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Supporting Varying Loads Using Rooftop-based Solar Power Systems
With the significant interest shown by industries and commercial establishments in the use of rooftop solar, especially to offset consumption of diesel from diesel gensets, an important question that arises is how to support different and varying loads while using rooftop solar, during times of of load shedding/power cuts.
Typically, prospective users of solar power ask two questions in the context of load requirements, especially during power cuts which is when solar might be required a significant percentage of the loads in the building.
- Can solar power support heavy loads?
- Can solar power support loads that could require high starting currents?
The above questions form the basis for this blog post. Part of the content for this post was derived from Solar Mango – the Rooftop Solar resource.
Types of Loads
While discussing loads, of main concern is the fact that there two types of loads – light and critical (many times heavy) loads.
Light loads comprise loads such as lighting and fans, typically these are about 40-60 W each. Heavy loads comprise air conditioning, motor machinery etc, which require both high power (large AC systems could be more than 10 kW each) and also require a high starting current. Both these could pose challenges to use of solar for heavy and critical loads.
This blog provides provides some inputs in this regard.
Rooftop Solar Solutions to Support Different Loads
Due to rooftop space constraints or issues with integrating diesel and solar power, you might be faced with limits on the kind of load or extent of load that can be supported. Many innovative solutions are being implemented, and they can be broadly classified into two approaches
In this solution the rooftop solar system is used to support non-critical loads that don’t require heavy starting current, such as lighting. Such a system requires the light points to be wired through a separate circuit that can be powered only through solar.
This solution is favoured by those who are severely restricted in the size of rooftop plants they can install.
Here the critical loads that must run continuously, even during a grid failure, are identified (such as a portion of the plant, or a critical machine) and their electrical circuit is isolated from the rest of the plant’s circuitry, sometimes through a separate feeder. The rooftop solar plant has a battery backup and is the primary source of power for the critical load, keeping it running even during grid failure. Any excess power generated by the panels is first used to charge the batteries, and then supplied to the rest of the plant. Any shortfall in power (perhaps due to an overcast day) is made up through a diesel generator.
This system is essentially a solar powered industrial UPS and is favoured by those running critical loads that cannot wait for a diesel generator to start up.
EAI’s Diesel to Solar Report – The one and only such report in the world
EAI has published a unique report to assist those keen on using solar power to offset their diesel consumption.
To know more about using rooftop solar power and reducing the use of diesel gensets, you can also refer to this comprehensive report EAI has published. The Diesel to Solar report is a comprehensive guide to implementing a rooftop solar system to reduce diesel consumption for power.
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