The next task is to calculate the solar array size or wind generator size for the location of the radio site. Our data indicates that the area around Asheville, North Carolina gets 2.94 hours of full sun equivalent on an average day in January (worst case scenario). You can find the solar insolation or average wind speeds for your or any area on earth by going to the NASA web site at http://eosweb.larc.nasa.gov. If we know that we need to make a minimum of 17.8 amp hours per day 365 days of the year we can divide 17.8 amps by 2.94 and we find that our solar panel needs to make a minimum of 6.05 amps per hour of full sun equivalent. That means we would need to find a solar module with a Max. Power Current of at least 6 amps. This is approximately a 100 watt solar module. To calculate the size of a wind generator to do the job we would look at the average wind speed for the site keeping in mind that our site may or may not have the same wind speed average as that shown on the NASA web site. If the worst case is shown as less than 5 meters per second (M/S), the site is not acceptable as a wind generator site. Most wind generators in common use reach their rated power at 10 to 11 M/S and their output is usually given as a percent of their full rating at various M/S windspeeds. Our data shows that in general, the windspeed at Asheville ranges between 3.50 and 4.96 M/S throughout the year. This would not be a site that would benefit year around from a wind powered installation. However, for educational purposes, let’s say that the average daily wind speed ranges between 6.5 and 9 M/S at our particular site. The lower figure is the one we need to work with because we have to make at least 17.8 amp hours, 365 days of the year. Most wind generator manufacturers show output of their wind generators in both MPH and M/S. However, if only one figure or the other is given it is simple to make the conversion. To convert MPH to M/S divide MPH by 2.2. To convert M/S to MPH multiply M/S by 2.2. Let’s say that the wind generator we are considering is a 600 watt (full rated power at 11 M/S) unit. It is listed at 40% of rated capacity at a windspeed of 6.5 M/S. 40% of 600 watts is 240 watts (20 amps at 12 volts) so we know that it would only take about 1 hour of good wind (6.5 M/S) for the 600 watt wind generator to provide our daily power requirements.

MULTIVOLTAGE SYSTEMS
Since many communications systems require equipment of varying voltages working in tandem, the calculations become very convoluted. We suggest that you print a copy and complete the following worksheet and fax it to us so that one of our technicians can assist you in sizing your system. Our fax number is 406-363-6046. We are always happy to assist you in your sizing efforts and provide you with a cost-effective quote for the right equipment to do the job.