What is the efficiency of a power station?

[Bluemoon]

The wholesale price of electricity in the UK at the moment is about 5p/kWh according to:-

www.businesselectricityprices.org.uk/cost-per-kwh

(RE:- " Over the past few years these have stabilised to between 4p and 5p per kWh. ")

 

and the wholesale price of Kerosene (@ $1.62 to the £) is about £458/mt (45.8p/kg) according to:-

www.thisdaylive.com/articles/falling-oil-price-as-window-for-subsidy-removal/192441

(RE:- " For Kerosene, the actual cost in a foreign refinery recently was $743 per metric tonne ").

{ I'm using 46.2MJ/kg as the heat of combustion for Kerosene according to:-

http://en.wikipedia.org/wiki/Kerosene

and 1kWh=3.6MJ }

which leads to 3.6p/kWh ( 45.8 / 46.2 ) * 3.6 )

 

 

As such, these figures indicate that power stations in the UK are operating at implausibly high energy conversion efficiencies:-

3.6p / 5p * 100 = 72%

 

I don't doubt at all that I've misunderstood something somewhere, but what?

[Endy0816]

How is the chemical energy of the kerosine being converted into electrical power?

Edited October 30, 2014 by Endy0816

[Bluemoon]

I suppose that it's burnt in a furnace.

[Strange]

What proportion of UK power stations run on kerosene?

[Acme]

I suppose that it's burnt in a furnace.

I think you should find out exactly because if the kerosene is being used as jet fuel in a turbine [jet] engine as opposed to a furnace fired steam boiler driving a steam turbine then the station (if using a jet engine) might be more efficient. I say this because we have a natural gas power plant in my village in which the gas fuels a turbine engine and then the cooling water drives a secondary steam turbine [on the same shaft] before the water goes to the cooling stations. This two stage generator gives added efficiency as it was explained to me when I toured the plant when it opened.

 

Edit: I had the term incorrect. It's not two-stage, rather called combined cycle. Here's a Wiki: >>Combined cycle generators

Edited October 31, 2014 by Acme

[swansont]

Do power stations sell all of their electricity at wholesale rates?

 

"the actual cost in a foreign refinery recently was $743 per metric tonne" - that's not a British cost. Perhaps the British cost is lower? Who knows if the foreign refinery had to import the oil, which would cost a lot more than if it were locally produced.

[Bluemoon]

Acme, your wiki link is intersesting, 60% is nearly plausible, but ...

Strange >What proportion of UK power stations run on kerosene?
Good point, I've only been able to find one:- Peterhead Power Station in Scotland
which, presumably, must be because Kerosene/heating oil really are as expensive as I thought
making my query mute.

swansont >Do power stations sell all of their electricity at wholesale rates?
I think so, because sometime last year SSE were told by the regulator that they had to stop selling theirs directly to their
customers and instead sell it wholesale to the 'pool' and then buy/(bid for) it back as a 'pool' customer;
and only then be able to sell it on to their customers.
Otherwise if they wanted to they would even be able to profitably sell the oil-made stuff, 5p +60% = 8.4p, to the likes of me for the 12p that they do;
(but they add some extras on, one of which is profit, that brings the price up to 16.5p +vat).

[Acme]

Acme, your wiki link [oncombined cycle generating plants] is intersesting, 60% is nearly plausible, but ...

 

Strange >What proportion of UK power stations run on kerosene?

Good point, I've only been able to find one:- Peterhead Power Station in Scotland...

I checked on the Peterhead plant and while it has gone through a variety of system configurations it appears it is now only operating as a gas fueled combined cycle station with an efficiency of 57%. (So it's not using kerosene.) They have a limit on what they can produce because of the transmission system.

 

Peterhead Power Station

Combined cycle gas turbines

 

In 2000 the station completed a major repowering project to increase the efficiency and capacity of the station. Three gas turbines were utilized in an innovative manner to provide steam to one of the original steam turbines. These changes allowed for 1150 MWe of output to be delivered at 57% thermal efficiency compared with the original plants 37%.

...

Specification

 

The three 277 MWe V94.3A (now called SGT5-4000F) Siemens gas turbines provide a CCGT-type system of power generation, with three Doosan Babcock heat recovery steam generators providing steam to one (older) steam turbine. ...

Edited November 4, 2014 by Acme

[John Cuthber]

Does the wholesale cost of kerosine quoted include tax/ duty?

If so do the power stations pay that same level of tax?

 

 

Also, if this is true

http://www.bbc.co.uk/news/business-29903666

then crude oil is currently about $82 per barrel

There are about 7 barrels to the tonne

so crude oil costs about $570 per tonne.

The heat of combustion is probably not that dissimilar

What oil fired power stations burn is more like crude oil than like kerosene.

 

So that's a factor of roughly $570/$743

That brings it down to about 55%.

Still rather high.