Low-energy vehicle - Christina Cherry

The term low-energy vehicle (NEF) refers to vehicles that realize significantly reduced energy consumption compared to the current average fleet consumption, or. In relation to a defined use, enabling significantly increased energy efficiency. The term is based on the low-energy house, but there is no uniform definition.

For models with internal combustion engines, terms based on fuel consumption per 100 kilometers are also common for such vehicles such as three-liter car or one-liter car. With the designation environmental car it was also chosen as the word of the year in the federal republic of germany in 1984.

General

There is currently no uniform technical standard for categorizing vehicles as NEFs, but the definition of an NEF should have an energy consumption that is significantly below current standard energy consumption levels. In this respect, it is generally understood that an NEF should be well below the fleet emission limit of 120 g CO2/km [1] set by the european union for 2015 at the latest. This value corresponds to a fuel consumption of around 5 liters of gasoline or. 4.5 liters of diesel per 100 kilometers or. An energy consumption of around 44 kilowatt hours (kWh) or 158 megajoules (MJ) per 100 kilometers.

In addition to low vehicle mass and a streamlined exterior, the design principles for realizing an NEF include the choice of an efficient drive system. According to the laws of physics, additional mass to be moved increases energy consumption linearly, especially depending on the acceleration and braking profile without regenerative braking, where part of the acceleration energy can be recovered by recuperation. Higher speeds mean a quadratic increase in driving resistance and thus a cubic increase in energy consumption.

When considering the total primary energy consumption (well-to-wheel), as is becoming more and more common, the supply expenditure (well-to-tank) for the drive energy is included instead of only the final energy consumption in operation (tank-to-wheel). A comprehensive life cycle analysis, which includes not only the total cost of ownership but also the energy consumption for manufacturing and recycling of the vehicles, is part of the environmental footprint.

In relation to the overall automotive market, many NEFs currently (2012) exist mainly as prototypes, test cars and small-series cars. In many countries, there are various incentives for the purchase of fuel-efficient vehicles. In Germany, for example, there is a temporary exemption from vehicle tax for three-liter cars.

Motivation

Economic efficiency

The need to produce and operate vehicles with the lowest possible fuel consumption is driven by the imperative to save energy. In addition to the sustainable use of limited energy resources, the economic operation of the vehicles is of particular importance. In addition to the acquisition costs, the continuous increase in fuel prices and the political, i.e. fiscal, promotion of fuel-efficient vehicles against the background of the increase in the number of vehicle registrations worldwide have a major influence on the economic efficiency of NEFs.

a major boost to the construction of low-energy vehicles came with the announcement by the californian government that, from a start date (postponed several times), it would impose punitive taxes on all manufacturers who did not produce a certain proportion of their vehicles in accordance with the uLEV (ultra low emission vehicle) or. Produce ZEV (zero emission vehicle) principle. ZEV means that the vehicle must be able to cover a certain distance completely without emissions. Today, virtually only electric vehicles can do this – the ZEV requirement (along with the EU’s 120 g CO2/km requirement) is the main driver behind the hybrid efforts of the major automakers. In europe, the EEV (enhanced environmentally friendly vehicle) standard is a motivating factor.

in 1996, the german manufacturer audi introduced an audi A4 avant duo, which was soon discontinued due to lack of demand (and because of its simple and inefficient technology).

The German three-liter models audi A2 TDI 3 l and VW lupo TDI 3 l also failed to generate an economic return – despite tax incentives for sales and subsidies for development – and the VW Group discontinued production (the lupo 3 l was available for order until may 2005; only 6,500 units of the A2 3 l were purchased).

