The old-school energy grid is on the nose. It still dominates the global supply, but all the talk is of renewable grids dominated by the on-again off-again poster children of the renewable revolution; wind and solar. Like Donald Trump, these technologies reckon that if they keep saying they are doing a tremendous job, reality will eventually fall into line.
Dealing with climate change makes it imperative that we decarbonise our energy infrastructure, but why focus on wind and solar to do it?
Old-school grids are dominated by continuously running generators that you feed with fuel; be it uranium, coal, gas, thorium, recycled reactor waste, repurposed nuclear weapons material (a personal favourite), forests (yuck), crop waste (what a waste of good soil conditioning organic matter) waste wood (ditto), manure (ditto) etc.
Peaks in demand, whether predictable or not, are serviced in traditional grids by additional generators fired up for the purpose. I've long called it the city lunch-bar model. A city lunch-bar has a few permanent employees who work all day and then a few casuals arrive to handle the rush of customers at lunch time. Some times of the year are busier than others and you need more casuals; easy. Lunch bars all over the planet seemed to have hit on this as a sensible mode of operation.
The gig economy, in contrast, opts for all casuals and zero permanent staff (except perhaps for a small elite team who actually reap the profits). In the most extreme cases, the gigiest of the giggis, people choose when to work ... like Uber drivers.
Wind and solar are the gig-technologies of electricity. They are like Uber drivers; they choose when and if they'll work. Except that they aren't like Uber drivers in that they don't have any idea of maximising their income by choosing to work when demand is at its maximum. They also don't see the value of working when everybody else is on a break; like Christmas day. In fact, they aren't really like Uber drivers at all! They don't choose anything. They are beyond gig.
About the only thing wind and solar farms have in common with Uber drivers is that they have a faithful fan club; people who love superficially-cheap and don't think about the total system cost or reliability.
Studies have shown that services like Uber and Lyft create congestion and increase travel times ... on average. But if you are only interested in your own travel plans, then who cares about the system impact?
Similarly with wind and solar; people are easily seduced by the cheap cost of marginal increases in electrical capacity and don't consider how these may bugger the system in the long run. This is partly because the full adverse impacts only emerge at high levels of penetration when the stability provided reliable dispatchable electricity sources is gone. It's like when a lunch bar sacks the permanent staff and realises that the casuals don't actually have a clue about many of the required tasks.
The 2018 Shaner et al study explained the big problems of basing an electricity system around wind and solar with great clarity and generality. But the generality of the explanation is a problem. Fine for experts, but the rest of us think best with examples. We all tend to muddle through problems by understanding little pieces at a time; and it often takes us multiple exposures before we have that "ah ha!" moment of clarity.
So I'll try and explain the problems of 100 percent renewable systems in a series of small steps.
Step 1. Demand
Here's a single week in South Australia in December of 2019. And yes, I chose it because it was special ... a horror heatwave ... 4 days over 42 degrees C in succession. You can see the peak demand swing from well under 2000 mega watts on Saturday 14th to over 3500 mega watts on Friday the 20th of December. Friday was when our bush fires started; like I said, it was a horror week.
Step 2. Add in the Wind Power ... and double it!
South Australia, where I live, has the highest penetration of wind power in Australia. On some days it can supply over 100 percent of our demand! The next graph shows how it behaved during that week from hell ... except that I've doubled it! Why? I want to illustrate where we are headed. We are still building wind farms, so this example could also be a prediction of our future.
But notice something weird.
The minimum output from our wind farms matches almost perfectly the maximum of our demand on the hottest days. That's not a fluke ... it's incredibly common during South Australian heat waves. I first became aware of it by seeing a similar graph in an Australian Energy Market Operator report back in 2010. So when we desperately need electricity at the end of a really hot day, wind power is about as useful as solar power after dark.
Time to add in the output from our solar farms and all those rooftop systems. If we are lucky, that might even up the two graphs a tad.
3. Add in the sunshine ... and double it!
This graph shows aggregate output of wind and solar technologies. You can see how on Saturday and Sunday, the 14th and 15th of December, we had massive peaks in wind+solar power, way above demand. But then we had four days where we needed either local fossil fuels or imports from the eastern states (also mostly fossil fuels). Friday the 20th is a shocker, wind plus heat. This was the day our bush fires began to cause depair and destruction. Keep in mind that the yellow line in this graph is double what it actually was.
4. Lets add in a really, really big mother of a battery.
A battery would help, so lets add one.
How big? South Australia installed what was the biggest Li-Ion battery on the planet back in December 2017. It is still one of the biggest. It has recently been upgraded and can supply about 100 mega watts for about 2 hours. Keep in mind that the South Australian demand is typically 1000 to 3000 megawatts.
