working in pieces

System

A few weeks ago a picked up a kyocera 200w panel for $200. I took the battery and inverter out of my boat and created a 12v system that has flawlessly been powering my xmas lights for the the whole and three in the house. The lights are coming down in another week so I need to move forward. Initially I was going to get the outback inverter and another 120w panel and a few deep cycle batteries so I have a back up power system. As I have been reading through the messages on this forum, I want to build a complete system for the house. I need to do this in pieces especially since I recently took a bunch of equity out of my home so I don't have that cash available.

The question is... I have a usual monthly surplus of $700-1800 per month - In know that's not much but it's what I have to work with. I want to build a grid tie system that can also have a battery bank in the case of blackouts or disaster. The question is where to start? Do I start by saving for the inverter or by buying a panel or two per month. I figure I'll need 22x165 Mitsubishi panels to cover my peak expenses in the summer. (I live in Phoenix) Is there harm other than to the pocket book with having too many panels? I seems that I can fit 38+ panels on my roof.

niel

Re: working in pieces

congratulations on getting that deal on the kc200, but i'll advise against mixing the kc120 or similarly rated pv with the kc200. the vmps should be similar or you waste the voltage difference between them. also know that you need an mx60 controller to downconvert the odd voltage of that pv(kc200) to 12v. the vmp is 26.3v for that pv so that's too low to be used for a 24v system and too high for most controllers to handle for 12v operation. the purpose of the pv and others similar to it was to series many together for a batteryless gridtie system.
as to your proposed piecemeal system it can be done with careful planning. the only drawback to it is you will have to have the battery system in place for the end goal system as adding batteries as you go isn't advisable. you have to also decide if you wish the pvs to operate at higher voltage by placing them in series to overcome some of the voltage drop losses. another concideration is the battery voltage of the system. having that much pv power as you propose into 12v batteries all paralleled can present its problems and some losses here too due to voltage drops so a higher battery voltage may also be advisable.
you need to wire everything to handle the full future system, with all that's missing is some pvs and possibly another controller or 2 depending on the pv inputted voltage to the controller(s) and outputted voltages for the battery system voltage picked. the missing charge power in the meantime has to be made up for by a battery charger. some of the larger inverters (the better sinewave types) have built-in chargers. the grid will charge the batteries the rest of the way in other words.
the only other advice i can think of right now would be to make sure you don't undersize your wires, get a battery temperature sensor for the controller(s), and for your battery bank in your home operating at its best efficiency and safety would be to use agm type batteries. it will take some time to save for the initial system. to help in this effort and to possibly reduce the needed number of pvs is the use of conservation. energy saving appliances and the use of compact flourescents can reduce your monthly electric bill that could freeup more money for the effort, but more importantly lower what you may need to have in the final system.

quoted from you "The question is... I have a usual monthly surplus of $700-1800 per month - In know that's not much but it's what I have to work with."

all i can say is people nowadays do have a strange idea of what "not much" is.

crewzer

Re: working in pieces

Jazzharper,

Now there’s a big jump!

The question is where to start?

I would suggest that the place to start is by looking for ways to reduce energy consumption. The basic idea is that it’s usually cheaper to invest in energy-efficient loads and appliances and a “smaller” PV system than it is to just go out and buy a PV system that’s large enough to meet “standard” needs.

Examples of things to do are to install compact fluorescent lamps (CFLs; $10 for a six-pak at Home Depot), to buy a new Energy-Star rated fridge (<500 kWh/yr is easily done), to buy a new high-efficiency (HE) front loader washing machine (saves on water and energy required to heat the water), and maybe even a new dishwasher (which is used in the “air-dry” mode). A high-efficiency A/C unit might be worthwhile as well.

Another consideration would be to install a solar water preheater on your house. These things are pretty efficient (~60%, I think), and one or two of ‘em would make a big dent in your water heating bill.

You’ve already started by estimating an array size based on your peak summer needs. Another grid-tie approach is to figure your average monthly need and size your array accordingly. The idea is to buy from the grid when your production is low and/or demand high, and balance this out by selling to the grid when your production is high and/or demand low.

