Solar Hot Water

Capturing the sun’s thermal energy for use in your home

South Portland, Maine - Solar Hot Water
An evacuated tube solar hot water system installed on the roof of a home in South Portland, ME.

Did you know that Maine has 450,000 homes heated with oil? This dependence on a foreign fuel source makes us vulnerable to supply disruptions and price volatility—not to mention the fact that we are polluting the northeast with the highest per capita CO2 emissions of all New England states.

Using sunshine to produce hot water for showering, laundering and dish-washing is a practical way to make a positive impact on the environment while saving money at the same time. After 10 years of designing and installing hundreds of solar hot water systems in Maine’s challenging climate, we’ve distilled our knowledge and experience into a robust design that offers the highest efficiency and durability. Maine Solar Energy can tailor its time-tested, field-proven system design to integrate with most existing water heating systems, whether it is gas, electric or oil-fired.

Solar hot water is the most common system type in Maine because it provides the quickest return on investment. This is because solar hot water substantially reduces fossil fuel consumption and CO2 emissions, particularly when an oil boiler or electricity is being used to produce domestic hot water. A properly designed solar domestic hot water system can save more than 300 gallons of oil per year and reduce greenhouse gas emissions by more than 5,000 lbs., depending on your existing situation.

How it Works

Solar hot water collectors are typically mounted on a south-facing roof or wall, but we also have plenty of experience ground-mounting systems when the roof is not a viable option. Major system components include the collectors, a purpose-built solar storage tank, copper piping, solar pump and electronic controls.

Whenever sunshine makes the solar hot water collectors hotter than the water in the bottom of the solar storage tank, an electronic sensor automatically turns on the solar pump affixed to the tank. Sun-heated antifreeze is pumped down from the collectors and circulated through a heat exchange coil located in the bottom of the storage tank, thereby transferring the heat from the sun to your domestic hot water supply. We design automatic hot water backup into all solar domestic hot water systems so that when the sun can’t get the job done, you don’t have to worry about cold showers. The solar storage tank has a secondary heat exchange coil located in the top of the tank, which is plumbed to your existing heating system for backup. If this is not possible, alternative solutions include using a special tank with an electric element for backup or installing an on-demand hot water heater.

Solar Thermal System Design
Typical schematic for solar thermal system design for domestic (home) applications

Solar Hot Water Collectors: Evacuated Tubes & Flat Plates

After years of researching and experimenting with different brands of collectors, we have come to the conclusion that Apricus evacuated tube collectorswww.apricus.com offer the best performance at the most reasonable price. Apricus is a global leader in evacuated tube technology based in Australia. We generally recommend evacuated tube technology over flat plate collectors because the tubes’ vacuum insulation design prevents system heat losses in Maine’s relatively cold climate. Plus, the cylindrical shape of the tubes enables them to better harvest low-angle wintertime sun at our northern latitude.

Flat Plate Solar Hot Water Collectors

For applications where high demand will come in the warmer months (seasonal homes, i.e.), or where cost is a primary concern, we offer Stiebel Eltron flat plate collectors www.stiebel-eltron-usa.com and Chromagen Collectors. The Stiebel Eltron collectors have been manufactured in Germany by a family-owned business for more than 50 years and we have had excellent results over the years with this product.

Solar Storage Tanks

We wanted to know how much heat is lost in our solar storage tanks overnight, so we ran our own test and found that the super-insulated Stiebel Eltron tank loses less than .5 degrees F per hour. This means that if you heat your tank up to 150 degrees during the day, it will lose just 6 degrees from 6 p.m. to 6 a.m. We believe Stiebel Eltron manufactures the best dual coil solar storage tank on the market. Stiebel’s purpose-built tanks have 3 inches of foam insulation to store precious BTUs harvested from the sun and its two internal heat exchange coils allow for easy integration with almost any boiler-based heating system. This enamel-lined steel tank comes with a sacrificial anode that is easy to view and replace if necessary.