(no subject)

[fivemack]

A Greenpeace article

http://www.greenpeace.org.uk/blog/climate/greenpeace-shuts-down-coal-fired-power-station-20071008

includes the line 'And it will only be 45 per cent efficient, in an age when power stations can reach 95 per cent efficiency'.

This is a coal-fired power station, so 45% efficiency in converting thermal to electrical energy is I think extremely good.

95% thermal efficiency implies, by the Carnot equation, that the heater is twenty times hotter in Kelvin than the heatsink and that there are no other thermal losses in the system. With a heatsink laid on an infinite icefield at zero centigrade, the heater has only to be hot enough to boil tungsten. I was unaware that gas-cored fission reactors were either in production, or this enthusiastically endorsed by Greenpeace.

Comments

[cultureofdoubt.livejournal.com]

Weird. I struggle to think of any measurement of efficiency that would be 95%.

[randwolf.livejournal.com]

They are arguing for what they call combined heat and power; re-using the waste heat of power stations. This is indeed very efficient, though perhaps not the best solution. Their objections to coal-fired plants are valid. And, you know, they're doing something. Perhaps not the best thing. But the people who could do the best thing aren't doing any damn thing. So why the objection?

I would ask for danger money for working on a coal plant these days

[jiggery-pokery.livejournal.com]

This is a coal-fired power station, so 45% efficiency in converting thermal to electrical energy is I think extremely good.

Damn straight! I think new closed-cycle gas turbine / steam turbine units get up to about 56% efficiency these days, though, but it's more about accountancy than thermodynamics at this level - what value you place on work done by the recovered steam, for instance, especially if you're calling it Combined Heat and Power and getting it to heat other stuff off-site as well.

I fear Greenpeace may not necessarily be using the word "efficiency" the way you are and that this 95% efficient station is measured in some other context apart from thermal efficiency. Not sure what this 95% efficient station would be, how large it is and what sort of load factor it has. That said, I half-recall hearing that pumped storage hydro stations are remarkably efficient, reclaiming something like 70% of the energy required to pump the water uphill. Not bad for fifty-plus-year-old technology!

[tau-iota-mu-c.livejournal.com]

A German bunch want to generate a gigawatt (4% of NSW needs) using wind in Broken Hill, but the NSW government don't want to commit to buying it, saying there's not enough wind here despite the investors saying "um, yes, there is. Look, here's our money".

But the NSW government are going ahead with plans to build a new coal fired power station that will still have to be operating in 50 years, despite er, 50 years from now being not a very good time to be stuck with coal fired power.

I'm with Greenpeace on this, as I was back when Real Action shut down Loy Yang a couple of months ago.

[rwl.livejournal.com]

45% fuel-to-electricity efficiency for a coal-fueled power is very good. It has to be some kind of advanced technology like integrated gasification combined cycle to do that. The waste heat can be used for other purposes, true, but most of them would require some significant infrastructure improvements. One possible use that would not require a lot of capital investment would be heating greenhouses in the cold winter months. That's already being done with waste heat elsewhere in the world.

[(Anonymous)]

Ah, Greenpeace just love invading power stations. They did something similar to Didcot A about 10 months ago. I don't think that they realise that the demand for power needs to be met, so National Grid will just use the Balancing Mechanism to call plant on to replace the generation that has been lost. It's entirely possible that by taking out coal plant at peak time, you force oil stations (such as Fawley and Littlebrook) on. Which doesn't help the environment one bit.

The major problem with the massive push for renewables that is being advocated is that there simply isn't the transmission infrastructure present in the UK to connect all of the wind generation that wants to come on - at present we can only shift about 2.2GW of power from Scotland (where there's lots of wind, and lots of wind farms that have applied for connection) to England (where there's lots of demand). It doesn't help that when SSE and SP applied to build reinforcement power lines from Beauly to Denny, the application got stuck in the quagmire that is a public inquiry.