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Solar heating is a means of collecting and storing energy, in the form of heat, harnessed from the sun. A passive solar heating system passively collects and transfers that energy. Skylights and greenhouses are examples of passive solar heating systems because they passively accept solar heat in but do nothing to actively enhance that process. Active solar heating, on the other hand, actively enhances the collection, storage or transfer of that energy. Active solar heating systems use fans and pumps to distribute the collected heat.
The collectors in an active solar heating system are typically made of silicon-based solar cells, also known as photovoltaic cells, which absorb the sun’s light. Solar panels, made up of solar cells, are usually installed on the roof of a home or a building; the larger the number of cells, or size of the panels, the greater the solar radiation.
There are two general types of active solar heating systems. The difference between them is based on the substance that is used to collect and transfer the heat in the solar collector. This substance is usually either liquid or air. Liquid-based systems, also known as hydronics, typically use water or an antifreeze solution to collect and transfer heat. Steam and hot water radiators are one of the oldest forms of hydronic heating systems. Air-based systems typically come in one of two forms — air room heaters or transpired air collectors. Both heat rooms, but do so via different mechanisms.
Whether the solar heating system uses air or liquid, the collectors are usually installed on the roof of a building or home. The stored energy, however, in liquid-based systems is typically housed in the basement or some other lower level location.
Active solar heating systems may be connected to the general power grid and in some cases, if the system produce excess solar energy beyond what a household needs, it may be sold back to the public utility. The goal of an active solar heating system is to heat approximately 40–80 percent of an interior space. Ideally, an active solar system should combine functions—heating air and water—thus enabling the system to work year round.
In abundantly sunny areas, an active solar heating system can greatly supplement electric, propane, or oil derived heat and greatly reduce heating bills. Although installation costs can be high, more and more governmental bodies are offering tax exemptions, credits, and deductions to encourage individuals towards this environmentally-friendly option.
Frequently Asked Questions
What is active solar heating and how does it work?
Active solar heating systems use solar energy to heat a fluid—either liquid or air—and then transfer the solar heat directly to the interior space or to a storage system for later use. If the solar system cannot provide adequate space heating, an auxiliary or backup system provides the additional heat. Solar heat is absorbed by panels or collectors, and a pump or fan distributes the collected heat.
What are the components of an active solar heating system?
An active solar heating system typically includes solar collectors, a circulation system (pumps or fans), a heat storage system, a heat exchanger, and controls. The solar collectors capture and absorb solar radiation, the circulation system moves the heated fluid, the storage system holds the heat for later use, and the controls regulate the system operation.
How efficient is active solar heating compared to other forms of heating?
Active solar heating can be highly efficient, with some systems converting up to 80% of solar radiation into usable heat, according to the U.S. Department of Energy. However, efficiency depends on factors like collector design, system sizing, and local climate. It's generally more sustainable than conventional heating methods, as it reduces reliance on fossil fuels and lowers greenhouse gas emissions.
Can active solar heating systems provide cooling as well?
While active solar heating systems are primarily designed for heating, they can be adapted to provide cooling through solar absorption chillers or desiccant cooling systems. These systems use solar heat to drive a cooling process, offering an environmentally friendly alternative to traditional air conditioning, though they are less common and can be more complex to install.
What is the cost-benefit analysis of installing an active solar heating system?
The initial cost of installing an active solar heating system can be significant, but the long-term savings on energy bills can offset this. The payback period varies based on local fuel costs, system efficiency, and available incentives. According to the U.S. Department of Energy, well-designed systems can cut heating costs by 50-80%, making them a financially viable option over time.
Are there any government incentives available for active solar heating systems?
Yes, there are often government incentives available for installing active solar heating systems, such as tax credits, rebates, and grants. In the United States, the federal solar investment tax credit (ITC) allows homeowners to deduct a percentage of the cost of installing a solar energy system from their federal taxes. Additionally, state and local incentives may also be available.