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Solar Plans  RSS feed

 
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I'm trying to figure out the best design to run my farm off solar or a solar/wind hybrid.  I have three main buildings plus a garage.  The main buildings are the house, a barn and what is now being used as our country market where we sell our goods etc plus start all of our plants.  Right now we have one power source from the grid that goes from the road to the house.  From there, it splits and a line runs to the yard light which splits again going to the garage, the store, and the barn.  Typically people put the solar on the house, but the roof pitch faces east and west, plus the south side of the house has a large oak tree. Anywhere where a ground-mounted array is possible would be more than 200 feet away. The barn which is about 100 feet from the house has great southern exposure.  The store which is about 75 feet also has great southern exposure.  Both have a lot of real estate to put a lot of solar panels on.  To begin, we could afford to put some solar on one of the two buildings, then add on as we are able to afford to.

Since I am not concerned with being grid-tied at this point, could I set up an array and battery bank on either/both the store and barn and use the existing electrical infrastructure to power all buildings at least to the extent of the solar power output?  Would it be possible to have an array on both buildings, but one battery bank that is charged by both arrays or would it make more sense to have two?  BTW, from the southern exposure on the barn to the southern exposure of the store is probably about 75 feet, however, a battery bank could be set up on the north side of the barn which would cut the distance from the store array to the battery bank to about 40 feet which puts the distance from the panels on the barn to the bank at about 35 feet.
 
pollinator
Posts: 1128
Location: Big Island, Hawaii (2300' elevation, 60" avg. annual rainfall, temp range 55-80 degrees F)
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When we started setting up our solar system, we knew nothing. So hubby spent a lot of time reading as much of the online information, plus books, that he could. We quickly learned that sizing and assembling the system wasn't as simple as we initially thought. Did we want/need a 12 volt system, 24, 48? What would be our energy needs? What would be our maximum load at any particular time? There were lots of variables to consider when choosing the number of panels and the corresponding batteries. DC current cannot be driven as far a distance as AC, something to keep in mind. There are charts online to tell you what the distance would be depending upon your voltage and gauge of the copper wire. And some newer panels have individual micro-inverters, something we are not familiar with.

Because of the expense of heavy gauge copper wire, most systems in my area keep the panels close to the battery bank, as close as feasible. Our barn has panels on the roof. The battery bank is housed in a box along the barn wal right below the panels. The inverter & controller are on the inside wall next to the outdoor battery box. The distances are short. Our house is located about 300' away and has its own independent system.

I really don't have any set figures for you. I'm not that well learned about solar. It's just that your distances sound much longer than what we have. Oh, when figuring your distances, measure the distance that the wire would actually travel, not just the distance from point A to point B. Remember that the wire needs to travel down the wall of the barn from the panels to wherever the batteries and inverter are, so there might be some turns and ups & downs to measure too.
 
pollinator
Posts: 574
Location: Southern Arizona. Zone 8b
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Tim Sipma wrote:Since I am not concerned with being grid-tied at this point, could I set up an array and battery bank on either/both the store and barn and use the existing electrical infrastructure to power all buildings


You could, but having two arrays separated by by long distance is not a good idea on an off-grid setup.  Not unless you have two separate "micro-grids", I'll explain in a moment.

Tim Sipma wrote: Would it be possible to have an array on both buildings, but one battery bank that is charged by both arrays


You typically run low voltage DC from the panels to the batteries, so you want the wires to be as short as possible.

Tpical solar setup goes:

Array --(DC)--> Charge controller --(DC)--> batteries --(DC) --> Inverter --(AC)--> lights & appliances

Connecting multiple inputs on DC is relatively simple as long as the voltages match.  Connecting multiple inputs on AC is impossible unless the voltage AND frequency AND phase angles match.

