Generation of Electrical Power Questions and Answers

Answer: B

As the load factor increases, the cost per kWh decreases.

The cost of generation has a fixed part (interest and depreciation on the plant, which depends on its capacity) and a running part (fuel, which depends on the energy generated). A higher load factor means the same plant produces more energy over the year, so the fixed charges are spread over more units and the cost per unit falls.

The fuel cost per unit stays roughly the same, so there is nothing to make the overall cost rise, and it does not stay unchanged because the fixed cost per unit falls.

Answer: B

The demand factor is 1/2.

Demand factor is the maximum demand divided by the connected load. The annual generation figure is not needed; it would be used to find the load factor.

\[ \begin{aligned} \text{DF} &= \frac{20\ \text{MW}}{40\ \text{MW}} \\ &= \frac{1}{2} \end{aligned} \]

2 is the ratio turned upside down; demand factor is always less than or equal to 1, because the maximum demand cannot exceed the total connected load.

Answer: C

Nuclear power stations are used for base load.

A nuclear station has a very high capital cost and a very low fuel cost per unit, and its reactor cannot be ramped up and down quickly or economically. It is therefore run continuously at a steady, high output to supply the base load, the minimum demand that is present round the clock.

Peak loads, which last a few hours and change quickly, are met by plants that start and change output easily, such as hydro, pumped storage and gas turbine stations. Using a nuclear plant for peak or fluctuating load would waste its capital and is technically awkward.