These foreparents did have some help in boosting their 1 kW Taking just Renaissance England England, around 5 million people had the power of more than a million oxen and horses to draw on, so this added perhaps as much as 2KwH per day per person to their power They had 125,000 sq Kilometres to divide up between no more one tenth of today's population, so they had lots of woodland - maybe 50,000 sq. kilometres, growing wood at the rate of 0.2 Watts per sq metre. Work it out 50,000 x 10⁶ x 0.2 = 10¹⁰ watts = 10 million Kilowatts, 2 kW per person, or 48kWh per day per person - maybe they utilised a quarter of this for keeping warm, cooking and smelting metals, say 12 kWh per day per person. No wonder we are so fond of open fires and campfires! Indirectly, the power of the sun turned their wind and waterwheels, perhaps 20,000 of them generating 12kW each, or 50W per person, a handy 0.5 Kwh per person per day. Also courtesy of the sun, they grew food to feed themselves and their beasts, used for meat and milk and wool as well as for power, maybe producing another 10 KwH per person per day so you can see that they had already, by Shakespeare's time managed to multiply their personal power output by a factor of 20 or 30 by what we would call sustainable methods, producing or at least utilising some 25 KwH per person per day. Nature provided everyone with 24 slaves. This estimate is supported by similar levels for today's Algeria, Egypt, Indonesia and other so-called developing economies.

Back to the Land - then?

Notice, however, that were the ten times more of us to attempt to go back to their way of working and living, that 25kWH per day would be reduced to 2.5 kWh per person per day. That's what a back to the land, self-sufficiency, backyard windmill and chickens life would mean. Maybe we should indeed move to France which supported a mediaeval population of some 20 millions on 4 times England's land area.

Back to today's Reality

How much power in total do we ACTUALLY use per head per day in early 21^st. Century Europe - well, it's hard to be exact, with all the global trade and moving around, but the figure seems to be about 125 kWh per day. 125 kWh per day!? I've seen an estimate as high as 140kWh per day. 5kW roaring away every hour of the day for every one of us – 12kW per household!!??

Yes, it is so, and, at 15p per kWh, we in Europe can (just about) afford it - £19 per day per head, maybe £50 per day per household, 8 hours work at the minimum wage - it is already becoming a strain, may we have some working tax-credit please?

Where does it come from - well, from coal, oil and gas of course - hence the global warming we're warned about. And, on that front let me say we ain't seen nothing yet - you can't multiply the concentration of a gas in the atmosphere by 50% without having effects. It's lucky for us that the concentration of carbon-dioxide in the used air in our lungs is already two orders of magnitude (about a hundred-fold) greater than the ambient levels, or we would all find our selves panting continuously even when resting. Fortunately, evolving life did have plenty of time to accustom ourselves to levels which are controversial but anciently probably 2-3 times the present level.

How do we use all this energy - I nip into Matlock to pick up our Clare from the community minibus.6 stop-and-start miles in the van, about a litre of fuel used, 10 kWhours, or about 10 x my daily output of power, or about 4 days worth of food-input! With the right equipment I probably could hand-haul the van to and from Matlock in four days. I could have walked it easily and gently in two hours, 200 watt-hours, Clare 100 watt-hours, say about a kWh of food intake, or about a tenth of the energy actually used, but about £20 worth of my time. The actual cost, doubling the taxed petrol cost was about £2,30. (note, a 30 miles per gallon vehicle travelling at 60 miles per hour is operating at about 90kW - NINETY KILOWATTS!! Don't forget to turn those energy-saving bulbs off.) Afterwards, a cup of tea - boil up a litre of water through 80 degrees, 80,000 calories, 80Kcals, about 100 watthours. Well, that's better, I could do that in an hour -but how, in practice - cuddling the kettle would only get the water to about 35⁰C. Later, a bath for Clare - 70 litres through 25 degrees, say 1.5kWh, or one and a half times my daily power output, but costing me only about 25 pence. A week of baths for Clare for less than the price of a pint. No wonder pubs are struggling - daily baths for the price of a round this Friday night.

