Solar Thermal Heating Works Even In Cold Climes

Most of the attention paid toward solar energy these days is on photovoltaic technology, harnessing the sun to make electricity. It has been used on satellites for decades so the potential for adding it to our rooftops is alluring, albeit still grossly inefficient.

There is another inefficient paradigm which can be aided with the sun’s heat yet garners little attention, the household water heater. Hardly a new technology but needed more urgently now than ever, the solar water heater is one of those no-brainer solutions which only now is beginning to move toward mainstream adoption, in such places as Hawaii and Spain.

Think about it. Most of us need a few drops of hot water to wash our hands throughout the day but don’t need gallons of it unless we bathe or clean our clothes. The rest of the time, we waste energy maintaining a constant temperature in our tank. Tell me how that makes sense!

It doesn’t, which is why my wife and I upgraded the water heater in our home to solar last year. We love it! We saw our energy bill drop by 20% in the very first month and ultimately top out at a monthly savings of more than 25%.

In areas with moderate winters (or none at all), the water heater is the second-greatest consumer of energy in the average home after the climate control system. Second-greatest! In fact, many electric water heaters pull current equivalent to forty 100-watt incandescent light bulbs when engaged. Ouch!

The solution for many is a solar water heater. Our system came with a couple of optional items but a basic unit for a single family costs about $4,000. At this price, depending on what one currently pays for energy, the amortized savings will take about a decade before entering the black.

The good news is that the units are designed to last at least 30 years and, of course, air pollution from the use of fossil fuels to heat water vanishes immediately. Modern units come with electric back-up coils so the risk of running out of hot water on cloudy days is minimized, too.

The inspiration from solar water heaters doesn’t stop with laundry and showers, though. It can spill over (pardon the pun) into climate control systems. More excitingly, water heated with the sun increases in temperature so rapidly that it can be harnessed for wintertime applications of heating air, when daily exposure from the sun is quite minimal.

Unsure of the practicality of such an idea? I have you covered! The proof of concept already has been built and is in use as you read this in Okotoks, Alberta. Yes, in Central Canada!

The Drake Landing Solar Community combines geothermal heating with solar water heating to keep fingers and toes warm in winter while reducing the use of natural gas to the barest minimum. The project is so successful that the Prime Minister of Canada referred to Drake Landing as the greenest community in Canada and all 52 dwellings were sold before construction was complete.

How does it achieve this remarkable milestone of domestic heating in winter? The solution lies in the additive gains of geothermal, which provides a constant temperature well above freezing, and solar thermal, which allows for the harnessing of glycerin well in excess of 100° F.

You see, if the project engineers tried to heat plain water in the summer and store it for use in winter, too much warmth would be lost. However, by using glycerin, which changes temperature slower than water, the heat capturing process is more efficient. The secret sauce, though, is in the application of geothermal heat, which changes very little from month to month. That yields the additive gains because the rooftop solar collectors only have to heat the glycerin above the minimum of about 50° F which the geothermal heating provides. This keeps the swings in temperature within a narrow and more significantly manageable range.

So, if this application can work in Central Canada, just a few hundreds miles from the Arctic Circle, why isn’t everyone heating water with the power of the sun as has become the custom in China?

If you know the answer, please post it as a comment.

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