North Sea Oil, DECC and Climate Change

2012 February 2
by Chris Vernon

This week DECC (that’s the UK Government’s Department for Energy and Climate Change) opened the 27th round of offshore petroleum licensing. This is a process of offering licences for offshore oil and gas exploration and production in the UK administered part of the North Sea.

photo: Creative Commons / Genghiskhanviet

The associated press release described this as “new opportunities for UK oil and gas exploration” … which “ensures the UK gets maximum benefit from our resources.” The Energy Minister Charles Hendry said “With around 20 billion barrels of oil still to be extracted, the UK Continental Shelf has many years of productivity left.”

Given the UK’s commitment to carbon dioxide emission reductions and the global agreement to limit warming to 2°C, do we need to spend time, money and energy exploring for more oil and gas to extract from the North Sea? If the limits imposed by the Earth system and our political system’s response establish a total amount of future emissions, isn’t it quite likely that existing, already discovered reserves of fossil fuels are more than sufficient? If in fact it would be very unwise to burn all the current reserves, why bother looking for more? George Monbiot made a similar point as the Government were approving new coal mines: Leave It In The Ground

It strikes me as odd, that neither the press release nor any of the other documentation associated with this new licensing phase even mentions the carbon dioxide emissions associated with the production and inevitable combustion of the newly discovered oil and gas they are hoping for. This omission leaves DECC looking schizophrenic, with one hand attempting to meet onerous emission reductions whilst the other simultaneously desperately scratches out the last remaining fossil fuels available.

Bicycle Maintenance

2012 January 24
by Chris Vernon

Bicycles are great. I ride mine almost every day. To the office, around town, in the countryside, to the allotment, with friends or on my own. The sad truth however, is that an awful lot of people who could ride bikes, don’t. In the UK only 2% of journeys are made by bicycle, compared with 9% in Sweden, Finland and Germany and 25% in the Netherlands (Bassett et al. Journal of Physical Activity and Health, 2008). Along with our lacklustre use of renewable energy, our cycling rates are also languishing at the bottom of the European table. I’d like, and expect, to see more people riding as energy prices rise, the economy continues to struggle and environmental pressures (both local and global) increase. A five-fold increase sounds incredible, but would only equal what many other European countries are already doing, and still represent only half the amount of cycling the best countries manage. It is achievable.

In April last year I spent two weeks in Lincolnshire with Alf and Teresa Webb at The Bike Inn completing my City & Guild’s qualifications in Cycle Mechanics.

Two weeks at The Bike Inn, Lincolnshire

City & Guilds Level 1& 2 Cycle Mechanics (3902) and The Bike Inn ‘Certificate of Attainment’

Since completing the training I’ve been working with Ross Taylor of Taylored Cycles offering the award winning Bristol University Cycle Surgery to staff and students and volunteering with The Bristol Bike Project.

Bristol University Cycle Surgery

Bristol University Cycle Surgery

The Bristol Bike Project also won an award. We won the Grassroots category of the 2011 Observer Ethical Awards and here’s the video:

Tools are important and I now have a fairly comprehensive toolbox. I’ve also recently built a bicycle wheel truing stand, more details here: bicycle wheel truing stand for building and repairing wheels. The only tools I’m still lacking are for the headset (press, remover, star nut fitter…), frame preparing tools (bottom bracket taps, crown race cutter) and the all important workstand!

This year I’m venturing into the world of frame building, with a one week course, again in Lincolnshire with Dave Yates and another with the soon to be opened Bicycle Academy. I say soon to be opened as they are currently setting up their workshop following a fantastically successfully crowd funding. They succeeded in raising over £40,000 in under a week though the new project.

Watch this space for my adventures in frame building!

Hat tip, James, Bristol Bike Project 🙂

Bicycle Wheel Truing Stand

2012 January 18
by Chris Vernon

A bicycle wheel truing stand is a must have tool for any bike mechanic. The shape of the wheel, its lateral (wobbling side to side) and radial (up and down) trueness are a function of spoke tensions. By using a spoke key and tightening either odd spokes or adjacent pairs of spokes, out of true wheels can be gradually straightened out.

There’s nothing fancy about a truing stand, it simply has to hold the wheel firmly in place as you spin it, and have indicators of the two degrees of trueness. Commercial stands are at least £50 and you can pay a lot more. There’s no need though. I learnt to build wheels with Alf & Teresa Webb at The Bike Inn on an old cast-iron stand with perfect results.

Here’s the stand I built, loosely based on Roger Musson’s design from his book, The Professional Guide to Wheel Building:

Bicycle Wheel Truing Stand

The completed stand with a 700c wheel.

