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How far can solar panels be away from house?  RSS feed

 
Ryan Mitchell
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Location: Charlotte, NC
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So I am moving to some land and will be putting in a 1 kw solar panel off the grid (batteries) system, because of the location of the house it isn't going to work to put the panels on the house, but there is a perfect place 450 feet away that gets great solar exposure. So my question is, will this distance present a problem? What voltage drop will I experience with this distance and would it be better to convert it to AC at the panels or at the house?
 
S Bengi
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Location: Massachusetts, Zone:6/7, AHS:4, Rainfall:48in even distribution
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If you connect the solar panels in parallel, it is possible to gets the volts up to 120+DC and have equal power loss either way.
However if you plan on running your house of AC vs DC, I would just build a little shed to house the electronic/batteries off-gassing explosive hydrogen, toxic lead & sulfur, etc
 
John Polk
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If you want to increase the voltage, the panels would need to be wired in series.
Wiring in parallel will increase the power out, but not the voltage.

With that long of a run, you would need some large diameter wire to minimize the losses.

 
Ken Peavey
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It's my understanding that you will lose more power running DC across a distance. If this be the case, and someone will correct me if I am in error, then an inverter with the panels would be desired. AC transmission across that distance will have less power loss.
 
laura sharpe
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Ken Peavey wrote:It's my understanding that you will lose more power running DC across a distance. If this be the case, and someone will correct me if I am in error, then an inverter with the panels would be desired. AC transmission across that distance will have less power loss.


nope that is pretty much it. But please remember 450 feet is really not that much of a distance, when they speak of distances they speak of wiring a large city or the eastern seaboard.
 
S Bengi
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Location: Massachusetts, Zone:6/7, AHS:4, Rainfall:48in even distribution
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Thanks for the correction John.
Wiring in series will increase the voltage but keep the current constant.Where as wiring in parallel will keep the voltage constant but increase the current.
Depending on the panels you use you might have to do a combination to get the voltage to voltage to 120v and the current to
http://physics.bu.edu/py106/notes/Circuits.html

Here are a 4 solar panels for you at 1kw. 1kw=(30V*4) *8A, its only $1200 if you look around you should find it cheaper.
http://www.amazon.com/Renogy-Solar-Photovoltaic--1000w-System/dp/B009ZOJ14S/ref=sr_1_3?ie=UTF8&qid=1360010751&sr=8-3&keywords=solar+panel+250w

Using AC vs DC does not make a difference what does is the voltage to current ratio.
And in DC the voltage is usually low whereas in AC the voltage is high. So as long as the voltage:current is the same the loss is also the same.

So to minimize power lost you could, shorten the distance or increase the wire diameter or decrease the current/increase voltage.

So with AC or DC voltage at 120V and current at 8Amps, you want to keep your power loss/voltage drop below 4V
To do that you are going to need a wire size of 1-6AWG aka 1/4inch to 1/8 inch the bigger the better.
Check out this applet it will help you calculate it.
http://www.electrician2.com/calculators/vd_calculator_initial.html

To handle the high DC voltage you are going to need one of the "new" MPPT controllers that can handle high DC voltage, they cost $600 vs the usual $300
http://www.wholesalesolar.com/controllers.html

Solar Panel1kw $1000
Wire $
Controller$600
Battery$3000
Inverter/Charger$1000
 
Vern Faulkner
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Ken Peavey wrote:It's my understanding that you will lose more power running DC across a distance. If this be the case, and someone will correct me if I am in error, then an inverter with the panels would be desired. AC transmission across that distance will have less power loss.


That is NOT correct. Power losses are a function of current - I^2*R - and the current doesn't give damn about which way the electrons are moving (DC versus AC.) In fact, many underwater transmission cables are DC.

The issue is the voltage. To minimize losses, the power needs to be transmitted so that the voltage should be as high as possible, the current as low as possible.

What we need to know is the operating voltage of those panels. I'm going to assume a VoC of 37.7, max power volts at 30, 240 Watts (eight amps), since that's pretty common. Wiring those four panels in series will create a eight amps at 120 volts. (There are only a few controllers that can handle the 150-volt open circuit voltage, and if you live in a cold climate, the potential increase in VoC due to cold means you're likely looking at a Midnite Classic 200 as a controller choice.)

