• Base Load and Peak Load

    The load on any power plant can be considered into two parts namely, Base Load and Peak Load. Load in a power system varies all the day. Electrical power generated by the generating stations depends on the demand for electrical power. During day time demand for electricity will be more and hence all the generating units will be running under full load. During nights, load on the generating stations will be less. The unvarying load which occurs almost the whole day on the power plant is called the base load. Whereas the various peak demands of the load over and above the base load of the power plant is called peak load.


    If the load represented in the figure is to be supplied by the single power plant only, the installed capacity of the plant should be equal to the peak load demand or more. Such a power plant is uneconomical since the peak load occurs only for a short duration in a day or in a year. Hence such a peak load should not be supplied from a single power plant. Therefore there should be an optimum mix of the power plants which supply the base load round the year and some other power plants of different type supply power to the peak load. Thus the co-ordinated operation of different power stations is essential.



    Base Load and Peak Load Demand Diagram


    Base Load Power Plants: The power plants to be employed as base load plants should have some of the characteristics:

    1. Low operating cost

    2. High efficiency

    3. Capability of operating for longer periods

    4. Maintenance should be simpler and requires less time. Time duration between the maintenance should be long

    5. Requires few operating personnel


    Peak Load Power Plants: The power plants to be employed as peak load plants should have the following capabilities:

    1. Quick start

    2. Faster synchronization to the grid

    3. Should be faster in taking up the system loads

    4. Quick response to the load variations

    5. Plant having low efficiency is acceptable.


    Hydroelectric power plants are well suited for both base load as well as peak load operational plants. The hydro power plants should be employed for base load operations as far as possible because of their higher capital cost. However during the period of draught or in summer season, the hydro power plants may be used as a peak load power plants.


    Steam power plants or thermal power plants gives minimum cost of generation per unit when employed as base load plant. However, in order to save the fuel it may be used to run as peak load plants in some circumstances.


    Nuclear power plants are suitable only for base load operation. Nuclear power plants have the highest load factor of over 0.8 to 0.9.


    Gas turbine power plants are best suited for peak load power plant operations.


    Diesel engine power plants are generally will have higher operational costs and is uneconomical to operate them continuously. Diesel plants are mostly operated as peak load plants.