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December 26, 2007



It's great if you get the land for free - on your roof, on a landfill, in the desert. But with ~8-10% efficiency for CIGS panels, the cost will start to rise once land gets scarce - which will probably take a long long time. I hope this will catch up.


Did you know that "coal is the most abundant fossil resource (and) the total amount of energy produced by burning all the coal on the planet, including all yet to be mined, would only be equivalent to the solar energy that strikes the Earth every six days." And, did you know that if we quit using coal for generating electricity the GHG problem would be completely, yes! completely! solved?

So you ask: How do we do that? The answer: by mass producing solar cells, gathering the electricity they produce and storing it in the form of spinning flywheels, hot water, charged batteries, chemical heat, etc.

Low-cost, mass-produced, thin film solar panels appear to be the first of the major breakthroughs we need to clean up our planet. Can you imagine a world where oil is used mostly for greasing bearings for BEVs and won't be worth fighting a war over?
If this company can ram up production and will license their patents to other mass-production companies, we could begin to see major changes in how we generate power; within a short period of time nuclear, oil, gas, coal and LNG power stations won't be necessary.

Paul H.

Amen!!! It's taken a couple years longer than the companies said it would take(I watched month after month), but it seems that it is finally here! I am going to cover the whole roof of my house!
$1 per 10 watt*year!!! That's a heck of a lot of energy for not much! Liquid coal?? do these people have special needs? I hope Mitt Loses, and anyone else that is that stupid with their energy policy.

Cyril R.

The advent of low cost thin film cells, that according to Nanosolar will be able to be produced for $0.99 per Watt

They actually claim they can sell profitably at $0.99 per Watt peak. So they would have to be able to produce for considerably less than buck a Watt.

Cyril R.

Could this be the begining of the end of all other forms of solar power.

Impossible to say. Storage for rooftop PV is still a huge showstopper in terms of being able to push out other solar technologies. Besides, there's plenty of room for all the solar techs out there. There's no need to think in this way.


Costs sound good, but unless I've missed something then it is still expensive for normal use.
I am taking it that if you wanted it on your roof, making it into a panel and installing it are going to bring the costs to you up to around $3 a watt, so for a 1kw installation you are paying $3000.
Of course, this is peak watts, so you have to multiply by the sunlight availability in your area.
For a really good location, say LA, you might get a factor of around 25%, so to generate an average flow of 1kw you would pay around $12000, and that is still without storage for power at night and so on.
My guess is that they are aiming the initial panels for utility scale generation because of issues like this, as the installation costs and maintenance and so on would be lot cheaper there.
The very high feed-in tariffs for solar in Europe are probably the only thing that make this economic, although perhaps peak load in very hot areas where air conditioning is important could cost reasonably.
Good progress though!


In the original post it states:
430,000 Mw of capacity per year in CA according to this CNBC video.

Oops - this is off by 3 orders of mangnitude. 430,000 MW would be equivalent to about 400 nuke plants. The correct number, as stated in the CNBC video, is 430 MW of capacity per year (peak, of course).


For the benefit of the less informed, how many KW would a typical (average?, median?) all electric home use in a day?


That's a surprisingly difficult question!
For a start it depends where you live in the world - the Europeans manage on a lot less energy than the US, and the Japanese do better still.
Also the energy mix varies - for instance, in my home, the UK, most heating is provided by natural gas piped into the home, and then combusted in pretty efficient boilers on the spot so you don't get the same waste as you do by combusting it centrally and using it to generate electricity.
I am going to assume that you live in the US, here is a table of relative electricity consumption per person in different states in the US:
As you can see, this is around 12,000 kwh for the US, and 7,000 odd for California
(To work out what a kwh is in terms of installed capacity, divide by the number of hours in the year = 365*24=8760, call it 10,000 for convenience, so we are talking about Ikw running 24 hours a day to generate the average US energy flow)
But hang on, this is not just for residential, but all the electricity supply,
however, check out here:
From that you will see that this is residential consumption, again per capita, and that the utility which uses electricity for most of it's residential power is SMUD, and that that averages around 750kwh per month, or again around 10,000kwh/year.
So why have we come back to around the same figure, when the first did not exclude uses other than residential?
Because not everyone uses electricity to generate all their use - some use oil or whatever.
It all boils down to that as a rule of thimb you allow around 10,000kwh per person, or 1kh of installed capacity.
For things like solar, you have to reckon that the sun don't shine all the time, so you might be talking about five times the installed capacity, reckoning on only getting power 20% of capacity, so you could really do with 5kw pp.
If you wanted to go solar though, things aren't that grim.
For a start most homes in the US are pretty energy inefficient, and you would be nuts not to do something about that first, with the cost of renewables.
Secondly, residential solar thermal is way cheaper, so you would set up so that most of your hot water came from that in SC (you would get around 50% in Northern Europe, and similar climes)
To give you an idea of how it pans out, most solar installations are around 2.5kw, but that does not provide all of a house's power, and if it were cheaper a lot more would be very welcome.


