OPTIMAL HEATING-SYSTEM RETROFITS IN RESIDENTIAL BUILDINGS

The optimal heating-system-retrofit strategy for existing buildings di ffers due to varying prices of energy, building and installation featu res, climate conditions, etc. We have examined a test building situate d in Linkoping, Sweden. By using the OPERA model, we were able to arri ve at the optimal retrofit strategy, which includes a ground-coupled h eat pump using electricity to run the compressor. Unfortunately, the p rice of electricity differs according to the time of day, month, etc. These variations are not included in the OPERA model. In OPERA, the pr ice should be divided into 12 segments, one for each month of the year since climate data are divided in this manner. Fine tuning of a dual- fuel system (an oil-fired boiler handles the peak load and a heat pump the base thermal load) is optimized using the Mixed Integer Linear Pr ogramming (MILP) method. Adding a hot-water accumulator also makes it possible to use low electricity prices for space and domestic hot-wate r heating. This system competes in the model with traditional heating devices such as district heating. The optimal method of heating the bu ilding was found for using the heat pump alone. (C) 1997 Elsevier Scie nce Ltd.