system design opinions

metalguy22
metalguy22 Registered Users Posts: 12
I’d appreciate any feedback on how compatible you guys see these components as being with each other and whether they would suit my purposes. This will be an off-grid system.

24 - Kyocera KD205GX-LPU, 205 Watt Panels
1 - Xantrex XW6048-120/240-60 Hybrid Inverter-Charger
2 - Xantrex XW MPPT 60 Amp Solar Charge Controllers running 4 strings of 3 panels each.
8 – 12V Concorde PVX-2580L AGM 260 Ah batteries (2 - 48v banks of 4)
1 - Midnite Solar MNPV12 Twelve Circuit Solar Array Combiner
Various combiners, cables, panel racks

I figuring on needing about 12kwh out of this system to run 1600 watts worth of lights and power tools, among other things, 8 hours a day. None of these items are critical to operate every day except office equipment. I currently use an average of 15kwh per day with no attempts at conservation.

I live in NE Nevada at 40 deg. lat at 6000 ft. elev. Very cold winters. Very hot summers.

Thanks.

Comments

  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: system design opinions

    Your second to last paragraph about conservation raises my eyebrows.

    It is always suggested that your cheapest energy dollar is that which is spent on conservation. Every dollar spent of conservation will save ~$5-10 in PV costs. Since you know how much you use, you might consider a Kill-a-watt meter to find all the loads that you can reduce, most especially phantom loads from things that are on all the time that don't need to be, such as power supplies.

    Next, if you have the grid currently available, my question would be, why do you wish to build a battery based system. A battery based system will ~double the cost per KWH of any given PV system. A battery based system will on balance put out net/net only about 50% of a similar off grid system. The rule of thumb is that a battery based system will run ~52% efficient net/net, while a grid tie can run in the 90s. Additonally, many rebates/tax credits etc that are available to grid tie systems may not be available for off grid.

    The rule of thumb I use, is take the name plate rating of your system, divide that by two to account for system looses including PV/charge controller/ basic battery charging efficiency/inverter loses etc. and multiply that number by the number of hours of GOOD sun you can expect (Seldom more than 4)

    So in your case, your 5kw of panels should give you 5000/2x4=10kwh/day on average. What you don't have is any built in for reserve. I would look to lower the loads first.

    As I have said many times (perhaps too many times) do your homework, read all you can, and avoid the single most expensive pitfall about PV,, that is "ready, fire, aim!"

    Couple of other thoughts. Most people over estimate the amount of power they get out of any given PV system. Most people also tend to underestimate their loads. These two issues lead to undersized/over used systems. To cover your ~12kwh of loading, you will need to generate ~25 kwh of power, pretty tough to do with 5 kw of Pv into a battery system.

    Good luck,

    Tony

    Ps Do you know any of the Morens in Elko?
  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    Re: system design opinions

    double the PV and battery's ( suggest using 6V so less parallel stings ), add a charge controller and it should work OK ... as you have it your kill the battery's in no time
  • metalguy22
    metalguy22 Registered Users Posts: 12
    Re: system design opinions

    "Your second to last paragraph about conservation raises my eyebrows. It is always suggested that your cheapest energy dollar is that which is spent on conservation."

    I didn't put that very well. What I meant was that I am only using 15kwh now so it should be an easy matter to cut my consumption drastically without much effort - which I would do before commissioning any PV system.

    As far as the off/on grid issues go I understand the general rules of thumb but the problem is Nevada. No State rebates. Utility rebates that are claimed but unfunded and not even taking applications any longer. Net-metering agreements that basically say they can change and do anything they please and you agree to let them - in writing - in advance. Many believe Nevada must still be the wild West but there are not many States that are so relentlessly increasing their regulations and taxes as Nevada. I just want out - not out of Nevada but the system. In any event I still get 30% Federal and a business deduction for the rest so it pencils out pretty well.

    Don't know any Morens personally but my wife works with a lady that is married to one of the Morens. Easy to do though as they are a huge old Elko family.

