Too Little Too Late

The government has now pushed back its timescale for nuclear ‘new build’ by five years. So already after the energy review in 2006 the nuclear programme is now at least five years behind schedule. In terms of cutting our CO2 emissions, it is extremely important how quickly we can replace high CO2 forms of electricity sources with low CO2 sources – this is what I am going to try to explain in this post.

This is a subject that I touched on in my post Nuclear CO2 Emissions. This is not going to be a quantitive analysis – I am just trying to get the basic concept across. I have attached by very simple spreadsheet if you want to have a further look yourself.

First of all a couple of points:

The levelised CO2 emissions are taken from one paper² since it is important to use the same methodology for calculating CO2 emissions from different sources.
The replacement of power sources – some plants will last longer is already accounted for in the levelised CO2 emission figures, so there is no need to do it here.
I have then levelised the CO2 emissions from the current high CO2 sources over a period of 50 years. The timescale (50 years) is in a way quite arbitrary but takes us past the 2050 targets. I have taken the current CO2 intensity as 500g/KWh.

delay1 — CO2 emissions from current electricity supply followed by nuclear (blue) and the average over 50 year period (red)

Anyway, down to business. Let us consider a nuclear plant that will be ready in 15 years. For those 15 years we are using the current mixture of gas, coal, wind and nuclear to produce electricity which emits about 500g/kWh. After that nuclear will replace it at 65g/KWh. Averaging over a 50 year period, this gives an average of just over 195g/kWh.

Now let us consider ramping up wind production over the same period.

delay2 — CO2 emissions from current electricity supply followed by nuclear (blue) and the average over 50 year period (red)

This gives us an average CO2 emission over 50 years of just over 97gCO2/kWh – less than half that of nuclear. However, wind can be implemented faster than this. If we assume a more reasonable figure of 6 years to build enough wind capacity, then it has CO2 emissions four times less than a nuclear plant built in 15 years time.

OK, on the two graphs I am not comparing ‘like with like’ but wind is not like nuclear. Wind capacity is actually happening – adding 500Mw per year³ while nuclear is still a pipe dream with lots of problems to overcome (subject of a future post).

When people talk about other technologies (subcritical reactors, thorium reactors etc) which are a long way in the future if they are developed before this factor becomes even more important.

It is not just by how much you cut CO2 emissions, but how soon can you do it.

Spreadsheet (xls)