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In his last blog post, TCA Environmental Scientist - physicist Arkadiy Matsekh, PhD - opened our eyes to the nuances surrounding the energy cost of electric vehicles.
In this, the next of his series investigating different aspects of energy transitions, he takes us on a journey into the world of electric bikes, setting out the equations and explaining the environmental logic that makes them an essential part of our sustainable future through the lens of the school-run and daily commute.
The journey begins...
This year our five-year-old son started school: a regular public school in an Australian suburb, just a few kilometres from our place. Of course, for us, as for most other Australians, the primary mode of transport for the school run is the car. Australia has a strongly car-centric culture, and all suburban infrastructure is quite successfully designed to force humans into metal boxes. So, a short 3km school trip (one way) becomes 2160 km driven in average school year. Even though we own a Toyota Prius with a remarkable 5.2 L/100 km real-life fuel consumption, we just didn't feel comfortable driving an extra two thousand km and using up another 112 litres of petrol...so we needed an alternative.
So, this simple math and our environmental concerns led us to the decision to take our son to school on a bike: saving around 350 kg of carbon dioxide emissions, almost three tanks of fuel per year, and keeping our car mileage low. There was a small problem, though...
The school stands on a hill – relatively short, but very steep. I ride my bike up and down this hill pretty much every day on my way to and from work; but even for me (a trained performance cyclist!), climbing this hill on a heavy cruiser bike equipped with a heavy child seat and actual child is challenging, to say the least. For my wife, as well as most other non-trained cyclists, such a hill represents an impregnable obstacle - we needed a solution.
Electric Dreams Become a Reality...
I study electric motors and electric propulsion systems. I used to regularly praise electric bikes as the backbone of sustainable urban mobility: but I never actually had one. Faced with our 'hill problem', I realised this had to change. So, I used some of my professional skills to convert a cruiser bicycle into a school transport for our preppie. I bought a conversion kit from a registered Australian supplier and, after a couple of hours of relaxed work, a cruiser bike with rather limited functionality was transformed into a fully functioning urban-hybrid-electric vehicle! Here it is!
While the hill was insurmountable beforehand, with a few hundred watts high-torque hub motor this previously perilous climb became a piece of cake! One-way trips take between 10-12 minutes; plus, there's no need to be a part of the morning mayhem that is school parking!
So now our little student comes to school mostly by bike...and we've started going for Sunday rides together: me riding my city pushbike and my wife with our little son on her new e-bike. On the flats I can keep up fairly easily, but my family leave me chasing shadows on the hills, even when I ride hard. Not wanting to be forever left behind, my next conversion project followed and my city hybrid bike got an electric motor too! Now I can keep up on weekend rides without a worry.
My e-bike also gives me the freedom to ride to work on the days when I don’t feel like exercising. Instead of taking the tram I now hop on my e-bike and can complete my 15km commute in 35-40 minutes in regular clothes, with no need to change or take a shower when I get in. On one charge of a 360 Wh battery with very gentle pedalling, I can make 4 commuting trips.
Don't get me wrong, I am no stranger to riding far and fast on a pushbike: with around 100,000 km in my legs, I love the feeling conventional cycling can give you. But riding an e-bike adds a whole new dimension to the bike-riding experience. It’s not ‘cheating’, it’s just a different, additional option! If you are an experienced bike rider – just give it a try. If you've never had a bike, make an electric bike your first one!
E-bikes effectively flatten the hills, provide range and make distances inaccessible for most people on a conventional bike easily attainable: and all that can be done in everyday clothes. Electric bikes close the gap between push bikes and cars for most short- to middle-distance urban trips, and do so with just a fraction of energy and associated emissions, even if all the energy is derived from unsustainable sources.
E-bikes spare the rider from the range anxiety electric car drivers are so notorious for. The same range anxiety that has pushed battery packs of modern EVs up to ridiculous size and weight: large Tesla battery packs weight 500-550 kg — enough cells to make batteries for 200 electric bikes. E-bike is generally a parallel hybrid (human + electric motor) and even when you happen to run out of energy in the battery, you are still left with a pedal bicycle, a human-powered vehicle (HPV) – the most efficient locomotion tool that evolution has ever come up with.