    "double the PV and battery's ( suggest using 6V so less parallel stings ), add a charge controller and it should work OK "

    I don't quite follow you. The batteries I speced result in only 2 parallel strings. Looking at Concords batteries their highest 6v amp hour is only 300 so I would need to parallel two strings to get 600 ah anyway wouldn't I? I would only get about an additional 50ah over the two 12v strings for almost another $1000. I see what you mean though about the overall increase to avoid maxing out all the time but like I said I didn't explain myself well. I intend to reduce my demand a good deal below 12 kwh per day and I can run a day or 2 without doing production work if necessary. I just need the office to run at all times and that doesn't require much load.

    That all said, does it look like these components might work together even if one doesn’t agree with my underlying usage assumptions or off grid bias?
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: system design opinions
    metalguy22 wrote: »
    "double the PV and battery's ( suggest using 6V so less parallel stings ), add a charge controller and it should work OK "

    The batteries should seldom be discharged below 50%. If you want to have power to run for a couple of cloudy days, you need a pretty big battery bank, or be prepared to fire up the generator.

    You need a charge controller to regulate the solar panels, charging the battery, and you need enough PV to charge the (Larger) battery bank.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: system design opinions

    Rebate or no rebate/tax credit or no tax credit, off grid PV cost ~twice as much per kwh as grid tie, and it is about 1/2 as efficient. What is your motivation to go off grid? If it is to save money, I think you are going to be disappointed. In realty it would probably pencil out close to 4 times as well with a grid tie,,, just my opinion.

    T
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: system design opinions

    Just to have some "real numbers" to go with your setup...

    The 600 Amp*Hours at 48 VDC for the battery bank is a strong recommendation for running the 6kW XW inverter. Xantrex marketing does recommend a lower minimum size battery bank.

    Using the PV Watt website to predict solar energy for Elko NV, assuming 4,920 Watts of solar panels, fixed array mounted at latitude;

    Derating Factor = 0.77 * 0.90 for AGM * 0.85 eff XW inverter = 0.59 overall off grid sys eff
    "Station Identification"
    "City:","Elko"
    "State:","Nevada"
    "Lat (deg N):", 40.83
    "Long (deg W):", 115.78
    "Elev (m): ", 1547
    "PV System Specifications"
    "DC Rating:"," 4.9 kW"
    "DC to AC Derate Factor:"," 0.590"
    "AC Rating:"," 2.9 kW"
    "Array Type: Fixed Tilt"
    "Array Tilt:"," 40.8"
    "Array Azimuth:","180.0"

    "Energy Specifications"
    "Cost of Electricity:"," 9.7 cents/kWh"

    "Results"
    "Month", "Solar Radiation (kWh/m^2/day)", "AC Energy (kWh)", "Energy Value ($)"
    1, 3.80, 348, 33.76
    2, 4.34, 350, 33.95
    3, 5.10, 447, 43.36
    4, 5.43, 446, 43.26
    5, 6.14, 508, 49.28
    6, 6.38, 490, 47.53
    7, 6.55, 504, 48.89
    8, 6.82, 530, 51.41
    9, 6.68, 527, 51.12
    10, 5.74, 480, 46.56
    11, 3.84, 322, 31.23
    12, 3.63, 328, 31.82
    "Year", 5.38, 5280, 512.16

    The third column is kWhrs per month and ranges from 322 to 530 kWhrs per month.

    Assume ~8 months a year running just off the panels give you 446 kWhrs a month for early spring:

    446kWhr per month / 30 days per month = 14.87 kWhr minimum per day for 8 months of the year

    322 kWhrs per month:

    322 kWhr per month / 30 days per month = 10.7 kWhr minimum per day for 4 months of the year

    So, you have ~4kWhrs per day to make up (genset, conservation) during the winter months (if you want 15 kWhrs per day average).

    You can use the Xantrex XW MPPT charge controller sizing tool when looking at number of panels per string (looks like 3 in series maximum if you get sub zero "F" weather). If you get very hot summers, 3 in series of that 205 Watt panel gets close to the battery bank voltage. You will need to compare against your actual min/max temperature ranges for your location.