Typically one measures power in KWh, not KW, but the average number of KW would be the KWh divided by the number of hours in a month.

My recollection is that the average house uses about 1000KWh/month. That's a very rough figure though, and I don't know about all-electric vs a combination of electric/gas. I expect it would depend a lot on the climate as well.

Usually it is far more cost effective to first work to reduce consumption as much as you can before you worry about putting solar on the roof. That which you don't use, you don't need to generate. At these new price points, that might change some, but supplies are still going to be tight for the next several years, so I would expect that it would still make sense to reduce consumption first.


I had seen elsewhere that initial manufacturing capacity was 430MW/year. That is about an order of magnitude larger than other startup plants, so these guys are definitely being aggressive. What the cost will be once they reach full scale production remains to be seen. I've heard claims that there are resource constraints for CIGS which will place an upper limit on how much of it we can produce, so even if the cost were to become very low the scaleup would reach its limit.

Don't expect to be able to buy panels for $.99/watt any time soon. Prices have been very stable the past few years as demand has exceeded supply. Lots of new production coming on line, both polysilicon, CIGS, and concentrating PV should lower prices somewhat, but I think the sellers market will continue.


Jim: The advent of low cost thin film cells, that according to Nanosolar will be able to be produced for $0.99 per Watt

Cyril R: They actually claim they can sell profitably at $0.99 per Watt peak. So they would have to be able to produce for considerably less than buck a Watt.

Actually, they claim they will be able to sell the panels (not just the cells) profitably for $0.99 per watt. But I agree with Big Tom, I don't expect to be able to buy panels at that price anytime soon, considering they've already sold out over a year's worth of production.


I took the price from Nanosolar to be $0.99watt for the cells, not the panels - so installed cost, at least residentially, would be around $3watt on a roof - do I have that right?
If the price is $0.99 watts already installed in a panel, that is way cheaper than I thought.


Clee, that answers my last!


This is heartening news. Congratulations to Martin and his team!

However, I just want to note though that it doesn't cost $.99/watt INSTALLED. Right now you need to add about $3 or $4 per watt to install solar modules. If Nanosolar Powersheets offer efficiencies in installation they MIGHT cost less but don't know how much less.

Right now First Solar sells it's modules for around $1.19/watt but a recent massive installation of their cells on a groundmounted array in Germany yielded a per watt cost of around $4.50/watt.

So Nanosolar's announcement beats First Solar's price but the improvement is incremental and makes a small dent in the price of PV electricity. On the other hand both of these pioneering manufacturers are going to sell out their production for a long time.

To compare, crystalline silicon arrays' installed-cost ranges between $7 and $10/watt depending on what kind of hardware and connectivity is involved.


Mike, I haven't been able to find the prices of First Solar panels. Could you give me URL showing their prices? $1.19/watt sounds pretty nice.

I can at least see the model numbers and watts/panel (if not their physical size and price) on their website, which is more than Nanosolar provides without an NDA.


This is the economics of the asylum.
I assume the installation you refer to is this one:
Being generous, and saying you get this for around $4watt ($171m/40MW) this is for peak capacity!
So your actual energy flow is around `1/5th the installed capacity, .2 of installed ( actually you might be looking at .17 in southern Germany, if you are very lucky) then this comes out to $20watt, amortised over 5 years that means that you come out to around again $4watt flow, or $4,000 kilowatt per year!
You can fool around with the figures a bit, because the installation will obviously last more than 5 years, but then you would have to add interest to the original capital as well, so you won't come out with very different figures.
So for this solar installation, you are looking at around $0.40kwh.
You can improve the costs a bit by putting it somewhere like the Mohave desert instead of Bavaria, but OTOH I haven't included anything for cleaning and maintenance.
This is a boondoggle reliant on the huge German incentives for solar, and in additon covering up good German farmland to no purpose.


