OT - Gridwatch and renewables snark again

[tabbypurr]

Flame triodes are that plus a bit, FFD only depends on rectification.

NT

[Martin Brown]

It probably is just about sustainable if managed properly but the devil is in the detail and it is always more profitable to take the money and run - leaving someone else to clear up the mess afterwards.

Ironically shipping bulky not especially energy dense material half way round the planet to supply it with fuel.

Fusion in the sun is pretty good though at least for modest geological timescales - ultimately it will go pear shaped in another 5bn years or so. Ironically as the sun cools and expands into a red giant the Earth will get hotter and ultimately find itself inside the photosphere.

In practice we probably have at most another billion years or so before the Earth becomes too hot for life. That is still more than three orders of magnitude longer than modern humans has been on the planet.

[newshound]

Don't they say that half of the UK agriculture industry is unprofitable without the subsidies? It's only 0.7% of the economy now, so not a big impact on GDP, and it would free up an awful lot of land. Although we tend to think of the hill farms as being not very productive, quite a lot of that area was forrested five thousand years ago.

[tabbypurr]

Farming is primarily done here for military security.

NT

[newshound]

The CEGB put a pile of research money into this in the late 60's or very early 70's. IIRC one of the problems was corrosion. You need big magnets too, of course. At the back end you still have a lot of energy in your exhaust gas after it has stopped being very conductive so you have to back it up with something like the back end of a combined cycle gas turbine. I suspect it was abandoned because CCGT made more sense. In those days you could not burn gas, of course, also oil got expensive after 1973. One of the guys in charge moved over to fast reactors, which is where I came across him.

The other technology the CEGB looked at around then was pressurised fluid bed using pulverised coal as fuel. The higher energy density lets you make the boilers smaller and therefore cheaper. The downsides were corrosion and erosion. There was a prototype at Grimethorpe, but they had more success with the colliery band.

[Tim Lamb]

Likely. It didn't seem hugely practical for pulverised coal firing.

[Dave Liquorice]

ICBA to dig up those figures but as we have them lets do some maths just to see.

2 trees per minute = 2 * 60 * 24 = 2880 trees/day = 1,051,200 trees/year. So that's a square of 1025 trees/side at say a 5 m grid = 26 sq km felled per year.

No to be sustainable you have to have a rolling supply of mature trees. These are grown over the period it takes to go from seed to mature, say 50 years. Simplistically the CO2 released by burning 1 years worth of trees is asorbed by the next 49 years worth trees (all

52 million of them) that you are growing to maintain the supply and the felled areas being replanted to be burnt in 50 years time. 4.4 tonnes per minute is 6336 tonnes per day. Over 52 million trees that's an average of 120g per tree per day.

With 50 years to grow a tree forest area required 26 * 50 = 1314 sq km.

So 7884 sq km for all 6 Drax units.

Canada, where most of Drax's wood chip orginates, has a forest area of 4,916,438 sq km according to Wonkypedia. So just 0.16% of it could, theorectically, supply all six Drax units...

Wether shipping 13.8 million tonnes of woodchip per year from Canada to Drax is a different matter.

Scotland has just over half of of the forested area of England, Scotland and Wales at 13,107 sq km. So Scotland could supply all six Drax units with a 50 year felling cycle (which is probably longer than the current timber cropping cycle) from something just over half of it's forested area. Remember that only 156 sq km would need to be felled each year to supply six Drax units or just 1.2% of the total forested area.

[AnthonyL]

I fairly regularly pass Radcliffe-on-Soar (2000Mw). Running full blast on Monday so meeting about 5% of demand. Lots of coal and for reasons I don't know lots of trucks near the coal pile. Usual delivery is/was by rail.

[Martin Brown]

Although in the UK the remaining forests final big hit was when glass makers and iron foundries started wanting charcoal on an industrial scale starting as early as the 1500's. This was back when good timber especially oak was wanted for building warships to defend the realm.

We were dependent on timber imports from about 1700 onwards. See:

Coal came at about the right time to save some of our forests although they did had to impose draconian measures on some glassmakers.

Kenya is presently going through the same destroy all remaining forests for charcoal production today as we did in the middle ages. eg.

[Chris Hogg]

I don't have the data on mass growth-rate of saplings, appropriate sapling spacing, best type of tree to plant, etc, but it seems to me we'd run out of space pretty quickly, upland farms notwithstanding. I suppose you might be a little better off with a sort of pollarding process, where you leave the extensive roots in the ground to feed the growing shoots and get things moving quickly, but you'd still need leaves to manufacture the sugars that then become the cellulose/wood.

[Chris J Dixon]

Indeed. I can see the plume from my bedroom window, and it does seem to be working more often than one might expect.

Perhaps the trucks were moving material associated with the Flue Gas Desulphurisation plant.

Chris

[The Natural Philosopher]

You dont need to do all this shit.

Output from biomass is about 0.2W/sq meter - that's fast growing wetlands - alders and poplars.

Drax is cracking out 3GW so that 15 square gigameters or 15,000 square kilometers.

A patch of land 122km on each side, Or 80 miles square give or take,

So Drax needs a county sized patch of wetlands. Under continuous cultivation.

[harry]

A lot of wood pellets are made from unusable timber. Offcuts, brash etc.

[David]

Perhaps unscheduled high demand is outstripping the available rail transport?

Or are the locals nicking some for their coal fires?

Cheers

Dave R

[Chris Hogg]

That's OK once equilibrium has established, but to avoid an initial pulse of CO2 you'd need to absorb the first year's CO2 within the first year, not over 50 years. Or put it another way, to avoid a pulse you'd need to plant your 52 million trees at the start, and then plant your replacement trees as each year's fuel is felled, presumably from a mature stand somewhere else.

Perhaps you could argue that the existing stock is adequate to cover that initial surge.

[Vir Campestris]

Let's see, two trees a minute and they take ~50 years to grow.

50 * 365 * 24 * 60 / 2 is ... 13 million trees.

Say each tree needs 10sqm to grow and that's 13,000 Ha. There are apparently 3 million Ha of forest in the UK.

Not impossible, but a lot bigger than a nuke.

Andy

[tabbypurr]

that's one way to confirm it's correct

NT

[AnthonyL]

That's around the other side. These were on the South side on the A453 side of the coal pile. I'd wondered if they were being used to shift coal around from one part of the heap to another as they often seem to be doing, though I'd expect them to use bulldozers for that. I'd guess about 6 or 7 tipper trucks in a line.

[AnthonyL]

Useless stuff for home fires and security is well over the top there ever since the demonstrations a few years back.

[AnthonyL]

I saw a TV program which followed the route of the pine from its origin. A lot of damage is being done to natural habitats that are not supposed to be used (Drax rep said it wasn't their concern, but their suppliers) and there's a lot of subsidy too.

Green my *rse