Electric Evie

Published:  01 April, 2019

Europe’s first fully-electric truck-mounted sweeper from Johnston Sweepers is set to offer local authorities a zero-emissions street-cleaning solution to help tackle air and noise pollution, reports LAPV.

Sweeper companies are under increasing pressure to help authorities eliminate diesel and meet their clean-air targets, and many manufacturers now offer a range of alternative fuel options, including Compressed Natural Gas (CNG) and small electrically-driven machines. In the case of Johnston Sweepers, the company’s entire sweeper range is now also HVO-enabled (Hydrotreated Vegetable Oil), allowing the clean-burning fuel to be used as a drop-in fuel, or mixed with diesel to reduce hydrocarbons and NOx emissions.

It was against the backdrop of a move towards alternative fuels that Johnston’s design team made the strategic decision to develop what many did not believe was possible – a fully electric truck-mounted sweeper. A handful of manufacturers, including Johnston, now offer electric compact-sized (2m3) sweepers, but the size and weight of the batteries required to power a full-size truck-mounted machine meant that it had always been considered unachievable by the industry.

The plan was to launch the Johnston VE651, known as Evie (Electric Vehicle/Intelligent Electronics), as a proof-of-concept vehicle, primarily to assess the feasibility of such a machine and to gauge market interest. And, to prove that it could actually be done.

Clive Offley, who heads up Johnston’s engineering team, describes the complexity of the task. ‘We initially started looking at electrifying just the bodywork – the sweeper – but it didn’t make sense to mount it onto a diesel chassis, or to create a hybrid. Municipals are working towards banning diesel entirely, so to remain ahead of the market we set about designing a fully-electric machine, working in close collaboration with Emoss BV in Holland, which has 20 years’ experience of converting chassis.’

The primary objective was to develop the technology to maximise the sweeping range of an electric truck-mounted sweeper. ‘We wanted to prove that it is possible to deliver a full-size, 16-tonne sweeper, capable of operating a full work shift with routine overnight charging, giving local authorities the opportunity to make a real difference to air and noise pollution.'

Evie is a full-size truck sweeper mounted on a specially modified 16-tonne DAF chassis and powered by a high-performance 350kW electric motor. The battery driving the whole vehicle is a 200kWh Lithium Ion Phosphate (LiFePO4) battery pack, which was chosen for its balance of weight, power density, charge rate, and lower operating temperature, and because it requires no liquid cooling.

‘Once we had sourced the battery, we knew that it would offset the weight of the two engines and two sets of transmission used in a standard diesel machine, meaning that the overall weight and payload of the sweeper would remain the same,’ explains Clive. ‘The main challenge was to position the batteries away from all the sweep gear, so a special system was developed to mount them behind the cab where the now-redundant exhaust and air cleaner are located. We also needed to develop electric drives for the suction fan, and all the hydraulics and sweeper functions – more than a year’s work for our R&D team.’

The project required finding solutions for numerous highly complex technical challenges, but the outcome is a zero-emissions full-size sweeper with a six-tonne payload, similar to a diesel engine and designed to be capable of a full sweeping shift. ‘It proves our theory, and, unique to any comparable vehicle, Evie’s driving range is 200km at mid-loaded mass on a single charge, meaning it operates at less than 1kWh per kilometre.’

Clive adds that the machine produces zero exhaust and dust, and is virtually noise-free, the only sound coming from the airflow and the brushes on the road surface, so it is ideal for municipal sweeping. ‘It can work around pedestrians and residential streets without polluting the environment in any way, and then be recharged overnight back at the depot – exactly as we planned.’

The VE651 is fitted with two 22kW onboard chargers, giving a charging capacity of 44kW with a fastest-possible charging time of four to five hours. Charging cables are available as 16A, 32A, or 63A, and the sweeper can be charged from various standard 415V AC 3-Phase industrial sockets, or from a supplied charging post. The AC charging connector is a Type 2, capable of charging from any supply, including motorway services or street-side chargers.

Clive says that the battery is good for 3,000 full charging cycles. An onboard battery management system constantly monitors and maintains the temperature and health of all battery cells, balancing them without the need for liquid cooling.

‘All of the automotive functions of the VE651 are electrically-powered, as well as the sweeper fan, brushes and Supawash system, requiring no additional power input,’ says Clive. ‘It is this aspect of the design that we believe makes this machine the first of its kind in Europe.’

The complexity of the engineering work that has gone into the design and development of Evie led the machine to be named Bodywork Innovation of the Year in 2018 in the Commercial Motors awards ahead of its launch. The judges recognised its potential to provide a viable alternative fuel option for local authorities.

Meanwhile, the machine is currently undergoing engineering development testing, with fully-independent industry tests planned in preparation for taking the machine into full production. Initial trials indicate positive results, and Johnston’s engineering team is now confident that the VE651 is indeed capable of a full working shift, proving that what was once thought unachievable will soon become a reality.

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LAPV (Local Authority Plant and Vehicles) is the only UK information source purely dedicated to local authority vehicles and affiliated plant equipment. Appearing four times a year, it offers well-researched technical articles on the latest equipment/technology as well as in-depth interviews with key industry professionals. More...

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