Guest Post by Geoff Russell. Geoff recently released the popular book “Greenjacked! The derailing of environmental action on climate change“.
My previous BNC post started with a story about satnavs, those great little replacements for a dog-eared street directory. Everybody understands the value of planning a route. Everybody understands that just because a road is heading in the general direction of your destination, it may not be good choice; let alone the best choice.
It might be a dead end or take you on a long circuitous route to or past your destination. Everybody knows this but when it comes to climate change, it’s as if basic smarts take a holiday and anything that can demonstrate a CO2 savings (i.e., heads in the general direction of a solution) produces cheering and cries of victory. The article went on to show that we’ve wasted over a decade with biofuels because they demonstrably cannot decarbonise our transportation system. Not ever. It was an easy argument; a slam dunk, a lay down misere.
But what about renewable energy? Specifically wind and solar? Are these dead end technologies? It certainly isn’t a slam dunk, but lets examine what’s been happening in South Australia for the past decade.
On Sunday the 8th of February, South Australian Premier Jay Weatherill called for a Royal Commission into all things nuclear after a long political history of being anti-nuclear and after being heavily involved in the past decade of wind and solar roll outs in South Australia.
This launched a small flurry of opposition with Greens Senator Mark Parnell rejecting the call with claims about any involvement in the nuclear industry by SA leading to dirty bombs; SA Conservation Council CEO Craig Wilkins invoked a threat to our clean food image. Following an op-ed by me in the Adelaide Advertiser, Wilkins followed with a letter claiming that SA couldn’t possibly have a nuclear reactor within 10 years, and went on to say that (Advertiser Letters 18th Feb):
credible commentators are suggesting that SA could be 100 percent renewable in 10 years
Why have nuclear inquiry if success is imminent?
What on earth is going on? If SA could have 100 percent of its electricity being generated by renewables in 10 years, I’d certainly be cheering and dancing in the street. And what’s with Weatherill? Doesn’t he have any “credible commentators” on his staff? Or is he getting advice from real engineers instead of credible commentators.
Let’s look at the numbers.
First a couple of interesting graphs from AEMO’s 2014 South Australian Electricity Report.
The next table shows electricity generated in SA by generator type:
SA got it’s first “big” wind farm in 2003. So these two tables summarise a decade of renewable growth. With rooftop PV beginning in earnest in about 2008.
The rise in electricity imports pretty much tracks the rise in rooftop PV but is more than double the size. Our net imports of electricity in 2013-4 were 1700 gigawatt hours and our rooftop PV was 709 gigawatt hours. This table doesn’t tell us how much coal or gas has been displaced by that PV, but any CO2 savings have probably been exceeded by importing some of the dirtiest (in terms of CO2 per kilowatt hour) electricity on the planet … Victoria’s brown coal.
Okay, so in 10 years we’ve gone from effectively zero renewables to getting 37 percent of our electricity from wind and solar. Does that mean that we can get to 100 percent in just under 20 more years; by 2035? Where on earth does the figure of 10 come from? Wilkins didn’t name his credible commentators.
What do the graphs tell us? The crash in imports beginning in 2006 is probably best explained by the raft of wind turbines which came on-line in 2005 and added significantly to SA’s homegrown generation capacity. But then as PV renewables grew, coal and gas operators here got priced out of the market, ramped down their production so shortfalls got met instead by imports of dirty electricity from Victoria.
We have two interconnectors with Victoria, one is normal AC, that’s called the Heywood interconnector, and the other is HVDC, that’s Murraylink. If you don’t know the difference between HVDC and AC, then keep reading, its important!
AEMO released a second report toward the end of last year and it’s really interesting reading. It’s about how to integrate renewable energy into the grid. What? Why do people write reports on that? Don’t you just plug it in?
Back in 2012 CSIRO did a major study called Solar intermittency: Australia’s clean energy challenge. Talking about the report, a CSIRO expert was asked at what level would the intermittent character of solar start having an impact.
Dr Glen Platt: … The short answer is we actually still don’t know. It depends heavily on the particular situation.
It’s now a couple of years on, presumably the issue is still being studied but the AEMO report contains a bombshell. I’m sure it’s not a surprise to power engineers, but it is probably a shock to the rest of us. Suppose we had all the wind and solar power we needed to generate all our electricity and we shut down all the coal and gas. Yes, that’s 100 percent renewable. Except that it isn’t, because without that interconnector we’d be toast. Or rather, we’d be bananas, because we’d all have to keep some raw food on hand to deal with statewide blackout risks. Here’s what they say:
Where SA has zero synchronous generation online, and is separated from the rest of the NEM, AEMO is unable to maintain frequency in the islanded SA power system. This would result in state-wide power outage.
This statement just says that a 100 percent renewable system would result in a state-wide power outage if the interconnector between Victoria and SA went down. In 2006, 200,000 homes in Victoria lost power when bushfires took out an interconnector between Victoria and NSW. So bushfires can take out interconnectors. Do we ever see bush fires in Victoria?
Now what exactly is this “synchronous generation” that was mentioned? How on earth can a grid fail if there’s plenty of electricity? There’s no shortage of modelling from people like Mark Diesendorf showing that with enough intermittent power supplies you can eventually have enough kilowatts on hand to meet demand. Just like you can run a restaurant with 100 percent narcoleptic casuals who nod off from time to time … you just need more of them. For example, AEMO calculates that wind power can only be relied upon for 8.6 percent of it’s stated capacity. So, for example, in SA we have 1200 mega watts of wind capacity, but in summer, when our peak demand is 3,300 megawatts all we can rely upon from wind is 103 megawatts. So while theoretically you can power the state entirely with wind power, you’d need 38,000 mega watts worth of wind farms, about 31 times more than out present amount.