Davemart writes
So why have we come back to around the same figure, when the first did not exclude uses other than residential?

Actually the reason is different. The first number is per capita use, including non-residential. So to get per capita residential use, you have to multiply that number by what percent of all electricity use is residential. That number is roughly 40%. The second number is residential use per customer, which means per electric meter, which is roughly the same as per household. The average household is roughly 2.5 people. So the per capita residential use is again that number divided by 2.5. As 1/2.5 = 40%, you get the same number. Or close enough when you use the real numbers, since it's not exactly 40% or exactly 2.5.

While that answers how much electricity an average home uses, it still doesn't answer what an average all-electric home uses. I don't know how to figure that one out.


Clee, what you say there is very true - I knew there was something not quite ship-shape in what I said, but couldn't be arsed to figure it out properly!
The other issue you raise, that of the all electric home, is I believe very approximately answered because it is specified in the link I gave that SMUD customers are pretty well all electric - the other utilities use much less electric per capita, and it says that they tend to use a lot of other resources.
So however you cut it, for the purposes of back of the envelope calculations, you are looking at an electric energy flow of around 1kw per person in the US.
In a single occupancy dwelling that goes up some, in a multi-occupancy one down - two use a lot more energy when divorced!


The accepted metric for solar installations is peak wattage. Of course average/peak ratio is important for determining say how much energy/year an installation will supply. The two simplest cases to do, which assume no atmosphere:
Whole earth average for a horizontal surface .25
(area of circle/area of sphere). A bit higher at the equator, and less at the poles:
Average for a tracking collector .50, independent of lattitude.
Once you add clouds and atmospheric scattering things become messy.
At mid latitudes a south tilting collector will do considerably better than a horizontal one.


They call this number, $1.19, "Production costs" which I assume includes their profit margin:
I don't think they would actually reveal their mark-up to their customers...but maybe.

DaveMart, You are showing signs of being a troll with a political agenda, so I hesitate to address you but your rant goes way beyond what I said and what is actually in the facts out there:

The array costs 3250 Euros/kW so you do the math.

As to the strength of the sun in Germany and the energy productivity of the array...I did not address these but you saw red and charged nevertheless! They estimate their yearly production at 40 million kWh and will be paid around $.45/kWh.

Germans have what they have and they are using what they have. They are not as lucky (or unlucky) as Americans in having massive amounts of natural resources to squander and their energy costs reflect their need to import most of their energy. We may help send the world into a tailspin because of our belief, which I think you share, that energy must be dirt cheap. Their laws in this area are far in advance of ours. Also thin film is particularly suited to the diffuse light of Germany.

You seem to misunderstand feed-in tariffs which over the long haul will allow the owners of the array to make a profit. It is a mandated price per kWh that they receive and is eventually mixed in with other rates and paid by all ratepayers in Germany. It is a very popular law and ordinary people invest in these arrays (solar funds) so they benefit from the higher rates as investors in addition to the environmental benefits.

Because of the security that a feed-in tariff offers, they used money from a solar fund and also got outside financing from a bank.

The array is built on a former military base so no existing farmland was used.


Does this $1/watt mean (e.g.) $300 for a 300W peak panel ? Or does it mean something else ? How much does a nanosolar 300W panel cost ?

(at 14% efficiency that panel would be 2,14 square meters I believe, or 1,50m x 1,50m)


Mike, your response is beyond weird - I thought the costs were out of line and said so, and referenced and gave figures for my reasoning - hardly a rant.
I have no agenda against renewables, and on this forum have commented very favourably on many renewable resources.
Regardless of how you feel about the conventions of presenting costs, what it comes down to at the end of the day is how much you have to pay to heat and light your home.
I notice you do not challenge the figures I gave.
This is just silly money.
No doubt the people who are putting up the array will make money, due to foolish feed-in tariffs, but the costs will be vast and the returns negligible, with the bill footed by the Germans.
Since most of the costs are not in the array, you are unlikely to get huge future cost reductions, although for sure you will get some.
As regards to the Germans having what they have and using it, they sure are - they plan to built 6GW of coal fired power, which they will combine with eco-bling like this PV plant, with the net effect that CO2 emissions will go up and so will costs - not that I mind the Germans subsidising the development of PV, but there is not a lot of sun in Berlin in midwinter, and fantasy does not take the place of facts.


