When you hear the term Reciprocating engine generator, you could be forgiven for believing that it is something out of a sci-fi movie. A piece of equipment designed by aliens!

Actually, a Reciprocating engine generator (REG) is much more down to earth. To put it simply, a REG’s job is to provide incremental energy almost instantly with comparatively low capital expenditure. REG’s play a vital role in ensuring safe and reliable power supply to the grid.

Since REG’s can function on a variety of fuels, they are critical for:

  • Ensuring incremental power to the grid during peak hours.
  • Neutralising the inconsistencies of solar, wind and other power generating sources.
  • Ensuring prompt backup generation during an outage


1. Enhancing Grid Efficiency:-

A REG has the advantage of temporarily producing power for a particular user or group of users - this means the users can reduce or totally eliminate their reliance on the grid when it is experiencing high demand.

A REG when used in a CHP (combined heat and power) plant can greatly improve efficiency but also reduce carbon dioxide emissions. This is done by channelling the by-product heat into heating or cooling buildings.

2. Reliability and Safety: -

When a power plant has to stop generating power due to a malfunction, a REG plays the role of a saviour that quickly helps start it again. This is called Black Start and is one of the most critical functions of the REG.

A REG is also used in nuclear power plants to supply the power needed to safely shut down the plant and maintain the reactor when there is a loss of regular power, a coolant episode, or an operational issue.

3. How does a REG Work?

It uses the expansion of gases to drive a piston inside a cylinder. The piston’s linear movement is converted into a rotating movement of a crankshaft - thus generating power.

Types of REG

REG’s are categorized by the number of: -

a) piston ‘strokes’
b) by the type of combustion (spark-ignited or compression-ignited) and
c) by kind of fuel.

Capacity of REG’s.

They can range from less than 1 MW to as much as 20 MW. It is not uncommon for groups or sets of REGs to be installed together - which means they can provide 50, 100 or even 200 MW of power.

REG’s. The last defence.

Reciprocating engine generators can be powered up almost instantly and supply the full load in less than five minutes. Since they can be switched on and off multiple times daily with minimum wear and tear, they are very useful for short run cycles. They can operate at high altitudes and in areas with high ambient temperatures. They are smaller than gas-fired combustion turbines.


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Mahindra & Mahindra Ltd., Engine Application Business (Powerol), Farm Equipment Sector, Gate No.2, Akurli Road, Kandivali (East), Mumbai - 400 101, Maharashtra (India)


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