Tuesday, August 12, 2014

Shale gas in perspective

How would the footprint of a shale gas operation compare with the footprint of other ways of delivering a similar quantity of energy?

There are many dimensions to a "footprint". In this blog post, I'll look at land area, vertical height, and vehicle movements.

I'll compare a shale gas pad (which might produce 0.9 billion cubic metres of gas over 25 years) with a 174-MW wind farm and a 380-MW solar park, both of which would deliver roughly 9.5 TWh of electricity over 25 years ­– the same amount of energy as the chemical energy in 0.9 billion cubic metres of gas.

In this table I've highlighted in green the "winning" energy source for each of the footprint metrics.

Shale gas padWind farmSolar park
(10 wells)87 turbines,
174 MW capacity
1,520,000 panels,
380 MW capacity
Energy delivered over 25 years9.5 TWh 9.5 TWh 9.5 TWh
(chemical) (electric) (electric)
Number of tall things 1 drilling rig 87 turbines None
Height 26 m 100 m 2.5 m
Land area occupied by hardware, foundations, or access roads 2 ha 36 ha 308 ha
Land area of the whole facility 2 ha 1450 ha 924 ha
Area from which the facility can be seen 77 ha 5200-17,000 ha 924 ha
Truck movements 2900-20,000 7800 3800 (or 7600*)

The total land area of the facility is smallest for the shale gas pad, and largest for the wind farm. The land area actually occupied by stuff is smallest for the shale gas pad, and largest for the solar park ­– the wind farm has lots of empty land between the turbines, which can be used for other purposes.

In terms of visual intrusion, the wind turbines are the tallest, and could be seen from a land area of between 52 and 170 square km, depending how they are laid out. (To roughly estimate an area of visual influence, I computed the land area within which the drilling rig or a wind turbine would be higher than 3 degrees above the horizon, assuming a flat landscape.) By this measure, the shale gas pad creates the least visual intrusion. Moreover, the drilling rig might be in place for only the first few years of operations at the shale gas pad. The solar panels are the least tall, but the solar facility occupies 450 times as much land area as the shale gas pad. (I've assumed that the wind farm and solar parks wouldn't require any additional "intrusive" electricity pylons.)

When it comes to truck movements, all three energy facilities require lots! I've assumed that solar panels are delivered at a rate of 800 (originally 400*) panels per truck; for the wind farm, my estimate is dominated by the delivery of materials for foundations and roads at 30 tonnes per truck; the estimates for the shale gas pad are from DECC's recent Strategic Environmental Assessment and from the Institute of Directors' report "Getting Shale Gas Working". The shale gas pad might require the fewest truck movements, if all water is piped to and from the site. But if water for the fracking is trucked to and from the site, then the shale-gas facility would require the most truck movements.

What can we take from these numbers? Well, perhaps unsurprisingly, there is no silver bullet ­– no energy source with all-round small environmental impact. If society wants to use energy, it must get its energy from somewhere, and all sources have their costs and risks. I advocate deliberative conversations in which the public discuss the whole energy system and look at all the options.

Thanks to Jenny Moore, Martin Meadows, and James Davey for helpful discussions.

Photo: Wytch Farm, on the perimeter of Poole Harbour in Dorset, is the largest onshore oil and gas field in Western Europe. It is located in an Area of Outstanding Natural Beauty. The photograph shows the 34-metre-high extended-reach drilling rig, from which boreholes longer than 10 km have been drilled.

Comments and clarifications

All estimates are for energy production facilities located in the UK. The estimate of energy produced from a shale gas pad is highly uncertain, since there are no data for actual shale gas production in the UK.

The comparison in the table is based on deeming 1 kWh of electrical output from the wind to be 'equivalent' to 1 kWh of chemical energy in the form of gas. This is the conventional equivalence used for example in DUKES and in Sustainable Energy - without the hot air. The following differences between the energy sources should be noted.

