My piece for the National Interest is now up. It ran under the headline “The end of the nuclear renaissance”, but that’s only half the story and probably the less interesting half. The real news of 2011 was the continued massive drop in the price of solar PV, which renders obsolete any analysis based on data before about 2010. In particular, anyone who thinks nuclear is the most promising candidate to replace fossil fuels really needs to recalibrate their views. There’s a case to be made for nuclear as a backstop option, but it’s not nearly as strong as it was even two years ago.
Feel free to comment here or at NI.
John Quiggin 
The system-wide demand profile (e.g. across a whole State or big city) might look different from a local demand profile, and different local areas (e.g. residential area vs a commercial or industrial area) might look different from one another (e.g. residential peak in the evenings, commercial peak during the day). And individual houses will have different load profiles (e.g. earlier risers or people with off-peak hot water will have higher load at night than other households).
So the local distribution system might happen to get overloaded during the middle of the day in some areas, even though the system-wide peak occurs later in the day. PV might be good in reducing local peak demand and reducing the need for investment in local distribution infrastructure (forgetting about intermittency for a second), even if it isn’t well matched to a system-wide peak and won’t offset the need for investment in transmission or big generation infrastructure by much.
Steve, looking at the data for Adelaide we have a huge peak in the summer. We can use a lot of electricity in the winter, but the peak use is definitely and clearly in the summer when the sun is up. I assume that in places that are less coldtastic than Adelaide in winter, the summer peak is even more prominent. Demand normally drops at 5:00 pm as businesses close, but in heatwave conditions demand can stay high until the sun sets, at which point demand drops because the sun shining on things makes them hot. If cloud cover drops electricity generation from PV then it drops the amount of sunlight making stuff hot, so not much of a problem there, especially since our PV is all higgly piggly so one cloud isn’t going to do much, and if a storm blows in we’re set because of all the wind power we have here. I don’t know where you are, but if you don’t have wind turbines I recommend getting some. They’re pretty cheap these days. Not as cheap as I’d like them to be, but on the plus side I’ve never seen a wind turbine grab a Thai person and hold them underwater until they drown.
Oh, and as for solar producing the most electricity at noon, yeah, it’s weird but no matter what type of solar cell is used, silicon, thin film, whatever, they all end up producing the most electricity when sunlight is the strongest. So if you are paying spot prices, I’d suggest looking into angling your solar panels to the west to maximise money saved, or you could look into using one or two axis tracking. (One axis is plenty in my opinion. Use the good axis and keep the other as a spare in case you ever need one for a State of the Union Address or something.) And if you aren’t paying spot prices, it might be best to just maximise kilowatt-hours produced.
Steve, PV might overload the local distribution system in the middle of the day? What year do you think this will happen in? Will we have sassy, wise cracking, robot companions? More importantly, will we have roboprostitutes? (I am asking for a friend.) Even more importantly, why will people in the future not realise that they are about to overload local distribution systems and do something about it? Have aliens used foresight sapping rays on humanity to soften us up for an invasion? Or are the wind turbines behind it all and their niceness was just a facade?
Personally, I think that if point of use solar PV ever becomes cheap enough that so much is installed that local distribution systems becoming overloaded in the middle of the day is a problem, then the problem is like my problem of not being able to fit more than eleven ferrero rochers in my mouth at one time. It’s not a real problem, and only one that people who are fantasically fortunate in the great scheme of things will spend any time considering.
this just posted:
http://www.science20.com/science_20/fight_snobbery_maybe_solar_efficiency_good_enough-85973
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Hi Ronald. I am not and have not talked about PV overloading the local grid, though I can see how you got this impression from my confused writing.
I was talking about whether or not PV is well matched to reducing peak demand. And when I mentioned overloading, I was referring to your earlier point about having brown outs. You were suggesting that brownouts occur “when the sun is shining” ie when PV output is available, as part of a point that PV output is matched to peak demand. I was suggesting that although some areas might see middle-of-the day peaks and get brownouts then, it still remains that pv output does not peak at the same time that demand peaks in other areas, or system wide.
