Conventional air conditioners running at the hottest points of the day contribute to power grid demands that often lead to outages. Solar air conditioning units offer environmental benefits including lower grid demand and load shifting during peak usage, reduced electricity costs, fewer power outages, off-the-grid capabilities and reduced greenhouse gas emissions.
Solar air conditioning units come in two basic flavors: hybrids and chillers.
A hybrid system combines photovoltaic technology (PV) with direct current (DC). It automatically switches between solar and battery power as needed. When it's set to hybrid mode, these systems charge their batteries when the sun is shining; when it isn't, the system runs on battery backup while charging its batteries via alternating current (AC) power.
GreenCore Air, for example, designed its solar-powered air conditioner to work either completely off the grid or as a hybrid solar/battery air conditioning unit. It is powered by a single 170-watt solar panel, runs on DC power and has the capacity to cool about a 600-square-foot (55-square-meter) room.
Solar-powered absorption chillers, also known as evaporative coolers, work by heating and cooling water through evaporation and condensation. Chillers cool the air by blowing it over water-saturated material -- solar energy is used to power the fan and motor. SolCool's hybrid solar air conditioner, for example, runs on solar energy, can be plugged in or can run off of batteries. Even when plugged in to a conventional power source, it operates at a maximum of 500 watts per hour, compared to about 900 for a conventional window unit (and 3,500 watts for an hour of central air conditioning). Its chiller option offers air conditioning for hours after a power failure.