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Sun, Wind Give Energy Options

Posted on: Wednesday, 8 March 2006, 15:00 CST

In many parts of Canterbury the availability, reliability and cost of electric power can be major issues.

Property owners intending to connect a new house or building to the nearest mains power line may find that the capital investment involved can be upwards of $20,000 for every kilometre of wire and poles.

For many years, one solution to meeting power requirements has been the use of diesel or petrol engines with alternators, commonly known as generators.

There can be a number of problems with this approach.

Generators can be noisy, polluting, and costly to run and maintain.

Depending on how they are used, they can also require frequent replacement.

For some, extended operation of a generator is simply uneconomic, while limited generator hours mean the absence of "flick of a switch" convenience -- where power is available at any time of the day or night.

Remote Area Power Systems (Raps), incorporating renewable energy sources and batteries can overcome some of the problems associated with generator-only systems.

Renewable-based systems convert energy from the sun and, or, wind to electrical energy for use in the home. Their location is not always "remote", but the term can be used to cover small-scale stand- alone power supply schemes, irrespective of location.

Even some people living in cities, where comparatively cheap mains electricity is readily available, prefer to remain independent of the local power company by installing their own power generating plant.

When combined with battery storage, renewable-based Raps provide a reliable, low running cost and environmentally-friendly solution to the energy needs of most householders in remote areas.

With a renewable-based Raps, solar, wind or micro-hydro power replaces the power otherwise provided by a generator. Batteries store the energy produced so that power is always available.

An inverter is usually used to change the direct electric current (DC) produced by batteries and renewable energy sources to the alternating current (AC) required by most household electrical appliances.

Electricity can be drawn from one or more renewable sources.

These sources include micro- hydro systems, where a suitable source of running water exists; or small wind turbines, often combined with solar panels.

Wind and solar are usually combined in a single system, together with battery storage.

The result can be a more reliable supply, equivalent to a mains electricity supply.

The wind/solar combination is a good one as the wind tends to blow more when there is cloud cover and less sunshine.

There is also a good seasonal match of more sun in the summer and more wind in the winter.

A combined system can be a cheaper option than having either a single, large wind turbine or a greater number of solar panels, both combined with greater battery storage capacity.

A domestic independent power supply system typically consists of a small wind turbine of 300 watts up to 1.5 kilowatt output, a series of approximately four or more solar panels and enough battery storage to last four to five days.

Solar (or photovoltaic) cells convert light into electricity.

They work most effectively on clear sunny days but even with full cloud cover they still produce some electricity.

Long-lasting and reliable solar panels consist of multiple individual cells wired together. Several panels mounted together are known as a solar array.

The size of the solar array depends on the amount of power required, as well as the amount of solar energy available at a particular location.

If energy requirements increase, more panels can be added to the system, although some upgrading of the control system may be needed to allow for the extra power.

Solar arrays providing household power are generally fixed, mounted on roof tops or on separate structures away from shaded areas.

In some instances it may be effective to mount the solar array on a moving frame, or tracker, which automatically follows the sun throughout the day.

Solar Electric Specialists Limited is a good place to start if you're looking at alternative energy supply.

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Source: Press, The; Christchurch, New Zealand

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