See this paper for a comparison of PV and local demand in summer in NSW in residential areas vs commercial areas:
The Value of PV in Summer Peaks
Steve, solar power is well matched to meet peak demand. And by peak demand I mean the big peak that happens on hot, sunny, summer afternoons. Solar power does not perfectly match demand, but it matches it better than wind or coal. If it is cheaper to use than natural gas, then solar PV should be the most economical way to reduce or meet summer peak demand.
Click to access value%20of%20PV%20in%20summer%20peaks.pdf
A study of the value of PV in summer peaks. Some interesting comparisons by graph of residential consumption versus commercial comsumption.
The link suggests a couple of ways that PV could be made more compatible with late afternoon air con demand. One way is to tilt fixed panels to the west to catch the setting sun. Another is to charge higher electricity prices so households supply more or demand less. Elsewhere I’ve seen suggestions that PV could chill a tank of water in the middle of the day so that the air con draws on it as a heat sink late in the afternoon. None of this helps the 7 am rush for coffee and toast or heavy industry powering through the night.
Hermit, do you know anyone who expects solar power to work at night? ‘Cause my guess is the number of people who think it works off neutrinos is rather low. And do you know anyone else who expects solar not to work during the day? You see, for some bizarre reason, in more than half of Australia the sun always rises before 7:00 am and in the rest of Australia the sun always rises before 7:00 am more than half the time. (I understand a guy called Copernicus is working on a reason why this should be so.) During a Brisbane summer it is possible for fixed panel PV to produce electricity at 10% of capacity by 7:00 am and single axis tracking PV can produce over 50% of capacity. Even tracking PV is considerably below its peak at 7:00 am, but electricity consumption is also considerably below its peak at that time. Anyway, Hermit, I’ll grant you that solar solar power doesn’t work at night, if you grant me that the sun rises before 7:00 am in most of the country.
* PV is not “well matched” to peak demand. Max PV output is at 12pm-1pm. Peak demand is at 3pm-4pm in Summer. So – presuming there are no clouds – PV output will be 30-40% of rated output when demand is at its peak in summer. PV is somewhat matched to peak demand, not “well-matched”. But then, there only needs to be a single day where cloud cover quickly increases, after a really hot series of days when demand is at its peak, to ruin this. Despite what you’ve said Ronald, it takes a long while for hot buildings to cool down and for people to switch off their aircon, and demand doesn’t magically fall as soon as clouds appear. The intermittency of PV will hurt to some degree its potential as a reliable source of power during times of peak demand.
* Tracking. When I was working in PV over 10 years ago, it was common thinking that tracking systems for flat-panel 1-sun PV systems* were not especially economic (e.g. the old Singleton Solar Farm, over 10 years old, did not include tracking). Instead of incurring additional capital and maintenance cost, it was better to simply spend the money on more panels. Now that solar panels are much cheaper, this would be even more the case.
*Peak demand vs greenhouse gas abatement. When you face panels west, or spend money on tracking instead of more panels, you reduce the total energy generated and therefore reduce the greenhouse abatement. The best bang for buck greenhouse abatement is to face panels due north, without tracking, and spend the money you might have spent on a tracking system on more panels. In my view, PV should be thought of first and foremost as a greenhouse gas abater, not as a peak generator. The peak demand stuff is a distraction (one that becomes more and more irrelevant as the price of PV falls, since it is all about trying to improve the economics of PV), and just unnecessarily focuses people’s attention on the weaknesses of PV as a peak generator. Leave peak demand for gas and hydro, and PV and wind can do their job, which is greenhouse abatement.
Forgot the *:
* Tracking makes more sense for industrial concentrator PV systems such as the ones produced by Solar Systems, because the PV arrays used in such systems are very expensive.