Environmental protection

Internal combustion engines in cars account for about 20 percent of the world’s CO2 emissions, which are a major contributor to global warming. In addition, the petroleum reserves that serve as the energy source for most of today’s motor vehicles are expected to become increasingly scarce in the coming decades (see global peak oil production). The motivation is the ALARA principle (as low as reasonably acceptable – as low as reasonably bearable) or. Generally an ethical behavior. This ethical behavior can be attributed at least to some so-called "garage companies" that – often with roots in the environmental movement – produce vehicles based on bicycle technology in very small series and, for example, are also concerned about the environmentally friendly generation of the energy required for propulsion.

A reduction in CO2 emissions is the fundamental goal of an energy turnaround in transport . The verkehrsclub deutschland gives the sog. Auto-environment list, which is based among other things on energy consumption. Another evaluation is the FIA ecotest.

Indication of the energy consumption

In europe, fuel consumption for vehicles is usually expressed in liters of fuel per 100 km driven (distance consumed). In order to arrive at comparable figures, the energy content of different fuels must be taken into account. Diesel fuel has an energy density of 42.5 MJ/kg, gasoline 43.5 MJ/kg. By making the appropriate conversions and multiplying by the density of the respective fuels, one obtains a volumetric energy content of approx. 9 kwh/l for super gasoline and ca. 10 kwh/l for diesel fuel.

Another way of calculating energy consumption is to express it in terms of the amount of energy per payload transported per distance. This is the distance consumption per weight [l/(100 km × 100 kg)]. Comparing a truck carrying 20 tons of freight with 35 liters of diesel over 100 km with a fully loaded diesel car carrying 500 kg of freight (passengers and luggage) with 7.5 l, the energy consumption of the truck is 0.175 l/100 km per 100 kg, while the car needs 8.5 times as much, namely 1.5 l for 100 kg over 100 km.

the energy consumption labeling regulation, known as CO2 labeling for short, does not address energy consumption per km in joules or kwh.

Design measures for fuel economy

Driving resistance: the driving resistance determines the drive power [kW] required to achieve the desired driving performance (acceleration, top speed). For constant driving at low speeds, the rolling resistance, which is directly proportional to the speed, predominates; as the speed increases, the flow resistance (air resistance), which is quadratically proportional to the speed, predominates. The acceleration resistance is v. A. Significant in urban traffic.

Acceleration resistance : the acceleration resistance occurs with the change of the speed. It is directly proportional to the vehicle mass. Lightweight cars allow the use of smaller engines at the same acceleration, which operate at a more efficient operating point at constant speeds (where rolling resistance and air resistance are significant). Negative acceleration resistance (during braking) can be used for energy recovery (recuperation).: low rolling resistance coefficient due to low rolling resistance tires, low vehicle weight, low-friction wheel bearings. (aerodynamic drag): a reduction in the aerodynamic drag coefficient can be achieved by an aerodynamically favorable body shape, clad wheel arches and smooth surfaces (no door buckles, camera instead of side mirrors) as well as narrow tires up to a value of about cw0.16. A reduction in the cross-sectional area of the vehicle exposed to the airflow (vehicle projection area) due to seats located one behind the other or at least offset (two-seater with approx. 1 m² of vehicle projection area), or low seating position and little overhead space also contributes to optimization.
Internal resistance : low internal friction losses, in the case of the internal combustion engine mainly due to low viscosity oil and lower friction losses due to low cylinder deformation and better sealing of the piston track. Efficient transmissions, bearings with low friction. Freewheeling and if necessary. Starter-generator systems , with no losses during idling (pant friction, intake and exhaust resistance, bearings and shafts as well as auxiliary engine drives and their control). Due to the concept, the electric drive (motor usually with only two bearings, simple reduction gears with few bearings and gear pairs) generally has lower internal losses.

The efficiency describes the efficiency of the conversion of z. B. Chemical or electrical power into mechanical power: the main problem of the internal combustion engine is that its efficiency is highest at full load and decreases towards low loads. Specific consumption [g/kwh] therefore increases sharply with decreasing engine load. There are two approaches to solving this problem:

Efficiency-optimal gear ratio: power is the product of speed and torque. In order to produce a certain power, the most efficient operating point is the one at which this power is achieved with maximum load and lowest possible engine speed.

