Civil Engineering Reference
In-Depth Information
Fig. 7.8
ÉcoTerra system schematic (Chen, Athienitis, and Galal, 2010a)
To supplement the heating contribution from the passive solar heat gains
and the BIPV/T system, the ÉcoTerra house includes a two-stage
ground-source heat pump (GSHP) with an 11.1 kW thermal output capacity.
The coefficient of performance (COP) of the GSHP was measured to be
between 3.5 and 4.0 - slightly below the rated COP of 4.2 at full load.
Theheatpumpiscontrolledtooperateinzero,one,ortwostagesdepending
on the outdoor temperature and the apparent heating load (as determined
bytheamountoftimerequiredtoreachtheheatingsetpointoncetheindoor
air temperature falls 1 °C below the setpoint). There is also an auxiliary
heater (electric resistance) if the heat pump, alone, is deemed insufficient
for achieving the heating setpoint. Operating in this mode is very
undesirable because the COP effectively declines to 1.0 - an efficiency loss
of about 75%.
Heating is distributed to all conditioned zones of the house via ducts using
a forced-air system. The distribution fan has three rates: 355, 495, 590 l/s.
The house is controlled as a single control zone for heating and cooling,
based on the temperature on the main level of the house. However, a
motorized damper prevents heat from being delivered via ducts to the
bedrooms if overheating is detected. This quasi-single zone configuration
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