# Ariz. Team Seeks Fossil-Fuel Cost Parity, Using Solar Energy Concentrators

245

I pay about $0.10/kWh. (1000 W per Hour) ### Re:What does$1/W mean? (5, Informative)

#### tmosley | more than 2 years ago

A watt is a unit of power, a watt hour is a unit of work. The goal is $1/W which means that a 1000 W system, which produces ~8KWh per day (more further south), only costs$1000, and would pay for itself in about three years, making it economically viable for most people.

### Re: (2)

#### wealthychef | more than 2 years ago

a 1000 W system, which produces ~8KWh per day

Pardon my ignorance, but shouldn't a 1000 W system produce 24 kWh per day, since there are 24 hours per day? Or is the 1000W input, and the 8kWh output?

### Re: (2, Informative)

#### Anonymous Coward | more than 2 years ago

The sun does not shine 24hours/day... at least not on our planet.

### Re: (2)

#### wealthychef | more than 2 years ago

Does the angle of the sun come into play here? Is it really the same at 4PM as at noon? Or is 1000 W an average?

### Re: (3)

#### rcw-home | more than 2 years ago

Does the angle of the sun come into play here? Is it really the same at 4PM as at noon? Or is 1000 W an average?

A number like 1000W would refer to the peak power output that you'll get from it with the solar cells perpendicular to the sunlight with optimally clear skies. Since the earth receives a maximum of about 1100W/m^2 of solar energy, and ordinary silicon cells are about 12% efficient, you can expect such a system to be a little less than 10 m^2 in size.

4pm is not noon, no. First off, the lower the angle of the sun in the sky, the more atmosphere it goes through, which filters things out somewhat. Second, while you can steer the solar panels so that they are always perpendicular to the sky, most are just fixed to a south-sloped roof and more of their surface area will be going to waste.

If you google for insolation map [google.com] you can get nifty maps of what areas get how much sunlight. Note that most of these maps are for plain photovoltaic installations, where diffuse light (cloudy skies) is still better than nothing. When you're using solar concentrators (mirrors), those mirrors can't focus anything but specular light (sunny skies). I don't know if any maps have been drawn taking that into account.

### Re: (2)

#### Xacid | more than 2 years ago

Technically it does. You might just have to chase it around a little. ;)

### Re: (2)

#### Jamu | more than 2 years ago

It certainly does. It's always illuminating half of our planet at any one time.

### Re: (2)

#### Dunbal | more than 2 years ago

No because the sun doesn't shine 24 hours per day. Also solar panels do not product 100% of their rated output if partially covered by shadows, debris, etc. Also you normally don't see solar panels that move to maintain the optimal angle with the sun except in very expensive set ups. Therefore you often need many more Watts' worth of solar panels than what you calculate your electrical usage as.

### Re: (2)

#### zippthorne | more than 2 years ago

Divide that by pi to account for the varying angle of the sun through the typical day and you'll see it's quite close to the 8kWh they're claiming as an average.

What you're doing this: \int{sin(x)dx_{0}^{pi}} \over \int{1_{0}^{2pi}}

The assumption here being that you can approximate the output as P*{sin(x) : 0<=x<=pi ; 0 : elsewhere}

### Re: (3)

#### fast turtle | more than 2 years ago

The short Answer is "NO". The reason for this is you never figure on more then 5 hours of Peak Sun unless you're at the equator, where you can figure 8 hours. The reason for this is pretty simple. It's called Axial Tilt, resulting in our seasons.

Why the 5 hour figure is simple and it's called Winter. That's when you have less sunlight that provides energy due to angles of incidence. Sure a PV panel can provide some output if faced directly at the sunrise but until 9am it's going to continue increasing as the amount of energy reaches saturation levels of the array. This will remain until 3pm (1500) during the winter as the sun passes it's peak and begins declining until the energy provided is less then what's being demanded.

In order to retain reliability, a PV array is generally in a fixed possition that's solidly mounted. This ensures the maximum amount of energy will be generated during the Peak Sun period and may include a seasonal adjustment for Summer/Winter tilt. Any method used to shift a PV array has to remain as mechanically simple as possible and the only ones that work reliably with minimal maintenance are fixed angle.
Yes you can use a more sophisticated tracking system but then you're reducing the actual output by the amount needed to power the tracking system.

