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24/7 renewables power?

By Geoff Carmody - posted Thursday, 14 July 2022

'Free' sunlight, wind, and rain? Sure. Weather's 'free'. It's also beyond our control. A rational energy policy review would:

Let known technologies drive transparently determined, evidence-based, cost, reliability and emissions outcomes.

Use these outcomes to decide the best cost, reliability and emissions policy 'mix', not the other way around.

Are renewables the cheapest power? Only when available? How about 24/7? What's the evidence?


We can't plug sun, wind or water into power points. Harvesting these comes first. The cost of that includes renewables generation, storage, transmission, equipment disposal, etc.

The government now draws voters' attention to power transmission ('poles and wires'). This is a big issue indeed. Optimal renewables generation sites often differ from fossil fuel deposits. More, and more specialised, 'poles and wires' are needed, (see AEMO).

'Poles and wires' deliver 24/7 renewables only if enough power can be generated and stored to transport to users in the first place.

Before worrying about 'poles and wires', worry about adequacy of renewables generation,and power storage, and technology.

i. Generation is delivered by PVs (solar), turbines (wind, hydro), and freely-flowing water (hydro).
ii. Storage requires manufactured batteries (tiny to large manufactured batteries for solar and wind, artificial dams for hydro).

Technology is lowering costs and increasing efficiency. That's good. However, intermittency is a big deal for reliable power, 24/7.


How big? A numerical example, (there are many others), based on past actual South Australian data, shows this for solar and wind.

i. On average over a year, solar generates full power about 15% of every day, and zero for the rest.
ii. On the same basis, wind generates full power a bit over 30% of every day, and zero for the rest.
iii. Solar power varies with the seasons (most in summer), latitudes (most in lower latitudes), cloud cover, etc.
iv. Wind power is geographically and weather-variable. Some places (not least offshore) are more consistently windy.

Suppose solar power is available every day for 15% of the time. For 24/7 power supply, effective generation capacity must be about 6.7 times as much as the equivalent effective fossil fuel generation capacity. Daily power must all be generated when the sun shines.

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About the Author

Geoff Carmody is Director, Geoff Carmody & Associates, a former co-founder of Access Economics, and before that was a senior officer in the Commonwealth Treasury. He favours a national consumption-based climate policy, preferably using a carbon tax to put a price on carbon. He has prepared papers entitled Effective climate change policy: the seven Cs. Paper #1: Some design principles for evaluating greenhouse gas abatement policies. Paper #2: Implementing design principles for effective climate change policy. Paper #3: ETS or carbon tax?

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