Newbie Solar System set up question

kcmc68

Hi everyone, some questions about solar system set up plans:

1. For a 500 W system (2 panels x 250 W each), what type of MPPT controller should I use? My budget for the controller is $350 USD. With your MPPT controller recommendation, if I expand my system in future to 1000 W, can the controller still support that wattage?

2. Right now, I am thinking of splitting my 500 W system into 2 sections, 1 connected to the MPPT controller (as above), while the other is connected to an Enphase inverter. Would you recommend using the Enphase inverter and can speak from experience?



Thanks for your response, opinions, and ideas.

Cariboocoot

Re: Newbie Solar System set up question

Welcome to the forum.

You've got a couple of problems here.The first being an off-grid system with 500 Watts of panel doesn't answer the question of what battery Voltage it will run at. For instance on 12 Volts that much panel could put out about 32 Amps of current and charge roughly 320 Amp hours of battery. Half that for 24 Volts. Not even worth considering for 48.

Second, and Enphase inverter is a grid-tie unit. It doesn't really go with the off-grid concept, nor vice-versa.

Perhaps you could tell us what you are aiming to accomplish with the solar panels?

BB.

Re: Newbie Solar System set up question

kcmc68 wrote: »

1. For a 500 W system (2 panels x 250 W each), what type of MPPT controller should I use? My budget for the controller is $350 USD. With your MPPT controller recommendation, if I expand my system in future to 1000 W, can the controller still support that wattage?

What is the solar panel specifications (basically Vmp and Imp). And what is the battery bank voltage and AH rating (20 hour rate).

Are you going to expand the array almost for sure? And will you be able to purchase similarly rated panels (Vmp/Imp) down the road for a reasonable price (in 18+ months, many models of solar panels seem to virtually disappear--Then you are left trying to match another brand/model of solar panels on the same charge controller--or having to purchase another MPPT charge controller if the numbers are too different.

2. Right now, I am thinking of splitting my 500 W system into 2 sections, 1 connected to the MPPT controller (as above), while the other is connected to an Enphase inverter. Would you recommend using the Enphase inverter and can speak from experience?

Enphase units seem to be reasonable...

I have other questions though... Are you going to attach this to your home's utility connected AC panel? Most utilities and building departments require permits (or even licensed electricians). If you install a GT inverter without permits, some utility meters will not turn backwards (or will "charge you" for sending power to the grid). And, the utility usually has the right to disconnect you from the grid if you do this.

If you do go the "permit" route--Your building department may charge hundreds of dollars for the permit. And (in California) for example, they may put you on a Time of Use / Tiered /Seasonal plan which can actually increase your bills if your array is too small.

Or are you planning on creating a micro grid--Using your Enphase to "back drive" an off grid TSW inverter to share the loads and even charge the battery bank from the GT inverter/solar array. This is possible, but there are a few details to discuss to make sure this is done correctly (I would not recommend connecting a GT inverter to back drive a genset (various reasons).

-Bill

kcmc68

Re: Newbie Solar System set up question

Cariboocoot wrote: »

Welcome to the forum.

You've got a couple of problems here.The first being an off-grid system with 500 Watts of panel doesn't answer the question of what battery Voltage it will run at. For instance on 12 Volts that much panel could put out about 32 Amps of current and charge roughly 320 Amp hours of battery. Half that for 24 Volts. Not even worth considering for 48.

Second, and Enphase inverter is a grid-tie unit. It doesn't really go with the off-grid concept, nor vice-versa.

Perhaps you could tell us what you are aiming to accomplish with the solar panels?

Hello! Thanks for the warmish welcome. Here's the specs of my panels that I plan to purchase: http://2solar.ca/shop/solar-panels/ontario-made-solar-panels/250w-mono-solar-panel-ontario-made

Could you also 'dumb down' some of this stuff....fairly new to this stuff...not sure what battery voltage and the other 'gibberish'

kcmc68

Re: Newbie Solar System set up question

BB. wrote: »

What is the solar panel specifications (basically Vmp and Imp). And what is the battery bank voltage and AH rating (20 hour rate).

Are you going to expand the array almost for sure? And will you be able to purchase similarly rated panels (Vmp/Imp) down the road for a reasonable price (in 18+ months, many models of solar panels seem to virtually disappear--Then you are left trying to match another brand/model of solar panels on the same charge controller--or having to purchase another MPPT charge controller if the numbers are too different.



Enphase units seem to be reasonable...