### Not so simple (2)

#### Iamthecheese | more than 2 years ago

It would have to cost 1 dollar per watt over the entire life of the device including manufacture, installation, and disposal.

### Re: (2)

#### polar red | more than 2 years ago

they mean 1$per maximum possible output wattage. (so a 1000000$ for a 1MW peak power plant)

### okay, makes sense now, thanks (2)

#### OrangeTide | more than 2 years ago

I see. so 1MW system can deliver 1000 kWh every hour. At $0.11 running 24/7 it could theoretically bring in$964,000/year and basically pay for itself. Assuming everyone had to pay 11 cents (industry probably pays a lot less, these are just so numbers I made up).

### Re: (3, Insightful)

#### Dunbal | more than 2 years ago

You are forgetting:

1) Solar panels produce direct current, not alternating current. Direct current is almost impossible to transmit across any meaningful length of electric cable.

2) Converting DC to AC is possible, however there are efficiency losses and thermal losses - these come out of your "profit"

3) At some point you are going to need to replace your solar panels - they only last 15-25 years. You need to set money aside for this, unless you plan on shutting down your plant at the end of 15 years.

4) Energy companies do not buy electricity at the same price at which they sell it to you. Often there is a HUGE discrepancy. Ahh, monopolies.

5) The obvious one - the sun doesn't shine 8 hours a day so your 1MW system will probably deliver 300kW every hour on average.

6) To provide power at night you will need some means of storing energy. Batteries work, but they need maintenance and they do wear out over time. Less profit.

Oh - suddenly it's not so profitable anymore.

### Re: (2)

#### Dunbal | more than 2 years ago

my bad - there is no edit button - point 5 should read: the sun doesn't shine 24 hours a day...

### Re: (2)

#### heathen_01 | more than 2 years ago

I just assumed you were posting from the UK.

### Re:okay, makes sense now, thanks (5, Interesting)

#### vlm | more than 2 years ago

Direct current is almost impossible to transmit across any meaningful length of electric cable.

Humorously, you have it exactly wrong. The longer the cable, the (relatively) cheaper the cost of HVDC conversion gear vs the rest of the project.

The power delivered by a AC line is based on the RMS voltage. However you have to insulate to peak, which is somewhat more. Insulation is a pretty major design constraint, as arcs to the ground or towers is kind of a waste of power...

As a very rough guess on a medium length line you can push about 1/4 to 1/3 more power for the same cost if you switch to DC.

The power levels I'm talking about are a couple GWs, distances of dozens of miles, costs vaguely around gigadollars. Capital costs of about a buck a watt per 50 miles, lets say. You can see the motivation of placing plants nearby cities, rather than in the middle of nowhere.

You can do long distance AC, and they used to, it just costs a heck of a lot more.

### Re: (3)

#### Dunbal | more than 2 years ago

Hmm? I thought the whole reason we use AC (thanks to Edison winning the argument with Tesla) was because there is less loss over long distances when compared to DC. Edison wanted One Big Plant generating power, and Tesla wanted many small, local plants. I guess I will have to re-read this - I apologize, I'm a biologist not a physicist.

### Re: (2)

#### francium de neobie | more than 2 years ago

That was the a century ago when people hadn't discovered how to step up and step down DC voltages. There're still problems with transmitting high voltage AC across long distances - many long distance runs are actually HVDC now.

### Re: (3)

#### HornWumpus | more than 2 years ago

Back in the original AC vs DC battle it was damn near impossible to raise DC voltages and damn difficult to lower them without wasting a large part.

With AC a simple power transformer could raise the voltage on the lines. In the old days AC had a massive transmission line voltage advantage. These days it has the RMS disadvantage.

### Re: (3)

#### Lloyd_Bryant | more than 2 years ago

Hmm? I thought the whole reason we use AC (thanks to Edison winning the argument with Tesla) was because there is less loss over long distances when compared to DC. Edison wanted One Big Plant generating power, and Tesla wanted many small, local plants. I guess I will have to re-read this - I apologize, I'm a biologist not a physicist.

