For those wondering about the significance of this announcement:
As several people have noted, what matters for solar PV isn't efficiency but cost per Watt. The maximum available energy is 1W/meter^2 at ground. Single-layer PV efficiency is on the order of about 40%. Mutliple-layer cells can reach a maximum of around 80%.
Even with existing efficiencies, the land space necessary to dedicate to solar power for all electrical energy needs is reasonably small. A percent or so of the Earth's surface. The hard part will be fabricating the PV and/or CSP (concentrated solar thermal power) plants to collect that energy, estimates run well over $100 trillion globally (Jacobson & Delucchi).
A key limiting factor in solar, wind, and other intermittent renewables is storage (or baseload / standby power). Assuming you'd want 7 days' total energy output on reserve, there's quite literally not enough lead in the world to build storage for just the US, let alone the rest of the world. Pumped hydro storage is very efficient, but sites are limited. Biomass similarly doesn't scale to present populations. Geothermal is good for 5-20% of power demands depending on locations (and some places such as Iceland might be able to export energy). Thorium reactors look like a plausible bet but require development. Liquid metal / molten salt batteries (such as Donald Sadoway's designs) look like they're both cheap and abundant enough to make the grade, though they're still under development as well.
Solar power does have its equivalent of Moore's Law: Swanson's Law. Solar PV costs fall by 20% with each doubling of capacity. It's held since the 1970s and looks likely to continue. Effectively, costs half about every 3 years.
http://www.economist.com/blogs/graphicdetail/2012/12/daily-c...
In short: this is mostly of significance for applications in which space and/or weight are at a premium: satellite or possibly solar-powered aircraft (ultralights or airships most likely). For ground-based generation, look for costs to come down further.
Not true at all. Your statement about available land is correct of course, but the important part of picture is that the soft costs for construction of solar electric power plants are already much higher than hard costs. And, improving efficiency is a great way to cut them.
Imagine a 10 MW power plant built out of panels with 10% efficiency. If you replace them with 20% efficient panels, you increase output 2x without measurably increasing soft costs - like land provision, fixtures on which the panels stand, installation work, insurance, etc. Only part that will increase will be inverters (not a particulary big item) and thicker cables connecting it to the grid. So, soft costs per watt will fall by 40-45%.
So, given that the wholesale price of solar panels now stand at 40 cent per watt, and even in cheapest countries the complete plant is $2 per watt, increasing efficiencies 2x means building a 2x more powerful plant for about $1.4 per watt (soft costs fall from $1.6 to $1.0 - i.e. they slightly increase but power output doubles) and hard costs stay the same. Big deal.
And almost all of the progress in solar power costs we can have now lies in this field - increase of panel efficiency, not decreasing their costs. Even if panels were free, costs won't fall much...
Of course this article bears no relation to that - these are high concentration cells, and cost to build collectors is already much higher than just buying enough of flat panels... better show me a non-concentrated cell with at least 35% efficiency.
There's a hard upper limit. 1 kW/meter^2 (mis-typed as 1W above). And you've got diminishing marginal returns of more efficient cells. The truth is that the land requirements are likely to go down by a factor of 2-4 maximum. Other cost factors (transmission, but especially storage) will dwarf these.
Once you've provisioned land for solar, the key costs are in replacing the panels every 20-40 years or so. Wind, stones, hail, and simple degredation will mandate this. Physical support infrastructure is likely more robust.
Land use for solar isn't dedicated-purpose for most applications. Even solar thermal can be used for grazing or other uses. PV can simply go on top of existing structures. You're not talking land acquisition so much as site acquisition.
Solar and wind are likely to be overprovisioned where possible. In the sense that you'll provide more capacity than is strictly needed to meet electrical demand. In part because you're not going to get 100% duty cycles ("capacity factor", which is how power installations are rated, are typically ~20 - 40%), and because you don't have an accelerator pedal, only a brake. Solar and wind aren't dispatchable, only sheddable. With overcapacity you've got the option of converting "excess" into other usable and storable forms of energy (hydrogen, methane, battery storage, electricity-to-fuels, etc.), or for intermittent but high-energy needs.
