Sanctuary: Modern green homes

Solar hot water

This is an excerpt from an article in Sanctuary magazine issue 3.

In the average Australian household, hot water accounts for 30% of energy use. Water heating is second only to transport as a households largest cause of greenhouse gas emissions. However a solar water heater can reduce your emissions by as much as four tonnes of CO₂ or more per year—the equivalent of taking a car off the road! By using the energy from the sun to heat water at zero costs.

Depending on where you live and your climate a solar hot water system can provide between 50 and 90 per cent of your hot water needs. The initial purchase price will probably be higher than a similarly sized non-solar water heater but the savings made in energy bills will generally pay for this difference in less than 10 years—in as few as four years in some cases. A solar system generally has a longer lifespan than a conventional unit, so financial returns can be considerable over the life of the system.

This benefit has been recognised by the federal and some state governments and is encouraged in the form of renewable energy certificates (RECs) and rebates. Rebates vary from state to state, but can save you a great deal on the cost of a solar water heater, making them more economically viable.

Flat-panel and evacuated tube collectors

Most solar hot water systems use solar collectors (in the form of panels or tubes) to absorb energy from the sun. Water is heated by the sun as it passes through the collectors. It then flows into an insulated storage tank for later use.

The most common form of solar collector is the flat-plate panel. They consist of a dark coloured, metallic absorbing plate to which a network of pipes is bonded. This arrangement is then placed in an air-tight metal box with a glass cover on the top and insulation on the back and sides to reduce heat loss. As the sun shines on the collector panel the water in the pipes becomes hot due to conduction from the collector plate

In the last few years another type of collector has started to appear on the Australian market. These are known as evacuated tube collectors. They consist of two glass tubes (one inside the other) that are bonded to each other at each end to form a sealed space between them. The surface of the inner tube is coated with a heat-absorbing coating. The space between the two tubes has most of the gas removed from it (hence they are evacuated), which provides a high level of insulation. As solar radiation passes through the outer glass tube and heats the inner tube, it is trapped by the lack of gas, which would otherwise allow heat loss. As a result, the efficiency of these collectors is higher than flat plate collectors, and evacuated tube collectors are suited to colder climates as they even perform well on cloudy days.

Save water

This is an excerpt from an article in Sanctuary magazine issue 6.

Use three or four star WELS-rated shower heads, toilets and water fixtures. Catch your rainwater in tanks for use in the bathroom and garden and look into getting a wastewater treatment system. Use drought-tolerant landscaping.