Sustainable Energy NZ #11: How can we make road transport more efficient?

Welcome to the eleventh post in the Sustainable Energy without the Hot Air – A New Zealand Perspective series. After our previous posts on hydro power, geothermal and wind (and a summary on the big three), solarbiofuelsmarine and waste energy, we’re now looking at answering the question:

How can we achieve a BIG reduction in our personal and national energy consumption?

We covered the breakdown of where we use this energy in the last post. Today we’re dealing with our biggest chunk of energy use: road transport.

A few notes before we begin: as before, the units are in kWh/day/person – ie. if you ran a 40W lightbulb for 24 hours, it’d take ~1 kWh over the space of a day. We then divide it by person to give you a sense of the scale of the resource proportionate to the size of the population. Be sure to check out the methodology. For reference – we’ve been looking to replace around 55 kWh/d/p of energy currently generated by fossil fuels.


About a third (31kWh/d/p) of our total energy use is spent on vehicle travel, which is high by international standards. (This figure also includes some diesel purchases by small farmers and transport operators that are not adequately captured by other statistics.) Incidentally, one litre of petrol contains ~10kWh of energy, so at a national scale, we’re all using around 3 litres of petrol/person/day. By comparison, the average UK citizen spends 14 – 16kWh/d/p on personal vehicle travel.  Consider that the average NZ car drives 18,000km in a year. If all were medium SUVs (0.9kWh/km) with 2 people in them, then this would translate into only 22kWh/d/p. It is clear then that we must make a lot of single-passenger trips in inefficient vehicles. Worse, this works out at a staggering 46kWh/d per vehicle (excluding mopeds, but including trucks)!

If spending on vehicle fuel is our largest energy use, how much scope is there for improvement? MacKay proposes that UK energy expenditure could be halved by electrification of transport, better cycle access and good public transport. Our low population density will limit the effectiveness of public transport and while we’ve made a bit of progress on building bicycle infrastructure, our focus is still heavily on vehicle infrastructure making bike-use less attractive.. We must surely be able to waste less than we do at the moment.

Electrification of Vehicles

McKay makes a strong case for the electrification of personal transport. Electric cars are 3 times more efficient at turning energy into motion than petrol motors, even when accounting for battery losses and transmission losses. When compared to other post-oil fuel sources (hydrogen, natural gas, biofuels, hybrids etc.) the benefits of electric far outweigh the negatives, and offer the ‘path of least resistance’ to uptake.

Most vehicle manufacturers have now recognised that electric is the way of the future and GM, Ford, BMW, Audi, Renault/Nissan and most other major car manufacturers are now intensely developing the technology and beginning limited production. Since 2009, the ‘race’ over the technology that will replace vehicle propulsion has been won by electric. However, the timeframe for the scale up is long, as it takes 20-30 years to replace the rolling stock from the point where they become the predominant technology.

Regarding the transition in New Zealand, it is likely that we will see greater adoption of electric cars as they become more economic. Currently the sticker price of electric cars is significantly higher than comparable models. This is primarily due the battery, which at half the cost of production is the single most expensive part of the car. We can expect this to come down over time.

The other relevant factor to consider is the impact of ‘range anxiety’ – electric cars have limited ranges compared to petrol cars which can just be quickly refuelled, and this is a concern of a lot of buyers. NZer’s drive on average 50km a day, which is less than half the range of most electric cars on the market. For everyday use, electric can suffice. For longer trips – technology is improving all the time, and most electric cars now come with a ‘fast charge’ option that gets up to 80% of the charge within the first few hours. Tesla Motors has just announced new charging stations that can give three hours of driving after 30 minutes of charging. This is a fast developing area of technology. The other alternative is to rent a petrol car for longer trips.

