Last Updated: Jul 10, 2021
Using the light and the heat from the sun to cool your home might seem a bit irrational, given that the sun is the largest source of heat on our planet. For centuries, the sun has been used as a natural source of warmth for hot water heating and the passive heating of the homes we live in. However, recent technologies have made it possible for homeowners to utilize the sun for the cooling of their homes. Below, we offer a complete guide for using solar panels and solar energy to cool your home this summer.
According to the US Department of Energy, air conditioners account for 6 percent of all energy used in the United States and 12 percent of residential energy usage. With air conditioners in almost nine out of every ten American homes, our homes' artificial cooling accounts for an enormous amount of carbon dioxide emissions (assuming the home sources its electricity from carbon-intensive energy like coal or natural gas, which is how most utilities produce electricity).
Air conditioners are one of the primary sources of hydrofluorocarbons (HFCs) emissions. HFCs are mainly used today in both refrigeration and air conditioning equipment. While HFCs was originally incorporated as a more environmentally friendly alternative to the CFCs that were found to be destroying our ozone layer, today, HFCs are a major contributor to global warming. Why?
HFC emissions are known to be 100 to 3,000 times more potent than carbon dioxide and can stay in the atmosphere for hundreds of years. While HFCs in the atmosphere are relatively low compared to other greenhouse gasses, the primary sources of HFCs come from the manufacture of air conditioners and refrigeration equipment, leakage from these devices, and the end-of-life disposal of these units.
At the same time, air conditioning is a modern-day comfort and convenience that is increasingly necessary in a world affected by global warming. Some reports suggest that the increasing frequency and intensity of summer heatwaves worldwide could send mortality rates from high temperatures skyrocketing by as much as 2,000 percent. So how can we stay comfortably and safely cooler in increasingly hot summers while minimizing the environmental impact of artificially cooling our homes? Remarkably, solar technology offers three different ways to help keep your home cool this summer.
Solar photovoltaic (PV) technology has the ability to capture sunlight and use cells to turn that light into electricity. The PV cell is made up of layers of semiconducting material, with silicon as the preferred material. The light that shines on the cell subsequently creates an electric field across the layers, causing electricity to flow. When combined with energy-efficient home construction methods, solar panels can essentially create a Net Zero energy home or a home that produces as much (or more) energy than what it uses.
Unfortunately, the problem with air conditioning is that it takes a relatively large amount of energy to keep a home cool. Air conditioners are high wattage appliances and require a high current of electricity when the compressor is running. While Energy Star certified air conditioners today use only about half as much energy as those made back in the 1990s, air conditioners continue to be one of the most energy-intensive appliances within the home.
The exact amount of energy used by an air conditioner will depend on the AC unit's size, the quality of home construction, including insulation and building envelope standards, and the outside temperature. However, a 5,000-watt central air conditioning unit would require at least twenty 250-watt solar panels, without factoring in the power loss that occurs when converting the DC electricity from the panels to the AC electricity that the air conditioner requires.
The average central AC unit uses around 5,000 watts of power every hour for an average of nine hours every day during the hot summer months. For an average 5 kW household solar system, the majority of the electricity produced by your solar panel system would go towards the home's air conditioning requirements.
Smaller homes built with more energy-efficient construction practices, such as those developed by the passive house principles, can drastically reduce your home's cooling loads. However, for homes located in hot summer climates, relatively large solar panel systems will be needed for air conditioning needs.
One of the best ways to reduce your home's overall cooling load is by lessening the amount of heat from the sun entering your home. Natural shading strategies focusing on strategic landscaping in your yard can reduce indoor temperatures without relying on artificial air conditioning. Similarly, one recent study found that “neighborhoods with well-shaded streets can be up to 6-10°F cooler than neighborhoods without good trees for shade.” Automated smart window shades, along with high-efficiency windows, can also drastically reduce the heat from the sun penetrating your home.
Residential solar panel systems are usually placed on the roof of homes. A home roof is usually an inconspicuous place for solar panels where high direct sunlight levels are available. However, solar panels can also be placed in other areas around the home. Installing a solar panel as a window awning over a west-facing bay window will offer double duty for keeping your home more naturally cool. Not only will the solar panel produce renewable, clean energy that can be used to power an AC unit, but due to its strategic placement, the panel would also offer needed shade from the hot summer sun.
Though much less common than solar PV panels, the sun's energy can also be used for household cooling needs through solar absorption cooling devices. Absorption chillers are a common type of “solar air conditioner.” These unique devices work by distributing water to many coils or heat exchangers used to cool the air. The cooled air is then distributed throughout your home to lower the interior temperature of the house. Solar-powered absorption chillers are usually connected to solar hot water panels located on the roof of your home. In this way, your sustainable source of hot water supply can also be used for environmentally friendly cooling strategies.
Essentially, the absorption chiller will take the hot water produced by your solar hot water heater and pass it through a chamber in the chilling unit that is filled with silica gel. This gel constitutes a low humidity environment that causes evaporation to occur, thus cooling the water.
These solar air conditioning units have few moving parts and are thus easy to maintain. Solar-powered air conditioners work best in well-insulated homes that also have ventilated attics and windows with high-quality awnings. These systems can also be connected to heat pumps that a solar PV system can further power.
There are several different strategies to use solar energy for cooling your home. Traditional PV panels that can produce power to run a high-efficiency air conditioner, creative placement of those panels, and solar-powered absorption chillers are all innovative ways to stay cool this summer while simultaneously reducing your carbon footprint—and saving money on your electric bill.
Tobias runs an agroecology farm and a natural building collective in the mountains of El Salvador. He specializes in earthen construction methods and uses permaculture design methods to integrate structures into the sustainability of the landscape.