The upright in the foreground can slide in and out to accommodate a range of hub widths from 100 mm front hubs, up to 150 mm dowmhill rear hubs. The two gauges are free to move around on the white surface making adjustment very fast, no fiddly screws to wind in and out, no levers, and swapping from a 700c wheel to 26″ is instantaneous. The gauges are black plastic which show up great against the white background. The corner gauge is used for lateral trueness with the longer angled one for radial trueness.

Bicycle Wheel Truing Stand

Obviously for radial trueness (is the hub in the centre) the tyre must be removed.

In total it cost about £15, I bought the M8 nuts and bolts, the angle brackets and a lump of aluminium for the ‘jaws’. The wood and plastic was all scavenged from the street/skips.

I am still lacking a dishing gauge though, haven’t quite worked out how to make one I’d be happy with yet. Any bright ideas, let me know!

A Lot of Hot Air? David Mackay Fudges the Figures in Favour of Nuclear Power

2011 October 6
by Chris Vernon

Last week I had the opportunity to attend a lecture at the University of Bristol’s Cabot Institute given by Prof. David MacKay, chief scientific adviser to DECC (UK Government Department for Energy and Climate Change). There were two main focuses of his lecture: firstly, a discussion of various sources of energy and secondly, an introduction to DECC’s 2050 pathways tool.

The pathway tool I like and I would encourage anyone interested in the UK’s future energy system and associated carbon emissions to have a play with it. All I would say is that, like many scenario analyses, it is too narrow. The whole point of carrying out scenario analysis is to explore the possibility space. The DECC tool assumes both population and GDP growth. These parameters may be “out of the scope of consideration”, but I would have liked the energy and emissions tool to allow the exploration of steady-state and also economic contraction scenarios. I got the impression MacKay would also have liked to include this flexibility but he said Westminster wouldn’t allow it.

I did not like his comparison of energy sources though. He promotes the use of a single metric to compare energy sources: power density. This means the amount of power delivered per unit area, expressed in watts per square meter [W/m2]. The lecture focused on wind and nuclear power but the analysis can be done for solar power, energy crops, or fossil fuelled power stations.

The headline results were that wind has a power density of 2.5 W/m2 whereas nuclear delivers 1000 W/m2. Sounds good for nuclear and not so good for wind! But the difficulty is that MacKay is comparing apples and oranges.

In order to compare things quantitatively as MacKay is attempting to, it helps if units are the same. MacKay’s m2 of wind farm are not the same as his m2 of nuclear power station. There are three main problems with this analysis:

  • Layering
  • Time
  • Externalities


Cows under Wind Turbines

Cows in a wind farm

The square km of land underneath a nuclear power station is 100% used up. There is nothing else that land can be used for. However, with many renewables the land isn’t used up in a comparable way. Solar panels can be installed on the top of existing buildings requiring none of the underlying land to be used up. Wind farms use around 5% of the land under the turbines, leaving the remaining 95% available for other uses (such as livestock or crops). This 5% compared to 100% improves the power per unit area of wind turbines by a factor of 20.

MacKay made no allowance for the time dimension. He just divided the power of a wind farm or power station by its area. This fails to consider that the nuclear power station took at least 10 years to build before its ~40 year generating lifespan, followed by a ~100 year decommissioning period. In contrast, the wind turbines are generating within months of build commencing and decommission can be similarly swift. This results in the nuclear power station using up the land for around three times longer than the period of time it is generating for, which effectively reduces its power per unit area by a factor of three.

MacKay also made no allowance for the land requirements outside the perimeter fence of ether the nuclear power station or wind farm. This discounts the land required for the uranium mine, the uranium processing, the water required for cooling and importantly the waste storage. The wind turbines also required an iron ore mine, steel foundry and factory. I am not able to quantify the differences in land requirement but I expect the nuclear power station’s “invisible footprint” to be larger, especially when multiplying up the area used for waste storage by the duration for which the land is required (potentially many thousands of years) as described above. Finally, nuclear power stations have a non-zero probability of catastrophic failure, then requiring exclusion zones of hundreds of km2 for decades (Chernobyl, Fukushima).

A Comparable Analysis?
A comparable analysis would consider the fractional land use (layering) of an energy source, the total duration for which this land was used (time) and the land required beyond the immediate installation (externalities). That MacKay’s analysis doesn’t consider these aspects, and that they impact the final results by many factors suggests to me that this metric of comparison is oversimplified. I do not object to the use of the power density metric but would like to see it done properly; otherwise it is comparing apples and oranges and is not useful information.

I don’t doubt that MacKay has considered the points raised above. I am worried that the seemingly-deliberate omission of these factors is presenting an overly political bias towards one source of energy.

According to the above back-of-the-envelope estimates, I would therefore amend MacKay’s comparison of nuclear (1000 W/m2) and wind (2.5 W/m2) to the more realistic 300 W/m2 (accounting for time) and 50 W/m2 (accounting for layering). These adjustments reduce the difference between nuclear and wind from 400- to 6-fold. A further unquantified adjustment to account for externalities is likely to reduce this still further.

