The real cost of solar power?

[Strygaldwir]

First 10 years, full warrenty. After that, prorated.

[sluissa]

I decided to do a bit of research on my own and found this site:

http://www.csudh.edu/oliver/smt310-h.../pvpayback.htm


Basically a study done way back in 1989 shows that solar cells can in fact produce the energy put into them in a reasonable amount of time. If you don't feel like reading the article, it basically says that most cells can pay back their energy costs in somewhere between 3 and 7 years.

Now, it's 2006, we can only assume that solar cells have gotten more efficient even since the writing of the article in 1997. So most people should within or below that range as far as energy repayment goes if they're using relatively recent cells. Given that nobody(at least to my knowledge) has found the true maximum lifespan of a solar cell(barring outside breakage or damage from saltwater or the like), it seems a dubious claim that they could NEVER pay back the energy invested in them.

even if this claim was off by 100%, and it took 14 years to pay back the energy costs, some solar cells have warranties up to and past 20 years. It just seems to me that the energy would be paid back in that amount of time.

[GordMay]

It should be noted that he author of the cited article (Richard Corkish), also cautions:
”... However, it should be noted that the above payback periods [sic: at worst, of the order of six to seven years and possibly less than three years] assume that the modules are always operated at their maximum power points [5], as with a maximum power point tracker. It is also assumed that no photovoltaic power is wasted or dumped, as would sometimes occur in many stand-alone systems, such as those using battery storage ...”

See another analysis:
Can solar sources meet Australia’s electricity and liquid fuel demand? ~ by Ted Trainer (University of N.S.W.)
Goto: http://socialwork.arts.unsw.edu.au/t...arSources.html

And some additional references linked at:
Energy Leverage Of Photovoltaics
In an argument between economics and thermodynamics, thermodynamics wins.
Numerous studies have been made to compare the energy that it takes to make photovoltaic solar cells versus the amount of energy that they produce over time. For example:
Goto: http://www.ecotopia.com/apollo2/pvlever.htm

[hellosailor]

"produce the energy put into them in a reasonable amount of time."
That's not unique to solars. After all, most utilities took 40 years (US-IRS long term depreciation schedule) to write off new power plants. And sometimes paid back the construction bonds in less time.<G>

It's the "$2k worth of solar to produce 32A per hour" that disenthuses me. Compared to a nice quiet tiny Honda genset producing twice the power rate at half the cost up front, burning a buck an hour in fuel and using a lot less deck space...That's a lot of tradeoffs. (Or an easy 4x as much power from a diesel genset, or using a heavier alternator to load up the main engine, which should be able to do something like 500A for an hour on a litre of diesel. Which, yes, would be excessive for normal battery banks.<G>)

Nice that solar means not having to lug fuel jugs or shop for fuel, to be sure. Just disappointing that "no moving parts" still REALLY costs that much.

Growing sugar cane on the taffrail & making ethanol, anyone?<G>

[Jentine]

I cannot understand how a generator is a better buy. $1000 for a 2kW generator, fuel, a one or two year life span (when run daily in a salt environment) maintenance and repairs compared against $2000 investment for 25 years. The math escapes me.

[hellosailor]

Perhaps, because the $1000 2KW low-end Honda will put out 148A versus the 32A from $2000 worth of solar panels. And the cheaper 1kW Honda will still perform as well as $5000 worth of solar cells, without requiring the extra $4000 out of pocket up front. Considering how economical these are with fuel (and tiny gensets aren't economical in the bigger picture, they just represent the minimum up-front purchase outlay)...

$4000 left in the investment market can bring in $300-400 a year in interest, which can buy 100 gallons of gasoline, which allows that Honda genset to be run for several hours several times a week. Outproducing the solar panels *while* allowing the $4000 worth of capital to not be spent.

That's not meant as anything more than one point in a group of points (places) to be considered. Or maybe, you'd rather just deal with finding $300 a year for gasoline, and put the other $4000 saved into a nice life raft, instead of a solar array.

Now, *that's* a consideration.

