Newbie questions on PV purchases

The_AlThe_Al Registered Users Posts: 6
Hello All,

I have been reading some of the great posts out there, and reading about different details related to a solar project and wondered if anyone would be willing to provide some opinions on sizing, and types of hardware to purchase.

I am looking to install an off grid unit in my barn, which is a good distance from my house. I would like to install 2-3K watts, but will take advice on more, or less.
I want to be able to power a remote non-potable well pump for watering my crops, occasionally, and to provide water for my animals daily (say 20 gallons a day or so). Some lights in the barn, a garage door opener (~300W), and possibly some hand/power tools.
The occasionally part on the watering of corps I realize will be the sticking point for sizing and advice. I greatly appreciate advice from all.

1) What should I look for in PV panels (size in Watts and volts).

2) Opinions on specific panels would be fantastic.

3) Racking hardware for the PV panels on the barn roof. I am a bit unclear on these as well. There are so many options

4) I think the mppt charger controller is the best way to go, correct? any suggestions?

5) I am bit confused on the volts portion associated with the panels, and pointers on web sites that may provide some clarity would be great. If the mppt takes care of varying voltages, should I worry about 12 vs 24 volt?
5a) Also, I have noticed that some of the panels out there are 20V, does that require I use 12V, or can I use 24Vs?


6) Should I install micro inverters on each panel? Seems logical, but I am not sure if this is the best route?
6a) What is recommended for micro-inverters as the most optimal method and hardware?
6b) If no on the micro-inverter what manufacturer should I be looking at?

7) Any suggestions on the inverter size, keeping in mind I need to power a 30A ~2Kw well pump?

8) As for batteries, any recommendations on manufacturer?

Sorry for the simple questions, and thank you in advance for reviewing and for your time.

Al

Comments

  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Newbie questions on PV purchases

    Welcome to the forum Al.

    Time to rethink the plan. Why? Because an off-grid system is designed around loads: the maximum Watt usage at any time and the total Watt hours used daily. Some of the equipment you mention in passing is going to be pretty big for those numbers. The pump I think you already realize will be a major power consumer. The lights at 300 Watts seem simple enough, until you multiply them out by how many hours they are on. Then all of a sudden you have major Watt hours.

    Off-grid systems revolve around the batteries, which must be able to supply the loads. The panels are a secondary thing; there needs to be enough to recharge the batteries.

    As a rule micro-inverters don't fit in to off-grid systems; they are a grid-tie device meant to feed back to the AC grid.

    Off-grid inverters come in 12, 24, and 48 Volt sizes. The more power needed, the higher the system Voltage. Solar panels come in quite a range of Voltages too, and it is necessary to configure them in a manner that meets minimum Voltage requirements for charging the battery. That is why we talk about "true off-grid" panels (Vmp 17-18 for 12 Volt system, 35-36 for 24 Volt systems, double up for 48 Volt systems) and "grid-tie" panels which have "odd" Vmp not suited for direct use with battery-based systems unless an MPPT type controller is used.

    At this point you're not ready to start discussing specific equipment. You need to have those target numbers for power usage. Chances are when you do get them it will turn out to be cheaper to lay a line back to the house and connect to the grid. Off-grid power is expensive.
  • vtmapsvtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    Re: Newbie questions on PV purchases
    The_Al wrote: »
    I want to be able to power a remote non-potable well pump for watering my crops, occasionally, and to provide water for my animals daily (say 20 gallons a day or so). Some lights in the barn, a garage door opener (~300W), and possibly some hand/power tools.

    Welcome to the forum. I totally agree with Cariboocoot's bottom line: it will probably be more cost effective to run a power line from the house.

    Just in case we're wrong about that, tell us a bit about your water situation... what sort of well, spring, brook, etc are you pumping from, and how much water do you need? Often, a system design will revolve around the water pump which may be the largest peak load as well as the largest average load.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • The_AlThe_Al Registered Users Posts: 6
    Re: Newbie questions on PV purchases
    Welcome to the forum Al.

    Time to rethink the plan. Why? Because an off-grid system is designed around loads: the maximum Watt usage at any time and the total Watt hours used daily. Some of the equipment you mention in passing is going to be pretty big for those numbers. The pump I think you already realize will be a major power consumer. The lights at 300 Watts seem simple enough, until you multiply them out by how many hours they are on. Then all of a sudden you have major Watt hours.

    Off-grid systems revolve around the batteries, which must be able to supply the loads. The panels are a secondary thing; there needs to be enough to recharge the batteries.

    As a rule micro-inverters don't fit in to off-grid systems; they are a grid-tie device meant to feed back to the AC grid.

