Solar chimney cost effective, environmentally responsible

Traditionally, the conventional design of our homes in Western Canada is one of resource-consuming appliances making up for the heat loss, or gain, in our ever changing seasons.

Traditionally, the conventional design of our homes in Western Canada is one of resource-consuming appliances making up for the heat loss, or gain, in our ever changing seasons.

With hydrocarbons and energy being our biggest export, and natural reserves being abundant in this province, it continues as an accepted practise; and when resources are cheap and abundant, it is cost effective.

Other countries of the world not lucky enough to have abundant energy wealth had to be more frugal with their consumption demands. This resulted in structures designed to use more solar, geothermal and wind-driven systems to offset their need for mechanical heating and cooling.

With prices for hydrocarbons increasing, these concerns are starting to be addressed by innovative, cost-conscious and environmentally-conscious consumers in our province.

In the previous two columns, we discussed thermal mass for heat storage and earth-coupled heat exchangers.

Illustrations of thermal mass are internal stone walls or cement floors placed where the sun can warm them during the day; or the heat from a fire being slowly released back into the room, as with a masonry wood stove.

Earth-coupled heat exchangers provide fresh air ventilation of tight, energy-efficient homes while decreasing mechanical heating or cooling requirements by using the heat of the outgoing air and the geothermal heat of the ground to pre-warm or cool the incoming outdoor air.

The next step in the utilization of this free and natural process is the installation of a mechanism known as a thermal or solar chimney.

A solar chimney uses the heat of the sun to warm the air inside the chimney and create an updraft; this then generates a suction effect at the bottom of the chimney, drawing in cooler air.

Proper design dictates the chimney has to be higher than roof level; the side facing the sun will absorb more heat if it is glazed, and a heat-absorbing material should be used on the opposing side. The size of the heat-absorbing surface dictates the effectiveness of the chimney by increasing convection, and the resulting air flow.

To maximize the cooling effect, the system can be designed in conjunction with an earth-coupled heat exchanger and a Trombe wall.

The advantage to the Trombe wall is that it can be reversed in cooler weather to help provide solar heating, and in combination with the earth-coupled heat exchanger, it can help reduce cool weather use of mechanical heating appliances.

A variation in the design of the solar chimney can use the attic space of a home to aid convection in the solar chimney and improve ventilation of both attic and home. This protects the attic from overheating, and a cooler attic reduces need for powered cooling and ventilation.

The simple design of a solar chimney used in conjunction with earth tubes, and solar mass, is an efficient way of providing fresh air for an untainted interior atmosphere.

If designed into initial construction, it’s cost effective and environmentally responsible.

Lorne Oja is an energy consultant, power engineer and a partner in a company that installs solar panels, wind turbines and energy control products in Central Alberta. He built his first off-grid home in 2003. His column appears every second Friday in the Advocate. Contact him at: lorne@solartechnical.ca.

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