These apparently trivial examples indicate how without thinking we use prodigious amounts of energy in our daily lives. Us Mitchells have had a very long generation time of about 35 years for three generations now, so my Granddad remembered life in the late 19^th. century - he a miner, Grandma a milkmaid in a Cumberland village. Sounds mediaeval, but it wasn't, their society, with its profligate inefficient use of coal - 5 tons or more per head per year works out at over 100kWh per head per day. The blink in time of 250 years since the Industrial revolution seems like forever to us, profligate use of energy goes back not just to our own upbringing, or to that of our parents but far, far beyond the tales of our grandparents.

Can this go on – of course not! - the reservoirs of fossil fuels are finite, only, typically about100 years of them are left at current usage rates. Global warming is just a little sibling of the family problem of use of finite and irreplaceable fossil fuels to provide energy – we'd better find other sources damn quick.

Finite Resources Last for Ever – the Chocolate bar Effect

 Actually, this isn't quite true. Logically, we CAN make a finite resource last for ever. Eg, consider this bar of basic best-value chocolate. Total Dave reserves one bar. Consideration-time's up! (Takes a bite) Current comfortable rate of consumption, half a bar a day. Dave's reserves will only last for two bites, then the end of life as I gnaw it. But wait, remedial action, I'll reduce my consumption by 50% per bite. Next bite is a quarter, next an eighth, next a sixteenth. It's the old frog-in-the-well commonplace that I'll never quite eat all of that chocolate. Even though there were only two bites of proven reserves, and half were consumed on the first day, the bar will last for ever. Coincidentally, we are thought to have used around a half of everything there is in the way of finite resources in aday of about 100 years (200, actually, but the equivalent of a much shorter period at late-20^th. Century rates), so as a rough stab, to eke out what remains for ever, we need to use up only half of what remains in the next hundred or so years.

Generally, the maths is beautifully simple - for 2 years of natural resources to last forever, we have to halve consumption each year, for reserves of 50 years to last for ever we have only to reduce consumption by a fiftieth or 2% per year, for a 100 year reserve to last forever we need to reduce consumption by a hundredth or 1% a year to make the resource last FOR EVER. Eventually, of course, our consumption will reach very low levels, and will be significantly lower after as little as ten or twenty years, but surely such a rate of retrenchment should be possible.

Not so easy, however. If we continue at present energy-use levels then even such an apparently small, say 1%, annual reduction in fossil use implies an enormous rate of increase in the provision of renewable energy, from the baseline near zero. Fossil fuel use would go down in the series 100,99,98,97,96,95, roughly, but renewables must go up in the series 0,1,2,3,4,5. The final 5 in that series is about where we are at in the UK with regard to electricity generation now, so to achieve just a 1% further reduction in fossil fuel use, we have to increase renewable energy from 5 to 6% - a 20% annual increase in capacity;  a tall order. You can see why it is that people quote 10 to 20 years as the minimum period it takes to get from pioneering to a substantial use of replacement technologies.

How might we do it? By renewable energy we tend to think of wind, of water of tide. However, to quote an article in the latest Scientific American:

Nathan Lewis of Caltec says that by the year 2050, civilisation must be able to generate more than 10 trillion watts of clean energy (what he means is 10 terawatts, or 10,000 Gigawatts, which he says is 3 times the average US energy demand of 3.2 Terawatts) (c.f. UK  400GWatts). Damning up every lake, stream and river on the planet, Lewis notes, would provide only five trillion watts, about half his target.

We can do that sort of calculation for the UK. Area of UK is 245,000 sq Kms, or 245 x 10⁹  sq metres, so if we could generate 2 W per sq metre of our land area from renewable sources of energy,, we could generate at a power of 500GW, approximately our current level. But is anything approaching 2 W per sq metre practicable?

