Imagine this. It’s a scorching, smoggy day, and the sun is beating down mercilessly. Now think about lighting a propane or gas fire inside your house – or running a huge electric heater – to heat water. All that extra heat warms your house, and generators must burn dirty coal to produce the electricity you need. It would make so much more sense to use the sun to heat the water directly.
Interest in clean energy has surged following our summer of smog and hydro brownouts. Wind turbines and photovoltaic (solar electric) cells produce clean electricity, but typical payback periods can range from 15-20 years. Household solar water heating offers one of the fastest paybacks, along with easy installation.
I spoke with John Gilbert, one of Caledon’s first residents to install a solar hot water system. According to Gilbert, the simplest system uses solar energy to preheat water going into a conventional water heater operated by electricity, gas, propane, or oil. Typically, water enters our homes at 10-12 degrees C. If the solar system preheats the incoming water to 35-40C, the conventional water heater only needs to use half as much energy.
Gilbert’s system consists of a black solar collector panel, about 4’ x 8,’ which contains a serpentine length of copper tubing through which the heat transfer fluid flows. The tube is contained within an insulated aluminum frame, and covered with glass to retain heat and protect it from the elements.
A pump driven by a smaller solar panel circulates heat transfer fluid through insulated tubing leading from the solar panel to a heat exchanger and back. The heat exchanger transfers the heat to water in a solar storage tank, which is similar to a standard water heater tank. This tank connects to the regular water heater tank.
The solar panel needs to be mounted and aimed as close to due south as possible. Ideally, the roof slope should be 35-55 degrees; otherwise, the panel can be mounted on a separate frame to give it the proper slope. The distance from the panel to the heat exchanger should be as short as possible to minimize heat loss in the transfer tubing, no more than 15 meters. Unfortunately, our house didn’t meet the requirements, so we were unable to install solar water heating.
Cost: Total system cost including the photovoltaic cell, the heat exchanger/pump module, the solar storage tank and the copper lines is approximately $3500. Installation can be accomplished by someone who understands basic plumbing.
Payback: A typical payback period for these systems is four to seven years, depending on water usage. You can calculate your savings by clicking on the Solar Calculator at www.enerworks.com.
Between now and June 30, 2006, you can receive a $700 rebate from the federal government on solar hot water systems and installation. There is no PST on solar panels until November 2007.
Environmental Bonus: A solar water heater can prevent the emissions of 1.4 tonnes of carbon dioxide per year, as well as sulphur dioxide, nitrogen oxide and mercury pollution.
If every household in Caledon installed one of these heaters, we would save enough power to run 1800households for 1 year, and prevent 19,000 tonnes of C02 emissions. You can meet your share of Canada’s Kyoto target just by taking this single step.
Dr. Richard Ehrlich