It’s not immediately obvious to many people that solar cars should have batteries. If you get all your power from the sun, why do you need to lug around all that extra weight?
There are several reasons for having a battery in a solar-powered car, and most are inter-related.
- To be able to operate when there isn’t any sunlight
- To decouple the car’s performance from the instantaneous weather conditions
- To provide a stable high-voltage bus to drive the motor, and “hang” the rest of the electrical systems off.
The WSC 2013 regulations permit solar vehicles to carry an energy storage system (in this case a battery) whose maximum allowable cell mass depends upon the chosen cell chemistry. If you use lead acid battery cells (the type you’ll find in your car at home) you’re allowed up to 125kg in Challenger class. If you choose to use lithium ion battery cells (the type you’ll find in your laptop) you’re only allowed 21kg. Why the big difference?
Lithium ion cells are extremely energy dense. That means there’s a huge amount of energy stored inside a small mass (and a small volume). The aim of the regulations is to make sure that …
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When was the last time you thought about light? As our designs are progressing quickly from wacky ideas to a full race vehicle, light is something that we’ve all been thinking about increasingly: “How can we track the sun better to get a bit more light?”; “How will light affect the temperatures inside the car?”; “How will the car perform under harsher Australian light?”. However, it occurred to us last week that not many people actually stop to think about the stuff that is everywhere and all around us: light.
Last week was the first ever E-Luminate Festival. This was a five-day light festival in Cambridge, celebrating the collaboration between light and clean technology. Dotted around Cambridge were greenhouses, churches, streets, shop windows and even parts of the Grand Arcade Shopping Centre, all bathed in beautiful light displays and light based artwork for five days to celebrate the festival.
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After all the hard work that goes into slowly piecing Daphne together, it was great to find a prestigious establishment like the London Science Museum approaching us and expressing an interest in our project.
Each half-term, the museum puts on an event called Antenna Live, a hands-on exhibition where the most current and innovative ideas from science and technology are gathered and their concepts shared with museum visitors from around the world. This time the event will be held from the 8th-10th of March and exhibitioners can be expected to engage with up to 3000 members of the public per day, so we were delighted when the Museum asked us to get involved! Having kindly been invited to showcase our project, this weekend myself and fellow first-year Lucy Osborne were over the moon to accept an invitation to go down to the museum, in order to have some communication and media training prior to the event.…
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Tesla, the electric car manufacturer, has once again hit out at media misrepresentation of its technology. After the New York Times published an unfavourable review of its Model S and the corresponding fast-charge infrastructure set up along Interstate 95, Tesla engineers grew suspicious and compared the data logs from the test drive to the reviewer’s comments. According to the article, the Tesla’s battery capacity wasn’t enough to sustain it between charging stations. Despite following advice from Tesla’s customer service helpline, the author, John Broder, found himself stranded on empty at several points during the trip, and at one point even had to be towed to his destination. Overall, it’s a dim read.
However, in a blog post published on the Tesla website, CEO Elon Musk points out that the data records of the drive (also provided) tell a different story. State of charge data shows that the battery was never fully depleted at any point, and that Broder seems to have deliberately cut short recharging times, against the advice of Tesla officials. Tesla claims that Broder continued to reduce the charging time despite repeatedly having insufficient range, and, most alarmingly, they note that at one point he appeared to drive …
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Finally, it’s Christmas! After managing to endure the whirlwind of my first 8 weeks at university this is a welcome chance to have some time out, revise and of course, reflect upon the fantastic opportunities that this intense term at Cambridge has provided me with. Yet looking back I can honestly say that, amongst the inevitable torrent of highs and lows, the best part for me was without doubt signing up to CUER.
Having naively joined the team on a whim within my first 2 weeks of studying, I was very uncertain of what to expect. I had comparatively minimal engineering experience, was pretty sure I would be the only girl present and felt as though I would probably be rendered useless to the team. It’s fair to say I could not be more wrong! Although initially daunting, sitting in my first mechanical team meeting surrounded by such a mixture of incredibly bright, passionate people soon brought me to the realization that I’d made a great decision.
To this day, the team spirit is a main contender as to why I have enjoyed my time with CUER so much. The genuine buzz and excitement surrounding the new ‘game-changing’ design was …
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If only the sun didn’t move.
