PV film generating carbon positivity
Network Rail’s Lead Development Manager (Southern Region) ANDREW WOOD tells TOM ALLETT about the initiative that has led to Denmark Hill station achieving a UK ‘green’ first
Denmark Hill is not among London’s most celebrated stations, but a recently completed project at the site has delivered a railway ‘first’ that could ultimately bring environmental gains across the UK.
As part of a wider station redevelopment programme, Network Rail has introduced a new type of solar power technology - a photovoltaic (PV) roof-covering film that has made elements of the station’s infrastructure (new station entrance, new platform canopies and rain cover for the accessible ramp) carbon positive (from an operational perspective).
In other words, they produce more electricity than they use over the course of year, with any surplus supplied to the National Grid. It is the first example of a carbon positive development at a UK railway station and possibly all of Europe.
Andrew Wood, Lead Development Manager for Network Rail’s Southern Region, tells RAIL: “The wider redevelopment project began in 2019, before the pandemic. Passenger numbers had tripled over the course of the previous decade, resulting in an urgent need to deal with peak-time overcrowding at the station.
“The existing station entrance/exit on Champion Park [at the south-west corner of the station] was becoming very congested and passengers often needed to queue for the entirety of the walking route from the accessible bridge to leave the station.”
NR estimates that customers were queuing for up to seven minutes to exit the station.
Wood continues: “If there was serious disruption to services, then we would often have a situation where people were queuing up outside the station encroaching on the very busy Champion Park road. This raised safety concerns, so we needed to do something quickly to relieve the congestion by delivering a new entrance/exit. The solar element became part of that solution.
“We took a new approach and decided to work through one of GTR’s contractors, INVVU Construction, to attempt to design and deliver the project faster. An intervention of this type can often take four to five years from start to finish, but we delivered this in 32 months using this new approach.
“Around two years ago, Network Rail Southern Region introduced its new ‘Southern Sustainability Plan’ with a vision of becoming cleaner, greener and socially more responsible. This includes a focus on reducing energy, carbon and air pollution, particularly in new development.
“So, working with the contractor, we were able to identify a new innovative type of PV covering to be used. It would generate enough electricity to power the new development.”
The new entrance/exit and rain cover that would host the PV film was built upon available space alongside Windsor Walk, on the opposite side of the station to the original congestion problem. In addition, new canopies to Platforms 2 and 3 and a widened Platform 4
They have a 40-year design life, but if any section is damaged, you can simply pull the layer off and stick its replacement down with adhesive and plug it in.
Andrew Wood, Lead Development Manager, Network Rail
would host the new PV covering
When building the new platform canopies, the construction team had the advantage of being able to build the canopy at ground level (in the road immediately outside the station), and simultaneously add the PV film covering in strips before lifting them into place. This was much easier than having to install them in situ on top afterwards.
Installation of the platform canopies was carried out over Christmas 2020.
NR had already completed a number of PV installation projects elsewhere, including at London King’s Cross (if you look up during your next visit, you should see it in the glass roof).
However, Wood explains: “One of the advantages of using the new PV film is that traditional glass PV panels tend to need to be angled to face the sun, which means they can sometimes be obtrusive. The glass panels are also far less resilient than the new PV film.
“At Blackfriars Bridge, we have a lot of glass PV covering the station roof. There’s a recurring problem caused by birds picking up stones thinking they are eggs, but when they realise they are not eggs, they drop them. Some have fallen on the glass panels and broken them, so they had to be replaced.
“With the PV film, we don’t have this problem. They have a 40-year design life, but if any section becomes damaged, you can simply pull the layer off and stick its replacement down with adhesive and plug it in.”
The PV film is manufactured in Japan and sourced by a UK firm. It is neither heavy nor bulky - it is only 3mm thick and weighs in at just 3kg per m2. Nor does it require any extra roof infrastructure to attach it to, as would likely be the case with glass panels.
“You can roll it up to carry it,” says Wood, adding: “It is a type of ‘plug and play’ item. The film in this instance is glued to the roof.
“The PV strips are positioned on the canopy itself. They are not obtrusive, you don’t have to angle them towards the sun as you would with traditional glass panels, and they don’t even need direct sunlight to work, just light.”
Wood notes that the PV film produces a lot more electricity than the new development needs, so on bright and sunny summer days, the power generated is enough to run the whole station and still put some electricity into the national grid. (Unless Denmark Hill’s three lifts are in use, as they devour a lot of electricity when in use. The lifts were not part of the recent redevelopment, having been introduced about five years ago.)
The electricity generated does not go into batteries, it goes straight into use. The amount of electricity produced is sufficient to power information display or CCTV screens, but not enough to power a train… yet, although Wood can envisage a time when it could be possible to acquire a field, fill it with PV panels or film, and then use that electricity to charge a battery that could give you a solar-powered train.
In February, storms battered Britain’s rail network. How resilient is the PV film?
Wood replies: “If a large branch were to fall on the roof and damage the PV film, then even if we could not see the damage, we can detect problems through monitoring the electricity levels produced.