In manual transmissions, "long" ratios are a simple means of converting. However, the low acceleration reserve ("elasticity") at such a driving level reduces acceptance. Are an alternative to drive the engine always with high loads, but they have a worse efficiency than manual transmissions and are not very accepted. (there is no direct correlation between speed and engine speed).

use of diesel engines, which have better efficiency than gasoline engines due to the lack of throttle losses in the part-load range and can be highly supercharged due to low knock tendency.
Lean operation of internal combustion engines improves efficiency in the part-load range, but this is problematic from the point of view of pollutant emissions (nox). Lean engines, e. B. Direct-injection gasoline engines with stratified charge operation therefore require complex exhaust gas aftertreatment, such as nox storage catalytic converters.
The hybrid drive reduces the problem of high specific consumption of the internal combustion engines in the part-load range, since an additional electric motor operates at low loads, while the internal combustion engine is only used at higher loads.
Also by supercharging, z. B. turbocharging or compressors, the efficiency of an engine in the part-load range can be significantly increased. The liter output (= power per liter of displacement) is significantly increased so that the desired rated power is achieved with lower displacement volumes. As a result, the engine operates at higher – and thus more efficient – load points in the part-load range (downsizing).
The efficiency of internal combustion engines can also be increased in the part-load range by cylinder deactivation (ZAS). At low loads, cylinders are switched off, resulting in a higher and thus efficiency-optimized load point for the working cylinders. For small engines, however, the ZAS leads to a deterioration in noise comfort that is not accepted.

Vehicle design

Passenger cars for urban traffic should have the lowest possible acceleration resistance (low vehicle mass) and technical recuperation equipment, i.e. a regenerative brake. Your rolling resistance should be low (low rolling resistance coefficient of the tires and low vehicle mass). Flow resistance (air resistance) does not play such a major role here, example: smart.
Passenger cars for intercity traffic should above all have the lowest possible flow resistance (air resistance), d. H. A small vehicle projection area and a low cw value. Examples: loremo cabin scooter , VW one-liter car, aptera 2 series.

With the electric motor, the efficiency is largely independent of the operating condition.
For constant-speed driving with internal combustion engines, the gear that allows the lowest, smoothest engine speed should be used. When accelerating, the engine should be operated close to its lowest specific fuel consumption, if possible. In a modern gasoline engine, this range is about 3/4 of the maximum load and about 3000 rpm. Oversized internal combustion engines are principally more problematic from the point of view of the most favorable operating point possible, as they often operate at low – and therefore inefficient – load points in everyday use. the solution to this problem is smaller engines (downsizing) and continuously variable transmissions or transmissions with a higher number of gears.

Classification of NEF

In germany, some vehicles with particularly favorable fuel consumption figures enjoyed tax concessions. However, vehicles are not classified according to their energy consumption, but according to their carbon dioxide emissions, measured in accordance with Directive 93/116/EC.

According to german tax law, a five-liter car less than 120 g CO2/km. This corresponds to a distance consumption of 5.06 l/100 km gasoline or 4.53 l/100 km diesel. In the event of registration before 1. January 2000, these vehicles were exempt from motor vehicle tax. The term three-liter car will be taxed with carbon dioxide emissions of 90 g CO2/km. This corresponds to a distance consumption of about 3.4 l/100 km diesel or 3.8 l/100 km gasoline. The same regulations apply to alternative fuels in internal combustion engines; electric vehicles are taxed according to vehicle mass.

The term one-liter car refers to vehicles with a fuel consumption of less than 1.5 l/100 km, although for marketing reasons vehicles with a fuel consumption of 1.5-1.99 l/100 km are often included in this category.

models

Ultimately, the permanent introduction of such vehicles on a broad front has failed so far. However, some of the technology has found its way into series production of "normal" passenger cars (electrohydraulic clutch, covered hubcaps).