In regards to the impact of electrifying transport on the grid, Transpower’s Centre for Advanced Engineering has conducted studies to assess viability and how much, if any, new generation capacity would need to be built. They concluded that even in the ‘high uptake electric vehicle scenario which sees over 390,000 electric vehicles on New Zealand roads by 2025, a maximum of only 180 MW of additional generation capacity would be needed – that’s the size of two medium sized wind farms such as ‘West Wind’. Further, the majority of the energy used for recharging would be at night when the grid is at its lowest and electricity is at its cheapest. The current wiring set ups in NZ households are capable of handling basic charging, but would need modification if they were to handle high voltage charging stations. [9x97yvx]

Like McKay in the UK, we think the case for the gradual electrification of New Zealand’s transport networks is strong, but will depend on the developments of car manufacturers overseas bringing down the costs, the relative costs of other transportation and the business models that can be developed for a New Zealand context that can drive adoption.

The case for bicycles

Bicycles use only 1kWh/100km, or roughly 1/100 the energy a car uses [95nwj67]. McKay is a big fan of biking for its energy intensity and related health benefits. It is easy to imagine that NZ, with its outdoorsy lifestyle and temperate climate would be an excellent country in which to encourage more use of biking.

What are the things that we can do to encourage a greater uptake of bikes? A Rutgers University study of biking patterns in 100 US cities has shown that there is a strong correlation between the number of bike kilometres travelled and the level of bike infrastructure present (bike paths/bike stands etc.) [8597ys8]. A Ministry of Transport study has similar conclusions [9xghegt].

McKay makes a big case for the development of bike-friendly infrastructure and legislation, in the form of separate bike lanes, lower speed limits and collision regulations that favour cyclists. If we’re going to increase biking as a viable transport option in NZ, we will need to take cycle infrastructure investment more seriously than we do today.

Improving our current vehicle options

When considering a car purchase, there are alternative strategies that can improve energy use. For example it has been noted that people tend to buy the car they want to use for holidays – and then commute in it. How about if we bought an efficient commuter vehicle and just hired an SUV for 3 weeks of holiday? According to the AA vehicle running costs report (AA members only, sorry), it works out something like this:

Small car (1200cc) Medium Diesel SUV
Annual running costs $7300 $11,100 $14,000

Three weeks hire on a Prado or Pajero would cost around $3000 plus fuel while a small SUV would be $2000. The philosophy of “commute in small and hire big when required” saves money as well as energy.

Being very optimistic, let’s suppose that we can get energy use from car travel down to 15-18kWh/d/p by savings and improved technology by around 2030, a saving of 13-16kWh/d/p.

Q.  Should I telecommute when that means heating my otherwise empty house, when I could drive to work and use their heating system instead?

A.  If you work for 8 hours at home crouched over your one bar heater, you use 8kWh of heating. You spend the same energy driving 13km in a Yaris or 9km in a RAV. If it works for you, then telecommuting is a good option energy-wise.

Q.  How much fuel do I save if I travel slower?

A.  See MacKay’s book for a detailed analysis, but considering air resistance only, fuel usage is proportional to square of speed. I.e. if you went half as fast, you would use a quarter of the fuel. In real-world performance, cars have rolling resistance. Most engines are tuned for an optimal revolution speed and gearing is designed for current road speeds. Nonetheless, travelling at 80kph instead of 100kph could deliver up to 30% fuel saving.

We’ll be looking a bit more into the costs of the electrification of transport at the end when we propose a plan using the different things we’ve talked about in this series.

Recommended reading:

Tom Murphy at Do The Math has a number of articles on the electrification of transport, starting with a calculation of the MPG of electric cars, assessing whether a solar powered car is a feasible option, doing the math on whether 100MPG is even possible, and assessing where it is that we can all reduce our liquid fuel use. He also has a great article on the limitations of battery development for electric cars – they’re hard to build, and they’re not developing at anywhere near the speed of computer chips. That last one is a sobering reminder of the fact that new technologies sometimes take longer than we would like to develop.

30 thoughts on “Sustainable Energy NZ #11: How can we make road transport more efficient?”

  1. The biggest problem with transport is the very entrenched notion that private ownership of vehicles is a ‘right’. Most cars are used by their owners for 1-2 hours per weekday, so are sitting idle for maybe 95% of the time. When the cars are being used, they are all being used at the same time, so it’s slow to get around – much slower than if fewer vehicles with more occupants were used.

