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Solar Hot Water Heater

Expected return

In Québec, it is estimated that a domestic solar water heater can supply up to 40% of the energy needed to meet a family's hot water needs.

According to measurements taken during the pilot project on domestic solar hot water heaters by the Agence de l’efficacité énergétique (AEE), a solar hot water heater should save yearly 7.7 kWh per litre of hot water used daily.

Households in Québec use an average of 186 litres of hot water per day. Using a domestic solar hot water heater could save 1,432 kWh per year, $107 per year at the current cost of electricity.

How does a solar water heater work?

Solar collectors are typically installed on a home's rooftop. They collect energy from the sun and convert it into heat, which is then used by the system to heat water for home use.

A solar water heater is made up of 4 components:

  • Solar collectors (commonly called solar panels)
  • A heat exchanger
  • Insulated piping
  • A hot-water-storage tank

Solar collectors

Solar collectors or solar panels are typically installed on a home’s rooftop, facing full south. They can also be installed on a wall or on a tripod anchored in the ground.

We estimate that the hot-water needs of a family of 3 could be met by 2 solar collectors measuring about 3 m2 (32 sq. ft.) each.

The exact number of collectors required will depend on the type of system selected, on the amount of hot water consumed by the household, and on the orientation of the collectors relative to the sun.

A solar collector converts the sun's energy into heat.

Heat exchanger and insulated piping

The heat-transfer fluid that flows in the solar collector absorbs heat and transports it through the pipes to the hot-water-storage tank.

The heat-exchanger system allows the heat-transfer fluid to flow through conduits (in a closed circuit) inside the hot-water-storage tank. Gradually, the fluid transfers its heat to the household water. No mix or contamination occurs during this transfer.

The cooled heat-transfer fluid then returns to the solar collectors to begin a new cycle.

The heat-transfer liquid typically flows with the help of an electric pump and a regulator.

Hot-water-storage tank

Cold water (± 7ºC) flows into the hot-water-storage tank. The heat provided by the heat-transfer fluid preheats household water while it's inside the storage tank.

The solar water heater provides the maximum amount of heat to the water in the storage tank before the water is transferred to the adjacent conventional water heater. Therefore, instead of being supplied with cold water, the conventional water heater receives hot water from the solar system's storage tank.
 
The conventional water heater only acts as a back-up system when needed, to heat the water to its normal usage temperature (60ºC). How much the conventional water heater is used will depend on the amount of solar radiation and on the occupants' hot-water needs.

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A pilot project to install solar hot water heaters in Québec

From June 2009 to October 2010 a pilot project to install solar hot water heaters in the residential sector took place. Financial assistance was provided to homeowners, within the framework of this project, to encourage them to install a solar hot water heater in their home to save energy.  

Panneau solaireThe pilot project enabled 70 solar hot water heaters to be installed. They were installed in the Capitale-Nationale, Montérégie, Montréal, Mauricie, Estrie and Outaouais regions.

For one year regular measurements were taken from 23 of these hot water heaters to collect information on solar hot water heating in real use conditions. The systems measured enabled an average of 40% of the energy required for the hot water needs of a home to be saved. Solar energy enabled a yearly average of 1,215 kW per household to be saved. 
Rapport technique

The final technical report on this project is now available in French :

Performance des chauffe-eau solaires solaire installés au Québec – Rapport final (PDF, 2 700 ko)

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