Of course, in the final analysis the total land area that is needed is reflected by the naive energy densities MacKay calculates – to generate most of our power from wind (or solar, or biomass) would indeed require vast proportions of the countryside or sea surface to be utilised, and this is an important consideration. However, given the above considerations, it is clear that the headline numbers MacKay is promoting are unfair to renewables, and overly generous towards nuclear.

Food Dehydrator

2011 August 30
by Chris Vernon

We have an apple tree on our allotment, it’s a Worcester Pearmain (we think) and by late August we have more apples than we know what to do with! This variety don’t store well and after giving away a couple dozen we still have over 50 on the table. Drying seems like a good idea but the food dehydrators on the market cost around £50 for a small one (0.38 m2 drying area) to over £200 for a larger one (1.35 m2). With a bank holiday Monday to kill, we joined the crowds at the hardware store to see if we could knock something up ourselves.

We did skip a few bits of wood and if we’d planned this for more than 15 minutes could certainly have skipped all the wood. As it happened though we spent £6.90 on the wood.

Wood £6.90
Trays 7 x £1.75 = £12.25
Cable £1.80 (4 m)
Plug £0.64
Lamp holders 4 x £0.98 = £3.92
Switch £1.72
Bulbs £1.97 (4 x 60W)
Screws ~60 = 0.40

Also a little bit of wood glue and some foil and duct tape (say 50 pence).
The cardboard is of no cost and the fan (120 mm, 12 v) came from an old computer case (these can be bought for £3 from good computer shops).

Total cost = £29.90

Call it £30.50 or £34 once we’ve added the 8th and 9th racks there’s room for. The shop only had seven in stock.


The materials for the dehydrator.


The cats were very helpful...

The basic idea is a simple wooden frame, with lights at the bottom to provide the heat and a fan to provide the air flow. All the joints were drilled, counter sunk, glued and screwed to produce a pretty robust frame.


Drilling - no power tools used here!


Each corner post has little ledges for the racks to rest on.

The four 60 W bulbs are in two parallel sets, each with its own switch. This gives us two heat levels of 240 W and 120 W.


Four 60 W bulbs provide 240 W of heat (and a small amount of waste light).

The sides are covered with thick cardboard. The 120 mm fan is fitted into the middle of the cardboard base, separating the bulbs from the heating area. It’s a DC fan, running off an old transformer I had kicking around.

Food dehydrator

All assembled with the 120 mm fan in the base.

And here we are in action!

Food dehydrator

First run!

In its current configuration the drying area is seven trays of 0.094 m2 totalling 0.66 m2. The capacity is 9 trays so a total of 0.85 m2, over twice the capacity of the cheapest commercial version. At least £10 of the final cost of £34 could be easily avoided by getting the wood and cable from a skip. The switch, bulb fittings, and plug could also probably be skipped with a little more effort. The trays were the most expensive part, they do look nice but similar function could have been achieved far cheaper by using a square metre of fine wire mesh from a garden centre. The apples do seem to be sticking to the metal a bit, so maybe plastic trays would work better? Or maybe we need to use a little bit of oil/butter on them next time.

Here’s the result:

Dried apple

The first batch!

It took around eight hours, used close to 2 kWh which is around £0.25 of electricity. Next up the solar adapter for sunny days! Whilst some did stick to the trays, these were the thinner ones; they were too thin! The best results are from the thicker slices, 4 mm seems around right.

The temperature with all four bulbs on was a stable 35 C, which looking at commercial dehydrators seems on the cool side. Be interesting to know how much airflow they have though. Now to try some courgettes! 🙂

Allotment Update No. 18

2011 August 13
by Chris Vernon

Follow the allotment series here.

Everything is growing really fast this month. After a relatively cool and wet July in Bristol (16.9C compared to the 30 year average of 18.3C along with 18% more rain) August seems to be a little warmer. Here’s the crop from the 13th August:


These are the first of our carrots along with lots of squash, courgettes, blackberries and chard.

Of course we can’t hope to eat this much squash, though we’ve had a good go! Most of this load was given away at a BBQ last week. The variates here are Parador courgettes along with Sunburst, Sunshine and Turks Turban squash. We also have some Crown Prince, Harrier, Confection and Harlequin on the plot which should all keep fairly well, along with a prolific pumpkin. The carrots are Jaune Obtuse de Doubs’ Yellow Carrot, a non-hybrid from Real Seeds. These carrots were planted on 26th March. The squash plants are mostly growing in front of the sweetcorn:

Sweetcorn and Squash

Sweetcorn and Squash

Our monstrous sweetcorn! Dave’s a handy 6 foot rule so these 55 sweetcorn plants are around 9 foot. Looking at other allotment plots and commercial fields our corn is exceptionally tall, however, it seems to have fewer cobs forming than we’ve seen on other plants. The seed was another non-hybrid, called Golden Bantam Improved.


