Multi-criteria assessment and optimization of ice-energy storage systems in combined heat and cold supply networks of a campus building

Abstract

Ice energy storage systems (ICES) can be a promising technology for the combined provision of heating and cooling for non-residential buildings by utilizing currently unexploited waste heat without depending on solar assistance. However, detailed studies on the effects of different operating strategies of an ICES in the context of an overall supply system are not available yet, nor are there any design routines for dimensioning and integration. For this purpose, a detailed numerical investigation and evaluation of an ICES in the supply system of a research building is performed in this work, using one-year measurement data of the system containing 500 m3 storage. The considered building, of which about 70% of the floor area is disposed of for laboratories and workplaces, is located in Bayreuth, Germany, where a warm and moderate climate with an annual average temperature of 8.9 °C is prevailing. Thereby, both an optimization of plant operation and dimensioning is carried out, while frameworks of Germany, France and EU27 average are used to elaborate their influence on the optimization process. Compared to conventional heating and cooling, the existing system can reduce CO2 emissions by 37% in optimal operation. Through the technically possible operating modes of the realized system, there is a range in annual costs from 213 to 287 k€ and CO2 emissions from 148 to 235 t/a between the optimal and worst control. By adapting the plant concept and a downhill simplex method for identifying optimal storage dimensioning, the economic efficiency of the process can also be significantly increased. Moreover, the configuration of the optimal ICES realization shows a high dependency on the prevailing boundary conditions. For all considered regions, the use of ICES can lead to an ecological improvement as well as a reduction in demand-related costs, whereby the methodology can also be applicable to other building types in the future.