The weather forecast calls for hazy, hot and humid but if you're like many people, you only notice it as you walk from your cooled house to your cooled car to your cooled office. What would you do during the summer months without your solar powered air conditioner?

American homeowners spend more than $15 billion on home cooling, and roughly 5 percent of all the electricity produced in the United States is consumed by conventional air conditioning units. All that cooling releases an estimated 140 million tons (127 million metric tons) of carbon dioxide (CO2), a greenhouse gas known to contribute to climate change.

Greenhouse gas emissions have increased by 25 percent in the 150 years since the industrial revolution. Today, fossil fuels supply 85 percent of the energy consumed in the United States; burning petroleum and coal are responsible for 80 percent of CO2 emissions in the United States.

Demand for air conditioning is expected to grow as temperatures increase. Heat waves cause blackouts, health problems and in some cases even death -- during the summer of 2003, at least 35,000 people died from a heat wave that baked Europe. Seven of the eight hottest years on record happened since 2001; the 10 hottest years have all been since 1995. Global surface temperatures have increased by 1.4 degrees F (0.8 degree C) since 1920, and scientists predict temperatures could increase an average of 2 to 11.5 degrees F (1.1 to 6.4 degrees C) by the end of the 21st century].

Reducing the use of fossil fuels and replacing them with renewable resources for energy is key to putting the brakes on the effects of climate change. The only option for reducing the energy consumed by air conditioning has been to simply turn it off -- until now. Solar air conditioners take advantage of the sun at its brightest and use its energy to cool you during the hottest part of the day.

Environmental Benefits of Solar Air Conditioners

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.