One of the factors limiting the efficiency of photovoltaic arrays is the motion of the sun across the sky, so that the angle at which sunlight strikes the solar panels varies. The ideal configuration for a solar array is to be angled perpendicular to the ‘direction’ of the sunlight. This becomes difficult to achieve when the location of the sun is continually changing. Ideally, we’d like the sun to just hold still. However, since we can’t change reality to accommodate our technology, we must instead change our technology to accommodate reality.
Traditionally, engineers have dealt with the issue of a moving sun by introducing solar tracking: using mechanisms to adjust the orientation of solar panels to follow the sun. These mechanisms have been around for a while – astronomers use a similar approach to allow their telescopes to follow the motion of the stars. However they can involve complex combinations of gears and motors, which require power to operate, and this cuts down the net output of the solar array.
This is a phenomenon that has not gone unnoticed by solar vehicle engineers. Since the very first World Solar Challenge in 1987, there have …
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It is finally here, launch day. The day that you finally get to see what we have been working on for the last 5 months! Getting to this point has been a huge effort from everyone on the team and a huge effort is still required to get the final car to Australia. I will write a blog post in due course explaining how we came up with the concept, explaining my CUER story from start to where we are now, but for today I will just fill you in on the work done this week (with a few photos from the last few weeks that I have been keeping under wraps.
To start with I would like to welcome three new sponsors to CUER who are supporting the mechanical team, Matchtech Engineering Services, Mackays of Cambridge and Moore and Wright.
Matchtech Engineering Services are an engineering consultancy, specialising in structural analysis and design. I first met the managers of their team during my Year in Industry before coming to Cambridge. They are IMechE registered mentors and their skills developing new talent in the work space are fantastic. They taught me a huge amount of engineering during …
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Week five of a term at Cambridge is traditionally the hardest week of term. The initial excitement and energy that lets you do far too much at the start of term wears off. The draw of Christmas, of rest the end is not quite tangible enough to just let you power though. The term ”week 5 blues” is often coined.
It was perhaps a slight oversight on my part to plan the most labour intensive week of our term for week five, but more by luck than judgement it turned out to be a stroke of genius.
Gluing together modelling board was a fun and sufficiently mundane task that everyone, stressed out by academic work, found it a therapeutic escape. With a total of 35 helping out at some point during the week, no individual had to spend too much time on the task and it was therefore the perfect team building activity.
The modelling board has now been delivered to JLR and the machining work is about 50% complete. I will post photos of this process after the design launch on 24th November.
Modelling board was not the only thing going on this week. Embodiment design progresses and logistical …
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Apologies for not making a blog post last week, the mechanical team has had a very busy fortnight. Read on to find out what we have been up to!
Just over two weeks ago, the composites layup team made their second batch of carbon fibre/ honeycomb core sandwich panels. These are to be used as supports for the mould for the car. The team showed that their layup skills were improving, with the quality of the panels remaining high without supervision from the more experienced members of the team.
The ergonomics team also set to work two weeks ago, building a basic cardboard model of the internal bulkheads of the car. This demonstrated that a few very minor changes to the design could be made that would not affect performance, but would improve the comfort of the car for the drivers. This once again helped the team to appreciate the scale of the car in a form more real than on a computer screen. This team them used the updated model to begin assessing the optimum position within the car for the driver controls. Lessons learnt from talking to drivers of our old car Endeavour, are applicable to the new …
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This week the Business Team are filming the video for our upcoming Design Launch on Sat 24th November, where some of the team, our sponsors and partners will witness first-hand the launch of the final design of our as-yet-unnamed new solar car.
We are also producing a separate film with help from our Technical team for CUER’s launch on crowd-source funding scheme Kickstarter (www.kickstarter.com) sometime in early November. We are hoping to raise over £10,000 to help us buy the components we need to win the World Solar Challenge.
But even professional camera-work was laid aside when we decided – as any normal solar racing team would, and should – to have a stroll with Endeavour through Cambridge on a mild Saturday afternoon. With some excellent coordination, a few high-visibility jackets and a new driver in Helena, our co-head of Sponsorship, we captured some beautiful rolling shots from inside Endeavour, something which we’ve been wanting to do since last year! We met with countless enthusiastic (and many bemused) onlookers from all around Cambridge, but one in particular left us humbled: one Professor Stephen Hawking.
The six-strong expeditionary team thought it most instructive just to stand beside …
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