Solar Air Conditioning

Have you always wanted to cool your home/camper/truck/tree-house with solar power?  Who am I kidding, of course you have.  Luckily there is a product on the market from Securus systems that will make it easier to do so.

The Securus climate control products use DC voltage to run the electronics.  In order to use a solar panel to power an air conditioner, you have to connect your solar panels to a battery bank, and then connect the battery bank to the air conditioner.  If you are using an AC powered air conditioner, you need a DC-AC converter between the battery bank and the air conditioner.  The advantage of using DC electrical power for your air conditioner is that you don't need a DC-AC converter and so you minimize electrical losses, cost, and complexity in your system.   If you only have an AC powered climate control system, you can see some examples of DC-AC converters at Mr. Solar.

A schematic of the Securus 48V-DC system is below.

From the PDF brochure for Securus systems states:

The 18000 BTU, (1.5 Ton), certified, 48‐Volt direct current Securus system silently cools and heats an average 600 square foot space by remote control using non‐ozone depleting 410A refrigerant and a brushless, direct current compressor. Movement and automatic temperature maintenance logic ensures maximum efficiency.

Since the 18,000 BTU Securus unit cools and heats, it actually seems to be an air-source heat pump, not an air conditioner.  A heat pump works in a similar fashion to an air conditioner; it's just that an air conditioner only works in one direction: taking heat out of your home.  A heat pump will do that in the summer (acting like an air conditioner), but it will also add heat to your home in the winter!

From the DOE Energy Savers Heat Pump guide (which has a great introduction to what a Heat Pump is and where it works):

For climates with moderate heating and cooling needs, heat pumps offer an energy-efficient alternative to furnaces and air conditioners. Like your refrigerator, heat pumps use electricity to move heat from a cool space into a warm, making the cool space cooler and the warm space warmer. During the heating season, heat pumps move heat from the cool outdoors into your warm house; during the cooling season, heat pumps move heat from your cool house into the warm outdoors. Because they move heat rather than generate heat, heat pumps can provide up to 4 times the amount of energy they consume.

In order for the Securus air-source heat pump to both heat and cool, it uses a 4-way valve to change direction of refrigerant depending if it is heating or cooling.

Flow Diagram of Heating/Cooling Cycles

While I have no clue how well the product works (I'm not thrilled with their website), I think DC powered cooling and heating products could simplify solar powered climate control systems.  As we've said often on Mapawatt Blog, heating and cooling are the greatest energy hogs for most people, so the sooner (and simpler) we can power those systems with clean energy, the better!

Has anyone had experience with a DC powered heat pump unit?

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Another company offering solar air conditioning
Here are a few other companies offering similar products: I am looking forward to adding one of these to a Travel Trailer and Living off the grid in more comfort in Texas.

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