Solar Water Heating
The sun supplies us with a free, endless resource for energy; solar water heating is the most cost-effective way to tap into that resource. This is only one of the reasons many people choose this type of system as their first investment in renewable energies.
Simple and reliable solar water heaters
Closed-loop glycol systems are our preferred systems for typical applications. They typically consist of 2 – 4’ x 8’ or 1 – 4’ x 10’ solar collector(s) mounted flush to the roof, a single 80 or 120 gallon solar water heater with an electric heating element to ensure a consistent supply of hot water regardless of weather conditions, and a single circulating pump run by a small electric (PV) solar panel which is mounted on the roof with the hot water collectors.
We can and do install drain back systems with different heat exchanger and/or storage tank configurations, but we prefer the glycol systems for the following reasons:
o A freeze-proof mix of distilled water and propylene glycol (the same non-toxic glycol used as a food preservative) transfers the suns heat from the solar collectors to the heat exchanger. This is a closed-loop system so there are no concerns with deposits resulting from poor water quality.
o There is only a single, brushless DC pump (many systems have two AC pumps). Brushless pumps have a very long life span. This nearly silent DC pump is powered directly from a small PV panel so you aren’t using electricity from the grid to power your green solar water heater!
o Our systems make hot water during power outages because they are run from the PV panel rather than the power grid.
o There are no sensors and no computerized controller. Properly designed and installed solar water heaters are very reliable in general, but these are the parts we have found most likely to cause reliability problems.
o A standardized Rheem solar water heater is used which features a single electric element for 24/7 hot water. Standardized equipment results in more reliability, lower labor costs, and better parts availability.
o Our tanks feature an integral heat exchanger which allows us to use the single pump described above, and avoid problems associated with deposits from pumping well or city water through an external heat exchanger.
Is there a down-side to the closed-loop glycol systems? Of course! Isn’t there always? These systems can overheat if not properly sized, or if left unattended for long periods (days or weeks) in extremely hot weather. All of our systems feature “overheat bypass loops” to address this issue. If the house is left empty during a summer vacation, the bypass valve can opened to allow the system to cool itself overnight. Automatic valves are also available.
In some cases, like vacation homes which stay empty for long periods of time, we do install drain-back systems for the ability to easily turn them off. In that case we still can still use the same tank with the integral heat exchanger for the benefits it offers.
A few examples of the benefits of Solar Water Heating:
o Systems have long life expectancies and require little or no maintenance from year to year.
o N.C. and Federal tax incentives reduce the price of a typical residential system roughly in half.
o New construction represents a cash-positive transaction of about $3,400.00 from day one.
o Existing construction represents about a 10% return on investment.
o You have fixed your water heating costs as the cost of energy continues to rise.
o Offsets almost 2 tons of CO2 emissions yearly for a typical household (family of four), as well as other greenhouse gasses.
Solar Water Heating FAQ
Q. How Does a Solar Water Heater work?
Solar water heating uses a panel or multiple panels mounted on your roof to collect heat energy. As fluid passes through these panels the heat energy is transferred into the fluid, which in turn is transferred into your water heater. The solar loop is circulated using either an AC pump, or even better, a DC pump powered by a small PV panel.
Q. Do I need to change my water usage?
Not at all. A standard electric water heating element is integrated into the solar water heating tank. During extended cloudy days or when friends or family are visiting and water usage is unusually high, the electric element makes up the difference.
Q. How much will it cost me? And are there any financial incentives?
The cost of a typical system is around $7,500. North Carolina has a 35% tax credit with a maximum of $1,400, the Federal tax credit is 30% with no maximum limit, and Progress Energy is also currently offering a $1,000.00 solar water heating incentive. So on a $7,500 system the final cost after tax credits is $3,850.00, or $2850.00 if you are in a Progress Energy territory, a 50% savings! These credits can be carried over for up to 5 years.
Q. How much can I save?
Especially in today’s more efficient houses, water heating can account for up to a third of a typical family’s energy usage. It is common for our systems to provide 85-90% of a typical household’s needs. This typically translates to $300 - $500 a year depending on the size of the house and number of occupants.
Q How long does the installation take?
Depending on the difficulty, installation time is 1-3 days. However, the hot water is only off for a few hours.
Q. What about high winds?
The panels are usually mounted very close to the roof, preventing high winds from getting underneath them. They are attached through the roof deck to the attic beams using very heavy duty lag screws, providing an extremely strong bond between panel and roof. Realistically speaking, the panels will not be coming off unless your roof does.
Q. Do I need to worry about roof leaks?
We use high quality copper flashing for all penetrations which is correctly integrated into the roofing system. They are typically the highest quality flashing materials we see on the roof at our installations.
