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Solar System sizing consideration factors

Solar System sizing consideration factors

Require data are following –

  1. Estimating the daily or hourly load requirements during a typical year.
  2. Calculating the required security of supply, taking into account the back-up source, (if any).
  3. Calculating the mean daily irradiation in the plane of the array at the chosen site for every month of a typical year.
  4. Considering the maximum number of consecutive sunless days likely to be experienced.
  5. Considering the mean daily ambient temperature for every month of a typical year.
  6. The estimated cell temperature rise above ambient of the modules in the array.
  7. Typical current-voltage characteristics of the module at various irradiances.
  8. Selecting DC bus voltage.
  9. Considering the maximum allowable depth of discharge of the battery.

10. Estimating percentage energy losses in the battery, power conditioning equipment and control system.

11. Estimating losses in the array from module mismatch, cables and voltage drop across blocking diodes.

12. Calculating the predictable losses from dust and shading.

13. Calculating the global position.

14. Considering the categories of solar modules structure.

15. Choosing the type of solar charge controller such as voltage regulated charger, PWM (Pulse wide modulated), MPPT (Maximum Power Point Tracker).

16. Choosing the type of solar panel such as mono-crystalline, poly-crystalline, thin film.  


In practice, designing a PV system depends if it is off-grid or grid-tied.

Off-grid systems require a thorough design, often with several iterations to optimize the number of modules, batteries, and stand-by generators, if necessary, to minimize system costs. Loads must be carefully calculated.


Grid-tied systems generally are sized by one of two methods:

         i.            How big of a system is possible with the available budget, i.e. budget constrained.

       ii.            How big of a system is possible given a limited area, i.e. area constrained.

NOTE: Systems rarely are large enough to match the load.

Approach is generally used. Also, the PV industry is marketing pre-engineered packages of varying sizes.