User talk:Hitssquad

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[edit] Minor edits and removing talk comments

Two things. I saw the unsigned comment at my user talk page, so I looked at your edit history a bit.

  1. It's considered very bad form to erase the content of you user talk page, since it looks like you're trying to hide discussion (I can dig up the guideline that says that if you need it). Archiving comments after they've accumulated a bit is a good idea, but not simple deletion.
  2. I notice you mark most of your edits as "minor edit", even though most of them are not. Even if you add a perfectly reasonable clarifying clause, if it is not simply a fix to a typo or formatting error, it should not be marked as minor. Doing so prevents people from seeing your edits if they view changes with "minor edit excluded".

Lulu of the Lotus-Eaters 03:45, 30 January 2006 (UTC)

Thank you. I appreciate the tips. I have now read the minor edit documentation. --hitssquad 07:49, 30 January 2006 (UTC)
No problem. I think there might be a setting in your preferences that controls whether "minor edit" is the default. I choose "no"... since it seems better to occasionally mark a minor edit as non-minor than to do the reverse. Welcome to WP. Lulu of the Lotus-Eaters 08:30, 30 January 2006 (UTC)

[edit] R&I

Yeah, it looks like there's some lack of agreement between style guides, though consistently using caps seems like the safest way to go. (thanks for fixing the article's usage) --Nectar 23:50, 31 January 2006 (UTC)


[edit] Solar Power

Hits -- We should probably get the discussion of Solar Power off of the Nuclear Power page. I hope this is the right way to communicate with you...

"I assume 45,833kwh/Wp is supposed to be 45,833kwh/kWp." Uh, yes, thanks.

Regarding electricity production rates... SolarWarriors system looks like a good comparable to my 2.4KWp system. Both were constructed by EcoEnergies, and Corrolitos is reasonably close to where I live in Redwood City. I did not find any reference to an estimate of 50kwh/day year round average production. The SolarWarriors sample graph for September showed well over 80kwh being produced on that day from about 11am to 3pm. If I crudely integrate over the graph, I come up with 140kwh for that day. Since the end of September is roughly the autumn solstice, it should roughly estimate an average day. And 140kwh per day is in the same ballpark as the value I gave (especially if they had tilted their array due south or slightly west to avoid morning fog).

You would proably be interested in [PG&E study]. The paper measured actual electric production for about 20 residential installations and meaasured an average of 1100kwh/year per KWp. (That's 3kwh/day/KWp versus EcoWarriors 50/36.7 == 1.36kwh/day/KWp versus my 4.19kwh/day/KWp.) The value that I suggested did assume relatively optimal fixed positioning of the modules. The best sites that PG&E observed were in the range that I gave, but included tracking systems. Note that my estimates are based on data obtained 5 years after the PG&E study. It is somewhat possible that in the intervening 5 years, modules have become better at generating electricity from relatively indirect lighting in the early afternoon and evening hours -- this would not change the Wp rating of the modules, but would change the kwh/KWp production ratings. But, of course, if I were you, I wouldn't buy that line of argument.  :-)

You can review [Rates] or, slightly better [Rates. Look at Residential E-7 Time-Of-Use rates.

Regarding the cost of turnkey -- Since I installed modules for $7.50 per Wp (not including rebates), it must be possible to install them for that price. I didn't use integrated roofing nor tract housing, so I didn't get to amortize the one-off design and construction costs. If you run your model at 3kwh/day/KWp and use a really high price of $7.50/Wp to install the panels, you would end up with a more realistic (but pessimistic) cost of $1/kwh.