Actually, Mike, I was a bit disappointed too, when I ran the figures - I had hoped that PV power was closer to competitive, and even though great strides have been made, found that the cost difference was still huge, and that in areas of ancillary cost where it is difficult to see much potential for rapid decrease.
That may possibly have lead to a tone which you interpreted as a 'rant' - I was hoping for perhaps $0.20 kwh - still darn expensive, but on the right planet.


Two considerations to add to the discussion:

1. It could be helpful to discriminate between residential / commercial applications and utility scale electricity generation.

2. With more widespread adoption there needs to be better accommodation by the Grid.

Better accommodation means welcoming grid ties and allowing the meter to run backwards.

To do this successfully under high growth conditions will be a challenge, requiring a smarter Grid. (http://jcwinnie.biz/wordpress/?p=2493).

Vinod Khosla believes this in necessary for utility grade solar thermal power (http://jcwinnie.biz/wordpress/?p=2218) and it also would be helpful when considering the residential / commercial sector. It gives the Grid greater resilience.


1) Remember I originally posted this to comment on installed costs of solar arrays, not to engage in a global argument about financing clean energy. You took my post as an endorsement of what was simply reporting facts.
2) They don't have a good coal-replacement strategy in Germany and the feed-in tariff has not been designed as such BUT neither do we
3) The feed-in tariff HAS caused explosive growth of renewables in Germany and it is a pay for performance standard, so if no energy is produced, no one gets paid
4) All big changes in infrastructure require some form of regulatory intervention and direct or indirect subsidy by the state: this intervention is only newer and maybe more obvious in the case of renewables
5) We in the US with our much stronger renewable energy flux in general, will probably end up paying less than the Germans to install renewables because of higher productivity. On the other hand, we will pay more for transmission costs if the renewables are in remote locations.
6) I'm still puzzled by your using YOUR figures rather than the figures that are publicly available about the Waldpolenz array, including its cost. The Waldpolenz array is not about what YOU think but about what Germans think they should do about their energy future and what it costs THEM. If you lived in Germany and supported renewable energy and had a few Euros in your bank account you could invest in solar or wind or whatever and see a decent return on your investment.
7) We are going to have to pay more money either through taxes or through higher electricity rates if we want nice new clean energy infrastructure...it's not just going to slide into place on its own at the cost of depreciated coal, nukes.


To take your points in order:
1)'Remember I originally posted this to comment on installed costs of solar arrays, not to engage in a global argument about financing clean energy.'
I had no idea why you made your post, nor was my response meant to be in any was a personal comment - when I ran the numbers I was just a bit shocked to find PV so uneconomic, and said so.
2)'They don't have a good coal-replacement strategy in Germany'
The whole point of these measures is supposed to be to reduce CO2 emissions. If they don't do so then it is reasonable to criticise them.
3)'The feed-in tariff HAS caused explosive growth of renewables in Germany and it is a pay for performance standard, so if no energy is produced, no one gets paid'
Sure, you are going to produce some energy - but if it is irrelevant to the amounts required at any reasonable cost, no-one is going to want to.
4)'All big changes in infrastructure require some form of regulatory intervention and direct or indirect subsidy by the state: this intervention is only newer and maybe more obvious in the case of renewables'
No, it hasn't.
Historically changes have happened due to reduced costs and/or ease of use - for instance wood to coal, coal to oil, oil to natural gas, and has nothing to do with subsidies.
I do not rule out the possibility or desirability of government charges for CO2 emissions in the future, but the only instance historically to which your comment
has relevance is the change to nuclear power, which did not happen in the end.
5)'We in the US with our much stronger renewable energy flux in general, will probably end up paying less than the Germans to install renewables because of higher productivity.'
It's got nothing to do with higher productivity, and everything to do with the fact that it is sunnier in the US and there is more room, so more possibility of putting loads of windmills up to generate more electricity per capita.
6)'I'm still puzzled by your using YOUR figures rather than the figures that are publicly available about the Waldpolenz array'
They were in no sense my figures but were instead figures from a referenced source, which I then rounded down to give a more favourable figure than that which you had quoted - $4.00 per watt, vs the $4.50 watt you referred to, so my comments were based on more favourable data than that which you used - why it sounded more expensive is because you have to look at how much power you actually generate over the year for your investment, not the peak wattage at noon on a summer's day.
7)'We are going to have to pay more money either through taxes or through higher electricity rates if we want nice new clean energy infrastructure...it's not just going to slide into place on its own at the cost of depreciated coal, nukes.'
Maybe, maybe not. Residential solar thermal is already very competitive, in many climates, for instance Germany.
In addition high altitude wind power, if we can figure out the technology, has the potential to be an order of magnitude cheaper than coal - and in northerly latitudes.
If you are talking about a premium for less polluting sources, that is fair enough - those who think that we are going to go for sources at 4 or 5 times the cost of current power are unrealistic, and in any case for a lot less than that we can figure out how to sequester the CO2 from coal.


