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2015 Bridgestone 3022km, powered At 8 AM on Sunday, October 18th, the first of 42 cars from 25 countries left Darwin in the Northern Territory for the ~3000km drive to Adelaide, South Australia. The leaders would cross the finish line just four days later – but they didn’t use one drop of fuel in the process. As competitors in the Bridgestone World Solar Challenge 2015, they used the energy from the sun to power their journey south. T he Bridgestone World Solar Challenge is much more than just a 3000km race for solarpowered vehicles. Sure, winning the race itself is the ultimate prize but simply getting the car to the start line is arguably 90% of the effort (and cost). This is simply because every team has spent thousands of man-hours in designing, building, testing, rebuilding, retesting and finetuning their entry, long before they get it anywhere near the “track” – in this case, the entire length of the Stuart Highway, in sometimes 40°+ heat and Red Centre dust! Every car (and that’s a term that’s arguable!) is different, reflecting the team’s philosophy and budget. Most teams are drawn from universities and colleges, where the World Solar Challenge entry brings together several faculties in a spirit of cooperation: • Electronic and electrical engineer- ing, of course, for virtually all cars have quite comprehensive (and unique) computerised control and management systems which not only determine how the energy is derived and used but reporting back in real time to their support vehicles.   Virtually all competitors had quite sophisticated radio links back to their support vehicles which not only relayed telemetry to the support crew but allowed two-way How about some more technical details? We’d love to bring you some of the more specialised technical information on the cars in the 2015 World Solar Challenge . . . but this information was difficult, if not impossible, to obtain, It seems the entrants were all playing their cards VERY close to their collective chests, mindful that any information they might supply could be used by their opposition when they return for the 2017 World Solar Challenge. Yes, most teams will be back – the 14  Silicon Chip comments on social media were particularly enthusiastic, not just about the organisation and conduct of the race itself but also the camaraderie and co-operation between teams, the social aspects (especially the social aspects, after all we are talking about university students in the main!) and, not the least, the stunning Aussie outback scenery and weather. One commented that he would never have believed there were so many stars in the sky if he hadn’t seen them himself. Another waxed lyrical about the amazing sunrises and sunsets in the outback. As a spectacle, apart from the start and finish the Bridgestone World Solar Challenge doesn’t offer too much: 46 teams spread across thousands of kilometres of outback road, going past at maximum possible speed. But for those who competed, and for all those overseas following the race via the net, it is one of the most fantastic advertisements for Australia you could hope for! siliconchip.com.au World Solar Challege: d by sunlight by ROSS TESTER Stella Lux, the energy-positive family solar car from Dutch Solar Team Eindhoven drives through Devils Marbles Conservation Reserve on day two of the 2015 Bridgestone World Solar Challenge. Photo: TU Eindhoven, Bart van Overbeeke communication between support crew and driver. “Road Train Approaching” was enough to put the drivers’ collective hearts in their mouths! • Computer sciences: some teams use off-the-shelf equipment from their sponsors, tailored to suit the exacting requirements of the challenge. But just as many design and build their computer equipment, then write the software required for their car.   The top crews had every aspect of car operation – and even the driver’s state of health – monitored at all times. • Mechanical engineering, which is largely responsible for the design and building of the vehicle itself. Some have access to wind tunnels; others have to rely on the theory that they have been taught. In all cases, students were responsible for building and refining their designs to come up with “the” racer which could be the Challenge winner. • Business studies, responsible for siliconchip.com.au raising the rather significant funds required for a serious attempt on the World Solar Challenge. While in most cases they can rely on some support from their own school, all are most reliant on sometimes millions of dollars worth of sponsorship.   