced EES system capacity utilization by aligning the operation intervals of the CHP with the SOC of the electrical storage. Thus, the number of operating intervals of the CHP per day increases with the effect of a higher utilization of the electrical storage:

For example, the conventional TLF strategy would favour long operating intervals of the CHP-unit. This would quickly charge the EES to the maximum state of charge and export power produced by the CHP (and potential simultaneous provision from the PV) to the grid from this point onwards. This effect is avoided by the ESF and grid export can be minimized and leads to more favourable characteristics for grid operators and economic improvements for CHP-operators.

Paper Keywords
self-sufficiency, costs for energy storage, CHP, system control, distributed energy systems, cogeneration, electric storage-following,  thermal load-following, energy storage, PV system, degree of self-sufficiency, test rig, energy system simulation.
Corresponding author Biography

Felix Gackstatter, born in 1985, has a Master’s Degree in Energy System Engineering from University of Applied Sciences Gelsenkirchen Bocholt Recklinghausen. In 2015 he started to work as a research engineer at the University of University of Applied Sciences Landshut. At the Technology Center Energy his tasks include the design and construction of a test rig for decentralised energy systems in the research team of Prof. Tim Rödiger.

The International Conference on Innovative Applied Energy (IAPE’18)