Wednesday, 14 July 2010

Solar stuff.

I have been looking further into cheap renewable energy provision - one thing that is clear is that cheap and renewable are an oxymoron.  See previous posting "Piss power for your boat"

So what's available in the Solar Power market.

Solar panels use light energy (photons) from the sun to generate electricity through the photovoltaic effect or photo-electric effect). Most modules are usually rigid, but there are some flexible modules available, based on thin-film cells.

One type of solar panel is the polycrystalline which is made from a block of silicon that has multiple crystals. These panels are square in shape, and have a surface that looks like a mosaic. Polycrystalline solar modules are less efficient than a single crystal wafer. However, they are much simpler to produce, and cost far less to manufacture. This makes them much less expensive to purchase. That means twelve percent of the energy in the sunlight that strikes these panels is converted into electricity.

The second type of panel uses a thin film layer of material otherwise known as amorphous. More recently, improvements in construction techniques have made amorphous solar cells more attractive for large-area solar cell use.

The last type is monocrystalline. Monocrystalline panels convert sunlight with a higher efficiency than polycrystalline and thin film amorphous panels. This means that fewer panels are required to produce a given amount of energy. They are often used when space is limited, or when there are high costs associated with installing a lot of panels.

The durability and longevity of polycrystalline panels are comparable to monocrystalline panels. Generally, polycrystalline panels have approx 12% conversion efficiency.

It should be remembered that standard ratings are not always indicative of the conditions in which you will be using your panels. These panels assume relatively cool climates, and are rated on a standard of twenty-five degrees Celsius (about seventy-seven degrees Fahrenheit). Very few solar panels incorporate any design features to decrease panel temperature.

Panels operating at a higher temperature – fifty degrees Celsius or more – will be a lot less efficient. That may sound like a lot, but these are dark coloured panels in direct sun. The likelihood of them rising to those temperatures is much greater than you think.
Expect the panels to lose somewhere between fourteen and twenty-three percent of their power converting capacity in these conditions. It should be noted that these tempreture standards apply to all types solar panels not just the polycrystalline, amorphous or monocrystalline type.
Since cell heating reduces the operating efficiency it is desirable to minimize the heating. Panels that are set at an oblique angle to the sun, in very hot locations can sometimes generate more power because they operate at a cooler tempreture.

Most solar cells are capable of producing electricity for at least twenty years without a significant decrease in efficiency.


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