    Off-grid inverters come in 12, 24, and 48 Volt sizes. The more power needed, the higher the system Voltage. Solar panels come in quite a range of Voltages too, and it is necessary to configure them in a manner that meets minimum Voltage requirements for charging the battery. That is why we talk about "true off-grid" panels (Vmp 17-18 for 12 Volt system, 35-36 for 24 Volt systems, double up for 48 Volt systems) and "grid-tie" panels which have "odd" Vmp not suited for direct use with battery-based systems unless an MPPT type controller is used.

    At this point you're not ready to start discussing specific equipment. You need to have those target numbers for power usage. Chances are when you do get them it will turn out to be cheaper to lay a line back to the house and connect to the grid. Off-grid power is expensive.

    Thank you for the information.

    The power usage in the barn will be minimal daily. Only to supply water for the animals, a few gallons daily ~10, and sporadic lights being on. The occasional use of
    I would like to be able to use the well to water some of my crops, as needed. I could run a power line, but think it would be fun to try setting up a PV system.
    Also, I did not mention I have a generator I can use if needed.

    Here are some of the stats I need in the barn:
    - The well pump would be on for ~1 min a day assuming 10gmp, so say 600/60 = ~10watts, correct? Easier than carrying it over.
    - Lights ~120w will be on only when in the barn during the evening. During the day there will be minimal usage as well.
    - Garage door I was thinking of installing ~300w is used on an as need "instant" basis
    - Basic tools that I want to move from the garage to the barn, which I do not use very often such as: skill saw, table saw, etc.
    - Plugging in the block heating element in for the tractor in the winter months ~600w, for say 20 minutes only when needing to plow snow.

    BTW I am in zone 5a, in MA.

    Thanks again.

    Al
  • The_AlThe_Al Registered Users Posts: 6
    Re: Newbie questions on PV purchases
    vtmaps wrote: »
    Welcome to the forum. I totally agree with Cariboocoot's bottom line: it will probably be more cost effective to run a power line from the house.

    Just in case we're wrong about that, tell us a bit about your water situation... what sort of well, spring, brook, etc are you pumping from, and how much water do you need? Often, a system design will revolve around the water pump which may be the largest peak load as well as the largest average load.

    --vtMaps
    Thanks vtMaps

    The well is about ~150Ft down, typical for the NE area. Figure about 10G a day for the animals.

    Thanks
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Newbie questions on PV purchases

    Here's what I'm seeing:
    Well 150 feet deep = 240 VAC 3/4 HP submersible pump with a start-up demand in the neighbourhood of 3kW. Running Watts probably near 600, not 60. So whereas the total Watt hours for it will be small, the start and run demand are not. This is the sort of thing that causes trouble: just to get the pump started you need a fairly high capacity inverter and a strong battery bank to take the "hit".

    So let's leave the well pump for the gen, perhaps? Large enough above ground tank to charge it occasionally and let the pressure system do the rest, perhaps?

    From my own system: 1/3 HP pump draws 800 Watts running, over 1 kW to start. It runs for about 6 minutes to charge the pressure tank with around 30 gallons. I do this midday when the batteries are full and there's "extra" power available from the panels. Otherwise if I need water I start the gen.

    The power tools you mention have a similar problem, only sort of in reverse: they start easily because there is no load on them then, but then when you put them in wood the power demand goes up. Very hard to judge a battery bank against occasional, unpredictable loads. I have tested such tools and the results are here somewhere. The worst was an air compressor, not surprisingly.

    Block heaters tend to be more than 600 Watts too, in my experience. Unless you actually have the number from the heater in question expect more. I don't know what the weather is like where you are, but in our -40 Winters we rarely have to use the block heater. Diesel is another story; they can be hard to start at warmer temps even with ether. Often the fuel congeals (yes; been there, done that, ran the salamander on it).

    If you are interested in experimenting with solar you may want to build a small, non-critical system first. It will give you an idea of the technology, limitations, and expenses involved. Solar power for your barn lighting, for example, can be the easiest goal to achieve. At least that way you wouldn't have to start a gen just so you can see where you are!
  • vtmapsvtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    Re: Newbie questions on PV purchases
    The_Al wrote: »
    The well is about ~150Ft down, typical for the NE area. Figure about 10G a day for the animals.

    I presume that this is not the same well that supplies your house, because your house well already has power.

    Building an off-grid system is expensive and its usually more cost effective to conserve a watt than to generate a watt. My point being: look for a better way to pump water. There are a number of options such as VFD with your current pump, or buy a different pump. Look here for some options: http://www.solar-electric.com/sodcwapu.html

    Another way to pump water is a direct PV to pump (no batteries) system. When the sun shines you pump water into a tank or cistern. That in combination with a small battery based system for lights might be cost effective.

