Solar Hot Water Heating Questions

What is Solar Hot Water Heating?

A system of thermal collectors that use a liquid working fluid to collect heat energy from the sun. With the exception of swimming pool heaters, the products that we offer use an anti-freeze working fluid. A water-to-water heat exchanger transfers heat to a hot water heater tank. A circulation pump regulates the flow of fluid in the system. In the picture the farm's dairy building has vacuum tube collectors to produce high temperature hot water for cleaning and sterilizing the dairy's equipment.

Can Thermal Solar Hot Water Heating Panels be Used for Building Heating?

It can be used as a supplemental heat source in a hydronic heating system. It should not be the only source of heat, as the amount of heat produced is the least in the winter, when the most heat is needed. It is possible to supply all the heat required, but it is definitely not an economically viable approach.

It can provide supplemental heat for both radiant heat and for hot water systems with baseboard or tall convectors.

There are systems that provide hot water for both DHW and for heating from the same set of thermal solar collectors.

Can Thermal Solar Panels provide Air Conditioning?

Yes, the heat collected can power absorbtion type refrigeration. Look up Oxford Gardens in Woodstock ON for an example of this application at work. During the summer of 2013 this provided 100% of the air conditioning load for this retirement home facility.

Flat Plate or Vacuum Tube?

For some people which is best question is similar to a chevy vs Ford topic. The best answer is that it depends on the project details. We offer both types. Some of the considerations are:

How Many Collectors will I Need For My House

For domestic hot water heating, some of the factors to consider are:

Can you Determine How Much Hot Water We Use?

This is an excellent question, and an accurate answer is required to correctly size your system without resorting to rules of thumb. For a couple of types of hot water heaters we can use a non-invasive methods to track your water use. For the majority of water heaters, the only accurate way is by inserting a flow meter into one of your pipes. This will require shutting of the water for a few minutes. For more details call us, or we can discuss this during a site visit. A diary method will give some useful information if you are willing to do it diligently for a week or longer.

Net Metering or Solar Water Heating?

Hot water heating accounts for approximately 22 percent of total household energy consumption (NRCan data from 2004). This energy may come from low cost sources such as natural gas, or wood. If it comes from high cost sources such as propane, oil or electric resistance heating, this is a considerable target for savings.

If your household has electric heat and electric hot water heating, which can offer the most savings by using solar energy? From one study which can be found at an average Canadian household using 236l of hot water per household per day is using 4775 kWh of electricity, or other fuel a year to heat the water. The mean household size was calculated at 2.55 persons from the 2001 Census, (Statistics Canada, 2001). For larger households with greater than 2.55 members, such as a 5 person household the energy input for hot water heating could be estimated to be twice this value or 9550 kWh.

The average Canadian household uses 19 kWh of electrical energy per day, according to a recent study. With electric heating and electric hot water you will be considerably above average. Therefore if your target is to reduce your current energy expenses, there is a bigger opportunity for savings with a net metering installation than with solar hot water heating. Another conclusion is that the opportunities of savings with solar hot water heating increase as the family size increases.

If a solar hot water heater was installed only to lower the utility bills of a family size of 2.55 people, it could avoid purchasing up to 4775 kWh, while with a solar PV net-metering system, it could avoid purchasing up to 11980 kWh per year. Therefore if there has to be a choice of only one system, and both systems have paid back the initial investment, the net metering system has the potential ability to reduce spending a little more than twice the amount of money relative to solar hot water heating.

If your annual electricity use is over approximately 11980 kWh per year, then in Ontario a net metering system will not bring your hydro bill to zero kWh. Then a solar hot water heater will provide additional electrical energy bill reductions.

If you only have a limited roof area to use, solar DHW usually uses less area for the given amount of solar energy captured.

Commercial uses of hot water such as a restaurant or dairy use a far greater amount of hot water, and the economics are quite different. There is no 10kW limit for solar hot water, since the energy is not exported to a utility, but consumed on the site where it is captured.

Heat Pump Domestic Hot Water Heater

Another idea that works for some locations, use a heat pump based water heater, and just use net-metering for your energy input. It does not work if your heating source is electricity, but could make sense if you heat with wood or other low cost fuel. There are at least 6 companies making these for the Canadian market. Note that they cool and dehumidify your basement when they are running, not exactly ideal during the winter, but nice in the summer.

Drain Water Heat Recovery

A drain water heat recovery can lower hot water heating bills dramatically if your household mainly takes showers and not baths. It costs nothing to operate, and can be up to 50% efficient. These are relatively inexpensive. Visit NRCan's web page on drain water heat recovery for more information.