Pushing that through 900 feet of AWG 8 wire wire (450 x 2, 50 cents per foot average = $450) produces a voltage drop of 3.7 per cent,The target is two to three per cent.
Pushing that through 900 feet of AWG 6 wire will produce a voltage drop of 2.3 per cent: close to acceptable. Not sure what six-gauge wire goes for, but it ain't cheap, I'm sure.

The difference between DC and AC here is moot: you're still looking at power losses. Assuming #8 wire, amd 120 VAC, you're stilll looking a 3.7 per cent voltage drop = 24 watts give or take - for an inverter driving AC. The plus, however, is that if you keep the voltage at 120 VAC, you're going to limit losses. That's because the 120 VDC from the panels is a best-case scenario. Partly obscured sun will drop both voltage and current, as you probably know - but just spitballing some figures, say, 70 volts at four amps, or 280 watts at the panels, will become 271 watts at the controller, after a 3.2 per cent voltage loss across that wire.

My thought? You have to figure out if the insolation at the two locations is of such a difference as to merit the extra costs.

 
John Polk
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A friend of mine was working at a very large Scandanavian electric company. An island was one of their customers, and through population growth, as well as adding more powered machinery, the island's power needs outgrew the capacity of the land based generator. Everything on the island was DC. A competing company also wanted in, so competition grew for the contract. The existing trans oceanic cable could not handle the new load requirements. Huge infrastructural upgrade was required.

With very little engineering, my friend found a solution which gave his company the winning bid. Rather than run 40 miles of new cable, they joined the cables into a single Positive (+) cable, and provided a suitable Ground (-) at each end. End of story.
 
Vern Faulkner
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John Polk wrote:
With very little engineering, my friend found a solution which gave his company the winning bid. Rather than run 40 miles of new cable, they joined the cables into a single Positive (+) cable, and provided a suitable Ground (-) at each end. End of story.


That would only be viable for very high voltage power sources, I would think, making it impractical for the situation at hand.
 
Charles Tarnard
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There's a something I've read on this thread and other places on this site that I'd like to address. Running cells in parallel increases the current capacity, not the current. If you hook 147 cells up in parallel, then leave the positive and negative terminals open, you'll still have 0 current. Hooking cells together in series will increase the voltage. It's a minor detail, but it sticks in my craw a bit.

If you think of current as a result of other conditions, it makes it easier to visualize (it does for me anyway). Voltage and impedance (resistance in most DC applications) are factors that are set, and current is the result of those conditions.

Also, with a suitable grounding connection, Mr. Polks idea should work fine. Depending on soil conditions, getting a suitable grounding connection may not be a trivial matter. If it doesn't create a consistent voltage to ground it's no real problem to drag another wire out there later, so long as you're not fed up with it at that point. It will always be a more reliably successful installation to run a second wire.
 
Rosco Heber
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Location: Arkansas Ozarks
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If you used a transformer to step up the voltage you could use smaller wire. Then at the house a step down transformer to get down to 120 or 240 whatever your wanting. There is a reason the power companies run the voltage AC and a high voltage between transformers.
 
A Bowen
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Location: Swanton OH
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Ryan
Make the 450' run with whatever will have the higher voltage. If this is for off grid (12, 24, or 48V DC) then put the inverter at the modules and run the 120 or 240V AC line to the house.

If this was grid ties and your solar array is running 400+ Volts DC then put the inverter at the house.loads.

You will want to size the wires for voltage drop either way but at higher voltages (and lower amperage) the wire is less expensive.
 
Angelika Maier
pollinator
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Location: cool climate, Blue Mountains, Australia
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No technical input here: there are some very good reasons not putting solar panels on the roof:
If you have trees close to the house and experience high winds with branches flying around.
If you have bushfires and a paddock which is not likely to burn (at least you keep your panels),
but I would not put the panels too far from the house they might be stolen.
 
Jose Romero
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Ryan Mitchell wrote:So I am moving to some land and will be putting in a 1 kw solar panel off the grid (batteries) system, because of the location of the house it isn't going to work to put the panels on the house, but there is a perfect place 450 feet away that gets great solar exposure. So my question is, will this distance present a problem? What voltage drop will I experience with this distance and would it be better to convert it to AC at the panels or at the house?

