Driving bans for diesel?

A plea for more objectivity

by Rainer Schopf

cc. The author is a trained aircraft mechanic, studied automotive engineering at the Technical University of Berlin and taught for 35 years at the Oberstufenzentrum Kfz-Technik (Occupational Training Centre for Automotive Engineering) in Berlin. His essay takes up the article “VW Dieselgate” by Ernst Pauli in Current Concerns No 4 of February 2018 and continues it on a technical level.

Postfactual driving bans – without any technical expertise

On 27 February 2018, the German Federal Administrative Court allowed German cities in principal to impose driving bans on diesel engines due to their NOx emissions. This judgement is absurd, influenced by almost no technical expertise and typical for the postfactual age. Opponents and users of diesel engines are engaged in an ideological struggle. The Green Party and environmental associations want to tramp down the diesel engine, regardless of the consequences. After the successfully implemented energy transition in Germany – the shutdown of all nuclear power plants, hard coal and lignite plants are to follow – they now want to force changing to electric cars within a few years with all might. The VW diesel fraud affair served the US as reason for an economic war against German manufacturers. On the other hand, the driving bans are Germany’s own doing and without necessity destroy the diesel engine and thus a mature technology in which Germany is leading. As early as April of this year, Hamburg rushed ahead with driving bans for diesel cars on two particular roads on the initiative of Environment Senator Jens Kerstan of the Greens. Baden-Württemberg has announced the first driving bans for 2019. In order to make the debate more objective, it is essential to take note of some physical, chemical and technical facts. Only on this basis can traditional drives be seriously compared with alternative drives.

“We will certainly have to stop burning fossil fuels (oil/natural gas) in the long term. But the diesel engine is far from dead, and many alternatives are still unclear. Scientists and technicians have helped people to expand their mobility and apply their findings to the benefit of human development. This can only be done on the basis of sound analyses and forecasts and not in ideological trench warfare. Political activism has never solved the problems at hand. Instead, we must enter into an open dialogue about the advantages and disadvantages of the various drive concepts.”

Market share of diesel engines

Diesel-powered vehicles have so far accounted for 53% of new registrations in the 15 largest EU countries. In Germany, the share before the 2017 diesel scandal was at a maximum of 45%, with a strong downward trend to an estimated 25% in 2025, followed by France and Ireland (73% each), Spain and Belgium (69% each) and Italy (57%). There is no threat of driving bans in these countries. Are the diesel engines there cleaner than in Germany? No. The same emission measurement procedure applies, but the handling is different.

Measuring stations

Before 2010, the rule in Germany was to measure the exhaust immission concentration at a height of 4 m and 4 m away from the centre strip of the road. Exhaust gases have the pleasant property of quickly mixing with the ambient air, which reduces the exposure of the people. Initiated by the Greens, the Federal Immission Control Regulation of 2010 no longer includes the four-metre distance. In Germany today, measurements are carried out as close as possible to the source of the exhaust gases, at busy roads, valleys or tunnel exits, where the exhaust gases cannot dilute quickly. The most notorious measuring point is a location called Neckartor in Stuttgart, located in a basin, with frequently highest NO_x values. This is what other European nations do differently. They measure area-averaged in loaded and unloaded roads and thus remain below the permitted limit value. This limit is only exceeded at a few points in Germany, but not reached area-averaged. Not the quantity, but the quality and balance of the measuring points is delivering significant results.

Combustion

In a full combustion of a fuel and air mixture nitrogen (N), carbon dioxide (CO₂) and water (H₂O) is produced. Former exhaust components such as lead and sulphur compounds are no longer contained in the fuel. Incomplete combustion produces carbon monoxide (CO), nitrogen oxides (NO_x), hydrocarbons (CH) in gasoline engines and additionally particulate matter (PM) in diesel engines. Whether combustion is complete or incomplete depends on the air/fuel ratio (λ, lambda), which is the quotient of the amount of air supplied to the theoretical air requirement. If λ= 1, the expert speaks of a stoichiometric mixture, below 1 it is fat (lack of air) and above 1 lean (excess air). Combustion takes place in diesel and petrol engines at different lambda values, so that the exhaust gas compounds are different, creating advantages and disadvantages for both engine types.

Diesel engine

At its optimum operation condition, the diesel engine uses 45% of the fuel for propulsion, i.e. it is up to 50% more effective than the petrol engine. The diesel engine runs with excess air in almost all load ranges and thus contributes to a significantly higher fuel yield. Today, diesel-fuel is injected almost exclusively with electronically controlled piezo injectors. After its debut in 1995, the common-rail engine (CR) has undergone rapid development, replacing all previous injection systems working at that time at an injection pressure of only 120 bar. The pressures in the common rail system (common line) are unimaginably high (2,500 bar), and the switching times are extremely short: These injectors open and close reliably at a engine frequency of 30 cycles per second in each cycle up to seven times for targeted pre-, main and post-injections, i.e. in fractions of milliseconds. An uncontrolled injection would rupture the diesel engine. Pressure and temperature ensure incredibly fine atomisation in the combustion chamber and thus maximum fuel utilisation.