  1. The three sources of power have different profiles of power generation. On an annual scale, a single shale gas well produces most power when it is newly fractured, whereas a wind-farm produces a relatively constant average power over its life. On an hour-by-hour scale, the gas from the well is dispatchable – its flow can be turned up and down at will – whereas the power from a wind-farm is intermittent.
  2. In a world in which the only conceivable use for gas is making electricity in a power station with an efficiency of about 50%, one might prefer to deem each 1 kWh of gas as 'equivalent' to just 0.5 kWh of electricity.
  3. On the other hand, in a world that values gas highly relative to electricity that is generated at times when the wind blows, one might imagine planning (as Germany is said to be planning) to use electricity from wind-farms to synthesize methane (with an efficiency of 38-48%); then one might deem each 1 kWh of wind-electricity as being 'equivalent' to 0.38-0.48 kWh of gas.
  4. If one wished to make a comparison in which both power sources are constrained to have very low carbon emissions, the shale-gas well must be accompanied by other assets. For example, if the gas is sent to a power station that performs carbon capture and storage, the gas-to-carbon-free-electricity efficiency might be about 42%, and the land area for the power station and the carbon transport and storage infrastructure should be included; assuming that these assets have an area-to-power ratio of 100 ha per GW(e), each 43.4-MW gas well (which would yield 18.2 MW of electricity) would require an extra 1.82 ha of land, which roughly doubles the 2-ha land area mentioned in the table.

My estimate for vehicle movements for large wind-farms is based on Farr wind-farm. I'm sure there is considerable variation from project to project, and I would welcome more data. For the number of truck movements required for a wind farm, I reckoned there would be about 870 movements to bring in the turbines themselves [counting an in-bound and out-bound trip as two movements], and significantly more movements to bring in the materials for roads and concrete for foundations. Some of these materials may be mined from quarries located on the wind-farm, which would then involve no vehicle movements on public roads; based on Farr wind-farm (where three quarters of the road materials were sourced on site) [sorry, I don't have a link for this fact], the road building would require 2774 vehicle movements for a 174-MW windfarm, and the foundations would require another 4140 or so – in total, about 7800 vehicle movements.

Further reading

Potential greenhouse gas emissions associated with shale gas production and use.

32 comments:

Chris Goodall said...

David,

A couple of comments, if I may.

a) It is very unlikely that a single shale pad would continue to provide gas for twenty five years if the US experience is any guide. I think a figure of eight to ten years might be a better working assumption.

b)I don't have the specific evidence to contest your assumption but I don't think the figure of 400 PV panels per truck seems right. A standard ISO container is 76 cubic metres. You can get a lot more than 5 panels per m3!!

c) I think it would be worth adding local air pollution and water use figures to your table. Obviously this would make wind and PV seem better.

d) Lastly, even if your comparison of truck movements is correct, the traffic flow in shale gas development is extremely peaky. I don't think people understand just how much many movements will occur within one week periods on the single road next to the site.

Chris Goodall said...

Supplementary point.

This web site gives a figure of 728 panels per standard 40 ft container.

(See Topoint 230 W section).

If this number is right, this is c. 2,000 container loads.

Chris

Joe Public said...

For the 'Number of tall things', it's a shame you omitted to mention that the 'one' on a shale-gas site is there only initially for the drilling.

The photo below shows BOTH the above-ground pipework, and the large building encloses the on-site generator which converts its thermal output into a direct-to-grid power connection.

http://www.cuadrillaresources.com/our-sites/locations/elswick/

Joe Public said...

@ Chris Goodall 5:30AM

"c) I think it would be worth adding local air pollution and water use figures to your table. Obviously this would make wind and PV seem better."

Perhaps Noise Pollution should be motored, too? Obviously this would make gas and PV better.

Joe Public said...

'monitored' not 'motored'

Joe Public said...

It's rather disingenuous to imply a 2MW turbine is only 100m tall.

That's only the height of the hub.

Add an additional 60m - 80m for the rotor.

