This is a guest post by Phil Scadden, a regular commenter at Hot Topic (bio at the end of the post). Phil’s interested in energy issues, and has spent a considerable amount of his personal time developing an overview of New Zealand’s energy issues, inspired by the approach used by Cambridge physicist David MacKay in his recent book Sustainable Energy – without all the hot air. I’m very pleased to say that Phil is making his work available via Hot Topic (PDF here), because the perspective he brings provides a starting point for the strategic energy debate we need to be having. Over to Phil:

Sustainable Energy – without all the hot air by Cambridge physicist David MacKay is an excellent and highly readable book of numbers about the questions associated with sustainable energy (available as a free download at www.withouthotair.com). As an advocate of sustainable energy, he describes himself as “pro-arithmetic” rather than a campaigner for one type of energy production over another, which is surely what informed debate needs. Rather than dealing with daunting numbers, he reduces energy calculations to units of kWh/person/day. 1kWh is the unit we pay for in our electricity bills — the energy used by one bar heater switched on for one hour. If you want to prioritise savings then you need to read this book. Turning off a cell phone charger when not in use for a year saves the energy found in one hot bath. “If everyone does a little, then we will achieve only a little”.

The majority of MacKay’s calculations are done for the UK, and I was interested in a New Zealand perspective. To this end, I have used a similar approach to look at two questions.

Can New Zealand maintain its current per capita energy consumption without fossil fuels and, in particular, can we live on renewable energy sources alone?

How can we achieve a BIG reduction in our personal and national energy consumption, in order to reduce our power requirements?

The detailed document (about 20 pages) can be downloaded here, but this is a quick overview.

Currently 30% of NZ’s energy comes from renewable generation. My calculations (based mainly on 2007 data) show that NZ has the potential to increase this to nearly 100% over the next few decades, thus eliminating fossil fuel use, while still maintaining our current per capita energy consumption (assuming no significant population growth). We could do this initially with new hydro, geothermal and wind generation, while large-scale solar and marine technologies are promising options for the future. Biofuels are feasible but only at the expense of considerable agricultural intensification.

NZ is energy-rich, but every option using renewable sources has its own problems. If we don’t like the environmental and other consequences of the available generation options, the only alternative is to reduce our power requirements. Vehicle fuel is NZ’s largest energy use (about a third of our total) so savings in this area have the potential for greatest significance. Optimistically, we might be able to reduce our energy needs by up to 25% by 2030, by savings and improved technology (especially electrification of transport).

I have also constructed an example plan that could be reasonably executed by 2025, incorporating both generation and conservation measures. This plan includes a huge number of windmills (10,000+), the 8 highest priority hydro schemes (including Lower Waitaki and Clutha), all geothermal schemes which could be consented within current resource management law, solar hot water and solar photovoltaic panels for half the homes in NZ, completion of home insulation, and large-scale adoption of electric cars. These combined measures could potentially allow NZ to operate on all-renewable energy, at an estimated cost of $91-174B. (Compare this with NZâ€™s GDP of $177B, or Sustainable Energy R&D of $0.032B).

Note that, if we want to live on renewable energy, we donâ€™t have to say yes to every wind and hydro proposal but we have to say yes to a great many of them. And if we want power to be affordable for everyone, we have to say yes to proposals in places where it is cost-effective to generate power.

Living on renewables is relatively easy for our current population of 4 million. Doing the calculations for 14 million would be more difficult. To maintain the country in even close to its current state, we need to constrain population growth as a priority.

In addition to energy sourced in NZ, New Zealanders also contribute to overseas energy use, with opportunities for considerable savings. This applies particularly to air travel and imported â€œstuffâ€ (eg the embodied energy in our imports from China).

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Phil Scadden is a Dunedin-based geoscientist/number-cruncher working from GNS Science Ltd. While professionally involved in the thermal modelling and hydrocarbon geochemistry of sedimentary basins, he is also keenly interested in energy and leads a GNS project investigating thermal power efficiency from the perspective of fundamental thermodynamics. The investigation here is a private work.