Monday, June 30, 2014

Californian electricity from solar more than doubles


So in January 2013 (mid winter in the northern hemisphere) it was 1000 mW.  By January 2014 it peaked at 2500 mW (notice virtually no fall in production in the northern hemisphere winter) By May, it wasnearly 3 times as much as May 2013.

All the same, as the article where I found this striking graphic shows, for the US as a whole, CO2 emissions increased.  Which is because, even though California is the world's 7th largest economy all by itself, the US as a whole is much larger, but it had a much lower penetration rate than Cal.  But that state has lead the rest of the US for decades.  What has happened there will happen across the sunbelt, and eventually, as solar costs drop, everywhere.

More on the Vanderbilt super capacitor

I mentioned the supercapacitor, a new kind of electricity storage device, orders of magnitude faster to charge and orders of magnitude larger storage capacity than batteries in this post.   The team who discovered it has done more work on it.

Researchers at Vanderbilt University are developing a new generation of supercapacitors that can function even when they are subject to weight and vibration stress. Translation: the drywall of the future will store enough electrical energy to power your home electronics and appliances.


The new supercapacitor report from Vanderbilt was published in the journal Nano Letters on May 19. The team subjected its silicon supercapacitor to stress tests replicating vibrational accelerations of more than 80 g, which is more than you’d get if you were a turbine blade in a jet engine. They also went up to 44 psi for stress/pressure.
In both cases, the team found that the supercapacitor operated “flawlessly” in terms of charging and discharging, while maintaining its storage capacity.

Read more here

Old fashioned capacitor




supercapacitor

Sunday, June 29, 2014

Another Abbottism

Via



Carbon Tax Works

And without affecting growth or employment or .... well, anything, except emissions.

And, oddly, the carbon tax was introduced by a right-wing government and opposed by the left.  Politicians.

The full story in the Mother Jones article, here.

And I repeat: no impact on economic growth, just as there hasn't been in Oz, where our esteemed leader, The Cane Toad, repeatedly and ad nauseam stated that the carbon tax would lead to economic collapse.  And was wrong.




Saturday, June 28, 2014

Earth will cross the climate danger threshold by 2026

I won't repeat the article from Scientific American; the author (Michael E Mann) says it better than I can.  You can read it here.  A key discussion in the article is how much global temperatures will rise if atmospheric CO2 doubles from the 280 ppm (parts per million) before industrialisation began to 560 ppm.  His estimate: 3 degrees centigrade.

The first chart below from the article shows different estimates of how much the world will warm based on different lines of evidence.

The second chart shows how temperatures will rise depending on just how sensitive the world's climate is to rising CO2.  In the article, the author points out that reducing aerosols (emitted along with CO2 by burning coal ) will cause global temps to rise.  So ironically, even as China slashes its emissions of CO2 global temps will rise/




Wednesday, June 25, 2014

Melbourne floods

Not caused by rain but by a high tide and wind.  And the inexorable rise in the sea level.  Nine inches since 1960.  And now, with the Antarctic and Greenland glaciers moving 10 times as fast as they used to just 20 years ago, thus over time accelerating the sea level rise, it is now expected that by 2100 the sea level will have risen by 2 metres.  That's just 85 years away.  My children will see half of that.  Flooding in Melbourne will happen more and more often.  As it will in other world cities close to sea level.  And the cost of protecting them will be prodigious, far, far more than the cost of switching to a carbon-free future.







Tuesday, June 24, 2014

US Recovery strengthens

May and June data look good.

Preliminary PMI up, as were both the Philly Fed and the Empire State surveys


Warmest May ever

Well, ever recorded anyway.

It's worth repeating.  THE HOTTEST MAY EVER RECORDED.

(data and chart from NOAA)

But of course, climate change is crap.





Friday, June 20, 2014

Goodbye, Miami



It's common for those who don't really understand climate change to say "oh well, I'm sure they'll think of something to sort things out."  Well, maybe they won't.  Read this fascinating piece on the difficulties Miami is already facing from rising sea levels.  Read past the first couple of paras, which are speculative though entertaining, and move on to the detailed discussion of the problems on page two and onwards.  The really depressing thing is that Florida's governor and elite are climate change deniers.  Despite the evidence all round them.  The 'she'll be right mentality'.  But she won't.

Cretinism.




