some newbie questions

dsc3507 · May 2010

I am looking at getting started with a grid tie system and have a couple of start-off questions.

I was thinking of starting at the 1Kw level with later plans to double or quadruple that.

I probably will be pole mounting since I have a slate roof.

I have been looking at inverters and it seems most have at least 150v DC input low end ranges. Looking at the 210W Kyocera panel if I used five in series for a 1 KW system it would not appear it is enough DC voltage for the inverters I see listed. How does one design around this and how do you expand in the future. I suppose if you had enough cells, say 20, you would series parallel them?

So I am looking for a little guidance on design of a starter 1 KW system with built-in expandability.

My PV's would be about 100 feet from my inside panel. Assuming 10A or maybe 20A in the future I suspect at last #10 cu wire would be in order for lowest loss. Might even go to #8. Would you typically run just two wires from the PV location with series connection of cells there? These wires would be in a buried conduit. Should more wires be run? What type of wire is acceptable? Can regular UF or multiple runs of THHN be used?

I have not found one good place to spell all this out. Perhaps someone can suggest a site or book that might help. I have a technical electrical/electronics background. I just need to understand the procedures associated with the use of PV solar power.

Thanks, Doug

Kamala · May 2010

Re: some newbie questions

dsc3507 wrote: »

Perhaps someone can suggest a site or book that might help.

As for sites, this one ( here) is the best I've found. As for books, none. But then, I haven't looked for any since I found this forum.

dsc3507 wrote: »

I have a technical electrical/electronics background. I just need to understand the procedures associated with the use of PV solar power.

Thanks, Doug

Not really that hard to understand. Ohm's law rules. One might benefit by thinking in terms of soures and sinks. Either of which may be voltage or current.

PV panels are current sources. Battery banks are voltage sources.

I still have difficutly describing/understanding sinks.

BB. · May 2010

Re: some newbie questions

dsc3507 wrote: »

I was thinking of starting at the 1Kw level with later plans to double or quadruple that.

For central GT Inverter installations--My own personal observation is that ~3kW is a good "step"... Hardware is relatively cheap at that point, and external services (building permits, power company approvals, contractors that come out to install system, etc.) seem to scale with size.

A 1,000 Watt system is pretty small. And the centralized GT inverters are more expensive ($$$/kW) than the larger versions.

Since Grid Tied systems are highly regulated--You are supposed to involve a licensed electrician, building inspector and the power company every time you add panels. So, you have to add their fixed per call costs over the small array wattage.

The new micro-inverters (like Enphase) and others, they do give you the ability of adding one inverter per panel. So--you could get down to adding 200 watts at a time. And you could pre-wire/pre-install mounting hardware, and just add a panel at a time (would require electrician/inspector/power company? I don't know the law--perhaps you could get a XXKW system pre-approved and add panels without--but I would doubt that).

Since the costs of the installation, labor, and inverters is probably 2/3'rds the costs of the entire job--just adding a few panels at a time may not spread out the cash costs as much as you would hope. Our host has a couple estimates of GT hardware costs at various system sizes...

I probably will be pole mounting since I have a slate roof.

Pole mounts can be pretty expensive (lots of concrete and steel). You might also look at a regular racked ground mount too if that works for your home.

I have been looking at inverters and it seems most have at least 150v DC input low end ranges. Looking at the 210W Kyocera panel if I used five in series for a 1 KW system it would not appear it is enough DC voltage for the inverters I see listed. How does one design around this and how do you expand in the future. I suppose if you had enough cells, say 20, you would series parallel them?

The typical GT inverter requires around 200-600 VDC range of panel voltage to function correctly... That sounds like a pretty wide spread, but by the time you take temperature and other issues (Voltage, open circuit, etc.) into account--system configuration issues become quite limiting to your options.