A moduler system approach is technically OK, especially with a grid-intertie system. You’d probably want to start with a “small” nominal 60 V array, an OutBack MX60 controller, a pair of OutBack GVFX3648 inverters (“stacked” for 120/240 VAC operation), an OutBack Hub and Mate for integrating the controller and the inverters, and a 48 V battery bank. You could add additional 60 V subarrays as funding permits. The folks at Northern Arizona Wind and Sun, this site’s sponsors located in Flagstaff, can help you figure all of this out.

Here’s what an OutBack-based system might look like: http://www.outbackpower.com/pdfs_wiring_diagrams/ps2ac-dcsystem48vGT.pdf

Another place to start is to learn about and understand all of the local, state and federal incentives available for designing, financing, buying, installing and/or operating PV systems (electric and/or hot water) and energy efficient appliances for your home. These programs will GREATLY reduce your net out-of-pocket expense.

See: http://www.dsireusa.org/ I suspect NAWS may be able to offer suggestions on these incentives and programs.

Some utilities offer novel financing programs. For example, the Los Angeles Department of Water and Power (DWP) financed my high-efficiency A/C and heat pump conversion in my home in 1989. Here is a summary of the then loan terms:

1) DWP conducted an energy survey of my home to prequalify our application
2) I needed three bids from city-approved contractors
3) DWP lent me 100% of the purchase and installation cost (paid directly to selected contractor)
4) Zero money down and 0% interest for 10 years ($4,800 job cost was $40/month)

Pretty sweet, eh?

Sound like you’re going to have LOTS of fun!

HTH, and have a GREAT holiday and New Year!
Jim / crewzer

BB.

Re: working in pieces

Several Suggestions (I see Jim has posted as I was writing this too--so mine is somewhat redundant),

First, work on conservation... Don't know how old your home is--but if it is an older home, insulation, ground sourced (or new) AC system, double pane vinyl windows, CF lights, turning off/switched power strips on unused loads (TV, Stereo, DVD, VCR, Sat. System, various wall warts, etc.), new energy star appliances, will return more for the buck than simply installing solar PV. Get a Kill-A-Watt meter from Wind-Sun (or others):

http://store.solar-electric.com/kiacpomome.html

Also, if you have electric or gas hot water/heating, solar thermal systems will also give more cost savings for the investment than Solar PV. Solar hot water panels are about $0.50 per watt (and 1/4 the roof area as solar PV), solar PV panels are about $5.00 per watt (installation, if you don't do it your self will be kind of expensive for either solar hot water or solar PV).

Even paying off the extra home loans (and CC debt) is a better investment than full solar PV (at this point in time--anyway).

After you have done the above (I did all of the above except the solar hot water/space heating) before I installed a 3kW (peak) grid tied solar PV system. I choose solar PV over solar hot water because of my concerns with maintenance of solar hot water and the fear of what California will do next with my electric rates (first they gave us the blackouts, now they are poised to tax the heck out of our power).

Fortunately, I live in a pretty temperate climate (don't have AC, conservation has got my electric usage down to ~200-300 kWhr/month, and my last natural gas bill was $54 for heating, hot water, and cooking. My solar PV placement is less than ideal but I still generate way more than I use right now (looking for the plug-in hybrid in the next year or three).

In reality, I would have been better installing solar hot water heating (for domestic hot water) as our two kids love to take long/hot showers after swim practice in terms of money spent--but it turned out OK because I got a great electric pricing plan from my utility--which is now closed to new customers (hope I can keep it). Also, California was about to hit the 0.5% total power limit (yea, like 0.5% in fossil fuel reduction is going to save the planet) for net metered solar PV installations--so I wanted to get a solar PV system grandfathered in before the programed was closed (CA has since raised the limit to 1.5% in the last few months).

Anyway, you need to ask what it is you really want from solar PV... If it is the best investment for your money, and you have cheap and reliable utility connections, then a pure Grid Tied power system is the best bet. It is more efficient (you don't waste energy converting, charging batteries, and re-inverting back to AC), virtually zero maintenance (no battery watering/cleaning), less space (no battery building/closet), and you don't have to replace the batteries every 5-15 years.

