Report 2 (of 5): Transport of the Future? - Sweden

Introduction

Approximately 90 per cent of the environmental impact caused by a diesel truck or bus occurs during the vehicle’s working life. The production and scrapping of the vehicle together account for the remaining 10 per cent. This is due primarily to the emission of carbon dioxide while the vehicle is in operation which adds to the greenhouse effect. In densely populated areas and cities, it is important to reduce emissions of nitrogen oxides, carbon monoxide and hydrocarbons which have a negative effect on both health and the environment.

As overcrowding and air pollution in our cities continue to escalate, Volvo, the Swedish motor manufacturer, is attempting to produce two vehicles which create "the least possible environmental burden". The Environmental Concept Bus and Truck have been developed as prototypes and are viable concepts, even if they are not commercially feasible at the present time.

Environmental Concept Vehicles

Compared to today’s vehicles, the Environmental Concept Bus (ECB) and the Environmental Concept Truck (ECT) produce virtually negligible amounts of harmful exhaust emissions. The drive line in these vehicles is a series hybrid featuring an ethanol powered gas turbine with an integrated high speed generator, batteries and electric motor. The gas turbine can be run on virtually any liquid or gas fuel, without necessitating major modifications. In this particular application, the engine has been modified for ethanol - a renewable fuel which can be produced from sources such as timber.

This is a solution which yields very small emissions of harmful exhaust gases. Emissions of nitrogen oxide are just one tenth of those generated by a conventional type of diesel engine.

Powering the ECT and ECB

The best way of combining sufficient operational range with a zero-emission facility is hybrid power where batteries are used for short stretches in particularly vulnerable environments such as city centres, with a combustion engine providing power at all other times.

The combustion engine in the Volvo series hybrid is a gas turbine which consists of a compressor, turbine, combustion chamber and heat exchanger which harnesses the heat in the exhaust gases and also acts as a silencer. These components combine to form a compact mobile power plan, the high speed generator unit.

The ECT and ECB offer two power alternatives - hybrid power and battery power. Under hybrid power, the high speed generator unit propels the vehicle via an electric motor fitted to the rear axle. When only a little power is required, the unit diverts all the surplus energy to the batteries for storage. When extra power is needed, the batteries release this energy to propel the vehicle at higher speed.

Structure of the ECT and ECB

The frames of the bus and the truck are built entirely of extruded aluminium beams which create a space frame covered in aluminium sheeting. The structure is both lightweight and strong. Although, the production process does require large energy resources, the recycling is easier and less energy intensive than for steel.

The middle section of the bus is made of robust aluminium beams and there are sturdy steel roll-over cages at the front and rear which would prevent the roof from collapsing into the passenger compartment in the event of a roll-over accident.

A large proportion of the material originally used in the manufacture of the vehicles can be recycled and returned to the production process.

Suspension System

Active suspension in the vehicles contributes to improved safety and higher levels of comfort. The advanced suspension system reacts instantly to compensate for any irregularities in the road surface and gives the vehicles excellent anti-roll stability. The floor height of the bus above the road surface is usually 320 mm but with the active suspension, it can be lowered to 170 mm to aid entry and exit.

Batteries

The ECT and ECB are equipped with Nickel-Metal-Hydride batteries (NiMH) which currently offer the best performance in terms of environmental suitability and energy storage capacity. The NiMH batteries weigh half as much as lead-acid batteries and are far more environmentally friendly. They are maintenance free with a long service life and they are designed to be recycled to about 95 per cent. In hybrid operations, the batteries are recharged very quickly by the HSG unit. They can also be recharged from the mains supply. The batteries are well protected in three separate units and the vehicle will continue functioning even if there is a fault in one of the units. The batteries provide 25 kilometres of zero-emission driving before they need to be recharged.

The drive line’s electric motor not only propels the vehicle, it also functions as an electric brake retarder. This design allows braking energy to be used to charge the batteries instead of being lost as surplus heat. At the same time, the retarder provides gentle braking and reduces brake lining wear.

