Great Western Coffee Shop

From The Guardian (https://www.theguardian.com/sustainable-business/2017/feb/15/solar-powered-trains-uk-india-renewables-tracks-electric)

How about wave power at Dawlish?  Power generation from the fierce surge along the sea front, building infrastructure to absorb the energy that currently attempts to tear apart the line and damages the trains, feeding into the local network for electric trains to Barnstaple, Exmouth and Paignton. Bimodes running under the wire could take advantage too, with renewable electrics used for starts from Cullompton all the way up Dainton.

How about tidal power at Pilning?   The Severn has one of the largest tidal flows of any river, and the line through Pilining is being electrified, been if electrification to Bath and Bristol is cut short at Thingley.

Do solar panels really generate enough power to be of use? You'd need some serious array size, surely?

Don't know ... but I was astonished as to how few modern windmills you needed to runs a train these days (I think it was one when under heavy power?) so we shouldn't rule out local renewables.

to directly power trains might not be very sensible. A large and costly PV array would be needed to meet the peak demand , and this costly equipment would lie idle between trains when no train was in the electrification section to which the PV array was connected.

Much better IMHO to install standard grid tied PV arrays that feed energy back into the grid and thereby offset some or all of the energy used by electric railways. Small arrays of a few KW are widely used domestically, there is nothing fundamentally different about fitting them to railway buildings rather than to homes.
Larger solar farms are also a well understood technology and are connected into the grid at high voltage, space permitting they may be installed on railway property.

Electric traction with its intermittent demand of many megawatts is one of the most challenging types of load to supply from relatively small scale generation, renewable or otherwise. Indeed the lack of a grid system able to supply large but intermittent traction demands was in the past a good reason for the retention of steam or diesel power, despite electricity being in many ways superior.

Let's not forget that the railway also consumes large amounts of electricity within stations, much of which is a fairly predictable load.

Blackfriars station has solar panels in the roof generating up to 1MW, or 50% of the station's power requirements, and in Belgium they had to put the new high-speed line in a two-mile long tunnel through a forest to avoid felling too many protected trees and stuck something like 16,000 solar panels on top of it.

I suspect the issue is that cuttings and embankments are rarely going to be orientated favourably, whilst access is likely to be tricky and expensive. That said, I think someone has put in planning permission to put some next to the railway line at Bedminister in Bristol. Station roofs are probably fairly ideal locations for panels, provided that they can take the additional weight.

Solar panels are effective through at least 180 degrees, and I understand can be most effective if facing more closely to east and west than directly to south (which brings a high surge in power). So most embankments and cuttings should have one side that will be of some use for solar panels. Placing solar panels in these positions has seemed obvious to me for a long time, so I'm glad someone is finally starting to look seriously into it.

Siting PVs on railway land and feeding into the grid is surely more sensible than using them directly to power trains.

Solar can (and on some days of the year does) generate really significant amounts of power.  Like 5 to 10% of total UK consumption on a sunny day and for relatively small levels of capital investment.  Not to be sniffed at all.

BUT, and there is always a BUT..

On some days the power generated is virtually nothing.  The intermittent nature of solar power is what is holding it back.  I don't see how this problem is lessened by putting solar electricity into OLE rather than feeding it into the grid helps solve this problem.   If NR starts taking solar electricity then it needs to have other sources in reserve as back up.  This is fine but they will have to pay for the ability to draw on those back up sources. 

Electric traction power demands may be locally intermittent, but on a national scale it is very predicable (in that you can predict the number of electric trains running each day by looking at the timetable).  It makes more sense for NR to buy its power from a source which is good at generating a predicable base load and in fact this is largely what they do with much traction power coming from nuclear power stations. 

The best customer for solar electricity is an industry which can cope with getting intermediate power at unpredictable times.  I am not sure which industries fit that bill?  Maybe the something like a clay dry were it doesn't really matter if the clay slurry is dried this week or next month and where they can wait until a sunny day for the cheap power.  Or maybe an industry that has an alternative power source available too.

The real solution to making solar work is of course better storage.  Or putting the solar panels somewhere (like the desert) where sunshine is much brighter and much more predicable. 
   

You also forget to mention the amount of space that solar 'farms' occupy. It seems to be a growing trend in the UK to replace decent quality agricultural land with banks of photo-voltaic cells...

...I'd also add that solar becomes somewhat more attractive when you have a national grid (or better still an upgraded or smart grid) because at least then you can shift power round the country and match demand from a non-generating (ie cloudy) region with supply from a generating (ie sunny) region.  More local arrangements where generator and consumer are matched as with this proposal run against that advantage.

I have invested in PV (via Bath and West Community Energy and their partner organisations) and can tell you that it is usually poor quality agricultural land which is used. It is also not completely taken out of farming use.  Very often there is grazing (sheep) between the panels.  There is also the opportunity to manage the land as a nature reserve.  The panels are certainly better for wildlife than an intensively farmed field of crop.

But of course, nothing beats putting the panels on unused roofs.  Changes in government subsidies make that less attractive these days though. 

I can think of a number that have popped up around Somerset and the vale of Glamorgan over the past few years - little of those county's agricultural land could be classed as poor quality - the bits I know of that are covered over were formerly dairy grazing or cereal production put over entirely to solar 'farming'.

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.

Agree with unused roofs, particularly in built up areas where you could have a sizeable array installed in a relatively small and discrete area.

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.

Grazing of sheep is almost a requirement since otherwise plant growth will in few years obstruct the modules. Other types of livestock find less favour, poultry crap on the modules, goats eat the cables, pigs root and dig up buried cables, and cattle damage the structures by rubbing against them.
Sheep do well in fields shared with PV modules since they can shelter under them.

Crops can be grown by hand cultivation but this is uncommon.

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.

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.



 

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. 

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.

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.

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 (https://www.onstride.co.uk/blog/how-many-solar-panels-would-power-every-uk-household/) 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 (http://www.independent.co.uk/news/science/gas-siberia-underground-earth-bounce-climate-change-siberia-global-warming-a7153486.html)}

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?

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

From the letters page in the Melksham News.


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.

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.

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

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 (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.