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Author Topic: Solar-powered trains are closer to reality than we might think  (Read 9828 times)
Tim
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« Reply #15 on: March 20, 2017, 08:16:23 pm »


There's certainly a balance to be reached, but my point was more that we don't want to go too far with it and end up with too much pressure on agricultural land. I can't help but think some of the sites I have seen could've been better sited on poorer quality sites.


absolutely agree with all of that.  To my mind it is a bit like building houses on farmland.  Much easier to justify if you have used the non-farmland brownfield sites first.  There are still plenty of roofs to put panels on.

Poor quality farmland is also often quite good for growing energy crops (willow coppice etc) which are excellent for wildlife.
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Tim
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« Reply #16 on: March 20, 2017, 08:34:29 pm »

Fields used for solar farms are not totally taken out of agricultural use, but the yield of crops or meat animals is much reduced since between one third and one half of the sunlight is gathered by the modules and is therefore not available for plant growth.

That is true in some circumstances but actually it is a bit more complicated in reality.  Your suggestion that the sunlight taken by the PV-cells is directly proportional to the loss of plant growth is often not the case because for many plants and many conditions, the rate limiting variable for plant growth is not sunlight.  It might be water, temperature or CO2 availability.  Intense sunlight on a plant leaf is, at best partly wasted (the photons excite electrons in the leaf which then are "captured" by chemical compounds, but the chemical compounds can't defuse in and out of the photosynthetic site fast enough and so the electrons lose their excitation and drop down to a lower energy level and the energy is lost as heat) and at worse damaging (excited electrons = free radicals = damage to cells).  As well as a complicated light harvesting apparatus (which is what they call it), plants also have a complicated photo-protection system.

I have did a bit of work on algal growth once (for biofuels) and the best yields are in ponds that are stirred so that the cells spend a second at the top of the water column, capture some light and then retreat to a low light region of the pond to do the chemistry that follows and to escape the damage. There are also pond designs that partly shade the ponds with solar panels.  If you want to get the algae really cooking you don't turn up the sunlight, you bubble CO2 into the pond (stick the pond next to a power station or oil refinery and you qualify as a "carbon capture" technology)

I don't have any data from English field trials but I expect the answer will strongly depend on the crop and the temperature and light intensity of the site.  There is of course an argument that all solar cells should be in a country with more sunlight than the UK, but you could equally say that all farming should be moved to somewhere with a better climate for crop yields.

Obviously, driving a combine between rows of panels is a challenge, so the usual method is for a sheep to harvest the crop.



 
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ellendune
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« Reply #17 on: March 21, 2017, 11:45:23 pm »

I share the concerns of any land taken out of agricultural use for solar farms.

However what is "good" agricultural land?  Some would argue that land that is only good for pasture, which is the case in many parts of the West and South West, is not good.

Agricultural land classifications support this.  Around here (Swindon and North Wilts) most of the lowlands are Grade 3b (Moderate) or 4 (Poor).  The better land is up on the downs where there is some Grade 2 (Very Good).  The only solar farm I can think of on good land is actually on the old RAF airfield at Wroughton which is surrounded by Grade 2 land. The airfield is however not classified because it was in non-agricultural use.   

The use of grade 3b or grade 4 land concerns me less than it would if it was Grades 1, 2 or even 3a.   
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Tim
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« Reply #18 on: March 22, 2017, 09:04:37 am »

I share the concerns of any land taken out of agricultural use for solar farms.

However what is "good" agricultural land?  Some would argue that land that is only good for pasture, which is the case in many parts of the West and South West, is not good.

Agricultural land classifications support this.  Around here (Swindon and North Wilts) most of the lowlands are Grade 3b (Moderate) or 4 (Poor).  The better land is up on the downs where there is some Grade 2 (Very Good).  The only solar farm I can think of on good land is actually on the old RAF airfield at Wroughton which is surrounded by Grade 2 land. The airfield is however not classified because it was in non-agricultural use.   

The use of grade 3b or grade 4 land concerns me less than it would if it was Grades 1, 2 or even 3a.   

interesting thanks. 
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caliwag
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« Reply #19 on: March 22, 2017, 11:16:36 am »

Worth following up Ecotricity's promotion of Greengas, ie methane from grass...several sites awaiting planning approval, mainly in areas close to fracking sites..as an eco alternative, with low impact and many 'green' advantages...local ecology benefits etc...all explained on their green gas site...not directly solar, but part of the low-impact mix!
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Tim
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« Reply #20 on: March 22, 2017, 05:39:13 pm »

Worth following up Ecotricity's promotion of Greengas, ie methane from grass...several sites awaiting planning approval, mainly in areas close to fracking sites..as an eco alternative, with low impact and many 'green' advantages...local ecology benefits etc...all explained on their green gas site...not directly solar, but part of the low-impact mix!

I do wonder if this indirect solar is better than PV panels.  It solves the storage problem.
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ellendune
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« Reply #21 on: March 22, 2017, 09:51:25 pm »

I do wonder if this indirect solar is better than PV panels.  It solves the storage problem.

Yes but how does it compare in efficiency at producing energy per acre of land? 

Also I assume the land can no longer support sheep, so it takes even more land out of food production.

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Red Squirrel
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« Reply #22 on: March 23, 2017, 05:15:38 pm »

While we're thinking about efficient land use: for fear of taking the lid off a can of soya protein worm substitute, it's interesting to look at feed conversion ratios.