Originally Posted by hellosailor

Perhaps, because the $1000 2KW low-end Honda will put out 148A versus the 32A from $2000 worth of solar panels. And the cheaper 1kW Honda will still perform as well as $5000 worth of solar cells, without requiring the extra $4000 out of pocket up front. Considering how economical these are with fuel (and tiny gensets aren't economical in the bigger picture, they just represent the minimum up-front purchase outlay)...

Hellosailor,

I don't buy your argument. If I spent $5000 on solar panals I would expect to buy something on the order of 1000 Watts of PV's. That would get me on the order of 3.6kW-hrs per day of electrical generation. To generate that with your 1000W Honda you would have to run it almost 4 hours per day. And that assumes you bought a 150AMP battery charger that can feed that 1000W continuously into your batterys.

If that is acceptable to you, please don't anchor anywhere near me!

My point is, be sure to compare like situations. A $5000 installation of PV's is a gold plated installation for a very high energy consumption boat, where as the 1000W portable generator you are comparing to is a bargin basement solution for a low energy consumption boat.

Neither approach is bad, they just aren't the same.

Bill

[hellosailor]

GreatKetch-
Your expectations apparently differ from Jentine's experience:
"four Kyocera solar panels - $1900; one solar controller - $119; "
"420 watts with the regulator set at 13.5 volts"

Which is one reason why I was looking for real world numbers, not just spec sheet claims. I've seen lots of solar panels rated at "### Watts at 20 volts" and in some cases, more than 20 volts. If they say 1000 watts at 20V, you can derate that claim to 750 Watts at 15 volts, and even less at 14.4 to 13.8 volts. Roughly 1/3 of the wattage in some claims, will never be seen in 12V systems.
And that's assuming perfect screaming sunlight all day every day.<G>

Hello HelloSailor...

I think your arithmatic is the same as mine, just expressed in a bit mudled fashion. My pricing estimate is about $5/ watt of nameplate PV capacity. You have to shop around for that kind of price, but it is out there.

Then I assume that 100 watts of labeled solar panel capacity is capable of generating about 30 Amp-hours per day at 12 Volts, or 360 watts-hours. Those are pretty standard numbers for expacted capacity in solar systems. Be sure you are following the difference between "watts" and "watt-hours".

And you are of course right, it is unlikely that all of the available solar power goes into the battery, but you can't put all 1000 watts of your generator into the battery for the same reasons. Your argument says that you expect to run the generator for a "several hours several times a week" I don't know what that means or how many amp-hours you expect out of it in the time.

Before I can really understand and accept your argument that your generator is cheaper than solar, you have to be more specific on the electrical needs of the boat you are putting forward as the hypothetical case.

[senormechanico]

Before the advent of 120 watt panels, we had (8) 53 watt Seimens solar panels on our boat which I had fashioned into a cockpit bimini. We had all the juice we ever needed for a ten cubic foot 12 volt coldplate refrigerator with a freezer (it made lots of ice and kept ice cream in Mexico) microwave, HAM radio which we used a LOT, inverter, 110 volt stereo system with CD changer, TV set, 2 vcr's, watermaker, 5 fans, radar, autopilot, etc etc.
While we cruised Mexico for 4 years, we NEVER had to run the engine for electricity. The boat's been sold and sailed back to Mexico and the panels are STILL running 100% 13 years later.

If you happened to see the mention by Richard Spindler about Grey Max in Latitude 38 last March, that's our old boat.

Steve B.

[Jentine]

410 watts of power per hour is much more than I use with all the systems operational including house systems and navigational systems. Would a generator that produces more power be more adventageous because it produces 110 amps more than is needed to run everything aboard. I hardly think so.
We should keep in mind the usage as it compares to the consumption. The batteries will accept just so much power/hour whether it is supplied from solar or generator or wind or water.
If the idea is to run air conditioning on the hook, you will need a generator. If the idea is to run all the other household systems, a generator is a noisy intrusion on your neighbors and a waste of money.

[ssullivan]

Um... I hate to disagree with people, but I regularly put 180 amps/hr (peak) right into my Trojan T-105's. Of course, this doesn't happen often, as the smart charger regulates the flow, but I could do it any time with my genset, all the while running my 120VAC fridge, which lasts 24 hours with holding plate system.

