By Andrew Castrique
The other day, as apparently all good Australian Democrats regularly do, I went to the bottom of my garden to consult with the fairies.
To my surprise, they were gone, leaving a note and forwarding address. It read:
Gone to the Fairies Festival.
c/o Bottom of the Garden, Liberal Party Canberra
So I gave them a call on my fairy phone to find out what is going on.
It all started last year, when South Australia had a massive storm, bringing down three of the four major high voltage power lines coming from the north of Adelaide. The resultant voltage fluctuations caused some of the remaining connected wind farms to trip out, overloading and tripping out the only interconnector to Victoria.
“It’s renewables,” screamed pollies in Canberra immediately. “SA should never have closed the coal –fired generator at Port Augusta.”
(Fairies please note – It was those high voltage power lines brought down in the storm that would have supplied power from the Port Augusta coal plant. Electricity can not be delivered via the ground.)
(P.S. The coal for Port Augusta was supplied from the very, very poor quality brown coal at Leigh Creek – the only coal in SA. Unlike the horizontal coal deposits in the eastern states, Leigh Creek coal seams slope downwards, requiring an ever larger volume of overburden to be removed to access it. Back in the 1980s, ETSA (then government-owned Electricity Trust of SA) estimated that the coal fields would no longer be economical to mine, and would be closed by 2017. The coal fields closed a couple of years early.)
So now our PM and various Ministers are plugging a return to coal, and specifically “Clean Coal”.
They talk of good, reliable, cheap, and with modern technology “clean”, super-critical plants, and carbon capture and storage (CCS), with the advantage CCS can be retrofitted to existing coal fired plants.
What are “super critical plants” and CCS, and why are they better than our existing plants? (Fairies – To understand the following, a little physics. A tonne of coal will release a certain fixed amount of energy when burned. When put through any power plant, some of the energy will be converted to electricity, the rest is lost as waste heat. The maximum possible efficiency of the conversion is strictly governed by the temperature difference between the hot end and the waste end. So the higher the steam temperature, the greater the efficiency and the greater the amount of electricity from each tonne of coal. A bog standard coal plant runs at about 30% efficiency.)
In Australia’s coal-fired plants, coal is burned to generate steam in a boiler. The steam is fed into a turbine connected to a generator. Simple, quick, reliable, and cheap to build, with lots of CO2 for the amount of electricity generated.
Super critical coal-fired plants operate at a far higher steam temperature than the regular plants, giving higher efficiency and more electricity for the same amount of coal. We have two of these plants operating in Queensland at the moment. The problem is, above about 600degC, steam starts to penetrate steel, making it brittle. To build and operate a super-critical plant is more costly. (Fairies – Read “more expensive electricity”)
The next step up is combined cycle with coal gasification (the Ministers have not talked about this one). For this process, the coal (or any organic material … chance to add renewables here, organic rubbish, sewage solids, agricultural waste) is converted to gas using the same process used to make town gas before natural gas came in. Part-burn coal with steam and restricted air to produce carbon monoxide and hydrogen gas. This is then used as fuel for a gas turbine. The exhaust from the gas turbine is still hot enough to heat a small steam boiler and turbine. The initial temperature reached in the turbine is well over 1,000degC giving a far greater efficiency. A typical plant can convert over 50% of the energy to electricity. With the record at over 60%. (Fairies – Very expensive to build and run. Only used in countries with expensive imported coal. Only needs a little over half the coal for the same amount of electricity as our bog standard units.)
And then comes Carbon Capture and Storage (CCS). The most promising method starts with a combined cycle with coal gasification plant. The gasified coal (carbon monoxide and hydrogen) is further steam and heat-treated to produce carbon dioxide and hydrogen. The carbon dioxide can be (relatively) easily separated from the hydrogen, and taken off to be pumped underground for permanent storage. The hydrogen continues as the fuel for the rest of the plant.
(Fairies – This is a VERY expensive power plant to build and run. According to Energy Minister Josh Frydenberg, CCS systems can be retrofitted to existing coal plants. As none of our plants have coal gasification, the carbon dioxide would have to be extracted from the flue gas – a VERY difficult process. And starting with a standard coal- fired steam generator requires extracting twice as much carbon dioxide per unit of electricity compared to combined cycle with coal gasification.)
And now the elephant in the room. The proposed “clean” coal, CCS plants and retrofits, are costly to build and run. So think expensive electricity.
If electricity generators were still run by government, they could be built by government decree. But our generators are privately owned. The system is “for profit”. So why would anyone invest in expensive power plants that generate electricity at prices far above standard coal plants? Electricity so expensive that no one would want it. Answer – A substantial price on carbon (at least for electricity generators). Either as a straight carbon tax, or an emissions trading scheme, to level up the price of standard coal with CCS plants, making “clean” coal plants the more profitable (ignoring the continued rapid decline in the cost of solar, and the extra advantage a carbon price gives renewables).
So Mr Turnbull, carbon tax or emissions trading scheme? Without a substantial price on carbon, talking about new coal generation is about as silly as … talking to the fairies at the bottom of my garden.
P.S. I don’t believe in fairies (sorry Tinkerbell).
Andrew Castrique works in science education in SA, and is a Deputy National President of the Australian Democrats.