There are two types of active solar energy systems.
These systems operate on a basis where a liquid or air is heated in residential solar panels. (A panel is an energy collector apparatus where the liquid or air is heated by the sun’s energy.)
Liquid-based systems heat water or an antifreeze type solution in a "hydronic" collector, while air-based systems heat air in an "air collector." Both of these types of active systems collect the sun's radiation and transfers heat directly to the interior space of a building or to a storage system.
In those instances where the active solar energy system does not provide a sufficient supply of space heating, the use of a back-up system can provide additional heating requirements.
Liquid systems are most often used when storage is included. These types of systems are appropriate for boilers with hot water radiators, radiant heating systems and absorption heat pumps and coolers. Both types of systems (fluid and air) can be used to supplement/enhance forced air systems.
See accompanying video to see how people have installed and benefited from this renewable energy source.
Economics/Benefits of Active Solar Energy Systems
For an active solar heating system to be cost-effective, is must be used for most of the year where the climate is cold and has good sunlight resources.
In many states, an active system is often sales tax exempt when purchased, can received income tax credits or deductions.
Active solar energy systems will vary in cost. For instance, an installed commercial system can cost anywhere from $30 to $80 per square foot of collector area. A large system will typically cost less per square foot of collector area than a small system.
Active Solar systems many times come with warranties or 10 or more years and can last for much longer than that. When considering the economics of a system, they will improve if the system also heats domestic hot water.
Homes that use active systems can drastically reduce fuel bills during the winter months.
These systems will help reduce the amount of air pollution and greenhouse gases that result from fossil fuel use.
Selecting/Sizing an Active Solar Energy System
There are several factors that need to be considered when selecting a renewable heating system for a home. The site, design and heating needs of the home all need to be considered.
In some localities, covenants may restrict the use of collectors or certain parts of the home and limit options on where they can be placed.
The amount of heat one of these heating systems can provide is based on the local climate, the type and efficiency of the collector(s), and the amount of collector area.
Typically, an economical design for active system is designed to meet about 40%-80% of the home’s heating requirements.
Systems that are designed to meet smaller needs are not often cost-effective. The exception to this is when the use of solar air heater collector is used to heat one or two rooms without heat storage.
For homes that use passive heating techniques and are well designed and insulated, they will require a smaller and less expensive heating system of any type. Many times, very little supplemental heat other than solar is required.
In many localities, building codes and mortgage lenders will not allow an active solar system to provide 100% of the home’s heat. They will require a back-up heating system to supplement the active solar system.
A back up system can be a wood stove to a conventional central heating system.
Active systems designed to provide 100% of the heat are generally not practical or cost effective.
Solar system controls
Active heating systems use controls that are complex and are much more complicated than conventional heating systems. The controls for these systems must monitor signals and control more devices than simpler conventional systems.
An active heating system will use sensors, switches, and/or motors to operate the system. There will also be other controls in use to prevent freezing or very high temperatures occurring in the collectors to prevent damage.
The main control of an active heating system is the differential thermostat. This device measures the temperature differential between the collectors and the storage unit.
Control systems for active heating systems will vary in their complexity, operation, performance and cost. In the more complicated systems, microprocessors (small computers) are utilized to control the heat transfer and delivery to the storage medium or zones within the house.
Separate controls may not be necessary with room air collectors. By not using these controls, it will ensure the active heating system will continue to operate if there should be a power outage with the electric utility.
Active solar power systems that utilized battery storage can continue to operate a central heating system. However, this can be an expensive proposition for larger systems.