I think the issue is that OK, say we managed to get to 100% electricity being solar when the sun is shining.
You'd still have the time the sun is not shining, which would likely be more expensive than before (a gas powered plant would only be running half the time - effectively doubling its capital/construction cost per kWh).
So you'd definitely have an improvement on some levels but I'm not sure that would really help that much.
The real big breakthrough would be somme big improvement on storage. I'm not convinced this will happen quickly (at least not in anyway similar to the declining cost of PV panels). The consumer electronics industry has been paying $$$ for decades for better batteries/battery r&d and has seen pretty poor gains.
I think Tesla and the electric car manufacturers will definitely rapidly get the price down by say 30% because of economies of scale but will then hit a brick wall as more of the cost becomes raw materials, transport, etc which will set a floor on the cost of batteries.
Also, solar isn't the be all and end all of renewable energy generation. Wind, Solar, Hydro, and Geothermal all have different strengths and weaknesses, and flexibility of generation is important.
But above all, I think security of supply is probably the number 1 requirement (unless you're a big fan of load shedding - https://en.wikipedia.org/wiki/Rolling_blackout), and therefore, we'll still need energy sources that are reliable.
I predict a move away from coal towards natural gas. Sure it's not perfect, but it's not the worst either.
No idea why the hivemind is downvoting you, but you're absolutely correct.
A couple of additions and caveats.
Friend of mine at ORNL has been talking up compressed air energy storage (CAES). I'm somewhat dubious due to the Boyles law heating/cooling problem (gasses heat when compressed, cool when expanded, and the resulting heat flows affect both efficiency and equipment function -- gas turbines don't spin well when iced solid).
Pumped-hydro is the most efficient storage solution bar none, but is painfully restricted by siting opportunities. Being able to use oceans as a lower baisin might address this, though salt-water engineering is a significant concern (corrosion and other issues).
Interesting to see molten salt as at large scale that pencils out a viable for even, say, a two week total energy replacement solution for the US. You'd need tankage (insulated) roughly corresponding to current Oaklahoma oil transshipment storage facilities.
Electricity-to-fuel is another option, with Sabatier and Fischer-Tropsch cycles both proven. Carbon source from seawater appears somewhat promising, though my concern is that there's been 50 years of research without a large-scale demonstration project, making me suspect deeper issues.
I actually am a fan of load-shedding, and suspect that the concept of dispatchable load as opposed to supply may be part of the future way of thinking.
Coal => gas is a no-brainer, though also not a total solution, by a long shot.
Geothermal is highly underrated, especially if currently protected areas are opened for consideration. The Yellowstone caldera could possibly supply up to 15% of total US electrical demand.
> Carbon source from seawater appears somewhat promising, though my concern is that there's been 50 years of research without a large-scale demonstration project, making me suspect deeper issues.
I haven't seen anything about it recently, but the Navy was/is funding a demonstration plant in Hawaii. I really hope it works out as I'm skeptical that the developing world will shift to electric vehicles anytime soon.
This is what Danielle Fong at Lightsail has been doing since 2009. They've had investment from Bill Gates and Peter Thiel.
They've developed a way to compress and decompress air efficiently by heating/cooling the air. by using a carbon fibre air canister they are able to store air at a much higher pressure than previously possible.
Her Ted Talk[1] and their website[2] explains it much better than I do.
Compressed air storage rings of a scam to me. They never mention how efficient it is to compress the air and turn the air back into electricity. It's always how efficient their storage tank is, which on paper gives batteries a run for their money.
When sizing an industrial air system a rule of thumb is to budget 7-8hp of compressor for 1 hp of air motor. That is 12% efficiency, or only worth it if you had no other source of power. I'll give them the benefit of the doubt and assume a tightly integrated system you could do 3x better, but it still doesn't come close to batteries.
If someone has plug-plug numbers that are better, let me know.
There's some secret magic going on using moisture and phase change to drastically up the efficiency and storage capacity. It's not just a simple compressed air system which, as you noted, doesn't work. No idea if their current system will work or not but it's complicated enough that they've spent 7 years trying to get it right.
My understanding is that the grid-scale stuff will be using natural geological reservoirs -- basically re-filling old gas wells with air.
My understanding isn't particularly deep, and I'd like to run numbers on storage, volume, pressure, etc. But I suspect this'll have to be big enough that constructing cans really isn't viable.