You mean the argument that Edison *lost* - he was the big proponent of DC, while Tesla and Westinghouse were behind AC.

### Re:okay, makes sense now, thanks (5, Informative)

#### DarkOx | more than 2 years ago

Wow, umm no.\\

Go back and check your history. Edison LOST that argument with Tesla. Tesla wanted AC because it was better for running motors and was more efficient for long distance transmission. Edision wanted DC because its arguably safer.

### AC, DC, transmission efficiency (2)

#### Beryllium Sphere(tm) | more than 2 years ago

It is high voltage that is more efficient for long distance transmission. The difference between AC and DC for that is that AC is relatively simple to step up in voltage with a relatively simple machine, a transformer.

### Re:okay, makes sense now, thanks (4, Informative)

#### tylernt | more than 2 years ago

Tesla wanted AC because it ... was more efficient for long distance transmission.

With the technology of the time, sure. Modern semiconductors have made high voltage DC-DC conversion pretty darn efficient though:

"For long-distance transmission, HVDC systems may be less expensive and suffer lower electrical losses" -- http://en.wikipedia.org/wiki/Hvdc [wikipedia.org]

better for running motors

Also, brushless DC motors have also made AC pointless (to an extent).

### Re: (3)

#### linuxpyro | more than 2 years ago

Edision wanted DC because its arguably safer.

Edison wanted DC because it was what he had started working with, and he wanted to keep using it.

The ironic thing though is that high voltage DC is actually kind of dangerous to work with, more so than similar AC voltages. This is because of the way inductance and capacitances behave as the frequency increases. As the frequency increases a capacitance starts to look more like a short, while an inductance starts to look more like an open. At DC (IE, at 0 Hz), it is the opposite. In DC, an inductance will resist changes in current. This makes it harder to build DC overcurrent protection devices, as in the event of a short the inductance inherent in the wiring can cause a voltage spike which can maintain an arc. In alternating current the zero crossing (every 8.3 ms at 60 Hz) inhibits this. Lack of a zero crossing can also make it harder to "let go" if you come in contact with a live wire.

At transmission-type voltages, though, like what you'd use to get power across the country it's kind of a moot point as you don't really want to get between either of them and ground.

### Re: (2)

I pay about $0.10/kWh. (1000 W per Hour) The figure in the OP is highly non-standard usage. In the US, only the kilowatt is a unit of energy. ### Re: (3, Interesting) #### vlm | more than 2 years ago I pay about$0.10/kWh. (1000 W per Hour)

What it probably means is they're scammers. Capital costs for coal and nuke run from $1.50 to$3.00 per watt installed. They're claiming $1 per watt. The problem is no matter how unconventional the heat source, no matter how magically free, the employee lunchroom costs$ per plant, the parking lot paving costs $per plant, the pipes from the magic heat source to the turbines costs$ per watt, the turbine itself costs $per watt, the water pumps and filters cost$ per watt...

PERHAPS they mean the capital cost of their magic heat source alone costs about $1 per watt. The problem is some recent historical nukes (not in the backwards USA, but civilized countries like France, etc) have come in at$1.50 per watt total plant cost delivered. So, on one side, their costs probably will decline as they are new vs the very mature nuke industry. On the other hand, can you build an entire thermal electric plant for well under 50 cents per watt? Then again, can a new tech be nearly as reliable as ancient technology nuke plant?