    Hope that helps.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: system design opinions

    So just to illustrate my point using Bill's numbers.

    Assuming a 5 KW system that cost net/net $8 watt installed. (Just a guess) for a total cost of ~$40k. Less a 30% rebate leaves a net cost of ~ $28,000.

    This system would yield, (once again, Bill's numbers) ~ 512 kwh/yr at todays pric would be ~ $475 worth of electricity? Sounds like a ~50+ year pay off. (Not factoring in any increase in the price of energy). Factor in the replacement cost of the batteries and you get farther away from breaking even.

    Take the same 5 kw system might cost $5 watt or $25k, less the same federal rebate, leaving a net cost of $17,500 (Less any local or utility rebate). In simple numbers using the same PV watt calc that Bill uses, you find a gross KWH annual output of ~6939, at a cost of the same $.097/kwh= $673 worth of electricity. Still a +25 year pay off, but with utility rebates, it gets closer.(and at least is in the range of the lifetime of the hardware). Factor in long term increases in the cost of energy and it gets closer still.

    In my mind, spending net, spending almost double to get ~70% of performance doesn't make a lot of sense. (Not to mention the cost of battery replacement) To my thinking, the grid is the greatest asset that people have to make PV energy work. Unless you have some compelling reason not to use it, I would strongly suggest that you reconsider.

    I'll shut up now.

    Tony

    PS As always, watch my math, as it may always be suspect, and subject to dumb errors. I believe the point it correct however.
  • metalguy22
    metalguy22 Registered Users Posts: 12
    Re: system design opinions

    "Hope that helps."

    Certainly does. Looks like I am kind of right on the edge with the system I speced but I think with the conservation you guys have suggested is required to avoid an overly expensive system it just might do. It would be different if I absolutely could not function with a down day here and there but that is not the case so I believe I am in the ball park. What makes it work here is the huge number of sunny days we get. Almost never more than 2 days in a row of storms.

    "Unless you have some compelling reason not to use it, I would strongly suggest that you reconsider."

    I value you input and have thought this over some and will likely stick with off-grid. Other considerations besides the extremely uncooperative and unsupportive State and utilities are, costs of using a licensed electrician as opposed to doing it myself (I've wired homes before and have a good buddy licensed electrician), building permits and inspections I won’t need, reduced capital cost by shopping around (I've got it down to under $20k just by going through wind sun), not needing a PV installers license (home owners don't need one), and other things push it towards penciling out better. But in general you are correct that when it come to $$, grid-tie always will likely be cheaper than not.

    It is an interesting thing I have found after 40 years as a contractor that more often than not people do not look at cost as their #1 consideration. I manufacture ornamental metalwork and most of what I sell has cost wayyy down the list as a consideration. I am mostly just a cranky Libertarian who wants as little as possible to do with the system and the independence of off-grid is worth a lot of money to me. This might not make sense to some but it is a fact of business that one really has to be observant to not miss what a customer think is important. More often than not it is not what I would think is important.

    I appreciate all the help. Any other comments are also appreciated.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: system design opinions

    Check out threads started by Adas -- He is in Hawaii and has installed a couple of systems for his business--borrowing heavily on used equipment/batteries/surplus inverters/etc.

    He shows that it can be done.

    Regarding the whole government thing--watch that you don't stumble over some sort of homeowner's insurance requirements (fire/liability) over local code/inspection requirements if, God forbid, something happens.
    I am mostly just a cranky Libertarian who wants as little as possible to do with the system and the independence of off-grid is worth a lot of money to me.

    I can understand that...

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • jeffkruse
    jeffkruse Solar Expert Posts: 205 ✭✭✭
    Re: system design opinions

    In your second post you said " In any event I still get 30% Federal and a business deduction for the rest so it pencils out pretty well. "

    Is this still true if you do the install yourself?
  • metalguy22
    metalguy22 Registered Users Posts: 12
    Re: system design opinions
    jeffkruse wrote: »
    In your second post you said " In any event I still get 30% Federal and a business deduction for the rest so it pencils out pretty well. "

    Is this still true if you do the install yourself?

