Free Power From the Sun

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mivey

Senior Member
They need to do more of what they haven't done -- storage development.
That's another concern. Let's just go with a solar cost of 30?/kWh for a moment (without subsidies). How much more will storage add to the ?/kWh? Considering that fossil and nuclear base load units can produce at 3-8 ?kWh solar seems to have too much of a chasm to cross right now. It seems to me it would take some major advancements in solar technology to close the gap.

I have seen pumped-back storage as well as some local ice production (used for cooling during the day). As for flywheels, I would think the other types storage you mentioned would make more sense. Storage is certainly something we need to develop. Energy conversion is such an inefficient process.

I like the idea of paying people a higher price for peak use of the energy they have banked in their EV batteries at night at a lower cost. Not a big resource but every little bit helps.

As for other battery banks, I just don't see how a battery bank is as cheap as running a turbine or engine using stored fuel.
 

tallgirl

Senior Member
Location
Great White North
Occupation
Controls Systems firmware engineer
That's another concern. Let's just go with a solar cost of 30?/kWh for a moment (without subsidies).

That would be a high cost. 1KW DC with a 90% conversion rate will produce 42 MWh over its life (25 years -- 1KW * 5.1 hours/day * 365.25 days/year * 25 years). $4,500 dollars (not a bad price for larger projects) per kilowatt DC divided by 42,000 kWH = $0.107 / kWh. Weird structural glarp is extra, but to get to $0.30 / kWh you're at over $13 / KW DC. There is some degradation of output, but not as much as had been expected -- many older systems are producing in excess of 90% of nameplate, decades later.

FWIW, I pay $0.10 / kWh imported and get $0.074 / kWh exported. I'd add more to my array, but I'd need to deal with an American Elm first. Which would require I buy gasoline -- something I don't do all that often on account of I drive an EV as much as I can ...
 

hillbilly1

Senior Member
Location
North Georgia mountains
Occupation
Owner/electrical contractor
Maintainance has to be taken into account also, to keep output at the greatest level, regular cleaning of panels would be required, storm and hail damage, cost of vast amounts of acreage per kw. Just seen a new solar farm that was a big eyesore, there was no grounds maintaince done (apparently was not in the budget) It was all grown up around the panels, and in full public view from the highway.
 

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
Part of the problem with estimating solar cost per kWh is that we don't know how long these systems are really going to last. Estimates and decisions are usually based on a lifetime of 25 years. It could be that the systems on average last much longer than that, or it could be they don't on average last that long. Much of the technology being installed today hasn't been around long enough to really know, systems that have been around a long time make up a very small sample size, and much estimation is based on lab tests of less-than-certain real-world accuracy.

In a decade or two will have a much better idea of how PV is going to work out.
 

tallgirl

Senior Member
Location
Great White North
Occupation
Controls Systems firmware engineer
Maintainance has to be taken into account also, to keep output at the greatest level, regular cleaning of panels would be required, storm and hail damage, cost of vast amounts of acreage per kw. Just seen a new solar farm that was a big eyesore, there was no grounds maintaince done (apparently was not in the budget) It was all grown up around the panels, and in full public view from the highway.

Google conducted a study on their solar arrays and found that "cleaning" isn't all that big a deal for arrays in areas that have regular rainfall.

As for maintaining the grounds, that's not a cost that's attributable to solar, nor is "acreage" -- I talked to someone today about how to put solar on 16,000 sqft of roof space. If I were infinitely wealthy, I'd be looking for unused roof space to populate with solar arrays.
 

hillbilly1

Senior Member
Location
North Georgia mountains
Occupation
Owner/electrical contractor
Google conducted a study on their solar arrays and found that "cleaning" isn't all that big a deal for arrays in areas that have regular rainfall.

As for maintaining the grounds, that's not a cost that's attributable to solar, nor is "acreage" -- I talked to someone today about how to put solar on 16,000 sqft of roof space. If I were infinitely wealthy, I'd be looking for unused roof space to populate with solar arrays.

I was actually refering to commercial installations, as you pointed out most residental installations are small and usually on rooftops, so they basically are using unproductive space anyway. The atmosphere is supposedly so polluted that all the rain in the world couldn't wash off it off! Like I have said before, it's a cool thing to do, but it's just not the most efficent way to produce energy yet.:)
 

tallgirl

Senior Member
Location
Great White North
Occupation
Controls Systems firmware engineer
That =was= a commercial sized install. 16,000 square feet is about 240KW DC, which comes out to about 215 KW AC. Residential is typically in the 3 to 6KW DC range, and off-grid goes about 1.5KW to 3KW. Large string inverters -- panels in series to make 500 to 600 volts DC -- are simple to install, especially with self-ballasting racking.