    If you do want to go forward with your plans to build a system that can power your present pump and tools, you should expect to spend at least $8,000, and that assumes you do it all yourself.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • The_AlThe_Al Registered Users Posts: 6
    Re: Newbie questions on PV purchases
    vtmaps wrote: »
    I presume that this is not the same well that supplies your house, because your house well already has power.

    Building an off-grid system is expensive and its usually more cost effective to conserve a watt than to generate a watt. My point being: look for a better way to pump water. There are a number of options such as VFD with your current pump, or buy a different pump. Look here for some options: http://www.solar-electric.com/sodcwapu.html

    Another way to pump water is a direct PV to pump (no batteries) system. When the sun shines you pump water into a tank or cistern. That in combination with a small battery based system for lights might be cost effective.

    If you do want to go forward with your plans to build a system that can power your present pump and tools, you should expect to spend at least $8,000, and that assumes you do it all yourself.

    --vtMaps

    Thank you, good thoughts.
  • The_AlThe_Al Registered Users Posts: 6
    Re: Newbie questions on PV purchases
    Here's what I'm seeing:
    Well 150 feet deep = 240 VAC 3/4 HP submersible pump with a start-up demand in the neighbourhood of 3kW. Running Watts probably near 600, not 60. So whereas the total Watt hours for it will be small, the start and run demand are not. This is the sort of thing that causes trouble: just to get the pump started you need a fairly high capacity inverter and a strong battery bank to take the "hit".

    So let's leave the well pump for the gen, perhaps? Large enough above ground tank to charge it occasionally and let the pressure system do the rest, perhaps?

    From my own system: 1/3 HP pump draws 800 Watts running, over 1 kW to start. It runs for about 6 minutes to charge the pressure tank with around 30 gallons. I do this midday when the batteries are full and there's "extra" power available from the panels. Otherwise if I need water I start the gen.

    The power tools you mention have a similar problem, only sort of in reverse: they start easily because there is no load on them then, but then when you put them in wood the power demand goes up. Very hard to judge a battery bank against occasional, unpredictable loads. I have tested such tools and the results are here somewhere. The worst was an air compressor, not surprisingly.

    Block heaters tend to be more than 600 Watts too, in my experience. Unless you actually have the number from the heater in question expect more. I don't know what the weather is like where you are, but in our -40 Winters we rarely have to use the block heater. Diesel is another story; they can be hard to start at warmer temps even with ether. Often the fuel congeals (yes; been there, done that, ran the salamander on it).

    If you are interested in experimenting with solar you may want to build a small, non-critical system first. It will give you an idea of the technology, limitations, and expenses involved. Solar power for your barn lighting, for example, can be the easiest goal to achieve. At least that way you wouldn't have to start a gen just so you can see where you are!

    Thanks for the reply, again.
    It can get cold here in MA, but the tractor in the barn helps with that somewhat.

    All great advice, and I think I will try to replace the pump and use it scheduled as suggested versus ad-hoc. I think I will start small and see how it goes.

    Thanks again

    Al
  • PhotowhitPhotowhit Solar Expert Posts: 5,905 ✭✭✭✭✭
    Re: Newbie questions on PV purchases

    I think a "...fun to try setting up a PV system" is difficult for us, we're a pretty thrifty bunch. So being thrifty lets look at your needs and how solar works.

    Off Grid solar works best delivering small amounts of electric over a long period, you don't need as large an inverter and the battery 'works' better, delivering more Watt hours than when pushed hard. Your needs require lots of energy over short periods of time, well pump, power tools. I just put in a 4Kw array and off grid system and My investment was about $10,000(reasonably cheap) it can't run your well pump, but might power your tools one at a time.

    In Massachusetts I think you have very good net metering laws and may even have tax breaks other than the 30% tax credit You could invest in a grid tied system likely around $6-7,000 + installation for a 4Kw system and run an electric line to the barn. This might even pay you back most or all of your investment over time. You can likely even be hands on if you check around with electrical contractors who will do the wiring and sign off on the work and let you mount the panels and such....

    If you want this as a backup as well a hybrid system is much less cost effective, but likely more cost effective than a pure off grid system.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
  • PhotowhitPhotowhit Solar Expert Posts: 5,905 ✭✭✭✭✭
    Re: Newbie questions on PV purchases

    If your primary concern is the well pump, you might look into a system direct pumping from panels.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
  • The_AlThe_Al Registered Users Posts: 6
    Re: Newbie questions on PV purchases
    Photowhit wrote: »
    If your primary concern is the well pump, you might look into a system direct pumping from panels.

    Thanks for the advice. Good points, and very much appreciated. I have some great advice to start with from everyone.

    Thanks again.

    Al
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