The CR engine – a brilliant engineering acievement

The triumphal march of the CR engine was achieved by the brilliant contributions of hundreds of engineers. The energy balance clearly speaks in favour of the diesel engine and against the petrol engine. The only problem with diesel is its NO_x emissions. At 80 mg/km, this is significantly higher than at 5 mg/km for the petrol engine. However, the NO_xvalue of diesels has been reduced by 70% since 1990 and should reliably fall below the current limit value by 2020. Furthermore, the toxic effect of NO_x is discussed highly controversially. Fundamental criticism of the verdict on the driving bans for diesel comes from pulmonary specialists. Martin Hetzel, chief physician at the Stuttgart Lung Clinic, believes that from a medical-scientific point of view there is no causal evidence that NO_x concentrations of up to 100 microgrammes per cubic metre of air cause illness. Retrofitting older diesel engines would also require two years of testing before they could be registered and would then become obsolete in 2020. The polemic against diesel technology (allegedly one hundred thousand deaths due to NO_x emissions) is simply irresponsible and a crime against the good faith of uninformed consumers. It undermines the fantastic advances in diesel technology.

Huge progress also in exhaust gas aftertreatment

Gasoline engines today have exclusively controlled three-way catalytic converters to convert CO, NO_x and CH into non-toxic components. The exhaust gas treatment of the diesel engine is much more complex: exhaust gas recirculation, oxidation catalyst, secondary air injection, particle filters, NO_x storage and selective catalytic reduction(SCR) catalysts using the so called AdBlue (urea) as a cleaner fluid. Together the systems serve almost exclusively to reduce NO_x and particulate matter. Huge progress has been made in this area. Clouds of black smoke are a thing of the past. In the past, soot output was measured with the blackening rate(SZ) of white paper. That is no longer necessary today. One can filter the exhaust with a white handkerchief, it stays white even at full load.

In both engines, the perfect functioning of the pollutant reduction system is not random, but is permanently electronically controlled. On-board diagnostics(OBD) has been mandatory since 2000. It monitors all exhaust gas relevant components. At the slightest fault, the malfunction indicator lamp (MIL) reports a fault to the driver. He is then obliged to drive the vehicle immediately to a workshop and have the fault corrected immediately. The driving distance after the warning light lights up is stored in the fault memory and can be read out by the police during a road check. Failure to do so could result in drastic penalties.

Gas engine – a technical challenge

Even the gas engine is still not a real alternative to petrol and diesel, although it has been tested and is proved for decades. Due to the approximately halved carbon content of gas, CO₂ emissions are also approximately halved compared to diesel and gasoline engines. Obstacles are its heavy gas tank, the lack of infrastructure (gas filling stations) and the driving bans in multi-store car parks due to the risk of explosion in case of leaks. Gas engines are only increasingly used in cruise ships because the heavy oil driven cruise ships have fallen into disrepute and paying passengers pay attention to environmental awareness. The Meyer shipyard in Papenburg is currently building the first cruise ship with a gas engine. The technical challenges are enormous. To liquefy the gas, it must be cooled down to minus 162° C. Each of the three gas tanks is 35 m long and 8 m in diameter with a total capacity of 3500 cubic metres. But in the ports the infrastructure is often still lacking. Container ships thus continue to burn heavy fuel oil and are called swimming polluters. In Hamburg, they are expected to account for more than 40% of NO_x emissions. Prohibited? Obviously not. Beautiful new world: The port is booming and the diesel car drivers are being expropriated.

“And by 2030, up to 30% more electric cars are supposed to be on the roads: Then the lights will go off in Germany.”

Electric propulsion

Depending on the design, the electric motor has an efficiency of 80% to 90%. That’s a fantastic value as such, but be careful. Looking at the entire energy chain of electricity generated by combustion (coal/oil), the overall efficiency falls below 30% and is therefore even worse than a petrol engine. Losses occur in the power plant, during power transport, charging, discharging and through the power electronics. The situation is different if the electricity is generated in an environmentally friendly way by wind, solar or water power. In the first half of 2018, 39% of the electricity in Germany was already generated from these alternative energies, and the trend continues to rise. There are a number of problems that stand in the way of this pleasing prospect. The further “asparagation” of the landscape by wind turbines is reaching its limits. At least twenty times more wind turbines would have to be installed. Hydroelectric power plants may be an alternative for mountainous regions, but in Germany they have a shadowy existence.

Electricity transport problem unsolved

And we have as well an unsolved transport problem. Schleswig-Holstein, for example, produces 100% of its energy requirements from renewable energy, mainly from huge offshore facilities in the Northern Sea. Even more electricity could be generated. However, electricity is not lacking in the more agricultural north, but in the industrial west and south of Germany. So power lines have to be built from north to south – with high voltage transmission poles? The residents, on the other hand, sued successfully, citing electro-smog and the devaluation of their land. Going underground? Not affordable, underground cables cost about three times as much. The necessary line projects do not succeed for years now. If the electric driven car population was to be widely expanded, the structure of the grid system would have to be completely changed. That would only be feasible in decades.

