Active solar heating systems are increasingly becoming a trend in residential settings nowadays. As the name suggests, it takes advantage of an infinite and sustainable source, which is solar energy. What it does is it heats either air or liquid before transferring the product (solar heat) to the interior space for use. For the most part, this system comes equipped with a storage system in case consumption is lower than the produced solar heat. In times when the solar energy system fails to produce enough for space heating, a home usually has a backup system that provides the additional heat. Some small and medium-sized residences use space heaters as backup. On one hand, a liquid-based system is preferred when storage is integrated. The same system is best for radiant heating systems, absorption heat pumps and coolers, and boilers paired with hot water radiators. It is important to note though that both liquid and air-based systems are capable of supplementing conventional forced air systems.
More about Liquid-Based Active Systems
If you have a conventional central heating system at home, you should know that a solar liquid collector is a perfect complement to it. These collectors are practically the same to those components used in solar domestic water heating systems. The most common variety is the flat-plate collectors, although you also have the option to choose either the concentrating collectors or the evacuated tube.
In this system, a heat transfer or working fluid like an antifreeze or water will absorb the solar heat. In a perfectly timed manner, the controller will then operate a circulating pump, the purpose of which is to move the fluid through the collector. As the liquid flows in rapid fashion, temperature increases to a limited range, usually from 10° to 20°F (5.6° to 11°C), while moving through the collector. If there is a smaller volume of liquid that’s heated to higher temperature, what happens is that there is a tendency of losing heat from the collector, thereby rendering the system inefficient. The liquid will find its way to the storage tank for use later, but for the most part, a heat exchanger receives it for immediate use.
Heat Storage in a Liquid System
One of the most interesting things about active solar heating in liquid-based systems is that solar heat is stored in tanks of water, or in some situations, in the masonry mass of a radiant slab system. For a tank-type system, heat produced from the working fluid is transferred to a distribution fluid in a heat exchanger exterior. Sometimes, it is done within the tank. The storage tank can either be pressurized or non-pressurized. The choice really depends on the design of the overall system.
When choosing the ideal storage tank, there are certain factors you must consider, including the cost, durability, quality, size, and where you plan on placing it. In some instances, it is conveniently located in the basement. But if there is no space, it usually is placed outside of the house.
Heat Distribution for Liquid-Based Systems
There are several ways to distribute heat using a solar-heated liquid. The most common are the radiant floor, central forced-air systems, and hot water baseboards or radiators. One of the simplest is by way of radiant floor heating in which solar-heated liquid will circulate through the pipes installed in a concrete slab floor. In fact, radiant floor heating and liquid solar heating systems are a perfect match because they allow for the production of heat at very low temperatures.
Furthermore, if a system is designed with utmost accuracy, there is a chance that the need for a separate storage tank is eliminated. However, it also is worthy of mention that majority of modern systems still use tanks since they make it easier when it comes to controlling temperature.
Finally, a liquid-based system can also be incorporated into a forced-air central heating system. The most basic setup includes that of placing a heat exchanger or heating oil in the main room air return duct before reaching the furnace. When air returns from the living space, it is heated as it passes through the solar heated liquid. The furnace is then responsible for supplying additional heat as needed.