Tag Archives: electric car

Difficult or inconvenient data about electric vehicles

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photograph of a MDI Airpod 2.0The embodied carbon (i.e. the greenhouse gas emissions produced by its manufacture and assembly) of a typical small (compact) battery electric vehicle (BEV) is about 14 tonnes CO2 compared to about 7 tonnes CO2 in a compact internal combustion engine vehicle (ICEV) [see brusselblog.co.uk for overview of estimates from several sources].  This is mainly a result of the embodied carbon in the batteries.  My compact ICEV does about 50 mpg and we drive about 8,000 per year so we burn 160 gallons per year and one gallon generates about 9 kg CO2; thus, the carbon emissions from my ICEV are about 1.4 tonnes CO2/year. Hence, with our driving habits, building and using a compact ICEV car for five years is equivalent, in carbon emissions (= 7 + (1.4 x 5)), to just building a small electric car.  This does not account for the carbon footprint of electricity generation for the electric car which will not be zero and be dependent on how the electricity is generated; nor is recycling of your old vehicle included.  If you already have a ICEV car then your additional emissions resulting from its continued use will take about a decade to be more than buying a new electric car though by buying an electric vehicle you will move the pollution away from where you live and work.  If you buy an electric SUV, as about 45% of new car purchasers do worldwide [see IEA data], then many more years will be required to acheive a net reduction in carbon emission because the embodied carbon in an electric SUV can be five to ten times more than a compact ICEV.  The challenge for engineers is to develop vehicles that have both zero emissions in use and also zero embodied carbon.  Meanwhile, the bottom line is to use public transport whenever possible but if you need a car then have a small one and keep an electric one for much longer than an internal combustion engine vehicle – neither helps achieve net zero.

Image: the MDI Airpod that runs on compressed air [see ‘Hot air is good for balloons but cold air is better for cars‘ on May 19th , 2021.

Isolated systems in nature?

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Is a coconut an isolated thermodynamic system?  This is a question that I have been thinking about this week.  A coconut appears to be impermeable to matter since its milk does not leak out and it might be insulated against heat transfer because its husk is used for insulation in some building products.  If you are wondering why I am pondering such matters, then it is because, once again, I am teaching thermodynamics to our first year students (see ‘Pluralistic Ignorance‘ on May 1st, 2019).  It is a class of more than 200 students and I am using a blended learning environment (post on 14th November 2018) that combines lectures with the units of the massive open online course (MOOC) that I developed some years ago (see ‘Engaging learners on-line‘ on May 25th, 2016).  However, before devotees of MOOCs get excited, I should add that the online course is neither massive nor open because we have restricted it to our university students.  In my first lecture, I talked about the concept of defining the system of interest for thermodynamic analysis by drawing boundaries (see ‘Drawing boundaries‘ on December 19th, 2012).  The choice of the system boundary has a strong influence on the answers we will obtain and the simplicity of the analysis we will need to perform.  For instance, drawing the system boundary around an electric car makes it appear carbon neutral and very efficient but including the fossil fuel power station that provides the electricity reveals substantial carbon emissions and significant reductions in efficiency.  I also talked about different types of system, for example: open systems across whose boundaries both matter and energy can move; closed systems that do not allow matter to flow across their boundaries but allow energy transfers; and, isolated systems that do not permit energy or matter to transfer across their boundaries.  It is difficult to identify closed systems in nature (see ‘Revisiting closed systems in nature‘ on October 5th, 2016); and so, once again I asked the students to suggest candidates but then I started to think about examples of isolated systems.  I suspect that completely isolated systems do not exist; however, some systems can be approximated to the concept and considering them to be so, simplifies their analysis.  However, I am happy to be corrected if anyone can think of one!

Image: https://www.flickr.com/photos/yimhafiz/4031507140 CC BY 2.0

Origami car-planes

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Origami wings in the roof-box?

Origami wings in the roof-box?

A few weeks ago I was fascinated by the competitors’ bikes tessellated on top of the team support cars during the Tour of Britain [see my post entitled ‘Tessallating bikes‘ on September 10th, 2014]. What if instead of tessellating bikes we could use origami to fold away a set of wings? Many people have dreamed of escaping the frustration and congestion of traffic on the road with a convertible. Not the classic convertible but a car that converts to a plane. One small company from Massachusetts, Terrafugiama has already flown a prototype flying car with self-folding wings and is working on an advanced prototype capable of vertical take-off and highway driving. Vertical take-off with wings is difficult so as an alternative a group of universities in Europe is studying the feasibility of a Personal Air Transportation System (PATS) based on a helicopter, known as MyCopter.

These convertibles are difficult to design in practice due to the space constraints for a flying car to take-off and land, the need for two propulsion or at least two transmission systems, the different type of suspension required for comfortable driving compared to landing, the current approach to crashworthiness in cars, and the overwhelming requirement for a light-weight system if there is any hope of getting airborne.   If you add to this list the desire for an environmental-friendly vehicle then perhaps there is no hope, unless we can cross a Tesla with the Airbus prototype electric plane, the E-plane!  [See my post entitled ‘Are electric cars back?‘ on May 28th, 2014]

Sources:

‘Why we’re not driving the friendly skies‘ by Stuart F. brown in the New York Times on August 22nd, 2014

‘If cars could fly‘ by Nick Bilton in the New York Times on June 30th, 2010

http://www.nytimes.com/2014/08/24/automobiles/pie-in-the-sky-flying-cars-from-the-past.html?action=click&contentCollection=Automobiles&module=RelatedCoverage&region=Marginalia&pgtype=article&_r=0