Germany produces 50% of its energy via solar

Yeah, it's summer, and the days are long, but WOW!

Read more here. As the article says, more storage is now essential.

If Germany can do it, surely countries with more sunshine, like Australia and the US could do even better.

Thursday, June 19, 2014

Biggest fall in Ozzie greenhouse gas emissions in 24 years

Alas, just in Australia.  And only 0.8% in total.  Still, better than nothing.  But electricity related carbon emissions fell 5%.  Clearly, the Carbon Tax is working.  And equally clearly, it's not enough (petrol and diesel for example are excluded)  Equally clearly, the economic catastrophe The Cane Toad (our rabid right prime minister, Tony Abbott) forecast hasn't happened.

Australia posted its biggest annual reduction in greenhouse gas emissions in 24 years of records in 2013 as the carbon tax helped drive a large drop in pollution from the electricity sector.
The latest greenhouse gas inventory, released online without fanfare by the federal government, showed annual emissions excluding changes in land use were estimated at 538.4 million tonnes of carbon-dioxide equivalent in 2013, down 0.8 per cent on the previous year.


Read more here.

Emissions need to fall GLOBALLY by 2.5% per annum.  This would lead to a fall on 40% over 20 years, still too slow, but a huge improvement on the current trends.


Wednesday, June 18, 2014

Lifters and leaners



An excellent article on the latest Ozzie budget and the steep increase in inequality it will cause, from Melbourne's The Age.

During the First World War, Australian soldiers in London were abused by the officer class and the English as "verandah-post leaners". Cartoons suggest they were commonly found adopting that comfortable posture. Not only did the criticism from "above" fail to stop them leaning against convenient posts, they responded by leaning even more laconically. They weren’t leaning because they were lazy; they were leaning because, on leave from the Western Front, they had earned the right to lean. Leaning was a pointed demonstration to the English of colonial egalitarianism. As Australians, leaning was their right.

In his recent speech to the Sydney Institute, Treasurer Joe Hockey summarised the government’s philosophical position on equality as "for equality of opportunity rather than equality of outcome" (The Age June 13, 2014). He takes it as self-evident that it is "not the job of government to manufacture the outcome from public policy in such a way as to ensure that every person is an equal beneficiary ..." In saying this he is not only drawing on one of the most persistent criticisms of equality as a political ideal - that it is impossible to implement in practice - he is going much further: he is explicitly repudiating equality as a political ideal.

But, since it is not politically acceptable to repudiate the cherished and widely held belief that Australians are all equal, it is necessary to pay lip service to the idea, even while emptying it of content. "Equality of opportunity" is a well-tried cover. It is the version of equality you claim to believe in when you do not believe in equality at all. Indeed, some in the Liberal Party are now coming close to embracing the extreme neo-liberal position that it is actually inequalitythat is desirable, because it releases individual initiative and is economically more productive. That is a very difficult argument to sell in a country that boasts of its egalitarianism.

The big problem for Hockey and the Liberals is that the debate on equality has shifted dramatically. Since the Occupy movement popularised the divide between the 1 per cent and the 99 per cent, and the high-fliers shook off the GFC without penalty or shame, now followed by the extraordinary success of Thomas Piketty’s Capital in the 21st Century, the discourse has moved onto different ground. The public issue is no longer the problematic ideal of equality but rather the relentless promotion of inequality.

Conservatives were much more comfortable with debating equality because of its historical associations with socialism, as even without recourse to philosophical argument, they could appeal to its seeming practical impossibility in real terms. But now people aren’t talking about equality, they are all talking about inequality. That is a debate in which the Right finds itself very exposed.

In Australia, where the meaning and extent of egalitarianism may be disputed, there is still a very strong attachment to the idea that we are, as a people, in some way equal. It is politically necessary for the neo-liberals to claim that, despite everything they say and do that might suggest otherwise, they really still do believe in equality. That is why "equality of opportunity" is talked up. It is, to be blunt, a con.
The problem with equality of opportunity is that it appears to be completely compatible with unlimited material inequality. Indeed, it is promoted as such. The "starting line" metaphor suggests that life is simply a race and that it is a fair race if everyone starts from the same line. But we all know people don’t start from the same place financially, educationally, in terms of health, or culturally. The only way we might get people even near such a starting line is by redistribution of wealth, but redistribution on a sufficient scale is labelled by Hockey as "unfair" to those who have accumulated it.

