Green building: The science behind solar panels. We take a look at the science behind one of the most talked-about alternative energy sources in the world today.

Millions of people across the globe use solar power on a daily basis to help meet the energy demands of their everyday lives. But how many people know where this solar energy comes from? While solar power does of course originate from the sun, there are still many different states that the power has to go through before it becomes usable energy. Here's an inside look at the science behind solar panels. Solar panels - the basics. The heat from the sun can be used to heat water or air for residential, commercial and industrial use. Sunlight can also provide heating or be converted to electricity using solar electric panels. Solar (photovoltaic) panels convert energy in the form of light from the sun into electrical energy. Between 4 and 22 percent of the energy falling on the panel is actually converted to usable electrical energy. The rest is reflected or turned into heat.  Source: The City of West Torrens website. Solar panels are rated by their wattage, so an 80w panel is rated to output 80 watts in a good hour of sun - in Australia, we average annually 4 hours of sun per day, so an 80 watt panel would output 320 watts per day. The average household uses around 15kw of power per day, so most households would require a 3kw solar power system at the very least to cover electricity usage.  Australia has an estimated 300 megawatts of installed PV power, contributing to an estimated 0.1 to 0.2% of total electricity production - despite the hot and sunny climate that would make it ideal for extensive use. Installation. The cost of a solar panel system varies greatly from company to company, but other factors will influence the price of an installation. For example, the angle of your roof may mean your system needs to be mounted in tilt frames, and if your home is a multi-storey dwelling, your installer will need to hire additional equipment to get your system installed.  Checklist for buying solar panels. Ensure your house is suitable, that the roof is not in the shad most of the day and that you have enough space on your roof. Check that the roof faces the right direction. North-facing panels are generally accepted as best, but it's not essential that they face this way, and you will still get a good output with other orientations. Establish whether a 1.5kw or 2 - 3 kw system is right for you. The bigger the system, the more upfront the investment - but the more energy you generate, the more you will save both money and environmental impact. Check the feed in tariff for your state on your state government website. The Solar Bonus Scheme will credit eligible customers who use a grid connected solar panel system to power their home. Check your eligibility for solar credits. To be eligible for these, your designer/installer must be accredited by the Clean Energy Council - visit the Clean Energy Council website for a list of accredited designers and installers. Your installer must personally sign off on the installation report. Demand that you get a 25 year warranty on panels, 10 years on your inverter and 12 months on the installation as per industry standards - check the Clean Energy Council website for more information.

The above example of the required capacity of installed solar panels to meet overall demand for electricity in a household is simply wrong. The majority of the 15 kW consumed in the house is consumed at times when the solar panels are not generating any
electricity. Electricity consumed at these times will have to be bought from the electricity retailer (imported from the grid). The 3 kW of installed solar panels may indeed produce something like 15 kW during the middle hours of the day. Most of the electricity
produced will be in excess of what is being used in the house at the time and will be exported to the grid. In NSW right now (for new installations) the price paid for electricity exported to the grid is about one-sixth of the price paid for electricity bought
from the grid. Given the large and largely unsubsidised up-front cost of the panels, inverter and installation labour, installing solar panels is not economically sensible. The least economically disadvantageous configuration would be a small installation
which produced no more than the average household electricity consumption during the hours when the solar panels are generating at their best. The situation depicted in this example would be valid if the excess electricity generated during the day could be
stored and used when the panels are not generating. This is of course what happens with an off-grid set-up using batteries. Batteries and the more complex inverter and regulator make this a much more expensive installation which is economically feasible only
where grid electricity is not available or would be even more expensive to lay-on. Hmmm..well we're going to investigate further. Stay tuned for an update. editor
Robert Arthurson 22-Aug-2011 09:51 PM

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