Next problem – Overload of the electricity grid and ethical issues

If you try to have a charging station for your new electric car installed in your underground car park because the public ones are too sparsely sown. Your application is rejected by the property management, the power grid would collapse. And by 2030, up to 30% more electric cars are supposed to be on the roads: Then the lights will go off in Germany. And the last point of criticism: the electric cars themselves. The batteries are still much heavier than a fuel tank, their range is still modest, the acquisition costs extremely high and the raw materials such as lithium and cobalt for the batteries come predominantly from Third World countries, often affected by child labour, inhumane working conditions, corruption and civil war. In February, a major southern German automobile manufacturer and a consortium concluded a price and volume secured supply chain for cobalt from the Congo. Now the government of the Democratic Republic of the Congo has suddenly increased the price of mining licences, and the corresponding mining law was rewritten overnight. The market size for cobalt has tripled since 2016, Congo holds 60% of the deposits, and the government will cut itself a mighty slice of the raw material cake. Do we then use our progress to finance the government’s arms purchasing for a fight against its own people? What a hideous idea.

Hybrid propulsion

Vehicles with two different types of drive are called hybrid drives. Usually an internal combustion engine is combined with an electric motor to reduce pollutant emissions and fuel consumption. Inner-city, at low speeds, one drives electrically and overland with a petrol or diesel engine. All of these vehicles have a start-stop function for urban traffic jams and regenerative braking, called recuperation. During deceleration, the electric motor becomes a generator, i.e. it converts kinetic energy into electrical energy and feeds it back into the battery. This is a well-known process from the rail technology of trams and electric locomotives. The hybrid drive is an important upcoming technology. Around 90% of all taxis in Zurich are now hybrid vehicles.

Conclusion – Prudence is needed

The emission values for diesel and petrol engines have been issued since 1992 (Euro 1) and have been constantly tightened since then. Of the 15 million diesel vehicles in Germany, only 17.8% meet the latest standard (Euro 6). Driving bans would therefore affect 81.7% of all diesel drivers, i.e. 12 million drivers whose vehicles have also fallen drastically in resale value, are often considered unsaleable and are increasingly being scrapped. This expropriation cannot last. Responsible politicians advise prudence. When Daimler, BMW, VW, Opel and others are brought to their knees, many industrial locations in Germany are in a bad position. The legislator would be well advised to examine the ruling in peace and to press for a nationwide solution. This process will not be completed until 2020 at the earliest.

“Driving bans would therefore affect 81.7% of all diesel drivers, i.e. 12 million drivers whose vehicles have also fallen drastically in resale value, are often considered unsaleable and are increasingly being scrapped. This expropriation cannot last. Responsible politicians advise prudence. When Daimler, BMW, VW, Opel and others are brought to their knees, many industrial locations in Germany are in a bad position. The legislator would be well advised to examine the ruling in peace and to press for a nationwide solution.”

Questions and perspectives to be clarified

Until then, important questions will have to be clarified, such as a possible retrofit for older diesel vehicles, responsibility for the cost and the introduction of another, now blue sticker. The share of hybrid and electric drives will increase moderately, but the major reversal will not take place in the next 10 to 20 years and the diesel engine will experience a renaissance. In the short and medium term there is no proven alternative to the diesel engine. In the long term we will have to say goodbye to fossil fuels. The resources of oil, which have often been said to be dead, are indeed finite. And the unchecked emission of CO₂ will cause climate change in the long term. The Americans continue to build high-volume gasoline engines with extremely high greenhouse gas emissions: “Big is beautiful,” they say, giving notice to the global agreement to reduce CO₂ emissions. America first is their motto, how is that supposed to work out in the long run? European car manufacturers have been working successfully for decades on downsizing the displacement of engines: ever more effective smaller engines, with less fuel consumption and less exhaust gases. The conflict is obvious and that is why the American government is attacking German car manufacturers. Despite the diesel scandal, VW is excellently positioned and strives to become the world’s largest manufacturer. Other European car manufacturers are also shining with positive sales and profit figures.

Every epoch has its companions, from horse and carriage via steam engine to petrol and diesel engines. We will certainly have to stop burning fossil fuels (oil/natural gas) in the long term. But the diesel engine is far from dead, and many alternatives are still unclear. Scientists and technicians have helped people to expand their mobility and apply their findings to the benefit of human development. This can only be done on the basis of sound analyses and forecasts and not in ideological trench warfare. Political activism has never solved the problems at hand. Instead, we must enter into an open dialogue about the advantages and disadvantages of the various drive concepts. It is to be hoped that objectivity will return to the discussions on individual mobility. •