History professor Kurt Möser knows them all: wood, rapeseed, steam, gas turbines, hot air, coal dust and solar drive systems for cars. An interview about the history of drive technologies and the lessons learned.
Interview with Kurt Möser, Professor of History at the Karlsruhe Institute of Technology (KIT)
The electric motor does not have to be invented from scratch. It has existed since 1881 – five years longer than the combustion engine. Hybrid drives also existed back in the 19th century. And that’s not all. There were drives with coal dust, wood or rapeseed as fuel, with fuel cells as energy stores, cars with steam and gas turbines and hot-air engines – even ones with jet or rocket propulsion and solar power. Experiments were even conducted with cosmic rays. An interview with Kurt Möser, Professor of History at the Karlsruhe Institute of Technology (KIT).
Professor Möser, today it is almost always a gasoline, diesel or electric motor at work beneath the hood of a car. That was not always the case. What other – perhaps curious or bizarre – developments in the area of drive systems have there been over the past 140 years?
Automotive history is highly irrational. Not all drive technologies that failed to thrive on the mass market were relegated to the trash heap. Some concepts, such as Wankel and solid fuel engines had noteworthy successes, but still failed to break through. Others, such as hybrid or hydrogen engines, were first mocked and now – decades after their invention – are on the upswing.
Why is that?
It depended, and still does today, not only on an ingenious spirit of invention and the engineering feats that follow on its heels. It also depends in large measure on the zeitgeist, on the society. In many cases political circumstances and requirements are crucial in deciding whether a drive technology can establish itself or even have a breakthrough. It’s a common thread that runs through 140 years of automotive manufacturing.
You’ll have to explain that. What do you mean by political circumstances?
Take the year 1906. At that time the German military decided which trucks would be subsidized for civilian purchase and operation. Due to war preparations, not only the range and speed, but even the H-shifter and the pedal distribution in the footwell were specified as preconditions for subsidies. The thinking was that soldiers in a possible war deployment could drive these trucks without any problem and would not have to get used to something new. The result was that many breweries procured subsidized gasoline trucks exactly according to these specifications, which then later did service in the war as well.
Are there other examples of politics influencing drive technologies?
Yes, in the Second World War. Because there was no more gasoline, they experimented with wood gasifiers, which had low output, and one got incredibly dirty. But that was the least of the problems. A more serious problem was that the amount of wood blocks needed for fuel could scarcely be transported. For the sake of comparison: two-and-a-half kilograms of wood corresponded to one liter of gasoline. So there always had to be a trailer to carry the “tank wood.” Naturally, that was not practicable.
So the military often determined developments?
The jet and rocket propulsion systems came from the military as well. Because Germany wasn’t allowed to build heavy artillery after World War I, they developed rockets. These were supposed to be adapted for cars, but they proved impractical for everyday use. The jet coming out of the rear was extremely dangerous and the vehicles were hard to control, hard to brake and responded sluggishly.
Okay, in the times before and during a war, it’s not so unusual that decisions were made on the basis of such considerations ...
... sure, but hold on. Interest-based decisions were and still are common in peacetime as well. Take the whole rapeseed oil production as an alternative fuel. That took place entirely in a period of peace. It was a hot topic until this organic, renewable fuel source was placed in competition with food. All of a sudden the question was: in the tank or on the plate? That’s the only reason there is now comparatively less interest in that topic.
Is the question of rapeseed oil over as far as you’re concerned?
Not quite. But for political reasons people are now looking around for other biofuel alternatives. There are efforts, for example, to make fuel out of algae. In bioreactors, algae is exposed to the sun and nutrients are added. The material harvested from that can be used to produce oil. Unfortunately, it is not yet economically viable.
Let’s talk about strange drive systems in history. What else was there that no longer exists today?
