This is not so much a race report as a summary of the entire year’s efforts, challenges, disappointments and successes. The culmination of all this activity was Australia’s WSC 2011, so in non-chronological fashion I’ll start there.
The most frustrating thing for a group of enthusiastic engineers is to have their efforts and aspirations thwarted by bureaucracy. But that’s exactly what happened when our shipping company refused to give us our container or even accept any form of payment. We spent an unproductive and relaxing two weeks in Darwin without a car to work on. However, what we achieved in the following fortnight after we finally got our hands on the car cannot be overstated. The car arrived in a “working” condition (we’d done some driving back in the UK at Bourn Airfield) but getting the vehicle race-ready took a huge amount of proverbial elbow grease and midnight oil.
We successfully fitted new lights and LED drivers, tested new driver controls and telemetry, performed solar battery charging tests and re-wired a few things that we’d never got around to in the UK, including the rear-view camera. The mechanical guys chipped in with a new set of wheels, worked out how to fit the Michelin tyres (and then taught a couple of other teams how to do the same) and fitted a brand new canopy. We painted the car and stickered her up with new sponsor logos, after BA successfully lost our first logos package somewhere between the UK and Sydney.
We always knew that testing was going to be critical to race success and not having the car for two weeks effectively robbed us of two weeks’ testing time. Despite this, we spent a couple of days out on the Cox Peninsula road just driving and practising convoy communications. I like to think of testing as deliberately causing problems so that they won’t happen when it actually matters. Pretty much anything that can go wrong in a solar car at some point will, and of all the things that can go wrong, the majority are electrical. The main problem that we “caused” during this testing period was battery related. One of our 5 Cell Management Modules (CMMs) decided to fail in a short-circuit state. These boards had until this point been doing a stellar job of keeping all 80 cells nicely balanced, but this fault destroyed two cells (and their two replacements) and meant we had to replace the CMM. Fortunately we’d brought two spare CMMs with us, unfortunately one of them didn’t work, and the other had an ID that conflicted with one that was still working. Some epic software bodging by “Batt-man” Ed meant we found a working solution. The CMM boards later threw regular over temperature faults and started physically shedding capacitors at an alarming rate. We fixed these problems as they appeared, but were nevertheless quite frustrated by such issues on supposedly reliable hardware. When you build a car, you half expect your home-made components to go wrong, not the stuff built by professionals.
We began the race quietly optimistic that we’d (perhaps) finish the 3000km on solar power. The first day we started fairly low on the grid after putting in a (sensibly) cautious qualifying lap at Hidden Valley due to concerns about the suspension and the new wheels. But when you’re not competing for the top 5 positions, grid position is relatively unimportant in a 3000km endurance race. We got off to a flying start and overtook the usual first hour breakdowns on the way out of Darwin. We had an exciting but (thankfully) uneventful few hours driving. The inevitable first problem occurred when the driver controls stopped functioning. It took the best part of an hour to work out where the problem was and find a solution. We fell back on an earlier version of the controls and carried on driving. Later inspection of the circuit would reveal that an inductor in the power supply had come loose causing total power loss to the steering wheel. The result of this fault was that we were behind our ideal race pace and would struggle to make Katherine (the first control stop) in time. What we failed to realise was that this was not critical and that we could have missed this control stop and perhaps adjusted our strategy accordingly for the following day. Instead we made the mistake of thrashing our car a bit too hard, driving at 20kph faster than we realistically could sustain. We ended up with what we assumed was a flat battery and were forced to trailer.
Another problem also contributed to our first day disappointment. Our telemetry system failed due to a blown fuse in the chase car’s 12V system. Another case of off-the-shelf components failing and lack of testing left us without good battery data while we drained a bit too much juice. As it turned out, the battery wasn’t completely drained, but one or two overly-discharged cells had triggered Low Voltage Protection (LVP). This fault was quite possibly a result of having to replace cells before the race because of the aforementioned CMM short-circuit issue. When a battery pack isn’t given enough opportunity to balance itself (which it wasn’t in this case) the entire pack capacity can be limited by only a few unbalanced cells. If the CMM issue had been triggered earlier with more testing, we would probably have started the race with a well-balanced pack and had access to a bit more capacity on day 1.
By now you might have noticed a common theme in my musings – we didn’t test enough. If shipping hadn’t been so problematic, we might have used our relaxing two weeks in Darwin more productively by (money permitting) spending several days driving the Cox Peninsula road in convoy.