Hydro: Mackay (in Sustainable Energy without the Hot Air) estimates the maximum theoretical hydro-power in lowland Britain as only 0.02 W per sq metre, (one hundredth of the target) and in Highland Britain as 0.24 W per sq metre – average about 0.15 W per sq metre and what proportion of this could we utilise in practice? - 20% ? , that gets us down to 0.03 Watts per sq. metre. Really, the contribution this can make is almost trivial, and just think of the expense,  fun though it may be to mess about with archimedean screws in Cromford Dam.

Wind.  Coincidentially (or is it?), the practically extractable wind energy per sq metre in the UK seems to average about 2 Watts per square metre ,so we could get to the target by covering the entire country with wind turbines at the optimum spacing. Actually, probably only about two-thirds of the country has wind-speeds high enough to justify installing turbines - but we can probably make up for that by employing off-shore area. If we wanted only to replace current electrical power generation as end-use then about an eighth of the country would do. If a quarter of current electricicity generation is the target, then about a thirtieth of our land area would suffice. This begins to sound more feasible, and is indeed about what the UK is currently aiming for, I think, and not far beyond what has already been installed in Denmark, Germany and Spain. That amounts to an average output of 4 Gw, which assuming a 20% load factor requires 20GW of rated capacity, only about 10,000 two-megawatt turbines, an investment of only around £20 billion in today's money. A wind-turbines-on-all-hills policy seems to be going ahead in Spain, where I suspect wild country is still viewed as wasteland, pending romantic poetical publications by their equivalents of Wordsworth, Coleridge and Ruskin. More of Wordsworth's view of the Lake District later.

The sun, the sun!  Even in this country, it's often burning down at the rate of  a full Kilowatt per square metre – from 10 sq metres, the footprint area of your house maybe, we can replace a 1 litre of petrol (10Kw) in an hour! Alas, however, there are clouds, low sun angle and  winter - cutting into the potential is the knife of the long nights! ( not quite original – a Band got there first). So the average power available in the UK is only 100 watts per square metre. Still, the human body, lazing in the sun all year would absorb about 2.4kWh per day;  2 Kilocalories if it could ALL be converted into food. So what about:

Sun via Biofuel Europe's best plants in bright sunlight and warmth can achieve about 2% efficiency in converting our 100W per square metre average sunlight into carbohydrate fuel; but the effect of cold and their tendency to have evolved to switch off in low-light conditions reduces this in practice to  somewhere in the region 0.2 to 0.5 W per sq metre. What proportion of our agricultural land could we spare? Well, as much as two thirds of our land area is classified as agricultural, but only about a quarter as arable. We still need to eat, and upland pastures would be very inefficient at producing biofuel, so I think 10% of our land area is the absolute maximum that could be utilised, so for the whole country that brings the Watts per metre down to  0.05 to 0.02 watts per metre - like hydro, symbolic rather than significant.

Was it Fred Hoyle who remarked that the sensitivity of photosynthesis to different light wavelengths suggested that life had evolved on a planet with a different solar spectrum to our sun and had arrived here from space via meteorites. Certainly, if we want to propagate our form of life in the Universe, something like sending out exploding warheads of poppy-seeds might well be the best way. Plants utilise the red and blue ends of the visible spectrum, but with a big hole in the middle - hence the green colour of leaves, reflecting or transmitting the unexploited wavelengths.

Are scientists even now working on the genetically modified leaf that would utilise the whole visible spectrum? Their super-efficient leaf would of course look BLACK. The era of black grass will then be upon us. Scientists would assure us that they'd built in safeguards such as susceptibility to a modified Roundup, in case the gene spread - but black plants being so much quicker-growing, they'd inexorably oust those old outmoded green species - England's Black and Pleasant Land would soon be upon us. A fantasy? Imagine my surprise to open the latest Scientific American at an article entitled Reinventing the Leaf. Researchers are devising artificial leaves that could .... convert sunlight and water into hydrogen fuel, which could be burned to power cars, create heat or generate electricity, ending dependence on fossil fuels. These particular leaves would, however, be entirely artificial and non-self-propagating! The aim is to get 10% efficiency in convertion of sunlight to fuel energy.