So I'm going to pretend we had a 6000 megawatt hour Li-Ion battery. Nobody is predicting anybody will have anything like that for 10 to 15 years, so again. I'm modelling the future in nice manageable steps. But my pretend battery is much better than a real one. It has perfect efficiency, can handle any charging rate and any discharging rate. I'll show it on the graph as a blue line. When the battery is fully charged the blue line will be on the 1000 megawatt line. If I had it up at 6000 megawatts, it would get in the way! No matter. You can see the line rise and fall as the battery charges when there is extra electricity and falls when there is a shortfall.
You can see that the battery discharges overnight on the 14th and 15th, gets only a small charge on the 16th. Then on the 17th, it gets lucky and hits full charge with a really windy night. Then it's pretty much flat until Friday the 20th.
I chose 6 gigawatts because that's a rounding up of the 5.6 gigwatts that Ian Lowe recently cited as being predicted on the entire NEM by 2035 ... assuming it was 5.6 gigawatt-hours. So I'm modelling a really very large battery for a very small part of the Australian grid!
5. The net shortfall ... with double our current renewable output!
The next graph shows the shortfall, taking into account the huge battery and double the wind and solar infrastructure we've built over the past 15 years. The shortfall is in purple and there's table summarising the week. All up, our doubled wind and solar resources generated 313 gigawatt hours of electricity (a gigawatt hour is a 1000 megawatt hours). Without the battery we'd have been short by 81.98 gigawatt hours, but with it, we were only short by 53 gigawatt hours.
We threw out about 12.44 gigawatt hours when it was windy and the battery was full.
What's next? Let's triple the wind and solar output!
Okay, in a decade we may have doubled our wind and solar power. But now that we know that double that amount isn't enough ... why not aim for triple! Now that you've seen the layers, I can just jump straight to the prize ... the final image. You can see that we get 129 x 5 minute periods during this single week where we don't have enough electricity ... despite throwing out about 1/4 of the electricity we produce.
But wait ... why not go for 4 times the wind and solar output?
This my seem extreme, but it is consistent with the kinds of overbuild that renewable advocates have been finding (and recommending) for years. A frequently cited UNSW study needed 24 gigawatts of wood fired generators (in a grid with a peak demand of 33 gigawatts) to avoid too many shortfalls in its "100 percent" renewable modelling. Renewable systems just keep layering on the paper mache over the cracks and people keep cheering.
So let's quadruple our renewable output.
With quadruple the output, we are throwing out 42 percent of the electricity we produce and we still get a couple of dozen 5 minute shortages ... in just a single week.
But surely these problems are because I chose a weird week?
No. Within reason, it doesn't matter how much wind and solar power you add in, you will exhaust all but the most extreme of storage systems. In the Shaner study I mentioned earlier, they modelled having 32 days worth of storage for the entire US electricity supply! Which would be fine if batteries grew on trees; they don't.
So here, as an illustration, is a graph for the beginning of May 2020 ... this month. Again, we assume four times the current renewable output and a 6 gigawatt hour battery. We had a couple of really still nights and it takes very little time to drain even a really large battery like 6 giga watt hours.
The Shaner used a full year's worth of US data and generalised the problem by allowing the ratio of wind to solar power to vary, and generalised the size of storage available ... up to a maximum of 32 days!
The bottom line was clear. Still nights over a wide area are common and will overtax all but the most ridiculous (meaning financially and ecologically costly) storage.
Bigger batteries and hydro schemes
The problem for builders of batteries and hydro schemes is that these technologies are intrinsically costly, not just financially. They are both predicated on big holes ... either for mines or water storage. Building them to pickup crumbs left over from high levels of wind and solar power is hard to justify. At the same time, using a massive wind and solar overbuild isn't environmentally benign either. The supposedly cheap cost of wind power soon vanishes if you need 3 to 4 time more of it. And when 3 to 4 times more of it still isn't enough, how are the holes to be plugged? Burning forests? Flooding valleys? Or rolling out hundreds of thousands of tonnes of battery chemicals?
And then there's the elephant in the room, nuclear power
My final image is of a nuclear plant in Switzerland ... Leibstadt. You can see it at the centre of the image ... it's a small point on a map. The big square is the area of solar farms you'd need to get the same amount of electricity annually that Leibstadt delivers (using a couple of hundred tonnes of uranium). The area of the big box is equal to 40 Nyngan solar farms, covering 10,000 hectares with 54 million CdTe panels. These panels contain cadmium, the Cd part of the CdTe. Cadmum is toxic and carcinogenic ... forever. In addition, the backing sheets on solar panels are a recycling nightmare ... most contain Fluorine ... you can't burn it and burying isn't simple either. But for some bizarre reason, solar is regarded as clean and nuclear isn't. It's time we all realised that the goal is of building a clean carbon free energy infrastructure is harm minimisation which isn't helped by pretending that some things are perfect and others are the devil's spawn.