So... I have a 1 hr max genset run per day, using as much power as we would ever want - lights, tv, dvd, refrigeration, this computer, WiFi, etc.. etc... This costs $10/wk or so in diesel at $4.50/gal.

I don't want to get too political, but I should remind everyone that these "green" companies that make solar panels are no better than big oil or anyone else. They compromise value to achieve shareholder profits, just like every other company - some more so, since they are heavily influenced by VCs. The reason solar costs the same as a genset (over 10 years) is because that's the price the market will bear and the solar companies know this. They charge as much as they can get away with, just like every other company does with its products. Who is the competition? Oil. So they make sure your genset and your solar are the same price over a reasonable amount of time (10 yrs). And.. with the batts you go through using solar over that lifetime of "free" energy, the cost would be quite even... I assure you.

[Strygaldwir]

My variable cost of running my little generator was aproximately $2.50 per hour. (This does not include maintenance). The variable cost of running my solar panels is $0 per hour. How long will it take to recover the cost differential of the panels? It could take you a LONG time if your usage is low. But then again you might not need expensive panel either! Running the generator for 2-3 hours per day to meet demand is not uncommon. So, how many days would it take to recover the cost of panels from just the variable cost difference. For us, about 400 days. Your figures may vary. So, an ROI of less than 3 years is a good economic decision for us. Then of course there the other variables. Maintenance, cost differentials, depreciation differences, convience, noise, smell, weight, danger (Still don't like having gasoline aboard!) etc...

How much you need? how much you'll get out of them? They are all variables you'll have to play with. One thing that is probably sure, you're ROI on saving energy is probably better than any energy production method.

Oh, our battery bank is 750 amp hours. We have a 2.5kw xantrex inverter/charger. We were never able to put more than 60 amps into our battery while using the generator. typical was 45 amps during bulk/charge phase. The inverter specs say there is a reduction if your genset is less that 5 kw. But, we would run our watermaker, microwave, breadmaker during the time we were running the generator. We should be able to load the generator up to about 150 amps. But, there is an increase in fuel consumption when we do this also.

I have never heard anyone say "I am not happy with may solar panels"! I have heard lots of cursing of generators, wind generators and gensets! "Broke my blades", "too noisey", "burned out the diodes", "wore out the bearings in the water pump", "too smelly", "lightening burned out the controller board", "ran out of gas", "it overheats", "rebuilding was going to cost more than a new one! $10k!", "It was eating belts", "burned out my starter", "had to have the brushes replaced", etc.....


Coolest thing I saw was a trawler with wind generator and solar panels. I guess they didn't like the noise either.

Far winds,

Keith

Keith

[Strygaldwir]

Sean;

You said,
"And.. with the batts you go through using solar over that lifetime of "free" energy, the cost would be quite even... I assure you."

I don't understand this? Battery life is dependant on depth of discharge and number of those discharges. If you run the generator continously, and never removed charge from the battery, it make sense. But, aren't you getting a deeper discharge of the batteries if you're only running the genset once a day? So, I didn't factor battery cost in doing the comparison. I think with optimal charging/utilization and care you're still looking at replacing the batteries every 5 years or so.

You use 2.5 gallons of fuel a week for your genset! and it generates 150 amps per hour! Those numbers make the ROI for solar much less compelling than I found. $10 a week. It would take me 200 weeks or so to recover my investment with variable cost. How much did your genset cost?

I was considering a diesel motor connected to a generator, but I discarded the idea because of the weight (the DISADVANTAGE in a catamaran) and I don't have a place to put it. The portable, I set in my anchor locker when I am using it, store it in the sail locker when I am underway.

$10 buck, mumble, mumble, mumble...

[hellosailor]

Stryg, you've got to remember Sean is in northern waters, he'd be lucky to get 4-5 hours at full rated output on a winter day, and there will be times when he'd get near-zero output for three days running.

Once you get to a land where there are seasons <G> solar has some problems.