Yes, you end up having to juggle cost, panel sizes, inverter selections, power layout, etc. to end up with your system. Also, if you want to add panels later to an existing inverter (say you started with 1,500 watts and want to add another 1,500 watt parallel string later to a 3kW inverter)--you could be stuck with matching the panels you already have (new panels have to nearly match the specifications of existing panels--and brands/models/availability all very over time--some vendors seem to match others for Vmp ratings--and some seem to have their own non-standard standard). It can be a real mess.

So I am looking for a little guidance on design of a starter 1 KW system with built-in expandability.

What is your desire for the final system--All of the support wiring/electronics/home main panel/etc. have to be sized for that maximum amount... Although, you could add up to your home's main panel now--and do the panel upgrade later--Lots of variables.

My PV's would be about 100 feet from my inside panel. Assuming 10A or maybe 20A in the future I suspect at last #10 cu wire would be in order for lowest loss. Might even go to #8. Would you typically run just two wires from the PV location with series connection of cells there?

When you have more than two parallel strings of solar panels going to one GT Inverter--you need a combiner box (electrical box with fuses/breakers) to safely parallel more than two parallel panels in your array. There are standard boxes available.

It would be your choice--you can run a pair for each string back to your home, put the combiner box there (if needed) then to your GT inverter. Or, you could put the combiner box at the array, and run a heavier single pair of wires back to the home. Just do it based on cost and ease of installation.

These wires would be in a buried conduit. Should more wires be run? What type of wire is acceptable? Can regular UF or multiple runs of THHN be used?

Running a larger conduit--or even several conduits for AC / DC / other wires (burglar alarm, remote sensing / weather station / etc.) in one trench is almost always a good idea...

You will have to do the installation per the NEC (National Electric Code) or whatever code is required by your local authorities. Different sections may require different wire (exposed wiring, UV rated. Conduit on roof requires high temperature wire, wire running through conduit in ground requires wet rated wire, etc.--as I recall--I am not a code guy).

I have not found one good place to spell all this out. Perhaps someone can suggest a site or book that might help. I have a technical electrical/electronics background. I just need to understand the procedures associated with the use of PV solar power.

BB. wrote: »

Regarding Solar Books:

What's a Good Beginners Book?

-Bill

PS: Our host also has a Book they recommend:

Book - The New Solar Electric Home

And back to a fundamental recommendation that many of us always make here--Before you drop your first $ on solar RE power generation--Work on conservation first.

It is almost always cheaper to conserve a watt than to generate a watt... For an average home where nobody has really paid much attention to energy use, it is not unusual to cut upwards of 50% off their energy bill through conservation, insulation, skylights, energy star appliances, changing out from desktop computer servers left on 24x7 and going to laptops, adding switches to DVR's, Sat Boxes, Stereos, etc. which can have high standby loads, etc...

Also, if you have any large electric loads (electric stove, hot water, heating, old A/C system, etc.)... Look at converting to alternative fuels and replacing older energy hogs.

Get something to measure your loads---A kill-a-Watt meter is great for 120 VAC 15 amp plug-in loads. Look at the whole house monitoring equipment (like T.E.D. and others).

Then, after all of the conservation work is done, look at solar power.

-Bill

dsc3507 · May 2010

Re: some newbie questions

Bill,

Thanks for your informative response. It does make one think as there is no utopia in any of this.

I am a DIY'er and it is always a problem when it involves things that need approvals, inspections, etc. I understand the reasoning behind it and surely know there are many who would do really unsafe things if we did not have these processes in place but I also know there are many (more than you want to know) who are "professionals" that manage to get away with doing really dangerous things and bad workmanship.

For the most part in my life I have just gone ahead and done things and asked for forgiveness later if it is ever necessary. But anyhow enough of that.

I have a couple of more questions. Actually I will probably have many more as I think of them.