That topic could fill a whole evening! In the 1920s there were wind cars and propeller cars. But they accelerated extremely slowly. And they were also dangerous. No one wanted to sit in the propeller wash. In the 1930s, gasoline became scarce, so people experimented – beyond the aforementioned wood gasifiers – with coal dust as a fuel. Domestic brown coal could be used for that. But the output was too weak with this drive system as well, and it never gained mass appeal. After 1945 there was some hype around gas turbines. The idea, as in aircraft manufacturing, was to replace the combustion engine with a turbine. Rover built a gas turbine car in 1948 – which had severe drawbacks: the exhaust gases were extremely hot, the fuel consumption extremely high, and acceleration extremely hard to dose. In addition, the engines and the reduction gearboxes were much larger. In 1960, this idea was buried as well.
What remains fascinating is the technical creativity of the generations, the continuous radical rethinking.
In the 1970s, the hot-air engine found many proponents, in particular in the US. It’s an engine with external combustion. Its great advantage is that the heat source that sets the air in motion inside the engine, thereby moving a piston, is outside. It almost doesn’t matter what fuel is used to generate the heat. Unfortunately, this type of engine had major problems as well: its efficiency was far too low, which is why research was discontinued.
What came after the hot-air engine?
The big thing after that was the Wankel engine and hydrogen cars. The Wankel engine is a rotary engine invented by Felix Wankel. He wanted to avoid reciprocating technology. What is still remembered about it today is its extremely smooth operation. Also still remembered, however, is its gas-guzzling – and problems with wear. With the oil crisis of the 1970s, the Wankel engine met its end. Hydrogen-powered cars, by contrast, remain interesting today. They turn hydrogen and oxygen into electrical energy, and there are practically no exhaust gases. But they are expensive to produce. And there is still not a comprehensive supply network.
What motivates engineers today to develop alternative drive technologies?
Ever since the beginning of the development of drive technologies, the driving forces have always been the same: high range, low consumption, little to no emissions – and specifications derived from the criteria of environmental policy.
E-mobility also has the objective of greater range and higher battery capacity. What can we learn from history to apply to electric drive systems today?
A lot. That the history of technology is never linear. That it always has anarchic elements. That developments often branch off into completely unexpected tracks. But also, that a society has to clearly state what it wants, where its priorities lie. Today for example: Reduce CO₂ or particulate matter? Accept the extraction in developing countries of highly toxic raw materials – lithium, nickel and cobalt – as the price of emission-free electric drive systems? Establish a comprehensive charging power grid as quickly as possible? Shut down nuclear and coal-powered energy in the face of massive future increases in demand for electricity? There are dozens of such questions.
Germany is and has been the leader in automobile manufacturing for over 100 years. Does that race begin from scratch again with the advent of mass e-mobility?
Not quite. Of course mass e-mobility is a game-changer, but it also requires auto manufacturing experience. Germany is still the leader in that field. A Tesla, for example, is still not viable for the mass market today. Germany is simply good at perfecting the chassis, in the manufacture of mass-market-viable, high-quality bodies and much more. I am optimistic about the prospects of the domestic automotive industry. But I am pessimistic regarding the political framework. We are once again in the midst of a shift in priorities. But it’s not one among the customers, but rather in politics.
When you look back on the history of drive technologies, is the turn to e-mobility more evolution than revolution?
Yes, that’s exactly right. The e-mobility of the future again has a lot to do with political decisions. At the same time, the diesel engine, for example, remains a highly efficient engine, particularly under the current conditions. Society has to define where it wants to invest and where it might be prepared to dispense with something. And what will customers accept? For the automotive industry, the times always remain a bit opaque.
Alternative drive technologies: The history to date
Electric drive systems
Electric drive systems for cars do not have to be invented from scratch. As far back as 1881, Paris carriage builder Charles Jeantaud traveled a short distance in a carriage equipped with an electric drive. That was five years before the combustion engine that Karl Benz installed in his patent motorcar in 1886. The driving force behind electric vehicles around 1900 was taxi companies. They expanded from Philadelphia to cities on the US eastern seaboard and received their own charging grid in 1898.
