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More than intuitive.That's the kind of programming non-elegance/lack of logic I used to get crucified for. I once if statemented stuff to death early on as a college student learning to program (which education began, BTW, in 1966 with machine language and an IBM 1620 that's now, if not in some scrap heap, maybe in a museum somewhere), and later got rightly and properly criticized for the lack of elegance in my attempts at FORTRAN IV and COBAL programming in the '70's. Now, I mostly modify my approach for most of this PV stuff and let spreadsheet methods and tools ease my mental anguish, often at the expense of the art form of programming. I was an engineer, not a programmer. Now I'm retired.
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On getting the hourly output out of SAM to a spreadsheet, and not trying to be a wise ass, I used the export to excel tab from the SAM output and copied that to the pricing spreadsheet.
On the gory details for Excel, I found the "Excel for dummies" book a simple help. There's also a title: "Excel for engineers" that's a lot better, but assumes a bit of preexisting knowledge of Excel.
I appreciate your situation. Been there lots. Nothing can replace persistence.Comment
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Understood, and that's exactly what I did; I just asked in case there was another importation method I was overlooking which would simplify things.
Where are you finding the 2-4PM super off-peak adjustments for March and April? I don't see that referenced in page 8 of the proposed rates.Last edited by kb58; 09-25-2017, 07:51 PM.Comment
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Pages 25 - 26 (pdf pages 27 - 28)
CS6P-260P/SE3000 - http://tiny.cc/ed5ozxComment
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+1 Confirming.
Pages 25 - 26 (pdf pages 27 - 28)
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Anyone remember the old text-based computer game from the early 1980's called "Adventure?" - I wasted tons of hours on that in college. For some reason, finding SDGE facts reminds me of it, just how well they've hidden things. https://en.wikipedia.org/wiki/Colossal_Cave_Adventure
Anyway... the spreadsheet's complete enough that I'm playing around with panel orientation. You're correct, 220 az and 30 deg tilt is about right.YOU ARE IN A LITTLE MAZE OF TWISTING PASSAGES, ALL DIFFERENT.Last edited by kb58; 09-25-2017, 08:47 PM.Comment
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Did SAM's shading work out for you ? Also, don't be too surprised if the revenue doesn't change much +/- 15 deg. or so in azimuth or +/- 5 or 10 deg. on tilt.
On shading: Remember, trees grow. Other stuff mostly doesn't. I added 7 ft. to the height and 4 + 4 ft. to the width of the tree off to my SW. Can't take it down because it's on golf course property.Comment
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Yes, I manually entered the scanned yard data output by the Solar Shades app. Agree on the small effect of orientation; 5 degrees is tilt or azimuth changed the sample 1 kW panel output by about $1 a year(!)
The trees involved are already full-grown, at the stage where they get trimmed. Two will likely get topped further if this goes through.Comment
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So okay, now that I have everything in the spreadsheet, with shading modeled, and a 1kW "crash test dummy" generating $379 annually at 30 degree tilt at 220 deg azimuth, what's next? Is it as simple as dividing annual usage by the 1kW test array in order to come up with the actual number of panels?
One thing I keep thinking about is potential future usage increases. For example, when our gas hot water heater goes out, maybe I should get an electric one - or even better, one of the heat pump units. Then there's an EV very possibly in the future - just not now. I read how no one seems to recommend adding empty mounts so that additional panels can be added later. From what I read, "either do it all now or not at all." I think I understand the statement but don't think that applies to me since I'm fully prepared to do everything myself. For that reason I don't see how installing mounts for more panels but installing only a subset is a problem. Of course I'm getting ahead of myself. I still haven't figured out the ROI on the system (once I know the number of panels) to see if this thing's a go or not.Last edited by kb58; 09-26-2017, 06:43 PM.Comment
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More later, but for now, Do as you wish but the smart money does not use electricity to heat water unless it's absolutely necessary. Match the entropy of the fuel to the task. Electricity is a low entropy (high availability) form of energy. It takes a lot of other lower availability fuels like coal and nat. gas to make a high availability energy source like electricity. That's most of the reason it costs as much as it does. Nat. gas is a much cheaper, and better way to do dumb tasks like heating things - or making electricity. It takes about 2 1/2 times as much energy contained in fossil fuels to produce the same amount of energy contained in electricity, but that electrical energy is much more versatile. Use electricity for tasks that cannot be done any other way. Try running a computer on nat. gas. r a phone. Or house lighting. If you have nat. gas now, keep it and use it wherever possible, home heating, water heating cooking, clothes drying.