Off-grid inverters are not usually designed to match AC frequency and Phase.  A few of them are designed to work together but they typically have a short synchronization cable that runs from one inverter to the next, trying to extend that cable will just cause problems with delay, and the phase angles will end up far enough off that it won't work.
They also make a hybrid inverter that is sort of a cross between an on-grid and an off-grid inverter, but that wont work for your setup because they need to have the grid side and the local side (house) on two separate wires with the inverter in between.  I.e. you'd need to disconnect either the store or the barn from the house and then run another set of wires between the two.  It could be made to work, but it's much to complicated (and expensive) to be worthwhile in your case.

So you could run two completely separate setups and never connect the two.  I.e have the array/batteries/inverter on the store just power the store and maybe another outbuilding, and then have the barn array power the barn and house.

However, the simplest and cheapest setup would be to just put panels on one or the other and then only have one set of batteries, charge controllers, inverters, etc.
Unless you use a stupendous amount of electricity, it's not likely you'll run out of roof space on a barn, or perhaps the store (depending on the size).

I'm currently grid-tied.  My 15 panels produce enough energy for my house and to charge my Chevy Volt, and my house runs entirely on electricity (electric heat pump, electric stove, electric dryer, etc.)
Even if we weren't frugal with our power consumption, and didn't live in Arizona, I could probably still power everything with 30 panels or less.  30 panels are about 500 sq feet
 
Posts: 347
Location: Michigan
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You can place the panels anywhere within 300'-400' without major cost in wiring. When we install ground mounted arrays located 300 plus feet from the connection point of arrays up to 8500w are about 35 amps. #2 or #1 wire will do it at about 1% voltage drop at 240vac....

If you use a 250v or even a 600v charge control, you can do the same or better with dc powerto basically wherever you like within reason without using 1/0 or larger wire sizes. Doing so with dc also reduces the harness by a wire, the neutral.

Dont opt away from a nice project where everything can be where you want, because of perception.

A large pv system is not inexpensive up front, but skimping on $500 difference in cost for conduit and conductors, on a $16,000 project is not logical, when you could have it the way you like and be happier with the results.

I would get a few estimates.

Probably a good approach is to place the solar wherever you like and the power center (batteries, inverter, charge, control) near or at the utility service entrance and then your outbuildings and yard light are down stream from the transfer switch. This makes it easy to place all other circuits on battery backup. If you placed the powercenter anywhere else it needs to feed your critical loads panel and so, requires an additional set or sets of wire to do so.

I would draw out a sketch of the site from above and plot the related distances. Depending on the system, it may make sense to do it another way, but usually not for battery backup.

Off grid (and simple grid tie) is different in that you can insert ac power anywhere in the ac system that can handle it (generator considerations) without the need to route conductors to feed various panels in a hopscotch to get proper transfer switching and utility line communication.

Then theres ac coupling....where you get the advantage of being able to place sources and loads anywhere on the ac line that can handle them, but with some extra cost and complexity of operation and caveat to battery charging especially.
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I know some people and even installers who basically designed a ground mount for a solar farm using free online tools like this online solar designer which lets you set the roof pitch like you were saying, battery banks, inverter, service panels and everything then you get a price estimation on how much the system will cost. You can also estimate how much sun your roof will take using Google Tool call project sunroof https://www.google.com/get/sunroof so you can plan which direction to face your panel and at what pitch to get the most sun.

But yeah it really depends on what you plan on doing whether you want to install the ground mount first or get a roof mount first. I think the project itself is pretty cool and bound to get really good return regardless of how big you make the system to be.
 
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Look at doing AC coupling. You can do your standard DC setup at the array with the battery. Then use micro inverters at the array without the battery.

The micro inverters are meant to inject power into the grid and self sync in unity or a set phase with the power line which is "powering" them. This could be a safety for you as if you shut down your main inverter this will turn off the micro inverters at the remote array.

Also if you have the room and don't mind gaming the system I would advise installing on the ground or at least beyond the maximum fire distance from all permitted buildings and then installing regular power meters...
 
Posts: 1780
Location: Massachusetts, Zone:6/7, AHS:4, Rainfall:48in even distribution
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Keep the solar panel+controller+battery+inverter at the barn.
Then run the AC 'wire' to your house. Very little power will be lost. If you are still worried buy a super thick run of wire to reduce the loses even more.

 
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