Solar power questions

SunshineHarvey7 · January 3, 2021

I have a friend who just purchased a 20+ rai of land with 3 dwellings, 1km from his light meter and village. With less than 7 amps of load (based on my clamp-on meter near his main breaker), his voltage drops to around 150 volts! So he's seriously looking at converting to a solar off-grid system rather than putting a lot of money into running high-voltage wire to his property and getting a transformer near his house. So I have a few questions, as I'm trying to help him plan a system. I don't yet have an inventory list of all the stuff he may want to use, so these are general questions to start with.

1. If he needs a system that provides more than 5kw, is it possible to connect two or more inverters in parallel to provide the load? If so, what special terms do I look for to find that kind of inverter? (I'm sure I can't do that with just the simple basic inverter.) Is there a separate piece of equipment that is needed to connect the two inverters together and/or balance the load? And would one of the inverters be a "master" inverter that sets the 50hz rate that the other inverter(s) would sync to?

2. Does it make sense to intentionally build a system with smaller inverters so that if one goes down you can fall back on using the good one?

3. Regarding batteries, does anyone on this forum have experience using batteries for forklifts or other such equipment? How do they compare with Gel-cells or other deep-cycle batteries?

4. To get a decent lifetime out of a gel-cell or deep-cycle battery, some people (including https://unboundsolar.com/solar-information/deep-cycle-battery-info) recommend a depth of discharge (DOD) of not more than 50-80% to get a good life and not damage the battery. Am I correct in understanding that this means that I should plan to get 100-160AH of use out of a 200AH battery?

5. Is there a way to program any of the inverters to shut off or set off an alarm when the batteries get to a certain DOD?

6. I would like to suggest to my friend that he start with a system around 3kw or 5kw and then grow the system as needed. (They aren't using any A/C, and most of the cooking would be with propane, so I think such a system may be a good start at least.) Am I correct in assuming that we should plan to grow the system in a "modular" fashion (sorry, maybe there's a better term here), with each "module" having its own set of panels and charge controller and an inverter that can be tied in? (Of course, this relates directly to question #1 above.)

These friends are caring for some children and plan to add facilities in the future. So I'm trying to help them plan a system that can grow with their needs. (Another approach is to add new independant solar systems for later buildings, but I assume such an approach isn't necessary.)

Thanks in advance for any "light" you can shed on these questions! (I've read quite a bit of the solar threads on the ThaiVisa forum, but please let me know if there's a thread that should answer most/all of these questions.)

BritManToo · January 3, 2021

1 hour ago, SunshineHarvey7 said:

4. To get a decent lifetime out of a gel-cell or deep-cycle battery, some people (including https://unboundsolar.com/solar-information/deep-cycle-battery-info) recommend a depth of discharge (DOD) of not more than 50-80% to get a good life and not damage the battery. Am I correct in understanding that this means that I should plan to get 100-160AH of use out of a 200AH battery?

Life and storage capacity of deep cycle gel/wet batteries depends on load and discharge level.

Most batteries are rated at a discharge period of 20hrs.

So a 100ah 12v battery can provide 5a for 20hrs = 60w (not a lot)

At 50% discharge they will work for 2,000 cycles.

At 80% discharge that drops to 1,000 cycles.

I worked out my entertainment (350w) system needed 4x 150ah (4 x 90w) batteries to work at their rated discharge.

(that's 30,000bht in batteries which will need replacing every 3-5 years)

What is your projected average load?

(5kw =5,000w would need a fortune in batteries, 200ah = 120w, 1200kw = 10 batteries = 100,000bht)

A generator is a far better bet than a small fortune for batteries at this current time IMHO.

And probably a lot cheaper (including the fuel).

But a Solar system for running a few LED lights at night, is entirely feasible.

Edited January 3, 2021 by BritManToo

SunshineHarvey7 · January 3, 2021

3 minutes ago, BritManToo said:

Life and storage capacity of deep cycle gel/wet batteries depends on load.

Most batteries are rated at a discharge period of 20hrs.

So a 100ah 12v battery can provide 5a for 20hrs = 60w (not a lot)

At 50% discharge they will work for 2,000 cycles.

At 80% discharge that drops to 1,000 cycles.

I worked out my entertainment (350w) system needed 4x 150ah batteries to work at their rated discharge.

What is your projected load?

Thanks for your input. I'm still working on estimating the projected load. Right now, I'm trying to make sure I'm understanding the basic principles.