One leading team had no less than 113 sponsors listed, mostly re- lated to some aspect of the attempt. Some sponsorship is in kind, where state-of-the-art equipment (eg, solar panels) is supplied either free or at a substantial discount. • And finally, the students themselves – in virtually every case, they had to raise the funds to get them a place in the team and the Stanford University’s “Arctan” crossing the “Ghan” railway flyover in the Northern Territory desert, followed by their chase vehicle. We are assured they had nothing to do with the bent guard rail! December 2015  15 The “Cruiser Class” aimed to replicate, as much as possible, a race-competitive vehicle that could be used on the road and rely solely on solar power. This publicity shot, from the Dutch Solar Team Eindhoven and their four-seat “Stella Lux” demonstrates just that. The Stella Lux was no slouch in the race, coming second in the class, 13 minutes behind the winners. “working holiday” to Australia.   For many students coming from Northern Europe or Northern America, the central Australian climate, even in October, was something of a shock to the system. Classes There were three classes in the race: Challenger class, which had highly aerodynamic single-seat cars built for speed and range, not for comfort (the type of solar racers you’re probably used to seeing); Cruiser class, where cars were built for practicality – as closely as they could mimicking your typical passenger cars with up to four seats; and finally Adventure Class, not quite a “beginner’s” class but one which allows teams to enter which may not have the (sometimes huge) financial backing of the other classes and in some cases do not comply with the technical requirements of the other classes (though they must meet all safety requirements). There was a further class allowed for Is it sunrise . . . or sunset? Regardless, teams oriented their vehicle’s solar panels (in most cases taking them right off) to catch the absolute maximum sunlight possible to charge batteries before the 8 AM start deadline or after the 5PM finish deadline, ready for next day. Here the “Stella Lux” team manoeuvre the solar panels into the best possible position. 16  Silicon Chip siliconchip.com.au Where the Challenger class was built for speed, the Cruiser class also added comfort and convenience, even to the large LCD screen. Photos above and opposite: TU Eindhoven, Bart van Overbeeke. under the rules, the Evolution class, which had less restrictions placed upon, for example, energy sources and capacities but this year there were no entrants in that class. Challenger class This class is arguably the toughest to enter because the competition is so intense. Each vehicle is designed for sustained endurance and total energy efficiency. The overall winners of the 2015 World Solar Challenge came from the Challenger class, if only because they were the fastest on the road. (Actually, the rules stipulate that the Challenger class winner will be declared the over- all World Solar Challenge winner). Unlike the other classes, which have a compulsory overnight stop in Alice Springs (where they can recharge from the grid if necessary – and usually do!) the Challenger class is a “one stage” event, travelling direct from Darwin to Adelaide. The vehicles rely on their solar TAFE SA’s “Solar Spirit” competed in the Adventure Class. This car has actually been in existence since 2010 and competed in the 2011 and 2013 challenges. There are no “big dollars” behind the team; it used off-the-shelf componentry and ingenuity instead! siliconchip.com.au December 2015  17 others rely on electronic systems (or both). Managing . . . everything! While the World Solar Challenge offers a very useful test bed for IBM's forecasting technology, it could have much wider implications. The winning Dutch teams had similar technology, courtesy of Philips. panel installation to both power the drive motors and to charge the (limited) on-board batteries, which help keep the vehicle moving during cloudy periods or under shade. No vehicle is allowed to compete at night. Driving is as carefully managed as power: it’s a race, but if the vehicle is driven too fast extra energy is used and the batteries will be depleted. This year, Challenger class vehicles are slightly shorter than in previous years at just 4.5m maximum. They also have a maximum width of 1.8m. Into this must be packed a solar array of 6m2 maximum (or just 3m2 maximum if using GaAs cells). Similarly, there is a limit to the mass of on-board batteries allowed – with Li-ion and Li-polymer they can carry up to 20kg, LiFePO4 40kg, NiMH 70kg and lead-acid 125kg. We don’t believe any vehicle carried the heavier batteries. There is only room for one driver, who must have a minimum weight of 80kg (or carry ballast to meet this minimum). Up to four drivers are permitted, each with that same 80kg minimum/ballast and each must have had at least 12 hours of logged driving in their team’s solar vehicle. All drivers must be licensed