Use the power of the sun to heat your water and significantly reduce your consumption of fossil fuels! Solar thermal systems are comprised of roof-mounted solar collectors and a holding tank for solar heated water. Most solar thermal systems fall in one of two categories. In a passive, or no-pump system, the holding tank is located directly above the solar collectors, where heat moves passively from the collectors into the holding tank by convection . In an active system an electrically powered pump is used to move heat transfer fluid from the solar collectors to the heat exchanger and holding tank. For both types of systems, an auxiliary energy source (electric or gas) is often used to provide additional heat on those cool and/or cloudy days.
Energy Trust of Oregon
PGE or Pacific Power electric water heating: $0.40 per annual kWh saved up to $1500.
NW Natural or Cascade Natural gas heating: $8.00 per annual therm saved up to $1500.
Central Lincoln PUD ($800/residential system)
Oregon Department of Energy issues tax credits amounting to $0.60 per kWh saved up to $1500 for qualifies solar thermal equipment.
Solar Thermal and Solar Hot Water
Drain back systems use a drain back tank or other wide spot in the solar loop to catch the heating fluid during periods of excessive heating or freeze conditions. These systems are designed to shut off the solar pump when either the solar tank gets too hot or the collectors are too cold. Advantages of this system are that there is no overheating or freezing concern and the heating medium is distilled water. This system requires a continuous,
downward slant in the solar loop plumbing and requires a small extra tank.
Closed Loop/Glycol systems are closed, pressurized solar loops in which a solution of propylene glycol is used to accommodate excessive temperature conditions. An expansion tank and the chemistry of the glycol solution are used to accommodate high heat conditions, while the glycol itself acts as an anti-freeze. There is no air in the solar loop, which can result in quieter operating conditions, the solar loop is not sensitive to elevation changes, and the expansion tank is smaller and easier to mount than a drain back tank. The glycol solution will break down over time, typically 6-8 years, requiring a replacement of this non-toxic solution.
Evacuated tube collectors use vacuum sealed glass tubes and highly efficient thermal concentrators. They offer superior performance during the colder months of the year, as they are more efficient than flat plate collectors at extracting heat from the lower temperature air.
Flat plate collectors have been successfully providing solar heat for over 40 years. The design of most flat plates uses a black heat sink backing upon which a pathway of copper fins and/or tubing direct the heat transfer fluid, covered by tempered glass with high heat transmission qualities. These collectors are robust and very effective at collecting heat during the warm months of the year.