Mike, thanks for the URL. I see they compare $1.19/W for First Solar with $2.80/W for traditional solar systems. Since traditional solar panels don't sell for as cheap as $2.80/W, I conclude that First Solar isn't selling panels for $1.19/W either. Those production costs don't include mark up or profit. ( http://www.solarbuzz.com for average and lowest PV module prices. I still wonder if First Solar is one of the companies they survey to figure out those prices.)


Excellent post!
100% correct that you have to have more sophisticated metering - and reward feed-back to the grid at peak times.
It is also true that regardless of the economics of utility scale thermal, residential solar would be good in new builds almost everywhere - you save loads of costs on transforming electricity to heat, and reduce the load on the grid - the lack of encouragement for it in the US and UK is almost criminal - and the lack of utilisation of ground source or air source heat pumps almost as much so.


I think it helps to have two strategies:

1) Be prepared to pay more in the near term for clean, sustainable sources as an investment in the future. Maybe not 4 or 5 times as much but enough to spur investment and growth.

2) work towards reducing the costs of clean, sustainable sources.

Feed in tariffs actually can help accomplish both goals as they decline over time to encourage industry efficiency. Your dismissal of them , Dave, seems to not to accord with their role in bringing down the cost of a bunch of existing renewable technologies.

I think people should be prepared to put their money where their mouth is if they care about climate change, etc. To substitute hope for a cheaper future technology for action now is foolish.

High altitude wind has some promise though there are a bunch of technical challenges as well as a liability concerns.

Furthermore, we have the technology now to use a whole bunch less energy: e.g. the Passivhaeuser in Germany use about 15% of the energy to heat that ordinary houses do. So in the coming years, we should be using a lot less energy, even as the cost goes up.


'1) Be prepared to pay more in the near term for clean, sustainable sources as an investment in the future. Maybe not 4 or 5 times as much but enough to spur investment and growth.'
If you have proper costings you do not actually pay more - you just recognise costs which are incurred anyway, and allocate them properly, for instance costs from coal emissions are currently uncosted, and take the form of high health bills, before you start adding on for CO2 emissions.
What I don't like are green fig-leaves - so for example the coal which Germany is going to burn is lignite, which is very dirty, and they are putting in a bit of ultra-green PV, which costs a packet, when to reduce overall emissions they might be better off, for example, by sequestration - without proper costing it is impossible to evaluate how
much is gesture politics.
- sorry! I used to do cost and works accountancy, and always ask 'how much bang am I getting for the buck?'
and 'can I get the same result easier and cheaper?'
2)'Feed in tariffs actually can help accomplish both goals as they decline over time to encourage industry efficiency. Your dismissal of them , Dave, seems to not to accord with their role in bringing down the cost of a bunch of existing renewable technologies.'
Your assumption is unjustified - I do not dismiss feed-in tariffs, but the rate at which they are set is a matter of careful judgement, or all you buy is a white elephant.

About technologies like Passivhaus I would 100% agree, and would go further and suggest that things like solar thermal hot water heating should be mandated.

Harvey D


According to our electric service provider, the average (well built) all electric home consumes about 10.0 Kwh/year/sq.ft. with 2 occupants. Add 10% to 15% for each extra occupant.

In other words, a well built, all electric 1800 sq. ft house should consume about 18 000 Kwh per year in the Montreal, Canada area.

The above are averages, the real consumption varies a lot depending on the quality of the construction, living style, heat and cooling levels etc. Variations of 7.0 KWh to 21.0 KWh per square feet per year is not uncommon.


Yes, there are unaccounted-for costs in coal, oil and nukes. But that still means that people's per kWh costs will be higher if you account for them. You can justify that cost in a positive way by saying they are paying for a clean energy source OR you can do it as you do by saying that we are evening out the playing field. A feed-in tariff makes the former a reality while a carbon price makes the latter a reality. We could probably use both.

Yes, feed-in tariffs can be either meaningless or very helpful depending on how they are set but to simply dismiss them as "silly" is a bit of pessimism we cannot currently afford.