in their home countries. The vehicles may not start to race before 8 AM and must be “parked”, almost always on the side of the road, by 5 PM. Every team has a lead and chase 18  Silicon Chip vehicle, with one seat given to an official race observer who ensured that competitors play be the rules. For example, every minute on the road before 8 AM or after 5 PM will be penalised 10 minutes in overall time. They were also looking for bad or unsportsmanlike driving, eg, deliberately holding up a team trying to overtake. Unlike some vehicles in other classes, Challenger solar cars must have four wheels. There are new requirements in the 2015 race for improved driver vision in all directions – some use conventional mirrors for rear view, Extreme importance is given to solar energy management and engine management. The rules are quite specific on how this is to be done, with extensive and compulsory documentation required. Another important part of the rules is driver safety – each vehicle must have emergency power disconnection accessible from both inside and outside the vehicle and every team must have a safety officer and a battery officer who are responsible for ensuring driver, team, other road users and public safety. The rules and regulations for the race are detailed in a 44-page manual. Every aspect of vehicle construction and its fittings are covered; for example solar cells, batteries, brakes, steering (even the type of steering wheel), seatbelts, tyres, wheels and so on. Every vehicle competing in the race must present a roadworthiness certificate from their home country but also undergo extensive mechanical, electrical, construction and safety scrutineering before the race starts. Vehicles failing this scrutineering are not allowed to compete. Cruiser Class Cruiser class “aims to change the way we think about what we drive and what fuels we use”. The Coates Hire Car Tracker gave vehicle positions, courtesy of their GPS systems, theoretically in real time. The inset shows the first five cars to finish in Adelaide – Nuna8 (No.3, parked in King William St), took the honours. siliconchip.com.au The class was established in the 2013 race, in which one four-seater “family” car travelled the 3000km race route using just 64kWh of external energy (ie, electricity) input. If this doesn’t excite you, a very efficient modern petrol car travelling the same route would use an energy equivalent of around 5000kWh! Cruiser class vehicles are designed for practicality and as well as being judged on this will also earn points for the time taken to traverse the course, external energy use (or more particularly lack of it) and payload carried. These vehicles are, to some extent, seen as the fore-runners of the electric vehicles which we will all be driving tomorrow. Most of the requirements of the Challenger class must also be met by Cruiser class vehicles. As mentioned earlier, one big exception for the Cruisers is that it’s a race of two halves – Darwin to Alice Springs and Alice Springs to Adelaide. During the compulsory night stop in Alice Springs (close to the half way point) Cruiser class vehicles can be recharged from the grid. Triple the battery capacity is allowed under Cruiser class than Challenger class; 60kg for Li-ion or Li-polymer and 120kg of LiFePO4. Cells may not be removed unless in a hazardous situation but packs can be removed (eg, at night) but must be locked away under direct supervision of the team observer. No grid recharging is allowed except for the designated night stop above. Adventure class There were only three entrants in the Adventure Class, and one of those didn’t quite make the distance! Both finishing teams came from the US: The Liberty Solar Car team’s car, the Solis Bellator, came from the Liberty Christian School from Argyle, Texas, while the Houston Sundancer was entered by students from the Houston School of Science and Technology. These teams, while highly skilled and professional in their own right, do not have the immense backing of many other teams (ie, the Challenger and Cruiser classes) and in many ways is seen as a “stepping stone” to get into the top classes in future events. While the winners were celebrating with an impromptu dip in Adelaide’s siliconchip.com.au The Philosophy behind the Development of the Classes By Chris Selwood, Event Director Primarily a design competition to find the world’s most efficient electric car, the biennial World Solar Challenge seeks to inspire some of the brightest young people on the planet address the imperatives of sustainable transport.  The original and largest event of its type, it maintains its position by offering an adventure of epic proportions: crossing a continent in a single stage using only sunlight as fuel. Every two years, teams from around the globe work tirelessly to design and build an ultra-efficient electric vehicle, bring it to Australia and, in the spirit of friendly competition, prove their concepts in one of the world’s harshest environments; the Central Australian Desert.    