Spring/Fall or at Night (Mild Weather)
Energy
Savings Illustrated
(The A/C Is OFF)
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The Indoor R/F must
transfer heat from its inside (at 42° F) to its outside (at 72° F). This temperature gap
is: 72 - 42 = 30° F |
The Window R/F must
transfer heat from its inside (at 42° F) to its outside (at 52° F) This temperature gap
is: 52 - 42 = 10° F The workload on the Window
R/F is much less (1/3), resulting in energy savings, higher efficiency
(COP) and prolonging the R/F's life.
In addition, since a part of the Window R/F is outdoors, it (the
insulated box) gains heat more slowly resulting in additional energy savings. |
Obviously this simple demonstration excludes the additional energy savings due to:
1. freezing water at night (cooler than day) behind the R/F and letting the ice melt during the day (hotter than night) to keep the R/F cool. This energy savings is due to the enthalpy of fusion of water. It also reduces the electricity demand on the city's electric grid during the peak hot days of summer.
2. Letting the cold outdoor air into the R/F during cold nights to cool it for free without electricity.