    I sometimes play a game when I’m at a bus stop – counting the number of empty car seats that go past the bus stop before the bus arrives. I have seen over 200 empty seats go past in less than 10 minutes – all going very slowly in a long line of traffic. This is literally insane.

    As a society, we really need to start questioning the individual ownership model for cars. Do people really need a car just so it can sit in a garage for 95% of the time? It would be way more efficient to have pools of cars out in the suburbs that can be shared by several people for commuting, and then hire cars for weekend activities.

    But as I say, this is a very entrenched view, so even suggesting something like this will get you labelled as a commie enviromentalist do-gooder.

    1. Yes it does label you as a commie, you are correct. People don’t have a right to own a car, but they do have a right to tell the state where to jump if they say they can’t own a car.

      I say this as a telecommuter, by the way.

      1. Gosh what evil people commies are. In my opinion, you have no right to infringe on the rights of others. In a good libertarian framework, you can do what you like so long as you also take full responsibility for your actions, including that if you damage someone, you pay them compensation. However, this becomes tricky when the harm is collective and/or cross-generational. A person with lung cancer from second-hand smoke holds who responsible? Ditto for someone who collapses from smog. In climate change the issue is both handing a problem to a future generation and handing problems from a wealthy west to more vulnerable populations on say large deltas.
        Sadly, we also find the libertarians, unable to solve these problems in a simple framework, fall back on denial instead.

      2. Thanks Andy, that’s exactly the sort of brain dead, knee jerk reaction I was expecting. It’s interesting that you can’t tell the difference between “state” and “society”. The key words in my comment were “As a society” – in other words, I was advocated a period of informed discussion followed by a majority decision. There’s a word for that, isn’t there – oh yes, democracy.

        The problem with informed discussion is when people with vested interests start leaping up and down making fatuous comments about being commies, drowning out reasoned debate.

  2. As far as I am concerned it’s criminal that neither the previous labor government or this have provided any tax relief or incentive to encourage the use of hybrid or fully electric cars. The cost of this new technology when it reaches NZ is so much higher than the ICE that’s its hard to financially justify buying them.

      1. I’d favour subsidies for full electric over both a Prius and a Golf TDi. Hybrids I see as an interim technology while the implementation of electric improves and people’s fear of the range limitation dissipates.

    1. I not much of a fan for any kind of subsidy – it means government is in the business of picking winners and very open to abuse. If the Prius fuel economy was better then that would speak for itself. A carbon tax would work in favour of any technology that was less carbon efficient so in my opinion, it is better than a subsidy.

      Eventually you can make the transition to fully electric but at the moment, short term ways to reduce carbon emissions from petrol is
      1/ dont buy that SUV – you are kidding yourself about your needs. Hire it when needed and save yourself some money.
      2/ Reduce speed limit (yes thats a commie, not-allowed-to-drive-as-fast-as-you-like attitude)
      3/ get on your bike
      4/ make public transport work.
      5/ telecommute
      6/ videoconference

      1. That’s a great idea Phil.
        I do all those things, but when I need a more grungy 4×4 for a backcountry trip I’ll do the 3 hour round trip to hire one.

        1. Then buy a grungy 4X4 and use it for only for that purpose. You will probably end up doing that even though no one will be forcing you to change. What will force you to change is good old supply and demand, which with or without a carbon price, is going to continue to push up the real price of oil.

  3. Then there is the velomobile to consider. With electric assist they can be as fast and as comfortable as cars and up to 80 times more efficient is one claim. I’ve divided them into various types below but there are finer classifications:

    1, pure cycle – advantages over bicycles: much lower wind resistance,
    therefore higher top speed (40-50 km/h), operator comfortable and out of the weather. Speed record >130 km/h
    Disadvantages: less nimble, heavier so take more effort to accelerate and climb; the law in most countries including NZ) does not recognise them as street vehicles! This last also applies to e-velomomiles.

    2. limited electrical assist (a) only during acceleration or climing) (b) limited to 25 km/h, in some countries to 45/50 km/hr, motors tend to be limited to 250 watts,
    regenerative braking.

