There are more than 20 pumped hydro projects in five Australian states at various stages of development, with some in initial assessment phases and others under construction. If these projects go ahead, Australia will be well on the way to have a national grid that could rely almost entirely on renewables, finds a new study from the Australian National University (ANU).
“It’s really a game changer. It destroys any argument that solar and wind can’t provide the baseload power needed to keep the lights on in eastern Australia,“ says researcher Jamie Pittock.
Pumped hydro stores energy for when the grid needs it by pumping water up-hill when demand is low and then releasing it down pipes through a turbine to generate electricity when demand is high. Optimal locations feature pairs of dams with an altitudinal difference of more than 250m, and exclude residential areas, national parks and other sensitive places.
Pittock’s paper, which has been published in Australian Environment Review, outlines the environmental implications of this system. He says it does throw up some unusual challenges, as people living in rural areas could be displeased to see a reservoir being built on top of the nearest mountain. On top of that, a lot of high elevation areas that would otherwise be suitable have to be ruled out as they are a part of a national park or host culturally significant sites. Other sites are too far away from water or existing electricity transmission lines.
But, there is a number of sites that are really promising, including everything from old quarries, such the old gold mining tunnels under Bendigo in Victoria that are sucking the contaminated water up to the surface and feeding it back down the mine shafts, to doubling existing pumped hydro schemes and a “green” steel mill.
“Estimates are that we would need about 20 big PSH facilities to back up the entire national grid. It’s partly a judgement call about how much risk you want to take in terms of the reliability of the electricity supply,“ Pittock said.
Pumped hydro recently grabbed the limelight as the federal government announced its plans to underpin two major projects. It pledged $1.38 billion in funding for the Snowy 2.0 pumped hydro expansion, along with $56 million for the Marinus Link project, part of Tasmania’s Battery of the Nation program, which would provide a second interconnector across Bass Strait to increase the availability of the state’s hydro resources on the mainland.
While analysis showed that additional energy storage capacity makes financial sense in the light of coal retirements, and for the Marinus Link well ahead of schedule, it has been underlined that the potential of these pumped hydro projects can be fully exploited only when they operate in concert with renewables.
“Don’t talk about Snowy 2.0 being renewable, when every time it pumps, it will be using off peak power from the dirty power stations we have in NSW today. They need to close, they fall over when the going gets tough in extreme weather, it’s time to move on into the 21st century with renewables, so Snowy 2.0 can truly be a renewable project,” the Climate Council’s Andrew Stock observed in a statement.
The same is needed for the Marinus interconnector to stack up. In an initial study, TasNetworks estimated the capital cost of the Marinus Link would range from $1.3 – $1.7 billion for the 600 MW link or $1.9 – 3.1 billion for 1200 MW of capacity. Noting that the project is looking promising, ARENA underlined the initial findings and indicated a second interconnector could become economically feasible in the early 2030s or as early as the mid 2020s – depending on when existing coal fired power stations retire.
“The second interconnector with Tasmania only works if the coal closure rates increase and we have an over 50% reduction in emissions from the electricity sector – not the 26% that the Government has been charting,” Ben Oquist, Executive Director of The Australia Institute stated following the funding announcement.
The Marinus Link has emerged as an early winner of the Underwriting New Generation Investment Program. Prime Minister Scott Morrison has indicated that there is a willingness to funnel taxpayers money into the project and Tasmania’s Hodgman Government promising to allocate $30 million for Hydro Tasmania to narrow the number of potential sites for the interconnector from 14 down to three.
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Pumped Hydro Tasmania using Cethana Dam for an example.
Dam height 113m so from the bottom to over the top minimum 120M Head.
Generating power 100MW one turbine at 90- 100% load. Normally run at 60% load.
Water through the turbine 375,000M3 (cubic metres, 1,000 ltrs = 1cubic metre) per hour.
Or 375Million lts
So if we are going to use pumped hydro here then for the 8hrs of low power use then we have to pump back 375 X 8 = 3,000mega litres for that period.
It would take at least 6 pumps at 63ML/hr using 20MW of power each to do the task.
These pumps are huge and weigh a lot and the Motors even more several tons each.
The power requirements of 20MW would most likely to be 3.3Kv, 6.6kv or even 11kv that is 11,000volts and 20million Watts.
Then you would need to construct a coffer dam below to hold 3,000 million litres for this to be pumped back, the reason for the coffer dam is to hold the amount of water required for the pumping for 8 hrs, and to have a flooded suction for the pumps. (Flooded suction is the term used for the pump input to be under water.
Then you would have to have large diameter pipes around 600mm diameter.
So you see the cost and the task is not easy.
The pumps could cost up to a $1M each and the same for the motors then you have the control equipment.
So 120MW of power per 8hrs 960MWhs at the going rate of $30/MW is $28,800
Then you have the lost revenue over that period at the same price another $28,800,so the total cost for that nights would be $57,600.
Over the next 16hrs you will need to recover the cost.
Over 6,000homes this would require 1.5 to 2 cent rise per kwh. Or you run at a loss.
Then you have to raise the capital cost of $150M over the same homes as this is where the power was used.
So somewhere taxes will go up to recover the cost.
To me this does not look like a viable process.
As a contractor to bid on this my pricing would be more like $250-300M the later as I know the terrain and worked on that dam project from beginning to the end . The government costing per MW of $1.2 – $1.5 is way out.
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