In my opinion, the ideal would be to prepare a room near the solar panels to place the inverter, battery bank, charge controller etc. So you send AC current from the inverter to the house, because if you try to send DC current would be very expensive to use the correct cable for 450 feet, besides the risk of resistance and voltage drop. Remember that AC power is right for transmitted over long distances. Remember to measure how much current AC going to transmit between 450 feet, so use the correct wire. I hope I was helpful.
 
Barry Fitzgerald
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Location: Welland, Ontario, Canada
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My thought on this would be to just put the panels 450 feet out there and run the largest size wire you can afford and not worry about the losses. When you have lots of great sun you will charge your batteries fully and your charge controller will limit the output of the panels, the panels will simply put out full output a little longer before the controller shuts them down.
You will have to get this working to see if you have sized the number of panels and battery bank correctly.
 
Wes Johnston
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I'd like to weigh in on this subject. There is a guy I've known for 15 years that uses his prius' 220v battery to run everything. If you leave the car on, it'll crank up as needed to recharge the batteries. What he found that is relevant here is that switch mode power supplies rated for 110-240v will run on dc as well as AC. So you could stack your solar cells in series to get 220vDCand transmit that over a great distance with a switch mode power supply at the home end giving you 12vdc.

Anyway, his web site is http://www.aprs.org/APRS-SPHEV.html
 
Wes Johnston
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Jose Romero wrote: Remember that AC power is right for transmitted over long distances. Remember to measure how much current AC going to transmit between 450 feet, so use the correct wire. I hope I was helpful.


You are correct in putting the batteries and inverter and such at the remote location and running 120vac to the house. Perhaps the original poster here should run 120vac from the remote location to his house and run a 2nd pair of wires to remotely turn the inverter on and off.

But just to be pedantic, what makes AC suitable for long distance is the jacked up voltage lets you use less current and therefore smaller wires and smaller voltage loss. A company called ABB is working on high voltage power supplies (like 400kv) to build a long distance transmission line that uses high voltage DC.


 
Cindy Mathieu
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Historically speaking, as a society, we went away from high voltage DC wires to AC. One of the main reasons, as I understand it, was that so many people were being killed by the high voltage DC.
 
Satamax Antone
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The other reason is electrons are being bounced back and forth, thus not making gaps in the copper wires, and being a bit easier on the sections of copper needed for a given amperage. IIRC
 
Wes Johnston
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Advantages of AC: Transformers allow us to step up voltage easily for long distance transmission without current losses. Arcs across switches extinguish within 8ms at 60hz.
Disadvantage of AC: Power losses in transformers. Peak to peak voltage is 2.8 times higher than the label says on AC. For example, your typical 120vRMS wire in your house actually runs 336v peak to peak. They call it 120, because if you average the power, it does the same work (energy) as 120v DC, so they call it 120v AC RMS.

Advantage of DC: Voltage is actually lower than AC for the same number of watts.
Disadvantage of DC: If it arcs, the only way to extinguish the arc is distance or killing the power at another point. At 120v, that distance is less than 1/8".

You can be killed by DC just as easily as AC, but AC due to it's higher P-P voltage is more likely to jump off the wire and bite you (in the context of those big high voltage lines that go from state to state). Really, the reason we went to AC was b/c more voltage means less amps for the same watts and super high voltage is not suitable for home use. So we step up and step down volts easily with transformers. The safety of the workers wasn't a factor - esp in the 19th century.

Nikola Tesla was the genius who realized the whole step up, step down thing. An amazing man! He's *the* reason we don't have a power plant in every neighborhood.

For *this* application DC is, IMHO, a suitably efficient means to get power from your remote solar cells. The emphasis here is on efficiency. To convert the solar cells' power to AC so you can have batteries near the cabin, then back to 12 or 24v DC, then back to AC to use appliances introduces more inefficiency. In my mind, better to convert once. Make a remote 120v DC stack of solar cells and use switch mode power supplies to get lower voltage DC.

By the way, if any of you open up a computer UPS power supply, how many batteries are inside? Many of the larger units run 120v worth of batteries. Most smaller ones use 60v batteries. The reason is to reduce the amount of current that has to be switched.