The main problem in my mind is not where to store the compressed air, but the poor efficiency of compressing/using the air. Compressing air produces quite a bit of heat, and you have the opposite problem when using the air. For Thermal and other storage methods while the storage part might be more lossy, they are less lossy over all because they dont toss away 80% of the power before it can be stored.
If it was more efficient, than we would see air powered cars (not the scam that surfaces every other year).
Industry only uses it to power things because you can have simple & compact actuators and high rpm motors.
Realise that virtually all your energy storage options have hugely pressing cost, capacity, or storage stability problems.
Pumped hydro's remarkably efficient, fast-responding (minutes), but extremely limited in scale. See Tom "Do the Math" Murphy, but I think you'd need ~1,500 or was it ~15,000 Hoover-dam sized project for US storage capacity.
Batteries are fairly efficient, but respond slowly (you can neither charge nor discharge them rapidly), and at scale virtually all have massive substrate / materials shortages -- lead and lithium particularly. Iron-based batteries should be abundant, and liquid metal or molten-salt batteries seem to be the most abundant. Storage densities aren't great, but if you're building stationary facilities, that's not a concern. The 600C - 800C temperatures may be though. Having a neighbourhood melt-out wouldn't be pretty.
Biomass might work for standby thermal generation.
Thermal salt storage also pencils out. But any thermal storage system, that is, hot stuff you use to boil a working fluid that runs through a gas turbine, suffers from Carnot efficiency losses, about 35-45 max efficiency. If in a desert area, you've got problems of cooling your working fluid without venting too much of it (or the coolant). Not insoluble problems, but an issue.
Heat also doesn't store indefinitely though it should be good for hours to a few days.
Fuel synthesis has the advantage of scaling fairly arbitrarily large, particularly with liquid hydrocarbons. Put them in liquid-proof tanks and they'll stay there. Storage stability is proven to 100s of millions of years, so there's that. They're also transportable and can be utilised on-site. You lose 50% in hydrogen electrolysis, plus 65% on Carnot, for a net return of about 17%, but if you've sufficient peak surplus, that's viable.
CAES has the hot/cold problem, but there's a lot of air, and there's a lot of underground reservoir. Again I'm not sold that it pencils out, but it's possible.
Other options include direct banking of heat for buildings and/or industrial processes -- these use a lot of energy, and direct application and storage avoids electric or electric-to-fuel conversion losses.
Wind pioneer and former CTO of Siemens Wind Power is currently working on energy storage using rocks instead of a molten salt - he's blogging about it in the Danish engineering news site ing.dk.
Molten salt is efficient because of the phase change, but also much more difficult and expensive to handle than a big (well enormous) bunch of hot rocks. Last thing I heard, he's currently trying to get demonstration plant up and running - it sounded like they'd already done some experiments at Siemens before he left.
Anyway, nowhere near ready, but just to show that there are still low-tech options out there being examined.
Another low-tech option is biomass, either wood chips/pills or other stuff processed into methane.
Yeah, it's not as cheap as coal, but with good grid connections we need less storage than people seem to think, at least according to the research papers I've seen.
We had research show that you can offset storage with capacity to some degree. [0]
Some numbers: 100% renewable energy with a capacity of 340% would require 8% storage just for Germany, 3.8% for Europe (due to larger area which means more diverse weather). Also 8% for Europe using no solar and more wind instead.
The 340% capacity is needed to get to the 100% coverage since there is more downtime compared to old energy which had 180% in 2007.
If we go to 390% capacity (which corresponds to 170 GW additional production as calculated for Germany) we only need 0.9% storage.
Depending on the relative pricing of additional capacity and storage, the price for building the whole infrastructure can go down by half. (The upper limit given in numbers is of the same order of magnitude as Europe's GDP in 2009, 12·10^12 €)
Much better than water - higher energy capacity means smaller units and higher performing insulation making losses much lower.
Heat loss is a bit problem in stored water DHW scenarios and will get even more of a problem if we begin building houses properly (which surely has to happen at some point).
Batteries have some advantages that can offset the cost a little:
1) You can move them around, as in an electric car. That's useful if you want to do mobile stuff like driving. Or if you just flat-out want to move the facility somewhere it will be more useful.
2) They can be efficiently decentralized, which benefits reliability, and decreases transmission loss.
But anyway, the solution is to use any and all technologies, right? Batteries make sense some places, gravity storage elsewhere.
Only if your local generation plus battery system is equivalent or cheaper at providing power than the grid. Most battery systems aren't profitable even if power is free. So, no.