I have other questions though... Are you going to attach this to your home's utility connected AC panel? Most utilities and building departments require permits (or even licensed electricians). If you install a GT inverter without permits, some utility meters will not turn backwards (or will "charge you" for sending power to the grid). And, the utility usually has the right to disconnect you from the grid if you do this.

If you do go the "permit" route--Your building department may charge hundreds of dollars for the permit. And (in California) for example, they may put you on a Time of Use / Tiered /Seasonal plan which can actually increase your bills if your array is too small.

Or are you planning on creating a micro grid--Using your Enphase to "back drive" an off grid TSW inverter to share the loads and even charge the battery bank from the GT inverter/solar array. This is possible, but there are a few details to discuss to make sure this is done correctly (I would not recommend connecting a GT inverter to back drive a genset (various reasons).

-Bill

Hello Bill: I plan to on purchasing these panels: http://2solar.ca/shop/solar-panels/ontario-made-solar-panels/250w-mono-solar-panel-ontario-made

To be honest, I don't know what I want, that's why I'm asking you guys so I can get a better idea of what I should do.

My name is Mark btw.

kcmc68

Re: Newbie Solar System set up question

How does this Enphase stuff work anyways? Is it for entirely off grid, half and half, or selling back to the hydro grid?

Cariboocoot

Re: Newbie Solar System set up question

It's a matter of why you want to purchase the panels more than anything else.

You have two basic choices: battery-based inverter system where the panels recharge the batteries via a charge controller, or direct grid-tie inverter system where the panels energize the inverter which feeds whatever current is available to your household. The first is usually off-grid; no utility power required (although there are grid-tie systems that use batteries for back-up ability). The second, whereas easier and less expensive, requires co-operation from the utility and inspections.

So rather than just buying some panels, do you have a goal in mind? Reduced electric bill? Emergency back-up power? Remote power capacity? Experimenting with solar?

Cariboocoot

Re: Newbie Solar System set up question

kcmc68 wrote: »

How does this Enphase stuff work anyways? Is it for entirely off grid, half and half, or selling back to the hydro grid?

Enphase are grid-tie: they feed current to your household wiring and any surplus would be sold back to the utility. That is why co-operation and inspection is required.

kcmc68

Re: Newbie Solar System set up question

Cariboocoot wrote: »

It's a matter of why you want to purchase the panels more than anything else.

You have two basic choices: battery-based inverter system where the panels recharge the batteries via a charge controller, or direct grid-tie inverter system where the panels energize the inverter which feeds whatever current is available to your household. The first is usually off-grid; no utility power required (although there are grid-tie systems that use batteries for back-up ability). The second, whereas easier and less expensive, requires co-operation from the utility and inspections.

So rather than just buying some panels, do you have a goal in mind? Reduced electric bill? Emergency back-up power? Remote power capacity? Experimenting with solar?

Thank you so much for your reply! My goal is to reduce my hydro bill and to have emergency back-up power. What would you suggest? The top priority is to reduce hydro bill; emergency back-up power is a want, not a need for the time being.

BB.

Re: Newbie Solar System set up question

Hmm... The typical recommendation would be for you to install a ~3-10 kWatt solar array and use Grid Tied inverters (a large central inverter, or a bunch of smaller Enphase type inverters--usually one inverter per panel).

A pure grid tied system (solar panel to GT Inverter to your AC main panel) is the cheapest and most reliable type of Solar Power system out there. However, it does not provide backup/emergency power.

Depending on your electric rates and any local incentives--It is actually possible to save money/make money with pure GT Solar.

However, in some places, the utilities are starting to clamp down on GT Solar Power Systems. The incentive payments are costly and it either drains cash from the utilities or increases power costs for the rest of the customer base (and their customers are starting to get tickd off paying for "green power"). In some cases, I have read of people getting approvals to install their 10kW system then the utility tells them they cannot turn it on. So do the research with your local utility and building department.

And for backup power (a few days/week once or twice a year), off grid solar + batteries is not usually the best investment for backup power. It is just too expensive to power your own home unless you only need a little bit of power (say 3.3 kWH per day, for lights, TV, computer, small water pump) (vs genset + fuel storage).

However, if you are able to install a Grid Tied system (utility is OK with it)--There are Hybrid Inverters that can do GT when the utility is up, and use a battery bank+solar panels+charge controllers to run off grid when the utility power is down. If you have unreliable power (lots of outages, and/or month or more outages and difficult to get fuel to the site), then a Hybrid system may be of interest (still not cheap, but can be very nice).

