Demand Side Management Questions and Answers

Answer: C

Sorting the year's hourly demands in descending order shows at a glance how few hours the peak capacity is needed for, which is the argument for peak clipping. The chronological order is lost, so the curve cannot show when the peak occurs.

Answer: D

Correct answer: energy consumed over the period

The load duration curve plots demand against the time for which it is equalled or exceeded, so the area under it is power multiplied by time - energy. Its height at the left gives the peak, which sets the capacity required, so the curve shows the two quantities that matter in one picture.

Answer: A

Correct answer: average demand to its peak demand

\[ \mathrm{Load\ factor} = \frac{\mathrm{average\ demand}}{\mathrm{peak\ demand}}. \] A high load factor means the plant built for the peak is used most of the time, so the fixed costs are spread over more units. Raising it is the object of nearly every demand side measure.

Answer: B

Correct answer: the maximum demand of the group as a whole

\[ \mathrm{Diversity\ factor} = \frac{\sum \mathrm{individual\ maxima}}{\mathrm{group\ maximum}}. \] It exceeds one because consumers do not all peak at the same moment, and that is what allows a feeder to be rated well below the sum of its connections. The larger and more varied the group, the greater the diversity.

Answer: C

Correct answer: the reciprocal of the diversity factor

\[ \mathrm{Coincidence\ factor} = \frac{1}{\mathrm{diversity\ factor}} = \frac{\mathrm{group\ maximum}}{\sum \mathrm{individual\ maxima}}. \] It is a fraction not exceeding one and says what proportion of the connected maxima actually coincide. The two express the same fact in inverted forms, which is why quoting which one is meant matters.

Answer: D

A tariff that switches every water heater on at the same off-peak hour creates a new peak of its own, which is a well documented failure of crude time-of-day design. Staggering or randomising the switching preserves the diversity.

Answer: A

Time-of-use, critical peak and real-time pricing all leave the decision with the consumer and rely on the price signal reaching someone able to act. Incentive-based programmes instead pay for a commitment or take control directly.

Answer: B

Correct answer: only on a limited number of days declared in advance

Critical peak pricing concentrates a very high price into a handful of events a year, called when the system is genuinely stressed, with the rest of the year on an ordinary tariff. Because the events are few, the consumer can respond strongly to each, which yields more reduction than a modest premium applied every weekday.

Answer: C

Correct answer: the wholesale price as it varies hour by hour

Real-time pricing passes the market price straight through, so the signal is exact and the consumer sees the true cost of consuming at that moment. The difficulty is exposure: prices can rise by an order of magnitude in an hour, so the arrangement suits consumers who can respond and can bear the risk.

Answer: D

Air conditioners and water heaters are cycled for short periods under an agreement that gives the consumer a rebate, and the load reduction is immediate and reliable. The consumer surrenders control rather than responding to a price.