If you want emergency power for the occasional power blackouts, then look at a generator and transfer switch--much cheaper and smaller. If you only need a little bit of power, get a small Honda eu2000i (1,000 and 3,000 watt versions are available too). They are very quiet, portable for other uses, and consume about 1/5 to 1/10 the amount of fuel as the typical Generac 5,000 watt ones do. If you have a well, it may still be worth getting the small Honda type for the house, and a cheap Generac for the well pump (run it only when you need water). If you need to power AC and/or other heavy loads, you may wish to get a standby generator system powered with natural gas or propane (but these will consume a surprising amount of fuel and money to run for days or weeks).

And, I would suggest that you save (or purchase) for installing a complete system at once. Purchasing additional solar PV panels of the same brand/model at a good price is over a 1-2 year period is difficult at this time (supply is variable, manufacturers change/improve over time, etc.). You need a minimum number of panels to power a Grid Tie inverter, and as you add panels, you will probably have to reconnect the existing string (series/parallel/series-parallel) as the string grows, re-inspect by building department, possibly update records with electric utility, etc.

You may wish to save for a "smallish" solar PV system (say $10,000 in one year), install the Grid Tied system (permits, utility notice, etc.) with a local installer--get an idea how it is all done, and then a year later install the next system yourself (if you want--basically just copy what was done for the first installation) and save 1/3 or more of the total system costs.

A pure Grid Tied system, as I have said, is going to give you the best price/performance (utility is my, almost free--$6/month, maintenance free, unlimited capacity battery bank), but will not supply you with emergency power. And today, unfortunately, the input voltage differences between the typical grid tie inverter (200-600 VDC) vs a solar charge controller (20-140 VDC) just don't map well together where you could put a, for example, a Xantrex GT 3kW inverter and a transfer switch to an Outback MX60 Solar Charger for emergency off-grid use. It is possible that you could add some extra wiring from the roof to a patch panel where you could disconnect the Xantrex, switch from one 360 VDC to three 120 VDC circuits, then patch to one or more MX60's (depending on battery/power requirements)--but this would only be for the most die-hard solar guy. I thought about doing this--but decided that it was cheaper and easier to get a small generator and store/siphon some gasoline for the (so far) rare lost power emergency--plus I have the generator and gasoline available if I need to bug-out (in my area, earthquakes are biggest natural disaster risk and a collapsed home with a roof of broken solar panels and area wide shutdown of natural gas colored my choices).

If you have unreliable power or want/need to live off-grid, then a solar PV system with batteries is a good way to go--but it is hard to put one together a $1,000 at a time. As Niel already said, you don't really want to add a battery a month as the new batteries will age quickly and, in the end, will probably need to be replaced when the oldest batteries in the string begin to fail.

Also, getting the same brand/model of solar panels over a several year period, at a good price, is not guaranteed. As you install more panels and batteries into an existing system, you will have rewire (series/parallel/series-parallel) to keep the inverter input voltages/currents in-spec... Possible issues with building inspectors/utility company issues with constant addition of panels/batteries (insurance may be void if fire/damage is result of un-inspected/approved electrical work).

Other than playing experimenting with a small battery backed solar PV system, you would probably be best off to save your money and buy the entire system at once, or in "small system chunks" (and possibly using a loan for some of the cash required if the numbers make sense).

Good Luck and Have Fun!
-Bill

niel

Re: working in pieces

that's now 3 of us saying for you to conserve. good points have been brought up that i overlooked like the solar hot water and the choices between gridtie, battery backup with gridtie, or battery and no gridtie. we don't know what you're shooting for with it. also, pv availability could be a future issue for pvs as we've seen this happen so loans are an excellant idea to get it all now and with the current incentives along with federal tax incentives, you could probably swing a decent system now. we could be overly stating some things for anybody that figured down to the numbers of pvs needed may have accounted for all or some of what we've covered here. if not then good we helped you to some degree.

System2

Re: working in pieces

I should have mentioned the conservation. Everything is already CF, T5 or T8 lighting with the exception of the vanity lights above the bathroom mirrors. The house was built in 2003. My primary home is 5122 sq ft and my current utility bill is $207/mo (12 mo plan) I find that unacceptable. I have both AC and a swamp cooler for the summer. We only use the ac when we have to. Being originally from MN we have yet to turn on the heat other than to test it since I've owned the home.