Joe Public said...

Comments & clarifications item 3:

"On the other hand, in a world that values gas highly relative to electricity that is generated at times when the wind blows, one might imagine planning (as Germany is said to be planning) to use electricity from wind-farms to synthesize methane (with an efficiency of 38-48%); then one might deem each 1 kWh of wind-electricity as being 'equivalent' to 0.38-0.48 kWh of gas."

Why? FFS.

We have Cuadrilla capable of generating on-site power from shale gas. Instead of them exporting the power to the grid, should it be used to synthesize methane? Then that methane can be fed into their generator, to produce power..... which can be used to synthesise methane. ...............

Joe Public said...

"The shale gas pad might require the fewest truck movements, if all water is piped to and from the site. But if water for the fracking is trucked to and from the site, then the shale-gas facility would require the most truck movements."

However, the BBC's infographic explaining how the water table might be at risk from contamination clearly implies there's little need to truck-in H2O, apparently there's millions of gallons of the stuff just below the site's surface.

http://www.bbc.co.uk/news/uk-14432401

Anonymous said...

It is quiet obvious that solar panels can be put on roofs and don't take extra land.

David MacKay FRS said...

To Chris Goodall, yes, I didn't assume steady production for 25 years - rather, I took from the literature an assumed profile of production that is much higher in the first ten years.

The assumption of 400 PV panels per truck came from http://www.hiveenergy.co.uk/1mwp-facts.html

David MacKay FRS said...

To Joe Public who said "it's a shame you omitted to mention that the 'one' on a shale-gas site is there only initially for the drilling", well, yes, it WOULD be a shame if I had 'omitted'; but if you read the post, I said "Moreover, the drilling rig might be in place for only the first few years of operations at the shale gas pad."

Chris Goodall said...

David,

I think your use of 400 panels per vehicle movement is very unfair.

The quote you have led us to actually says:

'Typically a smaller lorry can carry around 400 panels and needs to make around 10 trips per MW of energy installed. If a larger lorry is able to be used, these movements can be cut down to as little as 5 trips per MW of energy installed.'

That suggests, as I said, a figure of about 2,000 vehicle movements for a large PV park that provides the same energy over 25 years as the shale gas pad you compare it with. I think your much higher figure is wrong.

Second, my analysis - which I accept may misunderstand the typical output of a shale gas pad - suggests that the fall in typical output for a site that averages 40 MW output (as in your example) will mean that it will be abandoned no later than 10 years after construction.

So to get the 9 TWh you postulate, you would need about two and a half pads over 25 years not the one pad you suggest.

Best wishes,

Chris

Joe Public said...

@ David MacKay FRS - 10:19 AM

" I said "Moreover, the drilling rig might be in place for only the first few years of operations at the shale gas pad." [My italics]

Years???

Would you care to double-check the duration you allege the drilling rig is in-situ for?

The single relatively low-profile drilling rig will be on site for a much shorter duration than the massive cranes needed to raise & position 87 x 100m tall turbine towers and their 261 x 60m/80m blades.

It's not unnoticed that the 'fracking-site' photo chosen, is that of Wytch Farm.

Your gas/wind/solar comparison of 25 years energy production is 9.5 TWh. Wytch Farm output peaked at 0.187 TWh...........A DAY. (i.e. just 50 days' production = 9.5TWh)

Perhaps there should also be an indication of the relative areas of wind- and solar- (subsidy) farms needed to produce the 0.187TWh power in one 24-hour period that Wytch Farm achieved.

Commenter Chris Goodall offers suggestions for comparisons intended to show wind and solar 'in good light'. In the interests of fairness, a further useful comparison would be to state the total subsidies (£) paid to gas/wind/solar for their 9.5 TWh. Mention should also be made of the amount paid to wind farms to NOT produce.

