Renewables, Drax and Myth Busting No 1

It appears Drax wish to bust some myths about renewable energy (see HERE) They are tweeting about them one by one. So I thought I'd have a go too and dig under the headlines at least for the first so-called "myth" they wish to bust: Here it is.

The First "Myth" they want to bust is...

"Myth 1 — Renewables are unpredictable"

There’s more to renewables than solar panels and wind turbines. Tidal power is much more predictable than either, and geothermal power — using heat from the Earth’s core to generate electricity — is almost completely reliable.
As for predictability, sustainable biomass uses compressed wood pellets to generate electricity whenever it is needed. It’s completely predictable. You can use it to produce electricity on demand, to control frequency in a split-second or for baseload power. It’s as reliable as coal or gas, but with a fraction of the carbon emissions.

Yes it is true! There is more to renewables than wind and solar (both of which are hopelessly intermittent)

It is also true tidal power is more predictable and geothermal is reliable too! And that Biomass can provide baseload.  But we still have some problems here. So let us look at these predictable and reliable examples of RE goodness.


Sadly in the UK we have barely any tidal power at all. That is because in most places tidal power is simply unfeasible. Consequently little is planned and even this is horrendously expensive and arguably technically dubious.

To cap it all the maximum that could be generated by tidal is 12% of demand. But anyone who believes we could get anywhere near 12% is really living in the world of Tooth Fairies and Easter Bunnies. (h/t to  Dr Jim Hansen HERE)

But lets look at what Tidal there is and what is planned/proposed


In Scotland there is a tidal stream scheme (MayGen - HERE). Currently it has a maximum capacity of 6MW ( similar output to that from a single locomotive engine) But the dream is to expand this to is a maximum capacity of 398MW. Either way its capacity factor will be around 20%. (So averaged output power will be about 1.2MW/80MW)

There is a big incentive to build the dream. Tidal Stream generation is the only type of generation that makes offshore wind look cheap.

MayGen will be paid no less than 5 ROCs subsidy (or £225) per MWh. This means that typically they will be paid £260 per MWh whereas normal generators (gas/nuclear) get paid about £43 per MWh.

To be fair MayGen is verging on experimental. It is the very tip of the state of the art.

We know Tidal Stream power may be predictable. But is it viable? Or affordable? I'll leave you to decide.

But one thing is certain: It ain't going to be the golden bullet to save intermittent RE anytime soon.

Swansea bay Tidal Lagoon

Then there is the proposed Swansea Tidal lagoon. This will have a (very, very) brief maximum output of 320MW. But its capacity factor will be less than 20%. Averaged over a year its output power will equate to approximately 60MW. The estimated cost of building this thing is £1.3 Billion (Ouch!).

That is about the same cost as building a 1.2GW (i.e. 20x the output) CCGT gas plant.

Compared to the Scottish tidal stream scheme though, the Swansea lagoon will be cheap with only 1.8 ROCs subsidy per MWh. It will be only 3 times the cost of normal generators.

Again. Predictable it may be. Affordable? Viable? Or even environmentally benign? You decide.

(Euan Mearns did a wonderfully complete analysis of the Swansea Tidal Lagoon  HERE.)


Just like Tidal power, in the UK we have little to no geothermal power generation.

In fact the UK is geologically a bad place for geothermal energy. True - we can tap shallow underground heat for heat pumps and space heating but electricity generation? Really?

As far as I can tell the prospect for any significant geothermal power generation in the UK is Nil.

End of.


Then we come to the meat and potatoes of the Drax myth busting. Their glorious Biomass.

Happily I have to say that just about everything they say is true. I (sort of) believe them in their sustainablity claims as well. But there are problems.

But first - a pedantic point:
.....It’s as reliable as coal or gas, but with a fraction of the carbon emissions.

DON'T BE SILLY! Of course burning biomass emits Carbon Dioxide and MWh for MWh virtually the same as coal!! The fact that you offset that by replanting does not mean that magically no Carbon Dioxide or pollutants get emitted when you burn wood pellets! You could equally offset coal by planting trees - you just can't use the same space.

But back to what I see as a major problem with biomass.

Bear in mind to simply maintain the current Drax 2GW generation in a sustainable manner will require an immense 12000 sq Km of forest. (Wikipedia HERE)

How much more biomass can we (morally or practically) import from abroad?

I don't know.

But I would suspect that we are already at the limits of sustainably maintaining a supply of wood to the existing Drax wood burning plant.

So there you go. If you want non-intermittent RE in the UK, in reality you've got Biomass.

But how much more Biomass can we build before we start seriously damaging the environment?

Anyone who knows the answer to that one please tell me.

I'd love to know.