So, you would aim to not exceed 50% DOD on a typical day, right?

BritManToo · January 3, 2021

5 minutes ago, SunshineHarvey7 said:

So, you would aim to not exceed 50% DOD on a typical day, right?

I would plan not to exceed 50% discharge at the rated load 200ah 12v battery has a rated load of 10a = 120w.

10 x 200ah Globatt Inva batteries, could provide 1200w for 10hrs (50%) = 100,000bht for the batteries.

In comparison a 3kva generator can be had for 7,000bht.

Edited January 3, 2021 by BritManToo

Trujillo · January 3, 2021

"A generator is a far better bet than a small fortune for batteries at this current time IMHO."

Isn't a generator really loud?

sandyf · January 3, 2021

47 minutes ago, SunshineHarvey7 said:

Thanks for your input. I'm still working on estimating the projected load. Right now, I'm trying to make sure I'm understanding the basic principles.

So, you would aim to not exceed 50% DOD on a typical day, right?

Yes you really need to try and understand what is going on to come up with the best solution.

Unfortunately there is a variable that there is no control over, sunshine. When considering battery discharge you have to bear in mind that when the sun is shining, the battery is being charged as it discharges so the battery does not need to meet the full load.

Obviously the problem comes during cloudy weather and darkness and many systems fall back on the mains.

Instead of using the mains direct, it may be possible to look at converting the mains down to around 20v DC and effectively using it as a substitute solar panel. I would think that the variance on the DC output would be within working parameters.

Not a course of action that would normally be considered, but unusual circumstances often require unusual solutions. Good luck.

Crossy · January 3, 2021

1 hour ago, Trujillo said:

"A generator is a far better bet than a small fortune for batteries at this current time IMHO."

Isn't a generator really loud?

50k Baht will get you a 5kVA "silent" diesel genset, but they're really aimed at backup power rather than 100% operation.

Task "A" is to determine the daily consumption (which will size your panels and batteries), Task "B" is to determine the peak loading (which will size your inverter).

That there is actually a mains connection available at the site (no matter how feeble) gives some options for going hybrid (mostly off-grid but with at least some backup power).

To respond to the questions as asked:-

1. Plenty of inverters available which can be linked in parallel, usually up to about 6 which would give you 30kVA.

2. Multiple smaller inverters does give you at least some power if you lose one.

3. Unless you can get forklift or similar batteries at a really good price...

4. With lead-acid you need to get at least double the capacity you calculate, LiFePO4 is nearly on a par cost wise now.

5. Pretty well any inverter will do this.

6. Certainly start small, but you need to actually calculate what you need.

Some useful stuff in this thread:-

SunshineHarvey7 · January 3, 2021

42 minutes ago, sandyf said:

Yes you really need to try and understand what is going on to come up with the best solution.

Unfortunately there is a variable that there is no control over, sunshine. When considering battery discharge you have to bear in mind that when the sun is shining, the battery is being charged as it discharges so the battery does not need to meet the full load.

Obviously the problem comes during cloudy weather and darkness and many systems fall back on the mains.

Instead of using the mains direct, it may be possible to look at converting the mains down to around 20v DC and effectively using it as a substitute solar panel. I would think that the variance on the DC output would be within working parameters.

Not a course of action that would normally be considered, but unusual circumstances often require unusual solutions. Good luck.

Yes, I will have to consider that we will get much less power from the panels in the rainy system. I wonder whether @BritManToo or @Crossy or anyone else can share how much their panels dropped in performance during the rainy season. Down to 50%? 30%?

Since we do have limited electric service, we may consider a hybrid system that is assisted by line power esp during the rainy season. Right now, the line voltage drops so much with a load more than a few amps, any heavy loads are impossible; however, if we had a decent battery bank, I'm realizing that we could manage short-term heavy loads (determined by inverter size), and line power could help recharge. A steady current of only 3A @ 190V (after line loss) = 570 watts x 24 hours = ~13.5 kwh. (If Crossy and BritManToo are correct, to provide this amount of power it would take at least 13 330-watt solar panels on an average sunny day.)

2 hours ago, Trujillo said:

"A generator is a far better bet than a small fortune for batteries at this current time IMHO."

Isn't a generator really loud?

Noise is a small consideration. As @Crossy said, we might consider a generator for unusually high demands, but it doesn't cost-effective to rely on a generator as our primary power source.