    I'll have to ask my accountant but I believe since the equipment purchase is just a cost of doing business and a purely business expense I believe I would be safe claiming it. Maybe not the labor but that might be handled in a way that would work out too. Interestingly the Feds seem to be pretty easy going on their part. My research shows that there are no requirements on the IRS Form to claim the credit as to what you use and who does the work. I'm thinking that perhaps the deduction would be the same. Probably should check though.
  • hillbilly
    hillbilly Solar Expert Posts: 334 ✭✭
    Re: system design opinions
    jeffkruse wrote: »
    In your second post you said " In any event I still get 30% Federal and a business deduction for the rest so it pencils out pretty well. "

    Is this still true if you do the install yourself?

    Well I did claim and receive the federal tax credit for our own system which I did the install on myself; unfortunately this was when there was still a $2000 cap. Also unfortunately because we had enough deductions/ low enough income that we didn't qualify for the full federal stimulus check that year (we got 50%). Wish I would have known... and could have held out and put the system in place this year...
    You may want to double check the specific legalities of this, but on our federal tax forms there were no real specifics regarding installation so I figured "don't ask, don't tell" right. They very well may be more stringent now, since this could be a lot more money being doled out (since removing the $2000 cap).
    YMMV
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: system design opinions

    Regarding claiming self labor as a cost on tax return for credits/deductions--Generally that is impossible because you did not pay yourself with cash/check in the first place.

    If , however, you choose to pay yourself $XX per hour and pay income and employment taxes--I believe that your labor is then deductible--But, the taxes you have to pay for employment probably swamp the tax deduction in most cases.

    -Bill "I don't even play a tax adviser on TV" B.
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: system design opinions

    Metalguy2,

    I absolutely agree that there are way more considerations that money, and certainly more than up front initial cost.


    I have always been a fan of using total life cycle cost (value?) as opposed to up front initial cost. This assumes that one can get access to capital (and factor in it's cost) to make a potentially more expensive up front investment for longer term value.

    My big concern is the battery cost over time. The battery you list is ~$600 each, times 12 is ~ $7200. If you get ten years, which might be stretch given the loading you are proposing, that would be ~$720 per year just for batteries, this to get ~$475 worth of electricity!

    I also agree that having independence/libertarianism etc is something that one can't quantify, but if it were me, ( and I understand that it isn't) I would build the system that gives me the most bang for the buck, long term, and then take the savings and invest in my own future in other ways.

    So, you will make your choices based on your needs, but at least you will know the consequences. Too many folks think that they can "stick it to the man" and cut loose from the grid and "enjoy free power" only to discover later that they have made an expensive mistake. You have your eyes open so,, good luck with your endeavor.

    Tony

    (And I really will shut up about this now,,, sorry)
  • metalguy22
    metalguy22 Registered Users Posts: 12
    Re: system design opinions

    "Tony

    (And I really will shut up about this now,,, sorry)"

    Please don't shut up. Lots of considerations. Don't want to miss anything. As for the batteries I got a price of $512 per w/shipping included and I believe I only need 8 (2 - 12v strings of four = 4x12=48v @260ahx2 strings= 520ah) batteries so I can get out for around $4100. Still you are right that anyone thinking they are going to make their own independent power system and have it be cheap in any sense are fooling themselves. One further consideration is that I have many tools, spare generators and materials laying about so my $20k cost estimate is unlikely to climb.

    All this is also difficult because of that big black cloud on the horizon of stability in the price of energy. I don't really believe it will be stable at all. When I quit the gold mines in 1999 gold was around $300 an ounce. Today it is pushing $1200. All this is pure hedging by people who know against the worst instability scenarios and the politics of carbon. If (when?) that worst comes I believe energy costs will skyrocket. That will make PV look much more attractive and PV component prices will climb like all other commodities have been. I don’t believe this is very far in the future. But even assuming I'm all wet here (entirely possible) I don't see this as so out of line on the pencil pushing as to be a losing proposition. Anyway, thanks for the input and encouragement.