Batteries have a variety of uses on the grid. If you're clever enough to use them for several of these at the same time, it makes it easier to pay their way:
Similar to pumped water storage I wonder if we could do a household version with weight. Something like the gravity light (gravitylight.org) but on larger scale. I wonder if we could see a resurgence of chimneys on houses except now instead of letting smoke out they contain a XY ton weights that gets pushed up by excess solar capacity during the day, and then drops by evening powering the house.
I have no idea if that's realistic. Does someone know what the weight/distance to power output would be limited at...
A much better and denser option for storing energy mechanically is flywheels. I haven't researched what happened to this option since but when I was looking into it 15 years ago it seemed like a good option that needed more R&D into frictionless axles and vacuum chambers.
Excellent rapid response, second only to capacitors. But pretty poor densities, and hugely significant engineering challenges.
Flywheels that don't become fly-apart wheels is one problem.
Containment of fly-apart wheels another. Buried concrete pipes are usually what you're looking at. You need mass to contain these things.
The per-kg energy densities just aren't all that high. If you want reactive load to soak up very short-term demand / supply fluctuations, you can get that. And you've got crazy charge-discharge cycles.
Bearings are mostly solvable with magnets, as I understand. But you still lose a given percentage of storage over short time -- ~1% per hour or so, within a few powers of 2. Enough that long-term storage isn't viable.
And the thing that really screws you over is that the Earth moves. Geometric precession of your flywheel is something you've got to deal with.
There's a place, but I don't think it's large-scale, long-term grid storage.
You are referring to a hydraulic accumulator[0], such systems were built in the 19th century, though not for household use.
There is a modern effort to use the technology in a massively scaled up fashion by Heindl Energy[1]. Their concept uses pumped water to raise a rock weight 100 meters or more in diameter.
And considering this, a big question is will the market move away from centralized power systems. Will it be more viable to have a local/household level power generation and storage or will scale continue to give cost savings. This will likely have the biggest effect on storage/generation methods used. Possibly hybrid with distributed for suburb/rural and consolidated for urban/commercial? Or locally generated with grid peak power? Interesting times.
Batteries are the best bet for going off grid not for utilities based solar. Now that in more cities and states of US the utilities are getting net metering banned for home solar.
> The real big breakthrough would be somme big improvement on storage. I'm not convinced this will happen quickly (at least not in anyway similar to the declining cost of PV panels). The consumer electronics industry has been paying $$$ for decades for better batteries/battery r&d and has seen pretty poor gains.
Actually, it's not too bad, just slower. Batteries improve around 8% per year, if I remember right.
That's less than semiconductor based stuff improved when Moore's law held, but pretty impressive compared to lots of other technologies.
Li-ion 18650 cells held 2300mAh in 2005[1], and 3350mAh today[2]. That's an increase of 45% in just under 11 years. If capacity were really growing at 8% per year, then 18650 cells should have a capacity of 5300mAh by now.
Of course if the more solar we get combined with cheap computing a market will emerge where there are two prices of electricity. Car charging will probably be first where they turn on/off depending on the solar output. Refrigerators and AC could follow.
It's generally used in homes with 'storage heaters' which heat up overnight and release heat during the day while you're out at work. https://en.wikipedia.org/wiki/Storage_heater
I think we are more talking about hourly prices. You should take a look at the electric market, prices fluctuate heavy. So heavy even in some countries, that you are PAYING when you put electricity on the net: http://www.elia.be/nl/grid-data/balancing/onevenwichtsprijs
In areas where the utility is not set up to do this, you can programming it to monitor the grid and prefer charging when the grid is less carbon intensive.
Every time Solar and Wind and other renewables get mentioned - people get very confused over what is 'baseload', 'intermittency', why those terms are important and the whole "oh but the sun doesn't always shine and the wind doesn't always blow argument.
Lots of gas plants already run only a fraction of the time. This is because demand goes up and down on both a short and long term basis e.g. in many places the peak daily demand is just after lunchtime, and peak yearly demand is mid-summer, with an absolute peak at noon on one summer day. Without grid scale storage demand must be matched, hence ridiculously expensive gas peaker plants and transmission lines built for these peak loads.
It is in fact these very expensive gas plants that solar is destroying the market for first, both because they are the most expensive to run, but also because solar happens to align with the natural peaks in demand.