I have no debt other than my mortgages and current holiday CC charges which are less than $800 (though the wife is out shopping at the moment), so I'll say the CC bill will be around $1500 by the time she gets home. Either way my debt load is small however my liquid is poor at the moment because I bought a new car and 48v PV powered golf cart (almost as much as a cheap honda. Damn!!!)

I want to install the system myself, I figure it may take a year or two but I won't be overwhelmed with the project either. I want to invest in solar because I don't like owning anybody anything. My wife also senses a major US disaster within the next few years. The kind of thing where power is scarce and food is limited.

By the end of next year I will have a small home built in MT that is completely self sufficient. I recently purchased just over 230 acres. The MT home will be our safe haven.

So now that you know more about me and my nutty life back to the question.... What should my first step be? Inverter that can tie into the grid and charge my battery bank or should I buy the battery bank or should I start buying up solar panels? or ?????

Thanks

BB.

Re: working in pieces

I would still look at conservation... Look at your kWatt*Hours on your power bill, and map that against something like:

http://rredc.nrel.gov/solar/pubs/redbook/
http://rredc.nrel.gov/solar/pubs/redbook/PDFs/AZ.PDF Arizona Solar Radiation Numbers

Let's guess that you get 20% more power than my array (SF CA) during the summer (better weather, more sun, perfect orientation). My 3 kW peak array (3,500 watt stc rated panels) generates, roughly 500 kWh/month, or about 600 kWhrs (+/-) for you (just a beginning point).

Assuming you have cheap power at $0.10/kWhr (big unknown for me--here in California, as you consume more power, your rates double and triple the baseline rate), and your summer bill is 2x your winter bill (AC vs no AC), $207/month would be:

kWhr/month in summer = $207*2/$0.10perkWhr = 4,140 kWhrs a month during summer...

The 4kWhrs/month is a guess on my part--but 2,000-3,500 kWhrs per month is roughly some of the numbers I have seen from others visiting here in Arizona. So, lets pick the 2,000 kWhrs/month as your target for solar.

Currently, solar panels are round $5.00 per watt (~$5.83 per watt based on PTC and Inverter deratings), a Xantrex GT 3.0 inverter is $2,000, and generic labor (including building permits, etc.) is another $3.50 per watt (based on my costs--your numbers may vary). So, it all adds up to about $10 per peak PTC watt installed... And for summer in your area, a guess would be that you will get about 600kWhrs/month for each 3kW $30,000 peak system, or about 20 kWhrs/month (summer) for every $1,000 you spend.

For 2,000 kWhrs/month (in summer), you would need to spend about $100,000. If you do the work yourself (shop around better than I), you can maybe do it for 40% less--or $60,000 just to do grid tie to zero out your energy usage during the summer.

Now, if you want 3 days of bad weather battery backup, you will need about:

(2,000kW/Month) / (30 days per month) * 3 days *1/50% battery reserve (for good life)= 400 kWhrs of batteries.

From:

http://store.solar-electric.com/cr225am6vode.html (picking a "golf cart type battery" just so you have a reference in size--you would probably pick something else for a large system:

225 amp*hour * 6 volts = 1.35kWhr per battery

400 kWhr for 3 day battery bank / 1.35 kWhrs per battery =~ 296 batteries

At $650/eight batteries =~ $24,000 in batteries... and you will need to replace them every 3-15 years (better batteries and maintenance, more years)...

For a large pure sine wave inverter than can manage your AC load--Throw in a couple 3kW inverters for $1,500 each=$3,000.

For a solar charger that can manage 10 kW PTC peak of solar power at 48 vdc, you would need at least 4x MX60 charge controllers at $500 each for $2,000 (but you could get rid of the Grid Tied Inverter in a battery design)...

Now, because you are on battery, solar chargers, and AC inverters, you probably are going to loose 20-40% of your power (over and above a grid tied system) to additional conversion and battery charging losses--that means that the number of solar panels, batteries, solar charge controllers, will need to be 1.25-1.66 times larger than an equivalent Grid Tied rated only system.

So, if you are planning on powering your entire home like you do today--but using only solar, you are looking at somewhere around $50-$150,000 for a solar system (do it your self, to fully installed)... And that was not accounting for any extras like wiring, storage building, special racks, etc.)...

