For about 150 minutes in June, New Zealand was on the brink of running out of electricity.
A cold snap over most of the country on June 19, along with heavy snow in the central South Island, rocketed the demand for electricity to a record high.
New Zealand hit a peak demand of 6630MW between 5.30pm and 6pm the time when people get home from work but commercial and industrial demand is still high.
Between 5.34pm and 8pm that night, Transpower declared a “grid emergency”.
With unexpectedly high demand, there was insufficient generation being offered.
The country was using only 12MW less than the generation available at that time.
A “routine power system event”, such as a large generator tripping out, would have resulted in an automatic shedding of almost a third of the nation’s consumers to ensure the power system did not collapse.
The situation is hard to grasp in a country that has always believed it has plenty of electricity. Figures support that. According to the Ministry of Economic Development, last year, New Zealand had a total of 8858MW of electricity generation available from hydro, thermal, wind and other sources. The South Island has 3513MW of generation virtually all from hydro, which is vulnerable in dry years. Of that, 1738MW is generated on the Waitaki system. In consumption terms, last year, the South Island used 14,850 GWh of electricity. The North Island used 15,095 GWh. The South Island has the capacity to generate up to 18,440GWh a year and the North Island 27,560GWh. The projected demand in 2011 is expected to be 15,378 GWh in the South Island and 30,380GWh in the North.
However, that is the peak production that is installed, not the total amount that may be available at any one time.
For example, June’s crisis was compounded by a number of factors that reduced available generation low storage lake levels in the Waitaki hydro system; maintenance work on transmission lines, which reduced maximum generation from the Waikato River system; a weed problem at the central North Island Tokaanu station, which severely reduced output; and no output from the 300MW New Plymouth power station.
Under normal circumstances, New Zealand has electricity to burn.
But get a combination of factors such as that which occurred in June, and we are running close to our limits.
Like it or not, the country needs more electricity for about 25 years it has been living off projects from the 1980s and earlier. The Electricity Commission’s latest prediction is for demand to grow 2.7% over the next few years, falling slowly to 2% by 2015 and 1.3% by 2030. Over the next 20 years, that will require about an extra 3500MW in new generation about five and a-half Project Hayes wind farms. How that demand will be met is where the arguments start. The debate began with Meridian Energy’s Project Aqua power scheme on the lower Waitaki River, cancelled in 2004. It is now focused on the two major wind power projects in Otago. It could also include Meridian’s north bank hydro scheme on the lower Waitaki River, and any other big power projects that may come along.
Key to future generation is the latest Energy Outlook to 2030, produced by the Ministry of Economic Development and released only a month ago.
At present, electricity from hydro represents about 65% of total generation. Most of the rest is thermal coal or gas.
The Outlook wants to reduce that level of thermal production by replacing it with “renewables”: hydro, wind, wave or solar.
It is also suggesting conservation and increased efficiency could play their part, but not to the extent of a major reduction in new generation.
The report points out that conservation and efficiency, particularly in the residential sector, could lead to home owners using the electricity saved in other ways.
Major new hydro generation will be restricted by environmental considerations; Meridian’s cancellation of Project Aqua is used as the example.
“Similar issues are likely to surface in regard to any proposed new major hydro projects,” the Outlook said. Coal-fired power stations will be equally controversial unless the greenhouse gas problem, particularly carbon dioxide, can be overcome. Several wind power projects are proposed. Along with any new project comes a rise in the cost of producing electricity, leading to higher prices for the consumer. The Outlook predicts wholesale electricity prices, driven by gas price rises and new generation, will increase by about 35% by 2030. The Outlook looks at the major forms of electricity generation for the future in New Zealand.
Options for further hydro generation are limited, as many of the best sites have already been developed and there are resource consent issues with those that remain.
There is probably no limit to new gasfired generation, but security of gas supply is an issue, along with greenhouse gas emissions.
Coal is an option, particularly using the major lignite resources in the south of the South Island, but greenhouse gas emissions are again an issue. Its future depends on overcoming carbon dioxide emissions.
Wind generation costs have dropped dramatically over the past few years but wind does have an environmental impact, including noise, visual impacts and bird strikes which can be overcome with proper design.
New Zealand is windy country and has lots of potential for wind generation. It is estimated up to 2450MW can be produced with high reliability and up to 4585MW with high or medium reliability by 2015.
The main limitation with wind generation is that the wind must be blowing. Wind power has to be carefully integrated with other forms of generation.
The large amount of hydro generation would complement wind, because hydro can respond quickly to variations in wind generation.
Meridian proposes to tie its Project Hayes wind farm to its Twizel control centre to integrate with its hydro generation, saving water when the wind blows.
That would reduce the impact of dry years one of the factors in the problems experienced in June.
Wave energy is identified as a new technology with the potential to have a major impact on electricity generation before 2030.
New Zealand’s long coastline, with lots of waves, offers a potentially huge resource.
One manufacturer estimates a 30MW wave farm would take up 1sq km. That would mean about 21sq km to produce the same amount of electricity as Project Hayes.
However, like wind power, wave power would need to be integrated with other sources of generation, it has a high cost and it has limited commercial application so far.
It is predicted the new technology would be taken up gradually 250MW by 2020, 500MW more over the next five years and 1000MW more by 2030.
The Outlook predicts that by 2030, 85% of New Zealand’s electricity could be produced by renewables, halving the thermal production.
This assumes an additional 3300MW of wind, 1018MW of hydro and 106MW of geothermal.
By David Bruce
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