Click to enlargeStep Four - Determining your System

Now that we know your LOAD, your RESOURCE, and your system OBJECTIVES, we can now determine your optimum SYSTEM.

Now is the key step after Step (1) defining your load electrically in terms of Power and Energy. Step (2)is to define your local renewable energy resources, namely what is the average peak solar hours/day. And, what is the average annual wind speed to determine Wind Zone.

In Step (3) your objective is to define what "type" of system you're looking for. There are essentially three "types" of renewable energy systems: Grid Tie (usually Net-Metering systems), Grid Tie with Battery Back up, and Stand-Alone (Off grid).

An off-grid solar and wind system does not touch or interconnect to the Grid. Even though the Solar Photovoltaic (PV) panels you choose, and the Wind Generator you choose, each of these three types of systems use different Inverter technology.

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Sizing your system comes from working backwards. Define your electrical loads, the resources you have available, the type of solar and wind system you want, and lastly: the solar and wind power system.

From an energy perspective if you have an electric bill look for your total kWh electricity usage per month.

Example: You need 500 kWh of electricity per month. You've decided to use a Solar pv net metering system and produce the 500 kWh yourself. Your location is the Midwest and you have 4.5 solar peak hours of solar resource.

If you use 500 kWh per month dividing by the number of days/month gives us about 16 kWh of energy per day. If your site has a solar resource of 4.5 peak solar hours, then dividing 16 kWh by 4.5 hours gives us 3.55 Kilowatts (kw).

A solar array of 3,550 watts is therefore required to produce the entire 500 kWh of energy for your location. Use REC Solar pv panels 250 watts 24 VDC to combine into a solar PV array. The number of panels will equal 3,550 watts divided by the solar panels peak power (250 watts) coming to 14 panels. Make sure you round your panel numbers to an even number of panels.

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