Back to the original question, what amount of power (in kWhrs per day/month/season or something similar), how much battery storage, and is this intended to supply normal power, or for use during a disaster--and how long a disaster are we talking about (days, weeks, years)... I am guessing that you would want to plan on living on a 100 kWhrs / month in a disaster type situation...

Perhaps, you should at about a 600-1,200 watt STC panel system with 3 days of battery power (20 kWhrs of battery power or about 14 golf cart sized batteries... The system is much more manageable in size (only 3-6 200 watt panels), would supply enough for a few lights, small fan, radio and occasional washing/water pumping, and could be moved from your current home to MT as a starter/test system there. And you could do the whole thing after 1 year of savings. After you have experimented with the system (logged your daily generation and consumption), you can then decide where you want to go from there.

Even designing a "small" 100 kWhr/month system, there are still many choices to make--size/brand of solar panels, which solar controller, which batteries (wet/AGM) and what size, which inverter, wiring/fusing options, lighting protection, tracking or fixed solar panels, generator backup or not (and battery charger if needed)--it is still a great learning tool and will allow you to add optional items (like a small gas/diesel/nat-gas/propane manual or autostart generator, do you want a grid-tied inverter that can sell excess power or not, etc.).

The system will be small enough that you could move it and/or make some spending mistakes without greatly angering your wife and such. And after several years of working/tuning such a system, you too will be a solar guru (not claiming that I am--by the way)... And you can decide how you would like to proceed down the line with much more knowledge and experience.

Also, check into your local solar power incentives... Some may only be available for grid tied power, professional installation, or other such rules. A small independent battery/inverter system is likely not to qualify for most rebates.

Have Fun and Merry Christmas!
-Bill

niel

Re: working in pieces

montana?
hmmm. now that makes me ask, is it for montana in the near future or arizona forever? i'll guess that you wish to have this in montana as you state you are saving for or towards it. the bulk of this would be the pv costs with batteries probably second. see your needs may change in another state (this affects state rebates too) and the insolation certainly would. i'll give you another option to look into with wind power. you do have some time to get this stuff so just start saving and sort it out as you go. plenty of reading here and you could also download a free issue of home power magazine too.

crewzer

Re: working in pieces

(I live in Phoenix)… My primary home is 5122 sq ft and my current utility bill is $207/mo (12 mo plan)… I want to build a complete system for the house… I want to build a grid tie system that can also have a battery bank in the case of blackouts or disaster… I want to install the system myself, I figure it may take a year or two but I won't be overwhelmed with the project either… What should my first step be? Inverter that can tie into the grid and charge my battery bank or should I buy the battery bank or should I start buying up solar panels? or ??

Jazzharper.

Moving on past conservation and financing options, I’d suggest that your first step should be to more fully understand your goals and requirements. For example, in addition to grid-tie and battery back up, do you want to completely offset your average monthly power bill, or you just want to reduce it?

It’s also important to understand the jargon. “Grid tie” generally means that the system will interact with the electric utility. The system will typically “sell” to the grid during the day and “buy” from the grid at night, somewhat treating the grid like a very large “battery”.

Assuming $0.10/kWh, your ~$207/month power bill indicates your annual energy use is ~25,000 kWh. The PV Watts model for your location indicates that you’ll need a PV array (fixed tilt at latitude, south-facing) rated at ~15.5 kW to offset that consumption. That would be 94 of the 165 W PV modules.

The combination of grid-tie and battery backup reduces your options to grid-tie inverters from just two manufacturers: Xantrex (the SW and SW Plus inverters) and OutBack. I know the OutBack equipment a bit better, so I’ll use it for an example.

A “stacked” pair of OutBack GVFX 3648 inverters could tie to your 120/240 VAC main breaker panel. These inverter automatically disconnect from the grid in the event of a utility failure, but they will draw energy from the batteries to power the house loads. In fact, they won’t work without batteries. The pair could supply up to ~7200 W to your house and/or the grid. A pair of MX60 controllers and 40 Mitsubishi 165 PV modules (four modules per series string, 10 strings in parallel, 6600 W STC total) could be connected to the inverter pair.