But this isn’t AEMO’s concern in the above paragraph.
AEMO is saying, in effect, that it doesn’t matter how much electricity you have, you still need interconnectors. Why? Because power engineering is far more complicated than simply having enough watts on hand. When you read power engineering reports there are words like frequency, reactivity and inductivity, that don’t get a mention in 100 percent renewable modelling studies frequently cited by 100 percent renewable advocates (for example).
We use AC power. The AC means “alternating current”. The voltage at a power point oscillates between plus and minus 240 Volts 50 times a second, so the current, the electrons, move backwards and forwards. The frequency is kept very precisely at 50 cycles per second because some kinds of electric devices, particularly turbines, will go off line (‘trip out’ is what engineers call this) if the frequency drops too low or goes to high and the tolerances can be very fine.
What kinds of things screw up the frequency?
At 6pm or so when a large number of people start to prepare meals and the system is put under load, the frequency can drop. But those big spinning turbines in power stations act rather like flywheels and smooth things out. If that isn’t sufficient, automatic circuits kick in to shed load to keep the frequency within specified limits. Load shedding is a polite way of saying that some areas get blacked out. These big turbines are synchronous energy sources and that’s why we still need to be connected to places with turbines. It doesn’t matter what is driving them, it could be wood, coal, gas, geothermal, nuclear, or even solar thermal, it’s the turbines that are the key to maintaining frequency. In Germany, unlike South Australia, they are burning half of their forest output to make electricity and they are making more from this source than either solar or wind. This gives them a significant source of synchronous generators; just like Victorian brown coal supplies ours.
But don’t we have two interconnectors? It would be a freak to lose them both. That’s where the HVDC and AC distinction matters. The HVDC interconnector supplies DC and that won’t help with the frequency issue. So again, it isn’t just watts that are required, it’s the massive spinning turbines.
The relationship between alternating current and alternating voltage is also characterised by two other measurement of reactivity and inductivity. These are also important, particularly when you are running big electric motors.
Different types of devices can affect a grid differently. Turning on a bunch of hot plates does slightly different things to a grid from a bunch of air conditioners. The latter can change the relationship of the voltage and current waveforms and that matters. Similarly, having the wind start or stop blowing also causes disruption to electricity systems.
When engineers analyse the grid’s response to load changes, they look at all these things. The problem is that nobody knows how to model a grid without large synchronous sources. The AEMO study is very explicit about this.
The challenge of how to best model PV in power system dynamic studies is presently an active area of international research. Given the high levels of PV generation currently installed in SA, and likely to be installed in future, AEMO and ElectraNet plan to incorporate dynamic PV generation models into future studies when available.
“High”? They said “high” but it’s only 6 percent!
Scientists and engineers can model some very complex things, but can’t yet model an electricity network with even 6 percent rooftop PV. What can possibly be so hard about it? That’s the thing with modelling, some things sound really complex but are actually pretty simple, and vice versa. Readers may have heard about a problem called the “Travelling Salesman Problem”. It involves finding the route with the shortest distance for a salesman who wants to visiting a set of customers. Does this sound very much like the satnav problem? Yes. But it turns out to be harder. Much, much harder. People typically use networks of computers to solve largish versions of this apparently simple problem. By largish, I mean 85,000 locations. Is the problem of modelling a grid with a million small power sources easy, like the satnav problem, or hard, like the TSP problem? I’ve no idea, but if it were trivial, there’d be plenty of models floating around. So it isn’t trivial, but whether it’s really hard or not, I don’t know. But the fact that nobody has done it yet might just be a clue.
But we should return to the goal of our renewable roll out. It’s not a game, we really need to decarbonise our electricity, and further, we want to electrify as much of our transport system as we can. The goal isn’t to open up new fun fields of engineering. If that’s necessary to achieve our goal, then fine, but it isn’t an end in itself. And how is our renewable decarbonising going?
Using the table above, and some IPCC factors for the grams of CO2 per kWh of various electricity generator types, then we can calculate roughly the grams of CO2 produced per kilowatt hour in South Australia. In 2013-14, using the above table, I estimate we are generating about 436 grams of CO2 per kilowatt hour. That’s down from 451 in the previous year. More accurate calculation using local data by Ben Heard in a forth coming paper indicate that this is a large underestimate with the real number being around 600 grams of CO2 per kwh. France with nuclear power has been generating close to 70 grams of CO2 per kilowatt hour for the past 20 years. Sweden is very roughly 50/50 nuclear and hydro and they are down to about 20 grams of CO2 per kilowatt hour.
In the French case, it’s not just a matter of clean electricity, it’s impacted the total energy supply. Remember, energy is not just electricity but if you have plenty of clean electricity you can use it for other things. So a better measure then grams of CO2 per kilowatt hour is tonnes of CO2 per terajoule of energy. There’s a recent IEA publication which gives just that. Between 1971 and 1985, France went from 65.1 to 42.2 tonnes of CO2 per terajoule (and she’s now down to 31). Compare that 23 unit drop over 14 years with the German data from 2000-2012 (the latest available), the renewable roll out has taken them from 58.6 to 57.7 … a tiny drop.
So our renewable experiment, like the German renewable experiment, is just that, an experiment with an energy source that is slow to build and which nobody knows how to manage at the levels of penetration required. On the other hand, engineers know how to build grids with nuclear power stations. They are just large synchronous electricity sources with well understood characteristics. The issue is whether we want to continue with wind and solar and pray that it isn’t a dead end, or go with what we know will work and work quickly. Even if it isn’t a dead end, we are still decades away from decarbonising electricity, and there’s plenty to do after that. We need to replace ALL fossil fuel use; among other things.