On the other hand, you will want to include maintenance costs. I'm assuming (but not calculating into my profit/loss statements) that I will have to replace a $2,000 inverter in 10 years. I'm assuming that learning curves will keep the cost of that inverter at around $2,000 and will also increase the lifespan of the replacement inverter to last for the remaining 20 years. Additionally, I climb up on my easily accessible low-sloped roof a couple of times a year to squeejee my modules. There has to be some risk factor that I'll fall off the roof and break my neck, and my time spent squeejeeing is presumably worth something. (Of course, when I stand on top of my house, I tend to shout out to anyone walking by: "Hey, look at my bright shiny PV panels."  :-)

[The system will be worthless after 30 years. For my system, I'm going to have to replace the roof in 30 years, and the cost of taking off and putting back on the panels will be too high to justify -- especially since the new roofing material in 30 years will incorporate photovoltaics. Besides which, the performance of the system will slowly degrade over time. I'm also being somewhat optimistic that the system will really last for 30 years -- the warranty is only 20 years.]

I'm not sure I particularly believe your cash flow model. I don't understand what is happening on the payment side. You will pay about $430 for your stated amount of electricity the first year. You won't collect 5% interest compounded annually on that money over the next 29 years. You will pay $430 * 1.02 the second year, and not collect interest on that money.

When I run the model with a $18,000 capital investment and 3*30*2.4 kwh/month and a 5% after tax return on investment, the model still breaks even at $0.36/kwh current price of avoided electricity. Without solar, in the first year you would earn $900 in interest and pay out $933.12 for electricity. Chuck Simmons 21:12, 1 February 2006 (UTC)

I'm not sure I particularly believe your cash flow model. The money that we would have had to spend on electricity bills if we did not have the solar PV system would have an opportunity cost. I assumed a discount rate (borrower's cost) of 5%. Because of the cost of capital, money spent or saved or accumuated in early years is far more important than money spent/saved/accumuated in later years. (Deferring costs tends to save money.) This is principally why homepower is so expensive.
If I crudely integrate over the graph, I come up with 140kwh for that day. I crudely integrated also but made a mistake. Reintegrating just now, I get 140kwh (I did that independently by separately integrating the slopes and then adding together the results -- I did not work backwards from your 140kwh result). This page [1] says Solarwarrior's system "generates an average of about 5kW." I am not sure what that author means by that, but 5kW continuous would be 120kwh a day, which seems to jibe with our 140kwh for that near-soltice day in September, plus some rainy/foggy days thrown in for a realistic year-round average. That works out to 43,800kwh/year or 1193.46kwh/year/kWp or 2864.3kwh/year for our 2.4kWp system or 85,929.15kwh for our system over 30 years. That is 12/5 of my previous estimate, so my input figures would need to be adjusted by 12/5 -- and that should affect the results of the calulations by even more that 12/5. Normally, I use a rule of thumb of $1/kwh for the cost of solar homepower, not including insurance, maintenance, repairs, and decommissioning. Making a 12/5 adjustment in the system output should bring the results of my previous calculations more inline with my $1/kwh rule of thumb.
The output of the 2.4kWp system would continuously degrade over 30 years, so the output will not actually total 85,929.15kwh -- if output drops 1% per year, after 30 years the output will have dropped to 74% of its original value. The first year might produce 2,864kwh, but the final year might only produce 75% of that, or 2,148kwh. In sunnier climates, the output will drop more, so the more electricity you produce, the more potential you lose. The majority of the reduction in output comes in later years, though, so it would not cost as much as a continuous average reduction (say output drops to 80% at the point where the panels have been in use for 30 years -- that would not cost as much as would an immediate 10% drop, with no further degradation, when the panels are first installed) in output would (per my above point that early capital is far more important than late capital).
Perhaps the 30-year production total can be broken up into 5-year chunks so the capital cost of grid electricity (from the non-PV comparison scenario) can be more-accurately calculated. Or maybe I should do this on a spreadsheet. Roughly figuring for an 80,000kwh production total, a $.36/kwh grid-energy cost, and a 5% annually-compounding discount rate, the total grid-energy cost (the cost avoided by the 2.4kWp PV system) over 30 years would be $71,119.42, or $0.89/kwh. An $18,000 up-front-cost solar-PV system would cost $77,794.96 ($0.97/kwh, or -- if we assume a more realistic 70,000kwh total production to account for degradation -- $1.11/kwh) at the same 5% annually-compounding discount rate. The $2,000 repair cost at the 10- and 20- year marks would cost, with the 5% discount rate, an additional $5,306.60 + $3,257.79 = $8,564.39. $500/year of additional homeowner's insurance would cost $37,041.37 over 30 years at a 5% discount rate. Many insurance companies simply refuse to cover any damage that might be the fault of accessories attached to roofs.
When I run the model with a $18,000 capital investment and 3*30*2.4 kwh/month and a 5% after tax return on investment, the model still breaks even at $0.36/kwh current price of avoided electricity. Without solar, in the first year you would earn $900 in interest and pay out $933.12 for electricity. $18,000 would be $7.5/Wp. Homepower.com estimates $9/Wp for 2.1kw systems[2]. A $9/Wp cost would make a 2.4kw system cost $21,600. But even figuring an $18,000 turnkey-installed cost, the system will have a depreciation cost. 5% annual depreciation would be $900 for an $18,000 for the first year. One's property tax might also go up as a result of improving his property via the installation of a homepower system. Though, if the home is worth more, the homeowner might benefit via improved credit lines and improved resale value.
How did you derive those electricity rates? Looking around on the net, these seem pretty typical [3]:
Pacific Gas and Electric
Tier 1 - 12.6 cents/kWh
Tier 2 - 14.3 cents/kWh
Tier 3 - 19.4 cents/kWh
Tier 4 - 23.8 cents/kWh
Tier 5 - 25.8 cents/kWh
Southern California Edison
Tier 1 - 13.0 cents/kWh
Tier 2 - 15.2 cents/kWh
Tier 3 - 19.7 cents/kWh
Tier 4 - 23.6 cents/kWh
Tier 5 - 26.0 cents/kWh
San Diego Gas and Electric
Tier 1 - 13.4 cents/kWh
Tier 2 - 16.0 cents/kWh
Tier 3 - 16.9 cents/kWh
Tier 4 - 17.8 cents/kWh
Tier 5 - 19.4 cents/kWh --hitssquad 11:43, 2 February 2006 (UTC)

