Thursday, 19 November 2015

The lost world of electric powered transport

There's a much loved fantasy genre, Steampunk, where steam power never lost its preeminence as the dominant technology. But, surprisingly, there's a real alternate reality where electrical vehicles dominate.

In 1900 one of the worlds great cities, New York, was serviced with electric powered taxi cabs, vehicle charging points and battery exchange facilities. In 1908 an electric vehicle was driven on the dirt roads of the mid western United States. From Lincoln Nebraska nearly 1800 miles to New York. With many of the stages between recharges over 100 miles in distance. Fritchle

Electric powered mass transport, trams, followed the electrification of cities. This started in the 1880s. City electrification started with electric lighting but that meant demand was primarily in the mornings and evenings. The power companies sought a reason to sell power in the daylight hours so their plant could be kept running. Electric trams were developed in Germany and they provided the answer.  And what an improvement they were! Previously cities were dominated by the exhaust pollution of horses! The smell of horse shit was all pervading and the clean, quiet and reliable electric trams provided a welcome alternative. Electric_trams

In 1911 there was a railway line from Seattle in the west to Chicago. At the time the only technology capable of handling  the gradients of the Rocky Mountains were electric powered trains. And the Rocky Mountains themselves provided hydroelectric power  and copper mines to wire the railways.

This was a world where Thomas Edison and Henry Ford planned a mass market electric vehicle and where a transcontinental electric railway looked set to connect the North American east and west coast.

Science fiction? Not a bit of it. This was our world, up to 1914. It is described in Edwin Black's book. Internal_combustion_Black In this fascinating book Black promotes the thesis that, following the discovery of oil in Texas, the USA abruptly changed direction towards hydrocarbon powered vehicles. The tram tracks were ripped up and replaced by petrol fuelled busses and these were eventually largely abandoned to private cars. (Chrissie Hynde in her bio Reckless recalls how, in the 1950s, whole subdivisions of lovely residential homes were torn down to build freeways through her hometown of Akron Ohio.)

The USA and Europe became addicted to oil and has gone to further and ever more extreme lengths to service that addiction. Black recounts a history where  control of the fuel supply, whatever it was, has been a fundamental aspect of life. First the timber supply was controlled by the monasteries and then by an aristocracy who set supply levels and prices, this from the 10th century. Then coal came into use (see Hostmen_of_Newcastle_upon_Tyne) and finally oil. The periodic supply shortages generate big profits.  And even after a big scare the suckers keep coming back for more. Since the 1973 oil crises we've had ever larger, less economical private vehicles introduced. 

But what if the developed world had not gone the oil route  in the 20th century? The electrical technology of the early 20th century did offer a viable alternative. The fundamental characteristics of electrical machines offer some big advantages. An electric motor is a very simple machine.  An electrical current is produced whenever a loop of wire is moved through a magnetic field. And any electric motor is also, simultaneously, a generator.

Apply power to an electric motor and as the current flows it will turn. And as it turns it also starts to generate electricity in the opposite direction to the electrical current supplied. This is what is known as BEMF, Back ElectroMotive Force. When starting up the motor doesn't generate much BEMF because it is turning slowly. So the motor draws a lot of current from its supply. The high current flows into it and produces lots of power to get the thing turning. Very useful in a heavy railway train or tram and in a car it can give a ferocious acceleration.

As the motor picks up speed more BEMF is produced and so the current drawn from the supply is reduced. Eventually an equilibrium speed is reached where the supplied current almost equals the BEMF.  There has to be a little extra current to overcome turning resistance and aerodynamic drag. It is this characteristic that makes the electric motor so effective. It's also so much simpler than an internal combustion engine with its pistons shuffling up and down, valves opening and closing and various liquids being pumped around.

When it's time to slow down again the input current can simply be removed and the motor will start to slow. But the machine can be slowed more rapidly and electric current, the BEMF, fed back into the battery. This is how hybrid cars such as the Prius achieve economy. In stop start driving the Prius is more economical because when slowing energy is recovered to the battery. This is reused when the car next accelerates. Electric cars such as the Nissan Leaf and the Tesla also use this technique. It is usually referred to as regenerative braking. The Fritchle car in the top illustration used regenerative braking - Fritchle called it electrical braking.

With combustion powered vehicles the energy of braking is simply wasted. In fact in high performance cars disposing of the heat caused by braking can be a major issue. In fact, in combustion engined vehicles keeping all the various fluids: cooling water, lubricating oil, hydraulic brake fluid, at the right temperatures and pressures places a huge burden on the design. Moreover, a gearbox must be used just to generate sufficient torque to even get the car moving. The internal combustion engine is only really powerful within a small speed range, usually about 3000 revolutions per minute.

That such a limited propulsion system as the gasoline powered car should come to dominate 20th century propulsion, especially in competition with the quiet and elegant electric vehicles, is a long story and that is the story told in Edward Black's book.

But it's fascinating to speculate on what an electrically powered 20th century might have been like.
The character of aviation would have been completely different. Without the petrol car market Rolls Royce would not have made the Merlin piston engine. Whole fleets of warplanes, the Spitfires, Hurricanes, Mustangs and Lancasters would never have existed.

Battery powered planes? Well they exist now.  Airbus_E-Fan  It took the needs of early 21st century laptop and phone users to mobilise the development of new battery chemistry.  But in that alternate universe we might have had electrical aircraft engaged in dog fights in 1940.

And, it need hardly be said, the current position of the Middle East and its position on the global scene would have been immensely less significant.

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