Solar Collectors
There are several types of solar collectors available. Flat-plate collectors (glazed or unglazed) and evacuated-tube collectors are the more common types.
Flat-Plate Collectors (FPC)
A glazed flat-plate collector system typically consists of a dark coloured, or specially coated, solar heat-absorber plate that is fitted with a network of copper tubes. The tubes are in a glass-covered (glazed) insulator box. The sun passes through the glass and heats up the water or glycol solution in the copper tubes, converting solar radiation into useable heat energy. The glazing provides a greenhouse effect to reduce the amount of solar energy that escapes, while also protecting the panels from dust, moisture, and other contaminants. Most household systems consist of one or two collectors. Each collector is about 1.2 x 2.4 metres (4 x 8 feet), similar in size to a sheet of plywood.
Unglazed flat-plate collectors can absorb more of the sun's energy. However, the lack of glazing results in a larger portion of the absorbed heat being lost to the surrounding air in colder weather. Unglazed collectors work well in seasonal applications like summer outdoor pool heating.
Evacuated Tube Collectors (ETC)
An evacuated tube collector system consists of a series of insulated glass tubes that resemble fluorescent light bulbs that are arranged in parallel rows, each containing a small absorber pipe. The inner pipe absorbs solar energy and transfers it to a water or glycol solution. The air between the pipe and the glass is evacuated to trap heat in (like a thermos), maximizing the amount of heat energy transferred to the fluid. Household ETC systems tend to take up less space than equivalent FPC systems.
| Collectors Comparison Chart | ||
|---|---|---|
| Type of Panel | Glazed FPCs | ETCs |
| Performance | Typically perform better than ETCs on warm, clear days. | Insulating properties of the vacuum allow ETCs to produce higher liquid output temperatures at very cold temperatures. |
| Cost | Often less expensive. | Often more expensive |
| Installation | System direction and angle is less critical, providing more installation options. | System direction and angle is more critical, providing fewer installation options. |
| Maintenance | If a portion of the collector fails, the whole collector may need to be replaced. | Individual tubes can be easily replaced with little effect on total system operation. |
Installation costs (including equipment and labour) can vary from $5,000 to $8,000, and depend on the size, configuration, and equipment requirements. Installation costs tend to be lower if solar water heating systems are installed during the construction of a new home.
Solar water heating systems typically have a 25-year life expectancy. As with other mechanical systems such as your furnace or water heater, regular maintenance is recommended to extend the system's life and to maximize performance. Systems typically have warranty on the equipment and companies commonly offer maintenance contracts to ensure your system is functioning at an optimal level.
