Doctor and activist

A Response to the Libs’ Energy Plan

19 October 2017

The energy plan proposed by the Lib/Nat government has several major flaws based on either their poor understanding of how an electrical network works or wilful misrepresentation.  It is a government sanctioned, long term price fixing agreement.

The current plan is to force energy retailers to buy a minimum amount of energy from “reliable” thermal plant to ensure reliability by reducing the input from “unreliable” renewables. The plan is not a surprise as the thermal plant owners had a big input into it. This effectively puts a base price on energy of about $85 per MWh i.e. the typical wholesale price of power from at thermal plant.

The government confuses reliability with despatchability.

Reliability is a measure of whether a power source will be working over some specified time interval.  A better metric is availability i.e. the time period over which the power source is performing within acceptable parameters.

Modern well maintained thermal power stations have availabilities in excess of 95%.  But for example if Liddell which has 4×500 MW turbo generators has only been able to keep 3 running consistently its total availability would be 95%x0.75 =70% i.e for 70% of the time over the last few years it has been able to despatch, supply when needed 4×500 MW. Its capacity to despatch 3 x500MW has been 95%. Actually Liddell’s performance has been much worse than this.

Base load is the Coalition’s other favourite subject. It takes about 8 hours to start up a large thermal power station and about 12 hours till it comes up to full capacity. These times are dictated by differential expansion of its components. Hence normal practice is to keep these units running continuously. They also exhibit stability problems when run at less than 30% capacity. At night when the demand for electrical energy drops, continuously running operations like steel mills, aluminium refineries, cement works etc. took up this load generally this was not enough to keep the load above 30% hence the low off peak rates offered for water heating.

The problems of differential expansion also mean that thermal plant cannot respond quickly to changes in load especially load increases.

The above limitations meant that in a system dominated by thermal plant you have to keep enough older plant running at low load so that it could take up the power of the largest unit in your system should that unit be forced to shut down in an emergency i.e. trip. This is system spinning reserve.  So the price will be set by the needs of the old fossil fuel plants. This will keep the coal owners happy. It will also keep the renewable generators happy as the high price will give them a massive profit margin. It will keep Labor happy, as thye can make a magnanimous gesture of bipartisanship and when they come in there will be lots of renewables built to get the huge profit levels that have been there for the taking. 

The people who will not be happy will be the industries that will go broke because unnecessarily high power prices made them uncompetitive, and the long-suffering homeowner.

Renewable energy power systems and hydro have different characteristics. Hydro is despatchable if you have sufficient water. Australia’s lack of water means that all of our large hydro stations do not operate continuously. They are mainly used to handle short and medium length load peaks as they can respond quickly to load changes. Naturally if the water were pumped up when there was spare power they would act as batteries.

Wind and PV systems are not fully despatchable as their output is dependent on wind strength and sunlight.  They can respond quickly to load changes.

Their availability here in Australia is much, much better than the Liberals would have us believe and our ability to forecast wind in the medium term is now very good.  Hence their availability is quite high.  We can also use concentrated solar thermal plant. Here a heliostat field of several hundred hectares is used to concentrate sunlight onto a boiler mounted in a tower to heat a transfer medium, typically sodium carbonate to about 400 deg.C. The molten salt is pumped into a storage tank and then pumped through a heat exchanger to generate steam which drives a steam turbine. One such plant is planned for the head of Spencers Gulf in SA. Here the energy is stored as heat and the molten salt can be drawn from the hot tank to generate steam on demand i.e. the plant’s capacity is despatchable.

For example a wind farm costs about M$2.00 per MW to install. A 1MW unit running at 40% capacity factor, most wind sites do better, will then generate about 3,500MWh pa at $85 per MWh this will be $300,000. Assuming capital costs of say $85,000 and service and maintenance of $84,000 this leaves a surplus of $207,000 a very good financial result especially when you compare this to a thermal plant which will cost about M$30 per MW to build and take 10 years in the building compared to about 3 years for a wind farm.

Older thermal stations like Liddell are worn out especially their boilers which from a large part of the capital cost the boiler tubes suffer from stress fatigue and start developing fractures. Coal and ash handling plant starts to wear out and even the turbine blades erode due to the aggressive operating temperatures. Eventually the combination of wear and loss of availability makes them uneconomic. Try keeping a 40 year old car road worthy if you use it as a taxi.

Arthur Chesterfield-Evans

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