Solar-powered trains are closer to reality than we might think

[whole diary]

[grahame]

From The Guardian

Use of solar panels by the side of tracks to provide power to electric trains could make sense given match-up between peak generation and demand

How can we connect solar photovoltaics (PV) directly to railways to power electric trains? That’s the question my charity 10:10 and researchers at Imperial College’s Energy Futures Lab are trying to answer.

Electric trains are by far the best long distance transport mode when it comes to carbon emissions – at least when their electricity comes from renewable sources like solar or wind.

But the UK^▸ (United Kingdom)’s ageing power network poses a significant challenges to any bid to decarbonise road and rail that relies on the grid. There are now swathes of the British countryside where it is impossible to plug in any new solar, wind or hydropower without being hit with a whopping bill for the full costs of local network reinforcement.

Faced with this constraint, and squeezed by government subsidy cuts, UK solar developers have started to focus on ways to generate power directly for consumption, rather than exporting it to the grid. With the right customers, solar developers can offer lower tariffs than the grid, while still earning more for their power than they would get from exporting it.

[grahame]

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.

[ChrisB]

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

[grahame]

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.

[broadgage]

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

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^▸ (in my humble opinion) 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.

[Noggin]

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.

[froome]

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.

[Bmblbzzz]

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

[Tim]

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

Solar can (and on some days of the year does) generate really significant amounts of power.  Like 5 to 10% of total UK^▸ (United Kingdom) 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^▸ (Overhead Line Equipment, more often "OHLE") rather than feeding it into the grid helps solve this problem.   If NR^» (Network Rail - home page) 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. 
   

[chrisr_75]

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

[Tim]

...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.

[Tim]

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

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. 

[chrisr_75]

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

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.

[Electric train]

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

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 have been involved in discussion group looking at the various feasible options, there are quite a few innovative proposals being put forward, some technically simple other complex; some with complex operational interfaces with third parties others less complex.

It is a serious piece of work that not only involves PV it also include energy storage and the part regen braking has to play.

[broadgage]

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.