Rephrasing a young Steve Jobs: the bicycle for our bodies is like a computer for our minds. Of course, it’s certainly not as fun to ride a 20-25 kg pushbike, and you might need to walk your powerless e-bike up a particularly steep hill. Nonetheless, even without power and unlike an EV with flat battery, it’s still a very efficient means of transport and will ultimately get you home.
And now, after having praised e-bikes so much, let’s move on to the second part of this post, in which I continue to praise electric bicycles and begin to scold cars :-)
Electric Bikes > Petrol Cars: the Equation is Simple!
Electric bikes are amazing: they are motorised vehicles, but because their motors usually have "human-scale" power/torque levels, the ride feels very natural. They tend to slow down under heavy load, when riding uphill, just like a human would, and ride fast with little effort when on the level road. They are fun, they feel good, and they are extremely energy efficient with just 1.2-1.5 kWh giving you around 100 km of range. No conventional EV or hybrid vehicle can beat that. The best electric cars still need 13-15 kWh to cover 100 km.
In addition to the low energy requirement for vehicle propulsion due to its small weight and size, there is another factor that contributes to the outstanding energy efficiency of small electric vehicles: motor operation at close to its peak capacity means near-maximum efficiency. By comparison, modern cars operate at 20% (or less) of their rated power the majority of time; but drivers want to accelerate and climb fast and have extreme maximum speeds sometimes in excess of 200 km/h at their disposal: for this reason, cars are designed with substantially oversized motors.
Operating a motor and a propulsion system at the lower end of its rated power comes with a fundamental efficiency penalty. Paradoxically, it seems that interest in higher power and the top speed of cars is never-ending, which makes them very effective marketing tools for car manufacturers bringing bragging rights for petrol-headed consumers. However, the real value of being able to accelerate to 100 km/h in under 4 seconds, having a top speed of 220 km/h and rated motor power of 200 kW, while the average speed of cars in real-world operation is rarely more than 40 km/h and average power is around 20 kW, appears to be overstated.
In addition to the high power requirements imposed by the significant size and weight of these cars, customers’ demands for even more power results in a drive train which is doomed to sub-optimal efficiency by design. “Driving a powerful car while saving the environment is possible” is the dream we are sold by the car industry, and the electric car industry is no exception: the vast majority of the time, it simply isn't the case.
Of course, riding an electric bike does little to alter the immediate landscape through which we pedal. Sidewalks in my part of Australia are often afterthoughts for city planners: non-existent or windy, very rough and non-uniform; there is rarely a priority crossing for pedestrians or bike riders; and on-the-road bike lanes don't last long and are never physically separated from cars, generally only good for confident and experienced road riders who are increasingly at risk with distracted and careless driving on the rise. In short:
Australia has as a car-centred cultural fantasy that does not match up to the stark realities presented to us by the climate crisis.
So, my wife and I are often the only adult people at school on bicycles. And honestly, it feels a little weird to do things differently. Also, one bike can feel like a single drop in a limitless, fuel-filled ocean of cars...but, “what is an ocean but a multitude of drops?”
Conventional consumer wisdom has taught us that more - bigger, faster, stronger - is always better: yet in the case of sustainable urban mobility this simply doesn't ring true. Electric bicycles are comparatively cheap: they are cheap to own and very cheap to operate; they don't take up much space; and an electric bike embodies just a small fraction of the materials and energy (around 100th) used to produce a conventional car. At the same time, electric bikes give the range and practical average speeds for short to medium trips...and they eliminate hills — one of the major obstacles for many people to start riding. Finally, they really are fun to ride and provide an easy incentive to exercise.
Do your bit for the environment in comfort and style — ride an e-bike!
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Arkadiy Matsekh PhD - Arky to us - obtained his PhD from the Institute of Thermophysics, Siberian Branch of the Russian Academy of Sciences with a major in thermal physics and theoretical thermal engineering. He worked as a postdoc research fellow at Kyushu University, Japan, studying applied superconductivity for energy applications and later moved to Australia to join a privately-funded project of a large superconducting homopolar generator.
He is currently designing and studying electric propulsion systems and is particularly interested in light electric vehicles in general and electric bicycles in particular, seeing them among the key components of sustainable urban mobility. Also, he loves cycling and rides bikes a lot!
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