SunshineHarvey7 · January 3, 2021

1 hour ago, Crossy said:

Some useful stuff in this thread:-

@Crossy, can you re-post the link to the helpful thread?

BritManToo · January 3, 2021

5 minutes ago, SunshineHarvey7 said:

Yes, I will have to consider that we will get much less power from the panels in the rainy system. I wonder whether @BritManToo or @Crossy or anyone else can share how much their panels dropped in performance during the rainy season. Down to 50%? 30%?

October was very wet in CM, my 5 panels produced 117 units.

December totally dry, 149 units ........... so down to 78% in the three wettest months August/September/October.

Quite frankly, if I were you and only needed to boost the mains .........

I'd try 3x 340w panels and a 1000w GTi, total cost around 11,000bht and see how it goes.

That's about a 2A boost, what's great about distributed power generation, is you can just plug another in if you need it.

That would probably bring your voltage up to 220v in the day, as the grid wouldn't need to supply much current.

And whatever the result, you've got equipment you can still use if you need to buy more.

Edited January 3, 2021 by BritManToo

Crossy · January 3, 2021

2 minutes ago, SunshineHarvey7 said:

@Crossy, can you re-post the link to the helpful thread?

https://forum.thaivisa.com/topic/1198488-how-do-i-size-a-solar-power-system/

Crossy · January 3, 2021

We have 5.8kW of installed panels.

In the last 6 months (all I have records for) the best day gave us 32kWh, the worst 6kWh.

mahjongguy · January 3, 2021

When you've come up with a plan for solar, before you can make a decision, you will need an accurate estimate of PEA charges to simply provide a nearby transformer. That can take a while, so best to get the process started if you haven't already.

Crossy · January 3, 2021

12 hours ago, BritManToo said:

Quite frankly, if I were you and only needed to boost the mains .........

I'd try 3x 340w panels and a 1000w GTi, total cost around 11,000bht and see how it goes.

That's about a 2A boost, what's great about distributed power generation, is you can just plug another in if you need it.

That would probably bring your voltage up to 220v in the day, as the grid wouldn't need to supply much current.

And whatever the result, you've got equipment you can still use if you need to buy more.

My only worry would be that that GTI (Grid Tie Inverter for those who don't know) may object to the rather feeble "220V" supply.

It's certainly worth a shot and if it doesn't work out you still have the panels.

SunshineHarvey7 · January 4, 2021

2 hours ago, Crossy said:

My only worry would be that that GTI (Grid Tie Inverter for those who don't know) may object to the rather feeble "220V" supply.

How easy can a person find out what voltage range a GTI will work with before purchasing it? I am concerned that there are very few specs given for most solar equipment sold via Lazada.

I suppose an AVR (automatic voltage regulator) might help if needed.

Crossy · January 4, 2021

The Suoer units seem to have a good reputation at the lower end of the price bracket. The manufacturer's website says 190-260V for the 1kW unit, our Sofar 6kW unit is specified down to 180V.

To be honest it's probably going to be "suck it and see", much depends upon just how the mains supply actually behaves.

I wouldn't try putting a GTI on the regulated side of an AVR, the GTI pushes power into the network by slightly raising it's output voltage vs grid voltage which could confuse an AVR.

Going off grid with mains backup (so you can get away with smaller batteries) is guaranteed to work but is going to cost rather more $$$. Have a look at this thread https://forum.thaivisa.com/topic/1198488-how-do-i-size-a-solar-power-system/

Is this going to be a DIY job or employ a contractor?

SunshineHarvey7 · January 4, 2021

18 minutes ago, Crossy said:

I wouldn't try putting a GTI on the regulated side of an AVR, the GTI pushes power into the network by slightly raising it's output voltage vs grid voltage which could confuse an AVR.

Going off grid with mains backup (so you can get away with smaller batteries) is guaranteed to work but is going to cost rather more $$$. Have a look at this thread https://forum.thaivisa.com/topic/1198488-how-do-i-size-a-solar-power-system/

Is this going to be a DIY job or employ a contractor?

I really doubt we will ever try to push power back into the grid, so, ...

1. Tchnically we should be looking for a "hybrid" inverter (if I understand correctly that hybrid means the batteries can be charged by solar or by the grid). Is that right?