Electricity transmission is constrained by line loss, which is proportionate to amperage. To minimize it, voltage is raised to as much as over a million volts, keeping amperage down. This makes for very serious cross-country transmission lines, and electric companies still lose a quarter of the generated power to it. In my opinion, the two great strengths of solar are cleaner power and localizing power generating with its use.
Unless you user superconductors, like cooled aluminium (if I remember correctly). There is a lot of research in this area at the moment. If you cool a conductor low enough, the resistance reduces dramatically and you can transmit electricity with very little line loss.
The problem is that it costs lots of energy to cool things so it's difficult to end up ahead unless we make dramatic advances in high temperature superconductors.
So I guess the electricity companies also get most of their margins during daytime? Of that's the case, solar might screw up traditional electricity's business model much earlier, even without storage and feed-in laws.
We're talking about the grid, and there's plenty of demand when solar is not available -- nights, rain, snow, clouds, long winter nights, etc.
To be brief, I left it out, but my ballpark guesstimate is that, due to the cost of storage, for the main grid, solar for free is still not cheap enough. So, that is an answer to a question in the OP -- how cheap does solar have to be? My guesstimate is $0.00 per megawatt hour is still not cheap enough. In really simple terms, the grid doesn't want solar, even for free because of the need for storage and the fact that solar is unstable, e.g., due to just a sudden summer thunderstorm. The grid is super big on stability -- a small source of instability, and the whole grid of the US NE can go down, and at least once did.
Another, related point is that often the wholesale cost of power on the grid has been ballpark $0.005 per KWh, that is, half a penny per kilowatt hour. So, already, now, on the grid, intermittent power is nearly worthless, even when it is excess power from a rock solidly stable source.
And why might there be excess power? Because at the generators it's not so easy to adjust power levels quickly. So, when there's an excess, just sell it off where can, get half a cent for it, and go on.
Very much what the grid wants from the generators is rock solidly stable power, 24 x 7, no snap, crackle or pop, not even for two seconds, for years at a time. And we have that, now, that is, at least from the generators. Sure, for the lines and poles out to the burbs, during an ice storm, the reliability can be lower.
Solar? Fine, if it is cheap enough AND there is good storage to make it reliable enough AND the storage is not too expensive.
Again, the short answer, for solar, for the grid -- the storage costs too much.
Again, we're talking about the grid. There are other candidate uses for solar power -- taking salt out of water (get to store the clean water), pumping water uphill (if have a big dam handy), getting hydrogen from water (get to store the hydrogen or just pump it into a pipeline), making gasoline from coal and water (get to store the gasoline and pump it into a pipeline). So, these uses all have the feature that there is a good way to store the results of the solar power.
People have worked hard on storage for a long time, and that there is little or none installed on the grid indicates that so far no one has a good approach to storage.
Likely, get the solar panels with 100% efficiency for free, and the issue will remain -- cost of storage. A lot of this is just my opinion, but what's been deployed on the real grid makes me suspect I'm basically correct. We can be sure that lots of smart engineers have checked the figures very carefully, and so have the public utility commissions, so we don't really have to go over all the figures ourselves. It's pretty clear that the smart engineers that have done all the arithmetic carefully don't want solar for the grid.
But, sure, some people want to tax carbon, and tax it enough that solar with available storage will be cheap enough. That's another issue.
Installation has to get much cheaper. Installation is now more than the cost of the panels for most single family home installations. Home roofs are poor support surfaces.
Panels which are the roof have potential. The "solar shingle" vendors are making progress.[1]
I'm amazed that they aren't integrated much more.
Roof materials already have a cost. For example, one could create big roof tiles that are mostly solar panel. Edges have to overlap so it's a good idea to not have the panel extend there. One could lay them like other traditional flat panels, in an overlapping fashion.
Since the actual panel is so cheap, that shouldn't bring up the cost of the roof panel much.
The wiring can be on the underside and can be then connected after construction. (By some other team than roof constructors). After 30 years, they can be swapped. There might be some new technology then.
Another alternative would be roll-out plastic panels on ordinary roof materials. External wiring.
Everything should be laughably easy if you don't need to deal with snow and ice. They are a whole new design problem. To best limit CO2 emissions, the manufactured panels should be installed in places with best production ability, so freezing tends not to be among the first problems.
Storage is the /only/ way for solar to provide baseload power. Pumped water storage is vastly cheaper than batteries, and a better example of grid scale storage today. I should add that battery prices are coming down as volume increases (manufacturing learning curve), but not as fast as photovoltaic cells.