-Bill

vtmaps

Re: Newbie Solar System set up question

kcmc68 wrote: »

My goal is to reduce my hydro bill and to have emergency back-up power. What would you suggest? The top priority is to reduce hydro bill; emergency back-up power is a want, not a need for the time being.

A grid tie system is pretty much 'set it and forget it'. If you get into batteries you must really be involved with your system and will incur ongoing expenses. If you want backup power when the grid is down you MUST analyze your loads before you design the system. For many folks the most cost effective emergency backup system is a generator.

--vtMaps

gww1

Re: Newbie Solar System set up question

Bill

Or are you planning on creating a micro grid--Using your Enphase to "back drive" an off grid TSW inverter to share the loads and even charge the battery bank from the GT inverter/solar array. This is possible, but there are a few details to discuss to make sure this is done correctly (I would not recommend connecting a GT inverter to back drive a genset (various reasons).

I don't want to steal this thread but maby you could start a thread to explain this in more detail. I have seen many referances but never enough info to be sure of what is really ment, or maby a link where this has already been dicussed, preferably with my current inverters as the off grid portion.

Thanks
gww

Cariboocoot

Re: Newbie Solar System set up question

kcmc68 wrote: »

Thank you so much for your reply! My goal is to reduce my hydro bill and to have emergency back-up power. What would you suggest? The top priority is to reduce hydro bill; emergency back-up power is a want, not a need for the time being.

To reduce your electric bill the steps are: conservation, conservation, and conservation.
Chances are any form of solar electric will cost more per kW hour, and reducing usage will be a better return on the money spent.

As for back-up power, what vtMaps said: generator. Solar only becomes economical for back-up if you need to use it a lot (like some countries where the grid is unstable and unreliable and power is off for many hours every day). Weigh how often and how long the power goes out against the money needed to replace it for critical loads. Generators, especially the small inverter type, tend to come out ahead.

Any time you throw batteries into the mix it gets expensive and more demanding for maintenance.

BB.

Re: Newbie Solar System set up question

gww1 wrote: »

Bill

I don't want to steal this thread but maybe you could start a thread to explain this in more detail. I have seen many references but never enough info to be sure of what is really meant, or maybe a link where this has already been discussed, preferably with my current inverters as the off grid portion.

Thanks
gww

GWW, we can start the discussion here, it is part of the suggested options.

It turns out that many off grid AC inverters are actually bi-directional devices. They not only take DC power from a battery bank, inverter, and send it to the loads--But they can also be driven by another source, and push power backwards back through the inverter's transformer, switching transistors, and back to the battery bank (this could be called synchronous rectification--There are a lots of losses through diode rectifiers. One can uses FET transistors and turn them on and off with electronics to make them behave like very low loss diodes).

Anyway, there are a lot of requirements to make this work correctly.

First, the "power source" to push energy back through an OG AC inverter (the industry name is AC Coupling a GT inverter to an OG inverter) must be perfectly in sync with the OG inverter. So, that prevents using standard AC Generators (industrial AC generators can sync with the grid and also drive energy to the grid--This can be done with, for example, hospital backup generators. Instead of wasting the power during weekly/monthly tests into a load bank, they send the power backwards into the utility grid--with permits, etc.).

It turns out that GT Inverters are exactly perfect for this job. They are always in sync with AC Grid (or in this case, AC Micro Grid created by an OG Inverter) and they output a True Sine Wave (TSW) Wave Form. And it can work with many TSW OG AC inverters (whether they have been designed for this function or not). The OG sets the grid frequency/stability/voltage. And sources/sinks energy depending on the need of the loads and the output of the GT inverter.

But, there are "requirements" for doing this. The OG Inverter has to be at least as large as the GT inverter to absorb all excess power. And the OG AC Inverter should be TSW output, and must be pretty accurate for 50/60 Hz (better than +/- 0.5 Hz).

Next, is the big issue... The battery bank is now getting recharged--And will over charge/die/fail spectacularly if there regulation (OG Inverters are not designed to monitor/control this method of charging).

So, you can now setup a charging control system. You could use a dump controller and dump loads on the battery bank (just like wind power). You could also setup a voltage controlled switch that turns off a relay on the output of the GT Inverter--When the battery is full, the GT inverter is shut down (open relay). This is known as "Bang Bang" control theory (100% on, then 100% off--sort of "bangs" against the stops). Also, because charge control failures are always possible, there should be two independent charge control systems to ensure that a single failure does not cause a fire/battery explosion.