Sun via photovoltaics Currently, photovoltaics are very expensive financially and dangerously greedy for rare metals or expensive silicon products. Nevertheless, they are encouragingly efficient - about 16% is the current standard, 20% the current commercially available limit, 30% to 40% achievable but so far only in the lab. So that's 16 W per sq metre. If we put 20 sq. metres of photovoltaics on the roofs of 25 million buildings, that is 500 million sq metres, we'd be covering only a five-hundredth of the UK land area, so our watts per sq metre on average is down to (surprise, surprise) .. about 0.03 W per sq. metre - pretty trivial once more - and the capital cost of that, even at £100 per square metre (well below current costs) would be £50 billion.

Sun via Ground or Air-source Heatpumps We have an example in this building (the new, 2010, Derbyshire Eco-Centre), a plant able to produce some 20kW of underfloor heating for an imput of about 8 kW - an efficiency of 250% - about 4 x that obtainable from the most efficient gas-burning boiler or from combined-heat-and-power fossil-fuel generating stations. Mackay estimates an average energy flow into the ground, derived from solar-heating as 3 to 5 W per sq metre; much lower than the 100 watt average flux because of the low conductivity of soils and rocks. But at least we do have a figure in the right ball-park again! The trouble is, our dwellings, offices and factories are packed into rather less than 10% of our land-area, so the heat energy extractable in or adjacent to urban areas is going to be only 0.3 to 0.5 W per sq metre averaged over the whole country. Nevertheless, such a reservoir could supply enough heat for a high proportion of dwellings. Air-source heat-pumping doesn't apparently suffer from the limits of ground-source, but could surely have the effect of significantly cooling the local air on Winter's days. One might not want to live downwind of a major conurbation. With airflow halted by evening temperature invertion would the bowls in which Cromford and Wirksworth lie become intolerably frozen? Would the cold air of Wirksworth, perfumed by the tobacco of outside-the-pub smokers, pour over the lip of Cromford Hill, right by the Eco-Centre, to immerse the Cromfordites? I haven't done the maths on this yet...

Tide and Wave Power The potential around the UK is considerable, our islands are breakwaters upon which the Atlantic breaks and around which the tides are divided and accelerated. The energy extractable turns out, once again, to be in the 2 W per sq metre area - to match our demand, we have to find ways of harnessing wave and tide over areas of sea comparable to the area of the UK - once again a daunting task.

We could do some maths for Wirksworth

25 sq kilometres sounds about right for the area of the parish, 3 miles by 3. 200 people per sq.km, not far from the English average. There's no hydro, wave or tidal power (are there small tides on Carsington Reservoir, though - a project for Anthony Gell school?). Wind it must be.

25 x 1,000,000 sq metres x 2 watts per sq. metre - 50,000 kW which amounts to 10kW, or 240kWh per day, for each of your 5000 persons - sounds very useful: just the sort of level we need. - more than enough on average but a bit lacking to meet peak demand. But to generate that, with turbines that on average deliver no more than about 20% of their rated power, we would need to install wind turbines rated at 5 times the desired average power output: 250,000kW, or 250 Megawatts - 100 very large state-of-the-art 100 metre-tall turbines. 10 x10 at 500 metre intervals. Puts the Carsington or Matlock Moor proposals rather in the wind-shadow. Cost say £250 million or £50, 000 per person, say £125,000 per household. A lifetime's mortgage for everyone - that's the sort of cost we're looking at.

Tidal power is predicatble, but still very predictably variable over the year's lunar cycles. Wave and wind are very unpredictable. We'd need to store lots of energy from the good times to see us over those windless, and perhaps waveless winter cold-waves.

Storage by Slartibartfast

You will recall Douglas Adams' revelation in The Hitch-hiker's Guide to the Galaxy that the Norwegian Fjords were designed on the planet Magrathea by Slartibartfast, who won an award for the design. I asked him to redesign a fjord to store enough energy to keep the UK's lights on during a period when the wind doesn't blow. Let's assume we've built wind energy up to provide a quarter of our electricity generation capacity: 10 Gigawatts. To substitute this for a windless, hard-as-iron week in the deep midwinter we need to store 10 x 24 x 7 Gigawatthours - about 2000 GWh = 2 x 10⁹ kWh, which equals 6 x 10⁹ Megajoules, 6 x 10¹⁵ Joules.

