Heating and Cooling System
Hundred percent of cooling load and 50 % of heating load are covered by geothermal heat pump system. The main heating and cooling source of the Manitoba hydro building is exposed radiant concrete ceiling slabs. The water pumped in the tubes that are embedded in the concrete floor slab heats and cools the spaces by thermal radiation. This water system provides better comfort and uses less energy in comparison with air heating system.
The radiant heating and cooling slabs are located in the office space. However, the excess energy can run through the water gardens and the buffer zone in the double-skin fa?ade to maintain temperature and reduce the heat loss (Figs. 7.11 and 7.12).
There is a closed loop system consisting of 280 boreholes, 6 in. in diameter, 400 ft deep, spread between the building’s foundation piles and caissons. Each bar hole contains glycol that extracts the heat from the building and returns it to the ground during the summer time and the flow is reverse during the winter season.
Fig. 7.13 Displacement ventilation, © photo by Terri Boake
Conditioned water is circulated in tubes in radiant cooling slabs, providing 100 % of the temperature conditioning. Through this radiant heating system, the geothermal installation provides approximately 60 % of the heating in the radiant slabs.
Displacement ventilation introduces air at very low velocity at floor level via raised floor system. Air rises and moves gradually as it warms up by the internal loads (i.e. occupants and office equipment). This system is more efficient than over head mechanical system as it only provides air at the level of the occupants. In this system the conventional ducts under the ceiling can be eliminated (Fig. 7.13).
Energy consumption analysis of the building was compared to similar energy benchmark. This comparison shows that the building’s projected performance surpasses those benchmarks. The total annual thermal energy consumption ranges between 105 and 128 kWh/m2 . It is important to mention that these figures fall
Fig. 7.14 Performative analysis by KPMB
below all benchmarks including fully air-conditioned offices (190 kWh/m2), offices mechanically ventilated and heated but not cooled (160 kWh/m2), and most surprisingly naturally ventilated office buildings (135 kWh/m2) (Gon§alves 2010).
Two years of optimization of energy performance led to an unexpected result considering the extreme climatic conditions. All the optimization strategies resulted in reduction on energy loads. The first year operation cost was 161 kWh/m2 and that reduced to 85 going beyond the target of 120, which in comparison with the benchmarks is 70 % better (Fig. 7.14).