Elon Musk's goal with tesla is to boost battery production volume significantly to reduce the cost of batteries.
There's another large effect that is left out of this story. As solar gets cheaper, and as we get more of it, it reduces the marginal pressure on fossil fuel production. That, in turn, makes fossil fuels cheaper and forces solar to get cheaper still to compete.
Solar doesn't much compete with petroleum. Its main effect is to reduce prices for coal. You'd expect that this might start to affect the profitability of coal companies eventualy....
For solar to affect petroleum, whose primary use is transport, we'll need to solve the storage problem. Tesla notwithstanding that has not happened. Electric vehicle sales were 0.66% of unit auto sales in 2015, and actually represented a sharp numeric decrease from 2014.
(The dollar volume is higher given the higher price of electrics, but it's unit sales you want to watch.)
Once you've got electricity, FT appears to win. Though again, there's the ages of investigation without large-scale application, on a power-to-fuels basis.
Sasol, the South African energy company, did run commercial coal-to-liquids via Fischer-Tropsch, since the 1950s, and I believe may still do so. The US tried but ran into technical issues.
My biggest concern with solar power (which, by the way, may be based on outdated information) is that the production of photovoltaic cells produce more greenhouse gasses than will be spared in the cell's operational lifetime.
To ask an actual question: is this still the case? (Was it ever?)
I'd like to thoroughly debunk this myth with a more illustrative reference[1].
Over its entire lifecycle, utility-scale photovoltaic power creates 48g of CO2-equivalent emissions per kWh.
Natural gas emits 10x this; coal 17x.
Furthermore: the majority of PV emissions are dictated by manufacturing processes, which will probably get cleaner and more efficient over time.
The emissions of coal and gas are dictated by chemistry, and will never change.
This is directly tied to EROEI. If the EROEI of a cell is greater than 1X, it will produce more energy that it took to manufacture it. In that case it's net-negative -- over time it replaces fossil fuels in a net sense.
Lately I've read EROEI numbers for solar PV from 10-15X.
So no, this is not true, and likely has not been true for a long time. It might have been true back when PV was kind of a lab curiosity and niche item.
The interesting thing is the EROEI (energy returned on energy invested) for oil and gas has been falling for a century. I remember reading somewhere a claim that historical EROEI for crude oil.
There's an economics caveat to interpreting solar prices, which I think may have put a lot of people on the wrong track.
Suppose solar panels were priced such that, after accounting for installation costs and subsidies and everything else, solar was much cheaper than grid power and paid off quickly. Then pretty much everyone would want one, and the manufacturer would have a huge backorder. So the manufacturers wouldn't do that; instead, they'd price the panels a little higher, sell everything they could produce but not have the backorder, and invest the extra money into expanding their production capacity.
I think this is where we're currently at; solar power is in fact cheaper than grid power, it's just priced to support investment into expanding the manufacturing/installation capacity to properly take over.
> Suppose solar panels were priced such that, after accounting for installation costs and subsidies and everything else, solar was much cheaper than grid power and paid off quickly. Then pretty much everyone would want one, and the manufacturer would have a huge backorder. So the manufacturers wouldn't do that; instead, they'd price the panels a little higher, sell everything they could produce but not have the backorder, and invest the extra money into expanding their production capacity.
That's what finance is for. I assume if this were actually the case, wouldn't the manufacturers _take_ the backorders and separately raise money for expanding their production capacity? I don't buy it.
Isn't that the same with almost any kind of factory? If I was in the market for a car or computer, I wouldn't want to wait for a new factory to be build, either.
Is that anything special about the solar-panel industry?
If you can create a solar panel that pays off too quickly you could be better off selling the energy than selling the panels. You only need to start selling to the public when your competitors release enough solar panels to lower the grid price or you need cash. This is somewhat analogous to the situation with the manufacturers of hardware bitcoin miners.
It says a lot about the progress of solar if the big worry is that it won't provide 100% of all energy by itself.
Even cheaper solar would be nice but I'm not sure why it would be better than a radical battery breakthrough or some cheap and cheerful fusion thing or some mix of different solutions.
If you run the numbers pumped heat storage can likely do the job of time shifting electric power from daylight hours to night time.
The pricing structure will flip though, electricity at night costing probably 2-3 times peek daytime rates. One would expect industrial users would adjust and avoid using power at night[1]. That would reduce demand.
