Posted by: Saving Water SA (Cape Town, South Africa) – partnered with Water Rhapsody conservation systems – 29 May 2011
Eskom wants to build a new 2 100MW power station, making use of new underground coal-to-gas technology.
Since 2007 the power utility has been working on the technology and hopes to start designing the new macro power station by December. This week Barry MacColl, Eskom’s manager for technology, strategy and planning, told Sake24 that the success of the technology has already been demonstrated. The trials had produced satisfactory results and the potential was tremendous, he said.
In the technology process two shafts are drilled into underground coal reserves. Then the coal – which is underground – is set alight. The burning coal releases, through the one shaft, a flammable gas which is collected and redirected to gas turbines that generate electricity.
MacColl said the underground reaction is controlled by regulating the quantity of oxygen being pumped into the one shaft, and the process can be altered by cutting off the oxygen supply.
Eskom’s test project at the Majuba power station is already contributing 3MW of power to Majuba’s total output.
Chris Yelland, an independent engineering analyst, said that very little is still publicly known about the technology. The technology was developed in the Soviet Union and used there, he explained. The biggest experts in this area would be Russians.
The research started in the 1930s and was conducted aggressively until large underground gas resources were discovered in the former Soviet Union. The biggest commercial project using the underground coal-to-gas technology was developed at Angren in Uzbekistan. In the West it was largely America that researched the technology.
Yelland said that while he was somewhat sceptical, the concept nevertheless offers a number of advantages. The biggest of these, he said, is probably that coal that was previously regarded as unexploitable, could now be used.
This, Yelland said, is a particular problem at the Majuba power station where the coal in the environment cannot be exploited for use in conventional power stations.
Further advantages are that there is less exhaust-gas pollution than that from ordinary coal-fired power stations. For instance, the ash problem that ordinary coal-fired power stations have to deal with is absent.
Tristen Taylor, spokesperson for the environmental group Earthlife Africa, said there were still too many unknowns about the technology.
For instance, he said, there were questions about what would happen to underground water tables. A bigger issue, however, was that the technology would be more expensive than some sources of renewable energy. Why, he asked, would Eskom not rather spend the money on developing wind farms. That technology, he said, had been demonstrated and was available.
Eskom already operates gas turbines in, for instance, Atlantis and Mossel Bay, but those turbines use diesel. As a consequence their production costs are tremendously high – about R1 600 per megawatt hour (MWh). Eskom’s average production cost is around R250 per MWh.
Underground coal-to-gas turbines are expected to run less expensively than diesel-driven turbines. The 2 100MW project is expected to use a closed-cycle gas turbine system, which is more effective.
No one is sure where developments of this type of project would slot into government’s Integrated Resource Plan (IRP2010). The project could possibly be classified as either gas or coal. But for Eskom it would prove worthwhile, because over the next 20 years the power utility will struggle to supply sufficient electricity for the country’s needs.
Only this week Eskom announced that the country’s power grid was under pressure. While load-shedding was not on the agenda yet, consumers were asked to use electricity sparingly. Should Eskom work according to plan and start designing the project at the end of this year, the first electricity could be delivered by March 2020.
The full 2 100MW power station could be completed by September 2022. Eskom’s budget for the project is around R1.5bn up to 2013.