Eskom is short of generation capacity, particularly over peak periods. While possible to meet reserve margin needs with costly gas turbine generation plant, another more preferable initiative based on voluntary customer load curtailment (NegaWatt generation) was needed.
We developed and implemented a Virtual Power Station (VPS) for Eskom in 2007 as a mechanism to incentivise customers and enable them to reduce load over critical periods.
Eskom uses the VPS as a means to schedule all its controllable demand side resources and view available customer NegaWatts. A variety of Demand Response (DR) programmes are being catered for within the VPS, including customers with standby generation and ripple control systems, and a number of Eskom’s largest customers in an interruptible load programme. The VPS interfaces with the Eskom National Control Centre and manages all Eskom VPS customers’ availability, scheduling, dispatching and the gathering of metering information, event performance measurement, settlements and reporting.
The approach taken in creating the VPS was to make it indistinguishable from physical power stations from an operational point of view. Thus, when additional load is needed because of an unexpected shortage or an expected peak, the Eskom System Operator (SO) can dispatch the VPS as it would an emergency or supplemental generator.
While currently only Eskom’s large customers are being utilised within the VPS, Eskom is planning to expand its DR initiatives to include smaller industrial and commercial loads under its now well publicised Demand Response Aggregation Pilot Programme. Residential load can also be incorporated within the VPS, particularly when integrated with smart metering systems. Numerous pilot and small scale projects are being undertaken within municipalities and Eskom. Other potential participants are customers with standby generation, e.g. backup diesel generators.
Apart from being the cleanest energy source available, the VPS can be deployed faster (under 10 seconds) than any physical energy source of similar capacity, and can quickly modify its capacity and energy delivery capability. The effects of supply from the VPS are geographically distributed, thereby reducing network constraints where required.
The NegaWatt generation capacity available through the VPS has a significant cost saving over gas turbine generation plant, and avoids load shedding. More than 1 000 MW of customer load is certified and available for dispatch.
There has been much focus in recent years on the ‘smart grid’ which achieves distributed control through a network of automated real time load monitors and switches, e.g. smart meters which automatically limit load under certain network conditions. The VPS would in time interface with these systems, thereby adding to the MW available for dispatch.
Substantial growth in the number of MW under VPS control is anticipated over the next few years, with the full potential of the VPS and DR in general still to be realised. The Virtual Power Station will play a key role in South Africa’s smart grid architecture of the future, enabling Eskom to optimise usage of its electrical network in an environmentally beneficial manner.