Anybody who has used a black
garden hose in summer knows that solar energy will heat water. But that same
garden hose in winter will be useless. This has been the problem with
harnessing solar energy to heat our water or our homes. In winter, when we need
the heat most, the heat loss to ambient air is such that collected energy becomes
useless for the heating of water. Passive solar, that is south facing windows,
certainly collects solar heat during the day, but unfortunately, much of that
heat is then lost at night.
But new technology has
significantly changed what is possible. This new technology is vacuum evacuated
tubes. Vacuum evacuated tubes make it possible to heat a liquid in a roof panel
in the middle of winter, and deliver hot water into the house. In other words,
technology that allows us to heat water in a useful way in the middle of a Manitoba
The question is how much does
an installation cost and will it save me money? Well, that depends on what you
want.
If you are solar dependent
and want your hot shower in the morning, the necessary water will have been
heated the previous day and will have been kept hot all night. Hot water when
the sun is shining is relatively easy to deliver, whereas hot water first thing
in the morning brings its challenges. The challenges can be overcome, but it
costs money.
Furthermore, a system that
can fully utilize the sun’s energy every day of the year will pay back more quickly than a system that utilizes the
sun’s energy in winter, but finds the sun’s heat in summer a liability.
In other words, a system
designed to only heat water for domestic use will pay back quite quickly,
especially if the homeowner is willing to accept the discipline of doing the tasks
that need hot water when the sun shines. Some solar proponents say the system
will pay for itself in less than four years.
On the other hand, it is also
possible to design and build a solar hot water system that will keep the house
warm in winter. Unfortunately such a system will not be doing anything useful
in summer. In fact such a system needs to be protected from overheating in
summer. It will take longer to pay back the investment in this case.
The other factor affecting the
economic viability of a solar hot water system is the future price of hydro and
fossil energy. We know the price will go up. We don’t know how fast.
A practical solution will
probably be something in between: a system designed to deliver enough energy to
only look after domestic hot water needs in December and January. This system
will deliver surplus heat which can be used to heat the house as the days get
longer.
Join us Thursday, February
23, at the Eastman Education Centre. A panel of solar users that will discuss their
experience with solar energy.
Eric Rempel
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