Solar Hot Water Heating

One of the biggest energy drains in the home today is the hot water tank. Showers, dishwashers, sinks and automatic washers depend on hot water and, in the case of showers, the use could be several times a day. It accounts for 25% of the home energy consumed and accounts for almost 2 tons of carbon emissions from each home. Not only is the hot water used for washing purposes many gallons of it sit idle in the pipes after use and cools down. In effect, it is wasted energy

With the price of energy going up steadily year-after-year alternative methods for heating water are being explored. And one of the most cost-effective and environment-friendly methods is solar-powered heating. 

Sun-Assisted Heating

There are two types of solar heating:

1. Photovoltaic: The sun’s direct rays activate electrochemical cells to produce electricity. These solar-activated cells are semiconductor units made of silicon, an inert compound containing no liquids, chemicals or other additions. As long as the sun shines on them they produce electricity. And because there are no moving parts they do not require regular maintenance, are quiet and non-polluting.
2. Direct Heating: This system converts the sun’s radiation into direct heat for the home.

For solar-assisted water heating both types of solar energy are required for a self-sustaining system. However, if a source of electricity is available to run the small pump then this is not a cost to the household budget. In many European countries solar water heating contributes upwards of 50-65% of hot water generation.

Main Parts of Solar Water Heating

1. Solar Collector: This is the workhorse or “business end” of the system and is available in a few different options. The solar collector could even be made of a simple piece of glass covering an insulated box. Inside the box could be as simple as a large piece of sheet metal soldered to copper or aluminum pipes and painted flat black. However, the more advanced systems use collectors sealed in a vacuum tube.
2. Pump: As mentioned before, the pump can be powered by photovoltaic cell energy or from common household current. The pump transfers the glycol from the collector to the heat transfer/storage unit. In warmer climates a convection system can the coolant through the system.
3. Glycol Storage: This is a constrictor to prevent to much of the hot glycol from entering the transfer tank.
4. Heat Transfer Tank: The glycol enters this tank through small pipes which transfer heat into household water.
5. Hot Water Tank: This can be a standard electric water heater. The heated water from the transfer tank enters this unit supplementing the normal hot water cycle.

How It Works

The panels are attached to the south-side of the roof or an are where they received the most sunlight. When the panels heat up to a certain temperature the pump is activated moving a steady stream of glycol through the receiving panels and down into the storage unit. Cold water from the main water line enters the bottom of the solar storage tank and is heated by coils of stainless-steel pipe coursing with hot glycol. This solar heated water rises to the top of the tank then is transferred into the homeowner’s water heater and the into the hot water system. If the water is hot enough then it goes directly out into the system or when the need arises. If there is an extended cloudy period then the normal operation of the hot water tank – electric, oil or gas – kicks in and supplements the temperature.

In-Floor Heating

Not only can direct solar be used to heat water for showers and clothes washing it can also be used to supplement hydronic in-floor heating. This also creates an opportunity for extending the heat in the home if the flooring is tile. Ceramic tile on a thick bed of concrete is a good storage area for heat making the floor warm long after the sun goes down.

In the northern regions solar water heaters fall into year-round and seasonal operations.

Year-round systems: These are more expensive because they are designed to operate throughout the year regardless of the weather conditions. They have thermostats to prevent the coolant from overheating and special shields and freeze protection to prevent damage from cold and ice.

Seasonal Systems: These are “fair-weather” systems designed above freezing temperatures and have to be shut down in winter. They make great systems for summer vacation cottages.

Energy Savings

In 1984 the average price of professionally installed solar water heating system cost about $6,000. Today, with inflation, that installation would cost $11000. However the average cost today works out to $6,000 to $8,000 which means that more contractors are getting into solar heating, as are more manufacturers, which is bringing the cost of the units downward. With a 28 % to 45% drop in the price of solar heating there is also the possibility of federal and state grants. If you live “off the grid,” meaning that you are not on any power from a utility, then this system would be in the cards for you.  For more information on solar water heating click here.

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