Why are the costs for panels so high? I know they have been coming down but if the US is really in an energy crisis why can't we make these things cheaper. I suspect the rebates might have something to do with it. As soon as one agency gives us a break the seller might realize they can make a little more profit. It just seems to me that the real incentives should go to the companies that make the PV's and not necessarily the end user. Just about everything else we have made starts out at a high price and then through demand and quantity production is made substantially cheaper. Will this ever happen with PV's?

As far as regulation, I wonder how many ignore the net metering etc. and just use the systems to supplement or reduce there electric bill thus for the most part eliminating connection to regulating authorities. I guess what I am saying here is if I generate power and it offsets power I would normally get from the utility how would they know the difference. I could have just turned the item off and reduced the energy. Electrons don't have any DNA tag on them.

I know as a public forum you cannot advocate breaking the law but I am sure there are countless systems done in this way and owners who don't notify some agency every time they change or add a panel. There are not very many places that you can legally put your own toilet in or do electrical or plumbing work without a licensed professional. We all know how often those rules are really followed.

Now the real scary thing is when they start taxing the use of the sun! Maybe this is already happening but if not it will. Once this stuff really does get cheaper and more efficient and the central generators loss business the tax revenue from that source will dry up and have to be made up somewhere else.

solar_dave · May 2010

Re: some newbie questions

Well one of the reasons for the compliance goodies is so the insurance companies are happy. If anything happens from the system, like arc and fire, your insurance policy could be null and void.

Also I think if you can find your grid providers usage agreement, you will see they usually reserve the right to ensure your equipment doesn't interfere with theirs.

The first thing that will probably happen is your bill will drop (maybe drastically) and they are going to wonder why.

In my case the Utility rebate hinged upon the professional installation with permits. that is the only thing that made my system a capitalist purchase.

BB. · May 2010

Re: some newbie questions

dsc3507 wrote: »

For the most part in my life I have just gone ahead and done things and asked for forgiveness later if it is ever necessary. But anyhow enough of that.

You probably are not alone... Remember you are "competing" with the local power company and they do have the right to pull the meter on your home if they so choose. Also, your insurance company could choose to avoid paying out on claims if they wanted.

Has any company done this yet? Not that I have seen (but I am not in the industry either).

Why are the costs for panels so high? I know they have been coming down but if the US is really in an energy crisis why can't we make these things cheaper.

A decade ago, they were $10 per watt. Five years ago I paid $5 per watt, and now they are around $2.50 per watt and companies are having real financial problems making money on panels... I would suspect that this is about the floor pending some (probably as yet) unknown breakthrough technology. Raw materials, taxes, labor, etc. may push prices up.

I suspect the rebates might have something to do with it. As soon as one agency gives us a break the seller might realize they can make a little more profit. It just seems to me that the real incentives should go to the companies that make the PV's and not necessarily the end user. Just about everything else we have made starts out at a high price and then through demand and quantity production is made substantially cheaper. Will this ever happen with PV's?

The old early adopter that pays for new technology (cars, computers, flat screen TV's, solar power, etc.)... Then mass production follows on and drives the prices into the floor. Seems pretty normal here.

However, I will agree that government incentives seem to drive prices up by almost exactly the rebate/credit the governments offer (Prius cars, GT Solar from state of California, etc.). And, when those rebates/credits go away, many of the vendors that made their profits on the artificial pricing spread seem to go away too... Actually a very painful process.

We needed government rebates to bring "solar prices down" but did not need Gov. Rebates to bring Flat Screen TV prices down...

Europe is backing away from high credits and artificial tariffs that support Solar RE "investments"--They are seeing that this is unsustainable.

As far as regulation, I wonder how many ignore the net metering etc. and just use the systems to supplement or reduce there electric bill thus for the most part eliminating connection to regulating authorities. I guess what I am saying here is if I generate power and it offsets power I would normally get from the utility how would they know the difference. I could have just turned the item off and reduced the energy. Electrons don't have any DNA tag on them.

Well, utilities monitor their customer's bills very closely... If your bill suddenly drops and or "goes negative"--they may take action.

