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Components for Cold Storage Systems
BMWi (PT Euronorm)
Dr. Jörg Waschull
Flexible energy consumption of cooling systems
Aim of the Project
Refrigeration technology contributes with more than 14 % to the electric power consumption in Germany. Cold storage is therefore an important means to level out supply demand differences. ILK Dresden developed and demonstrated the required components of a cold storage system for smart grid integration. The first problem that was solved was the controllable thermal connection of the quasi isothermal PCM cold storage to a cold room with fluctuating heat ingress. This system bases on a valve controlled looped thermosyphon which works without any auxiliary electrical energy.
The problem of the indication of the state of charge of the thermal storage was solved by the integration of an elastic element into the storage enclosure. The elastic element has the property to change its electrical resistance according to the applied strain. Characteristic correlations between the electrical resistance of the element and the volume (and with that with the state of charge) of the storage could be verified experimentally. A micro controller based control unit was developed to control the refrigeration system in dependence on the cooling demand, the current state of charge of the cold storage and the availability or cost of electrical energy.
To demonstrate the feasibility all components were integrated into a domestic refrigerator (Fig. 1).
The proposed technical solutions provide the basis for a great variety of cold storage applications. This includes e.g. refrigeration systems for optimized self consumption of electricity from photovoltaic systems, refrigeration systems for energy supply with variable tariffs and refrigeration systems for regions with unstable energy supply. Cold storage technologies in combination with the required peripheral components (state of charge sensors, control elements) provide the capability to act as a compensating part of an energy supply system with fluctuating sources.
The main results of the project are summarized in the following video presentation and are published as an original paper in the Energy Procedia.