Air-conditioning For Sleeping
The Sun Frost “Sleep
a hot humid climate, keeping comfortable by passive strategies is often
difficult and sometimes not possible. Passive strategies, such as high
ceilings and large operable windows to increase ventilation, can make
conventional air conditioning more difficult because of increased heat
gains. Sun Frost has developed an air-conditioner to provide comfortable
sleeping conditions even in an airy uninsulated building. The strategy
to accomplish this feat is to create a relatively small, insulated space
around the bed. This space can then be air-conditioned and dehumidified
with a very small air-conditioner. A diagram of the air-conditioner and
enclosure is shown in the accompanying figure. Here the structure is installed
over a small single bed. Since cold air is heavier than hot air, the space
above the occupant’s head can be left open.
The compressors we are currently
using to power the cooling system can be run off either a 12-volt or a
24-volt battery bank. We will also be building a 120-volt model. The typical
load in a 12-volt system will be about 7 amps or 84 watts. With 8 hours
of sleep, the nightly electrical load at 12 volts will be about 56 amp-hours
or 672 watt-hours. To power this air conditioner with photovoltaic panels,
a 200-watt array would typically be required.
In addition to homes, this concept
could find wide application in long-haul trucks with sleeper compartments.
Currently, drivers idle their trucks all night to keep cool in hot weather.
This burns up about 1 gallon of diesel fuel per hour and causes a great
deal of noise and air pollution. Idling trucks all night is becoming illegal
in a great many states for these reasons. With Sun Frost’s “Sleep
Genie”, idling would not be necessary because the air-conditioner
could be run off the truck’s starting batteries.
In some tropical countries like
Singapore, many of the buildings are concrete and use no passive strategies
for cooling. As a result of poor design, heat from sun-baked walls will
begin to penetrate into an apartment several hours after sunset creating
the most uncomfortable conditions as you are getting ready to go to bed.
In Singapore, air-conditioners are often only used at night to make a
bedroom more comfortable. Instead of cooling a high thermal mass, uninsulated
space, a task air-conditioner like the “Sleep Genie” would
be a much more energy efficient solution. Of course, it would make the
most sense to combine strategies, incorporate the “Sleep Genie”,
insulate the building and put windows in the most appropriate locations
with effective shading devices and then use the “Sleep Genie”
when necessary. “Task” air conditioning is a simple strategy
for cutting the air conditioning electrical loads for the 1/3 of your
day you are off your feet and making solar cooling more practical.
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