Also, please see [[4]] which gives 2004 prices for cells and modules. The modules are quoted at $3/Wp which is compatible with a turnkey installed system cost of $6/Wp. Chuck Simmons 22:06, 1 February 2006 (UTC)

I usually refer to Solarbuzz[5] for module prices. Average prices there are usually listed as being between $5/Wp and $6/Wp. The lows since Jan 2002 came in April and June 2004 at $4.96/Wp. The mean price for Jan. 2006 is $5.32/Wp, and the 10th percentile of the distribution is $4.50/Wp. The price trend right now is sloped upward. The $5.32/Wp January 2006 price is 5.56% higher than the $5.04 January 2005 price. At that rate of increase, $6/Wp would be reached by March 2008.
Many manufacturers exaggerate the output ratings. Some modules may degrade more-slowly than others. Some modules may operate cooler at higher radiation flux levels, and thus would be more efficient on hot summer days. It may pay to not go with the "lowest" price. These prices do not include the costs of shipping, handling, contractor's insurance and storage. If a contractor is building solar tract houses, he is going to have to pay for extra insurance and storage of the mass-purchased modules. Currently, the most-likely construction materials to break on a construction site are windows. Solar panels can be added as high breakage-risk items if contractors are going to start building solar-PV tract houses. --hitssquad 11:43, 2 February 2006 (UTC)
You can review [Rates] or, slightly better [Rates. Look at Residential E-7 Time-Of-Use rates. If you were talking about time-of-use metering, I believe one should be able to time-shift one's grid draw with a lead-acid battery bank for a fraction of the cost of a solar PV system. The most expensive lead-acid batteries only cost a few hundred dollars per kwh of capacity[6]. There are refurbished whole-house backup systems on eBay. --hitssquad 21:24, 2 February 2006 (UTC)
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