For beef cattle, an FCR of about 6 is common in the US, but in the UK it looks like 8 is more common - i.e. you put 8 times as much food in as you get out. For sheep, it looks pretty similar - between 5 and 10:1.

According to one source we'd need 750km2 of solar panels to power every household in the country, which is about 0.3% of the land area. But, um, maybe if we ate a bit less meat and a few more vegetables, there'd be more than enough room for all these panels.

Yes I do realise that that we'd also need a lot of batteries to give these panels 'turning mass'. And yes, there's a carbon cost associated with making these things. But doing nothing doesn't seem that great an option

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Noggin
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« Reply #23 on: March 24, 2017, 02:01:59 pm »

Also I assume the land can no longer support sheep, so it takes even more land out of food production.

Although I believe that if you are looking purely at carbon emissions alone, it's actually less polluting to raise sheep in New Zealand and ship the meat here. Obviously that's not great for our self-sufficiency in food though.
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ellendune
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« Reply #24 on: March 24, 2017, 03:03:00 pm »

Also I assume the land can no longer support sheep, so it takes even more land out of food production.

Although I believe that if you are looking purely at carbon emissions alone, it's actually less polluting to raise sheep in New Zealand and ship the meat here. Obviously that's not great for our self-sufficiency in food though.

I do not understand why that might be.  Is it because we give supplementary feed to sheep here and New Zealand sheep only eat grass?

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grahame
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« Reply #25 on: November 25, 2020, 08:20:16 am »

Byron Bay Railway headline picture at https://www.bbc.co.uk/news/av/stories-55044198 but video majors on Aldershot direct feed and looks wider.   An important subject to bring back up

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How sunshine can make the railways greener

A solar farm plugged directly into the rail network is just one way that the railways are using solar energy to power trains.
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grahame
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« Reply #26 on: January 20, 2021, 01:17:03 am »

From the letters page in the Melksham News.

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Along with the government's announcement to ban the sale of new petrol and diesel cars in 9 years' time, UK rail companies are testing and developing solar panels alongside some of our railway tracks to feed electricity into passing trains. India, which has a massive rail network moving millions of people around the sub-continent, has adopted the use of solar farms to power there trains, and Australia has trains with solar panelled roofs to generate electricity.

re: Suggestions in the Melksham News that we learn lessons from solar powered railway trains in Australia, India and (!) Aldershot.  Management summary - yes, BUT they are different cases.

Byron Bay (in Australia) is an interesting.  The line in question is quite short - total running time 200 minutes per day. The solar panels on the train generate some power, but most of it is from batteries which are recharged at the main station between runs - admittedly from solar panels on the roof of the station for the most part.  It's a leisure line, so the train only runs in the daylight.

Contrast - Melksham. 
* Our "shuttle" train is running for around 800 minutes per day, rather than 200.
* Our round trip times of 95 minutes rather than 20, so would need to store more "juice".
* Our train runs from very early (pitch black at 05:17) and into the dark evening
* Melksham is much further from the equator meaning much shortened charging days in the winter
Byron Bay teaches us lessons - but also shows where we need to develop further and modify .

There are other examples of solar panels providing power to run trains - UK and India - but in those cases the electricity is fed into the overhead wires or 3rd rail rather than being generated or stored on the train, and supplemented with electricity from other sources when the sun ain't shining of even out behing the clouds.  Mixed technologies - with batteries, overhead feeds and diesel all available on the same train are coming in more and more too.  Network Rail's core decarbonisation plans include electrification through Melksham as part of their core network. See http://www.passenger.chat/24005 for links.
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broadgage
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« Reply #27 on: January 20, 2021, 01:25:34 pm »

Powering a train DIRECTLY by solar power is unlikely to be viable.
Solar power can of course be used to power an electrified railway, or to charge a battery train.

I have previously suggested the fitting of PV modules to seldom used rolling stock, but that is to keep seldom used batteries in good condition, not to propel the train.

Many UK stations could usefully be fitted with grid tied PV modules, note that no agricultural or other land is taken up by fixing PV modules to existing buildings.
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A proper intercity train has a minimum of 8 coaches, gangwayed throughout, with first at one end, and a full sized buffet car between first and standard.
It has space for cycles, surfboards,luggage etc.
A 5 car DMU is not a proper inter-city train. The 5+5 and 9 car DMUs are almost as bad.
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« Reply #28 on: January 20, 2021, 04:20:14 pm »

There are number of renewable energy systems trials in development and others options being explored, also energy recovery is being looked at.

The renewable energy systems are being developed for ancillary systems ie other than traction power, such as signalling power, level crossings, staff access and walkway lighting etc
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broadgage
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« Reply #29 on: January 20, 2021, 05:06:57 pm »

One type of product that may be of particular interest for railway use are semi transparent PV modules.
Ideal for platform canopies, waiting shelters, cycle stores and the like.

They block excessive heat, light, and glare, but admit enough daylight to avoid the sheltered area being unduly gloomy.


https://archello.com/product/semitransparent-pv-modules

This sort of thing. Link to illustrate the TYPE of product to which I refer and not by way of recommendation of any particular brand. Many alternatives exist.
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A proper intercity train has a minimum of 8 coaches, gangwayed throughout, with first at one end, and a full sized buffet car between first and standard.
It has space for cycles, surfboards,luggage etc.
A 5 car DMU is not a proper inter-city train. The 5+5 and 9 car DMUs are almost as bad.
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