When the debate shifts from equality to inequality, the role of intuitive popular understanding changes sides: this time it is on the side of those who believe that the degree of inequality is both unfair and increasing. This appears to be not only the view of the majority of people in Australia, but of the majority of people in the world.

The history of welfare in Australia has always been a changeable mix of private and public provision, but the recent enthusiasm by neo-liberal governments for a greater reliance on charity (and personal responsibility) is a remarkable turn back to the darkest days of the 19th century and the "deserving" and "undeserving" poor. Charity was then a creator and marker of class division: the "givers" were morally superior and the "takers" were morally inferior. Conservatives thought it instrumentally useful that the takers of charity should feel shame. Apparently they still do.

When the sales force of the federal government employs the terms "lifters" and "leaners" it is drawing on just this type of retrograde 19th-century imagery. It is not surprising they are finding a budget based on such social divisiveness hard to sell. Australians generally regard themselves  as lifters, and very capable ones. But, like the Diggers in London, we also believe, that after we have fought hard, or been injured, or are just plain tired from a lifetime of lifting, we have the right to lean.
Dr Bill Garner is a Research Associate at the School of Social and Political Sciences at the University of Melbourne.


Read more here

Sunday, June 15, 2014

Climate change is crap

Our esteemed PM, the Cane Toad, is on record as saying that "climate change is crap".

I was trying to work out why the Right is so hostile to the very concept of climate change.  But before I get there, I think it's worth summing up how I, a non-scientist but a reasonably intelligent thinker, see things.  Let me sum it up.

1) We have known that the world is much warmer than it should be since Fourier (1824).  He stated that the world was warmer than it would be in a vacuum.  It was left to later scientists to work out why.  By the way, that's nearly 200 years ago.  Global warming is not some recently concocted unhinged communist plot.

2) Arrhenius, in 1896 forecast global warming would occur as the amount of CO2 rose in the atmosphere as by then the "blanketing effect" of CO2 and the physics of light/EM spectrum refraction/dispersal were clearly understood.  He forecast that a doubling of CO2 would lead to a 5-6 C increase in global temperature, only he thought it would take thousands of years.

3) Since his time, the measurement of atmospheric CO2 has improved greatly.  It is a matter of scientific measurement that the amount of CO2 in the atmosphere has risen steadily since the industrial age began. Recently the concentration of atmospheric CO2 passed the 400 ppm mark, the highest it's been for hundreds of thousands of years.

4) Although we are not sure how much warming will result from a doubling of atmospheric CO2 we are sure it will warm.  The earliest models in the 70s suggested 2 degrees C, not quite as alarming as Arrhenius' calculation but still bad enough.  In 1979 the US NRC estimated somewhere between 2 and 3.5 C rise.  The models since then have provided different answers, pretty much between those extremes, with a bias towards the lower end, depending on their estimation of the impacts of aerosols (which reduce warming by reflecting incoming infra red radiation back into space) and other global warming gases like CFCs which are far more potent than CO2 but are also far less abundant.   But all the answers suggest that temps will rise, the only debate is by how much.

5) And in fact --- surprise! --- it is a fact of scientific measurement that global temperatures have  risen since the 1850s.  It is a fact, etc, that glaciers have retreated, that the Arctic ice cover has retreated, that the Greenland and Antarctic ice caps are melting, the sea level has risen, and recent analysis suggest that this process has accelerated.

How simple is that?  Even Tony Abbott could understand that.

You can read an excellent summary of the steadily increasing understanding of our climate and of climate change here.   What is abundantly clear is that we have gone step by step from ignorance through to deeper insight, and at each stage of the way, since this was science not religion, at each stage, there were doubts and alternative theories,  and new evidence changed scientists' minds.

Here is a record of forecasts made and results subsequently confirmed.

The chart below is a simplified version of the chart from this post, and I've fitted a moving average to smooth out the data spikes.

Source.  Smoothed by me, using 13 term Henderson curve


There is now an overwhelming consensus among climate scientists that global warming exists and is anthropogenic, i.e., caused by mankind.

So why is the Right so dead against this consensus?  The reason these nongs persist with their piffle is that for them it has become part of the culture war.  The Left "believes in" global warming, it advocates collective (i.e., "socialist" action, how we laughed) so therefore it is to be vigorously opposed by the Right, not because of logic, not because they are correct, but just because.  Not that the cheques from "think tanks" funded by demented plutocrats and coalminers hurt.   Our own prime minister, Cane Toad Tony, is of that ilk, still fighting the adolescent battles of uni now he is in power.  What a tool.