I've also noticed another misleading fact in the 'Height' row of the table:

The Heights are given as (gas) 26m (wind) 100m (solar) 2.5m. The figure for the gas pad is the height of the rig, which is then removed once production begins. However, the 2.5m for the solar farm ignores the height of its site-construction equipment. The panel-delivery truck is taller than 2.5m. The above-ground equipment on a Shale Gas Pad site (see link to Cuadrilla photo) is similar to that of a solar farm.

David MacKay FRS said...

Joe Public said: "It's rather disingenuous to imply a 2MW turbine is only 100m tall.
That's only the height of the hub."
- Me: I'm sorry, but you do talk a load of rubbish. A fairly typical British windfarm is Red Tile wind farm, which consists of twelve 2-MW
turbines with a hub height of 59 m and a turbine diameter of 82 m (thus a tip height of 59 + 41 = 100 m.
So there.

David MacKay FRS said...

@ Chris Goodall - fair enough re the solar PV vehicle movements, I agree that based on the source I gave, the figure in the table can be halved. But as for the shale production, as I said, the steep decline in production has already been taken into account.

Joe Public said...


@ David MacKay FRS 1:24 PM

"A fairly typical British windfarm is Red Tile wind farm, which consists of twelve 2-MW
turbines with a hub height of 59 m and a turbine diameter of 82 m (thus a tip height of 59 + 41 = 100 m.
So there."

Market leaders arguably are Vestas & Siemens.

Vestas spec:-

TOWER Hub heights 95 m and 125 m (50 Hz),
80 m and 95 m (60 Hz), using BLADE DIMENSIONS - Length 54 m. (Total ht 134m - 179m)

http://www.vestas.com/en/products_and_services/turbines/v110-2_0_mw#!

Siemens spec (SWT-2.3-101) is 80m Hub height using 101m diameter rotors (Total ht = 130.5m)

http://www.energy.siemens.com/hq/en/renewable-energy/wind-power/platforms/g2-platform/wind-turbine-swt-2-3-101.htm#content=Technical%20Specification

The Repower MM82 turbines you mention are sited at Red Tile wind farm have hub heights ranging from 59m to 100m (with the same 82m dia rotor). Mounted on the shortest tower means they're operating at their 'lowest' efficiency, and, their noise at ground level is highest.

So my info was hardly 'rubbish', was it?

Incidentally, your posting refers to truck movements numbers, but surprisingly fails to mention load-sizes or weights.

Typical weights are Rotor 62 tonnes, Nacelle excl. rotor 82 tonnes, Tower (80m) 162 tonnes.

Fortunately, there's photos at the link below of the massive transporters carrying the blades, and, the crane needed to offload & position them, for Red Tile.

http://www.windprospect.com/docs/project142/Red%20Tile%20uk%200607%20LR.pdf

Continuing commenter Chris Goodall's suggestions for seeking factors that favour 2 out of the 3 fuel/energy sources, how about 'avian & chiroptera fatalities'?

Obviously, static solar farms and gas fracking pads cause few, if any, bird and bat deaths.

However, a turbine having a rotor diameter of 100m at 16rpm has a tip speed of 190 mph. No wonder they're colloquially known as 'bird choppers'.


I note your estimate for vehicle movements for large wind-farms is based on Farr wind-farm. Are you (or more importantly, your readers) aware that over the Christmas 2011 - New Year period, payments totalling £399,444 were made to shut down the turbines at that wind farm. Every UK power consumer paid for its owner to "not produce". That is not "sustainable".





Joe Public said...

"Comments and clarifications

4. If one wished to make a comparison in which both power sources are constrained to have very low carbon emissions, the shale-gas well must be accompanied by other assets.

For example, if the gas is sent to a power station that performs carbon capture and storage, the gas-to-carbon-free-electricity efficiency might be about 42%, and the land area for the power station and the carbon transport and storage infrastructure should be included; assuming that these assets have an area-to-power ratio of 100 ha per GW(e), each 43.4-MW gas well (which would yield 18.2 MW of electricity) would require an extra 1.82 ha of land, which roughly doubles the 2-ha land area mentioned in the table."

