Questions asked by MBA Strategic Carbon Management Students 2013

 

The following are questions asked by students on this year’s cohort, and so that all may benefit I am including both the questions and answers so that all may benefit.    In some cases, if I feel there is something more to add,  I may ask supplementary a question myself to give more information.

 

A question asked by Alex on 7^th March

 

1.      A Couple of questions:

a)      Could you please refer me to data on the real carbon cost of nuclear fuel, taking into account the mining, refining, production etc. before the cans get delivered to the reactor. Whilst the actual operation is low-carbon, there must be set-up (and decomm) cost.

b)      You mentioned the carbon / KWh for different kinds of elec generation systems. Unfortunately I couldn't write them down quickly enough. Can this be broken down by different type of reactor?

   Answer: 

 

The overall actual carbon factor depends on several factors –

 

1)      Mining,

2)      Transport to power station

3)      Actual generation – which depends on calorific value of fuel, and the actual efficiency of the power plant (the latter probably being most significant part over all.

4)      Transmission losses to end consumer which vary from around 6.5% to over 25% depending on country

 

Overall though the carbon emission factor for coal is around 900 – 1050 g per kWh – note some references declare only the carbon factor within the power plant itself and then figure comes out rather lower – my figures include all aspects

 

For oil – based on similar assumption it is rather lower at around  800 – 850g / kWh

 

For gas it depends on actual technology used – if a direct steam generation is used – i.e. replacing coal or oil – then the factor is around 600 g, while with Combined Cycle Gas Turbines the figures is around 390 – 400g  .  Most gas stations these days are of the CCGT type, but there are some open circuit gas turbines which have a high factor (up to 700g) because of the relatively low efficiency of such plant -  they are used because they are rapid responders in sudden changes in demand so are used for peak lopping and not for base load generation

 

For nuclear the full fuel cycle including mining and fuel fabrication comes in around 5 – 20g – lower for MAGNOX and CANDU because less enrichment but more for PWR because of enrichment.   The actual values for a particular reactor will vary depending on where the fuel enrichment and fabrication takes place – thus a PWR fuel element in France will have a lower value than in the UK as the overall carbon factor taking account of the generation mix in France is around 70 – 80 g / kWh where as it is 530g in UK, around 550g in Germany, 900g in Poland, and 2g in Norway.  So depending on where the fuel is fabricated the actual figure can vary quite a bit – that is why a bracketing of values is often given.

 

With regard to construction embedded carbon – there are once again assumptions which need to be made but per kWh over lifetime – the embedded carbon for both nuclear and wind turn out to be in the range 15 – 30g for oil and coal – comparable amounts although probably a little higher for coal in view of the coal handling plant construction.  For gas the figure is likely to less at around 10g.  For solar,  it is highly dependent on Country of manufacture – would be very low if made in Norway,   low in Switzerland or France,   moderate in Spain – moderately high in UK and Germany,  and very high indeed in Poland and China.

 

The above raises an interesting dilemma in that labour costs are low in China, but carbon emissions are high, but on the other hand labour costs are high in Norway but carbon costs are low.   Do we probably value carbon to take account of these differences?