Just my thoughts.
Wes
 
Cindy Mathieu
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Well, don't get me wrong. I like DC. We have large batteries and remodeled our space and added DC lighting and fans, changed our desktop computer power supplies to DC, and changed our well pump arrangement to 2 DC pumps rather than one large AC one. It seems to me that some things are better done with DC, particularly if you are getting some from the sun.

Also, I hope you have seen the movie: "The Secret of Nikola Tesla" made in 1980. It is available from Netflix.
 
Wes Johnston
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Solar power

Here's a guy I've known for YEARS thru my ham radio hobby. He's definitely a think out the boxer. What he discovered a few years ago was that most switch mode supplies (ie your cell phone charger and your desktop pc power supply) are happy with 120-330v DC. I'm going to guess that newer LED 120v lights will also run on 120v dc. I can't say you should wire this to your breaker box in your house (think of the wall switches that are not suitable for DC arcing, and ceiling fans), but a lot of home things will run on 120 or 220v DC. If you do build a stack of batteries for 120v, do not simply tap off the bottom battery to get 12v... you'll reverse polarity that battery. If you need 12v from a 120v stack of batteries use a 12v power supply. golf cart people do this all the time, they take 48v batteries and use a power supply to get 12v.

So instead of wiring your grid-tie array for 500 VDC to minimize wire loss, wire them in series parallel to about 250 to 330 VDC so that you can use this power directly if needed. Just about any system that has a nameplate showing it is good for 100 to 240 VAC will work on 150 to 330 VDC too! And almost all modern electronic systems come that way! See more details. But most appliances and lights are a problem. You CANNOT wire two CFL bulbs in series to equal 250 VDC, they are unstable and one will take all the voltage and burn out instantly. But you can series two incandescents of the same wattage, or you can special order special 220 volt CFL bulbs normaly sold in Europe. But you will pay 10 times their value. I'm looking for surplus LED christmas light strings! Large LED bulbs are ideal beacuse they run on 100 to 250 volts AC or DC but cost a king's ransom ($50 each).
 
Chris Olson
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Ryan Mitchell wrote:So I am moving to some land and will be putting in a 1 kw solar panel off the grid (batteries) system, because of the location of the house it isn't going to work to put the panels on the house, but there is a perfect place 450 feet away that gets great solar exposure. So my question is, will this distance present a problem? What voltage drop will I experience with this distance and would it be better to convert it to AC at the panels or at the house?


Definitely run DC if this is an off-grid installation. We have one 3 kW solar array that is 930 feet from the power room. The array runs at 370 volts (370 Vmp, 433 Voc) and the loss is negligible. Array voltage is stepped down to battery voltage with a 600V MPPT solar controller. When running high voltage arrays just remember to allow enough headroom for your MPPT controller in cold weather. We have seen our 3 kW array at 520 Voc in -30F weather on a sunny day.
 
Alex Shorts
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Maybe this info will help with the design and keeping costs down. I'm a designer for a huge solar company and have done designs for both residential projects (2kw+) and commercial projects (2MW).

Here are some guidelines that we follow:
Voltage drop
-up to 5% DC, 2% AC
-higher the voltage the less the voltage drop. As stated before maximize voltage by utilizing as large as strings as the inverter will allow.
-the loss in power at drops in voltage is not significant. A secondary reason that we utilize these guidelines is to make sure we never drop out of the voltage windows of the electrical equipment.

Conductors
-upsize as needed to address voltage drop
-compare costs with Aluminum conductors. Copper conductors can be very costly in comparison. Just keep in mind that your equipment may not always be rated to allow for Al connections. If this is the case a transition to a Cu conductor can happen right before the connection.
 
Peter Liv
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Chris Olson wrote:
Ryan Mitchell wrote:So I am moving to some land and will be putting in a 1 kw solar panel off the grid (batteries) system, because of the location of the house it isn't going to work to put the panels on the house, but there is a perfect place 450 feet away that gets great solar exposure. So my question is, will this distance present a problem? What voltage drop will I experience with this distance and would it be better to convert it to AC at the panels or at the house?