By day two we’d established what went wrong on day 1, and put in place the necessary fixes. This required some proper Outback Engineering and the WSC observer looked on with a concerned expression as we fired up our generator and plugged various cables into the car. After we’d explained (across a slightly difficult language barrier) that we weren’t charging our battery but just powering a couple of laptops and a soldering iron he left us to it.
The rest of the race passed without major technical incident. From this point onwards we encountered all the problems afflicting every team: haze from a large bushfire on days 1-3, bushfires closing the road on day 3, strong crosswinds, lighting storms, quite a bit of rain, and the general lack of sunlight. Every encounter with other teams at control stops began with some engineers standing in a circle looking dejectedly at the clouds and pointing hopefully at a small patch of blue sky in the distance. Towards the end of the race we found ourselves doing a kind of “inverse storm chaser” manoeuvre where we’d trailer as fast as we could away from the bad weather and then spend a few hours at a rest stop where the sky would be lighter or (if we were lucky) we’d get 30 minutes of direct sunlight.
Squeezing every last ounce of energy from a solar electric vehicle is strangely satisfying, especially at the point in a solar race when everyone is resigned to not finishing on solar power alone and what really matters is the number of solar km covered.
So we finished the race in 25th position after covering 1487km on solar power alone. It’d be a lie to say that we’re completely happy with our position. Whilst better weather would almost certainly have enabled us to cover over 2000km, it would also have similarly improved the performance of the other 28 cars who also failed to complete the full distance. We were slightly unlucky to be caught at the back of the pack after day 1 as cloud cover advanced from the north and hit the slowest teams hardest, and we certainly had our share of bad luck with technical issues. But the fact remains that we lost over an hour to an electrical problem that would have been solved before the race if we’d tested more. The resulting sprint to Katherine cost us (and our battery) dearly, and if we’d driven more conservatively we wouldn’t have been forced to trailer on day 1.
One reason for our excessive energy use on day 1 is that our car simply weighed too much. The first half of the race was much hillier than any of us had been expecting and this took a heavy toll. Even with perfect weather, no technical problems, and perfect race strategy, it’s difficult to say whether our current vehicle is genuinely capable of finishing the race on solar power.
We began the year with plans to build a new car, but also with several thousand pounds of debt. Initial optimism, excitement and inspiration gave way to frustration as the decision was made to re-use our 2009 vehicle due to financial issues. This was clearly the right decision at the time – we might never have made it to Australia at all otherwise. To build a competitive solar car requires strong financial backing, and at the start of the year we simply didn’t have this. The other limiting factor is the time required. CUER is composed entirely of Cambridge undergraduate engineers. The Cambridge MEng is demanding and time consuming and where the best solar car teams in the world have a team of full-time engineers on an 18 month sabbatical from their studies, million dollar budgets and dedicated production facilities, we’re the equivalent of a few guys with spanners in a shed. With these constraints and the best will in the world (such as the 2009 team’s: they actually built a new car) you’re never going to build a world-beating vehicle.
Our solar car remains the best in the UK, an achievement we’re immensely proud of. But we recognise that we’re currently not going to beat the top Japanese and Dutch teams at their own game. The World Solar Challenge has made a handful of engineers across the world extremely good at building and racing solar-powered cars that have very little real-world use (but are damn good fun). It’s my personal opinion that CUER should adopt a very “Cambridge” attitude and build a genuinely innovative and perhaps slightly more practical vehicle. This isn’t an easy task and several conditions would make this easier, summarised below in my own personal wish-list:
• A bigger budget (we currently operate with roughly negative money…). This would probably require a large, dedicated business team and might include financial support from the university/department itself.
• A strong dedication of time from perhaps a 10-strong team of undergraduate engineers. Ideally a sabbatical year off the master’s course to concentrate on building the car.
• Dedicated lab space and facilities. Many teams have their own space to build their car. We beg, borrow and steal space from various labs and do a lot of our work in a car park at the back of the department. Other student-run projects in the department suffer from the same lack of facilities. It’s a pretty sad state of affairs when the best university in the world can’t support its own students in such fantastic projects.
Having one or two of the items from the above list would greatly improve our chances of doing something quite special next time around, especially considering at least half the 2011 team are remaining in Cambridge with either PhDs or employment. We’ve all got some fantastic ideas and the technical experience and know-how to put designs into practice.
Having completed the World Solar Challenge is no mean feat, and CUER can be extremely proud that it has now entered twice and still has a fully-functioning solar car. The battery is still workable, we have a robust wiring system, our old and battered solar array still gives us a good power output, and Douglas’s telemetry system performs admirably. Despite the issues, WSC was the experience of a lifetime for all of us.