The California Energy Commission is recommending them to help meet the state RPS standards.


Thinking about the figures a little more I am not quite so down as I was at first, when some here kindly referenced some current costs.
At Nanosolar/Firstsolars costs we are looking at $$4.00 or $4.50 installed peak watt for utility-scale generation.
Ignoring the bits here about the availability of tellurium, but focussing on the efficiency,
you come out to around 10% for current cells.
Nanonsolar is likely to be in the same ball-park, both for efficiency and possible limitations on avilability of rare resources.
So something like this would be nice:
No worries about the availability of silicon - current shortages are just in processing out the highly refined form needed.
The interesting thing is that the 3 times greater efficiency would reduce the installation and maintenance cost by similar percentages, quite aside from any gains from experience.
With luck and a following wind you might be talking about 12-15c/kilowatthours installed cost - and I don't mean peak watts, but watts generated - and that is at the point of use, not needing to go through the grid and so on.
IOW it seems unlikely to me that costs or availability of materials for Nanosolar or First solar are good enough to generate electricity universally, but we are getting within one breakthrough or so of being there, and already can certainly economically generate electricity for peak use or off-grid by means of solar PV


Mike. I said the rates of German feed in tariffs were silly, if they make electricity at the costs we were discussing economic to build - or at least would be if used on a major scale - doing 40MW or so at those rates is fine, but the costs if you go to GW scale installations rapidly go out of control unless you have the right scaling down of the tariffs.
Not everyone is equally wealthy, and some people in northern areas end up freezing to death if they can't afford the heating bills, so you have to be careful.
I should have said that if would be silly to subsidise electricity production on a major scale at those rates.


It would be better to set feed in rates generously and then provide some form of exemptions or aid to the poorest. Yes, this is another non-market function but why shouldn't middle class people pay a little more for their electricity to support a cleaner future?

As is for solar, in the lower 48 in the US, we can afford to set the rates 30-50% lower than in Germany because of the higher rates of insolation...investors will still get the same return on investment as they would under German law. If we want to make it less generous...fine but it will have less of a stimulative effect.


Mike, I agree with incentivising, but there are a lot of scams out there too - the ethanol from corn one in the US has become notorious recently.
At the rates we are talking about for PV, then you need $16-17bn to replace one 1GW powerstation - that's too much, on any reckoning.
If you build maybe 1GW, then costs fall a lot, then fine, but you have to have confidence that it will, and that you are not just subsidising boondoggles.
Here is what is happening with carbon trading in Europe:
So if this is accurate (and although the author has his own axe to grind, it is correct) Europe is already paying around $25bn into a slush fund for carbon emitting industries, and not reaping any efficiency benefits from it.
My point is simply that you have to be very, very careful that any subsidies work correctly - they can often lead to a wonderful land of excess profit, increased consumer cost, and no perceptible benefit at the end of it.


I did some quick calculations to see what the end kw-hr costs would be for a homeowner who got some of these Nanosolar panels installed. Here are my assumptions:

$3/peak W installed cost
4 Hours @ Peak output / Day

In year 1, it will cost you $2.05/kW-Hr that you generate. Every year you keep the system in production your cost per KW-Hr will go down. So if you keep the system running for 10 years, your kW-Hr cost for the 10 years will be 20.5 cents/kW-Hr. For the 25 year lifetime of the panel, your cost would be 8.2 cents/kW-Hr. Pretty darn good if you ask me.


I think we have to be careful throwing around costs of installation. If a PV technology is brittle, and must be protected by a rigid panel, as is true with most polysilicon cells, the cost will be much higher (per meter**2) then if it a flexible material, that can be unrolled and fastened into place. Now that the cost of the photovoltaic is coming down it becomes increasingly important to make serious progress on the balance of system costs. These costs are likely at least somewhat dependent on scale. I can probably build a 1MW system for less than 100 times the cost of a 10KW system.

Cost benefit methodology needs to be carefully considered. Benefits should be corrected for the discounted cost of the power. As an example:
B= integral{ power(t)*price_of_power(t)*exp(-I*t)}
where: t is time in years:
power(t) is the expected power produced in year t.
price_of_power(t) is the estimated price of the power in year t.
I is a reasonable interest rate (say 6 to 8% per year).

You shouldn't need to be a calculus expert to be able to apply this, plugging in some numbers and using a hand calculator should be sufficient.