The good news to set against this shameful, dishonest and damaging campaign run by the global warming denialists  is that the ever declining prices of solar power (both PV and CSP); the precipitous fall in battery costs, and the slower but inexorable decline in wind power costs will make it -- has already made it in some places -- cheaper to switch to renewables than to continue with coal.  Moreover, the world's largest emitter (China) has taken a high-level commitment to reduce the energy intensity of GDP dramatically and will cap and then cut CO2 emissions.  Their suddenly found moral fervour is greatly helped by the fact that renewables are now close to grid parity.

It will be very hard for the unhinged Right to stand in the way of market forces though no doubt they will try.

Peaking Duck

No, it's not a spelling mistake.  It's the jokey name given to the chart below, which shows how as solar PV power cells are installed, midday demand will fall away making the evening (the "head" of the "duck") the new peak period.  (see the article here)


This is scary stuff for conventional monopolistic electricity utilities.  Old-fashioned power stations (coal or nuclear) have to run all the time to provide baseload power.  But if demand is collapsing in the middle of the day, the time when because of aircon units, it used to peak, not only must the cost of the power stations be spread over lower sales thus raising costs per kWh, but also this previously most profitable period in the day is now the least profitable (because deregulated/traded power prices are at their lowest)

The principal solution to the technical problem is obvious: storage.  Six hours of solar power needs to be stored (on site prolly) to be released in the evening.  That solves the technical issue, but it doesn't solve the utilities' economic issue, which is that distributed power means utility sales will decline.

Yet there are innovative and inventive ways round this.  The utilities themselves could install CSP solar towers, which store the energy from the sun's heat and light at its maxima to release when needed later.  Naturally, since it is for a peak period supply, they would charge peak period rates.  Or the utilities could sell solar plus batteries to households and business, with the condition that the batteries are connected to the grid in such a way that their stored power can be called on by the gird at peak periods.  The economic gains could be shared between the grid owner and the consumer.  The utilities could even make money from financing their customers' solar, wind and batteries.  Instead of providing power 24/7, they would provide (at a fee) the right to power at peak periods and the peak power itself (at a premium).  The article itself has several other suggestions.

But the economic problems for utilities surely aren't going to go away by themselves.  And their problems will become inexorably worse as renewable power costs drop.

Thursday, June 12, 2014

Solar Towers

Solar panels (photovoltaic cells) are not the only way to convert sunshine to electricity.

This article talks about the largest concentrated solar power (CSP) project in the world.  In essence, it consists of heliostatic mirrors which "follow the sun" (like sunflowers), reflecting the heat and light to a central focus.  At that central point, the heat is intense enough to melt salt, which is then used to produce steam which runs a turbine generator.  The key advantage of this is that the heat can be stored and released later, when there is no sunlight.   Another advantage is the CSP uses the whole spectrum of sunlight, i.e., including heat (infra-red) whereas PV cells (solar panels) just uses visible light.

The chart below shows how this would work.  The blue line represents a PV cell.  Note how it rises smoothly towards its maximum (a quartic by the looks of it, I thought it would be like a normal distribution!):  the spikes from 10 o'clock onwards are due to clouds.  The green line shows the concentrated solar power output when it releases its electricity over 8 hours into the grid, starting at midday.  The yellow line is the same thing over 16 hours.

This technique enables solar to be used as baseload power.  In effect, in places where the sun shine strongly and a lot, houses/shops/factories would have their own solar panels for daytime use and would use CSP for the evening and the night. No need for gas or coal or nuclear.  As the article mentions, there are some places where CSP is already producing power, without subsidies, at 13.5 cents per kWh (the average retail electricity price in the US is about 12.3 cents, in Australia it's about 28 cents).  For Australia, Spain, SW USA, southern China, India, etc, this alternative form of solar is likely to very soon make not just new coal plants but also existing coal plants too expensive.

































Tuesday, June 10, 2014

Electric motor bike

Somehow I just didn't believe it was possible to create an electric motor bike which could compete with petrol-driven bikes.  And I was wrong.