The HW installation inside your home would look something like this: http://www.outbackpower.com/Flex500.htm

More info on specifying large PV arrays with the MX60: http://www.outbackpower.com/forum/viewtopic.php?t=767

(Added on edit: Constant downstream loads would be limited to 7200 W max, regardless of whether the inverters are running from the batteries or in "pass-thru" mode from the grid. Other "non-essential" loads would have to be powered directly from the main AC breaker panel and bypass the inverters' outputs.)

A 48 V AGM battery bank rated at 1,000 Ah would require 16 size 8D batteries. The total nominal energy capacity would be 48 kWh. Reducing daily energy needs to the "essentials", the 6,600 W array and the 48 kWh battery bank would get you through almost indefinitely. For example, I'm planning to start build an off-grid home in Wyoming next year. My present design includes an array rated @ ~3,000 W STC and a 48 V x 1,000 Ah (48 kWh) battery bank to meet all of our energy requirements year 'round, including at least three days of autonomy (no Sun during bad weather).

A system of this size would offset ~ 43% of your present utility bill. This might be an incentive for further conservation measures. Such a system could be modular in deployment. Staging might look like this:

1) Buy and install the inverters and related hardware (system not operational)
2) Buy and install the batteries (inverters will charge the batteries; limited backup capability)
3) Buy and install one MX60 controller and four Mitsubishi 165 W PV modules (at some point after this, the system should be selling power back to the grid and you should see your utility bill start to drop)
4) Progressively buy and install four more series-strings of four PV modules per string
5) Buy and install another MX60 controller and four more 165 W PV modules
6) Progressively buy and install another four series-strings of four PV modules per string

Finally, you may want to look into a combination of a grid-tie system and time-of-use (TOU) metering from your utility. By using your grid-tie system to sell power to the grid during the day ("peak" rate hours) and then buy back at night ("off peak" rate hours), you may be able to substantially reduce your electric utility bill without having a massive PV system.

HTH,
Jim / crewzer

System2

Re: working in pieces

I want a grid tie with battery backup system for my primary home in AZ. I will becoming into some money early next year and I have three other homes in MN & IL for sale that should be sold. The money for those transactions are ear marked for the MT property. Living off the grid is a new thing to me but something my wife has always wanted. I've always wanted a bunch of land for a horses or simply to run around naked (scarcasm). My wife wants the MT property to be completely off the grid and we plan to use it as a rufuge from life, AZ and if disaster strikes. In the mean time, none of this is nothing but a pipe dream until next year. I'm around enough in AZ that I want to put up a solar array. If y'all think waiting til I have the cash in hand then I suppose I'll have to wait a few months. I really wanted to do this chucks because I'm terrible at saving money and I'd end up buy more crap like a boat or another cabin or something and I don't need anymore of that stuff...

niel

Re: working in pieces

the particulars of the sources of income are not needed by us as you could have just kept it to you'll get a sum later and if you wanted you could have kept it to from the sale of property if you wanted to tell us. in any case try to buy the stuff before the end of 2007 to take advantage of the federal incentives. if you wish to calculate for both az and montana that will be 2 seperate homes with full blown systems and will run a pretty penny for both. do know you don't have to rush into it to the point that it must all be be in a few months although having it in place to take advantage of the summer sun would be nice for you. with power requirements as jim calculated for your needs the odds are you will be supplementing your power requirements with solar.
you could also add a wind generator into the mix if it presents itself as feasable. wind and sun is a nice marriage of power sources as when there's storms which produce wind there's no sun. mind you that no matter what you will have times of no power production. there is also another power source some people have access to and that's hydropower. no you don't need big dams and such as it is smaller in scale, but a good differencial in height between the source of the water and the hydro generator is needed and is usually done by a pipe of around a few inches (give or take depending on circumstances) in diameter to deliver the water.
all of this can be considered into your final system and i guess jim came right out and said it that you need to know what you want and to do that some knowledge will be needed by you on the subjects for you to make your decisions. we don't make the decisions for you, but only our opinions are presented to you. with the power levels you are saying you want/need i concur about 60v pv system voltage with a 48v battery bank system voltage. there will be wire gauge calculations, mounts to consider for the pvs, and fuse/breaker box systems to be installed. it is quite involved and to a great degree must be engineered to all work together and there are also safety issues to consider with inspections.