@Steve
“In my view, PV should be thought of first and foremost as a greenhouse gas abater”
In my view, once the cost of global warming is properly internalised (with an appropriate carbon price), this should be a purely commercial decision. If we had a real carbon price, I would want generators to be simple profit-maximising animals. They should tilt panels at whatever angle serves this end.
Steve, you are confused. You linked to a report earlier on the value of PV in summer peaks. Go read it. It says what I have been saying, solar PV is well matched to peak demand. If you still say I’m wrong, please make clear whether your disagreement is with the report or just how good I use English.
You say solar should not be thought of as a peak generator. So do you know anyone who thinks of solar as a peak generator? That is, people who think that the sun and weather are controled by electricity use, or vice versa? I don’t. (Well I did, but he died chopping through a power line with an axe to create an eclipse.) Now I could understand that if someone thought solar PV worked like a gas turbine they might think that it didn’t match demand well, but who the heck thinks PV works like a gas turbine? Even the dead guy with the axe didn’t think that. For something we have no deliberate control over, PV matches peak demand well. It matches it better than coal, wind, geothermal, or nuclear. Considering that we have no control over the sun and clouds (although we can predict them fairly well) the fact that solar PV helps meet peak demand is pretty groovy.
And dude, here in Adelaide noon is at 1:23 today. If it’s clear, north facing fixed panel PV pointing will produce over 60% of capacity at four o’clock. And the sun will set at 8:33. What are the figures from where you live? If you’re in Australia I’m sure they’re different from the ones you gave.
So, do you know anywhere in Australia where solar PV would not help meet peak demand? I mean an actual real place. Maybe you should check the figures for Tasmania?
I read the report Ronald, and I’m not confused. It shows that PV output is not well matched to peak demand in residential areas. It shows that PV output is well matched to peak demand in commercial areas (assuming no cloud). It says little about system-wide peak demand (graph of vic summer peaks vs pv output is shown), but remarks that peak demand lags PV output somewhat (as I’ve said, and as is shown in the graph).
My numbers came from an ausgrid report, that I’ve attempted to link, but it keeps getting caught in the spam filter. Google “ausgrid pv peak demand” and it will come up first.
Its for places in NSW, where I live. See page 4.
I think that PV generators and electricity retailers will hopefully be able to benefit from selling electricity at times when prices are high, because they do produce electricity at times when prices are high and load is generally higher. But as a means of contributing to a deferral in investment by helping to reduce peak demand, less useful than is sometimes made out.
Steve, we are only approaching grid parity for low installation cost point of use PV. That’s the sort of thing that goes on large flat roofs. The sort of roofs that are found on commercial and industrial buildings. As for PV not matching residential area use, currently that’s not a problem. In Australia the electricity usually comes from more or less the same place. Where I am, the coal, gas, and wind generators all supply electricity to residential, commerical, and industrial areas, so if solar PV results in residential demand being lower than what it currently is, that makes it easier for them to meet demand in other places. There’s only a problem if residential areas start generating more electricity than they use, but that’s not going to happen for some time, if ever.
Looking at page 4 of the Ausgrid report, I see why you are confused. Firstly, the time of day is screwed up. They give eastern standard time when in summer Sydney runs off daylight savings time, so the actual maximum PV output happens and hour later than what is given on the graph. Secondly, what they give as capacity is not what I call capacity. You see, they have summed together the output of thousands of residential PV systems and compared their output to the theoretical paper maximum output if they were all properly aligned and operating. But if my neighborhood is any indication, they will have PV systems facing west, facing east, and bizarrely enough, facing south. They will even have ones built in the shade. There will also be lousy systems wired so that the whole lot operates at the performance of the worst panel. This is one of the reasons why giving substantial subsidies to residential installations while mostly ignoring commerical installations was not a very bright idea. Anyway, if you look at day 5 or 3 on their graph, that smooth line is the sort that results from a cloudless sunny day. The electricty produced at its peak is its real capacity. You ain’t gonna get more that that without stripping away the atmosphere or increasing the output of the sun. (Please don’t try this, neither worked out well for me.) Or ripping the systems off the roofs and installing them better. (This didn’t work out well for me either. I explained that I was helping them, but they still called the police.) So allowing for daylight savings, you will see that at 3:30 on a sunny day PV is operating at over 80% of real capacity and at 4:00 it is producing about 70% of real capacity.
