LNG or Electricity? Find out!

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Re: LNG or Electricity? Find out!

Postby Warpspeed » Fri Apr 18, 2014 1:32 pm

Smurf1976 wrote:According to AEMO (Australian Energy Market Operator), maximum gas demand in Victoria for 2013 was on 24 June at 1200.4 TJ (terajoules) of consumption.
21.4 TJ of LNG was used on that day

So less than 1.8% was LNG the rest from Longford.
Hardly seems worth the trouble.
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Re: LNG or Electricity? Find out!

Postby Smurf1976 » Fri Apr 18, 2014 7:38 pm

Warpspeed wrote:So less than 1.8% was LNG the rest from Longford.
Hardly seems worth the trouble.

I think the point is that regardless of where it came from, consumers were going to take that gas out of the system therefore it has to come from somewhere.

And if Longford had cut production by, say, 30% due to a breakdown etc then consumers would still have burnt the same amount of gas.

Last decade Hydro Tas was buying "interruptible" gas from Longford to run the Bell Bay power station (Tas). Basically they only got gas when there was supply available that wasn't needed by someone else, and in return they got it cheaply. Since they were just using it for energy generation, and didn't need the peak capacity of the gas-fired plant just the energy output (to avoid the dams running dry), an intermittent supply was acceptable.

How reliable was it? Between breakdowns at the (somewhat antiquated) power station and interruptions in the gas supply, operation was anything from a couple of days to a couple of months before abruptly coming to a halt then restarting. Despite aiming for baseload operation, if you graph the output then it's all over the place - on, off, up, down. Such is the downside of buying cheap gas.

This was done for 6 years from 2003 to 2009. Prior to 2003 the plant was oil-fired (heavy fuel oil) complete with 3 tanks holding about 50 million litres of oil and it's own wharf for the tankers. Half of it was very abruptly closed in late 2008 following a major failure, and the other half was closed in running condition in April 2009 when a new power station came online.

My point there is that it seems that Longford does run short on capacity at times.
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Re: LNG or Electricity? Find out!

Postby Warpspeed » Sat Apr 19, 2014 7:46 am

Smurf1976 wrote:And if Longford had cut production by, say, 30% due to a breakdown etc then consumers would still have burnt the same amount of gas.

Longford cannot cut production by 30%, it either runs flat out or is shut down.
It fires up intermittently as load requires, it never runs continuously 24/7, and my understanding is that it cannot do so.

The gas is just sitting there under Bass Straight, and Longford jut intermittently crank up their gas processing plant into action as required.
Things like catalytic converters and water removal require certain definite temperatures, flows, and pressures to work. its like the compressor in your refrigerator, it is either running or completely off.

The pipeline to Melbourne carries three days minimum of full load gas supply during winter peak, and much longer than that during warmer months, even with full flat out industrial load.

When Longford blew up, it was totally out of the picture for several weeks.
An immediate total ban on gas use by industry, businesses, and home owners allowed the hospitals and other critical users (of which there were not that many) to keep going for several weeks on just residual line pressure in the 400 Km of high pressure gas pipeline.

There were gas inspectors madly rushing around everywhere checking house to house and business to business that all consumer gas cocks were turned off, and in some cases physically removing gas meters and issuing fines. Those guys must have made a fortune in overtime !!
It was quite a memorable event.
If the whole system HAD shut down, it would have taken a very long time to safely start it all back up, mainly because of water and air ingress into gas mains if the line pressure in the whole distribution system had actually dropped to zero.
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Re: LNG or Electricity? Find out!

Postby Smurf1976 » Sat Apr 19, 2014 11:12 pm

I can only assume that the gas industry would have done a probability analysis which concluded the LNG plant (or some other means) was necessary.

Back in the old (pre National Electricity Market) days the electricity industry was very much driven this way.

Eg in Tasmania it was done on the basis of 1000 data runs with simulated weather (rainfall being a hydro system) which then gives production limits (energy as distinct from peak power) for the individual power stations and the system as a whole.

Normal operation will shift baseload production around to where the water is. Eg the schemes with smaller storages run very hard, often at full load 24/7, during wet weather but are shifted to peaking operation during dry conditions. Vice versa for the schemes with large storages - they're pretty much shut down during wet weather and run hard when it's dry.

But it's not impossible for the system to fail to meet load in full, even if the overall storage situation is reasonably good. Eg if it's June (high load on the system) and it doesn't rain (extreme but it's happened before) well then you can't carry the whole load just drawing on the main storages especially if something breaks down. So it's certainly possible to end up draining the smaller dams, thus putting their associated power stations out of action, under various scenarios. And if you drain enough of them well then the lights really will go out.

The risk of such problems was always worked out using simulation runs (computer calculations). You do 1000 runs starting with current storage levels and factoring in any current breakdowns and planned maintenance work and see how many failures you get. The internal standard in the pre-NEM days was 2% - if more than 20 out of 1000 runs resulted in blackouts then that was deemed an unacceptable risk requiring that something be done to bring the risk back down to an acceptable level.

Typically, the preferred action (since it was the cheapest) is to defer non-essential maintenance work. Then there are options like short term overload production which is very doable in parts of the system but at the cost of lost efficiency (and the higher the overload, the greater the efficiency loss - there's a point where it ceases to be sensible to do). Then there's things like switching off internal pumping loads if this can be done without losing the water from the system (just store at the current location and pump it later). If all that wasn't enough then there was always thermal generation as a last resort (due to cost).

So I'd assume that the gas industry would have done a similar exercise at some point and concluded that Melbourne needed an LNG plant and storage in order to maintain system reliability under various plausible scenarios. For example, what happens if one of the three production lines at Longford suffers a major problem and is out of service right through winter? Or if the entire Longford plant goes down for 24 hours (for whatever reason) and it's extremely cold that whole week? Or there's an urgent need to take a major pipeline out of service? Or any other scenario that just happens to result in a reduction in gas supply into the system at a time of high demand?

It was the old Gas and Fuel (government) which built it - it's been there quite a while now. I can only assume they did a risk analysis and concluded that it was necessary since it wouldn't have been cheap to build that's for sure.
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