### Re: (2)

#### ColdWetDog | more than 2 years ago

I pay about $0.10/kWh. (1000 W per Hour) What it probably means is they're scammers. Capital costs for coal and nuke run from$1.50 to $3.00 per watt installed. They're claiming$1 per watt. The problem is no matter how unconventional the heat source, no matter how magically free, the employee lunchroom costs $per plant, the parking lot paving costs$ per plant, the pipes from the magic heat source to the turbines costs $per watt, the turbine itself costs$ per watt, the water pumps and filters cost $per watt... PERHAPS they mean the capital cost of their magic heat source alone costs about$1 per watt. The problem is some recent historical nukes (not in the backwards USA, but civilized countries like France, etc) have come in at $1.50 per watt total plant cost delivered. So, on one side, their costs probably will decline as they are new vs the very mature nuke industry. On the other hand, can you build an entire thermal electric plant for well under 50 cents per watt? Then again, can a new tech be nearly as reliable as ancient technology nuke plant? My impression (and damn these mindless 'articles') is that this is an ultimate goal. That figure isn't unreasonable even if it's cheaper than a coal fired plant. Small scale repetitive parts may well bring down capital costs compared to large purpose build structures - the employee break room is not the big ticket item in a nuc plant. Even if they don't get to the$1/watt figure, you have to remember that typical costs for nuc plants especially have enormous subsidies from the government in terms of waste disposal and insurance costs. Likely the same if you figure out the true environmental costs from a coal plant.

So, I'm not sure that they're a scam but equally unsure that it will lead to any significant commercial application.

I like the glowing ball, though. A whole field of those would be neat.

### Re: (3)

The theory is that if $1/watt is the installed cost of solar panels, including labor and inverters, and you don't have to pay for fuel, and the maintenance costs are very small, it would be cost competitive with conventional power sources. The cost stability - fuel prices can't go up, and once you install the panels you do not have to worry about prices changing for the next 25+ years, means that solar would become the preferred source of new power plants. ### Re: (2) #### vlm | more than 2 years ago But I can buy a whole French Nuke plant, delivered, the whole thing, not just a reactor, for$1.50/watt. Or maybe that was the Russian plant. And it runs 24/7 for years at a time... You're just talking about panels. Not mounting systems. Not active trackers, nor wiring, nor a control building.

I bet I could build a PV ish plant using these $1/watt modules for maybe$1.50/watt. But that only outputs "nameplate power" half the time over the course of a year... Hmmm. Just nuke it.

### Crystal Ball (3, Funny)

#### Aighearach | more than 2 years ago

I always suspected that PV technology was just missing a glowing crystal ball.

To the stars, Merlin!

### Solar cells is a bad idea for concentrators (5, Interesting)

#### BlueParrot | more than 2 years ago

If you are using concentrators for solar power you really ought to consider a thermal cycle like a brayton turbine or a sterling engine, rather than solar cells. Thermal cycles tend to have higher conversion efficiencies, the equipment is more reliable, and their power output is more easily converted to grid voltage ( AC as opposed to DC ). Solar cells also tend to see reduced lifetimes when used with very concentrated light. The advantage with cells is pretty much that they don't need concentrators to work, since they don't rely on a high temperature. They can also be used in places where space/weight is an issue, such as on sailboats, rooftops or sattelites. Thus if you are already using a bulky concentrator to get the light intensity up, you may as well use a sterling engine.

### Re:Solar cells is a bad idea for concentrators (5, Interesting)

#### Waffle Iron | more than 2 years ago

If you are doing a thermal cycle with concentrators, you need a *big* system. Small thermal engines aren't much more efficient than garden variety solar cells. (And presumably, concentrated solar would use high-tech cells that rival the efficiency of big heat engines anyway.) That means that you have to use a complex "power tower" arrangement with a field of precision synchronized mirrors pointed at one huge collector. You also need a big cold sink for thermal cycles; most power plants use a bunch of water for that, which is hard to come by in the desert.

The solar cell approach would also have the advantage of mechanical simplicity, and the ability to add capacity in small self-contained increments.

### Re: (3)

#### jmorris42 | more than 2 years ago

If you are using concentrators you either take a huge loss because solar cell output drops off at high temp (and suffer shortened service life) or you end up with a cooling system for the cells. Once you have the cooling system you should just yield to the physics and accept that the best use of concentrated sunlight is in heat, not direct conversion to electricity. Solar cells only convert a few frequencies (three in the article for this story) while dumping the light over to heat uses much more of the spectrum..

### Re: (3)

#### Waffle Iron | more than 2 years ago

So? At the end of the day, overall net system efficiency is what matters. Heat engines will always be saddled with the laws of thermodynamics, which force them to waste much of your enhanced spectrum. Solar cells, without the limitations of the Carnot cycle, can convert more of the available energy in the part of the spectrum that they *do* use.

