Off Grid System Approach

What does Off Grid mean?

     Off Grid is a system and lifestyle designed to help people function without the support of remote infrastructure, such as an electrical grid.

In electricity, off-grid can be stand-alone power system or mini-grids (typically to provide a smaller community with electricity).

    Off Grid electrification is an approach to access electricity used in countries and areas with little access to electricity, due to scattered or distant population. The term off-the-grid can refer to living in a self-sufficient manner without reliance on one or more public utilities.

    Going off grid represents the ultimate in energy independence. No more utility bills or power outages when the grid goes down. A common misconception is that a true off-grid house is able to operate completely independently of all traditional public utility services. Although this is not the case. The term "off grid" traditionally refers to the electrical grid only.

Stand alone electrical power

    Electrical power can be generated on-site with renewable energy sources such as solar (particularly with photovoltaics), wind, micro hydro and a generator with adequate fuel reserves to back the system up. Such a system is called a stand-alone power system or sometimes referred to as a Hybrid power system.

Economic consideration 

     Locations that are expensive to connect to main electricity grids are particularly suited for off-grid renewable energy developments, for example remote or rural areas with no or very deteriorated infrastructure.

     In situations where grid parity has been reached, it becomes cheaper to generate one's own electricity rather than purchasing it from the grid. This depends on equipment costs, the availability of renewable energy sources (wind, sun), and the cost of a grid connection. For example, in certain remote areas a grid connection would be prohibitively expensive, resulting in grid parity being reached immediately.

Becoming energy independent and self sufficient 

    Getting there, however, requires more than just installing solar panels on a roof and disconnecting. Specialised power electronics and an energy storage system are the heart of any off-grid system, along with a reliable source of renewable energy such as solar, wind or hydro.

 

Off grid system approach

 

A Typical Off Grid System

>Off Grid Inverter / Chargers

     Appliances in a home operate on AC current. Solar and other renewable sources generate DC current. An inverter is required to convert DC current from the renewable source to usable AC current for appliance and other home powering needs. But where does the “charger” part come in? In an off grid application, batteries are used to store energy for later consumption when the sun is not out, or the wind is not blowing. Because there is variability in the renewable source, a generator is often incorporated into the system to charge batteries when needed. Because the output of most generators is AC. Essentially, an off-grid inverter/charger will convert power from DC to AC for consumption and AC to DC for charging.

>Charge Controllers for Off Grid Applications

   It might seem redundant to have an inverter/charger and a charge controller, but each serves its own purpose in an off-grid system. A charge controller allows power from a DC source like a solar array to charge the batteries. 

>Battery Storage for Off Grid Systems 

    A truly off grid solar system must incorporate batteries to achieve true energy independence. Batteries function as the “bank” where excess renewable is deposited and then later withdrawn when needed. Required battery capacity, measured in kWh (kilowatt-hours), depends on the size of the loads that will be powered, meaning that there is no “one size fits all” answer. Other battery considerations include battery chemistry, battery size, storage and recyclability of battery materials.

 

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References:

  1. https://en.wikipedia.org/wiki/Off-the-grid
  2. http://www.outbackpower.com/applications/off-grid