| Solar
Water Heating Systems
Solar
energy is a clean and abundant energy resource that
can be used to supplement many of your energy needs.
Solar energy can be utilized as a form of heat, such
as solar water heating, and as electricity, such as
solar photovoltaics. Solar water heating systems are
commonly referred to in the industry as Solar Domestic
Hot Water (SDHW) systems. |
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Consumers often ask if there is enough sunlight in
Canada to support solar applications such as water
heating. In fact, there is enough solar energy to
deliver an average of 2500 kWh of energy per year.
This means that a solar water heater can provide
enough solar energy to meet about one half of the
water heating energy needs for a family of four.

Water
heating is one of the most cost-effective uses of
solar energy, providing hot water for showers,
dishwashers and clothes washers. Every year, several
thousands of new solar water heaters are installed
worldwide.
Canadian manufacturers have developed some of the most
cost-effective systems in the world. Consumers can now
buy "off-the-shelf" solar water heaters that
meet industry-wide standards, providing a clean
alternative to gas, electric, oil or propane water
heaters. Freeze-protected solar water heaters
manufactured in Canada have been specifically designed
to operate reliably through the entire year, even when
the outside temperature is either well below freezing
or extremely hot.
Benefits from
Solar Water Heating
A
solar water heater reduces the amount of fuel you need
to heat water because it captures the sun's renewable
energy. Many solar water heaters use a small solar
electric (photovoltaic) module to power the pump
needed to circulate the heat transfer fluid through
the collectors. The use of such module allows the
solar water heater to operate even during a power
outage.
Solar water heaters can also be used in other
applications, for example, car washes, hotels and
motels, restaurants, swimming pools, and laundry mats.
There are many possible designs for a solar water
heater. In general, it consists of three main
components:
- Solar
collector, which converts solar radiation into
useable heat.
- Heat
exchanger/pump module, which transfers the heat
from the solar collector into the potable water.
- Storage
tank to store the solar heated water.
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Most
medium to large systems have both an auxiliary
tank and a solar preheat tank with a heat
exchanger. |
The
most common types of solar collectors used in solar
water heaters are flat plate and evacuated tube
collectors. In both cases, one or more collectors are
mounted on a southerly-facing slope or roof and
connected to a storage tank. When there is enough
sunlight, a heat transfer fluid, such as water or
glycol, is pumped through the collector. As the fluid
passes through the collector, it is heated by the sun.
The heated fluid is then circulated to a heat
exchanger, which transfers the energy into the water
tank.
When the homeowner uses hot water, cold water from the
main water supply enters the bottom of the solar
storage tank. Solar heated water at the top of the
storage tank flows into the conventional water heater
and then to the taps. If the water at the top of the
solar storage tank is hot enough, no further heating
is necessary. If the solar heated water is only warm
(after an extended cloudy period), the conventional
water heater brings the water up to the desired
temperature.

Solar
collectors should be.

Cutaway
view showing glazed flat plate
1. Metallic Absorber
2. Glazing
3. Housing
4. Insulation
5. Heat transfer fluid inlet
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