What is a solar air conditioner?

What is a solar air conditioner?

Solar ACs can be a great low emissions alternative to traditional cooling. Essentially, they refer to any AC system that is powered by directly by solar energy.


Cost

Capital outlay: High upfront cost for the time being given the immaturity of the technology, but cost is expected to come down & energy efficiency to increase in coming years as the tech improves. Currently, the system costs around $4,000 to install, including having solar panels fitted –four to power a small unit, and up to eight for a larger unit.

Operating: Solar ACs can bring your cooling bills down to about 10c a day, and don’t require an existing PV system (similar to solar hot water). There's no need for inverters or charge controllers as they work directly and will power on during the day when there’s sunlight, and power off when the light fades, and it becomes naturally cooler.

Savings: Because they work independently of the grid, you can leave them on all day without worrying about the cost. Savings over the lifetime of the units could be between $8000 and $30,000 (reportedly)


The tech explained:

There are 2 types of solar ACs

-          Conventional Solar Powered Cooling System

Conventional solar air conditioners utilise a standard vapour compression refrigeration cycle to cool or heat the building in question. The principle is that heat in the building is transferred to a refrigerant gas, which is then circulated out to a condenser where the excess heat is dumped. The now cool refrigerant then circulates back into the building to repeat the cycle. A conventional solar AC system draws operational power from a solar array rather than the electricity grid, in an effort to increase efficiency and lower costs.

-          Open-loop cooling (both cooling and heating)- pilot pioneered by CSIRO

Process begins with a typical solar hot water system. A portion of that hot water would be diverted into the solar AC unit, which is divided into 2 compartments. The hot water enters a heat exchanger in the first compartment (similar to a car radiator, the heat exchanger uses the hot water to heat outside air that has been drawn into the first compartment through the vent.) At the same time, outside air is being drawn into the 2nd compartment into a “dessicant wheel” which dries out the air, cooling it down before being released back into the house.

When heating is required, the hot air is instead used to directly warm the house.

If there is no sun or heat to drive the dessicant wheel process, you can mitigate this intermittency by switching into indirect evaporative cooling mode. 

Both systems require some electricity from the grid in order to operate: the conventional Solar Powered Cooling System uses it to power the compression and circulation of the refrigerant gas, and the open loop cooler uses it to power the cooler for the incoming air. With either, you’re drawing less power from the electricity grid, and will therefore use less electricity when you utilise solar air conditioners – provided the unit you invest in isn’t particularly energy inefficient.