    And... the tax and deduction issues are complex. As a further complication I am a corporation and as its President I am also an employee. That likely will make my labor deductible to the corporation. We’ll see.

    And... as hillbilly says the forms (I downloaded the '09 ones today) make no mention whatsoever of details about what goes into the system. They just ask for the bottom line price so I'm with him on don't ask, don't tell.

    Thanks
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: system design opinions

    Since you asked me not to shut up, I'll make one more point. Using your own comment about the horizon of energy pricing being somewhat cloudy.

    With battery based systems, you are in to a fixed energy cost. (The cost of PV plus the price of the batteries amortized over the life of the system. If the price of electricity goes up (or down) your costs net/net stay the same, except for any increase (or decrease) in battery costs over time.

    On the other hand, grid tie energy(depending on the local utility contract) comes at a fixed cost. Over time if (as we would expect) the price of that energy goes up, you net cost of energy goes DOWN. For example, right now we are calculating that your would make ~$475 worth of electricity. If the price of electricity in ten years is $.18 kwh, the value of your contribution is now $950, making YOUR electricity cheaper. You would actually have a much greater benefit if the price goes higher.

    Add in the trend for utilities to go with real time, time of day metering, it is not unreasonable to assume that in the not too distant future you will be able to sell your power during times of peak demand (at a time when coincidently your PV performs the best). You can then buy back power off peak at a cheaper price.

    There are people in certain areas who do this, and the pay off period of there Pv is then measured in months, not years. If you go battery based, you cannot benefit from this.

    Icarus
  • hillbilly
    hillbilly Solar Expert Posts: 334 ✭✭
    Re: system design opinions
    metalguy22 wrote: »
    All this is also difficult because of that big black cloud on the horizon of stability in the price of energy. I don't really believe it will be stable at all. When I quit the gold mines in 1999 gold was around $300 an ounce. Today it is pushing $1200. All this is pure hedging by people who know against the worst instability scenarios and the politics of carbon. If (when?) that worst comes I believe energy costs will skyrocket. That will make PV look much more attractive and PV component prices will climb like all other commodities have been. I don’t believe this is very far in the future.

    I think you make a pretty good point here; I think that all of the "ROI" figures and charts that are out there all make some pretty bold statements based on some degree of conjecture as to future energy costs. Everything from PV being a huge financial net loss on to glowing reports that "prove" you'll get filthy rich of a large PV array. None of us really know for sure what the numbers may look like in 15-20 years...
    I tend to agree with you that at some point energy costs will grow substantially, and I think it's highly doubtful that they will remain static or drop.
  • metalguy22
    metalguy22 Registered Users Posts: 12
    Re: system design opinions

    Icarus,

    I see your point that price increases in a sense don't matter to a grid-tie but aren’t you limited to just trading watt for watt? I don't quite get the idea that I would be further ahead as prices increase. Perhaps the difference is in the net-metering agreement with NVEnergy. They will offset your input with their output up to the limit of your consumption. Supply anything more than your consumption they just take it, thank you very much. So as I say, at best is one ever going to get better than break even from my utility?

    However, you have convinced me to sharpen the pencil a bit more and see how the added installation and equipment costs and hassles play off against my (slowly becoming clearer) plans. I'm in no rush now anyway. The temps here have been subzero for a couple weeks so the ground has frozen and it snowed major last night so installation will have to wait till next Spring. Plenty of time to plan now. I doubt though that I will let go of my prepper/survivalist tendencies and give up the battery backup even if I do go grid-tie. It's only money ;)

    I am a dedicated record keeper (you kind of have to be in business) so I will know exactly how this all costs out in the end. I’ll spreadsheet it out and let people know. It’s always good policy to give back info to forums.
  • metalguy22
    metalguy22 Registered Users Posts: 12
    Re: system design opinions

