Solar Water Heating Systems
Table of Contents
This infosheet provides farmers and rural residents with options for solar water heating systems, explains current technology and a method for determining whether a solar water heating system is right for you. Also included is information on current incentive opportunities.
Solar water heating systems, first developed at the turn of the 20th century, convert energy from sunlight into heat, which is then used to raise the temperature of water. Solar water heating systems have a high efficiency in the summer, converting up to 80 per cent of the energy that contacts the system into heat. In the winter, around 20 25 per cent of the energy is converted. Smaller systems are suited to providing hot water for residential consumption by preheating water before it enters the normal hot water tank. More extensive solar water heating systems can heat large volumes of water for agricultural applications, like milk production.
Solar collectors for a water heating system come in many forms, and can be mounted on a roof, on outside walls, or on the ground. One common form is the glazed flat-plate collector (Figure 1), in which the water or anti-freeze circulates through a network of copper piping attached to a flat black plate inside a glass-covered frame.
Figure 1. Glazed flat-plate collectors for a on-farm milk processor. Courtesy of Enerworks & Ronnybrook Farms.
Sunlight passing through the glass hits the plate and becomes heat. The heat is trapped by the pane of glazed glass and raises the temperature of the liquid inside the piping.
Based on similar principles, an evacuated tube collector (Figure 2) encases the individual tubes in a layer of glass and creates a vacuum between the two. The glass allows the sunlight to pass through, strike the tube, and heat the liquid while the vacuum insulates the tube and minimizes heat loss. An evacuated tube collector system consists of a series of insulated glass tubes that are arranged in parallel rows.
Figure 2. Evacuated tube collectors for domestic hot water. Courtesy of CAREarth.
The solar water heating system most common to cold environments is the closed-loop anti-freeze liquid system (Figure 3 and Figure 4), which circulates a food-grade anti-freeze (usually propylene glycol) through the solar collector. The heated glycol is then pumped into a heat exchanger. A heat exchanger can be a plate (Figure 3) or two coils of copper piping in a water tank (Figure 4).
Figure 3. Flat-plate solar water heating system (with plate heat exchanger). Courtesy of Enerworks.
The performance of flat-plate collectors and evacuated tube collectors is similar regardless of the amount of solar radiation.
Figure 4. Evacuated tube solar water heating system (with copper coil heat exchanger). Courtesy of CAREearth.
Flat-plate collectors tend to perform better on days in which the ambient temperature is similar to the collector temperature, whereas evacuated tube collectors tend perform better on days when there is a larger difference in temperature. For cold and cloudy climate regions evaporated tubes can perform better than flat plate collectors.
Solar hot water systems are considered a mature technology as they have been commercially available for over a century. They are available on many scales, from small do-it-yourself kits for domestic hot water needs, to large commercially installed systems for agricultural applications. There are more than 600,000 m2 of solar water collectors installed in Canada.
Whether used for residential or agricultural purposes, solar water heating systems are usually paired with a back-up heating system, in order to ensure that hot water is never lacking. A solar domestic water heating system can provide from 80 per cent to all of a household's hot water needs in the summer, depending on water consumption habits. During the winter, however, its output falls to 20 to 25 per cent of hot water needs.
Though unable to provide for all hot water needs in a residential or agricultural application, a solar hot water system does offer a clean, renewable, and efficient way to cut down on the overall cost of water heating.
A solar hot water system can be connected to your existing hot water tank, allowing it to use significantly less energy. Heating water accounts for a quarter of energy usage in a normal residential home; using solar heat can substantially cut your energy bill.
Whether mounted on the ground, an outside wall, or a roof, the solar collector for the water heating system should face south, so that it is exposed to as much direct sunlight as possible during peak sun hours, from 10 a.m. to 3 p.m.
The energy used to heat water is sunlight, a clean, renewable, and free source of energy. A solar hot water system will require only the electricity used to pump water into the collector. After installation, the solar water heating system will require only routine maintenance.
For all approved commercial solar water heating systems, the Province of Ontario is offering a full PST rebate of those installed and purchased before January 1, 2010.
For commercial enterprises, the federal and provincial governments offer joint incentives for adopting solar thermal water heating, reimbursing farms up to 50 per cent of the total cost of a solar water heating system.
For the federal ecoEnergy for Renewable Heat Program, the incentive is up to $400,000 and is proportional to the 'Performance Factor' assigned to the individual system, the 'Incentive Rate' assigned to the general type of system, and the "Area (square metres) of the solar collector" installed. The Ontario Solar Thermal Heating Incentive (OSTHI) matches the federal program up to $80,000.
The Ontario Soil Crop Improvement Association, through the Canada-Ontario Farm Stewardship Program, offers to pay 30 per cent of the costs, up to $5,000, of a solar water heating system for a farm.
For residential solar water heaters, Bullfrog Power and Enbridge Gas
Distribution offer an approximate
Community groups in Kingston, Ottawa, and Toronto offer resources, advice and further incentives for homeowners looking to install a solar water heating system. For example, Sustainable Ottawa, through the Solar H2Ottawa program, offers a further $1,200 incentive, as well as preferential pricing with local installers. In conjunction with federal and provincial incentives for home renovations and energy retrofits, some regional programs can significantly ease the cost of solar domestic hot water.
CAREarth Solar Energy Systems
Ronnybrook Farm Dairy
Companies are listed only for example purposes. This list is not meant to exclude other qualified vendors offering this technology and service throughout Ontario. See a complete list of accepted solar collectors at www.ecoaction.gc.ca.
A special thank you to Graham Juneau for all of his hard work in creating this infosheet.
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