Now--There are OG inverter manufacturers that are design/manufacturing equipment to use this method of charging batteries. SMA with their Sunny Island system. Very cool and well designed system (not cheap for use in the US). Basically, the OG AC Inverter varies the "micro grid" AC frequency--As the battery becomes fully charged the OG Inverter starts "dithering" the AC frequency of center from 50/60 Hz by a little bit (they go both above and below the center frequency--so that the average frequency is still to specifications--to keep clocks on time).

When connected to a standard GT inverter, when the frequency goes out of spec. the GT inverter shuts down and times out for 5 minutes. With their Sunny Island GT Inverter, their GT inverter starts to throttle back on output power and reduces output energy (very cool, and much better for battery bank charging).

And, Xantrex XW and some very new Magnum OG TSW Inverters are also using variable frequency control to knock the GT inverters off line (I think this is still bang bang control). You need a Sunny Island (or similar--if there are any out there) GT inverter for better charging control.

That is the basics.

Why would anyone do this? It uses an existing GT Inverter system + array for backup power (just need to add a large OG inverter and battery bank+charge control). It also can reduce wiring costs as it supports 120/240 VAC (as opposed to typical 18-100 VDC for most off grid power system) for high voltage distribution (could even use high voltage boost/buck AC transformers too for longer distances). And it makes an AC Micro grid where you can mix distributed generation (battery bank plus DC solar charging at home, a GT Inverter+AC load like well pump 100's of feet away, etc.) and local DC generation/battery bank.

In some ways, AC Coupled GT Inverters are a relatively simple installation if done with newer equipment (that has native support). But it does add complexity to the design and may not save any money--depending on specific site and user needs.

Hope that makes sense.

-Bill

kcmc68

Re: Newbie Solar System set up question

Guys, I want the solar system on a separate breaker from hydro, so think of it as we can switch between hydro and solar at a flick of a switch.

I think I only need a small to mid size system, simply because it's going to be in my backyard. Start at 500W, to a max of 1000W.

NorthGuy

Re: Newbie Solar System set up question

kcmc68 wrote: »

Guys, I want the solar system on a separate breaker from hydro, so think of it as we can switch between hydro and solar at a flick of a switch.

I think I only need a small to mid size system, simply because it's going to be in my backyard. Start at 500W, to a max of 1000W.

If you do it this way then when you flip the switch to solar all your loads must be supported by your system (that is by your batteries). It's really hard to accomplish with such small system.

Cariboocoot

Re: Newbie Solar System set up question

To give you some idea of what to expect from 500 Watts of panel on a battery system:

500 Watts * 4 hours good sun * 0.52 over-all system efficiency = 1040 Watt hours per day.

The batteries would probably be about 320 Amp hours @ 12 Volts, enough for about 1600 Watt hours maximum.

This would just about keep an average refrigerator running.

There are quite a few variations on this theme possible, mostly depending on how you intend to use the power. It is not at all unusual to have a system like this with a transfer switch (often built in to the inverter) for backing up power to critical loads in the event of an outage: under normal use the grid power feeds everything (sometimes including a charger for the batteries). When the grid goes down the transfer switch is engaged (either manually or automatically) and the batteries & inverter supply the power.

BB.

Re: Newbie Solar System set up question

The usual setup is to have a "protected" sub panel. Just a few circuits (fridge, lighting, a few outlets, etc.) so you can have emergency backup power.

Some are setup so you can pick and choose your backed up circuits (fridge always on backup, but turn off to use the microwave or well pump, etc.).

Backing up the entire hone can be cone, but it is not cheap. So it depends on your needs.

-Bill

gww1

Re: Newbie Solar System set up question

Bill

Hope that makes sense.

-Bill

Some of it makes sence. I had thought that with a double run of wire "200 foot" to support to solar arays to two charge controllers that I can send about 90 volts to, it might be nice to be able to do it with 600 volts. I was thinking if a person went from 5000w of solar panel to say 8000w it might be easier to exspand. I thought that maby it could be done with fewer charge controllers for large arays.

Would the outback gvfx 3648 provide the hertz/voltage to run a grid tie inverter and would it accept the power back to charge the batteries? If it would work then the grid tie that would be coupled with it would have to be 7200w as that is what the two outbacks are. One charge controller with a relay to turn the gridtie inverter off and on based on voltage?

