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 winter now exists.
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