Lean and Green - the Clever vehicle
Current mobility trends are unsustainable - in simple words, we use our cars too much. They congest our cities and harm our health. However, we cannot stop driving altogether. A European consortium is designing a better-behaved vehicle for the future: cleaner, quieter, leaner - and stylish.
Road transport is a difficult area for policy-makers to implement change because of the huge benefits of freedom and mobility that cars offer. However, change is necessary. Much of the pollution that damages health, and the greenhouse gas emissions that drive climate change, come from road transport. Lost productivity and high noise levels are other consequences of road congestion. All stakeholders, including car manufacturers, agree that change has to happen – cars and driving habits must change. Anti-car measures, such as urban parking restrictions and congestion charging schemes that are appearing in towns and cities across Europe, reflect policies to change behaviour and reduce car use. In addition, there are large research and development efforts to develop cleaner, quieter cars and engines, as well as new fuels that emit less pollution. Often, these efforts aim at incremental technological improvements which can be quickly implemented – but others seek larger leaps in technology and design.
Designing a lean machine…
Berlin Technical University leads the FP5-funded Clever project (Compact Low Emission Vehicle for Urban Transport), a consortium of nine partners covering a large part of the automotive supply chain. Clever is developing a vehicle for urban transport that is small, safe, and energy efficient with low noise and emissions. Their design is a three-wheeled vehicle, taking two occupants and luggage and fully enclosed against the weather. It is small enough – less than one metre wide – to make a real difference to the road and parking space it needs; it will have low CO 2 emissions, under 60g/km and much less than half emissions from conventional cars; and it will meet current safety specifications for occupants and pedestrians. As well as these technical specifications there are other considerations, in particular the performance and handling must be acceptable to drivers.
…and a mean and clean machine
Heiko Johannsen, the project coordinator from TU Berlin, explains the technology choices. “The small size is logical because estimates show that an average urban car trip has less than 1.5 occupants – so large cars are not usually needed. So we design to save space, reducing the weight and thus fuel consumption, and allowing the vehicle to use narrower lanes and smaller parking spaces. The three-wheel design tends to give less rolling resistance than four wheels and a better aerodynamic shape – both features that improve fuel efficiency – and it also reduces the complexity of the front wheel suspension, which cuts costs.”
The car is powered by compressed natural gas stored in two removable cylinders that are custom designed for ease of handling and refilling. Natural gas emits around 25% less greenhouse gases in a normal car, but Clever aims for bigger reductions. The French partner which adapted the engine to natural gas, the Institut Français du Pétrole, increased the ‘swept volume’ of the engine cylinders, allowing the engine to run more slowly and bringing several benefits, as Johannsen explains. “The lower engine speed both reduces emissions and lowers engine friction – which enhances fuel efficiency. It also produces less noise. Due to the increased displacement, the torque of the vehicle will be higher – giving the higher levels of acceleration needed in urban traffic for acceptable driving performance. These measures, together with a lightweight vehicle design, enable us to meet the CO 2 emissions target of 60g/km easily. This is well beyond the current industry target of 140g/km. When the catalyst is added, we expect overall exhaust emissions to easily meet European targets.”
Stability when cornering is important for safe and acceptable handling behaviour – so Clever has a novel, electronically controlled, tilting chassis developed by the University of Bath. Safety also requires new approaches says Johannsen: “Normal cars have a crumple zone of 50cms while Clever will offer not more than 25 to 30cms. This means that the deceleration in a crash is much higher than in normal cars. In addition to this, the available space for the occupants is smaller than in conventional cars. This is the reason why our partner Takata-Petri from Berlin is developing more powerful and faster restraint systems. Tyre behaviour is also important for safety while cornering – depending on the tyres fitted, Clever could tip over or slide in a critical situation. Clever needs a motorcycle tyre at the front tilting wheel and car-style tyres at the rear non-tilting wheels. In order to balance cornering forces correctly ,between front and rear axles the rear tyres are likely to be narrow, which has led to the choice of a motorcycle-based design. In addition, the energy consumption has to be considered and is taken into account in the tyre design. Our partner Cooper-Avon from the UK is developing a car-style tyre that fits on to a motorcycle wheel.”
A driver survey
Just being innovative, or ‘green’, is not enough to be ensure acceptance. The consortium puts strong emphasis on ‘driver acceptability’. This emphasis is found in all design and technical aspects of the car. As an accompanying measure, the consortium will undertake a survey on drivers’ behaviour and preferences to better understand the particular obstacles to using the Clever car and similar vehicles with smaller capacity and new fuel requirements. The University for Bodenkultur in Vienna, Austria, is conducting the survey by sending a postal questionnaire to 1 200 drivers in Graz (Austria) and Thessaloniki (Greece) and conducting around 300 face-to-face interviews. Johannsen explains: “When you drive in urban traffic you must feel ‘comfortable’, for example you need to be able to drive at the same speed as the others and refuel at your convenience. A key aim of the survey is to understand how the Clever vehicle fits into this framework, and to identify the room we have for more improvements and where compromises are needed.”