Alas for Slartibartfast - his greatest work, the celebrated Sognefjord would have to be sacrificed to progress. The Sognefjord is a deep trough about 100Km long and typically 5 Km wide. We just need to dam up its mouth and a few side arms at Balestrand, Hoyanger and Ardal and pump-store energy therein as raised seawater - like the Dinorwic or Ben Cruachan schemes in the UK but on a rather larger scale. Dinorwic can store about 1.5 GWh - so we need about 1300 Dinorwics (this ties in nicely with Mackay's estimate of 400 Donorwics to store two days wind energy). Slartibartfast pointed out that as the fjord empties back down to sea level when generating, the dam will have to be twice the average water height during generation. I won't bore you further with the details, but, remembering that we need 1 Joule of energy to raise 1 kilogramme through 1 metre, Slartibartfast's design requires a dam height of 2000 metres, or about 6500 ft. A less obtrusive policy might have been to empty out the Fjord to that depth - but it's average depth is less than 1000metres. The high plateau above the Fjord's mountain walls lies at about 1500 metres above sea-level, so Slartibartfast reports that he can only guarantee about 4 or 5 days emergency supply with a 1500 metre-(5000ft-)high dam, higher than Ben Nevis. I haven't passed on Slartibartfasts's recommendation to the Norwegian Government yet, though there are already plans to lay a high-tension cable under the North Sea on the pretext of adding to the flexibility of the European Power Grid. If the Norwegians charged 5p a Kw Hour to give the energy back, they'd earn £75million every time the Fjord's store was discharged. Not to be sniffed at!

Energy density

Mechanical energy is, indeed, a very volume-consuming way of storing energy. The so-called energy density is very low - imagine trying to run a car on the energy from a descending pendulum weight. We could alternatively manage the job of storing a week's windpower energy using a fuel-oil tank of volume 2 x 10⁸ litres, i.e. 2 x 10⁵cu metres, or 200 metres by 100 metres by 10 metres tall - about the size of the Argos distribution centre you pass on the A38 near Burton on Trent. An oil-tanker-full in fact. Liquified natural gas would do just as well, but has only about two thirds the energy density of diesel oil. I suspect that some such project may well be in hand.

SAVING ENERGY

I know what any Transition Wirksworth, Transition Matlock and Sustainable Youlgreave persons here are going to say. Hold on, we all know that SAVING energy is a far better and cheaper way to go than trying to generate our present demand from renewable sources. Indeed the whole message of what I've said so far is to point out the appalling scale of any meaningful renewable energy project - disruption of great swathes of land and sea, tens of billions of pounds of investment But saving energy isn't easy either.

The rule of HALF seems to me to apply. We could all use cars that are twice as efficient (i.e smaller and less overpowered); we could all insulate our houses and change to more efficient condensing-boiler or heat-pump warming - and halve our household energy needs ; we could all recycle metals, paper, plastics, glass, which reduces the energy needed to make new finished materials, typically by - guess what - a half. Maybe we could fly half as often ( I can't help much here as I don't fly at all). But that only halves our energy consumption - and how are we going to force people to do that? Only about 10% of us (?)at the outside take any practical interest in these matters, and most of what we do is talk. Tony Blair for Instance: (to quote David MacKay again - he's a bit behind Douglas Adams, but Light-Years ahead of me)

Unless we act now, not some time distant but now, these consequences, disastrous as they are, will be irreversible. So there is nothing more serious, more urgent or more demanding of leadership. (October 2006)

Two months later, responding to the suggestion thatnhe should SHOW leadership by not flying to Barbados for holidays:

a bit impractical actually ... The Lord of the Manor declines to halt another Tragedy of the Commons .. take Commons either way.

