Solar hot water systems use basic thermal principles to capture incoming
solar radiation and heat water for domestic and other uses. Over the years,
a variety of system designs have been developed and tested to meet speci
Mc consumer needs and conditions. Due to the cold climate in the Northeast
we use primarily closed loop systems with a 50/50 water/glycol (antifreeze) mix.
The main difference between domestic and commercial systems is the sizing of components and the number of thermal collectors required.
As a general rule, a smaller family would require 1-2 collectors with
an 80-gallon storage tank. A larger family might require 3 collectors with
a 160-gallon solar storage tank.
Businesses that use a lot of hot water are excellent candidates for a
solar hot water system, including gymnasiums, laundromats, restaurants,
car washes, pools, and factories that use hot water in the manufacturing
process. You can use either Nat plate solar collectors or evacuated tube
solar collectors. Flat plate collectors are similar in style to the PV panels
on the cover of this booklet (right side). The tubes on the left are evacuated
tube solar collectors. Evacuated tube solar collectors perform better
during cold or cloudy days; Nat plate collectors perform better during the
summer months. Collector arrays can be mounted on a sloped or a Nat
roof, on the south wall of your building, or on the ground.
Solar hot water (SHW) operates in series with your existing heating
source by preheating the incoming cold domestic water, with the existing
hot water heater as a backup. There is usually no need to alter your existing
hot water heating system. If the water in the solar storage tank is hotter
than the temperature setting in the primary tank, then the solar-heated
water passes through without further heating. If the water in the solar
storage tank is cooler than the temperature setting in the primary tank,
then additional heating is provided by the existing or backup system.
This means you get hot water from the solar system when the sun is shining, with assist from the backup system when the sun is not shining.
SHW offsets the cost of fossil fuels or conventional electricity normally
used to heat your water. Over the year an SHW system can provide
as much as 60%-65% of all water heating needs, even in cold climates.
During the summer months the system operates at its maximum with little
extra heating from conventional sources required. Given that about
20-40 percent of the average family’s energy use comes from the cost of
operating a domestic water heater (the second highest energy cost in a
typical household), the savings garnered from an SHW system plus the
increase in home resale value will usually offset the cost of installation
within 6-8 years, the fastest payback of any renewable energy system.
After that, your SHW system will be putting money back in your wallet.
Solar hot water systems are:
• Reliable: SHW systems are designed to provide hot water using the
clean power of the sun Mrst and other fuel sources as a backup.
• Affordable: Tax credits and state incentives reduce your cost, making
SHW affordable everywhere. Solar energy is stable in price. As other
forms of energy rise in cost, the returns from your solar heating system
• Aesthetic: Looks great on almost any home. Flexible mounting
hardware allows for installation on roofs and walls, even on the ground.
• Environmental: Solar water heaters consume no fossil fuels, and no
greenhouse gases are produced. Safer, cleaner … environmentally friendly.
• Socially Secure: Reduces dependence on foreign and undependable
Frequently asked questions about Solar Hot Water Systems:
- How much space does a system require?
- How do you get pipes from the solar system to the storage tank?
Article by Don Wemple (Handbook Renewable Resources by Prudent Living)