Abstract

Peak shifting plays a vital role in easing the stress on electrical grids as well as in reducing the electricity bill for consumers by taking benefit of the time-of-use tariff. In cold climates, this can be achieved effectively by storing the heat in thermal energy storage (TES) systems during off-peak periods and releasing the stored heat during peak periods. In this regard, building integrated thermal energy storage (BITES) systems (e.g. ventilated wall, electrically heated floor (EHF) with high thermal mass (e.g. bricks, concrete), hydronic heated floor etc.) can be used. It is worth stating that a well-designed BITES system can completely shift the load from peak periods to other periods. On the other hand, residential buildings in places like North America face practical constraints on incorporating high thermal mass into each envelope and each room. To overcome this limitation and also mainly to increase the percentage of peak load shifting, the present work proposes a forced ventilation system/heat extraction system (HES) to transfer the additional heat from zones with well-designed BITES system to zones with no such provisions.
In this study, a multistory house, in which the BITES system (i.e. EHF) is mainly installed on the basement floor is developed in TRNSYS and validated using the field measurement data. The validated model is then utilized to evaluate the peak shifting potential of the existing EHF under different heating strategies. It is inferred from the simulation results that the existing EHFs almost had the ability to completely shift the heating consumption in the basement from peak period to other periods). Further, the potential of HES to transfer the heat from the basement to the second floor are investigated in terms of its heating performance (effect of air flow rate and outlet location) and ability to extend the peak shifting potential of EHF. The key finding of the present study is that the HES augments the peak shifting potential of EHF up to 19%. Also, it is inferred that the proposed methodology increases the heating energy consumption by 18% but decreases the daily heating cost by 24%. It should be mentioned that the increase in energy consumption is due to the prolonged operation of the basement EHF during the off-peak period and the decrease in energy cost is because of shifting the peak to the off-peak period.
The proposed concept would be a benefit to both supplier and consumer in terms of peak shifting and heating cost saving. Also, the proposed methodology resolves the constraint of incorporating higher thermal mass in each floor of the residential buildings.