    "None of us really know for sure what the numbers may look like"

    Yes, it is pretty dicey these days to make even short term decisions. On one hand a terrorist attack on Saudi or Israel finally having had enough could lead to war and energy catastrophe. OTOH a change in the political climate could lead to vast quantities of cheap US gas and oil that could drive prices for conventional energy down just as drastically. OTOOH a major breakthrough in PV technology could produce energy so cheaply as to completely decentralize our entire energy grid. Challenging times out there and I suspect this is much of what drives my leanings towards personal energy independence and an off-grid system. I worked for some time in the nuclear industry as an engineer. At first we (engineers working in the field) thought it was THE answer. Then we decided it was not likely to ever be economical given the hazards. Now most of its drawbacks have been addressed with the newer generation nukes and they are making a comeback. It’s just really hard to nail down all these things in a manner that allows one to make informed decisions.

    Anyway, I've managed to totally drag my own topic off topic so now I'll shut up.
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: system design opinions

    I think the general consensus on the price of energy is that on balance, over the life span of a PV installation (25+- yrs) is going to go up. Even if huge quantities of natural gas comes on the market, the CO2 emission issue is going to be real, and ergo expensive. IF Pv all of a sudden gets a decimal point cheaper, the huge amount of energy demand is going to do nothing but go up keeping any decrease in Pv price off set by demand increases.

    I certainly empathize with producing power, plugging it into the grid, and not getting paid for it, but the same is essentially true in an off grid situation as well.

    If you design a net metered system so that on an annual basis it produces just as much as you use, so that your net bill is zero, every body is happy. (Figuratively anyway). This is fairly easy to do within a few percentage points, especially in the arid desert west where you are, with +300 days of sunshine.

    Now in an battery based off grid, first you are "giving away" ~20% of your power just for the mere fact that batteries take about 20% more power to charge than they can give back in load. This is simple battery physics and chemistry and little can be done to change it. Additionally you will "give away" some other smallish portion of your harvest to charge controller loses. (Loses that wouldn't be there in a grid tie system) But perhaps your biggest "give away is that it is almost impossible to design a battery based system that can use 100% of it's PV. The way that batteries charge forces the controller to ramp down the current as the batteries approach full charge. The difference between what your system CAN produce and what it DOES produce might be on the order of 25%. (If your batteries go to float too early in the day, power potential is wasted, if they don't go to float nearly ever, then battery life may be compromised.) That said, there are ways that you can use diversion loads to help harvest some of this excess energy, but it adds cost and complication.

    So in a good, net metered grid tie system you might give away a few percentages worth of power over the year, but you would have the security of being able to turn on a light 24/7-365. Not a bad trade if you ask me.

    With an optimally sized battery system, my GUESS is you might "give away" 30% of your harvest AND not have the grid to rely on.

    Anyway, I think this illustrates the real benefit of this forum. In the real world, it matters not to me whether or not you do one system or another, but the forum exists for you to get the benefit of many thoughts, many of which are useful. You can also benefit from people who have forgotten more about PV than most of us will ever know. (I am not one of those!) As such, you don't have to reinvent the wheel as you go forth with your system. Your best ally is reading and learning all you can, so that you indeed do avoid "Ready, Fire, Aim!

    Good luck, keep in touch, and by the way, welcome to the forum,

    T
  • tallgirl
    tallgirl Solar Expert Posts: 413 ✭✭
    Re: system design opinions
    icarus wrote: »
    There are people in certain areas who do this, and the pay off period of there Pv is then measured in months, not years. If you go battery based, you cannot benefit from this.

    That's not at all the case -- my system is battery based and I have considerable control over when I buy and when I sell.

    The problem is that most inverters and charge controllers have little to no intelligence. My solution was to create a product (this is back when I was still an engineer at IBM, but now I sell it and other RE hardware) that is able to forecast production and consumption, then control whether the grid was being used or not.