Hybrid drives also existed back in the 19th century. In 1898 in Barcelona, artillery officer Emilio de la Cuadra outfitted a small vehicle prototype (voiturette) with a one-cylinder combustion engine (De Dion-Bouton motor) and an electric drive.
The battery had the familiar drawbacks: low energy density, high weight, expensive manufacture, short service life. In Vienna, Jakob Lohner built battery-electric passenger cars from 1900 onwards and gasoline-electric cars from 1901 onwards based on a design by Ferdinand Porsche, followed by commercial vehicles with an identical drive in 1903/04.
Wood as a drive technology experienced its heyday from 1939 to 1945, i.e. during the Second World War. The Reich authorities had ordered that trucks, omnibuses, tractors, passenger cars, rail vehicles and even ships on interior waterways be converted from liquid to solid fuels. In ddition to wood, charcoal, peat, brown coal and even anthracite could also combusted.
However, the amounts needed were enormous, which meant there always had to be a trailer attached to the vehicle just to carry the fuel. Moreover, the engine output was 20 to 40 percent lower because the heat value of wood gas compared to gasoline is roughly a third lower, and the rate of combustion is slower.
The oldest engines were gas engines for town gas. That’s because gases are more knock-proof, burn clean and, thanks to their higher heat values, achieve thermal efficiency levels equal or superior to liquid fuels. Luxembourger Jean Joseph Étienne Lenoir built combustion engines with coal gas as the fuel as far back as 1863. The engines of the time were not suitable for vehicles, though, because a gas vessel would have been prohibitively heavy and space-consuming.
It was only with the independence policy of the National Socialists in the Third Reich with their “domestic fuels” that gases re-emerged as a viable fuel for vehicles. Municipal operations in particular began shifting their busses, garbage trucks and street-cleaners to gas after 1934. The gas was compressed to 20 MPa as it is today, but was still carried in removable gas canisters in the vehicle. From 1935 onwards, permanent gas tanks were installed, as changing the gas canisters during operation was very cumbersome. In the three years that followed, a gas station network with 50 filling stations was built in the German Reich.
Through the end of the 1930s, scientists, in Germany in particular, continued to work on the fuel cell. After World War II, research and prototype construction of stationary energy generators shifted primarily to the US. There the machine manufacturer Allis-Chalmers launched what was probably the first farm vehicle with a fuel cell drive unit in 1959, a tractor with cells from General Electric. Hydrogen and oxygen play the leading roles in this energy harvesting process, which takes place within a fuel cell. The two elements react with each other, and the product is electricity. This electricity powers an electric motor. The efficiency achieved reaches 50 percent and more (by comparison: 37 to 45 percent in a diesel engine, and 32 to 40 percent in a gasoline engine). Aside from electricity, the only bi-products of the process are steam and heat, so nothing harmful.
This type of drive is now no longer considered merely experimental for road vehicles; indeed, in spite of limitations regarding operations, it is produced in small series. The chief limitations result from the still-sparse network of hydrogen filling stations. At the end of 2018, there were just 60 of them in Germany. The fueling process is quicker than for electric vehicles, and ranges are in the area of 550 kilometers.
Steam-powered vehicles were the first automobiles of all. Nicholas Cugnot got things started in 1769 with a transport cart for cannons. In a steam engine, water vapor drives the vehicle. The fuel used to heat the water in the boiler is coke, brown coal, wood or oil.
Further steam vehicle development shifted to England, where ash and non-gassing coal (anthracite) were available at low prices. In 1803, Richard Trevithick used a steam-powered carriage with some success to transport people within London. Sir Goldsworthy Gurney and Walter Hancock ran regular service between English cities with steam omnibuses starting in 1828 and 1831, respectively. And yet, England – the land of the steam engine – did not bring forth any noteworthy steam-powered personal vehicles.
