Sébastien Buemi may be a familiar name to motor sport enthusiasts, in 2009-11 he drove for the Scuderia Toro Rosso Formula 1 team, and he is now making a name for himself in the fume-free environment of Formula E, the all electric premier motorsport series run by the FIA. After the first three rounds leading up to the Christmas break, Buemi leads the championship driving for the Renault e.Dams team. The series continues at the beginning of February 2016 in Buenos Aires and concludes in London in July.
Unlike F1 the current driver standings is not ordered in pairs according to the racing team. In F1 the relative merits of the car play a significant part in the results. In Formula E this is less significant – at this stage at least - as the cars fundamentally were the same in season one, with individual development of the e-motor, inverter and transmission allowed in the current, second season.
Built and designed by Spark Racing Technology, the cars have powertrain and electronics from McLaren, a chassis designed by Dallara, bespoke tyres from Michelin and system integration by Renault. At the heart of an electric vehicle contest is inevitably the battery and for this Formula E turned to Williams Advanced Engineering.
Ian Cluett is head of programmes and commercial at Williams Advanced Engineering and observed: “This level of co-operation historically is unusual in motorsport, but I think it’s needed those different organisations to pool their expertise together to develop a car in the time that was available.”
This journey began for Williams back in 2006 when it was announced that F1 would go hybrid in 2009. At that point the company looked at two different engineering streams. One was a magnetically loaded composite flywheel-based system. It was tested in an experimental Porsche GT car and Audi won Le Mans using it between 2012 and 2014 but it never raced in F1. There have also been trials with London buses in an attempt to improve fuel efficiency, but Williams took the technology as far as it wanted to and sold it to GKN in 2014.
Cluett continued: “What we raced in F1 was a battery based hybrid system with the energy storage mechanism, and then that’s gone through an evolution through Formula 1, through C-X75 [Jaguar’s concept hybrid vehicle] into Formula E.”
Like the first season, the second season of Formula E has a ‘series’ battery, meaning all cars use the same one. In fact two are used in each race as battery life is not enough to complete a race, so each driver has two cars, each of which will be raced for 20 minutes. In the reactive world of motorsport it has not been decided what will happen next year. Cluett commented: “The intention is that as we get to Season 5 we will have a single car race, but we’re pretty hopeful that Seasons 3 and 4 will run with a series battery - an enhanced version of the Williams battery. This season a number of the teams are running their own motor gearbox and inverter solutions, so you’ll start to get some powertrain differentiation.”
Given this competitive and increasingly open development environment, Williams is understandably cagey about the precise technology within the batteries beyond ‘lithium-ion and other cell technologies’. However patent applications for both thermal management system and battery case technology are indications that this has been a big evolutionary step for the design team.
The car itself accelerates from 0 - 100 km/h (0-62mph) in 3 secs and can reach a top speed of 225 km/h (140mph) – more than enough for the city centre circuits that Formula E is raced in. There are very few of the long straights that feature in F1 circuits and the city environment was specifically chosen so that Formula E was not just fun and technically challenging, but also relevant to the future of urban transport.
Achieving these specifications required a maximum battery of 200kw (equivalent to 270bhp). This is only used for qualifying. In race mode the power is limited to 150kW with an additional ‘FanBoost’ of 30kW allowed for 5 secs per car.
Developing a battery to meet these criteria was not easy, particularly given the timescales. Williams were bought in late to the process after the initial battery developer pulled out, giving Williams only 12 months for the whole design, development and test cycle.
Design of the battery has been almost entirely down to the Williams team. Cluett said: “The FIA have become involved through crash safety - they set the crash standards for batteries in racing series. And then also we use calibrated FIA sensors to monitor current and voltage - therefore power in and out of the battery - to ensure everyone’s got an equivalent amount of energy they can use. So that’s where the FIA has been involved. Within the battery itself, it was all down to us.”
Cluett continued: “It looks like a relatively straightforward box, but the box itself is stress member. It is part of the chassis of the car. It bolts onto the crash cell at the front of the car, and then the gearbox and the motor hang off the back of the battery. So the case itself takes quite a lot of stress during a race cycle. It’s got something like 4500 parts inside.”
Given the complexity of these units, Williams Advanced Engineering has had to develop a specific battery build facility for this project, at a peak there was up to 20 people manually building the batteries. In the interests of uniformity and therefore fairness, each battery had to be exactly the same, so four cells dedicated to testing Formula E batteries were set up , each capable of testing up to 300kW/1000V/800A.
“The essence of the series is really all about how you use energy,” concluded Cluett “So each driver has a fixed amount of energy, it’s up to them how they use that. Anything they can regenerate through braking is free, effectively, that just gives them more energy to use to drive the car forward. We’re seeing many different strategies being used within the race series, and I think this would drive some of the developments within electric cars as we go forward in the next few years.”
Presumably this is not intended to encourage driving like Sébastien Buemi round city centre streets at 140mph, but there is increasing evidence it becoming more viable.
 Renewable racing Racing electric cars only demonstrates environmental benefits if the electricity to charge them is generated without the associated by-products of burning fossil fuels. For this reason Formula E has signed up to RE100, a collaboration of major organisation who have publicly committed to working towards using 100% renewable energy. During the first year of the championship, Formula E powered its electric race cars with renewable electricity using an innovative zero emission fuel glycerine to run a generator. The new technology is called ‘Aquafuel’. The generators are based on standard production diesel engines that have been adapted with Aquafuel’s patented technology to run on glycerine. |
