The Sun provides the Earth with an astounding level of free energy every day. The Sun will also never send you a bill!
What is Solar Hot Water?
Instead of using the sunshine indirectly (either through the Earth for geothermal or the air for air source heat pumps), a solar hot water system collects this energy directly from the Sun. Because the Vineyard receives approximately 6 hours of good sunshine daily, solar hot water systems are most commonly used for heating domestic hot water. Larger solar systems can be used to provide space heating and domestic hot water. Because the cost of solar PV panels has come down so dramatically in recent years, it is now more cost effective in many cases to use PV panels to power heat pump water heaters. The cost/benefit analysis of solar hot water must be carefully considered to ensure that it will be a worthwhile investment.
How does solar hot water work?
Solar thermal differs from solar PV in that instead of producing electricity, we are producing hot water. Our two panel solar package is a great supplement for domestic hot water needs. Additional panels can be added to supplement a hot water heating system such as radiant or hydro air. The two main types of solar thermal systems on the market are drain back systems and glycol systems. These two systems produce about the same amount of hot water, they are just applied to different applications.
We recently installed one of the larger solar thermal installation on the island. Twenty 4×8’ solar hot water panels were installed at a private residence to heat the pool, produce domestic hot water, and supplement the radiant heating system. We expect this system will produce approximately 93,000,000 BTUs per year.
There may be tax credits available for the installation of solar hot water panels. We have the necessary MA plumbing licenses to install a solar hot water system in accordance with local authorities and our products are SRCC rated; this is necessary to receive the above mentioned tax credit.
Drainback solar hot water systems:
Drainback systems only fill the solar panels when there is enough solar energy to produce hot water. This benefits the system in two ways. First, the system will not freeze and become damaged in cold weather if the Sun is not shining. Second, a big concern of solar hot water systems is over production in the summer. If you do not use the hot water that is produced (such as during a vacation in the summer) you will produce an enormous amount of hot water at very high temperatures. This can set off safety valves and damage the system. A drainback system eliminates these problems by draining the collectors if the temperature of the stored hot water rises above a safe level.
Glycol solar hot water systems:
Glycol solar hot waters systems are filled with a mixture of food grade propylene glycol and water that protects the solar panels from freezing. An issue though is possible overproduction of hot water in the summer – excessive heat will break down the glycol and make this product corrosive.
Overproduction is handled in two ways; some systems have louvers on the panels that open to create air flow when the glycol gets too hot, other systems run at night to cool down the glycol by radiating solar energy from the collectors back into the atmosphere.
Our goal is to be Martha’s Vineyard’s premier plumbing and HVAC shop – we appreciate the opportunity to service and install your solar hot water system!