16-03-2011, 04:45 PM
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SOLAR POWERED WHEEL CHAIR
Using solar power to produce electricity is not the same as using solar to produce heat. Solar thermal principles are applied to produce hot fluids or air. Photovoltaic principles are used to produce electricity. A solar panel (PV panel) is made of the natural element, silicon, which becomes charged electrically when subjected to sun light.
Solar panels are directed at solar south in the northern hemisphere and solar north in the southern hemisphere (these are slightly different than magnetic compass north-south directions) at an angle dictated by the geographic location and latitude of where they are to be installed. Typically, the angle of the solar array is set within a range of between site-latitude-plus 15 degrees and site-latitude-minus 15 degrees, depending on whether a slight winter or summer bias is desirable in the system.
It is presumed that at ‘peak sun’, 1000 W/m² of power reaches the surface of the earth. One hour of full sun provides 1000 Wh per m² = 1 kWh/m² - representing the solar energy received in one hour on a cloudless summer day on a one-square meter surface directed towards the sun.
Triming installed a pair of 20 Watt panels in series to deliver the 24 Volts required by his wheelchair. The extra energy provided by the solar panels gives him an extra 30 minutes of full power every sunny day, and sunny days are the days you want to be out and about. When it rains the solar panels are not useless; they function as an umbrella. The solar panels and frame are easily detached to allow for easy transportation of the wheelchair.A conventional fully-powered electric wheelchair can go approximately 7km on a charge, but in contrast, a solar powered wheelchair can go 10km to 12km.
SOLAR PANELS:
The output of a solar panel is usually stated in watts, and the wattage is determined by multiplying the rated voltage by the rated amperage. The formula for wattage is VOLTS times AMPS equals WATTS. So for example, a 12 volt 60 watt solar panel measuring about 20 X 44 inches has a rated voltage of 17.1 and a rated 3.5 amperage.
V x A = W
17.1 volts times 3.5 amps equals 60 watts
If an average of 6 hours of peak sun per day is available in an area, then the above solar panel can produce an average 360 watt hours of power per day; 60w times 6 hrs. = 360 watt-hours.