    3. Motor can be used to maintain speed (halves range – 60 km say) – up to 750 watts

    4. Unlimited – recognised as road vehicles – rare

    Additionally there are e-velomobiles with car safety gear, lights, mirrors, indicators, many have roll bars and even radio/stereo sound.

    Detailed overview of velomobiles, types and laws – October 24, 2012
    I wanna ride a velomobile – 2009

    So bicycles can be ridden anywhere in NZ except on motorways and the Auckland harbour bridge but their safer, faster, more useful relatives- velomobiles cannot. The law should be ammended to encourage development and deployment of relatively low cost e-vehicles – the law should not lock us in to unsustainable behaviours, but it does.


  4. On related health benefits for bicycles, well not bicycles and not entirely on topic but I was bemused to see in that “democracy now’ sandy coverage two chinese blokes, one young, one almost elderly, both commenting on the health advantages of running up 20 stories of stairs to deliver supplies to the immobile elderly.


  5. Great post. Thanks!
    I guess many families in NZ already own two vehicles. The introduction of EVs in this case is much easier as the family can choose the right car at the right time for the right sort of trip.
    Also most people will love their EV once they tried it and realized the low running cost.
    One way to support low consumption diesels such as the GOLF Tdi or similar cars such as the low consumption Hyunday Getz Diesel would be for the government to introduce a step on the RUC scale for small diesel vehicles. At the moment the lowest RUC class contains anything from a Hyunday Getz to a 2 Ton Pajero. This makes no sense and artificially makes a 4 Lit/100Km diesel more expensive than a 5 Lit/100Km petrol to run.

    1. Two vehicle families are pretty much the norm. When my son was 7, he went to an after-school club. They had everyone sit round and introduce themselves. He was asked: “What colour is your dad’s car?”
      “Blue,” he said.
      “And what colour is your mum’s car?”
      “I just told you, blue”
      He then had to explain that our family only has one car – the concept was completely alien to them.

      1. Multiple car families are a relatively recent phenomenon. I grew up in the 60s and 70s and families were lucky to have one vehicle. Only with the deregulation of used imports in the late 80s did this trend to multiple car families really develop.

  6. While we’ve all seen promising sounding new technologies fail in execution or never get commercialized, I thought I would mention a few promising battery technology developments.

    A group at MIT have developed utility scale liquid metal batteries for storing power from PV solar and wind power.

    The Weekend Wonk: Liquid Metal Batteries
    TED talk video 15 minutes

    {watch it at Climate Crocks -3/31/2012}

    DOE-funded battery breakthrough to halve cost, triple range

    “A new breakthrough from California-based Envia Systems will yield lithium-ion batteries that are less than half the cost of current cells, while also having three times the energy density. ……….
    Envia’s announcement said that its packs would deliver cell energy of 400 watt-hours per kilogram at a cost of $150 per kilowatt-hour. Though it doesn’t disclose a cost breakdown, Tesla Motors rates the energy density of its Roadster’s pack at 121 watt-hours per kilogram. Envia said its energy-density performance was verified in testing of prototype cells at the Naval Service Warfare Center’s Crane evaluation division.”

    {read it at Grist}

  7. Not only has Tesla introduced their new superchargers for Tesla cars, the charging is FREE. And solar powered. They have installed 6 charging stations in California and will have 6 more by next year. You can drive for 3 hours at 100km/hr and recharge in 30 minutes. They plan to build these all across America, along interstate highways.

    You could drive from northern California into Arizona or maybe Tijuana, Mexico on free electricity, just using their 6 existing charging stations.

    They are working with a company called Solar City that installs solar systems on rooftops etc. Solar City will install solar panels on your roof at no charge. You pay them for the power, at a lower rate than your current utility bill.

    BTW the new Tesla sedan will go 0-100 km/hr in 4.4 seconds.

  8. The problem with oil has been that it is a fabulous fuel and has been really cheap, and still is. As a result we have ignored public transport and ant effort to use electricity for transport. The motor manufacturers and the government have not helped by trying to replace a petrol car with and electic one. It won;t work. Oil is to good and to cheap. With government assistance with taxes we could make a start by encouraging short distance electric vehicles to use for urban travel. Many families have two vehicles. A big one for the main car as a smaller one for shopping or to take the kids to school. Its the second car we should target as a start so that we can slowly reduce our dependance on oil and move to an electric transport society. We know its going to happen and it takes a lot of work to make it happen. Best get started now.

