The sun doesn't always shine and the wind doesn't always blow!

Reading time: 5 minutes

TL;DR

Hot take

WHAT?!

Actually chalk another one up to Captain Obvious. We know. We’ve known for millennia really.

Why do people drop this pearl of wisdom as if that rules out renewable energy generation?

Explanation

People love throwing this out there to spread doubt and uncertainty about renewable energy. They play on the fear of electricity not being available in order to promote some fossil fuel project. Using words like “firmed”, or “dispatchable” - if you’re really lucky you’ll get a “baseload” but most people realise what an outdated concept that is now.

Well how are we going to deal with intermittent solar and wind generation? There’s a few things available

  • Overbuild
  • Batteries
  • Pumped hydro
  • Demand management
  • Hydrogen

Overbuild

Build more capacity than you need - for example, 150% or 200% and store the excess energy. The costs to deploy solar and wind are getting so cheap we can go beyond a 100% replacement and build more. Diversification of geography also helps mitigate intermittent weather - because chances are the sun is shining and the wind is blowing somewhere else. You can read more about overbuilding here.

We know about wind patterns, wind is even forecastable. The financial backers of multi-million dollar wind farms don’t just plonk them down in random locations.

Batteries

We can store energy in batteries, both grid-scale and people’s homes. Home batteries are becoming more common and allow people to store their excess solar and use it through the night, or at least avoid drawing from the grid during the peak morning and evening periods.

Grid-scale batteries are coming online and in some cases replacing coal fired power plants. These also soak up the excess solar and wind during the day and use it through the night.

Pumped hydro

Pumped hydro can also play a part. We know hydroelectric dams generate electricity when the water runs downhill, what if we pumped some of that water back up and did it again? Well the laws of physics means we can’t do that for free. That’s where excess renewable electricity comes into it.

With a large deployment of solar and wind on sunny, windy days we’ll have too much power - more than is needed, so we can use that to pump water back up hill into the dams. Hydroelectric dams also have a role to play in water management, it’s not all about the electrons - so there are considerations for what is happening downstream as well, flows can’t drop below the minimums needed for the environment or townships that rely on the water. At the same time, a full dam can’t store more water if there’s more flowing in - where have I heard that analogy before.

Demand Management

The electricity grid is a constant, ongoing game of matching supply with demand. In order to maintain the correct voltage in the grid the operator of the grid has to constantly ensure there is enough - but not too much supply feeding into it. It’s large enough that somebody at home turning on their light makes no difference to the grid, but large facilities such as factories and smelters can definitely have an impact on grid demand.

Demand management is a term that talks about the coordination efforts to orchestrate usage, or demand at different times of the day. This could be done intelligently with fancy gadgets - e.g. tell the batteries in this part of the grid to charge up because we have too much power, or through market based approaches such as the price of electricity.

In Australia as an example, the price of wholesale electricity varies throughout the day. When the sun really is cranking and we have more than 100% of electricity than we need the price can even go negative. This means there is a disincentive to generate electricity, in fact there is now an inventive to use electricity. If you were on dynamic pricing this is how you could get paid to charge your EV, your home battery or run your aluminium smelter.

If you’ve ever had an electricity plan that costs more during peak, and has off-peak pricing - guess what, you’re already in market-based demand management.

Some of this could be as simple of time-shifting loads into the middle of the day when there is likely to be excess electricity. I once saw an example of a large frozen food facility that was lowering it’s temperature beyond what was needed during the day when it was cheap - soaking up excess electricity so that it could then get through the night without needing any further electricity at all. Prior to that it would have just drawn an average throughout the 24 hours.

Hydrogen

Hydrogen may play a role in this storage as well in stationary situations. With excess electricity, turn on the hydrolysers to convert water into hydrogen and store that. When the sun isn’t shining and the wind isn’t blowing burn the hydrogen to generate electricity. The output is water.

I don’t think hydrogen will play a large role in the transport sector, but I think there are uses for it in these industrial and stationary uses.

Alumni

Cool people who have dropped this line of logic into the debate about the transition to renewable energy.

Further reading


Last updated: March 2024