NZSM Online

Get TurboNote+ desktop sticky notes

Interclue makes your browsing smarter, faster, more informative

SciTech Daily Review

Webcentre Ltd: Web solutions, Smart software, Quality graphics


Sustainable Energy

A variety of sources could help New Zealand become sustainably self-sufficient in its energy needs.

Dai Redshaw

For several years the Sustainable Energy Forum has promoted a sustainable energy policy for New Zealand. Keith Dawber and I have been examining options which may assist us to achieve such a policy, and the Energy Efficiency and Conservation Authority (EECA) actively promotes the better use of energy in our country.

If we can achieve a sustainable use of energy, then we will meet our energy requirements without compromising the ability of future generations to meet their needs. At present humankind is far from such a situation; the planet's reserves of fossil fuels are being depleted at a rate whereby several groups have predicted that supplies of oil and gas will begin to decline within the next few years, which given humankind's track record of preparedness, may cause yet another "oil shock".

Humankind is also facing the probable consequences of global warming. Although not conclusive, there is strong evidence that our planet is warming. Most authorities believe that the warming trend is caused by the release of greenhouse gases such as carbon dioxide into our atmosphere. We are conducting an unplanned and unauthorised experiments on the effects of altering the concentration of certain trace gases in our planet's atmosphere. Aware of the possible consequences of climate change, the international community negotiated the Framework Convention on Climate Change (1992) which New Zealand has ratified. We are thereby committed to stabilising our CO2 emissions to our 1990 levels.

Unpleasant Consequences

If warnings of future oil shocks and global warming prove to be correct, there are unpleasant consequences for New Zealand. Our economy is more energy-intensive than most OECD countries, approaching the economies of Eastern Europe and the ex-USSR in this parameter. Furthermore we are only about 80% energy efficient, importing about half of our liquid fuels. Although we have extensive reserves, our gas fields, which supply about half our energy at present, are likely to run out before 2020. If an oil shock were to occur in the future, powerful countries would be likely to secure their crude oil supplies and we would be disadvantaged, with dire consequences for our agricultural, forestry and fishing industries, as well a for tourism, which is also dependent on the ready availability of liquid fuels.

Global warming has the potential to adversely affect our country. At first sight it might appear pleasant to anticipate a temperature rise of a degree or so nationwide, but this brings with it the likelihood that diseases such as malaria, as well as tropical insect pests, could become established in northern districts, and that a sea level rise of around one metre during the next century could expose our low-lying areas to storm-damage and flooding.

Self Sufficiency

If we accept the above, New Zealand should move towards energy self-sufficiency. Unfortunately our present reliance on "market forces" does little to encourage such a move. In the event of an oil shock, market forces would cause the price of liquid fuels to rise sharply, moving our economy towards the use of other forms of energy -- however, by the time such adjustment was made, our economy would have suffered considerable damage.

New Zealand has the potential to derive much of its energy from renewable sources. We already generate around 70% of our electrical energy from hydro schemes, and a further 5% from geothermal sources (not strictly renewable). Although there is little scope for further major hydro development, other than a controversial dam at Tuapeka Mouth on the Clutha, construction of small schemes, such as one in South Canterbury, which will provide three megawatts as well as irrigation for the surrounding area, would contribute significantly to our supplies.

Geothermal energy could economically supply up to a third of our electricity demand if our resources were developed. Although geothermal generation causes some emission of CO2, it has the advantage that the major fields are close to Auckland, and so the growth demands of that conurbation could be met without the need to strengthen the grid connections from the South Island.

Of the three main renewable forms, wind energy is beginning to be exploited. A 3.5MW wind farm comprising eight turbines has recently been commissioned near Martinborough, at a cost of $8.8 million, and several major farms are in the planning stage. Wind farms have advantages over major hydro schemes, in as far as their construction does not inundate land, and they could be dismantled and relocated if necessary.

To illustrate these points, the construction of the Clyde Dam flooded 26 square kilometres of land, required the construction of an expensive stretch of new highway to replace the original highway flooded in the scheme, and $337 million had to be spent on land stabilisation. This sum could have purchased 300 wind turbines with a combined output of one-third of the Clyde Dam. These turbines could have been located close to North Island cities and would not have caused land to have become unproductive; many feel that they would have represented a much wiser use of the money.

Even developing the most favourable wind sites could supply half of our annual electricity needs (45 petajoules), and such a source would complement hydro-generation well. Such development would remove the need for fossil fuel use at Stratford and Huntly, extending the life of the Maui gas field.

Biomass is another energy generating system which is clearly suitable for our use. The technology for electricity generation from biomass is well established, but possibly its main advantage to us is in the manufacture of liquid and gaseous fuels. It is estimated that by 2010, six million tonnes of dry wood waste will become available annually as a consequence of our forestry operations. If this wood were gasified in apparatus such as that being developed by Ralph Sims's group at Massey, it would be possible to produce up to 600 kg of methanol for each tonne of dry wood. This methanol could be converted to road fuel by the Mobil process, or blended with petrol in up to 15% concentration. Alternatively it could be used as a fuel in fuel cells.

An alternative would be to convert the biomass to ethanol by fermentation (200kg/t). The blending of ethanol into petrol improves the octane rating without the need for the dreaded aromatics, and with suitable conversion motor vehicles can run on pure ethanol. Brazil uses ethanol as a road fuel, and in that country four million cars are fuelled that way.

Biogas obtained from the anaerobic fermentation of organic material, either in fermentors or city landfill has properties similar to CNG, and is being increasingly used by cities for domestic gas reticulation, or electricity generation. CNG is well known as a fuel for road vehicles.

Solar energy represents a source of energy delivered free to every roof in New Zealand, even those in Dunedin! It is estimated that solar water heating panels could supply half of the hot water required by every household in New Zealand. As these panels cost around $3,000 fitted, this represents a tax-free return to the household of at least ten per cent, as well as a saving of 300 kg of carbon emissions from our fossil-fuelled power stations each year, for each panel fitted.

Photovoltaic cells are not economic at present, except in remote situations such as Great Barrier Island, nevertheless their cost is falling rapidly. New Zealand is well located to make use of this technology, and it is surprising that our government is not vigorously supporting research in this field.

Energy conservation would help to secure our energy supplies. This is particularly so in the field of transport, which accounts for 37% of our consumer energy. Private cars which use about 60% of the transport energy have increased in energy intensity from 2.00 MJ (passenger km)-1 to over 2.30 MJ (passenger km)-1, probably due both to the purchase of larger engined models and increase in single car-occupancy. Even the fashionable use of four-wheeled drive cars for recreational purposes places further demands on fossil fuel use. In total our passenger energy use has grown over 20% in the past four years.

Road freight transport, although declining in energy intensity, is still less efficient in terms of energy consumption than rail or sea. Nevertheless during the last twenty years the percentage of freight transported by road has increased from 38% to 58%. It is arguable that we cannot sustain our use of road transport in these forms for much longer. Certainly efforts to develop a national transport policy should be implemented, as well as efforts to increase the use of public transport within and between urban areas.

I would like to suggest that New Zealand should develop a long-term energy policy. Just as we have accepted that our superannuation provisions may not be sustainable in the long term, I propose that the same is true of our energy use. Although any decision will have to be made, or at least approved, by society at large, I believe that the scientific community is in a unique position to convince politicians and voters that changes are necessary for the security of our country and ultimately our planet.

Dai Redshaw teaches at Kavanagh College in Dunedin.