- Identify the household energy demand and household owner’s budget for an installation of photovoltaic energy system.
- Evaluate the past bills and identify the system size. If there is no previous data, then estimate the connected load (kW) and determine the average annual energy consumption (kWh). This will lead to the estimation of proper system size.
- The calculations for getting the approximate system size (kW) are iterative and can be performed using NREL tool PVWatts.
- Finalize the system size (kW) by performing the site analysis and identifying the available roof area for the installation. Shading analysis must be done and proper spacing between the modules must be calculated.
- Maximum number of modules should be placed in series. This helps in achieving high voltage which mitigates the wiring loss and reduces the size of the conductor used for the layout. Number of modules in a series is calculated according to the National electric code 2014 (NEC 2014).
- Proper sizing of an inverter is a key. The ratio of inverter AC output and photovoltaic system DC output (AC/DC ratio) should be in between 0.80 – 1.30.
- Under-sizing the inverter, meaning AC/DC ratio below 0.80, will bring down the inverter efficiency. Oversizing the inverter meaning AC/DC ratio above 1.3 may lead to loss of power from module.
- Modules and inverter must be installed according to their installation manuals. Any violation will lead to failure of a complete system and void warranties associated with it.
- The sizing of wires, breakers, grounding rods and load center must be performed according to the NEC 2014.
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