Heat reflective paint

[modernrail]

I read a few years ago a theory that quite a lot of heat in the underground is seasonal and could be mitigated through the use of heat reflective paint so that the trains do not heat up as much in the above ground sections and then transfer that heat underground.

I have since seen stories on this paint being used successfully in other applications.

Has a trial ever been carried out on the Underground. It seems like a very logical and low cost approach to trial and measure, with potentially significant implications.

 

[Dstock7080]

Not heat reflective paint but the colour of train roofs has changed over the years, from dirty matt-black of the 1950s, gloss-black of 1960s, with experiments undertaken on C Stock using white roofs, initial C77s having unpainted aluminium to the adoption of light grey as the perceived better colour.

 

[modernrail]

Thanks Dstock. Do you know why have they not volunteered to trial the new paint tech? I work on thermal energy/sustainability and have actually worked on some of the plans to pull heat from the tube. One of the important factors on that is future heat levels in the tunnels. New trains should reduce that to some extent which needs to be factored in but I have also been considering what else might. It is in that thinking that I came across work on these paints. The Australian navy is already using them to good effect.

Considering the massive issue this is, and the potential for there to be an extremely low cost solution out there, I am really confused as to why TfL has not offered itself up as a major testing ground for heat reflective paints. It might make the project I am working on less attractive in terms of available heat but is still 100% the right thing for the engineers to look at for the Underground system.

It makes total sense to me that trains are picking up lots of heat in summer above ground, this heat is then been carried into the tunnels with the heat being drawn from the heated up trains into the tunnels and into the wider system.

A train in an above ground depot probably radiates most of its heat back out overnight and so starts the morning cool in all but hot nights. Where that train runs underground in the middle section of its line throughout the day it probably gets loads of that heat pulled out of it underground through the day with the train effectively acting as a radiator warming any cooler air it passes through in the tunnels. So the trains might basically be acting as a free and very unwanted heat transfer medium. This might be especially so with the particular features of our system with quite significant above ground sections at each end of all but the Victoria Line and then a nice ridiculously tight set of metal tunnels with clay behind them in the middle. Even better, the deep level lines are designed with trains acting as a massive series of pistons to move air around making sure that hot air ‘infects’ all parts of the system. This means that even lines without above ground sections probably end up equalising to a system temp, hence the Victoria line eventually heats up through a hot day as well. I am not sure I can think of another system that has this perfect storm for heat transfer?

I would also be looking at this for purely overground trains as it could be a good way of reducing ac load and maybe improving comfort on legacy non-ac stock to extend its life.

However, for the underground it seems to offer a serious part solution to an otherwise really difficult problem that is very very expensive to fix with any sort of underground infrastructure.

Here is an interesting article to one example of the tech. https://www.coolingpost.com/world-news/reflective-paint-confirmed-as-worlds-whitest/

It should also be remembered that paint has already proven itself to be an amusingly low cost solution to some classic UK infrastructure problems, with this being my favourite example of going ‘oh **** how much money would we have saved it we had thought of that a while ago’ for ages…

Network Rail save £40m thanks to revolutionary electric resistant paint | Rail Technology Magazine

In a revolutionary world-first, electric resistant paint combined with voltage-controlled clearance (VCC) has helped make a Victo

www.railtechnologymagazine.com

£40 million pound saving!!!!!

 

[Gerald Fiennes]

Well, the case study at Cardiff is a well known one. It's the surge arrester that's doing the hard yards here, a kind of fuse. The paint is to increase the insulation and protect against flashovers. It is also pretty high-tech.

 

[Nym]

Thanks Dstock. Do you know why have they not volunteered to trial the new paint tech? I work on thermal energy/sustainability and have actually worked on some of the plans to pull heat from the tube. One of the important factors on that is future heat levels in the tunnels. New trains should reduce that to some extent which needs to be factored in but I have also been considering what else might. It is in that thinking that I came across work on these paints. The Australian navy is already using them to good effect.

Considering the massive issue this is, and the potential for there to be an extremely low cost solution out there, I am really confused as to why TfL has not offered itself up as a major testing ground for heat reflective paints. It might make the project I am working on less attractive in terms of available heat but is still 100% the right thing for the engineers to look at for the Underground system.

It makes total sense to me that trains are picking up lots of heat in summer above ground, this heat is then been carried into the tunnels with the heat being drawn from the heated up trains into the tunnels and into the wider system.

A train in an above ground depot probably radiates most of its heat back out overnight and so starts the morning cool in all but hot nights. Where that train runs underground in the middle section of its line throughout the day it probably gets loads of that heat pulled out of it underground through the day with the train effectively acting as a radiator warming any cooler air it passes through in the tunnels. So the trains might basically be acting as a free and very unwanted heat transfer medium. This might be especially so with the particular features of our system with quite significant above ground sections at each end of all but the Victoria Line and then a nice ridiculously tight set of metal tunnels with clay behind them in the middle. Even better, the deep level lines are designed with trains acting as a massive series of pistons to move air around making sure that hot air ‘infects’ all parts of the system. This means that even lines without above ground sections probably end up equalising to a system temp, hence the Victoria line eventually heats up through a hot day as well. I am not sure I can think of another system that has this perfect storm for heat transfer?

I would also be looking at this for purely overground trains as it could be a good way of reducing ac load and maybe improving comfort on legacy non-ac stock to extend its life.

However, for the underground it seems to offer a serious part solution to an otherwise really difficult problem that is very very expensive to fix with any sort of underground infrastructure.

Here is an interesting article to one example of the tech. https://www.coolingpost.com/world-news/reflective-paint-confirmed-as-worlds-whitest/

It should also be remembered that paint has already proven itself to be an amusingly low cost solution to some classic UK infrastructure problems, with this being my favourite example of going ‘oh **** how much money would we have saved it we had thought of that a while ago’ for ages…

Network Rail save £40m thanks to revolutionary electric resistant paint | Rail Technology Magazine

In a revolutionary world-first, electric resistant paint combined with voltage-controlled clearance (VCC) has helped make a Victo

www.railtechnologymagazine.com

£40 million pound saving!!!!!

The problem with using paint and VCC systems like this for OLE clearance, is that someone then needs to maintain it, that £40m will soon end up spent with the route maintenance thinking, "Oh, why didn't we just do this properly" 10 years later. Especially with how difficult it is to get hold of EN50317 OLE Test Trains at the moment.