The Anonymous Widower

Riding Sunbeams Deploys Solar Array

The title of this post is the same as that of this article on Railway Gazette.

These are the introductory paragraphs.

Riding Sunbeams Ltd has installed a 30 kWp solar test unit with around 100 panels near Aldershot which is directly supplying electricity to power signalling and lighting on Network Rail’s Wessex Route.

This will enable data to be gathered to assess how much larger solar arrays could be used to power trains.

Note that kWp is peak kW. On a very sunny day, 30 kW is the highest power level that will be supplied.

This page on the Energy Saving Trust is entitled Costs and Saving and this is said.about solar generation in the South of England.

A 4kWp system in the south of England can generate around 4,200 kilowatt hours of electricity a year – that’s the same amount of electricity as it takes to turn the London Eye 56 times. It will save around 1.6 tonnes of carbon dioxide every year.

For comparison, they say this about solar generation in Scotland.

A 4kWp system in Scotland can generate about 3,400 kilowatt hours of electricity a year – that’s the same amount of electricity as it takes to turn the Falkirk Wheel 2,200 times. It will save approximately 1.3 tonnes of carbon dioxide every year.

I’d be interested to know, the two locations, where they measured the sunlight.

It was a lovely sunny day recently, when I passed through Aldershot station, so I’ll use the Southern England figures.

  • Uprating the Energy Saving Trust figures by 30/4 gives a yearly output of 31,500 kWh,
  • The daily output is 86.3 kWh.
  • The hourly output based on a 0600-2200 sixteen hour day is 5.4 kWh

There would probably be a battery to make the most of the electricity generated.

Powering Feeder Stations For Third-Rail Electrification

As the Railway Gazette article says, the trial installation at Aldershot station will be used to power signalling and the station, which will then give figures to assess how trains can be powered.

In the September 2017 Edition of Modern Railways, there is an article entitled Wires Through The Weald, which discusses electrification of the Uckfield Branch in Sussex, as proposed by Chris Gibb. This is an extract.

He (Chris Gibb) says the largest single item cost is connection to the National Grid, and a third-rail system would require feeder stations every two or three miles, whereas overhead wires may require only a single feeder station for the entire Uckfield Branch.

It would appear that 750 VDC rail-based direct current electrification needs many more feeder stations, than 25 KVAC overhead electrification.

Could a solar system from Riding Sunbeams supply power in the following situations?

  • Places where there was space for a solar array.
  • Remote locations, where a connection to the grid is difficult.
  • Places, where the power supply needed a bit of a boost.

How large would an individual solar feeder station need to be?

Consider a feeder station on a rail line with these characteristics.

  • Third-rail electrification
  • Four-car trains
  • Each train uses three kWh per vehicle mile.
  • Two trains per hour (tph) in both directions.
  • Electrification sections are three miles long.
  • Trains run from six in the morning to ten at night.
  • Trains pass at speeds of up to 100 mph.

The hourly electricity need for each section would be 144 kWh or 2304 kWh per day and 841 MWh for the whole year.

The Energy Saving Trust says this.

A 4kWp system in the south of England can generate around 4,200 kilowatt hours of electricity a year.

Using these figures says that a solar array of 800 MWp will be needed to provide the power for one feeder station.

Consider.

  • The largest solar array in the UK is Shotwick Solar Farm, which has a capacity of 72 MWp.
  • Shotwick covers 730 acres.

Am I right to question if that enough electricity to create a feeder station to power trains, can be produced reliably from a solar array and a battery?

I’d love to have the electricity usage and bill for one of Network Rail’s typical third-rail feeder stations. Not that I’d want to pay it!

How Would Station Stops Be Handled?

When a modern electrical multiple unit stops in a station, there is a three-stage process.

  • The train decelerates, hopefully using regenerative braking, where the braking energy is returned through the electrification to hopefully power nearby trains.
  • The train waits in the station for a minute or so, using power for air-conditioning and other hotel functions.
  • The train accelerates away using track power.

Would a Riding Sunbeams system provide enough capacity to accelerate the train away?

In What Is The Kinetic Energy Of A Class 710 Train?, I calculated the kinetic energy of a very full Class 710 train, which is just about as modern and probably efficient, as you can get.

These were my results.

  • 50 mph – 15.3 kWh
  • 60 mph – 22.1 kWh
  • 90 mph – 49.4 kWh – Operating speed of a Crossrail Class 345 train.
  • 100 mph – 61.3 kWh – Operating speed of many electric multiple units.

These kinetic energy values are low enough to make it possible that a modern electric multiple unit can run using on-board batteries.

  • Regenerative braking would be captured in the batteries.
  • Hotel power in the station can be provided by batteries.
  • Batteries can cruise the train through sections of line without electrification or with a poor electrical supply.

Suppose there is a twenty mile gap between two stations; A and B, where trains cruise at 90 mph.

  • The train arrives at station A, with a battery that has been charged on previous parts of the journey from the electrification.
  • Regenerative braking energy will be stored in the battery on braking.
  • Acceleration to 90 mph will need 49.4 kWh of electricity from the battery.
  • Using my 3 kWh per vehicle mile figure, going from A to B, will need 4 cars * 20 miles * 3 = 240 kWh of electricity.

It looks like a battery with a capacity of 300 kWh would handle this situation

Could this be fitted into a four-car train, like an Aventra?

In this article in Global Rail News from 2011, which is entitled Bombardier’s AVENTRA – A new era in train performance, gives some details of the Aventra’s electrical systems. This is said.

AVENTRA can run on both 25kV AC and 750V DC power – the high-efficiency transformers being another area where a heavier component was chosen because, in the long term, it’s cheaper to run. Pairs of cars will run off a common power bus with a converter on one car powering both. The other car can be fitted with power storage devices such as super-capacitors or Lithium-ion batteries if required. The intention is that every car will be powered although trailer cars will be available.

Unlike today’s commuter trains, AVENTRA will also shut down fully at night. It will be ‘woken up’ by remote control before the driver arrives for the first shift

This was published over eight years ago, so I suspect Bombardier have refined the concept.

If 424 kWh can be fitted under the floor of a two-car Class 230 train, I’m sure in a train designed for energy storage at least 500 kWh or maybe as high as 1000 kWh could be fitted to a four-car Aventra.

A 500 kWh battery would give a battery range of just under forty miles, whilst a 1000 kWh battery would give a ninety-five mile range.

Obviously, the battery would need to be charged, but in many cases the range would take the train between two existing electrified lines. Think Ipswich -Cambridge, Newcastle-Carlisle, the Fife Circle Line, the Uckfield Branch and Ashford-Hastings!

Conclusion

Riding Sunbeams may be suitable for providing local power for signalling and stations, but batteries on trains looks like it could be a better way of powering trains.

September 8, 2019 - Posted by | Transport | , , , , ,

No comments yet.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.