Definitely run DC if this is an off-grid installation. We have one 3 kW solar array that is 930 feet from the power room. The array runs at 370 volts (370 Vmp, 433 Voc) and the loss is negligible. Array voltage is stepped down to battery voltage with a 600V MPPT solar controller. When running high voltage arrays just remember to allow enough headroom for your MPPT controller in cold weather. We have seen our 3 kW array at 520 Voc in -30F weather on a sunny day.


Hey Chris, what size wire did you run and in what conduit? Any safety issues with running that high DC voltage?

I have a 200 foot distance from panels ( on a sunny hill) to a shady valley cabin.

I am choosing between

#1 locating charger controller, batteries, inverter by the cabin resulting in 200 foot 48 volt dc run( actually variable from 0-60 volts depending on sun and temp)a
or
#2 locating charge controller, batteries, inverter up on the hill .resulting in running 200 foot 120 vac to the cabin.

Seems like I should choose #1 as from my understanding a 5% or so voltage loss on the 120 AC run choice will mean that AC devices simply not work, whereas a loss on the DC, simply means a loss in power, my charge controller will handle from 12 VDC to 60 VDC
To me the issue is not if im loosing a few percent of energy, but whether my devices will work or not. So I will try to avoid long 120 volt runs.

Peter


 
Timothy Black
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Lots of advice here.. I'll throw in a bit!

I have thought about this sort of problem quite a bit, and for me, it looks like you are trading cost and convenience for long term power savings/efficiency. Also, I don't know how comfortable I would be with wiring a solar array all in series to provide hundreds of volts DC.

It seems to me the simplest solution, though not the most efficient, would be to have a local battery bank where the solar panels live. This bank soaks up the solar power, wired in parallel across a bus, and stores it for you.

Then, you have a very high efficiency inverter right there as well, and you invert the power to high voltage AC, transmit it to your house, and use it in a normal way.

If you wanted to really get interesting, you also put in a DC/DC converter on each end to do the same thing, and run a DC circuit to your house to directly power whatever you liked. DC/DC converters can be made to very high efficiencies, so again, not much power loss.

Done and done. If you invest in high quality converters, you will get back good (not fantastic) efficiency, and have a very predictable result. Plus, you can hire a technician to handle your system fairly easily if you need that someday. And if you get the right batteries, they will be easy to maintain, and last for 20 years (think Rolls-Surrette.. although I am looking at making my own Nickel-Iron edison batteries ).

So.. that's what I would do in your situation. I don't want to have to spend a lot of time maintaining my power setup, so I would try to make it as standard as possible, even if it did lose me a few amps along the way. To make up the difference, you can just add one more solar panel or two.

To give you an example of my thinking.. I needed portable power for camping and festivals. I purchased a portable 40w solar setup that folds out and sets up all by itself.. stored its like a briefcase with handles.. It gets attached to an AGM lead acid battery with two standard alligator clamps. Also attached to it via alligator clamps is a 1000w inverter with two outlets and a USB slot.

The darn thing is so simple, takes 2-5 minutes to setup, and has never failed. total cost $230. Expensive for solar, but for a system that is portable, and will store and release 35AH at 12v, thus powering a whole group of warm led lights and a small 10w stereo all night, it is worth every penny. I keep the battery along with a few others attached to a trickle charger which has a small solar cell on it 24/7. This keeps the batteries healthy. Very simple, no thought required, no fancy things involved.

I could have done this for a fraction of the cost! But, my result would not have been as durable, and the parts not as easily swapped. I could have salvaged a deep cycle lead battery and reconditioned it, purchased solar panel cells and made my own panel setup, and built my own inverter from scratch.. all of these things are things I have done for other projects.

Which is why I didn't do them for THIS project. It takes a lot of effort to do these things, and you have to figure out how much you want to trade time for money on something like this. In my case, I didn't want to since it was so small scale.

If it had been a larger scale project, I would have considered that more complicated solution. But.. I know how to do all of this stuff! It would take ME less effort to maintain because I have experience with it. If you do not, I would think more along the lines of convenience and standard parts and methods.

If, on the other hand, you want to use this as a learning project, then forget everything I just said and buy a few books, talk to people, and DIY!

So, that's how I see it.
 
I agree. Here's the link: http://richsoil.com/email
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