Portable Air Conditioners

Most portable air conditioners are designed to cool a small space, usually just two or three hundred square feet.  Cooling an entire home would require several units.

A characteristic to look for is wheels.  If a portable air conditioned is designed for a single room, it may be needed in one place in the day and in another at night.  People may gather in a kitchen or in a den while awake, but retire to a bedroom at night.  Wheels make it easier to move the unit, since many are heavy.

Portable air conditioners are designed for temporary relief, so many are less efficient than other units.  The inefficiency is manifest in more energy being consumed than might otherwise happen.  This is probably a necessary to keep the cost down.

Portable air conditioners are more often noisy.  A free standing unit can be subject to vibrating when operating.

Most portable air conditioners require a window that can be opened.  This is not always something available, especially in an office building.

Some portable air conditioners, those that operate using evaporation, may avoid some of these problems, but other things need be considered.  Evaporation air conditioners are covered below.

Some units use ice cubes and evaporate the chilled water.  These have some advantages over units with a compressor.  First, there is no need for a window that opens.  Second, they are more energy efficient, and may cost little to operate.  Finally, they can be quiet.

Before you jump in think.  They require ice cubes.  If there is a power outage, and you have a back-up battery for your air conditioner, will you also be able to make ice cubes?  Do you really want to open the freezer?  And how long will those ice cubes last?  And, do you really want to change the water from melted ice and replace it with ice cubes in the middle of the night?

These units might be right for you, especially in a heat wave where there is no power outage, but do understand the limitations.

Perhaps the one real positive here is the much lower price for an item used on an emergency basis.

So, how do these units work?  When water evaporates it takes some energy to change from liquid to gas.  In fact, it takes a lot of energy.  Additional energy is absorbed by melting ice to the liquid state.  That energy comes from the air, having a chilling effect.  But, dehumidifying to avoid excess humidity releases heat back into the air, so either you will have increased humidity or work against the cooling effect. 

Heat is a form of energy.  Basic physics teaches that energy is conserved.  So, if we cool a room where does the heat go?

The cooling process does not destroy the heat.  Instead, it removes the heat from the air that remains in the room.  This is why there must be a window to vent the heat to the outdoors. 

Some small units, those designed for a small personal space, do not vent the heat.  These are not large enough units to do much, and the heat must be considered.  If cool air is forced in one direction, and hot air in another, it is wasted effort after the air mixes. 

During a power failure a portable air conditioner can only work if it has a battery.  It is important to use a compatible energy source.  If your air conditioner requires alternating current, make certain the battery has a way to convert direct current to alternating current.  Fortunately, such batteries do exist.

As global warming alters the thermal profile of the planet, unusual weather, including unbearable heat, is possible.  Be prepared in advance.  Otherwise, portable air conditioners may be scarce. 

Many portable air conditioners also can function as dehumidifiers.  And some can be switched to become heating units.  This makes one device have multiple uses, solving more than one problem.

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