We've got cost reductions built in to PV production for the foreseable future. Again, efficiency improvements need to be considered in terms of total cost per Watt / kWh delivered*.
Correct, i agree to all these. I just meant that there are hardly many ways to decrease costs for large-scale solar available now except cell efficiency (not for U.S. where majority of costs are red tape and scarcity of installers, i mean countries where markets are established like Germany or Italy). Also, there is not much NEED to decrease costs below those achievable with efficiency increases (especially if efficiencies ca. 30% are achieved, which is possible like, 10 years down the road). A solar power plant with fully installed system cost of $1.5 per watt will be cheaper that high-voltage grid in majority of places, at $1 per watt in nearly every place.
>We've got cost reductions built in to PV production for the foreseable future.
In which way? Production capacity-related economy of scale? Current production capacity is already close (well, at least half of) what can be sustainably loaded worldwide. Maybe, another 2x growth is possible because factory builders don't care much if their business is sustainble long-term, they will work until worldwide demand is filled. But i will be very surprised to see over 300 GW/y production capacity worldwide anywhere in the coming 10 years. Apart from economy of scale, there is little way to reduce price.
Germans in their Kombikraftwerk study back in 2007, figured out that you need 5x the capacity (compared to the average usage) to cover entire annual (and daily) fluctuations of the grid with renewables, without storage (more exactly, with that little storage they already have - in the form of a few pumped hydro plants). I tend to still trust this study, there are no counter-arguments to speak of.
Yes, it included biomass and more importantly, biogas, which acted as flexible means of generation. That 5x capacity in fact, did not result in significant losses of power, it was in the range of a few percent as i remember.
More closer to the equator, less in higher lattitudes and/or where topography (valleys, canyons) or weather (fog, clouds) interfere, though even diffuse sunlight can provide significant power.
Regarding storage, I've read some interesting things about the potential of electric vehicles here. If every car were electric, that's a massive array of large efficient batteries connected to the grid. If utility companies charge varying amounts at different times, depending on supply, you could imagine a smart charger for your car whereby you buy electricity when it's cheap, store it in the battery, and sell it back for a profit when the price goes up (or just use the power in your home, reducing the amount you buy from the grid - the effect is the same). The utility company is effectively renting your electric car battery as short term storage.
There's some opportunity for this, and I've seen discussions of it. The capability is real and is being seriously considered, though with existing EV fleets the effects are too small to consider.
Given the variability of renewables supply, this is a good way to allow for surplus daytime supply (of solar) and possibly overnight supply of wind (though in many areas winds tend to peak during the afternoon/evening due to land heating effects).
The challenge though is that you're still ultimately limited by battery materials. Known lithium reserves would be exhausted within a century even with recycling (about 90% efficient) providing only a fraction of the world's population with a Tesla-sized battery. Other electrolytes, improved recycling, or sourcing lithium from much poorer sources (potentially seawater) might work around this, but it's still a constrained resource.
Solar power has something that has been proven to be an universial law for all manufacturing: The manufacturing cost decreases is a power function of cumulative production, also known as wright's law.
Moore's law is special because it relies on physical scaling (See Dennard Scaling) of the product. The transistors get smaller with each technology iteration, resulting in a physical correspondence to the economical law. Something like this does not exist for solar cells and most other products.
I've been very interested in finding out what lies behind Swanson's law. I suspect that chip fabrication technologies and methods have much to do with this, and to that extend there would be some carry-over from IC silicon fabs.
How conservative do you sound when you promote Thorium reactors in a solar cell thread? ..some people have heard enough "positive" things about nuclear power now. There are cheaper, more reliable, regrowing and more efficient technologies that Nuclear power fans simply ignore. Nobody said that the power generated by nuclear fusion is lower than with green power, but definitely at scale.
Gates has looked at a number of power options, including Sadoway's liquid metal batteries and the TerraPower "nuclear candle" breeder reactor.