    May not be considered `pretty` by some but nevertheless is 98% carbon neutral and 68% efficient in converting stored energy to motive power.
    Tata Motors have endorsed the technology and intend to produce three models by October 2013.
    Violia are negotiating exclusive rights for EU and many others are queuing.
    Just think, no exploration, drilling, refining, transporting and pumping to the tank before burning and blowing out 80% waist pollutants (that you just paid hard cash for) into the atmosphere that you breath and much easier and cheaper to produce than electric vehicles.
    Aaah but I guess it will be to good to be true.

    1. The Air motor is interesting but has significant barriers to increasing efficiency: The laws of Physics. Compressing air causes the same to heat up. In the process of loading the tank with compressed air this heat is removed through cooling. Hence the efficiency of getting energy (in form of compresses air) into the tank is rather low. Some thermal energy is recovered from the environment when the air expands in the engine while driving but the overall the process is not a stunner on the efficiency front. A nation on Air cars could well need twice the overall prime energy input than a nation on EVs.

    2. Well! I had started to folow this air motor business about 14 months ago then forgot. It has come a distance since. The price makes it a starter too.

      In the list of features one that is not mentioned is that in NZ for example, some kind of infrastructure is already in place. I refer to recharging the bottle. Obviously the ‘tank to tank” dedicated recharge station is fastest and best but having read the docs and checked out compressors, I see that at a pinch diver air charging stations could manage up to 330 bar but taking much longer. Three phase and even single phase home high pressure compressors are also feasible and at the worst a low pressure compressor could still give a car enough air for 20 km say.

      Some days back a friend drew my attention to velomobiles but commented “not to Tuatapere” The furthest away place reachable by road without crossing Foveax Strait. After reading about airvolution I posted back the link with the comment “Tuatapere yes”.

      Perhaps NZ should have a challenge “North Cape to Tuatapere, no emissions, battery and air tank swaps OK, even sailing yachts permitted! Can’t see yachties that keen on the Waiau river bar or risking a lee shore – they would prefer Bluff. To qualify get to the start on own hull or wheels from nearest large center or further – Kaitaia. Any route permitted. No trucking or rail travel – any way across Cook straight you can manage but emissions must be accounted for along with charging emissions and come off the competitor’s time – bit fuzzy this :).

      Sound like fun? Of course such an event must not turn out like a certain Olympic marathon back in 1904 or thenabout. The first two finishers were disqualified for taking strycnine as a performance enhancer, the third was disqualified when it was discovered he took a train for two thirds of the distance. Th first african entry was held up when a dog chased him a kilometre off course! Heard this on QI (Prime) last night


  10. Vehicle X-prize 2010 $5 Million Mainstream Class Winner:
    •Edison2 “Very Light Car #98” (Charlottesville, VA)
    •Economy: 102.5 MPGe
    •Fuel: E85 ethanol
    •Boasting the lowest drag coefficient of any car with four wheels tested in the GM wind tunnel and at the Chrysler Proving Grounds, this vehicle demonstrated over 100 MPGe on the test track, and verified in the lab, under stringent testing conditions using a highly innovative small displacement engine. Its low weight of just 830 pounds is a tribute to its use of light weight materials, reduced engine displacement and a host of other weight-saving innovations.

    A team in Chrischurch is getting started on a 100MPG capable vehicle arising from

    Wikispeed is a ‘hands on’ project for skilled volunteers (and not just technical manufacturing – also legal, business etc). more here –

  11. I would like to know what beyond cars means. But on cars I think I read that the gasolene motor could be very quickly swapped for an electric motor. Is that true or have I my cars mixed up?


  12. Yes Noel – the car is modular, so easy to choose or switch between electric and combustion. A Wellington contributor is involved in developing the electric propulsion module.

    The rapid development process could be applied to just about anything. The aim is to make and sell stuff to fund further projects. An Auckland group is using project to distribute water at events and emergencies to learn the process.

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