This is a red herring!

Maximum energy efficiency is obtained by piping gas to the point of prime use. Modern domestic gas boilers achieve >107% net efficiency; >96% gross efficiency.

Regards

Joe Public ('O'-level Woodwork)

Robert Wilson said...

David,

Very interesting numbers as always.

In many respects the numbers are fairly predictable to anyone familiar with the power density of different sources of energy. Sadly, despite good writing on this by yourself or the likes of Vaclav Smil, knowledge about this has not penetrated that far. So, people would perhaps be shocked that wind farms have a far greater visual impact on the landscape than fracking. It's not that surprising though.

These numbers, of course, can be interpreted in many ways. Fracking is clearly more "green" if smallness is what matters. And certainly the high density of fracking means that it may face far fewer nimby problems than onshore wind farms. (UK population density is a problem according to many, yet the experience of onshore gas drilling in Holland and Pennsylvania suggests it is not a totally insurmountable one.)

However, the truck movement numbers you produce perhaps do not tell the whole story. Maybe what is really needed is truck movements per square kilometre, or per kilometre of road. Wind farms are spread over areas order(s) of magnitude greater than fracking pads. Truck movements for fracking pads, then, are much more concentrated and are possibly a greater source of nimby opposition than truck movements for wind farms. But how you quantify the causes of nimbyism is a mystery beyond me.

That aside, your numbers suggest that overall nimby opposition is likely to be more of a problem for wind farms. I always remind myself when getting the train past Drax that replacing it with a wind farm would quite probably see wind turbines covering the city of York. These problems won't go away.

Robert Wilson

Jonathan Graham said...

David,

I wonder if your comparison is not a bit of apples and oranges.

Your post refers to shale gas wells as one of three 'sources of power', but a shale gas well simply takes the energy from the ground. It does not generate anything, unlike the wind turbine.

Would it not be more accurate to compare both a shale well and a power station before you get to a fair comparison?

Mark Brinkley said...

David,

Why not compute the carbon footprint as well? Maybe that would stop the likes of Matt Ridley using this feature as another way of bashing wind farms.

On second thoughts, perhaps not, as he would simply suggest all that added carbon would be good for us. I seem to recall he makes the claim that excess CO2 is turning the planet greener.

Joe Public said...

@ Robert Wilson 7:53

"Maybe what is really needed is truck movements per square kilometre, or per kilometre of road."

Only if the objective is to provide stack figures in favour of the least energy-dense source.

There is generally a single road entry to a site.

The road that that serves that single entry is usually approached from two directions.

Irrespective of the area of the site.

Perhaps an alternative measure could be truck movements per hour of production. For shale, simply divide by 24. Would anyone care to guess the denominator for wind and solar?

Regards

Joe Public ('O'-level Woodwork)

Joe Public said...


@ Jonathan Graham 8:55 AM

"Your post refers to shale gas wells as one of three 'sources of power', but a shale gas well simply takes the energy from the ground. It does not generate anything, unlike the wind turbine.

Would it not be more accurate to compare both a shale well and a power station before you get to a fair comparison? "

A shale well provides a fuel, not energy. That fuel is flexible enough to be used as and when required. The output from a power station cannot (economically) be stored. If it's not used when generated, it's 100% wasted.

One wind-subsidy farm Mr MacKay chose as an example received in one week (Christmas 2011 - New Year period, payments totalling £399,444 to shut down its turbines. Every UK power consumer paid for its owner to "not produce".

Regards

Joe Public ('O'-level Woodwork)

Joe Public said...

Ooops another slip from me.

"A shale well provides a fuel, not energy. "

Should be "A shale well provides a fuel, not power."

Mat Hope said...

Hi David,

Interesting analysis. Just a quick Q on the shale gas truck movements. You say you got the figures from the IOD and DECC SEA reports. Whichever way I cut DECC's figures (from p30-31), I can't seem to get 20,000. I was wondering how you got that?