Models such as the smart show that even the smallest vehicles are accepted by buyers. mid-range vehicles are reaching fleet consumption levels of 7.5 l for some manufacturers, which some believe would recommend legal action by the state (as in california) to demand a reduction in these levels.

series models

Series models in preparation

The aptera 2 series was a range of three-wheeled vehicle models with gasoline (fuel consumption 0.78 liters gasoline/100 km) or electric motors. The aptera motors company went bankrupt in december 2011. [5] in april 2012, the zhejiang jonway group parts of the intellectual property purchased that belongs to the aptera 2 series. Aptera motors was founded as apterausa newly established, after zhejiang jonway together with smaller american investors, had bought up the company’s shares. [6][7][8][9]apterausa the gasoline version aptera 2g and the electric version 2e are to be produced in small series in the USA. The company, which has been operating independently of this since june 2013 zaptera is to build the aptera 2e electric variant in large-scale production in china as soon as the market permits. Apterausa according to the will of its boss, richard deringer, production is to be concentrated in detroit and santa rosa. Deringer does not want to wait for possible developments in china. [10][11] by producing exclusively in the u.s. since then apterausa a significant price increase is expected. If the originally planned Chinese-american production variant of the aptera 2e was to be built with approximately 30.000 dollars, prices are now expected to range between 80.000 and 100.000 dollars for the all-U.S. production variant. [12] according to previous plans, one or more models were to be launched in the first quarter of 2013. [13] this was changed when the plans were amended by the zhejiang jonway group first of all nothing. Deringer now hopes to be ready to start production in the first quarter of 2014 [obsolete]. [10]

Studies

The citroen ECO 2000 SL 10, developed between 1981 and 1984, achieved a total consumption of 3.5 l of gasoline per 100 km. Features of the study were used in the development of the Citroen AX.

In 1996, the twingo smile from Greenpeace consumed around 3.5 liters of gasoline under real-life conditions (RL93/116/EEC). [14]

the mitsubishi "i" concept [15] achieved only 3.8 l/100 km in the FIA ecotest 2003, albeit under practical conditions such as operation on a freeway and with air conditioning. The most fuel-efficient competitors in the test (audi A2 1.4 TDI, mini one 1.6, suzuki ignis 1.3 ddis) achieved 4.5 l/100 km under these conditions. [16] the opel corsa ECO 3 l consumed 4.3-4.7 l/100 km in practice.

The mercedes-benz bionic car is a concept study presented by mercedes-benz in 2005. The suitcase fish served as the aerodynamic model for the development of the vehicle . The fuel consumption of the diesel-powered four-seater with a cd value of 0.19 is said to be 4.3 l/100 km.

The concept study of the toyotas ES3 with diesel hybrid drive achieved 2.7 l/100 km (87 mpg). [17]

The daihatsu UFE III has a combined fuel consumption of 2.1 l/100 km.

Oscar (opensourcecar): [18] development of a 2-person electric car by students of the TU darmstadt, 6 kwh/100 km, range 300 km, top speed 130 km/h

In 1973, the shell oil company converted the 1959 opel P1 into a test vehicle. The vehicle was designed for competition and achieved a fuel consumption of 159 km/liter (376.59 mpg). 1975 the vehicle made it into the guinness book of records. In 1976, a small, lightweight special vehicle for one person achieved 403 km/liter (1141 mpg). These tests were carried out at very low powers and speeds. [19]

The loremo , a loremo AG design that has been continuously developed since 1995, consumes 1.5-2 liters diesel/100 km. [20] for lack of solvent investors, no series production came about.

