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Solar Powered Mini-Grid

A solar powered mini-grid is an electrical AC power distribution network providing an electrical power to a community with multiple buildings located in a small geographic area.  The power is supplied by a solar PV array with batteries and backup sources which are usually a diesel or propane generator and a connection to a local electrical grid.

Typically in the developing world, the electrical grid is non-existent or operates only for a few hours per day, so that the Mini-Grid providing electrical power 24-7 using the free and renewable sunlight as the power source is a great resource for the community.  The system creates the standard  current for the site country which is compatible with all AC appliances, power tools, etc.

AC Coupled

The GSI mini-grid system is an “AC Coupled” configuration based upon a controller/battery inverter, several typical grid-tied inverters, and a large bank of batteries or other storage devices connected to the wires running to the buildings.  The grid-tied inverters are connected to the solar array and creates AC power that is fed into the controller/battery inverter which determines if power should be fed directly to the electrical loads (lights, computers, etc.) or used to re-charge the batteries.  During the evening hours when the sun is not shining, the battery inverter system generates the required power from the batteries and if the battery voltage drops too low, can turn on and control a generator for the needed power.  When the sun rises in the morning and the solar array starts producing, first the loads are powered and then the excess energy goes into recharging the batteries.

Knowing the electrical loads used in each hour of the day, such as lights, computers, fans, etc., allows GSI to design the system using HOMER software from the US Department of Energy.  HOMER determines the size the solar array and battery storage appropriately to minimize the use of the fossil fueled generator.

The AC Coupled backbone allows renewable and conventional power sources to be combined, depending on the availability of the grid or generators. This is a particular advantage in situations where the grid structure is weak.  The system allows other sources of power to be seamlessly integrated such as wind turbines, water turbines, bio-mass and other sources of AC power.  Their power will be used if it is available, if not then the solar power or batteries are used.

Expandable Configuration

As time passes and more people get connected to the system, the GSI mini-grid can easily be expanded by adding more solar arrays and more battery inverters, thus enabling it to handle the rising energy demand.  The initial investment is protected as it is does not become obsolete and will be used as the backbone for future expansion making it ideally suited for applications in rural areas of developing countries.

The typical initial size of a system is 5 kW or roughly 7,000+ kWH per year but it may be expanded to over 100 kW.   Stand-alone power grids can be gradually expanded into large-scale systems as a result of the parallel connect-ability of all energy suppliers and consumers.  The system is very reliable due to redundant system structure, if one component of a multi-array system fails then the whole system does not come down but the output is reduced.

 

Global Solace Inc.
20530 Beallsville Rd
Beallsville, MD 20839
301.972.8672 | info@globalsolace.org
EIN Number: 27-4400089