In the meantime, get your current loads figured out and your future loads estimated as best as possible. Then, sit down and be realistic about what you want out of life for the next 10-12 years and how electricity will fit those choices for the future. I mentioned realistic choices in a post of a couple days ago in a post to this thread. Everyone wants an EV, and everyone may wind up with one, but maybe not. Choices with an honest appraisal of self and the future are required. Bigger family ? Moving/new job in the future ? Some sober reflection is sometimes in order.
As for expansion: Expandable systems are often, and for a lot of reasons, easier to conceive of than bring to reality. Building SOME extra capacity up front is probably wise, but like expenses and lifestyle that usually expand to meet (or exceed) income, electricity usage will expand to meet or exceed PV system output. Larger than necessary systems are self fulfilling usage increasers. Get your loads and choices and any time shifting planned as best as possible, know that things will change and the unexpected will surely happen. Then take your best shot and don't oversize too much.
As for that statement about doing it all now not applying to you : It does.
As for how much of a bill or usage to offset ? Use process economics and life cycle costing methods that involve the time value of money. PV systems are characterized by relatively large up front costs that are (hopefully) recouped over time by future saving realized from lower electricity bills. A very oversimplified explanation: When the present value of the future savings equals the up front system cost (and the future cost of maintenance, insurance, taxes and any finance charges), the system is cost effective. Or, as a comparison of alternative analysis (a similar but different type of analysis), you'll need to decide (guess) which investment of a sum of money (the initial system cost) today, will yield the most value in the future. Will buying a PV system and savings in electric bills put you further ahead in, say, 12 years than taking that same amount and buying a high quality corp. bond ? Or investing in improving your home figuring you'll sell/move in 12 years for more becase of the improvements ? Or, whatever ? One version (of many) of solar process economics is to use or calc something called the Levelized Cost of Electricity, or LCOE analysis for short. Fortunately for you, being familiar with SAM as you are, that may be an easy way to start. See SAM and the additional information it contains for particulars about LCOE and other tools for financial choices.
If the choice is to get PV, the next decision is how big to make the system. As for how big to make a system, or how much of a bill to offset, that too is a financial choice. If the choice IS PV, then the goal of the exercise is to find the system size, using the time value of money tools to figure out what size system results in the lowest combination of NPV costs of present system initial expenditures, and future costs for purchased electricity and system maint. This is all the stuff of engineering economics I bet you learned as an undergrad EE student.
Usually, but not always, if done thoroughly and realistically, and if a case for PV can be justified, any resulting system size that yields the lowest life cycle cost is often one that does not offset an entire electric bill or 100 % of usage. It might feel god that you're sticking it to the POCO, but the goal is the most cost effective way to save money, not revenge. T.O.U. and time shifting complicate things a bit, especially when you consider that the T.O.U. times as well as rates will change in the future. But that's one example of many reasons why a lot of forethought is a necessary thing, even though it involves necessary guesswork, a lot of which will undoubtedly be wrong. Life's a bitch. Do your homework, take your best shot, and don't oversize too much.
If you choose the cost and process economics be damned approach:, To size a system to offset 100 % of your current (or any desired) annual cost, using current DR - SES rates and times, and the spreadsheet you just created, you will need some way to estimate you hourly usage. Either estimate that on your own or get current hourly (actually 15 minute ) usage from SDG & E. Plug those 8,760 hourly usage figures, or reduce the 15 minute data to 8,760 hourly values, and plug those into the spreadsheet you just created that has the 8,760 DR- SES hourly rates. Multiply the hourly usage by the corresponding hourly rate for an hourly charge. Sum the hourly charges for an annual bill. Finally, divide the annual bill $ amount by the revenue from a 1 STC kW system (that $379 figure) to get an estimated system size to offset 100 % of the bill.
If you choose a more accurate method of estimating system size based on economics, see the SAM references and brush up on engineering economics and process economics.
Note that, mostly because of weather variation, but some other things as well, the system size calc'd using the above method, or any method, will be over sized some years and undersized in other years, perhaps by 10% or mor in any particular year. After you get a size, run it through SAM and see what it pukes out for output. Adjust for panel size and inverter/string or micro/optimizer considerations.
For you: Before you go further, go to Barnes & Noble or Amazon and buy a copy of "Solar Power Your Home for Dummies" ~ $20. Then read it. After reading it, come back here and ask questions to fill in any questions the book either raises or you can't answer on your own. There is a slightly outdated version of the book free for download on the net. I think you're beyond that point. I suggest the hardcopy.
Some of the questions you may have:
Have you looked into inverter types yet, be they string micro inverters or optimizers. Given your shade, I'd suggest that string inverters may mot be the best choice, maybe optimizers ?