Embedded Energy

A big logical, and therfore practical, problem is that if we spend less on driving or heating or flying, we'll have more to spend on something else, and absolutely everything we eat or buy has oodles of energy embedded (to use the customary term) in it by the processes of refining, transporting and manufacture..

I slipped petrol and food into the bottom of that table just to point out that nearly everything we use is about as energy intensive- but, of course, we BURN petrol and diesle and gas, we don't burn, or throw away the THINGS we use - or do we?? Well, as I've said above, we can recycle, and that reduces the figures in the above table by a factor of two or three (MUCH more in the case of Aluminium) - but every time our possessions go through the recyle cycle, they are still absorbing typically 5 to 10 kWh per kilogramme. A car, incidentally, even if kept permanently in the garage has an embedded energy equal to about 100km of driving. The only solution in my opinion is:

BECOMING POORER

So, how can we reduce our energy consumption down towards a level that might be sustainable? We have simply to consume less of EVERYTHING, substitution just won't do. A free-market economist would jump in here and say - no need to worry, the MARKET will take care of all that, as fossil fuels get scarcer and mining them more expensive, energy prices will rocket and, hey presto, we'll all get poorer automatically. The market has a way of getting hysterical, of booming and busting, however AND its only perfect if EXTERNAL COSTS are charged to the producer - which they blatantly are not. Sainsbury's pay me nothing for the time I waste stuck at their bloody traffic lights! And ,given a very long-tailed income distribution, the details, in terms of social injustice and conflict, might be messy.

LOOKING PRUDENTLY AHEAD

The Market is not allowed to be very good at sorting out international problems, either. Unexpected political and military conflicts get in the way. Our position in the UK and in Europe generally is one of fragility, our supply routes by air, sea, rail and pipeline stretch far across the globe. Twice last century, U-boats came close to winning wars by successful blockade of Britain. We only grew our own pit-props AFTER the first war (too late). After the unification of Western Europe following 1945, the potential aggressor became the Soviet Union, and, surprise, surprise, they built up a very large submarine fleet - over 100 nuclear and many more diesel-powered, based initially on WW2 German designs - I wonder why? Pit-props should have been on the pre-first war defence budget. The excess cost of generating energy locally, and that means, largely, renewably or nuclearly, should be considered as part of today's defence budget; an alternative to maintaining a global military reach. To quote the Economist of September 4-10^th. Renewables in Germany are growing more quickly than in almost any other EWU state .... but that is only because consumers pay a large subsidy, some Euros 10 Billion last year. Great! They're making themselves poorer! What a better use of technological expenditure than an out-of-date white-elephant Trident system.

POLITICAL STANCE

So, can Transition Wirksworth, Matlock, Middleton and Youlgreave have any significant effect? I think that the aim must be to educate a public opinion that will make very big central government action possible . And that's a remarkable statement, coming from me, a classic anti-government small-business Closet Thatcherite.

Oh, and I mentioned the baleful effect of Wordsworth, converting the useless wastes of the Lake District into a Shrine of Beauty. A new poet has recently taken up arms against the Lakeland Poets. I'm surprised Evan ( my opponent in the original Sept. 2010 debate at the Eco-Centre) didn't quote him.

Reflections in Windermere by William Wirksworth

I wandered lonely as a cloud

That floats on high o'er vales and hills

When all at once I saw a crowd,

A host, of silver windermills

Lake and trees were hid by sails

Motionless despite the gales.

Occasionally one turned, like star

That shines but rarely, hid by cloud.

They margined each high fell and scar;

Round every bay another crowd.

Ten thousand saw I at a glance,

Each one in need of maintenance.

The waves beside them danced but they

With gearbox jammed could scarcely turn

A poet could no more be gay

At sight of so much money burned

I gazed - and gazed - took one more gander

How all that cash could help Ruanda!

For oft when on my couch I lie,

Nought else to do in power cuts,

They flash upon the inward eye

Those warm, remembered fossil nuts.

The light's come on! Where's Dorothee?

Boil the kettle! Cup of Tea!