“The installation was built in two halves. The first covers Platforms 2, 3 and 4, while the second covers the station building itself. Through monitoring the output, we can identify any system failures.”
He describes how the roof surfaces have walkways across them, to enable easy access for the routine inspections that are required every six months.
The PV film is also self-cleaning. And as each section is positioned on a slant, water just runs off it. Any work required is carried out by Network Rail Building Maintenance staff.
When Denmark Hill’s new facilities were officially unveiled last September, there were still some teething troubles with a display board that shows how much electricity is being produced in real time.
This is now fully operational and uses a 3G WiFi connection to the inverters to calculate the amount of electricity being produced. Today’s visitors can see the facility’s
generating performance on the display screen.
Looking ahead, NR is hoping to introduce similar technology at Peckham Rye station, located just one stop along the South London Line from Denmark Hill. NR is working on a much larger project at Peckham Rye, and one element of that will hopefully be introducing PV roof coverings.
“One of the reasons the PV covering works at the likes of Denmark Hill and Peckham Rye is because they both have large roof areas that can be covered,” says Wood.
“Interestingly, Southern’s Sustainability Plan encouraged the project to look at PV and to maximise the covering’s performance, we widened the canopy on Platform 4 to cover a greater area.
“This led to the area above the accessible ramp being covered over for the first time… why should people with restricted mobility get wet while accessing the station when it’s raining?
“So, while creating a wider roof area to catch more light, the station received another bonus through providing greater shelter from inclement weather.
“It’s also worth noting that the accessible ramp was fabricated offsite and lifted into place in segments, thereby greatly reducing the number of truck journeys that would have been required if the many materials involved had all needed to be taken to the station by road.”
Denmark Hill is Grade 2-listed, so any alterations need Listed Building Consent.
“We had to prove that we weren’t detrimentally affecting the sightlines at the station,” Wood explains.
“It really makes sense to introduce this type of PV when you are building new structures, and the installation work can take place offsite.
“While it is possible to attach the product to existing structures, that could be more problematic. The existing surfaces could be dirty, so the adhesive won’t hold. These are problems that could be exacerbated by working at height - and they can be avoided when you are building on the ground.”
Being the first to use any new technology operationally can often mean that you learn all the lessons that assist the users who follow. However, Wood says there was “surprisingly little” that needed to be ‘ironed out’.
He explains: “The array you can see at Denmark Hill has the PV covering connected by cabling to several inverter cabinets. If you go to Denmark Hill, you will see that there is an inverter cabinet next to the main station building and two others under the canopies on to the platforms, then more cabling from there to the electricity meter.
“The hardest thing for us wasn’t the installation itself, it was the legal agreements
that we needed to make with the electricity supplier - called a G99 agreement - and a Power Purchase Agreement with the train operator, Govia Thameslink Railway, owing to this being the first time we have done such a thing.
“The benefit for GTR is that it buys electricity from Network Rail at a discounted rate (not including distribution costs) compared with the normal commercial rate.
“So, a win for Denmark Hill, Network Rail and the government in terms of energy use and sustainability credentials, and a win for GTR because it is benefiting from cheaper energy.”
Wood believes that the dramatic rises in UK energy prices means that the PV-supplied electricity has the potential to create further savings for the railway..
He tells RAIL: “We’ve had enquiries from Europe, Chile, and from within our own business where we may use similar technologies elsewhere. I’ve put my colleagues in touch with the supplier.”
Other green additions to Denmark Hill include an 85-space bicycle park created on a piece of scrubland. It has yet to reach its full potential, but it is still a relatively new facility, and the two adjacent hospitals (Kings College and Maudsley) are encouraging staff and visitors to use it when possible.
“We’ve used a lot of sustainable materials in the construction of the station,” says Wood.
“When widening the platform, we put in a King Post wall. Rather than take the KP wall out while we were building a retaining wall, we just left it in place because it provides integral strength and it meant that we did not have to dispose of it and take it away from the site, saving the countless truck movements that would have been involved and the carbon emissions that go with them.
“We also used polystyrene blocks as infill in place of virgin material, which is a better solution as it used recycled materials.
“We also recycled as many bricks as possible in the listed wall on Windsor Walk, and used 75% recycled steel for the metalworks.
“All lighting is LED technology to reduce the power requirement, and fresh rainwater is attenuated and can provide water for some of the station’s plants.”
Despite the early success of Denmark Hill’s new PV film and its expected 40-year working life, the manufacturer is already working on improved PV technology that is even more efficient at producing electricity. NR hopes to use this in the proposed transformational station upgrade at Peckham Rye.
Wood explains: “At Peckham, we are proposing to install PV on the proposed rear atrium roof and platform 4 access building. This will help provide power for the new lifts that are a central component of that design.”
On March 7, Network Rail submitted its application for planning permission for the upgrade of Peckham Rye station, which is now the busiest interchange station in the UK without Access for All.
All being well, that means approaching the Government this summer for the required funding to deliver the scheme.