Due to the frequent increase in electricity tariff charged by the electric utility, poor reliability of electric supply, forced outages, long power cuts, etc., a large number of industries have switched over to their own generating station (plant) within their own campus. This method of generation is called Captive Power Generation and such plants are known as Captive Power Plants.
Advantages of Captive Power Plants
- Captive power may be cheaper than power from the grid.
- There are no transmission and distribution losses.
- The problem of electric theft is eliminated.
- There is no extra-cost on infrastructure like land, road, etc.
- overhead transmission cost is low.
- Forced outages can be lower than that of grid supply.
- No problem of power cuts.
Disadvantages of Captive Power Plants
- Cost of Captive Power Plants is high if the industry has to purchase extra land for Captive Power Plants.
- Skilled personnel to operate and maintain the captive power plant are employed.
- Storage of fuel may lead to problems.
- Small power plants emit more pollutants as compared to big power plants. Therefore, pollutants control measures a further increase in its cost.
- Small size plant is inefficient, especially at low loads.
Types of Captive Power Plants
- Steam Plant
- Gas Turbine Plant
- Diesel Engine Plant
- Co-generation Plant
- Hydro Plant
- Wind-Diesel Plant
1. Steam Power Plant
These plants are set up by large size and heavy industries. E.g. steel, aluminium, etc. which already have access to coal and necessary facilities for purchasing and storing coal. These plants are generally of around 100MW or larger. Some industries for e.g. sugar industry use the Bagasse as fuel in Captive Power Plants to reduce the generation cost. Bagasse is a waste dry sugarcane left over after sugar juice has been extracted.
Many sugar industries in Andhra Pradesh, Bihar, Uttar Pradesh, Gujrat. etc. have steam Captive Power Plant using bagasse as fuel. Generation of plants ranges from 1MW-25MW.
2. Gas Turbine Plant
It is suitable and used in large sizes. Some industries for e.g. Petrochemicals have easy access to gas and liquids fuels and therefore prefer captive power plant having gas turbine which uses gas and liquid fuel. For example
ONGC (Hazira, Gujrat – 59MW)
Reliance Industries (47.5MW in Narod, Gujrat)
Maruti Udhyoga (60MW in Gurgaon, Haryana)
3. Diesel Engine Plant
These are the largest number of Captive Power Plant. They are used in sizes of 1MW to 10MW. (sometimes 30MW or above).
Advantages of Diesel Engine Captive Power Plant
- low capital investment
- small space requirement
- quick starter time
- efficiency
Examples:
India cement (30MW plant, Khorappa, Andhra Pradesh)
Indian oil corporation (75MW, Panipat, Haryana)
4. Cogeneration Plant
A Cogeneration Plant may be steam gas turbine plant with based heat boiler combined cycle cogeneration plant, biomass fuel plant, diesel engine plant, etc. The basic idea is to use as much of the energy of the fuel as possible. The initial cost of a cogeneration plant is more than that of the electric power plant. However, if an industry requires both electricity and steam, the cost of installation of a separate steam generator is saved. Example
Arvind Mills (two-29 MW plants) gas turbine has a combined cycle captive power plant at Ahmedabad, Gujrat.
5. Hydro Plant
It is suitable for the industries located near the site for a mini-hydropower plant. It has the following advantages
- a low gestation period
- short starting time
- very low operating cost
- the absence of pollution
Thus it makes it a cost-effective captive power plant. Example
A 12 MW hydro Captive Power Plant in Kerala.
10 MW hydro Captive Power Plant in Karnataka.
6. Wind-Diesel Plants
If the industry is situated in an area suitable for wind development, the wind Captive Power Plant can be very economical, however, a wind plant always has a backup diesel plant to supply electricity needs during periods of low wind speeds.
The control strategy for the wind-diesel system is
- The energy of wind-electric generator is directly used by the industry as much as possible.
- the extra wind is used to charge the batteries.
- When load cannot be met by a wind-electric generator, the batteries meet the remaining needs. If storage is not sufficient the diesel generator is used to supply the deficient.
- If diesel generator is run, it is run at full capacity so that it operates at best efficiency. In case its full capacity is not used in supplying the load, the remaining capacity is used to charge the battery.
- Wind energy plant requires a huge investment(diesel and batteries further increase the cost).