[1] Think of a mini-mill (steel) that currently runs its electric furnaces at night when rates are cheap. If rates are cheaper in the day they'll switch to daytime operation.
You are correct integrated mills use blast furnaces and thus can't stop. However Mini mills are secondary producers. They process scrap into finished steel. Since they use electric furnaces they can start and stop production.
A significant impediment is handling peak usage power. Maybe solar can provide most of our energy needs, but for those times where peak power is needed, it's probably more sensible to take a more balanced/mixed approach.
*edit looks like the article has a convenient link to another article talking about this exact problem:
People are comparing the wrong things when it comes to solar, and that leads to solar not showing how expensive it truly is.
For one, there is nowhere where solar is the baseload power, because it can't be, so it gets a bit of a "free rider" advantage. For another, solar plants depreciate like any other, but those costs aren't really factored in to a lot of solar power costs yet.
We'd need to build out a significant amount of energy storage capacity and change a lot of the grid as well in order to fully adopt solar as a baseload power source. And that would increase its cost by non-trivial factors. Would it still be worthwhile? Maybe?
This is a poorly researched article with many inaccuracies.
(1) Utility Scale Solar is already less <$1/W installed in India, and heading for sub $1.5/W in US.
(2) The price of Solar PV panels is already at $0.40/W. US-based $FSLR is has a roadmap to get to $0.25/W by 2019. In addition PV efficiency is increasing by 10% yoy. This is just from purely riding the 'industrial learning curve'. See [1].
(3) "Value deflation" is a policy issue that has a simple policy solution. As a tech that produces an intermittent product, but has high fixed-costs but zero-marginal costs - solar (like wind) should be financed (and paid for) via a fixed tariff (feed-in tariff or FiT). See [2]. This is how Solar is financed in the rest of the world outside the US. If 'value deflation actually became an issue - then my guess is that regulators in the US would step in (but one can never say with US regulators who tend to get captured by various lobby groups).
(4) Solar will account for 30% of all new capacity power additions going forward globally. This is happening - now. There is over 100,000MW installed globally already.
In addition - every time solar or wind comes up for discussion on HN or elsewhere, the same misconceptions and confusions about baseload, intermittency and costs arise.
To summarise the counter-points again:
(1) Renewables does not need to be base-load or compared to 'base-load'. 'Base-load' is spectrum not a point. See [3]
(2) There is a difference between intermittent and 'unplanned'. Planned vs unplanned is the main issue. Even nuclear has unplanned shut-downs - no tech has a 100% 'capacity factory' running 24/7 365 days. see [4]
(3) Renewables can get to 60-80% penetration via:
(a) increasing efficiencies (happening now)
(b) increasing energy storage efficiencies with declining prices (happening now)
I think the biggest impediment to widescale solar adoption is legeslative.
If you follow hackernews, you'll regularly see articles about places like Florida (and possibly Nevada if memory serves) where solar could easily power homes, but disingenuous legislative instruments and manipulativly worded ballot initiatives are housed to effectively block solar adoption.
>> 25 cents per watt by 2050 — down from around $3 per watt today
Can I trust a report that does not even have the units right?! Price should be proportional to energy (i.e., Joules or Watt-seconds) not power (Watts).
Huh? What's wrong with measuring in price/watt? Price/watt is actually the standard for comparing electricity generation due to not having to create arbitrary units of time to compare with
You're mistaken. Fuel is sold by price/energy, effectively, but generating capacity is sold by price/power. Since in the case of solar PV, the "fuel" is free, the only cost worth mentioning is the capacity cost.
Installed capacity is normally measured in watts. It's really only valuable for trending within the same technology, though, unless you include the capacity factor.
You'd still have the time the sun is not shining, which would likely be more expensive than before (a gas powered plant would only be running half the time - effectively doubling its capital/construction cost per kWh).
So you'd definitely have an improvement on some levels but I'm not sure that would really help that much.
The real big breakthrough would be somme big improvement on storage. I'm not convinced this will happen quickly (at least not in anyway similar to the declining cost of PV panels). The consumer electronics industry has been paying $$$ for decades for better batteries/battery r&d and has seen pretty poor gains.
I think Tesla and the electric car manufacturers will definitely rapidly get the price down by say 30% because of economies of scale but will then hit a brick wall as more of the cost becomes raw materials, transport, etc which will set a floor on the cost of batteries.
Happy to be proved wrong though :)