Renewable Energy: Photovoltaic (PV) solar electric projects

• Basic 12 volt negative ground PV system
   
  This diagram illustrates the basic components required to harness the suns energy using a 75 watt Photovoltaic (PV) solar array and a regular 12 volt car battery.
   
  Other components in the system include a 15 Amp charge controller, a fused service disconnect and the inverter and are grouped into three systems:
   
  
  1. The PV solar panel array
     The ideal location for a fixed array is the spot that gets the most exposure to south facing sun. The frame of the solar panals are attached to a ground rod and in this case a 120 VAC GFCI outlet powered by the inverter is located on the array support post.
      
     
  2. The Battery Box
     Any standard unsealed 12 volt battery should be located in a freeze protected area and outside of any habitable spaces. The discharge and recharge cycle of a battery will release harmful gas into the air. Avoid breathing this by building a box between the solar panel array and the charge controller location and putting the battery in there. There is a grounding rod in the battery box and a direct ground from the battery negative terminal to the rod.
      
     
  3. The Charge controller and disconnects
     The charge controller, service disconnects, and inverter should be kept out of the weather and are typically located in an interior space. The PV system requires a fused disconnect that controls the hot power lead from the battery, the PV in and the post charge controller PV out. There is also a grounding rod the disconnect is attached to. If an inverter is used, a separate disconnect should be installed if the inverter powers anything other than a device plugged directly into the inverter. In this example, a cord from the disconnect is plugged into the inverter and this powers the 120 VAC GFCI outlet outside by the solar array.
  
  The size of wire used in any 12 volt direct current (DC) portion of a PV solar system is subject to voltage drop because of the lower voltage. The length of wire used should be kept at a minimum otherwise larger diameter wire must be used which can increase costs significantly.
   
  The wire size / length charts on the example will give you an idea of the effect of voltage drop on long distance DC wire runs. Every milli watt of power is important in a solar system so don't give away power by losing it in undersized wires or inefficient components.