The Anonymous Widower

Thoughts On Batteries

As a Control Engineer, I have a lot of thoughts about making the World a more efficient and safer place.

As a simple example of what Control Engineering is all about, do two hundred mile drives in your car.

  • One is a route you don’t know.
  • The other is one you know very well.

In both journeys drive as carefully as you can to try to do both journeys using the minimum amount of fuel.

Inevitably, in most cases, you will do the second route on less fuel, because you will adjust speed and anticipate possible problems from previous knowledge.

A well-designed control system for a self-driving car should be able to outperform a manually-driver car because it has better knowledge.

Control Engineering is all about taking all the knowledge you can, processing it in a control system or computer and doing the job to the ultimate best.

Batteries Will Get A Higher Charge Density Per Cubic Metre And Per Dollar

There are a lot of clever engineers and scientists out there in countries like China, Germany, Japan, Korea and the USA,  working on battery technology and increasing the charge density will be one of their key objectives.

The smaller and more affordable a battery becomes, the more will be sold.

With several large companies out there investing heavily in the production of batteries, there can only be one ultimate wuner – the individual, company, government or organisation, who eventually pays for the product in which the battery is installed.

So How Will Control Engineering Be Involved?

In some ways, it already is!

Control Engineering In Personal Devices

In your smart-phone, laptop or personal device, you can set parameters to get the maximum minutes for one charge of the battery.

You are effectively, tweaking the device and the battery control system is doing the best it can with the lkimited energy resources of the battery of the device.

Control Engineering In Transport Systems

One of the problems with personal devices, is they need to be plugged in to be charged.

But as transport systems are larger and often have access to other forms of energy, recharging is not such a problem.

  • Batteries in hybrid vehicles can be charged by an onboard engine.
  • Some battery and hybrid cars can be plugged into the mains.
  • Braking energy can be recovered and used to charge the battery.
  • Trains, trams and trolley-buses can use overhead wires or third-rail systems to charge the battery.

It is the major task of the vehicle’s control system to balance the needs of traction and the onboard systems, by pulling in energy from various sources.

A Typical Hybrid Bus

A hybrid bus like a Routemaster, has a very different  transmission system to your bog-standard diesel bus.

  • It is actually driven by a Siemens ELFA2[4]electric traction motor.
  • Braking is regenerative.
  • The Cummins diesel engine is mounted under the rear stairs.
  • The 75 KwH battery is mounted under the front stairs.

Effectively, the diesel engine tops up the battery to a high enough level and the wheels are driven from the battery.

The control system manages the energy starting and stopping the engine as required.

The Ultimate Hybrid Bus

In the ultimate hybrid bus, the control system would know lots of other factors, including.

  • The route.
  • The actual and expected number of passengers.
  • The actual and expected weather.
  • Whether Arsenal were plying at home, or there was a demonstration by taxi-drivers.

So it would manage the power in the battery according to the predicted future energy requirements.

What would that do for fuel economy and the reduction of pollution?

But how could the efficiency of the bus be improved further?

  • A lighter battery with the same capacity.
  • A lighter diesel-engine, traction motor and other components.
  • A much improved control system.

As with most things, reducing weight is probably the most important. But don’t underestimate, what can be achieved with the ultimate control system.

It all points to my belief, that we should probably leave the development of batteries to the big boys and concentrate on the applications.

Hybrid Electric Trucks

Hybrid electric trucks are on the way.

Hybrid Trains And Trams

I think the mathematics point to hybrid trains and trams being one of the better applications of batteries in transport.

A typical four-car electric multiple unit like a new Class 710 train, weighs about 130 tonnes or 138 tonnes with passengers. Going at a line speed of 100 kph, it has a kinetic energy of 15 KwH. So this amount of kinetic energy would be well within the scope of a 75 KwH battery from a Routemaster bus.

I think that the typical four-car electric multiple unit can easily be fitted with a battery to handle the braking for the train.

The physics of steel-wheel-on-steel-rail are also very efficient, as Robert Stephenson, if not his father, would have known.

But with trains, there are several ways the batteries can be charged.

  • From 25 KVAC overhead power.
  • From 750 VDC third-rail power.
  • By recovering braking energy.
  • From a small diesel generator.

A good control system manages the energy and also raises and lowers the pantograph as needed.

Conclusions

Design and manufacturing competition from the big players in batteries, will bring the price down and increase the amount of energy that can be stored in a battery of a particular size.

But the key to making the most out of a battery is to have a well-designed control system to manage the energy.

 

 

January 22, 2017 - Posted by | Travel | , ,

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