In 1990 Damark International, a national mail order firm based in Minneapolis, was advertising for $699.99 ("manufacturer's suggested retail price $1,199.00") the Bionaire Cold Front Portable Air Conditioner, a "free-standing portable unit" which "does not require outside venting."
This appliance was intended to be rolled from room to room by the user,
who could simply plug it into an ordinary 110-V AC outlet and enjoy the
cool air from its "Cold Front." It was claimed to provide 5,500 Btu/hour
cooling capacity for 695 watts by drawing 6.3 amperes of electric current.
This advertisement can be used to think about energy principles and
1. It can be checked whether 695 W is consistent with 6.3 amperes
and 110 V.
2. The heat removed from the air blown out the front,
5,500 Btu/hour, can be calculated to be 1,612 W in SI units, making use of
the conversion factor 1 Btu = 1055 joules.
3. The coefficient of performance (COP), the ratio of heat removed to energy supplied, is then
Although the COP is a dimensionless quantity, air conditioners in the U.S. carry labels giving the COP as an "Energy Efficiency Ratio" (EER) in mixed units of Btu per watt-hour, so the EER of this unit is
This is on the
low side, since efficient window air conditioners can have EER values of 10
or higher; in fact, it does not meet current national minimum standards.
4. Heat must be rejected at the rate of
Presumably this is not out the "Cold Front," so it must be out
an unadvertised "Warm Back."
5. This air conditioner has the net effect, while its compressor is running, of providing
to the room in which it is used. So this
air conditioner, because it does not vent the exhaust heat outside, is really
a heater! Perhaps during the winter the unit could be sold as a portable
heater, with users facing its "Cold Front" away from them! Of course, its
price of $739.99 (including shipping) is an order of magnitude greater than
that of commonly-available electric resistance space heaters.