Solar Hot Water: How It Works

Solar Hot Water incentives for Seattle and all Washington State have just gotten better by being exempt from State sales tax!  Solar electric systems enjoyed this advantage, but now the incentive gap has been narrowed.  Solar hot water is an excellent solution for those with limited budget, rooftop restrictions, or simply like the idea of heating their water with solar instead of natural gas and all its environmental consequences.

A Solar Hot Water system is almost half the cost per energy output of an solar electric system.  A (30) evacuated tube system is about $7,800 and is equivalent to an (8) SolarWorld solar panel electric system at $13,000. 

Don’t let anyone discourage you from placing solar hot water on the same level as solar electric when selecting your renewable energy solution.  Sunergy Systems is one of the few installers who have stuck with this great technology during the incentive gap, so it’s doubly important to trust an experienced solar hot water specialist with your investment, especially as others scramble to learn design and installation best practices.  There are only "two" certified NABCEP solar heating specialists in the State, and our own Steve Tedesco is one of them, with over 400 installed systems in his portfolio.

Solar Water Heating

Heating water is the second largest energy load in most homes, just behind space heating. Installing a thermal solar water heating system will save you significant money and help protect the environment.  A residential solar water heating system west of the Cascades saves a typical family up to 90% of their hot water demands in the summer, 75% in the fall and spring, and 50% in the winter.  In addition, your system will prevent the equivalent of 20,000 car miles of greenhouse gases from entering the earth's atmosphere.

How solar water heating works

How Solar Hot Water Works

The solar collectors turn the sun's energy into heat, which is transferred to the water in either your hot water tank or a dedicated solar hot water tank via piping loops from the collectors.  This loop is filled with bio-degradable antifreeze solution, which stays inside the collectors and piping at all times. Whenever the sun shines on the collectors, the circulating pump comes on, and the solar fluid circulates within the closed loop.  The fluid gets hot inside the collectors and travels through the piping to a heat exchanger inside the solar heated water which transfers the heat from the antifreeze water inside the storage tank, which stores the heated water for your use.  When the sun is not shining, the circulating pump simply turns off, and the fluid stops circulating.

Works on Cloudy Days and Even when it is Freezing Outside

Because solar hot water collectors use the full spectrum of the sun, they efficiently absorb even the diffused solar radiation present on cloudy days and are an ideal solar solution to solar in Seattle, Bellevue, Tacoma, Olympia, Bainbridge and Everett weather conditions.  They do not need direct sunlight to operate and are not nearly as impacted by shading issues like solar electric modules are.

Types of Solar Hot Water Collectors

There are two popular kinds of solar hot water collectors, the traditional flat plate and the recently more common evacuated tube systems. E ach technology has its strengths and weaknesses and Sunergy Systems is one of the few solar contractors in the region that carries both technologies.  Our engineering staff will design your system with the most cost effective solution in mind.

Flat-Plate Collectors

Flat-plate collectors are by far the most popular kind of collector and work well in all climates.  They have been around the longest and are efficient and competitively priced.  They are very aesthetically pleasing and look just like a skylight.  They also operate precisely within the temperature range needed to heat domestic water, but are not well suited for many commercial high temperature water applications.

The collector is a shallow rectangular box with a glazed top and insulated back and sides.  An absorber plate inside gathers solar heat and transfers it to a network of copper tubing, through which the solar fluid flows.  Like evacuated tubes, they do work well on cloudy days, but will have more heat losses during cold conditions.

Evacuated Tube Collectors

Evacuated tube systems are a proven technology and have been widely available in Europe and Asia over the last decade and are finally making their way into the US market.  Up until the last couple of years they have been significantly more expensive than flat-plate collectors; however, with prices coming down and copper prices going up they are now cost competitive with flat-plates.  Evacuated tube collectors are appropriate for both high temperature applications over 140 degrees F and easily perform in residential low temperature applications.

Each tube and fin of the collector is contained within a glass tube from which all the air has been evacuated.  The purpose of the evacuated tube is to provide a perfect insulator to prevent heat loss to the outside temperatures and to prevent air from carrying heat from the hot surface of the tube to the cooler surface of the glass.  The temperature inside the tube can reach 350 degrees, while the outside of the tube is cool to the touch; tubes are barely affected by outside temperature and weather conditions.

To minimize radiant heat loss, the tube is covered with a selective surface.  The special coating absorbs more than 92% of the arriving radiation, but radiates less than 8% back to the environment.

Heat transfer from the absorber to the fluid circuit is performed by the "heat pipe".  A heat pipe is a closed system, carefully evacuated and charged with a small amount of water before it is sealed.  The absorber imparts heat to this water, causing it to evaporate.  The steam rises to the upper end of the heat pipe where it transfers heat to the fluid circuit via a metallic conduction bridge.

The Sunergy Systems Difference

Sunergy Systems is one of the few solar contractors in the region that carries both flat-plate and evacuated tube technologies.  Because we are not biased, you will receive an honest appraisal of your site.  Our engineering staff will design your system with the most cost effective solution in mind and  our installation team, with over 100 installed solar hot water systems of experience since 2006, will install it on your house or business. Serving your solar energy needs from Seattle to Redmond, Olympia/Tacoma to Everett and beyond, we cover the entire puget sound region.