Solar panels are the most well-known and powerful way to capture solar energy, but there are lots of other ways you can harness the sun to make your life even greener! Solar water heaters and active solar heating systems can use the sun’s thermal energy to provide water and/or space heating, and a wide range of equipment including attic fans, water pumps, and device chargers can use small PV panels to provide power to equipment not connected to your household electricity system.
Solar Water Heaters
The thermal energy of the sun can be efficiently harnessed to heat water for household use, replacing some or all of the output of gas-fired or electrical conventional water heaters. Solar water heaters consist of a solar collector to concentrate the sun’s heat (which may utilize a variety of designs including flat plate and evacuated tube systems), one or more storage tanks, and, in some cases, active pump and circulation systems. The proper design and sizing of a solar water heating system will depend on the amount of hot water you use, the climate where you live, and other factors. The U.S. Department of Energy’s Energy Saver portal is a good resource to learn more about your options.
While solar water heaters have a higher up-front cost than conventional water heating systems, they can reduce your monthly water heating bills by 50-80%, which can make the economics very attractive – especially if you’re building a new home or refinancing a home, which allows you to take advantage of a federal income tax deduction on mortgage interest attributable to the system. The Department of Energy also has more information on the economics of solar water heaters and how to estimate your potential savings.
Active Solar Heating
Solar thermal energy can also be used to provide household heating for interior spaces via active solar heating systems. Liquid-based active heating systems use solar collectors very similar to solar water heaters, and circulate a working fluid such as water or anti-freeze through a system of pipes, radiators, and/or hot-water baseboards to radiate heat throughout a room. These liquid-based systems may also include storage tanks to enable the hot working fluid to be used after the sun goes down.
Alternately, solar heating systems may utilize air as a working medium instead of a liquid. In this case, an air collector with a glazed, black metal plate absorbs sunlight to heat the air, which is subsequently pulled into the house with an electric fan or blower. In general, solar air heating systems are less efficient than liquid-based systems, but they produce heat earlier and later in the day and don’t avoid operational risks of fluid leakage or freezing.
Like solar PV systems, active solar systems are generally sized to provide some but not all of household heating needs, relying on conventional heating systems for backup. They are generally most economic in cold climates with good solar resources and high heating fuel costs, and their cost-effectiveness is increased when integrated with solar water heating systems. Once again, the U.S. Department of Energy’s Energy Saver portal is a handy resource for more information.
Solar Attic Fans
Solar attic fans work by pulling hot, humid air out of attic spaces to reduce climate control costs. Because hot air rises, the air inside an attic can reach temperatures far exceeding ambient outdoor temperatures, increasing central air conditioning loads during summer months and leading to excessive condensation in attic woodwork and insulation during the winter. Solar attic fans are roof-mounted electric exhaust fans powered directly by a connection to a small PV panel that is not connected to the household electricity system, making them much easier and less expensive to install and integrate than a full-fledged home solar system.
Solar attic fans are available in a variety of specifications and strengths from a wide range of manufacturers, and are typically rated for airflow and speed using a cubic feet per hour value to indicate how much air they’re able to replace over time. They are also available in many different form factors, with low-profile units available for particularly windy areas, high-profile units that are less likely to be buried by snowpack on the roof and tilted angle units available to optimize the solar panel’s access to the sun. Since the solar panel is only capable of generating electricity during the day, homeowners who wish to replace warm air with cooler air overnight will need to consider a battery array installation, which will store power collected during the day to keep the attic fan operating once the sun has set.
Solar Water Pumps
Solar water pumps use solar PV panels to power an electric motor for pumping water instead of grid electricity or diesel generators. These pumps can be sized for a wide range of applications, from small wells or garden fountains to larger agricultural irrigation systems, and the amount of power required will determine the number PV panels and their arrangement. Climate Wiki has more information on different types of solar water pumps and how they compare to conventional alternatives.
Like household solar PV systems, solar water pumps have a higher up-front cost than conventionally-powered systems but can potentially save money over time because their operating costs are essentially zero. With no moving parts, PV panels also require far less maintenance than conventional generators. The economics of solar water pumps can be particularly compelling in areas that lack access to grid electricity, where the alternative is continually refueling generators with often-expensive diesel fuel.
Portable Solar Chargers
Beyond using solar energy to reduce the carbon footprint of your home, there are also a growing number of portable solar PV charging devices available to help you stay green on the go. These devices are designed and sized for a wide range of number of purposes, from backpacks with flexible PV panels capable of charging cell phones and laptops to larger mobile systems capable of providing power for campsites or off-grid housing. Simpler, smaller systems only provide power when the sun is shining, while others charge a battery to ensure electricity is available at all times – a particularly important consideration for larger systems designed for providing backup power in emergencies.