Click to enlargeStep Two - Your Solar and Wind Resources

This step involves determining how much solar and energy is available at your location: your RESOURCE. It is important to know your available peak sun hours. Your solar energy peak hours can be looked up on these charts.

Solar Resource is your sites Peak Sun Hours. This is the peak-hour equivalent of your global solar radiation. Sunny places like Phoenix may have 6.5 Peak Sun Hours. The total solar radiation throughout the day has an equivalent of 6.5 hours at peak. Peak solar values are Standard Test Conditions (STC) which is 1,000 watts per square meter. 25 degrees C (77 degrees F), and an Atmospheric Mass Unit of 1.5. This refers to the path through the atmosphere sunlight must make to reach the ground. At noon the sun goes through the shortest path, at dusk, sunlight travels the longest path. STC places the Atmospheric Mass at 1.5.

Wind Resources are defined by Wind Zones. Wind Zones span 7 levels ie. Wind Zone 1, Wind Zone 2 etc. Wind zone 1 is the lowest wind speeds, with Wind Zone 7 the highest. Look up your sites wind resources. You'll need a Wind Zone 3 or higher for best results.

Your solar and wind resources are the key to understanding the particular resources at your site. If you have low winds, but great solar access, this would lead you to a more Solar influenced system.

If you have little direct exposure to the sun, but have higher wind averages, then Wind should be your emphasis.

As in step 1 (determining your load) the next step is to find your average Solar radiation (in average Peak Solar Hours/Day), and your Average Annual wind Speed.

Solar Energy is described in Solar Zones that describe the Equivalent energy of a day's solar resource into Peak Hours. Your site's location will have a Peak-Hour rating. For a location like Portland, Oregon, with it's cloudy micro-climate the rating is 3.5 Solar Peak hours/day.

This is an average of all days and reduced to a daily peak amount. Use this number to multiply your Solar Module Array peak power rating to calculate the Energy produced by that panel, or array of panels, at your location.

Example: How much Energy does 1,000 Watts of PV Panels produce in Portland, Oregon? The answer is 1,000 Watts times 3.5 Peak hours producing a product of 3.5 1000-watt-hours, which simplifies to 3.5 kWh of energy.