In California, the law is that you cannot leave the grid and/or generate your own power because the utilities have taken out loans in your name to build and maintain the power infrastructure. There is hole for Solar RE power--but the penalties are there and available.

Regarding my experience, my installer operated my system once we had the signoff from our building inspector and utility. However, the utility was 3 weeks late in installing my meter. Well, the meter ran backwards and the utility "assumed" is was a meter reader's typo... So they just added 1,000 kWH to my "usage" and billed me $200 or so for the privilege (my previous electric bills where in the $30 per month range). I had to do a whole bunch of hand waving to get that bill killed (by that point, my meter was changed out and the old meter was lost/tossed and they could not get the old reading that went backwards).

Now-a-days, many utilities simply install a meter that does not run backwards. Either you send the utility "free energy" or they actually bill you for the energy you are sending out (i.e., use 100kWH and generate 100kW, you don't get a 0kWH bill, you get a 200 kWH bill instead). "They" are paying attention.

I know as a public forum you cannot advocate breaking the law but I am sure there are countless systems done in this way and owners who don't notify some agency every time they change or add a panel. There are not very many places that you can legally put your own toilet in or do electrical or plumbing work without a licensed professional. We all know how often those rules are really followed.

Yep, and there have been systems that where installed with permits and inspected--that have caught fire too... Either because of poor workmanship, illegal panels that nobody checked, or act of God and squirrels...

Now the real scary thing is when they start taxing the use of the sun! Maybe this is already happening but if not it will. Once this stuff really does get cheaper and more efficient and the central generators loss business the tax revenue from that source will dry up and have to be made up somewhere else.

Yep--you can fear that one already... You grow your own biodiesel fuel or (when fuel prices where high) buy frying oil from Costco and put it in your diesel car.

Last time we had fuel heading towards $4 per gallon, there were state tax officials "sticking" diesel tanks in vehicles looking for un-dyed/un-taxed fuel (and the one guy with the "bio-diesel" bumper sticker was hard to miss :roll:).

Electric vehicles, untaxed electricity, and missing road taxes... Eventually the state will not be able to ignore that and we will see GPS based road tax meters rolled out.

Oregon's 'GPS Tax' Raises Privacy, Efficiency Worries

Oregon is already trying this because Prius' don't buy enough fuel and don't pay "their fair share" of road taxes... One plan had a Hummer and a Prius paying the same $/mile road taxes (add congestion charges, urban charges, etc. and you have a real big brother mess)....
-Bill

niel · May 2010

Re: some newbie questions

just kicking thoughts around here, you know i hear this question of, "why is solar so expensive?", all of the time. maybe you should be asking your utility why they can't give you electricity cheaper as their profit margins are far better than solar's. in spite of some claims, solar is not a cheap and easy thing to accomplish because of the processes needed. it has also been found that improving the processes has basically improved the narrow profit margins for manufacturers with some lowering of prices to consumers too. solar really isn't for everyone and is not a panacea answer to all of our planet's woes, but many need it (as opposed to want it) and it is a partial answer in many cases.
i am not discouraging solar for anybody as there is no comparison to buying $20,000 worth of pvs or paying a utility that much to put in a few poles to feed power to your abode just to further charge you for the electricity that constantly goes up in price. solar costs have actually been going down some and is one of the few things around that can say that.
so my question to you might be, why is utility power so expensive and unreliable? which is actually making more $ and which is a monopoly? try not to criticize what solar costs too much, but we all would like things to be cheaper as that is a prime motivator to many of us no matter what is being talked of. it just so happens that commercial manufacturers can make a reliable pv better and cheaper than we can. remember it is about what things cost and the special glass, backing, sealants, as well as the obvious cells and framing in a package that may have been tested for safety compliance and all with a warranty in the neighborhood of 20-25yrs you can't match for the same $ cost.
diy pvs are not discouraged as it is something many feel good about doing, but don't expect to mass produce diy pvs and put them on your roof and get an atta boy from your local inspector or insurance company and do expect diy to cost you more money than commercially made stuff. there are aspects that you might try to diy if you are technically so inclined in the electronics end of things for solar. many have successfully done this and are making some profit, but they aren't getting rich. i know this because some of them are on this forum.