The leeks are continuing to bulk up


We're letting this one grow!

This ‘marrow’ is actually a Romanesco courgette.

We sowed more carrots on 10th July. These should be ready by the end of October, thanks Amanda and Dave for weeding!


Yellow carrots planted 10th July


Here's our haul from 2nd August 2011

A few photos from earlier. This is the first half of the plot, as it looked on 17th July:

Allotment plot

Chard, leeks, rhubarb and squash in front of the sweetcorn


We're eating the turnips much smaller than this... but it's fun to let one grow!


The kittens are curious and enthusiastic creatures, not often helpful though!

Allotment Update No. 17

2011 August 1
by Chris Vernon

Follow the allotment series here.

A round up of recent progress on the allotment.

These photos are from 9th of July:


These leeks had a slow start. The rabbits ate them almost down to the groud a couple of months ago. Amazingly they seem to have come back pretty well.


The squash are growing fast now, looks like we'll have a lot! These are called Sunburst and have a wonderful scalloped edge.


The kale's done really well. More than we can eat! And in the background the rapidlly growing sweetcorn.

A few days later, 23rd of July and we’ve got a good harvest:


The potatoes are the first earlies, Foremost. That's the crop from three plants. We've also lifted the second garlic patch, this was planted in January and seems pretty similar to the stuff that went in in November. Also a good crop of courgettes, turnips, chard, onions and blackberries.


Sweetcorn are looking lush now, lots of foliage but not much sign of corn yet!


The chard has been a great success. We have yellow, red and a more conventional leaf beat, very similar to spinach.


We've planted sweetpeas and sunflowers against the fence for a bit of colour.

Runner beans

The beans have been a nightmare, bad weather, rabbits and voles have had most of them. We have some dwarf runners that are finally doing what they're meant to do now.


2011 June 21
by Chris Vernon

Here are our two kittens, Bert and Ernie.


Bert on the left, Ernie right.


Bert's hanging back!

And here’s a short video recorded on 20th June 2011 – they do this a lot!

Allotment Update No. 16

2011 June 11
by Chris Vernon

Follow the allotment series here.

After a record-breakingly dry spring, we’ve finally had some wet weather and the plants have really appreciated it. The rhubarb, which had been looking increasingly unhappy despite regular watering, is now thriving:


Rhubarb, these started as four small donations from our allotment neighbour.

The remaining onions (some were nibbled by hungry rabbits) are starting to swell:


Onions, this is our 2nd bed of onions. They went in after the super cold December and have done better than the first lot.

And the sweetcorn are looking great!


Sweetcorn, current count is 55 plants from the 60 kernels. Not bad!

Our squash have come from various sources. Some we grew ourself from seeds, some we got as little plants, others from friends and family:


Our largest squash, the donated pumpkin from Will & Kaz. 🙂


We have 23 various squash/pumpkin/courgette plants in total.

The beetroot and parsnips are coming along well. We may have underestimated the germination rate of the parsnips and overestimated our likely consumption of them…. Anyone out there who would like some parsnips in a couple of months’ time??


In the foreground, the eldest beetroot, behind them younger. In the background parsnips and potatoes.

After netting the chard to prevent the rabbits getting at it, it has grown up quickly. Tasting some directly from the plant, I can see why the rabbits liked it so much. The ordinary green ones taste best, but the yellow and red look exciting:


Rainbow (at least red, green and yellow anyway) chard.


The kale has been growing fast since it finally started raining a couple of weeks ago.

The garlic that we put in in autumn had completely died, so we were forced to harvest them all, although it’s a bit early. Maybe they were tricked by the dry spring into thinking that summer had been and gone. Turnips that we had almost given up on have also done remarkably well, so we thinned them out and ate some in white sauce with the chard.


First real harvest this year. Chard, turnip and garlic.

Time to stop buying vegetables!

Allotment Update No. 15

2011 May 24
by Chris Vernon

Follow the allotment series here.

Just a quick post today. All the photos below were taken on the evening of Tuesday 24th May.


Parsnips, three sowings with each separated by a few weeks (5th March, 20th March and the most recent mid-April).


Potatoes, really impressed with how vigorous they are. They were planted on 20th March so this is almost 9 weeks growth. Only a few more weeks until the first earlies should be ready!


Beetroot, planted 20th March - not as impressive as the potatoes!

Strawberries and squash

18 Strawberries (9 Elan and 9 Roman) and 9 squash plants.






Sweetcorn, we have around 60 plants at ~1 foot spacing in a large bed.