Don't get me wrong, I realize that new large gt inverters cost large money. Also if the outback wouldn't work I probly wouldn't replace. Mostly I am just trying to learn what can and cannot be done. I bought some used equipment and it might not last or work and I would like to learn my options and just to know. I am a sort of a,b,c type of guy. In other words I may need more "this fits here and that goes there" then I do theory.

I am thinking by you explination that the outback would not allow ac power to push back through its ac output. When looking at off grid inverters, what on their spec sheet would indicate that it would work in the fasion you explain if I even understand at all. I will read it again.
Thanks
gww

NorthGuy

Re: Newbie Solar System set up question

gww1 wrote: »

I had thought that with a double run of wire "200 foot" to support to solar arays to two charge controllers that I can send about 90 volts to, it might be nice to be able to do it with 600 volts.

Have you thought about using XW MPPT80-600? It can handle 600V and you only need #10 wire.

This is much cleaner solution, and doesn't require dangereous GT inverters.

Cariboocoot

Re: Newbie Solar System set up question

NorthGuy wrote: »

Have you thought about using XW MPPT80-600? It can handle 600V and you only need #10 wire.

This is much cleaner solution, and doesn't require dangereous GT inverters.

What's dangerous about a GT inverter? In a way they would be less dangerous because the long run would be at 240 VAC, which is easier to control than the >240 VDC from panels.

The main problem with AC coupling is the limited number of off-grid inverters that can be used this way. There is also a slight drop in efficiency in converting from DC (panels) to AC (GTI) then back to DC (OGI) to charge the batteries.

gww1

Re: Newbie Solar System set up question

Northguy
I actually saw that being discussed in anouther thread and I believe all the equipment with it was mentioned to be about $1200 and my wire is going to cost that much not counting the combiner box which I have already bought. I have not looked it up yet. It does sound cheeper even with me only needing to buy wire as I already have charge controllers. I just bought the fm80 cc. I wanted to try the midnite classic but got hung up on plugging into the outback hub ten for comunication between componants. I didn't know that charger existed when I got my stuff. It might still be cheeper to look into it even though wire is all I now need. I am going to look it up but off hand will it handle 5640w PV to a 48 volt battery bank?
Thanks
gww

I looked it up. 4800w max

Cariboocoot

Re: Newbie Solar System set up question

5640 Watts / 48 Volts = 117.5 Amps. With typical derating 90 Amps.
There is no charge controller that will handle that power (MidNite Classic will not do 90 Amps @ 48 Volts).

NorthGuy

Re: Newbie Solar System set up question

gww1 wrote: »

I am going to look it up but off hand will it handle 5640w PV to a 48 volt battery bank?

By docs, it can handle 4800W output, which translates to 5000W array. Dave Sparks (member of this forum) uses them frequently and it says the charger can go to 95A if not hot. He says:

Dave Sparks wrote: »

If you are not in the desert with a ambient of 90F, the unit can output 90 amps all day long. As the circuitry heats up from air temp or just being at alot higher than rated current the output will current limit. I have seen 95 amp peaks with cloud effect.

That would be enough for 5600W array.

gww1

Re: Newbie Solar System set up question

Yea I looked it up. I aready had an mx60 when I considerred adding the midnite clasic.
gww

gww1

Re: Newbie Solar System set up question

Thanks all for the comments. I will probly stick to the path I am on and see how I like it. I am trying to learn though. Thanks for the help.
gww

Cariboocoot

Re: Newbie Solar System set up question

Yep, that's the spirit: run everything right at the edge or even a bit over. Who needs margins?

kcmc68

Re: Newbie Solar System set up question

BB. wrote: »

The usual setup is to have a "protected" sub panel. Just a few circuits (fridge, lighting, a few outlets, etc.) so you can have emergency backup power.

Some are setup so you can pick and choose your backed up circuits (fridge always on backup, but turn off to use the microwave or well pump, etc.).

Backing up the entire hone can be cone, but it is not cheap. So it depends on your needs.

-Bill

Just as you suggested, I only want to have essentials for emergency backup power. Only lighting, fridge etc.

I want to be able to directly use the solar power generated during the daytime. In the case where it is not enough, I want hydro power to supply the remaining to ensure I have enough overall power to power the load.

On another note, how many batteries should I get for a 500 W system? If I expand to 1000 W in the future, how much more will I need? What should the battery total amperes be? What type of charge controller would you recommend that will support 500 W, but will also allow me to expand to 1000 W in the future?

Thanks.

Mark