The vehicle tuner 9ff converted a VW golf V 1.9 TDI by adding approx. 400 kg of the vehicle weight was saved in order to achieve a fuel consumption of 3 l/100 km. [21] the project was abandoned despite media support (VOX, stern.Tv, ams.Tv) not completed.

electric vehicles

In addition to vehicles with internal combustion engines, electric vehicles also achieve final energy consumption values equivalent to one liter of diesel per 100 km (that’s approx. 10 kwh/100 km), in some cases even lower. These are, for example, vehicles with lightweight bodies such as the hotzenblitz, whose production has now been discontinued, and the kewet from norway. The most economical vehicle is probably the two-seater TWIKE, which regularly consumes less than 5 kwh per 100 km from the grid (measured). This is roughly equivalent to a 0.5-liter car. The "only" single-seater cityel needs similarly little fuel. Even vehicles with a normal small car body, such as the Citroen AX Electrique, consume significantly less than 2 l/100 km. According to long-term consumption measurements, the citroen AX electrique runs on around 15 kWh per 100 km, measured from the wall socket, i.e. including all charging and battery losses. Based on just under 500 g CO2 per kWh in the German electricity mix in 2010, this results in a CO2 impact of around 75 g CO2 per km well-to-wheel when supplied with the normal electricity mix. However, this calculation does not take into account the line losses from the power plant to the socket and transformer losses, nor does it take into account the fuel production losses in the data for the vehicles with internal combustion engines.

If the batteries are recharged with CO2-free solar, wind or hydroelectric power, the CO2 impact per km is even lower and tends toward zero.

Other vehicles: cityel , TWIKE , these vehicles consume the equivalent of less than 1 l/100 km. The tesla roadster from tesla motors (california) with purely electric drive and the driving characteristics (and price) of a sports car has an energy consumption of 11 kwh/100 km with a range of 400 km on one battery charge (manufacturer’s data). The tesla roadster uses commercially available lithium-ion batteries, which have good charge-discharge efficiency thanks to design measures and a good battery management system.

the fuel consumption and CO2 figures given above for the citroen AX also apply in principle to many five-door and four-seater french electric cars (peugeot 106 electrique, renault clio electrique, citroen AX electrique), which can be operated as nearly one-liter cars with optimized charging and driving.

Technically, even older vehicles can be upgraded, as demonstrated by the hotzenblitz converted in 2007 with a practical range of more than 350 km. [22] if batteries are installed that do not take up too much space and are not too heavy, several recharging stops must be made for longer distances. The charging time for today’s traction batteries depends less on the accumulator and more on the available charging infrastructure (strength of the charger, capacity of the power connection). A recharge of 80 % in 30 minutes, as with the chademo direct current charging system, is technically feasible without any problems.

Low-energy vehicles are not widespread

Although series production of the three-liter car was welcomed in principle, it was discontinued again because the low demand made it uneconomical for manufacturers to produce conventional models due to the high acquisition costs. The development of successor models to the VW lupo 3L TDI (z. B. On the platform of the VW fox) was discontinued. Production of the audi A2 3L TDI was discontinued in mid-2005 without a successor. The smart cdi is gaining popularity precisely because of its low CO2 emissions – in principle, however, vehicle production has often been called into question and has not yet offered the original concept of the electric vehicle in series production. The opel astra eco4 with modified bodywork has disappeared in the new model series.

