Wed, Aug 30, 2017 - Page 8 News List

Developing virtual power plants

By Lu Chan-nan 盧展南

Energy policy has two main principles — reasonable rates and a stable supply. Despite coming under considerable pressure, the government has resisted increasing rates.

However, following the area-by-area rolling blackouts that were imposed earlier this month, businesses and the public are not impressed by the government’s efforts.

Furthermore, the persistently insufficient reserve margin, as well as the recent massive power outage, have reinforced people’s impression of electricity shortages.

There are two ways to make the electricity supply more reliable: improve the electricity supply structure, and maintain a reasonable power reserve.

Taiwan Power Co (Taipower) sets its operating reserve low. Under such conditions, it has instituted an emergency voluntary demand response system, which electricity companies in other countries consider to be the most effective option. This functions as a virtual power station that serves to reduce electricity consumption and increase the reserve margin.

According to system requirements, Taipower notifies users before 6pm on the day before curtailing electricity supplies, advising them to reduce power use. The minimum suppression contract capacity is 50 kilowatts. This system has been in force for two years.

Although it has been extended to include real-time (on-the-day) bidding, as well as day-ahead bidding, only those classified as high-voltage users or higher can submit bids, while those who opt for three-period, peak-time adjustable time-of-use rates cannot take part.

Furthermore, due to insufficient publicity, many factory operators do not know or understand how to take part in the program and because of various limitations imposed by Taipower and its unwillingness to offer sufficient incentives, such users are not willing to change their production schedules and electricity-use habits.

Consequently, there has been little growth in the use of emergency peak load reduction and it played no role in responding to the N-6 whole-plant generator shutdown.

If we hope to enlist the help of electricity users to improve electricity-supply security by avoiding inadequate operating reserves, we must be willing to cover the additional construction costs needed to achieve that degree of electricity-supply security.

There is no need to worry too much about participants taking advantage of the system. At this time of energy resource transformation, there is a need to buy back power capacity at reasonable rates, because if the system does not provide adequate real-time operating capacity response, it will cause the system frequency to fall too low, making it necessary to restrict electricity supplies.

This month’s rolling blackouts showed how great an effect the rare event of a shutdown of all generators in a major power station combined with inadequate rapid-response operating reserves would have.

If as many generators were to shut down in winter, when there is a relatively light load, it would have an even more serious effect. When the system frequency falls to a certain level, generator protection measures cause a shutdown. If the low-frequency situation were to persist, it would set off a chain of shutdowns, the result of which would not just be local rolling blackouts, but a nationwide power outage.

Power grids are one of the greatest systems that humankind has created. The system operates like the interconnected gears of a machine. Electricity generation and consumption must be kept in regular equilibrium to stay within the frequency range needed by high-technology industries.

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