This little piece is addressed to people who won’t see it. I speak of those who are paid to write about energy, but don’t know what it is. It was prompted by a couple of pieces in Norfolk’s local newspaper, the Eastern Daily Press, or rather its web presence. The first was this from December last year, in which the following is said:

More than 10pc of the UK’s domestic energy will be supplied from a wind farm set to be built off the north Norfolk coast. Vattenfall, the firm behind the Norfolk Offshore Wind Zone, has increased its capacity to 4.2GW and will now power 700,000 more homes compared to its original design. This will see the turbines supply electricity to 4.6m houses across the country.

Wrongness abounds here. This can all be ascribed to being imprecise with language; there is no intent to deceive. Nevertheless it may give rise to a false understanding of the facts by the audience. The second was more recent. It cuts and pastes (and links back to) the first, and says:

Once completed, the 4.2GW wind zone will supply more than 10pc of the UK’s domestic energy.

As an aside, the article is actually about the cabling. No it is not manufactured in the UK. In fact:

Vattenfall, the company behind the Norfolk Offshore Wind Zone, has signed an agreement with Greek firm Hellenic Cables to provide the inter array cables for the project. Hellenic Cables will supply around 528 miles (850km) of aluminium cables – as far as from Great Yarmouth to Aberdeen – to connect the wind turbines with the offshore substation, helping to power the wind zone.

Let us begin with the obvious point. The UK’s energy consumption does not solely consist of electricity. If it did, then the EDP would not be so obviously wrong – it would be on the right planet at least. Last year, according to the March 2023 update of Energy Trends, the (provisional) energy consumption of the UK was:

170.9 million tonnes of oil equivalent (mtoe).

I prefer to use joules. Naturally this is “wrong” in the sense that not all the oil and gas will be used for its energy content. However, it has that potential at least. According to the internet, 1 toe = 41,868,000,000 J, so the number is:

7.16×10¹⁸ J

Or if you prefer, 7.16 EJ. It does not include energy sent to “marine bunkers,” which is fuel for ships. It does include a small amount of electricity exports.

The pie chart shows what that energy consists of. Here the electricity exports are missing, so the total is slightly higher than 7.16 EJ. The lion’s share is fossil fuel; note the small share of primary electricity from our “zero carbon” friends. Data from Energy Trends Table 1.3, except there they give the numbers in mtoe, as mentioned.

Of course, the end user does not obtain all that energy goodness. Some of it is thrown away by converting the energy from one form to another (e.g. by generating electricity). The final energy delivered was 127.364 mtoe, or in joules…

5.33 EJ

This does not include non-energy uses of energy. (Huh? Well, it means things like turning fossil fuel into plastic.) Of this, 0.98 EJ was the final energy consumed as electricity. This is smaller than the quantity of electricity generated. It does not include electricity used by power generators or losses. It means that electricity is 18.5% of final energy consumed. [It’s 273 TWh, if you prefer it that way. Energy Trends does.]

How much of this is domestic electricity? The next pie shows the breakdown of the UK’s final electricity consumption, provisional, for 2022. Data this time from Energy Trends Table 5.2; I have not bothered to convert into joules. The pie shows that domestic electricity is about 37% of all electricity. That means it’s roughly 7% of all energy (0.37 * 0.185 as a proportion).

So, making the assumption that our correspondent meant domestic electricity when he spoke of domestic energy, to reach “more than 10pc” of that number, the Norfolk Offshore Wind Zone (NOWZ) needs to generate roughly 100 TWh * 0.1 ~ 10 TWh. Once all 4.2 GW is operational, NOWZ will cover an average of 10% of domestic electricity if its capacity factor exceeds about 27%. [4.2 GW * 8766 hours in a year * 0.27 = 9.94 TWh.] This is obviously achievable for an offshore wind “zone”, or maybe a more appropriate term would be an offshore wind “defeatherisation.” Of course, we know that the actual delivered power is likely to swing from 0.42 GW to 3.8 GW, but that’s another story.

If we wanted to build a wind farm to actually produce 10% of UK domestic energy, not just electricity, how big would it have to be? Well, about 4 times larger than if you wanted to just cover 10% of domestic leccy. [The proportion of domestic energy that is electricity is usually given as 0.2, e.g. by Ofgem, but it has been creeping up over the past 25 years on my look at the numbers and is now closer to 0.25. Of course, it is eventually intended to reach 1. Given that increase in leccy – from 20% of all domestic energy to 25% – in 25 years, it might take a while for that to happen.] You would therefore need a wind farm of about 16.8 GW.

Incidentally, the first part of NOWZ, Boreas, has been awarded a CfD at a ludicrous price:

Government has awarded Vattenfall a CfD at £37.35/MWh (2012 prices) for the 1.4GW Norfolk Boreas Offshore Wind Farm

According to power-technology.com, it will cover 1,300 km² when completed:

The Norfolk offshore wind zone will cover an area of 1,307km² in the southern North Sea.

An elementary sum would show that if NOWZ produces <1% of the UK’s energy, then to produce 100% from this source, we will need 130,000 km² of offshore wind farms.

The NOWZ belongs to Vattenfall (Swedish). As noted, the cabling is Greek. The turbines are Spanish-German. A Dutch company did the surveys. The HVDC converter stations are from a Norwegian-German consortium. Some British companies helpfully arranged pieces of paper. (I don’t know where the turbines will be made.)

There is much more to be said on this topic, but this post is already long enough.

Please alert me if I have missed a decimal point somewhere…

Data tables and the Energy Trends report available via this link.

Featured image: “A power engineer juggling pie charts in front of an offshore wind farm” – Dall.E.