Owing to uncertainty surrounding South Africa’s electricity supply, it is important for State-owned power utility Eskom to conform to legislation that governs emission limits, as forced shutdowns of its gene- rating units is not an option for the country.
As a result, engineering and information technology company Invensys Operations Management and information technology provider Bytes Systems Integration helped Eskom implement a comprehensive emissions monitoring system to better supervise and control its emissions.
The emissions monitoring system is based on software that was supplied by Invensys Wonderware in 2011 and currently forms part of the integrated generation control centre (IGCC) that was provided to Eskom in 2010.
Every power station has an emissions licence with which it needs to comply. This ensures that the environment and health of people in the vicinity of power stations are not affected negatively. The emissions licence specifies two limits – a normal operating limit, which states that emissions must be below this limit 96% of the time – and a cap limit, which emissions must never exceed.
Eskom senior consultant Kristy Ross says control room operators at power stations must be constantly aware of potential problems which might result in emissions exceeding the set legal limits.
“If such an event occurs, it might be necessary to exercise load loss. This will have a ripple effect, as other power stations will be required to pick up the slack by ramping up production. Given the scope of the problem and Eskom’s nationwide footprint of 13 operational coal-fired power stations, it was decided that emissions status should be centrally monitored and controlled in real time,” Ross says.
The system runs on a Microsoft platform and collects data, including emissions levels, from all Eskom’s power plants, after which it is sent to a central control room at the utility’s Megawatt Park head office, in Gauteng.
Invensys technical director Deon van Aardt says Eskom now has a central platform that provides an overall view of its fleet of generators.
The emissions monitoring system also helps stabilise the electricity grid and reduce downtime of generators, as it provides an early warning in the event of emissions exceeding the legal limits.
Van Aardt says Eskom has the ability to connect to installed equipment at each generating stack, which monitors the ash emissions in real time.
This information is then captured by a database, which the utility can use to draw a graph of the emissions. This graph is then logged into an operational historian that captures the data at a high-rate on plant level. The ArchestrA System Platform, which forms part of the main system, collects all the information and provides Web-based visuali- sation for the IGCC, which can be accessed using Internet Explorer.
At the IGCC, Eskom has set up dashboards and reports. The dashboards show a live view of the operations and provide the emissions levels. From there, Eskom can draw reports to make an analysis and strategic decisions, take corrective action or shut down the generating plants, if needed.
“You have to get the right information in the right context and, by having a mechanism that enables someone to rapidly and easily collect plant information and put it in the right context, operations can run more efficiently. In this case, it is environmental data being collected to control emissions, so Eskom can make deci- sions quickly if needed,” Van Aardt says.
The emissions information can also be accessed from mobile devices, while the monitoring system also provides a warning, should emissions begin to exceed the legal limit. This enables Eskom to quickly take preventative measures.
The system also has the capability to escalate information to other Eskom personnel, if the primary person is not available.