Economics in Plant Selection:

Economics in Plant Selection – The plant capacity and size depends upon the power demand. A power plant should be reliable i.e. its capacity must be more than the predicted maximum demand. It is desirable that the number of generating units should be two or more than two in order to use the capacity of the plant efficiently. Generating cost for large size units running at high load factor is considerably low, however, the unit has to be operated near its point of maximum economy for most of the time through a proper load sharing programme as too many standby will increase the capital investment and rise the over all cost of generation.

In a steam power plants, the thermal efficiency and operating cost depend upon the steam conditions like throttle pressure and temperature. Also addition of boiler accesseries like economiser, air preheater, superheater increases the efficiency of the boiler. Boiler accessories cost has to be balanced against the gain in the operating cost.

In hydel power plants, power can be produced at low operating cost provided water should be in abundant. If the quantity of water available is small, then the capital cost per unit will be high as installation of hydel project involves large capital expenditure.

The nuclear power plant should be installed in an area having limited conventional resources, it must also be noted that the plant located should be in remote or unpopulated area in order to prevent the damage due to radioactive leakage during operation as well as any unpredicted hazards. Disposal of radioactive waste may be another issue which demands abundant of water at the plant site. The capital investment in a nuclear power plant is large as it needs a large area to accommodate itself and a large capital for its operation and maintenance.

The diesel power plant is best suited for the areas where resources like land, water, etc., are an issue. They can be easily located in the load centre. The choice of the diesel power plant depends upon the thermodynamic consideration. The efficiency of the engine increases with higher compression ratio. Diesel power plants are quite suitable for areas where small output without interruption is needed like cinema hall, hospital, malls, industries, etc.

The gas turbine plant is also suitable for small output. The cost of gas turbine plant is relatively low as compared to diesel power plant, but its capital increases with the addition of equipment’s like generators, reheater and intercooler. The above cost is balanced by the improvement in efficiency of the plant. The plant is widely used in regions where gaseous fuel is available in large quantities.

During the operation, there is a variation in load according to the demand, therefore prime mover and generators have to act fairly quickly to take up this variation of voltage of the system. This requires that supply of fuel to prime mover should be carried out by the action of a governor. Diesel and hydro-power plant are quick to respond to load variation as the control supply is only for the prime mover, where as in steam power plant the control is required for the boilers as well as turbine. Further to cope up with the variable load operation, it is necessary for the power station to keep reserve plant ready to maintain reliability and continuity of power supply at all times.

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