nvyseal · May 2010

Re: some newbie questions

Hi niel,

To add to this i often wonder why all new homes built are not equipped with some sort of solar, PV, heating etc. and the government rebates the home builder for the install depending on the size of unit. The new home owner can afford more in mortgage because of a cut in power bills, the power company does not need to build more power plants, and the states start meeting their renewable energy programs. It's just kind of a win, win situation all around

BB. · May 2010

Re: some newbie questions

nvyseal wrote: »

To add to this i often wonder why all new homes built are not equipped with some sort of solar, PV, heating etc. and the government rebates the home builder for the install depending on the size of unit. The new home owner can afford more in mortgage because of a cut in power bills

The return on investment from Grid Tied solar is probably, at best, about the same as the mortgage interest rate (5% or so)... And if solar adds to the price of the house, property taxes may go up (when you add solar in many states, the solar panels are example from property taxes--may not be true in the sale of a home)... So, I am not sure that there is any net/net savings in money--and could be stuck with higher property taxes (or as a new programs in California can, it puts the cost of the loan in the property tax payments--and those costs are paid by the buyer, and any future buyers, for the life of the loan/program on the property tax bill for the next 20 years).

, the power company does not need to build more power plants, and the states start meeting their renewable energy programs. It's just kind of a win, win situation all around

At this point, it has been hard to show that solar/wind/etc. can reduce peak power loads for a utility... While Solar PV power is relatively predictable--Wind is not... And in any case, these are not "on demand" generation systems but "as available power" type systems.

Last I looked, Denmark has actually increased use of coal (thread discussing it here) and has yet to decommission any coal fired power plant despite being something like #1 or #2 in percentage of wind energy power for their grid.

-Bill

dsc3507 · May 2010

Re: some newbie questions

diy pvs are not discouraged as it is something many feel good about doing, but don't expect to mass produce diy pvs and put them on your roof and get an atta boy from your local inspector or insurance company and do expect diy to cost you more money than commercially made stuff. there are aspects that you might try to diy if you are technically so inclined in the electronics end of things for solar. many have successfully done this and are making some profit, but they aren't getting rich. i know this because some of them are on this forum.

Well I wasn't trying to make money as in selling things and I doubt I would try to assemble PV's, I was just trying to save bucks by assembling a system and it is really more than that. If you are a DIY you would understand. You like the satisfaction of doing things yourself and it is very hard to relinquish that to another person. I take pride in what I do and I hate it when you go to someones home and they have all this great stuff, impeccable yard etc. and they have never lifted a finger, just payed out the money for someone else to do it. Where is the pleasure in that. might be for some people but not me. I generally research things to death and when I am ready to do it I am sure of the product and what I am doing. When you call a company in you get there products which may not be the best and also the marked up prices plus the labor. I can't blame them but in some cases the mark up is ridiculous compared to what it would cost you to do it yourself. I haven't been around solar long enough to know if that is the case in that field but in plumbing, electrical, automotive, etc. it certainly is.

BB. · May 2010

Re: some newbie questions

If you want a DIY type solar project... Look into solar thermal (hot water, space heating, hot air space heating, etc.). Those projects really lend themselves well to DIY and actually can save you a fair amount of money too.,

Take a look at this thread--It is a bunch of random (until I edit it together in a FAQ someday) solar information stuff--including DIY projects:

Working Thread for Solar Beginner Post/FAQ

Depending on the price of power and your local weather conditions--there are various forms of heat pump type water heating systems now--Which can be very competitive with solar thermal (in above thread too).,

-Bill

some newbie questions

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