UK bus manufacturers lead the way in developing fuel saving technology, and they rely on a range of suppliers to help them realise real, in-service benefits. Avid Technology is one of them, and it has more in store than its well-known eFan. Tim Deakin reports.
Popular opinion holds that the UK’s manufacturing base has long since disappeared, but every day the domestic bus industry proves that theory wrong. It’s one of the world leaders in development of fuel saving automotive technology, and small businesses are just as important in these efforts as the big vehicle builders.
Based in Cramlington, Northumberland, Avid Technology is making a vital contribution to these endeavours. It can trace its history back to 2004, and founder and MD Ryan Maughan and his team continue to work hard to improve its current range and develop new products.
Best-known among Avid’s existing range is the eFan. As the name suggests, it utilises a bank of electric fans for coolant and charge air cooling in place of the conventional hydraulic installation.
â€œWe started out in 2004 by looking at the control unit of a hydraulic fan, and how we could make it more efficient,â€ he explains. â€œVery quickly we realised that removing the hydraulic aspect entirely and converting it to electric would be the best idea, but because of the heat exchanger design it wasn’t that simple. That meant we took a ‘whole system’ approach instead.â€
Removing the hydraulic circuit’s parasitic drag from the engine delivers a double-digit percentage fuel saving in itself, and the eFan gives several other efficiency benefits, says Ryan.
â€œYou don’t have to look too hard into investigation reports to see that hydraulic fluid leaks are involved in many bus fires. Our system removes the hydraulic system from the engine bay, and in most cases we also electrify the power assisted steering (PAS) as part of the installation, removing the need for any hydraulics on the bus.â€
Avid installs the eFan by removing the existing radiators and fan assembly and replacing them with a unit of its own design. The vast majority of buses in the UK market can be equipped with ‘off the shelf’ equipment held in stock, but in other cases Avid will produce a bespoke design to suit.
The bank of fans is mounted in front of the radiator core, and they activate as dictated by the control system. The new radiator unit is substantial, and stands up to jet washing from a reasonable distance. The fans also have a reverse function that allows accumulated debris to be removed in seconds.
So far so good: eFan’s appeal is not difficult to see, and besides its work with chassis OEMs Avid has retrofitted around 2,000 units into older buses.
But the ability to closely control the individual fans’ operation is important, particularly as the industry begins its movement to Euro 6, says Ryan.
â€œThe fans’ speed is infinitely variable, and we can cut them in and out individually to suit conditions. We can also turn them off completely, allowing the engine to warm up quickly, and then we can precisely control its operating temperature. That’s very difficult to do with a hydraulic system.
â€œRunning too cold during winter months is as big an issue for buses as overheating in the summer. We remove both problems, and raising operating temperature on colder days helps the diesel particulate filter and SCR system to work at their best.
â€œNot only that, but an engine runs at its most efficient only when it is at the optimum temperature. Our system can allow it to run hotter during the winter while increasing cooling capacity in summer months. Making the radiator core a lot easier to keep clean is also an aid to reliable operation.â€
An increase in cooling capacity is provided by the flexibility which comes with eFan, and it has proven its mettle in the demanding North American market. â€œIf the system is designed correctly it gives a considerably higher cooling capacity,â€ says Ryan.
â€œAdditionally, the traditional heat exchanger is square with a single fan. We can develop L-shaped heat exchangers thanks to design flexibility, which may be the best solution for the bus in question. We can also split the coolant and charge air radiators.â€
As part of the eFan’s installation process the electrical system in the bus is upgraded. PAS is converted to electric operation and this alone gives a fuel consumption reduction. A stand-alone kit for PAS electrification is currently being fine-tuned in a ‘guinea pig’ bus.
â€œElectrifying the steering also helps ready buses for stop-start operation. Having engine-driven steering in a start-stop application is not a good idea,â€ says Ryan.
The alternator is also replaced to satisfy the increased electrical requirement, and Avid installs one to its own design. It is more efficient than those fitted as standard and the subject of a number of patents.
â€œWe developed an alternator of our own because we couldn’t find one on the market which gave us the performance we need for the eFan,â€ says Ryan.
â€œOur alternator is more powerful, but it’s also more efficient. It’s a unique, brushless and maintenance-free design.â€
The alternator also has a major ace up its sleeve. Avid is finalising an installation where it can work in both directions, allowing the electrical system to inject a ‘shot’ of power into the driveline when the bus is moving away from a stop.
Unlike a diesel-electric hybrid driveline or a flywheel, the bi-directional alternator is not able to deliver torque on a prolonged basis. It is limited to a few seconds, but if engaged at the right moment there is a potential for useful savings at the most inefficient part of a bus’ drive cycle.
â€œPutting torque into the driveline requires a slightly different design of alternator, and the slack adjuster and belt drive must also be revised,â€ says Ryan. â€œIt’s a small electrical machine that can give a brief boost, but it has a significant fuel saving possibility.â€
Control is king
Even if the alternator is not used to inject power into the driveline, it is a fuel saver thanks to its greater efficiency than conventional examples. â€œWe can also turn it off under certain circumstances through our smart control unit, which helps,â€ says Ryan.
â€œDesigning suitable and intelligent control systems is one of the most important parts of any electrification process, and it is not a simple thing to do.
â€œBut we began the business in 2004 by working on control systems, and have developed from there.â€
A busy R&D department is working on the development of suitable control systems and further efficiency gains in the product line-up. Reducing the cost of the eFan unit is a priority, primarily thanks to operating circumstances away from the UK.
â€œeFan is already commercially viable here, where average bus mileages are considerably higher than in nations such as Germany. When mileages are lower the potential for savings are too, and we are conscious of that.
â€œBut any benefits which are driven by other markets will naturally be applied across the board, and UK operators will see the results as we drive down the ‘on cost’.
â€œAt the moment a hydraulic system is cheaper than electrification of the radiator fans, but the eFan is more cost-effective over the life of the bus. The long-term aim is for us to get to a point where the purchase cost of an electric system is below than that of a hydraulic set-up.
â€œThat would make it a complete no-brainer, and remove any remaining barriers that may exist.â€