I'm not convinced that nuclear's the way to go, but we know how to create working plants based on both uranium and plutonium fuel cycles, with thorium looking pretty viable. How economically feasible and long-term safe they are remains an open question, though I'd consider them as at least bridge technologies to whatever human's next stable-stage energy mix is.
The best fusion reactor design I've seen is a third-generation design that's been in long-term field trials with wide deployment, and can be found in an operational model 8 light minutes away. The primary challenge is figuring out how to plug it into human power grids.
First off, you're going to want to be getting away from coal by and by, for both availability reasons (turns out Peak Coal may well hit us sooner than expected) and for greenhouse gas (CO2) emissions. An alternative would be to have biomass plants available for weak-supply periods, and some solar plants (the solar thermal plant in Spain for example) use this method.
Second, solid-fuel plants don't ramp quickly. If you're keeping them in standby, you're burning a lot of fuel just to keep your boilers hot. Most peaking plants today are either hydroelectric (which can literally spin up in seconds) or natural gas (not quite as quick, but still capable of demand-matching in a few minutes). Natural gas is also subject to depletion and CO2 concerns.
For base-load power, nuclear and geothermal would be good options. Geothermal also doesn't ramp particularly quickly in most cases, though it's very reliable. Enhanced geothermal (ground holes dug into which water is injected) has proven to be much more expensive and accident prone, and less productive, than hoped.
I wonder if electrolysis and storage of Hydrogen would be a viable 'storage' method? Of course, the problem then might be the hazards associated with containing such a 'bomb'.
In practice it's pretty bad; Hydrogen, even compressed, takes up a large amount of volume. A 10 gallon tank stores about 1.5 gge of compressed H2.
The energy to compress H2 is again as much as it takes to create H2, and you don't get that energy back when you burn it (combustion perhaps 30% efficient).
An electric battery returns a far higher percentage of the power in, and is far simpler and safer.
H2's dangers are mitigated by its limited energy density. Most of the people on the Hindenburg survived.
I don't see H2 as a highly efficient storage option, but if the alternative is simply wasting the electricity generated, it's a choice worth considering. Compression or liquification will address some of the storage density issues, combustion is straightforward. If it's being used on-site or nearby then transport and handling are reasonably minor issues -- wider-scale distribution is a thorny problem.
In an oil-scarce world, hydrogen (or hydrogen-derived gaseous or liquid fuels) are probably the only real bet we've got for heavier-than-air aircraft fuels where passengers, significant freight, or military performance are required.
That's just it- the alternative is never wasting the electricity; you wouldn't invest thousands to millions of dollars in half a system. Well, I wouldn't.
Compression or liquefaction don't address the storage density issues. The horrible densities involved are _after_ you put the Hydrogen through those processes to their fullest possible physical limit. Uncompressed Hydrogen in a 10 gallon tank contains about 0.003 gge (enough energy to move an already-moving car just 500 feet).
Aircraft fuels are being addressed by biofuels including crop-based, algae-based, or char-based kerosene-like compounds. Natural gas-derived (steam reforming) and coal-derived (Fischer-Tropsch or Karrick) Jet A are already possible and much more scalable than oil-derived, just more expensive for now.
Hydrogen could never practically power a performance airplane (rocket is a different story) simply because you need big heavy tanks to safely carry it.
Well: don't discard unused what you can profitably exploit. That is: you get more utility from the storage than it costs you to get it. Net energy on storage will always be less than the input, but so long as it's either net positive or you get some highly useful form of energy out (food, liquid fuels, chemical feedstocks), it's worthwhile.
storage density issues I said "some". Compressed / liquified H2 is viable for some uses. Including flight. Remember, the alternative isn't existing fossil-fueled heavier-than-air craft, but airships and other "unconventional" fuels.
Aircraft fuels are being addressed by biofuels
If there were any level of success from these efforts I'd expect them to be touted to the stars. Pretty much every pilot project I've heard of (one big one in the US Midwest over the past year or so) has been exceptionally quiet/muted. The costs are going to be very high, and I'm expecting roughly $1000/bbl, translating likely to $50/gallon fuel. At 40 passenger miles to the gallon, a transcontinental (3000 mile) flight would run you $3750 in fuel charges alone.