Monday, June 9, 2014

Assault and battery





Obviously electricity storage is critical to moving away from fossil fuels and thus to slowing and eventually reversing global warming.  Even though the cost of solar and wind power are falling fast, the sun doesn't shine at night, and is lower in the sky with a shorter day in winter than in summer, and the wind is variable.  So we need to be able to store power when it's made to use later when it's needed.

Well, the good news is that battery costs are plummeting.  For  example, over 15 years, the cost of a laptop battery has fallen from $2000 to $250, a compound rate of decline of 13% per annum.  If that trend continues, then they will halve again over the next five years.  But will it continue?  The pessimists say no (they always say no)

The likelihood, actually, is that new battery technologies will accelerate that decline, if only because as solar power becomes widespread and the need for storage builds, so will it become immensely profitable to find solutions to the storage problem.

Here are two:.


  • A new lithium-ion battery that is -- wait for it -- 2000 times as powerful and recharges 1000 times faster than existing lithium-ion batteries.  (The lower chart in this article requires a bit of explaining.  As far as I can make out, the coloured blobs represent different iterations/models of the new battery; the stars with 'A123' and 'Sony CR1620' represent existing batteries, as I assume do the squares with 'MB1', 'MB2' and 'MB3' next to them)
  • A completely new storage technique using silicon and graphene, with a similar technique to the new lithium-ion battery above, namely giving the surface of the storage material (in this case silicon) a nanosurface which multiplies its effective surface area 100s of times.  Once again, orders of magnitude (i.e, 10 or 100 times) faster recharge and energy density.


Still experimental.  But would you bet that something like either or both of them won't be in production within 5 years?

Meanwhile, Tesla is constructing a giga factory which will cut the costs of EV (electric vehicle) batteries (existing technology) by 30 to 50%.   Elon Musk (first PayPal, now Tesla, soon the world?) is confident every garage will have an EV within 6 years.  Prolly one of his.  One clever idea: using EV's to provide peak energy to buildings, for example.  All the EV's would be plugged in to the building's grid , recharging when power demand is low, but releasing power to the building when demand peaks.

When I got my first laptop, paid for by my work, it cost $12,000 (in 1992 money! -- double that to get an estimate in today's money).  These days you can buy a much more powerful one with quadruple the electricity storage for $400 or $500.  Then, I was the only commuter on the train using a laptop.  Quite literally, the only one.  For several years.  Now everybody has them -- or their equivalent: smartphones and tablets.  Some ppl have all three.

Coal is in trouble.  For now, oil is OK, but very soon (3 years?) electric cars and lorries will start to seriously compete with petrol and diesel vehicles.  Gas is still OK for now, because it emits half the CO2 of coal for the same power output.  But how much longer will it last, as PV cell and battery costs plummet and their efficiency improves?

As it becomes more and more compelling and urgent to cut greenhouse gas emissions, so the cost of doing so is precipitously declining.

I wouldn't buy a coal share for any money.

Yesterday, today and tomorrow

The three charts below look at solar power in the past, now, and in the future.

See full article at CleanTechnica

The Past:

Solar was more expensive than other forms of energy and only survived with subsidy.



The Present:

Solar now costs the same as other forms of electricity.


The Future:

Solar will get inexorably cheaper than alternatives.


The chart below shows the levelized cost of electricity from solar.



As the cost of solar falls, so the amount installed will rise --- exponentially. Interesting that the forecasts in the Wikipedia article by the US Department of Energy of a LEC of PV solar of 13 c per Kw by 2019 look very conservative.  The LEC by the end of 2015 for solar PV should be on my forecasts about 15 cents,  only a little above the average US electricity price of  12.3 cents.

Climate change: the AHA! moment

Source: http://www.metoffice.gov.uk/hadobs/hadcrut3/diagnostics/comparison.html
When ppl first started talking seriously  about the risks of globule warming in the 70s (Arrhenius produced a prescient analysis of the risks in the late 1800s!) , the cost of doing something to stop it seemed prohibitive.  Alternatives to coal and oil were extremely expensive.  Moreover, poor countries just starting out on their massive eco development were dirt poor; naturally their focus was on development not clean air.  But the cost of solar and wind power fell steadily, as did the cost of batteries: solar by 18% per annum for most of the last 40 years, wind by about half that, batteries by 13% per year (in 15 years, the cost of a laptop battery has gone from US$2000 to US$250).  And China, India, Brazil etc got richer and things like clean air and water became more important to them. 