Thanks a lot,
Mat

Anonymous said...

It was rather unfair to dispute Mr Publics turbine height figure, when the actual wind farm wasn't named in the original comparison.

It's almost as though a farm with short turbines was then selected after he'd questioned the data in the table.

It doesn't add up... said...

Mark Brinkley:

Many of our windfarms are bad news with regard to carbon dioxide emissions:

http://www.telegraph.co.uk/earth/energy/windpower/9889882/Wind-farms-will-create-more-carbon-dioxide-say-scientists.html

David Flint said...

I'm astonished that you don't include greenhouse gas emissions as an environmental impact. That seems far more important than the things you do include and would tell very heavily against shale gas.

Joe Public said...

@David Flint 12:39

"I'm astonished that you don't include greenhouse gas emissions as an environmental impact. "

They certainly do have an impact, the clue is in their name. CO2 is plant food.

BTW - have you considered how much excess greenhouse gas is created by running lower-efficiency OCGT plant to cope with the unpredictable intermittency of wind & solar generation?

paul taylor said...

Well thank you very much for being a fan of math Professor MacKay . As a supporter of fracking in Canada there are some factors I am sure you may indeed not know of. Length of production and flow rates are increasing. Drilling ten wells on a pad now is taking months not years especially in proven shale plays. A two Hectacre well pad could host 500 4 megwatt GE jenbacher engines if indeed the gas supply requirements were met . That would also mean an electric switch yard . The nature of GE Jenbachers is they are containerized and woukld be best at the end of the gas delievery lines in towns and cities . There is no loss of energy with Natural gas lines unlike a remotely located renewable energy development. What may not be included is the additional power instrastruture when you spread your energy plant over 950 to 1400 hectares . With Cogen systems like the Jenbacher you also get 3000 additional megawatts of heat energy which very often is used with Greenhouses or district heating for urban settings. I would certainly be interested in the production rates you are using for a well pad of ten wells . A huge disadvantage of a solar park is you actually might be taking agricultural or forestry land out of production. Thanks Paul Taylor

Joe Public said...

@ paul taylor August 17, 2014 at 10:42 AM

Thanks for those interesting facts.

One observation:

"A huge disadvantage of a solar park is you actually might be taking agricultural or forestry land out of production."

Not necessarily. It's possible for some subsidy-farmers to 'double-use' some fields by elevating the panels & grazing sheep.

Google: 'solar panels sheep grazing'

paul taylor said...

@Joe Public thank you back for the information on Synthetic Methane production . When I generally think of agriculture I am thinking Grain and Produce . From the pictures I have seen of Solar farms it seems so tightly packed for rows of crops or forests of trees which both take CO2 out of the atmosphere . Going back to developments in shale on this side of the atlantic . A company named IMG Midstream is building 20 megawatt clusters of GE jenbacher generators in Nirtthern Penn State to take advantage of over abundant shale gas. IMG midstream is also offering partnerships with Commerical Greenhouse Companies to take advantage of their Jenbacher CO2 striping abilities . 20 megawatta can provide enough CO2 and heat for 100 hectares of Greenhouse Thanks PT

Joe Public said...

Another woeful underestimation of the impact of wind turbines:

The article states "Area from which the facility can be seen 5200-17,000 ha"

However, evidence to a Parliamentary Select Committee in 1999, (the Sinclair-Thomas Matrix) shows the visual impact of a 95m high turbine having a moderate visual impact up to 17 km, with gradually less impact to 35 km.

Based on 17 km, the area affected would be 90,800 hectares, rather than 5,200-17,000 ha.

http://www.parliament.the-stationery-office.co.uk/pa/ld199900/ldselect/ldeucom/18/18a04.htm

[5,200 ha equates to a radius of less than 2.6 miles. I suggest the unusual unit used (ha) for a visibility range, was deliberate obfuscation. Shame on you, Professor MacKay]