Solar cells also don't need to be cooled to the same low temperatures that the outlet of a heat engine requires to run efficiently. In the desert, that's much easier to achieve.

### Re: (2)

#### vlm | more than 2 years ago

The problem is the Carnot eff at a relatively cool nuke plant is still around/over 33%. Good luck finding a production off the shelf solar cell with decades of operating experience that can dream of reaching 33% efficiency.

If you're willing to try "exotic" PV units, I want to try "exotic" carnot units, like maybe a century old binary fluid system like the old fashioned two stage mercury and water system. Maybe something a little less toxic that vaporized mercury. A century or so ago those ran around 50% carnot eff. They were also horrific toxic beasts, but maybe with some more advanced materials... Maybe a modified cycle with yellow hot helium thru an exotic turbine, then its waste heat thru a sodium vapor turbine, then an "old fashioned" water cycle...

There is also the engineering problem.... Thermal means a very traditional water boiler design, no question marks at all except for the weird source of heat. PV means multiple areas of engineering experiment, the concentrators, the PV units, the cooling system for the PVs, etc.

### Re: (2)

#### Software Geek | more than 2 years ago

Presumably, most of the cost in this system is the concentrators, not the PV cells. So, perhaps the PV cells can be replaced when they deteriorate without driving the overall system cost up too much.

### TFA gets it wrong, twice (2)

#### GPS Pilot | more than 2 years ago

Instead of using expensive PV cells, the solar telescope uses commercially available triple-junction solar cells

In fact, triple-junction cells are far more expensive than garden-variety PV cells. The cost savings come from the fact that sunlight is concentrated onto a much smaller area of cells. And this is hardly the first company that has applied that idea; for example, see Energy Innovations, Inc. [energyinnovations.com]

Roger Angel has designed a new type of solar concentrator that uses half the area of solar (PV) cells used by other optical devices and delivers a light output/concentration that is over 1000 times more concentrated before it even hits the cells.

If the light is concentrated over 1000 times, wouldn't the the device require less than 1/1000 the area of solar cells, relative to a solar panel that lacked a concentrator?

### Still the same problem as with all solar (2)

#### RightwingNutjob | more than 2 years ago

It doesn't work at night when you need electricity to power your lights. Which is especially a problem in the long winter nights when you need to heat your home. Can we please finally put this solar-for-everyone nonsense to bed?

### Re:Still the same problem as with all solar (5, Insightful)

#### Aighearach | more than 2 years ago

If only somebody would invent some sort of device that could store electricity for later use.

Then I could finally ditch the diesel generator I have to drag around to keep my mp3 player running!

### Re: (3)

#### RightwingNutjob | more than 2 years ago

And then you'd have the fun and moral satisfaction of purchasing a new set of heavy duty batteries every year or two. Mind you that would be a very large set, to account for the possibility of many short cloudy winter days in a row.

### Re:Still the same problem as with all solar (5, Insightful)

#### jmorris42 | more than 2 years ago

Look into the efficiency of a battery sometime. Unless you buy really expensive ones you lose about half of the energy putting it into and getting it back out. More losses if you are putting in AC and needing AC back out. And the really good (from an efficiency pov) lithium-ion batteries don't suffer many charge discharge cycles before hitting the 50% capacity point generally considered as replacement time. We currently have zero methods to store electricity that are cheap enough and effective enough for use on the grid. All electricity is generated as needed, with vast arrays of 'peaking power' generation capacity that largely sits idle. Believe me, if there were a good way to store electricity the industry would be using it already.

Worse, while electricity can be sent large distances, it is best to generate close to the point of use because of the line losses. So even if we were willing (and shot enough enviromentalists) to cover our deserts with solar arrays we would lose most of the power heating the lines getting it to where the customers are. Same for wind, it mostly occurs in areas where there aren't many people... or more accurately windmills near populated areas attracts more environmentalists.

### Pumped hydro is common. (2)

#### HornWumpus | more than 2 years ago

You pump water up hill at night, then use it for power during the day.

Yes fish blend.

