Active Solar Space Heating: A Tutorial
Photo credit: http://www.acrux.hu/sun/pic/kollektor_teton.jpg
The summer sunshine sure is sweet, and warm and inviting. But the sun still shines in winter, and even at night if you factor in the solar heat you’ve gathered during the day to heat your living space. Solar energy has a wide array of applications for home use, not least is solar space heating.
Solar space heating may be active or passive, the only difference being the use of mechanical blowers or fans to “actively” distribute heated air throughout the home. Within the category of active space heating there are two subcategories: liquid-based and air-based systems.
Site Assessment
The first step in any solar energy installation process is site assessment. That is evaluating your home and region for its solar energy potential based on location and climate. The good thing about solar space heating is that the colder the climate in which you live, the more need for solar space heating. And considering that solar space heating is a solar thermal application (collecting solar heat rather than directly converting radiation to electricity), the system will even work to some extent on cloudy days.
A site assessment will entail the sizing of the solar thermal heating system (i.e., amount of heat needed, monthly energy usage, etc.). It will also include determining which type of solar thermal collector to use. The vast majority of solar heating applications utilize flat-plate collectors.
Liquid-based Heating
A liquid-based solar space heater involves a flat plate collector, which collects solar heat via a flat, black plate beneath a layer of glazing, that in turn heats water or an anti-freeze solution (transfer fluid) that runs through tubes installed next to the plate. In a closed-loop system, those using antifreeze, a pump is used to continually circulate the liquid through the collector.
That transfer liquid passes at some point through a heat exchanger that transfers collected solar heat to water which is then directed to point of use. For active space heating, that heated water usually sent through tubes running in or under the floor as part of radiant floor heating system.
An open loop system will send the water directly to the collector and back to the home in a continuous cycle.
Air-based Heating
Air-based heating excludes any liquids. Instead it utilizes a fan or blower to move cool air through the solar collector, where it is heated, and then into the home’s central air system or into an air-based radiant floor system to heat the home.
Air systems are not susceptible to freezing temperatures but are less efficient than water at retaining heat. In some cases the solar heated air will have cooled significantly before it has time to reach the living space. Water, although prone to freezing (hence most cold climate citizens use closed-loop systems), is much better at storing heat.
Finances
Issue number one for most people is financing. And it is true that active solar space heaters will be significantly more expensive up front that conventional or passive systems. But like any other solar application it is an investment that will reap rewards in the long run.
There are also federal incentives available that will knock up to 30 percent off that price tag in tax rebates. In most cases there are state incentives as well that can further reduce those costs. And in rarer instances, utilities or local municipalities may also have financial incentives available.
Active solar space heating systems are not a DIY project for the vast majority of homeowners. They can be complex and will require rare but regular maintenance (transfer fluids must be changed roughly every 3-5 years). Therefore, initiating contact with a local solar thermal installer is the best move you can make, even if active space heating is still just a consideration. Free estimates are not difficult to come by.
Posted on July 21st in Solar Information by Dan.