Conventional freight rail "moves 1 ton of goods 100 miles on 1 gallon of gasoline". Assuming 180# per person, that's about 1100 miles per person per gallon, or 2.7 gallons for a transcontinental trip ($135 in fuel costs at $50/gallon). I'd expect that passenger rail achieves only a fraction of the efficiency of freight (lower packing densities, more stops, etc.). Turns out it's quite a bit less according to methodology applied to Amtrak. Roughly 55 passenger miles/gallon, a high of 80 pmg during WWII given higher utilization rates:
http://www.railway-technical.com/US-fuel-paper.shtml
This could likely be improved by reducing amenity cars (lounge, dining, observation). And it's frankly not much better than a personal automobile with 2 or more occupants.
However: trains offer one significant advantage over aircraft. They can be electrically powered. Which frees them from dependence on (increasingly rare and expensive) liquid fuels. With conventional (<80mph), "higher speed" (<125 mph), or "high speed" rail (150 - 220 mph), power consumption is around 50-95 kWh/passenger km (todo: convert to mpg equivalent), with loading factor (how many seats are filled) being a key determinant. At 350 kph, a non-stop transcontinental trip would be roughly 14 hours (adding in stops and dwell time would increase this, though if kept to a minimum, not by much). Hardly as convenient as the 5-6 hours presently attainable, but you'd have more space and amenities, as well as the option to embark and debark directly in city centers. An overnight service could be feasible: leave at 6pm, arrive at 5am (heading west) or 11 am (heading east). Stagger service a bit -- you could depart at 4pm for east-bound and 8pm for west-bound service to make arrivals more convenient.
If you've got sufficient excess energy, a supply of water, and the means to store it, it's a possibility.
It competes with alternatives such as compressed air storage, where you literally compress air and pump it into the ground, filling reservoirs from which natural gas was extracted. These rely on suitable geological structures, but it seems to be a real consideration.
For hydrogen, the main challenge is that you'd need to compress or liquify it for long-term storage. It's also possible to convert it to other fuels (electricity-to-fuel conversion) though that's complicated, fairly inefficient, and not something I've looked at in depth.
As several people have noted, what matters for solar PV isn't efficiency but cost per Watt. The maximum available energy is 1W/meter^2 at ground. Single-layer PV efficiency is on the order of about 40%. Mutliple-layer cells can reach a maximum of around 80%.
Even with existing efficiencies, the land space necessary to dedicate to solar power for all electrical energy needs is reasonably small. A percent or so of the Earth's surface. The hard part will be fabricating the PV and/or CSP (concentrated solar thermal power) plants to collect that energy, estimates run well over $100 trillion globally (Jacobson & Delucchi).
A key limiting factor in solar, wind, and other intermittent renewables is storage (or baseload / standby power). Assuming you'd want 7 days' total energy output on reserve, there's quite literally not enough lead in the world to build storage for just the US, let alone the rest of the world. Pumped hydro storage is very efficient, but sites are limited. Biomass similarly doesn't scale to present populations. Geothermal is good for 5-20% of power demands depending on locations (and some places such as Iceland might be able to export energy). Thorium reactors look like a plausible bet but require development. Liquid metal / molten salt batteries (such as Donald Sadoway's designs) look like they're both cheap and abundant enough to make the grade, though they're still under development as well.
Solar power does have its equivalent of Moore's Law: Swanson's Law. Solar PV costs fall by 20% with each doubling of capacity. It's held since the 1970s and looks likely to continue. Effectively, costs half about every 3 years. http://www.economist.com/blogs/graphicdetail/2012/12/daily-c...
In short: this is mostly of significance for applications in which space and/or weight are at a premium: satellite or possibly solar-powered aircraft (ultralights or airships most likely). For ground-based generation, look for costs to come down further.
And pray for highly effective storage solutions.