The philosophy of evolving design parameters and creating regulations around what must be achieved, without dictating how they are to be achieved, not only encourages creativity and lateral thinking but provides a unique opportunity of engaging with some of the issues which face us all and a philosophy which has led this famous international event to its position of global dominance. This openness has fostered the innovative strength of thought that continues to come to the fore as teams look to create the ultimate efficiencies in energy capture, storage and conversion. The World Solar Challenge may have the sun as its nucleus but its innovation reaches into many other areas such as advanced composite materials, low rolling-resistance tyres and innovative power-electronics capable of ultrafast switching of the high current inductive loads demanded by modern EV powertrains. When first devised, the solutions were only limited by the imagination, although practical considerations were soon to drive the regulations. If solar cars were to drive on public roads, they should be of an appropriate size. If the cars were truly solar powered, there should (for the purposes of a competition) be a limit on the stored energy they brought with them.  So, based on the admittedly somewhat fanciful notion that we, as humans, each have 8 square metres of the earth’s surface from which to draw our sustenance, solar collectors (not defined by type) were originally limited to 8 square metres, however with more efficient conversion leading to faster cars, this was dropped to 6 square metres in 2009 and, in 2011, space grade technologies such as Gallium Arsnide were limited to 3 square metres. Energy storage limits, again for the sole purpose of competition, “retained to this day” a relationship to the power required to complete the course and, as far as we are aware, the World Solar Challenge is the only event which does this. Based on a reference point that if a one kilowatt car could complete the course in 50 hours, we consider it reasonable to allow 10% of the energy requirement to be stored to assist with hills, clouds, or extra acceleration for overtaking. Thus a nominal figure of 5kW was, and remains, the original determinant of the allowable mass of batteries, and the basis of the current calculation by class. Rapid advancements in technology coupled with a growing acceptance of the imperatives of environmental action require constant review and evolution of the design parameters required to keep the Challenge both attractive and relevant. Experienced teams need to be pushed in order for innovation to flourish, but at the same time the tasks should not be seen as impossible by newcomers. Motivators also change with time. At one end of the scale we have young people inspired to attend by what they read and saw as children, and seek the adventure. At the other, the brightest students take a two-year sabbatical to immerse themselves in the project thus gaining wide ranging experience beyond campus life. The world is also changing. In early events there were few reference points for home made vehicles or regulations for electric cars. This led to to the development of road protocols and safety regimes specific to the event. That these were adopted by other events proved their efficacy. Now the developed world recognises myriad regulations for “individually constructed vehicles” harmonised by the UNECE. The Institute of Electrical Engineers has set wiring standards of electric vehicles, and transport authorities around the world are reacting to the rapid developments in urban mobility and the technology which drives it.  The World Solar Challenge: Adventure. Innovation. Achievement. December 2015  19 Armed with this, they were able to pass information through to the driver on, for example, any cloud build-up, its direction and speed, so the driver could either try to outrun the clouds or slow down and let the clouds pass. Follow those cars. . . maybe Another shot of the crews, this time from Michigan University’s “Aurum”, working hard to get the last photon of sunlight into the solar cells. The two guys with spray bottles of water employ the only method of solar cell cooling allowed. Victoria Square Fountain, the two Adventure class vehicles had not long crossed from the Northern Territory into South Australia. Active forecasting When seconds count, the teams grab any possible advantage that’s within the rules. As you would realise, the solar cells work at maximum efficiency in bright sunlight – any shading can drop the output significantly. And that