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In most instances, solar is utilized as a power generation medium for off grid applications.  At Primus Wind Power, we are advocates for wind to be used in conjunction with solar for system redundancy, more uniform power generation, and reduced depth of discharge.  AIR is a suitable complement for nearly any off-grid power system where solar is being used.  It is recommended that wind represent between 10% - 50% of the power generation capacity, depending on three variables:

  1. Wind Resource:  With solar accounting for 50% or more of the power generation capacity, the wind resource analysis should be focused on solar assistance, which is during winter time months when wind is at its peak.  Most regions of the United States have sufficient wintertime winds to support most off-grid power needs (see winter wind resource map below).
  2. Solar Resource (see solar resource map below):  In cloud-free locations at less than 35 degrees latitude, such as Arizona, wind will comprise a smaller percentage of total power generation (typically between 10% - 20%) since wintertime solar availability is high.  Other locations such as the Great Lake region or Canada with shorter and/or cloudier wintertime months, off-grid systems should have much larger wind capacity (typically between 20% - 50%).
  3. Load Specifics:  Energy loads that are necessary in the wintertime and nighttime should have a much higher wind component.  A prime example is hybrid lighting, where the load is increased in the wintertime (due to longer nights) and where energy is only needed during nighttime when wind power generation can occur and solar power generation cannot.




The table below should be used as a guide regarding the mix of PV and wind on a given site.  Based on the wind zone number and the solar resource in the particular region, an optimum percentage can be estimated.  For instance, in the Great Lake region (from Northern Illinois through Northern Indiana, Ohio, and most of Michigan), the wintertime winds are Zone 3.  With the solar resource fairly modest, the upper region of the band should be utilized, 40% wind.  In other Zone 3 locations such as Northern Texas with strong wintertime sun, wind should have a smaller percentage, 20%. 


Upper Average at 33’

Percentage Band

Location Example

Zone 1

9.8 mph



Southeast US, AZ

Zone 2

9.8-11.5 mph


Light Blue

Southern IN

Zone 3

11.5-12.5 mph



Northern IN

Zone 4

12.5-13.4 mph


Dark Blue

Central SD

Zone 5

13.4-14.3 mph


Very Dark Blue

North Central ND


Note:  Mountain regions in the map should be investigated in greater depth as terrain affects wind speeds significantly


Wiring AIR into Off Grid Solar Systems:

In the case of AIR, the wind generator is wired independently and in parallel to the PV components.  The output from the turbine is wired directly to the battery terminals.  This enables existing solar-only systems to be easily retrofitted with an AIR system.