Double delivery

A consortium is developing a system designed to allow conventional delivery vans to be cheaply converted to run in a zero-emissions, all-electric mode for urban use.

The ADDZEV (affordable add-on zero emissions vehicle) project aims to adapt light commercial vehicles so the front drivetrain remains driven by the internal combustion engine, and an electrical drive system is added in parallel to drive the rear wheels. It was funded with £450,000 from the Department for Transport (DfT) through the Energy Saving Trust's low-carbon R&D programme.

Project leader Prof Nick Vaughan, head of automotive engineering at Cranfield University, said: 'This means you can operate the vehicle so the back wheels free-wheel as it would have operated before the modification, or you can leave the front part non-operational and just work with the electrical system at the back.'

The target range for the vehicle is 22km on electric-only operation. The battery can be charged either from the mains or through regenerative braking, where some of the kinetic energy of the vehicle is transferred to the battery when it stops, more like a conventional hybrid.

The researchers chose a Vauxhall Combo as their test vehicle because project partner Millbrook Proving Ground is associated with General Motors, and the Combo is a light delivery vehicle of the type the technology is aimed at.

ADDZEV uses a valve-regulated lead-acid battery rather than the nickel metal hydride (NiMH) or lithium ion (LiIon) technology used in conventional electric vehicles. It delivers 240V and has a capacity of 20A/hours.

'This project combines a hybrid mode with a zero-emissions mode, and the operating logistics of the battery have to be different for those two situations,' explained Vaughan. 'If you're driving in electric mode, you're using the battery through a wide discharge range — it can go from 80 per cent to 20 per cent of its full charge capability. In most hybrid vehicles, you're operating through a fairly small charge range, which places different demands on the battery.'

The innovative spiral-wound valve-regulated lead acid batteries used in the project are supplied by project co-leader and sponsor. the Advanced Lead Acid Battery Consortium (ALABC).

Allan Cooper, the European co-ordinator for projects at ALABC, said: 'A lead acid battery was chosen over LiIon or NiMH because it's cheap. Though significantly heavier, it costs a quarter to a fifth of the price of NiMH alternatives.

'In traditional electric vehicle operation, you're limited by weight. But the type of van we're converting is used for local stop-start deliveries, such as postal service or flower deliveries, where you're more limited by volume than by absolute weight, so we could afford a heavier battery.'

Vaughan added that the environmental impact of lead acid batteries is better than the alternatives. 'Because there are many lead acid batteries around, there's an existing infrastructure for recycling them, which doesn't exist for either LiIon or NiMH technology,' he said.

ALABC tested the lead acid battery by replacing the same size NiMH battery from a Honda Insight. It has so far run for 100,000 miles (161,000 km) with no problems.

There are five partners in the project including Cranfield, which is looking at the integration and control issues for the system and has overall project management responsibility, and ALABC. Millbrook Proving Ground is responsible for the mechanical construction of the vehicle and modification of the existing vehicle. Hybrid vehicle technology specialist Provector is developing the electronics for the battery management system and to drive the electric motor, and Oxford University is supplying the novel design of electric motors.

The team is completing the build of the electronics for testing with a motor. The next stage will be to assemble all the components on a frame, known as a 'mule', which has all the electrical drive systems mounted on it, so it can be tested on a vehicle dynamometer.

The project will run until March 2009, when the consortium hopes to deliver a mobile demonstrator that will work under electric-only power or under a conventional powertrain. Following that, the team intends to raise further funding to integrate the two systems.

Berenice Baker