includes shading from clouds. At least two teams, the Aurum (University of Michigan) and the Stella Lux (Solar Team Eindhoven) featured advanced solar forecasting capabilities through deals with their sponsors – IBM, in the case of UM and Philips, for Stella Lux. Both teams were able to obtain instant weather information while travelling, which was combined with historical data for the route. Coates Hire sponsored what was supposed to be a real-time display of all entrants which could be called up on line. It nearly worked . . . except for the times when the GPS data (and therefore the location) was hopelessly out of date (up to 12+ hours out) and, in some cases, simply wrong because of a glitch. For example, at the end of race time (5 PM) on the second-last day, the map showed the leaders in Port Augusta, SA . . . whereas at the start of the last day (8 AM) they had just 177km to go. Hmmm. But we’re assured the positions shown at the finish are correct – and there are plenty of photos to prove it. And the winners were: The 2013 winners, Nuna7 from the Nuon Solar Team of Delft University in the Netherlands, returned with an even better car, the Nuna8, to defend their world title. And defend it they did, taking out the Bridgestone World Solar Challenge in a time of 37:56:12. Even on day 1 of the race, the pace was on. But it took until the fourth day for Nuna8 to take the lead, then hold off their main rivals, another entry from the Netherlands, to claim their sixth victory in the race! Second place was the Delft University’s Solar Team Twente’s “Red One” which pushed Nuna8 all the way, never more than a few kilometres behind. Its official time was 38:04:32. Winners are grinners . . . and wet! Here the support team for the Nuna8 is lifting the the solar panel “lid” off the car once they had passed the “ceremonial” finish line. Actual timed finish was outside Adelaide to ensure traffic congestion wouldn’t influence the official positions but cars still had to make it to the Victoria Square finish line. At right, Nuna8 team members take a ceremonial “paddle” in the Victoria Square fountain. 20  Silicon Chip siliconchip.com.au Winners of the Cruiser Class in the World Solar Challenge, the “Owl” from Japan’s Kogakuin University. All teams were required to have a trailer for this purpose. Some of those “trailers” were more like mobile workshops. When they didn’t meet the stage deadline, cars were given a lift to the next control point ready for next day’s competition. Naturally, trailering cost the team significant points in the overall competition using a distancebased formula. One team, the Durham University’s “DUSC2015” (UK) actually recorded a negative distance under solar power against 1495 kilometres of “trailering” when they reached Alice Springs! Surprise . . . they were coming last! Well, Third place went to the Tokai University (Japan) entry, the “Tokai Challenger” at 38:50:07. In the Cruiser class, it was a race in two: Kogakuin University’s “Owl” (48:07.00) and another Dutch team, the Solar Team Eindhoven in their four-seater “Stella Lux” (48:54:59). Incidentally, the Stella Lux earned pole position at the start of the race by taking out the time trial at the Hidden Valley racetrack but the Owl crossed the finish line nearly an hour ahead of Stella Lux in Adelaide. During the race, Stella Lux achieved the remarkable feat of travelling 1500km on a single battery charge! Australian competitors Considering the enormous amount of support – dollars and otherwise – that many of the overseas teams enjoy, Australian competitors didn’t fare too badly. In the Challenger class, Clenergy TeamArrow and their Arrow1-GT were in eighth place (45:22:00), two ahead of the Western Sydney University’s “Unlimited” (46:51:00). The Adelaide University’s “Lumen” was further back again (55:42:00) but travelled 35% of the race on their trailer. Even better results were achieved in the Cruiser class, with the UNSWSunswift “eVe” coming in third in 55:28:44. The popular “tunnel” design, for aerodynamic stability, is demonstrated in this front-on shot of the second-place getter in the Cruiser class, Stella Lux. – was required because of equipment failures or other “on the road” problems (including, for example, running out of power). maybe not quite last: Siam Tech1’s STC1 (Thailand) was withdrawn from the race and India’s RVCE “Soleblaze” didn’t even make the start line. Trailering Only five of the Cruiser Class managed to complete the course without requiring assistance in meeting stage deadlines. All bar seven of the Challenger class managed to compete under their own power. Usually this assistance – “trailering” siliconchip.com.au The University of Michigan’s huge “Car Trailer” – capable of not only holding the car but was also a mobile workshop with all equipment the team