Add battery back-up power option to existing grid-tied PV and solar systems

August 05, 2013 //By Mark Mays
Add battery back-up power option to existing grid-tied PV and solar systems
Mark Mays of OutBack Power explains how to add a battery back-up power option to existing grid-tied PV and solar systems.

Overview:  Homeowners and businesses have bought into the concept of distributed power by installing solar energy systems. There are a lot of factors that have caused a significant rise in solar energy production. These include federal tax incentives, renewable energy incentives, cheaper photovoltaic (PV) solar modules, immediate and projected rises in energy costs, and increasingly stronger desires for energy independence.
 
Almost all residential, community and light commercial PV/solar systems fall into three types, the first being the most common:

  • grid-tied capable of reducing dependency on utilities and saving money,
  • off-grid capable of supplying electricity where a grid is non-existent, and
  • grid-interactive where the presence of a connected energy storage system (usually in the form of a battery bank) enables the user to achieve both grid-tied benefits with off-grid independence.

The last type is especially useful in scenarios where the grid is down for a variety of reasons, when grid power is inadequate or problematic, or when grid power is costly making it advantageous to “offset” the grid using renewably-generated stored energy. Concerns about grid stability and even availability are more valid than ever, even in the developed world, as life-changing events such as historic storms, tsunamis, and other disasters are combining with increasingly routine brownouts, blackouts and other interruptions to raise anxiety levels about electricity supply to meet growing demand worldwide.
 
In areas where a lot of renewable energy is added to the grid, the effect of all this extra “peak demand” electricity can actually destabilize the “load demand” grid which relies on more conventional and less flexible or “dynamic” sources—once the sun stops shining or wind stops blowing PV arrays and turbines are effectively turned off, and that loss of peak electricity places even greater demands back on the relatively in-elastic grid which can’t always meet the need.

Figure 1 – Typical Grid Tie Inverter Utility Connection

 
For these and other reasons, the benefits of storing

Design category: 

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