Building Integrated Thermal Energy Storage Systems

A ventilated concrete slab (VCS) was designed to be used as thermal energy storage. The slab has implemented air channels inside and can be charged either by air source heat pump or building integrated photovoltaic and thermal (BIPV/T) system. Multiple charging scenarios with different air temperatures, air velocities, concrete temperatures, etc., were studied to identify the effectiveness of the VCS. It was shown that the average concrete temperature increased up to 12.2^oC when charged directly by BIPV/T system while it increased up to 18.7^oC when an air source heat pump was used to charge the slab. It was also shown that decrease in the air temperature after passing through the channels highly depend on the air velocity and its source temperature.

Next, an insulated concrete form (ICF) wall was designed as thermal energy storage to be charged through single or double pipe hydronic system when there is excess, or free, or inexpensive energy available. The heat source for charging the ICF is either heat pump or solar thermal collector system. Various charging cycles were modeled and advantages and disadvantages of the ICF thermal energy storage were investigated. It was shown that the maximum of 2,195 kJ can be stored in each single ICF block when charged with heat pump during a six-hour cycle. However, the same ICF block can be charged as much as 2,866 kJ using four flat plate solar collectors in series with 0.02 kg/s mass flowrate.

A typical townhouse model and a bungalow house were modeled using building energy simulations. These models were used to estimate how ICF thermal storage can cover the thermal loads of the buildings. Simulated results showed that as much as 284.5% of the total heating demand of the townhouse and 246.4% of the heating load of the detached house in Toronto weather condition was covered using the solar collectors to charge the basement walls of these buildings. Similarly, using the heat pump to charge the basement ICF walls resulted in storing more than 88 kWh in the townhouse and 140 kWh of energy which was more than two times required heating demand of the buildings.