Civil Engineering Reference
In-Depth Information
Most thermally driven cooling technologies are geared toward producing
chilled water, with the exception of the desiccant systems. The performance
of EC, CVA, OVA, and adsorption systems is strongly dependent on the
generator (hot side) operating temperature. This poses a significant
disadvantage for solar thermal systems compared to fossil fuel powered
systems. The performance of desiccant systems, however, is not strongly
dependent on regeneration temperatures and allows for the independent
control of the latent and sensible loads; an increasingly important feature
with present higher ventilation standards and indoor air quality concerns.
Another advantage of liquid-desiccant systems is the potential of using the
desiccant solution for energy storage.
2.2.4.2 Solar Assisted/Source Heat Pump Systems
Heat pumps may be used either in parallel with a solar system to act as
a source of auxiliary heating/cooling or in series with the solar system.
Parallel application of heat pumps is usually straightforward since usually
each system operates independently. The feasibility of using a parallel
source heat pump then largely becomes a matter of the economics of
competing auxiliary energy systems and may be influenced by local climatic
conditions.Smallheatpumpsystemsarerequiredtooperateefficientlywith
the reduced loads experienced in Net ZEBs. The use of a heat pump to
enhance the heat transfer from a solar collector to the thermal storage can
improve overall performance over a wider range of seasons and weather
conditions.Combiningheatpumpswithconventionalsolarsystemsalsohas
the potential to produce high energy output from low-cost unglazed solar
panels (Bridgeman and Harrison, 2008).
The example in
Figure 2.25
(Candanedo and Athienitis, 2011) shows the
possible utilization of a BIPV/T air system connected to an air-to-water heat
pump in order to heat water in a thermal energy storage tank that can be
used to heat room air or a floor (e.g., floor heating). The heat pump can also
coolthewaterduringthecoolingseason,butinthiscaseitwouldmakemore
sense to directly draw air from outside as opposed to the BIPV/T system.
Also. if the air from the BIPV/T is too hot, it might be preferable to use it
first through an air-water heat exchanger and then through a heat pump.
The addition of storage can serve to displace heating and cooling needs
by converting solar electricity that the grid may not be able to take (due
to high penetration of PV; for example in neighborhoods) into about four
times as much useful stored heat or cool. The addition of storage will of
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