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If you are considering renewable energy sources, the first question you need an answer to is how much energy can be harvested at your site. It isn’t a matter of just buying a turbine or some panels and mounting them. The first step is to determine if your particular location is suitable. You can certainly search for the average conditions for your city, but for exact information you will need a site assessment done by a professional….. Or do you??

General Site Information

If you are evaluating a solar application, you need to have an idea about where to place your panels. First, consider orientation. Solar panels work best when they face south, assuming you are in the northern hemisphere. You’ll need plenty of south facing sunshine with no shading during the day. Also, they should be set at an angle close to the latitude of your location. The optimal angle varies between 15 degrees less than your latitude in the summer to 15 degrees more in the winter. This does not pose a problem for ground mounting, but if you have a steep or flat roof, additional brackets will be required to set the angle correctly. Also, if your roof is old, consider replacing it before installing solar on the roof.

Solar Measurement Basics

Solar site assessments are based on calculations of peak sun hours. Two things you need to understand about that term:

– A peak sun hour is one hour of solar energy on a clear day falling on one-square meter at the correct angle to the sun.

– In ideal conditions, one peak sun hour equals 1 kWh per square meter.

Two other measurements that you will need to know are:

– Irradiance: The rate of solar radiation falling in a specific area at a moment in time. This is measured as kilowatts per square meter (kW/m2).

– Irradiation: Commonly called “radiation”, this is the amount of solar energy falling on a site over time. It is measured as kilowatt hours per square meter per day. (kWh / m2 / day)

In most locations, you can get 5 to 6 hours a day of good sunshine. When the sun is low in the sky during other daylight hours, solar power collection will be small or negligible.

Average Annual Peak Sun Hours

As I previously stated, you can find solar maps on the web at many locations, but they show the average annual peak sun hours by region. The maps do have a negative side to them though, they assume almost perfect conditions for a fixed solar array facing true south at the optimal angle of tilt.

Wind Measurement Basics

Wind assessments are easier to understand, but rely on long term data collection. If you are considering a wind turbine, you will need consistent winds in the 10-15 MPH range to optimize the system. You can check your local weather data to determine your average wind velocity but remember, wind data has not been collected for wind assessment purposes. Thus the results often represent the mean conditions near population centers in relatively flat terrain or low elevation areas. Their primary benefit to the analyst, therefore, is to provide a general description of the wind resource within the analysis area, not to pinpoint the windiest locales.

Is This a Bit Over Complicated?

Solar and wind assessments certainly do have a place in determining the feasibility of installing solar or wind renewable sources. If you were an investor who was going to put up a considerable amount of money expecting a good return, a professional wind or solar assessment would be the minimum documentation required. For the average home owner, the price is a bit more than what you may wish to spend.

What are the Alternatives?

What if you could do a solar or wind assessment yourself?

DIY – Solar and Wind Site Assessment