Is pumped storage the answer to electricity woes?
BY TOM NEVIN, MAY 04 2015
STORAGE is the golden fleece of the energy business. If science could find a way to store large amounts of electricity in a battery, energy prices would drop, reliability would be improved and availability would be constant.
It would deliver South Africans from what threatens to be a long nightmare of load shedding and other electricity blackouts.
SA is captive to the shortcomings of “use it or lose it” — more than 90% of our energy is generated in coal-fired power stations, with all its attendant production clumsiness. Blame it on history, a huge coal resource and the economics of the energy business we’re stuck with for another half-century or so.
Coal-fired furnaces to heat water to create steam to turn the turbines is the cheapest way for us to generate the 40,000MW of power we need now and much of the 80,000MW we’ll probably have to produce by 2030 if our gross domestic product growth model is to survive.
We can’t turn the fossil-fired furnaces on and off at the flick of a switch, so we create huge amounts of heat — even in off-peak times when we don’t need it. We’re in an energy wastage trap that will take decades to escape.
A method of storing energy has been around for 50 years or more and could ease our load-shedding darkness. Pumped storage offers the breathing space Eskom needs and the sensible thing to do is to instal much more of it as quickly as possible. Pumped storage is the only proven and reliable solution for grid reliability, providing large-scale, affordable means of storing and deploying electricity.
The system stores and generates energy by moving water between two reservoirs at different elevations. At times of low electricity demand — at night or on weekends — excess energy is used to pump water to an upper reservoir.
During periods of high electricity demand, the stored water is released through turbines, flowing downhill from the upper reservoir into the lower and generating electricity. The turbine is then reversed and pumps the water back uphill.
It can be operated for a set number of hours but then must be recharged — much like a battery. The time span is determined by the volume of water that can be stored in the reservoirs.
STEENBRAS Dam in the Western Cape can generate 180MW for a little more than 15 hours, while Eskom’s Drakensberg plant can generate 1,000MW for 26.5 hours. In terms of “recharge” time, it takes the Drakensberg scheme 34.6 hours to pump the 26-million cubic metres of storage water from the lower to the upper dam.
“The Department of Energy should indeed consider more pumped storage,” maintains David Easton, a retired civil engineering manager. “In the last 15 years Eskom has considered two new pumped storage schemes, Ingula and Tubatse,” he says.
Ingula is four years behind schedule and Tubatse has yet to move off the blueprint.
Ingula is on the Little Drakensberg escarpment near Van Reenen. It is nearing completion, and will produce 1,332MW. The 1,500MW Tubatse scheme, planned for the De Hoop Dam in Limpopo, is unaccountably on hold.
Eskom reports that Ingula is progressing. The dams should fill during the 2015-16 summer and commissioning of the first unit should happen in the first quarter of next year.
Although the Tubatse project has been engineered and environmental issues ironed out, it languishes at the point of execution, awaiting a decision from the department. The project does not appear on the list of Eskom’s build programme.
There has been speculation that Tubatse will be put out to tender to independent power producers, eager to exploit the experience gained from Ingula.
The curious reluctance by the government to involve independent producers in base-load, or big volume energy projects, has cost the country dear.
Tubatse could have been up and running by now, delivering a vital 1,500MW of peak power, while the Mmamabula Energy Project could potentially have sent 4,800MW of electricity flowing from just over the border with Botswana, at no capital cost to SA.
While the government acknowledges that independent producers could be mobilised to deal with the electricity crisis, such participation would be temporary, to be terminated after energy generation was normalised.
Easton believes it makes sense to have the Tubatse project built by an independent producer.
“An independent power producer would be able to develop the scheme at a lower cost than Eskom. Most of the expertise required to construct the caverns and tunnels at Tubatse is available within SA’s tunneling and construction industry,” he says.
“The experiences gained at Ingula can be fully exploited. With a two year lead-in time for concluding agreements, and a six-year completion period for commissioning all of the four pump turbines, in 2022 there would be 1,500MW of additional peaking power capacity.”
Easton believes that Tubatse should be ring-fenced, so that the government only has to finance the building of roads and other minor infrastructure. Eskom’s transmission division would construct the switchyard and transmission lines linking the grid to Tubatse.
“Some of the considerable number of actions that have to be taken, start with the process to invite competitive bids as was done for the renewable energy projects, the REIPPPP (Renewable Energy Independent Power Producer Procurement Programme) method.
“The 64 solar and wind projects under construction at present have given the South African engineering, banking and legal professions huge exposure to new forms of getting difficult power generation projects successfully negotiated and completed. The way forward is to complete the Tubatse Pumped Storage Scheme as an independent power project,” he says.
For the past decade, Eskom has been expanding its generation and transmission capacity to meet SA’s growing demand for energy. Ironically, the slowing economy has provided some breathing space for energy infrastructure installation, although not quite enough.
Eskom says that nominal generating capacity in 2005 was 36,208MW. It plans to increase this by 17,384GW by 2019-20, according to latest estimates. The key generation expansion projects are the 4,764MW Medupi and 4,800MW Kusile coal-fired stations, and the Ingula pumped-storage scheme. Transmission line length and substation capacity will also increase substantially.
THE capacity expansion programme has cost R213.2bn (excluding capitalised borrowing costs) to date.
Between 2005 and March 31 last year, Eskom’s generating capacity increased by 6,137MW, its transmission lines by 5,497km and its transmission substation capacity by 27,565MVA.
The US has about 20,000MW of pumped storage capacity countrywide with another 31,000MW in varying stages of delivery. As SA’s energy supply crisis deepens, new thinking is emerging on how municipalities can better secure their electricity needs in the light of diminished and unstable power generation from Eskom.
The Cape Town metropolitan council hopes to open discussions soon with Energy Minister Tina Joemat-Pettersson on new ways to ramp up a more secure power flow.
“Cape Town is one of the first cities to promote embedded generation and we are investigating ways in which this programme can be ramped up to bring more electrons on to the grid through renewable energy,” Cape Town executive deputy mayor Ian Neilson says.
“The feasibility of implementing our own demand-response system, whereby businesses can be contracted to reduce demand immediately as opposed to having to implement load shedding, is currently being investigated.”
Among the energy-adding options being considered by the city is a complementary electricity flow from the Steenbras pumped storage facility. This entails changing the operation priority for the scheme as a way of reducing load shedding rather than to save on peaking power costs.
The 40-year-old installation is currently being refurbished.
Neilson regards the involvement of independent power producers as vital in securing supply.
“The key issue is whether or not the minister would allocate a portion of the independent resources plan to the city to enable it to contract directly with an independent producer,” he says.
“We hope to get clarity on this matter soon. It is potentially feasible that we could piggyback on the Department of Energy’s independent power producer process if the minister agrees, thus simplifying processes. We are open to all options.”
For this article & more visit www.BDlive.co.za