    In the longer run, battery based systems are going to be where it's at -- it's the only way to do "Demand Response" as well as "Load Following". Both of those are required for all the "Smart Grid" stuff that's going on. RE system owners who are able to participate in the "Smart Grid" are going to be able to get a better deal for power than RE system owners who are either "On" or "Off" based on when the sun is shining.
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: system design opinions

    TG,
    I am not arguing that battery based systems have a place (as you can see we are having a discussion on anther thread, and I will carry on the bulk of the argument there rather than duplicating it here). What I am arguing is that for a "most bang for the buck" a battery based system is way more expensive net/net than a pure grid tie.

    Tony

    PS Go over to this thread to read my other arguments http://forum.solar-electric.com/showthread.php?t=6515
  • metalguy22
    metalguy22 Registered Users Posts: 12
    Re: system design opinions

    "What I am arguing is that for a "most bang for the buck" a battery based system is way more expensive net/net than a pure grid tie."

    And you are correct in your solution to the problem *as you state it*. Most people are looking for the most bang for their PV buck. But I don’t think I am in the sense that you mean it. That doesn't mean I don't pencil things out it just means I believe you are stating the problem so narrowly that it just doesn't address what are the more critical issues I believe are confronting me/us.

    There is nothing about PV at this point that is anything other than an enormous transfer of money from one group to another to make something that on its own would have no chance in the competitive marketplace. If you want bang for your buck in a real world *unsubsidized* market there is little to recommend PV solar. I don’t believe that is sustainable. So the problem as I want to address it is how to I decrease my dependency on “the man” as you put it in a manner that is true to my views on the State and its place in our lives. One can believe this is a bunch of hooey and still understand that "most bang for the buck" as you define it is answering a question I am not asking.

    To address my concerns you would have to include the question, “What if your assumptions about a net-metering agreement are incorrect?' in your calculations. I don’t believe that the state of things vis watt for watt trading will remain the same over the life of a system. What happens when Nevada decides that instead of a watt-hour for watt-hour swap they will henceforth give you .90 watt-hour for your one watt-hour - or .8 - or .5? Just how long will they go on managing your power consumption for free when it is easily within their power (since they wrote it up that way) to charge you for it? My answer. As soon as the money they are being paid to do it now runs out.
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: system design opinions

    I think that you make a legitimate point about what happens if,,, for example if they change the net metering payout.

    I do think that one of the things that folks need to do, is to be proactive within their state and local governments to ensure that good public policy is established. I don't want this thread to turn into a push/pull about what good government is so I will let it go at that.

    You have your eyes open, and indeed you will make your informed choice.

    Tony
  • tallgirl
    tallgirl Solar Expert Posts: 413 ✭✭
    Re: system design opinions

    At some point in time the watt-for-watt schemes =are= going to be abandoned. Selling electricity is a money making venture for utilities and if more people "Go Renewable", at some point the utilities are going to make a valid case that there are unrecovered costs in net-metered schemes.

    Whether or not that means battery-backed PV is the silver bullet that gives customers choice, I don't know. One thing I do believe is that coordinated central monitoring will allow Distributed Renewable Generator (DRG) owners to act as a block and make better "deals" than the current approach -- which is hoping that public utility commissions and governmental bodies keep being nice to us.

    One thing I do predict happening sooner rather than later is DRG owners being assessed a "balancing energy" fee since we're not exactly making life better for the folks who shell out the money for balancing energy. And if the utilities that pay for that service aren't collecting money from us that can then be given to the folks providing the service, they will eventually make that case and that'll probably be the end of the free ride. The only thing that I think is going to save us when that happens is businesses like GridPoint, with GridPoint using our systems to either provide our own balancing energy / spinning reserves / demand response or selling services based on our systems to generate revenue to offset that expense. Either way, the pure "blast the watts onto the grid!" approach of pure grid-tie has the least flexibility -- at least in the current incarnation of inverters (and I know how to fix them, but I'm not saying, neener-neener!)