Some simplifications can lead to understanding:
If the cost of power doesn't change, then the benefit for an infinite lifetime is 1 over the interest rate, times the value of the power per year. If the cost exceeds this number you will never reach breakeven. If the cost of power is increasing with time, then the benefit is greater then this. If the cost of power increases faster than the time discount factor (6 to 8%) per year, then the later time years count most, and if the product lasts long enough you will eventually win.

If instead you ask: is it profitable for me to defer my purchase of a system until next year? If the cost of an equivalent system is decreasing rapidly, then it almost always pays to wait. Buyers of computers are aware of this dilemma, for a fixed budget, it pays to wait for a better product to appear. If PV costs start rapidly decreasing, and that trend looks sustainable, then it can be hard to justify not waiting until better systems are available.

Cyril R.

Hmm. That may be a catch-22 bigTom. If everyone would decide to wait for PV to get cheaper, it won't precisely because they all are! But if they all decide to buy now, PV costs can go down more rapidly so it doesn't make sense to buy now!

It would only be true on the individual level. I've always found monthly net cost paid by homeowners to be more useful. PV systems can often be financed by increasing the mortgage, so there should be reasonable interest rates. Then, if the average montly payments for the PV system are lower than the average monthly savings, installing PV will make sense.

The market will take care of it eventually, but it's likely a bunch of people have to pay the price now in order for PV to get cheaper in the future. I also think the seller's market in PV will continue for a long time. A switch to consumer-market orientation could signify true competitiveness of PV systems though. Maybe we'll find out sooner than I've thought so far. We may also be disappointed in CIGS when we realize it has serious resource issues in being able to grow exponentially. I actually have more hopes for new silicon technologies rather than CIGS.


DaveMart wrote:
Also the energy mix varies - for instance, in my home, the UK, most heating is provided by natural gas piped into the home, and then combusted in pretty efficient boilers on the spot so you don't get the same waste as you do by combusting it centrally and using it to generate electricity.

The case for this isn't as clear as it may seem. If the natural gas is burned in modern large combined cycle power plant, the coversion efficiency is 60% of the lower heat value (non-condensing). Since the higher heat value of natural gas is about 10% higher, compared to a condensing furnace, the efficiency is about 54%. By the time to the electrical energy is delivered to the house, transmission losses might bring the efficiency down to 50%.

Not very good you say? Well, run this into even a moderately efficient air-to-air heat pump, and you will get 3 units of heat for each unit of electrical energy (heat equivalent). Use a ground-source heat pump, and 4 units of heat per unit of electrical energy can be done easily enough.

So with the gain from a heat pump, the heating efficiency of burning natural gas in a central generating plant can be 150% to 200%. The best condensing natural gas furnaces get 97%, and by physics can't go over 100%.


You can indeed increase the efficiency of a central gas burn, but only by going to the added expense of installing heat pumps.
In much of the US this is likely to be a fairly expensive option, indeed, looking back over this thread when I said that 'it is almost criminal that heat pumps are not installed in new builds' I find I grossly overstated my case.
The continental climate of the US, with in many areas temperatures dropping for long periods below zero, means that the much more expensive ground source heat pumps would be the preferred option.
There is nothing impossible about installing them, 97% of all new builds in Sweden have them, but they are dear, and with the historic price of energy in the States it is hardly surprising that not many are installed.
Of course, the calculus changes with concerns about GW and so on.
In the UK with a maritime climate which rarely goes below zero then all you need is the much cheaper air pump.
The reason why not many are in the UK is until recently we were self-sufficient in cheap gas.
Indeed, at current prices for the individual householder it is difficult to make an economic case for retrofitting to an air pump.
New builds are more hopeful, as the underfloor heating which works best with air pumps can be specified from scratch.
In the UK, if a home goes from gas to heat-pump electric, that saves around half on CO2 emissions given the UK's current energy mix - if we get more renewables in the generating capacity, then you do better still.
An interesting case in point is France, which is also climatically suited to air pumps, and where they are currently installing 50,000 a year - if you bear in mind that most of their electricity comes from nuclear, then you are talking about seriously low CO2 emissions!
For real efficiency short of nuclear or an all renewable set-up though, then some of the new Japanese fuel cells designed for domestic use are interesting.
In such a system you would pump natural gas to the house, where it is used to generate electricity, with waste heat going to heating, and any shortfall provided by the electricity run through a heat pump!

Cyril R.