Fuel costs are too low, fixed costs too high, often assumed. Only 1 l/100 km more consumption causes over 100.000 km at 1.60 €/l fuel costs, but additional costs of 1600 €.
The product advertising of many car manufacturers continues to focus on high-powered sporty vehicles.
Customer demand for high-performance cars, driven by advertising, is counteracting efforts to reduce consumption.
Streamlined body shapes are unfamiliar and have so far been rejected by the majority as unaesthetic. Vehicle design has been identified as a key success factor for the marketability of passenger cars, so there is a trade-off between customer needs (aesthetics) and efficiency.
Modern vehicles weigh significantly more than their predecessors, have more electrical consumers, and accordingly have a higher power requirement. Modern engines can only compensate for these disadvantages to a limited extent.
Existing models (z. B. VW lupo) are said to have negative characteristics (high purchase price, susceptibility to defects, high maintenance costs), which make them appear unattractive to potential customers. The additional price of an audi A2 3L compared with the basic diesel version (4.3 l/100 km) was z. B. However, only 300 €. According to ADAC breakdown statistics, the A2 achieved first place in its class in the years 2003 to 2006. The aluminum vehicle also took first place in the TuV statistics in 2004 due to its freedom from defects.
The problem of the cost of energy storage for electric vehicles has so far been insufficiently solved due to the lack of mass production. The utility value is so far partly limited by the limited range.
Driving behavior that requires getting used to, which appears uncomfortable to the untrained customer and sometimes makes him feel insecure, as already shown by the VW golf ecomatic with engine shutdown built at the beginning of the 1990s.
The automotive industry has been accused of using the three-liter car only as an alibi project. This accusation is questionable in view of the development costs.
The purchase prices, the resulting long amortization period and also the limited utility value of some models (smart, lupo) have so far prevented three-liter vehicles from establishing themselves on the market. Incentives such as the €511 tax exemption have also not contributed to the success of the project.
Advantages such as the higher final speed of the eco variants due to lower aerodynamic drag and a greater range were not addressed. Overall, the vehicles were not promoted enough.
The disclosure of CO2 emissions and fuel consumption is done very discreetly and fails to have an impact on purchasing decisions. For example, the (legally required) disclosure of fuel consumption by vehicle dealers has been implemented only hesitantly and after various fines have been imposed.
The automotive industry promotes alternative fuels, some of which have an uncertain life cycle assessment and availability, in order to avoid a fundamental reorientation. Low-energy vehicles, however, can increase the share of alternative fuels in the face of limited resources. This can be used to counter objections that biofuels are far from being able to meet demand.
Development of appropriate technologies and use of lightweight materials increase cost per vehicle. However, since most customers are not prepared to pay more for an efficient car than for a conventional one, there is (as yet) no significant market for these vehicles.
In some countries with an affinity for cars and technology, efficient passenger cars are mistakenly compared with subcompact cars (e.g., the "smallest car"). B. Smart), which at best can only be used as a second or third car and do not contribute to any reduction in energy consumption in transport without a change in habits.
Optimization in terms of fuel consumption does not automatically lead to a lower overall environmental impact. Most fuel-efficient vehicles have a diesel engine. However, without sophisticated filter technology, these vehicles generate soot particles (see also: fine dust).
Many old vehicles can also reduce their CO2 contribution with biofuels. Savings in the consumption of fossil fuels can also be achieved by using alternative energy sources such as biodiesel or ethanol. Consumption by motor vehicles in germany accounts for approx. 12 % of total (crude) oil demand from. However, this alternative is controversial in terms of food prices, as feedstocks such as corn are no longer available as food once ethanol is produced.
Various measures to reduce consumption cause an increase in energy consumption in production. The production of aluminum and magnesium is very energy-intensive. If the energy for smelting and production is added to the consumption per kilometer and the resulting systems of equation for otherwise identical vehicles made of aluminum and steel in the size of an audi A2 are equated, the average point is approx. 12.000 km – below that, the steel vehicle has the better environmental balance, above that the aluminum car. Annual mileage is more easily achieved by fleet vehicles, so it is conducive when loan systems and participatory ownership models (e.g., fleet vehicles) are introduced. B. car sharing) can be further developed. Vehicles with expensive alternative drive systems also become easier for the general public to finance.

Compared with previous years, however, the first signs of a change or even a trend reversal are becoming visible: while the number of new registrations in the vehicle classes from small cars to luxury cars in germany fell in the first five months of 2012 compared with the same period of the previous year, there was an increase in the number of new registrations in the "smallest car" class [23] an increase of 16.2 percent. [23] This vehicle class includes many low-energy vehicle models.