It was instead in France, after the Franco-Prussian war of 1870/71, that the real progress was made in the development of steam vehicles. Following the steam buses of Amédée Bollée in 1873, Albert de Dion began working in 1883 to reduce the great weight of steam-powered passenger vehicles by using bicycle parts. In 1906, Fred Marriott set a new land-speed record for steam-powered automobiles with his Stanley Rocket model in Daytona Beach: 205.5 km/h. And yet, from the turn of the century onwards, the then-young gasoline engine overtook steam technology in Europe. It was lighter, cheaper, easier to handle and boasted higher efficiency.
With the gas turbine, combustion proceeds continuously in different areas of the engine, and not pulsating and in the same spot (cylinder head) as in a piston engine. Nor does the gas turbine have a back-and-forth motion of masses such as the piston, connecting rod and valve drive. Here all parts rotate and allow for vibration-free operation. Familiar from aircraft, this technology boasts good efficiency at higher altitudes and greater output than the piston engine. On earth, however, demand for transporting such large numbers of passengers over continental distances at speeds up to and beyond the sound barrier is limited.
Nevertheless, even passenger vehicle companies tried the gas turbine, because they wanted to apply the experience to land vehicles. Over the past half-century, this has led to a wide range of one-off test cars: roadsters and sports cars from Rover in 1950/1957 and Fiat in 1954, a semi-trailer truck from Kenworth in 1950, trucks from Laffly, Ford, General Motors and International from 1951, the record vehicles from Rover in 1952 and Renault in 1956, the dream car from GM in 1954, a sedan from Austin in 1956, a coach bus from Viberti in 1956 and the race car from Rover-BRM in 1963.
From 1963 to 1966, Chrysler inched toward small-scale production and examined the market viability of gas-turbine-powered passenger car by gathering input from 203 selected customers testing 50 loaner turbine vehicles. But high fuel consumption, sluggish responsiveness, unresolved material issues, leakage problems and poor efficiency, particularly with the small turbines produced for passenger cars, finally closed the door on the turbine.
The Stirling engine traces its origins to the heat engine developed by Robert Stirling in 1816. The principle consists of heating a hermetically sealed medium – usually a gas like helium – in a closed cylinder and then cooling it in another closed cylinder by means of energy applied from the outside. The gas goes back and forth between these chambers, constantly changing its temperature. This closed cycle can be operated with any external heat source. The development of the Stirling engine began, as was common for heat engines, as a stationary machine and can be divided into two phases. The first phase begins with Stirling’s patent of November 16, 1816 and ends before the year 1900. In just under a century, it had emerged that Stirling’s machine could be most favorably configured for outputs of up to 3 hp. With the introduction of gasoline, diesel and electric motors before the turn of the 20th century, trade, commerce and industry lost interest in the Stirling engine.
The principle of rocket propulsion was discovered by Greek inventor Hero of Alexandria in the first century AD. He routed steam into an axially positioned sphere with nozzles that caused the spin to rotate as steam escaped. The function is derived from the principle actio = reactio. Mass particles are repelled at great speed against the direction of flight, which results in an equal reaction / forward propulsion force (thrust) in the direction of flight.
In more recent times, people have only known fireworks rockets, the rocket apparatus for sea rescue operations and (ineffectual) anti-hail rockets. In the early 20th century, interest in rocketry gained currency once again. Following theoretical work in the US, Germany and the USSR, in 1935 the German Army Weapons Agency in Peenemünde began application-oriented development of rocket propulsion systems with liquid fuels, for both aviation and aerospace applications. Initial trials with terrestrial vehicles began in March 1928 at the Opel test track in Rüsselsheim with engineer Kurt C. Volkhart. Worldwide notoriety was achieved by Fritz von Opel’s attempted record drive on Berlin’s AVUS on May 23, 1928. Reaching 223 km/h, his race car, dubbed Rak2, failed to match the world record at the time, which had been set at 334 km/h on April 22, 1928.
This was followed by Opel’s Rak3, an unmanned rail vehicle that hit 254 km/h on June 23, 1928. Beginning on December 2, 1928, Kurt C. Volkhart made guest appearances with his rocket vehicle and motorcycle on the AVUS, the Nürburgring as well as in Heide, Oslo and Copenhagen.
