Author: Oliver Bruce

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), solar, biofuels, marine 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.

Cars

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)!

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Sustainable Energy NZ #10 – How can we achieve a big reduction in our personal and national energy consumption?

Welcome to the tenth post in the Sustainable Energy without the Hot Air – A New Zealand Perspective series. We’ll be changing gears here from our previous posts on hydro power, geothermal and wind (and a summary on the big three), solar, biofuels, marine and waste energy. From here on out we’ll be attempting to answer the question:

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

It’s a very important topic – and one prone to greenwashing and hype. Like McKay, we want to have informed discussion about the options available to us here in NZ, so we’ll be going through topic by topic and looking at energy use in each sector of our lives: transport, residential energy, the things we buy, and so on. We hope that you find it interesting and informative.

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Sustainable Energy NZ #9 – Here Comes the Sum – what are renewables worth?

Welcome to the ninth post in the Sustainable Energy without the Hot Air – A New Zealand Perspective series. Today we’re summarising the numbers on the various renewable energy options in New Zealand (and finding they’re more than sufficient!). For the background to the work please our introductory post here. Also check out our earlier posts on the potential of hydro power,  geothermal and wind, and the summary on the big three. More recently we’ve dealt with solar, biofuels, marine and waste energy. Note: 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’re looking to replace around 55 kWh/d/p of energy currently generated by fossil fuels. 

So we’ve gone through the various renewable energy options over the last week or so. So where does this leave us for increased generation potential among renewable options? The affordable, mature technologies are hydro, geothermal, wind, waste gas, solar heating and biofuel. Large-scale solar and marine technologies are really promising options for the future but cannot be realistically considered now.

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Sustainable Energy NZ #8 – The Tides They Are A-Changin’ – the marine and waste energy resource

Welcome to the eighth post in the Sustainable Energy without the Hot Air – A New Zealand Perspective series. Today we’re crunching the numbers on marine and waste incineration potential in New Zealand. For the background to the work please our introductory post here. Also check out our earlier posts on the potential of hydro power,  geothermal and wind, and the summary on the big three. More recently we’ve dealt with solar and biofuels. Note: 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’re looking to replace around 55 kWh/d/p of energy currently generated by fossil fuels. 

The marine environment offers several possible renewable energy sources, notably wave and tidal energy. Wave energy systems have been studied by the Electricity Authority, and data here comes from their report [yeqtogu]. Feasible wave energy plants need wave energy greater than 20kW/m “close” (say 6km) to coast. New Zealand has 2000+ km of coast-line fulfilling these parameters, mostly on the west coast. Wave derived energies in the far south can be 60 to 80kW/m, which is impressive. That is approximately 86kWh/d/p for a 50% efficient wave generator covering half our available coastline. However, a reality check indicates that no such mechanism exists (so far wave generators have been built for survivability rather than efficiency) and many factors would constrain where wave generators could be built.

A fairly detailed analysis based on currently available technology has identified sites offering perhaps 2kWh/d/p and a maximum potential for perhaps 27kWh/d/p. While a number of prototype and early commercial plants have been deployed worldwide since 2009, this realistically still is best be described as an emerging technology with very substantial environmental and economic barriers to deployment.

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Sustainable Energy NZ #7 – Biofuel Bonanza? – NZ’s bio-energy potential

Welcome to the seventh post in the Sustainable Energy without the Hot Air – A New Zealand Perspective series. Today we’re crunching the numbers on the potential for biofuels in New Zealand. For the background to the work please our introductory post here. Also check out our earlier posts on the potential of hydro power,  geothermal and wind, and the summary on the big three. Yesterday we dealt with solar (and found it was pretty big!). Note: the units are in kWh/day/person – that is, 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’re looking to replace around 55 kWh/d/p of energy currently generated by fossil fuels. 


Energy problems are just one of the significant challenges facing our civilisation so we are reluctant to consider options that affect food production or contribute further to soil degradation. However, as we transition away from liquid fuel-based transportation, biofuels could play a role in keeping us mobile.

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