### Re: (2)

#### ShooterNeo | more than 2 years ago

Uhh, ever heard of compressed air and salt caverns? That method is cheap and allows storage of large amounts of energy.

### Re: (2)

#### physicsphairy | more than 2 years ago

The sound you are hearing is not a diesel generator, it is the background "melody" of your songs. You need to stop letting your grandchildren (whose existence I infer from your five-digit UID) upload the music which is on your mp3 player.

### Re: (2)

#### BlueParrot | more than 2 years ago

Energy consumption is largest during the day, and thus solar can actually help do some load leveling. Yea, you can't get all the energy from solar, but having the plant peak in power output around noon is actually a good thing.

### Re: (2)

#### Desler | more than 2 years ago

Who ever claims that solar is for everyone despite a minority of kooks? Anyone sensible knows that you need to store excess generated energy in batteries for later or to have a backup generator for when night comes. What you are doing is the classic strawman.

### Re:Still the same problem as with all solar (5, Interesting)

#### cduffy | more than 2 years ago

If electricity is cheap in the daytime and scarce/expensive at night, the market will figure it out.

Maybe that means people have incentive to charge their cars at work. Maybe it means entrepreneurs buy excess electricity on the spot market during the daytime, use it to pump water uphill, and use the potential energy of that water to generate more expensive electricity at night. (Is that process lossy? Sure! But the market will only reward it if it provides a net benefit, so it's all good. Same for battery / ultracapacitor / other technologies -- if they're a good fit for the problem, someone will make money using them; if not, they won't).

### Re: (2)

#### proverbialcow | more than 2 years ago

(Is that process lossy? Sure! But the market will only reward it if it provides a net benefit or focuses supply to a few producers, so it's all good.

Fixed that for you. No need to even yield net benefit if you can choke supply. Ask OPEC.

### Re: (2)

#### Dunbal | more than 2 years ago

Peak electricity demand is lunch-time and supper-time. Lunch-time is pretty much covered with solar, and depending where you live, a good chunk of supper-time is too. "Powering lights" is by no means the biggest use of energy, even if lights is all you see when you look outside at night-time. The biggest energy consumption comes from things used to make heat (cooking, hot water) and everything with a motor (cooking again, air conditioning, laundry). Your light bulbs (especially nowadays with LED's and compact fluorescents) don't actually use all that much electricity.

### Re: (3)

#### cgenman | more than 2 years ago

We have an energy surplus at night, due to things like nuclear facilities that run at the same output no matter the demand. Really, we need to expand our power system to handle larger peak energy during the day, when everyone is running their air conditioners. Expanding into more nuclear is politically difficult. Gas and Coal are polluting. Solar would help us during the day, when power usage is highest.

So no, no one energy source can be our only generation point. But solar could definitely help when it is needed most.

### Decepticons.... (3)

#### kikito | more than 2 years ago

... ATTACK!

... And when we get the energy ...

### This guy is an astronomer (2)

#### Animats | more than 2 years ago

Roger Angel is an astronomer. He's done good work on telescope design. Hence the fascination with mirrors.

There have been many elaborate schemes for solar power using collecting optics. [solar-concentrators.com] The mirrors and supporting machinery usually end up costing more than you save by having less silicon area. Flat solar panels are simple to install, can be made resistant to high winds, and require minimal maintenance.

### Re: (2)

#### the_povinator | more than 2 years ago

Yes, when I saw the picture of their device I was concerned about winds. They make a big deal about the fact that it's made of out lightweight alloys. But the forces due to wind would be much greater than the gravitational forces, and the structure doens't look as if it is built in a way that you could collapse it somehow if a storm is expected.

### Clouds (2)

#### Arlet | more than 2 years ago

Solar concentrators have a disadvantage that they only work on clear days. On cloudy days, the light won't concentrate, and they're useless. Still useful in some areas with lots of direct sunshine, but not where I live, for instance.

### Maintenance is Good? (2)

#### simonbp | more than 2 years ago

The article seems imply that the fact that it requires so much maintenance is good because it's all local. But no matter where the maintenance jobs are, they cost money, and thus make it uncompetitive...

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