Tyres

The Michelin tyres have been specially developed for Volvo’s ECT and ECB vehicles. Both the material and the production process are optimised for minimal environmental impact. The tyres tread section is made without any environmentally hazardous oil additives.

The Michelin "Super Single" rear tyres are 495 mm wide and provide 30 per cent lower rolling resistance than standard tyres. This means lower energy consumption and therefore, lower exhaust emission levels. The front tyres offer about 15 per cent lower rolling resistance.

Mirrors

The rear view mirrors have been replaced by T.V. cameras because they provide better all round visibility. In addition to the side mounted camera, there is a camera which monitors the rear of the truck and is activated as soon as reverse gear is engaged.

Lights and Indicators

The conventional bulbs in the turn indicators, position lights, tail lights and braking lights have been replaced by light-emitting diodes (LED). They consume just 20 per cent as much energy as conventional bulbs and they last virtually forever. LEDs are far more durable to vibration and they light up more than 1,000 times quicker. For brake lights, this faster activation time can give a following driver several more metres in which to react.

The headlamps and auxiliary lamps feature gas-discharge bulbs which offer a more intense beam, long service life and low energy consumption. They are supplemented with UV lights which offer twice the visibility of normal bulbs and work by reflecting off UV sensitive substances found in textiles and minerals etc.

Heating and Air Conditioning

The conventional source of heat in a vehicle is from the combustion engine’s coolant. Cab heating in the ECT and heating for the ECB comes from the coolant which carries away the surplus heat from the electronic systems, supplemented with electric heating. In order to reduce energy consumption and the risk of cold down-draughts, the cab of the ECT is well insulated and the door windows are double glazed.

The air conditioning system uses iso-butane refrigerant and it contains neither freons nor other chlorine-based chemical compounds which can impair the ozone layer.

Noise Emissions

The noise level is low. The gas turbine produces a soft whining noise and when the battery power is activated, there is no noise at all.

ECT Specifications
 

The cab is a walk through one and offers full standing height at 190 centimetres. It also has a floor height of just 60 centimetres above the ground which is a feature that is appealing for any driver. The driver sits at almost the same level as pedestrians, cyclists and cars which increases the safety aspect of the truck. Short and low, the ECT is built for dense city traffic.

ECB Specifications
 

In a conventional bus, the drive line usually has to be positioned below the floor, and this sets the limit on how low the bus can actually be built. None of these considerations need to be taken into account with the ECB because there is no gearbox or propeller shaft and all power transmission takes place electrically.

By pulling apart the axles and placing the wheels way out in their respective corners, so they do not affect the interior passenger space in any way, and by fitting most of the drive line components in the roof, a very long wheelbase and a low and flat, uninterrupted floor can be made. The ECB has been designed to accommodate the needs of disabled passengers and there is no difficulty in boarding the bus with either a wheelchair or a pram.

The short overall length of the ECB (1.3 metres shorter than most city buses) in combination with four wheel steering and speed dependent power steering means that the ECB is extremely easy to manoeuvre. In the ECB, the driver sits directly above the front axle, midway between the two front wheels which provides excellent vision.
 
 

For further information, please contact:
 

Intermediate Technology would like to thank Volvo - in particular,Michael Borg and Lars-Ake Weimar - for providing the original material on the Environmental Concept Bus and Truck.
 

Further reading available from ITDG Development Bookshop

Electric Vehicles: With aspects on developing countries
Markus Eisenring
£12.95, (SKAT), 1998, ISBN 3908 00183 8

Environmental Limits to Motorisation: Non-motorised transport in developed and developing countries
Urs Heierli
This book examines non-motorized transport - bicycles, rickshaws, electric vehicles - as a decisive component in a new strategy for urban development in both developing and developed countries. It provides useful case studies, tables and many illustrations.
£17.00, (SKAT), 1993, ISBN 3908 00141 2
 

TVE/ Practical Action gratefully acknowledge support for the HANDS ON programmes from the UK's Department for International Development (DFID), the European Commission (EC), the UN Foundation and UNDP/The Equator Initiative in collaboration with the Government of Canada, IDRC, IUCN, BrasilConnects and the Nature Conservancy.