So, to sum up, solar PV is well matched with peak demand in Australia.
Eh?
There would only be a daily savings offset problem if PV output was on eastern standard time, while the demand profile was on daylight savings time. But since both are on the same graph, using the same time scale, they are both offset, and there is no problem.
Quoting from the text:
“The estimated impact of solar on reducing network summer peak is reduced due to the system peak time differing from the solar peak time. The estimated output of the gross connected sample of small solar systems at the time of system peak on 3 February was 16.7MW or 32% of the total solar rated capacity of 51.6MW of this sample set.”
I take your point on installations not all being optimal. If you ignore what the rated capacity is, and just look at the highest output value in the graph as you suggest (doing this should make allowances for the fact that PV installations are not all optimal, though it will also allow a fudge for PV because it will leave out the impact of high temperatures on hot summer days reducing efficiency), the highest PV output in the chart at top of page 4 is 39 MW, and at peak time between the blue lines, it is between 25MW and 20MW. That is, between 51% and 64% of maximum hot sunny day output. And that is for the clear sunny days, and with PV installations spread out over many rooves. Looking at the brown line, which seems to have less favourable weather, the output across all these rooves at the peak time interval was between 20MW and 17MW. And for purposes of deferring the need for new infrastructure, its the worse case scenario that counts.
So, to sum up, solar PV is =somewhat= matched with peak demand if one assumes that you have a clear sunny day. PV is not “well matched”. I guess this is just semantics now. 🙂
As I said, I agree that the degree of match could give PV some economic advantage in that generation probably occurs at times when prices are high. But whether or not that match is good enough that it is now or ever will be economically sensible to use PV to try and offset peak demand for purposes of deferring network investment remains to be seen.
Hello Steve! Demand is on the same graph? Oh, I see! It’s on the previous graph, and yes, both graphs are in Eastern Standard Time. Earlier when you wrote that peak demand was 3-4pm in summer I assumed you meant daylight savings time and I kept that presumption when I looked at the graph on page 4. Sorry for the confusion. Also, I think the peak where you are is later than here, but I’m not sure as I’ve only looked at raw data and all those letters that are actually numbers hurt my eyes.
And I should appologise, rather than saying maximum capacity I should be saying something like maximum output to avoid confusion, because it could be technically correct to refer to maximum capacity as being much rather than its maximum output, even if that seems a bit weird to me.
And yes I think we have a semantics issue, I say well matched, you say somewhat matched, but neither of us have definded these terms.
But as for, ‘whether or not that match is good enough that it is now or ever will be economically sensible to use PV to try and offset peak demand for purposes of deferring network investment remains to be seen.’ I don’t get.
First of all, people don’t install PV to defer network invesstment, they do it to reduce grid electricity use and/or to sell it. Deferring network investment is just an added bonus. And there is no doubt that point of use solar can defer network investment .
Ooops! Somehow managed to accidently submit that last comment before I was finished. I hadn’t even edited it. Let me see… Nope, looks like my tourette’s didn’t slip through, thank FRACK ME! goodness.
Anyway, I was going to say that point of use PV can definitely help put off spending money on transmission infrastructure investment. And since the cost of point of use PV is paid for by people who aren’t the distributer, perhaps encouraging people to invest in it is a cheap way for a distributer to avoid paying for transmission improvements. On the other hand, they may not think it’s in their best interests. I just don’t know.
Anyway, we could keep going at this, but I’m getting pretty tired. I think a recess is called for.
watch through to the end – where he talks about fuel
pop