There are ways to make solar even more affordable that have nothing to do with credits or subsidies. Utilities will pay extra to have an array pointed some amount to the west, when demand is higher. In addition, the rooftop shading can reduce heat gain and A/C expense. Because solar panels are designed to resist hail damage, they can also increase the life expectancy of the roof. Lots of ways to "win" with solar.
 

c_picard

Senior Member
Location
USA
Land area required...

Land area required...

There have been numerous studies undertaken calculating how much land area it would take to power the world using solar alone, and having seen a few of the maps it is surprising how little space it would take up.
That said I don't believe solar is the only answer, just a piece of the puzzle.

If you've ever been to the sunny southwest, I think you'd have a hard time calling the desert "arable" land.
Even a lot what is considered arable land in this country (the breadbasket) wouldn't be if it weren't for intense irrigation.
As for deforestation, really? Estimates vary for sure, but do you think solar is going to even make the needle twitch when we're already cutting down a couple hundred thousand acres a day?

It seems that there is generally agreement that the technology that is lacking is not so much in the PV modules, but in the ability to get the power produced where and when it is needed efficiently.
 

mivey

Senior Member
FWIW, I pay $0.10 / kWh imported and get $0.074 / kWh exported. I'd add more to my array, but I'd need to deal with an American Elm first. Which would require I buy gasoline -- something I don't do all that often on account of I drive an EV as much as I can ...
You have a better solar footprint in some areas of Texas than we do in Georgia.

Here you could find yourself paying $0.085 for import and getting $0.035 for export to go along with a lower array output. Our non-subsidized PV costs seem to be a lot higher here for some reason, but our subsidized costs are close to the figures you gave.
 

mivey

Senior Member
Because solar panels are designed to resist hail damage, they can also increase the life expectancy of the roof.
How is that going to work when the array does not cover the entire roof? I can see patching a fairly new roof but ...
 

mivey

Senior Member
That would be a high cost.
... will produce 42 MWh over its life (25 years -- 1KW * 5.1 hours/day * 365.25 days/year * 25 years).

... $4,500 dollars (not a bad price for larger projects) per kilowatt DC

... = $0.107 / kWh.
I'll readily admit I'm no expert on the installed cost for small systems but I will say that we recently investigated the cost of wholesale units and they did not compete with our other options.

FWIW, we recently had a large retail customer investigate the long-term costs strictly from a savings standpoint and their consultant concluded it did not make sense for them either. I was not privy to all of their numbers.

As for retail units:
Why do these sites:
http://www.facts-about-solar-energy.com/solar-energy-cost.html

http://www.solar-estimate.org/

show installed costs at twice what you have (they show $8-$10 per watt as opposed to $4.5 per watt)?

I will also note that they show output at about 76% of what you gave (for Georgia anyway). They showed less than 33 MWh over 25 years rather than 42 MWh. Even for Austin Texas they showed 33.9 MWh for 25 years.

Both of those factors would push your cost figure of 10.7 cents/kWh to almost 27 cents/kWh.

FWIW, they also show an inverter replacement at year 15.
 

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
As for retail units:
Why do these sites:
http://www.facts-about-solar-energy.com/solar-energy-cost.html

http://www.solar-estimate.org/

show installed costs at twice what you have (they show $8-$10 per watt as opposed to $4.5 per watt)?

Maybe because they're not keeping up to date? :D Seriously. Look at the figures on page 11 here: http://www.seia.org/galleries/pdf/SMI-Q1-2011-ES.pdf

But with that said, your overall point is well taken, $4.5 per watt installed cost would seem to be about the lower boundary for residential, not the average, which SEIA pegs at $6.41 at the end of last year (and they are not an uninterested source, I realize).
 

mivey

Senior Member
Maybe because they're not keeping up to date?
That may be the problem as it appears to be a fast moving target lately (based on the info provided). I really don't know.

Seriously. Look at the figures on page 11 here...
Thanks for the link.

But with that said, your overall point is well taken, $4.5 per watt installed cost would seem to be about the lower boundary for residential, not the average, which SEIA pegs at $6.41 at the end of last year (and they are not an uninterested source, I realize).
I also find interesting the value they seem to bring to a home. A DOE link says about $3.9 to $6.4 per Wdc in California with the value decreasing with the age of the system. The calc tool gives a pretty wide range of value ($2-$8 per Wdc depending on the GA locations I dropped in for a test) but I find it interesting that in some cases the increased home value could more than offset the $/W cost of the system.
 

tallgirl

Senior Member
Location
Great White North
Occupation
Controls Systems firmware engineer
How is that going to work when the array does not cover the entire roof? I can see patching a fairly new roof but ...