Really efficient heat pumps are expensive though, especially for smaller residential buildings. It may make more sense to build one (or a few) central heat pump unit(s) for an entire city block or industrial/commercial area. Or for big appartment complexes, hotels etc.

Combined with high building insulation quality, there should be some massive efficiency gains to be had in electric heating/cooling.

Cyril R.

Sorry Dave, didn't got your post yet.

As you say, heat pumps aren't that exotic.

In fact, all refrigerators are heat pumps, albeit not very efficient ones.

Electric heating/cooling with heat pumps would definately be a good idea for France! So would electric transportation be.

They should just build more nukes in France and export the electricity to power heat pumps in other countries during the day and export nighttime nuclear electricity to charge other countries' plug-in hybrids. That way, they could continue operating at the high (economical) capacity factors, make good money, reduce European CO2 emissions.


Cyril, I believe you are talking about ground source heat pumps, which are pricey due to the need to sink the pipes - and they are indeed the most suitable option for most of the US
Air source heat pumps are pretty reasonable, even here in the UK where we always have to pay through the nose for everything.
Here is a nice new one from Mitsubishi:
they are cheap enough even for older buildings that if your boiler went (here in the UK we mostly use gas combination boilers ) that even in strictly economic terms it might be worthwhile considering installing one, although the cost effectiveness varies according to the exact details of your house, and your view of future gas prices.
For new builds they are a very good option.

Carl Hage

Great discussion.
Yousef writes: But with ~8-10% efficiency for CIGS panels, the cost will start to rise once land gets scarce. I've heard others claim even if the price is good, solar PV isn't practical because of the land area.

I was able to find land use and electric statistics for San Mateo County, CA, just south of San Francisco. For a 10% efficient horizontal PV panel, it comes out to 18/24/11/54 m2/person for residential/commercial/industrial/total electric uses. All electric needs could be met only by covering 68% of the buildings and parking lots on commercial and industrial land, without using residential or rural land. A 1000ft2 house has about 100m2 area, so it's not impractical to meet residential needs covering roofs of houses.

You need about 14m2 PV to power a 15Kmi/yr Tesla electric car, or a 10x15ft covered carport.

Coal takes more land by a factor of 10 if you include the mine, and PV needs less than 4x just the plant area-- based on the Coal Creek Station in SD.

The $1/watt is really significant considering panels cost around $4/watt now. I don't think it's fair to assume that installation costs will be the same-- they need to come down. Does it really take $200-400/m2 to install? Mass-produced mounting hardware and lots of contractors can bring down the cost. A (non-PV) carport kit costs $23/m2-- double that with installation, and you can see how covering a shopping center parking lot is practical.

It's also not fair to only compare cost to 100% utilized base load plants. See an interesting cost table from the CA Energy Dept or the full report. Simple cycle gas turbines cost $.60/kWh because they are used 5% of the time (missing column in the table). This report assumes $9/watt installed PV cost.

Supposedly with the 40% tax-credit in CA, PV panels at current costs just about break even with interest included. Looks like we are seeing a 50% cost reduction, with more possible in the future, so no need for the subsidy. The Coal Creek station in SD gets coal delivered at $10/ton-- literally dirt cheap if CO2 is free.


My town wouldn't let me build a solar carport on my driveway because of some 25 foot setback rule. But I agree, there's lots of roofs, parking lots and other places to put PV as a dual use thing so that PV doesn't take up any additional land in those places.


I would be glad if you would check my reasoning from earlier in the thread.
Like most here I was pretty pleased and excited at the thought of the Nanosolar panels, but then Mike referenced a build in Germany, using First Solar panels, which in panel form only come in at $1.19 - the build cost of $171 for 80MW was still produced power for around $0.40!
I allowed a use of 20% of capacity and depreciated the capital over 5 years - sure, I could have allowed more years, but OTOH I did not put in any interest charges.
I was disappointed, but perhaps I have missed something, and would be grateful if you would check my figures and reasoning - hopefully I have missed something.
As you say, without coal at least paying for some of the crap it puts out into the atmosphere, let alone CO2, it is difficult to beat on price, but I had hoped we were nearer than that.


I don't know of any 40% solar tax credit in California. There's a 30% federal tax credit limited to $2000 max for residential, and a $2.50/watt CA state rebate.

Kit P

Technofossil, when was the last time it was 30 below in San Mateo?

One of my family that still lives in California can not install solar panels or a cloths line because it might make the neighborhood look tacky. There does not appear to be a limit on the number of BMWs in the driveways.

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