How about panel choices ?
Start looking for a PV vendor/installer.
Good luck.Comment
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Of course the other school of thought is that your equipment, be it PV, wind, hydro, geothermal, etc. makes electricity, not gas, so go electric when possible. I was first exposed to that by Chris Olsen, a full time all electric off-gridder that has had some interesting posts in this forum in the past.Comment
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Natural gas is usually cheaper and much more efficient for heat generation. Thus converting from natural gas to electric and trying to offset with solar has a much longer return on investment because of the difference in cost of the fuel as well as the cost of conversion.
LP and oil would be similar in the conversion costs but the fuel is not as cheap as natural gas.
Half steps would be more practical, like if you had a natural gas furnace and air conditioner that was old. You might upgrade the central air conditioner to more efficient heat hump unit that would get you electrical savings as well as provide some heat in winter with natural gas furnace taking the heavy heat lifting.OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNHComment
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Two somewhat separate concepts going on here. The most likely common one is financial. Simply put, given a choice, the most cost effective fuel that's available to perform the task is the one used. No brainer there.
Using LCOE type costing analysis, suppose grid electricity is available at an LCOE of, say, $0.15/kWh (= $43.95/MM BTU). And say the LCOE of PV is $0.18/kWh for this example. And, say the LCOE for available nat. gas is $1.20/therm, or $12.00/MM BTU when burned at 70 % efficiency (== $0.041/kWh equivalent LCOE cost).
The task is to heat water for domestic. .
Now, which fuel is the one to use if all three are available ? Well, based on a long term cost analysis using LCOE methods, and the method's assumptions used, looks like nat. gas is the no brainer choice. Even if a heat pump water heater operating with a seasonal and average C.O.P. .of, say, 3 will cost more than the nat. gas option, particularly when higher initial equipment costs of the heat pump are considered.
Those LCOE costs I used are for this example only, but I believe them to be representative of prices in a good part of the U.S. However, if some areas (the pacific NW for example) have very low electricity costs that are competitive or olower than gas costs, then electricity becomes the fuel of choice. Bottom line for a lot/most of the U.S.: Electricity usually costs more than nat. gas, usually by a lot, so that's the usual and more common default fuel of choice. In any case, people vote and choose with their wallet.
However, If electricity is not available, as in my case, then the choice in the above example becomes grid or PV, or most likely, until l can get a PV LCOE price down to <or = the grid LCOE price, a least LCOE mix of the two sources is the most cost effective choice, all that of course only and until the point where levelized, or life cycle costs of any and all conservation measures I take come up to the LCOE of the LCOE of the cheaper fuel, in this case, the grid electricity @ $0.15/kWh.
The other concept, and admittedly the that's almost never considered, is the idea of matching the requirements of the task to the quality of the tools (in this case fuels) available to do the task.
I can drive nails with a pipe wrench - not something usually done, but possible. A hammer is a better tool and more fit fir purpose. But I can't put a threaded nipple onto a piece of 2 " threaded pipe with a hammer.
I can use gold bars as paper weights. Lead bars work as well for that task.
Think of it: I can use electricity to power an information device that puts the world at my fingertips as I'm ding right now. That seems pretty powerful and somewhat amazing to me when I think about it.
Seems a gross mismatch to use the same amazing and very versatile source of energy to do something I can instead do simply by putting something in the sun and letting it heat up, i.e. heating water.
Point is, match the energy source quality that's available to the required task. Don't cut butter with a chain saw, or kill flies with a howitzer.
Electricity is a very high quality form of energy with respect to its versatility. That versatility comes at a price: It takes a larger quantity of energy of a higher entropy (say a fossil fuel burned to make steam to turn a turbine to turn a generator to make electricity) to create a smaller quantity of energy (the electricity produced by the generator) that has lower entropy. in that process, the lower entropy energy source created (the electricity) acquires a versatility to perform many more tasks than the fuel that made it. That's a good part of why the stuff costs so much relative to other fuel prices.
A way oversimplified example of the relative waste of using a low entropy ( = high quality) energy source rather than a higher entropy (= lower quality) energy source:
Suppose I live across the street from a power plant that makes electricity and feeds the grid by burning nat. gas to make the power. A big nat. gas pipeline feeds the plant. Say the plant operates at 40% efficiency == energy out/energy in. The gas company that feeds the power plant has a branch off the line from the power plant that goes through a meter before it reaches my home.
I can heat my domestic water with either electricity from the plant by using electric resistance elements, or nat. gas from the gas company used in a combustion process in my home. Costs aside for a minute, which method of heating makes more sense ?
BTW, I've got a lot of respect for Chris.
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