It protects the parts that are covered, and every square foot of covered space reduces the heat gain by that much.

For large roofs, I like amorphous panels -- big and cheap. Solves the entire "I make too much power!" problem on account of they make half the power of poly-crystalline and even less than half of mono-crystalline. I have 280 square feet (more or less) and net to zero in the spring and fall. It would take about 700 square feet in amorphous to equal what I have with the poly-crystalline Kyocera panels I have. The cost per watt for the array is less, though the racking and installation is higher.
 
It protects the parts that are covered, and every square foot of covered space reduces the heat gain by that much.

It protects the parts that are covered from UV degradation, however the supports are required to penetrate the membrane if you have any wind resistance requirements. The life of the penetrations are far shorter than the life of the roof. Impossible to recaulk them since they are covered by the panels - except the perimeters - and the roof replacement will also be more costly since it requires the removal of the panels.

This is just ONE of the so many unaddressed issues associated with solar. If, and when , the solar panels themselves installed as the roof weather barrier then we can talk about an integrated solution, not an afterthought. I see a lot of short range thinking in the installation of solar systems that will bite the owner in the proverbial down on the road.:happysad:
 
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BillK-AZ

Senior Member
Location
Mesa Arizona
PV protecting the roof?

PV protecting the roof?

It protects the parts that are covered, and every square foot of covered space reduces the heat gain by that much.

... remainder removed ....

There are situations wherein the PV does not protect the roof. I know of a situation in Phoenix where USSC amorphous panels were installed on a white roof and literally destroyed the roofing due to the higher temperature that was produced by an essentially black surface. The PV resulted in a roofing temperature that exceeded the design temperature for the roofing. The adhesive backed PV modules could not be removed/reused and the basic roofing had to be replaced. A case of how not to do it.
 

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
The life of the penetrations are far shorter than the life of the roof.

Not exactly disagreeing, but how do you know that?

Impossible to recaulk them since they are covered by the panels - except the perimeters -
Um, you can take panels off temporarily to address roof leaks. Also, properly flashed penetrations should not be very reliant on caulking, if at all.

and the roof replacement will also be more costly since it requires the removal of the panels.
True, to a point, but solar systems will require periodic overhaul or complete replacement anyway, and thankfully roofs last longer than solar systems. So when it's time to replace the roof, it will just make sense to overhaul the solar system at the same time (or remove it and sell the materials, depending on your financial situation). In the future, one can imagine solar systems being overhauled every 20 years and the roof being redone every 40 years. In this sense, the only thing way it will be 'more costly' is if one fails to coordinate the two things.

Yes, it's stupid to put a solar system on a roof that is known to be within 10 years of the end of its life, but the solar industry is not encouraging people to be stupid that way. I've installed a number of systems on brand new roofs where the customer had the foresight to see that problem.
 
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tallgirl

Senior Member
Location
Great White North
Occupation
Controls Systems firmware engineer
It protects the parts that are covered from UV degradation, however the supports are required to penetrate the membrane if you have any wind resistance requirements.

Penetrate what?

There are ballasted solutions that don't require any penetrations for the racking. Obviously every installation is different and what works for one installation won't for another.
 
Not exactly disagreeing, but how do you know that?

Um, you can take panels off temporarily to address roof leaks. Also, properly flashed penetrations should not be very reliant on caulking, if at all.

True, to a point, but solar systems will require periodic overhaul or complete replacement anyway, and thankfully roofs last longer than solar systems. So when it's time to replace the roof, it will just make sense to overhaul the solar system at the same time (or remove it and sell the materials, depending on your financial situation). In the future, one can imagine solar systems being overhauled every 20 years and the roof being redone every 40 years. In this sense, the only thing way it will be 'more costly' is if one fails to coordinate the two things.

Yes, it's stupid to put a solar system on a roof that is known to be within 10 years of the end of its life, but the solar industry is not encouraging people to be stupid that way. I've installed a number of systems on brand new roofs where the customer had the foresight to see that problem.

That penetrations need maintenace? That is my personal experience, booth in New England - milder and wintery climate and on the Midwest, blazing hot and hurricaney.

Where the solar systems make the most sense - most and highly available sunshine, the same also effects the roof life. (Talking about asphalt-shingles.) Realistically a 30 year roof might lasts 15.
 
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