Wake Up Call

A lot of people enjoy comfort foods – foods that remind them of their young days, when Mom made meatloaf, or spaghetti and meatballs. There is something about such things that is comforting to the soul.

In my home, I have comfort sounds. The wood stove has glass windows that are a bit loose. So when the wind blows, they rattle a bit. My brother offered to fix this once, but I turned him down. The glass rattling in the fireplace is the sound of the wind turbine turning.

About a year after I moved to my current house, I had a solar hot water collector installed. It has a 20 W circulating pump for the fluid, and I can hear it from my bedroom. It is a white noise – comforting, not annoying. On the sunny long days of June, the pump starts circulating the fluid well before 7 AM. On those days, I know that my hot water is virtually free. It is a very gentle and comforting wake up.
In the average home, 20% of the energy consumed is for hot water. Using less hot water, by using cold water laundry, and low flow shower heads, is an easy way to reduce the cost, and of course the emissions associated with heating the hot water. A solar thermal collector will provide you with about half your hot water, with almost 100% provided by the sun in the summer, and only a marginal contribution in the winter. In February, we had a very heavy, wet snow fall, that froze on my collector. So the sun did not get to it for almost a month. But sure enough, in a sunny day in March, the circulating pump came on. It was a sign of spring.

The thermal hot water system is made by Enerworks. It is a collector about the size of a 4X8 piece of plywood that sits on the roof. Downstairs, we installed a 60 gallon hot water tank (with no element), which feeds my 40 gallon conventional hot water tank. A freeze protected fluid circulates to the collector, which consists of copper pipes on a black background, with a piece of glass on top. When the sun shines, the collector and circulating fluid heats up. When the temperature in the collector is 5 degrees C more than in the tank, the fluid begins to circulate. It goes through a heat exchanger, which transfers the heat from the fluid to the water in the bottom of the tank. The tank water then circulates using convection, with the warmed water flowing to the top of the tank, and the cooler water at the bottom passing through the heat exchanger. The result is that the hottest water is at the top of the tank, and it is this water that feeds the 40 gallon electric tank. On a sunny day, the electric element in the hot water tank is not used, as the water is already warm enough.

One of the technical challenges with hot water collectors is overheating. What do you do when the water in your tank is too warm, and so it would not cool the circulating fluid? Enerworks has an ingenious way around this. The collector is on a slanted roof. At the top of the collector is a flap of metal with a memory. When that metal hits a certain temperature, the flap opens. This then allows air to circulate through the collector, using convection, drawing the cooler air from the bottom, and out the top, thus cooling the collector. The flap closes when the temperature falls, allowing the collector to once again heat up. Very elegant.

The payback on such a collector is somewhat difficult to calculate, and will depend on your solar angle, your hot water usage, and the cost of installation. Installation cost will vary depending on how far and how difficult it is to run the water pipes from the roof to the basement. With todays electricity cost, I figure my payback is 5-6 years. With tomorrows electricity prices, the payback will be faster. A solar hot water collector is one of the most cost effective sources of renewable energy.

I have heard that there are 1,600,000 electric hot water heaters in use in Ontario. A solar pre-heating system like mine will work with any type of water heater – oil, gas, propane, or electric, but with the concerns in Ontario about electricity supply, anyone with an electric hot water heater, and a good solar exposure should consider it.
The Minister of Energy recently issued a directive to the Ontario Power Authority, calling for more aggressive conservation. Solar thermal hot water heaters were included in the directive. I hope they come out with a good incentive program.
Buy one. You will save money, emissions, and you will also enjoy the comfort sound of the circulating pump when you wake up.

Leave a Reply