could ever possibly use . . . and let’s not forget those vitally important sponsors! December 2015  21 Well, a few things we have learned about Solar Challenge cars . . . Earlier we mentioned that it proved rather difficult to find any information on what equipment the cars were using... apart from general information, such as the winning Nuna8 sported 391 monocrystalline silicon cells offering an impressive 24% efficiency; that the body was a carbon fabric/foam sandwich, similar to that used in formula 1 cars; that it had 96% efficient Mitsuba engines integrated into the rear wheel rim and that it was aerodynamically shaped to improve road-holding and stablitity. We also found more details on the 2013 winner, Nuna7 (on which Nuna8 was closely based). [See below] That was about the limit of data, until we found the photograph at right of an unidentified 2015 Bridgestone World Solar Challenge car’s control equipment. Together with a magnifying glass, we were able to identify at least some of the componentry used and make some educated guesses on what we think was the make-up. For example, the fact that there are three blue boxes on the right side of the picture and three inductors on the left automatically suggests that the motors being used were three phase – just as we would have expected. We know (from previous races) that the majority of these were “pancake” type motors which pack an enormous amount of grunt for their size. We also know that the motors are extremely efficient – the (albeit limited) spec sheet for the Stella Lux, for example, claims a high 97% efficiency. Efficiency is absolutely vital when you’re running the motors from a supply limited by what you can generate from the sun (in many cases, it was reported that onboard batteries were exhausted or near exhausted during the Nuna7 (2013 Winner) Specifications Dimensions 4.5 x 1.8 x 1.12m (l x w x h) Weight 180kg Driver Weight supplemented to 80 kg Wheels 4 Solar Cells 392 Motor InWheel Direct Drive Electric Engine Integrated motor in rear wheel Efficiency 98% Battery 21kg Lithium Ion cells Capacity 5.3kWh Body carbon fibre and foam sandwich construction Aramid reinforced parts Titanium roll bar Aerodynamics Specially designed wing profile Revolutionary asymmetrical design Tested and proven in the windtunnel Suspension Aluminium uprights, hold by aluminium leading arm below with single A-arms of carbon fiber Integrated dampeners in suspension Lightweight magnesium rims High precision ceramic bearings Titanium axles Tyres Low resistance profile tyres specially developed with Michelin for solar racing Brakes Regenerative braking with the electric motor Rolling Resistance > 10 times less than a conventional vehicle Air Resistance > 11 times less than a conventional vehicle Telemetry Wireless connection with support vehicle Support vehicle determines the speed of Nuna using touch screen application 22  Silicon Chip day – the cars were running on what the sun provided). WaveSculptor 22 Motor Inverter Specifications WaveSculptor 22 Inverter Peak Power Rating: 20kVA Average Power Rating: up to 20kVA with water cooling But one of the more interesting Motor type: 3-phase permanent components we magnet (BLDC) or induction identified is that Cruise Efficiency: 99.2% large-ish orange Cooling Method: cold plate and black box in the middle of Maximum Battery Voltage: 160VDC the picture. It’s Maximum Motor Current: 100A rms a Wave-Sculptor Drive Waveform: Sinusoidal 22 Motor InvertCommunications: CAN bus er, one of a range of products from Size: 255 x 165 x 35mm Brisbane-based Mass: 855g Tritium Pty Ltd (www.tritium.com.au). A quick check of their website showed that this was indeed the inverter of choice, claimed to be “used by nearly all leading solar racing car teams worldwide . . . “. According to the manufacturers, the WaveSculptor 22 is one of a family of inverters. This one is a high-efficiency, low weight, 3-phase 14kW variable frequency inverter especially designed to drive high-efficiency, low-inductance, permanent magnet motors The suite of firmware, software and ancillary products that form the WaveSculptor drive system work together to make the motor controller easy to configure and compatible with a wide range of electric motors. The WaveSculptor 22 is not cheap at $AU6000 plus GST. However, given the number of Solar Challenge teams investing in one of these Australian-made and produced products, it seems that they all believe they represent good value for money. Each WaveSculptor 22 is supplied with a motor position/temperature adaptor, a CAN-Ethernet bridge, power adaptor and a 1m CAN cable. For more information on the Tritium WaveSculptor range, contact Tritium Pty Ltd, 16 Cavendish Rd, Cooparoo, Qld 4151. Tel (07) 3129 4389; email enquiries<at>tritium.com.au SC siliconchip.com.au