At the same time, all the cheap sources of oil have been found and extracted.  All new oil supplies are harder to extract and more expensive.  That's true of coal too, the big discoveries in Oz are pricey to produce because of all the new infrastructure required,  So the cost curve of renewables is falling steadily and inexorably, while electricity generated from fossil fuels is getting more expensive.  Meanwhile, the evidence of global warming is becoming ever stronger.  Recently, for example,  there has been new analysis showing that the glacial melt in Antarctica and Greenland is much faster than had been thought and it is now clear that the forecasts of sea level rise made just a few years ago are far too conservative.  

So we've reached an AHA! moment. 

  1. Renewables are on the cusp of becoming cheaper than fossil fuels and are getting cheaper every year.  Why resist that (unless you are a coal miner or oiler or are otherwise part of the fossil fuel economy)?  It will be interesting to see how the right squirms now it is market forces leading to creative destruction of their fave industries.
  2. China, the world's largest emitter of CO2 is taking steps to cut emissions radically, not just because climate change is creating immense problems for them, but also because coal is filthy, and the air over China is lethal.  The top six emitters (China, United States, India, Russia, Japan and Germany) produce nearly 2/3 of global energy-related CO2 emissions (data for 2009; China is surely even bigger now).  The top three over 45%.  Modi, the new PM of India, "wants to see solar panels on every rooftop" (India has more sun in winter than summer because of the monsoon), China wants to cut energy intensity by 50% over (I think, couldn't find the reference) 6 years, the US will cut emissions by 30%   If the top 3 agree, and start concerted action, (a) emissions will start to fall, and (b) everybody else will be obliged to follow.
  3. Forest burning (mostly Brazil, Indonesia, Borneo and Oz) contributes 15% of global emissions (i.e., not energy related).  A man-to-man chat with these guys, armed with a cricket bat, will no doubt see dramatic reforms.  
  4. Global warming is obvious -- and terrifying.  We need to start acting NOW.  Fortunately, thanks to technological advance, the transition costs will be low.

My grandchildren won't drive petrol-driven cars, or use coal-fired electricity.  The VERY BAD NEWS:  Even if atmospheric CO2 peaks NOW, global temps will keep on rising, droughts and floods will worsen, and the sea level will go on rising.  And of course, it WON'T peak now.  Soon, I'm sure.  Soon enough, I hope.

Three years ago I installed 1.5 kW PV panels on our roof, which halved my electricity bill.  If I were to install 5 kW, now, it would cost at A$5000, just twice as much as 1.5 kW then, a compound rate of decline of about 16% per annum.  At the wholesale/feed in tariff of 8c per kWh, at this latitude, $5000  solar panels would be cover their cost in 9 years, after which I would get electricity for free for the next 16 years (panels last 25 years)  At the retail cost (28c per kWh) costs would be covered within 3 years.  But if costs keep on falling like this, should I wait another year?  Another two? Until the  $5000 is down to $4000?  Or $3000?   But the lure of negligible electricity bills as well as doing my bit to save the world .....  

Of course, I also need to put in storage.  The sun doesn't shine at night.  Can't get costings for that yet (there's this and this, though) but for a total system of 6.5 kW, my guess for storage costs for a couple of hours of power is A$1500-A$2000.  Without even getting started on Wind power, with a new Ozzie turbine design

I saw a Nissan Leaf yesterday for the first time, in the lane next to us at the robot while we were waiting to get onto the freeway.  They're still expensive in Oz (A$40,000, but down from $55,000 two years ago) because there are no subsidies, but with battery costs falling as they are, it will be no more expensive than petrol driven cars within just a few years.  And as my lady said  "Imagine never having to buy petrol again!"  But electric cars also require far less maintenance than petrol-driven cars(though batteries must be replaced eventually) and are cheaper to run.  "Imagine never paying for electricity again".  These are as potent motivators for change as saving the planet.

It's all happening. 

Sunday, June 8, 2014

Wind Turbine Prices

A more or less continuous slide over the last 30 years.  My calcs give me a 5% per annum compound decline in cost, not the 14% shown on the chart, although that is not against time  but against (I assume) installed capacity (hence the note below the chart of 'learning rate').

This is not as fast as the fall in PV cell costs (+-18% per annum) but still means that costs have fallen 75% in 28 years.

Via ThinkProgress