Coal dust engine
In December 1899, Rudolf Diesel (1858 to 1913) experimented with a stationary engine that, instead of using diesel fuel, pumped coal dust into the combustion chamber with compressed air, mixed with petroleum for ignition. And the 20-hp test engine did indeed run for a few minutes, but then the ignitions started to backfire, dust and oil settled in a thick coat on the crosshead, connecting rod and piston rings. The machine factory Machinenfabrik Augsburg, where Diesel was allowed to perform his trials, refused to permit further experiments, and Diesel gave up.
One of the biggest problems with the dust engine was abrasion. The issue affected all components that came into contact with the fuel (= coal dust), e.g. the cylinder liner, piston rings and valves. Thanks to special materials and design measures, the wear problem was mitigated by the end of the 1930s, albeit at the cost of higher manufacturing outlays: a 100 hp diesel engine cost 17,300 marks, while a comparably powerful coal dust engine cost 22,000 marks, including auxiliary engines and license fees (1935).
No less problematic was the amount of ash produced. With a stationary one-cylinder engine with 170 hp of output and a consumption of 85 kg/h lignite dust with six percent ash content, the ash production amounted to the tune of roughly five kilograms per hour. This was approximately 3,000 times the amount produced by a conventional diesel engine and meant that with 2,000 annual operating hours, some 10,000 kilograms of hard, abrasive parts had to be withstood and discharged by such an engine. Because both the mechanical and thermal efficiency failed to match the values of the diesel engine, from a technician’s perspective there was little incentive to pursue further development.
In 1839 French physicist Alexandre Edmond Becquerel (1820 to 1891) discovered that certain materials, when exposed to light, emit electrons that produce direct current. In 1954, American scientists discovered that silicon is a particularly favorable absorption material. And because it is available everywhere, ever since then silicon cells have been used as power suppliers for stationary consumers, in satellites, camera exposure meters, signal systems, watches and pocket calculators. And to power cars, albeit to quite a limited degree.
Evidently fascinated by the elegant technology, in 1957 the Vice President of Chrysler Corp. considered it possible that before the century was out, the automotive industry would produce solar-powered cars. Although no carmaker has yet to launch a solar car, many solar-powered means of transport including aquatic vehicles and aircraft have since been built, beginning with the three-wheeled bicycles in the 1970s and the test Passat from Volkswagen in 1982 that had solar modules in the rooftop luggage carrier, to the solar passenger boats on the Spree, Alster, Maschsee and Neckar. Solar gliders have plied the skies as well. What they all have in common is oversized, sun-facing solar panels. Space constraints make it impossible to place such panels on cars. In concrete terms: to generate 100 watts in around 1978, a surface area of one square meter was required; by 1993, it was 0.53 square meters. But such large areas are simply not available on road vehicles. The solar cells on the aforementioned Passat supplied the vehicle electrical system with a paltry 160 watts.
Inexhaustible, free, clean: energy from outer space is all those things. The cosmic radiation that comes from there penetrates the Earth’s atmosphere as primary radiation comprised of energy-rich nuclear particles. Due to diminishing intensity, it reaches the Earth’s surface as secondary radiation. It consists of electrically charged particles and remains sufficiently energy-rich to supply homes and cars with energy. This, at any rate, was the conviction of Nikola Tesla (1856 to 1943), one of the great minds of science. The Croatian-American physicist and electrical engineer developed the principle of an alternating current motor starting in 1881, discovered wireless electrical energy transmission in 1887, and invented the (Tesla) transformer for the generation of high-frequency alternating currents in 1891. Around 1900 he occupied himself with an electrically powered car without an energy store or battery or other visible or invisible (inductive) means of power delivery. There were multiple test drives with “invisible power,” according to modern sources. But there were many more skeptics, who ultimately put an end to cosmic radiation as a drive technology. Whether the “invisible force” was really cosmic radiation or generated in some other way may never be known.
Source: With ADAC material