In the lead-up to the 2020 general election, the Prime Minister announced Labour will bring the target of 100% renewable electricity generation forward five years to 2030.
You’ve probably heard the terms renewable electricity and green electricity used a lot lately.
While there are subtle differences, both terms refer to the fuel source used to produce electricity. Broadly speaking ‘renewable’ relates to the sustainable nature of the fuel ie it does not run out. The ‘green’ nature means it has nil (or very low) greenhouse gas emissions.
In New Zealand hydro averages around 60% of total generation and is the largest source of what is classed as renewable power. Geothermal is a significant source of rewable generation and valuable because it is near-continuous output. However, while geothermal is a sustainable fuel-source, it is not zero emissions with CO2 released in the heat capture process.
Wind turbines now contribute an increasing proportion of our renewable energy and accounted for 6% of total generation in the last 12 months
There is little large-scale solar at present and, while this does not currently feature in the statistics, there is significant investment underway. In addition, the Electricity Authority report that over 37,000 ‘roof-top’ solar systems have been installed . Transpower (the operator of the national electricity grid) records show renewable energy at 81.6% for the past year. While this is slightly down on the previous record, it is a very good number in comparison to most other countries (eg Australia 24%).
There are two main factors that determine if there is enough electricity to meet our individual needs and the requirements for the country.
• Capacity – the maximum electricity that can be produced at any point of time.
• Energy – the amount of electricity produced over a period of time.
Generation units are not always going to be available due to breakdowns, maintenance, and in some cases the fact market prices mean it is just not worth producing the electricity. The latter is particularly the case for thermal plant i.e. natural gas and coal where there is a real cost for the fuel, which now includes a significant cost for the carbon emitted, compared with wind and solar where the ‘fuel’ is free.
Will we have enough generation capacity in NZ?
We currently do. However, as happened on the night of 9 August 2021 unless generation assets are ‘primed’ and ready to go, the lights will go out. This will become an increasingly important question as NZ moves to increased electrification e.g. electric vehicles and converting coal fired boilers to electric.
A number of the thermal (gas and coal) power stations are due to be retired shortly and as yet we do not have the replacements built.
Are we able to produce enough electricity?
This is largely a question of fuel availability. Key questions are:
• how much water is stored in the hydro lakes,
• is there enough natural gas and/or coal to operate the thermal stations,
• and increasingly important, is the wind blowing?
Winter 2021 was a challenging time for being able to generate enough electricity. NZ has the generating equipment, but availability of fuel was a problem. Hydro lake levels were well below average at the start of winter and there were problems with supplies of natural gas. The country was reliant on Genesis Energy using imported coal to run the Huntly power station. At times it is was also necessary to use the large diesel fuelled generators based in Hawkes Bay. All in all, 2021 was not a good year for green electricity, but the lights did stay on (most of the time).
When it comes to electrical energy from renewable sources there are even more challenges. Wind and solar are known as intermittent sources of generation. That is, they cannot be relied upon to always be there. While weather forecasting is helpful, there is no certainty the wind will blow or the sun will shine where and when it is wanted. NZ is blessed with geothermal generation. This is a near continuous source and now makes up approaching 20% of our electrical energy needs.
Will we have enough of the right kind of generation?
That, as I will explain, will be the 64 Million (more likely, multi-billion) dollar question
The challenges of 100% renewable.
It’s predicted there will be a significant increase in demand for electricity as part of the decarbonisation drive. With the looming close-down of some thermal plants, significant investment in wind and solar will be required. There are a number of factors to be considered:
• The wholesale electricity market incentivises the current large generators to not invest in additional generation i.e. keep supply tight (and prices high). Hence a handbrake on building new generation.
• The wind does not blow all the time. A good average output is generally around 40% of the wind turbines potential.
• Likewise, the sun does not shine brightly all the time resulting in an average output of 20% of rated capacity for a standard solar array.
• We also know our hydro lakes do not hold a lot of water. They can go from feast to famine, and vice versa in less than 3 months.
• There are technical things to be considered like maintaining voltage, frequency, harmonics, power factor, etc.
Managing towards 100% renewable.
NZ will need a lot of wind and solar generation to make up for the gas and thermal plants that will need to close. At times there will be more than can be used. At other times not enough. This introduces the subject of storage.
• Very large (grid scale) batteries are now a reality. This provides the opportunity to store surplus energy by charging large batteries. This is an option to contribute energy at the time of shortfall, but it is only for a matter of a few hours at best.
• Pumped hydro. A full hydro lake is a kind of battery. The Minister of Energy, Megan Woods, is championing the idea of filling lake Onslow in Central Otago . A working group is investigating the feasibility, but while the concept of pumped-hydro has merit, most commentators question the financial viability. If built, it would provide for dry-year generation but getting the power to the upper North Island is one of the many costs and challenges.
• Storage through converting surplus electric energy into another energy form e.g. hydrogen. Then using this stored energy to produce electricity when needed.
• Distributed Energy Resources (DER) involves electricity provided by small scale generation such as solar on house roof-tops. An electric car battery that still has charge can be plugged in and provide power at peak times and recharge later that day.
• Demand side management is where consumers shift power use to a different part of the day. The example we are all used to is (ripple) control of our hot water cylinders. Most of the time we do not even notice this is happening, but it enables shifting load away from peak times. The smart house concept sees automatic control of our electric devices.
• Other technologies will further develop e.g. tidal and wave generation, bio-fuels.
• And, dare we mention … nuclear. That is a topic in itself, and will require a major shift in societal attitude before we go down that path
So, can the ambition of 100% renewable electricity be achieved?
The technology exists to make this possible and the Interim Climate Change Commission, and others, say we can move from NZ’s current 80-85% to 95% renewable relatively quickly. The big challenge is the remaining few %. The major issue is to provide for periods of low hydro lake levels. The technical and capacity issues would make achieving those last few % very expensive.
Natural gas is the ideal fuel to cover dry hydro years and other eventualities, but this is outside the ambition of the current Government.
NZ is different to virtually every other country in that we have a single integrated power system with no interconnection to and, therefore, no support from neighbouring transmission grids e.g neighbouring countries or states
100% renewable electricity is a laudable objective. However, the realities of achieving this by 2030 will be very costly and, at times, could compromise the security of our power system.
So, to answer the question, yes, given enough investment and commitment NZ can reach its target of generating electricity from 100% renewable sources. However, the Minister should heed the advice of a range of experts and provide for an extended transition timeline for thermal fuels to provide security of supply while we implement the systems needed to take us from the achievable 95% to 100% renewable.