2. In this context, does it make sense to use an AVR? Honestly, I have no idea what an AVR <= 1kw can cost.

3. If it doesn't make sense to use network power to help charge the batteries when the panels don't keep up with the demand (since our grid feed seems to drop about 10V for every 1A of load), I guess a generator is an option, right? (Noise would not be an issue in this case.) Does it make sense to size the generator to use its full capacity for charging when it's running to get the most power for the fuel used? Hope that makes sense.

Thanks for the link re sizing a solar system. I'm sure it will be helpful. We are aiming for this to be DIY as much as possible.

Crossy · January 4, 2021

Something like this would do the trick (Note this is not a recommendation for this particular unit).

https://www.lazada.co.th/products/hybrid-off-grid-inverter-5000w-wifi-sun-d-inverter-i1940978696-s6148390588.html

Parallel up to 9 units, grid / genset backup for those dull days.

I wouldn't bother with an AVR, at least not at first, although you could price one from my AVR thread https://forum.thaivisa.com/topic/1008193-installing-an-automatic-voltage-regulator-avr/

If you go with a genset, size it to run between 60% and 70% of the specified output for best efficiency and reliability. Again I'd start with the hybrid solar and a reasonably sized battery (easy to add more battery and panels), add a genset later if necessary.

Is major consumption going to be during the day or the night (battery sizing)?

BritManToo · January 4, 2021

1 hour ago, SunshineHarvey7 said:

How easy can a person find out what voltage range a GTI will work with before purchasing it? I am concerned that there are very few specs given for most solar equipment sold via Lazada.

I suppose an AVR (automatic voltage regulator) might help if needed.

The SuOER 1000w GTIs I use cost 2,500bht .......... it's not a lot of money to risk.

https://www.lazada.co.th/products/suoer-grid-tie-inverter-1000va-gti-d1000b-i1330154723-s3319062846.html

Edited January 4, 2021 by BritManToo

SunshineHarvey7 · January 4, 2021

4 minutes ago, BritManToo said:

The SuOER 1000w GTIs I use cost 2,500bht .......... it's not a lot of money to risk.

How many of those SuOER GTIs can I gang together if I want, say, a 5kw or 6kw system?

And can those GTIs be set up as a "hybrid" inverter--being able to charge off the grid but not feed power back into the grid? (reasons already explained above)

How long have you been using your SuOER GTIs?

SunshineHarvey7 · January 4, 2021

16 minutes ago, Crossy said:

Something like this would do the trick (Note this is not a recommendation for this particular unit).

https://www.lazada.co.th/products/hybrid-off-grid-inverter-5000w-wifi-sun-d-inverter-i1940978696-s6148390588.html

Parallel up to 9 units, grid / genset backup for those dull days.

I wouldn't bother with an AVR, at least not at first, although you could price one from my AVR thread https://forum.thaivisa.com/topic/1008193-installing-an-automatic-voltage-regulator-avr/

If you go with a genset, size it to run between 60% and 70% of the specified output for best efficiency and reliability. Again I'd start with the hybrid solar and a reasonably sized battery (easy to add more battery and panels), add a genset later if necessary.

Is major consumption going to be during the day or the night (battery sizing)?

I'm guessing most of the usage will be during the day.

Thanks for the tips on the hybrid inverter and genset.

I'll probably have more questions for y'all later! ????

BritManToo · January 4, 2021

25 minutes ago, SunshineHarvey7 said:

How many of those SuOER GTIs can I gang together if I want, say, a 5kw or 6kw system?

And can those GTIs be set up as a "hybrid" inverter--being able to charge off the grid but not feed power back into the grid? (reasons already explained above)

How long have you been using your SuOER GTIs?

I've had a 600w one going for18 months with 2 x330w panels.

and a 1000w one going for 6 months with 3x 340w panels.

The only limit to the number you can use, is the number of available sockets in your house.

Why would you care about feeding spare power back to the grid? worse case is they install a digital meter, and keep any free power you provide them.

I also have a SUOER 1000w pure sine wave inverter + 100ah Globatt INVA deep cycle battery between the mains and my entertainment system (350w max load) to sort out all those little power cuts that happen frequently in Thailand. I know I stress the battery horribly (30a when it should only provide 5a) but it's only used for an hour now and again, so I'm not that worried about it's battery life.

https://shopee.co.th/Suoer-อินเวอร์เตอร์-off-grid-Model-PL-1.5KA-12V-12V-1-500KVA-มี-AC-Charge-220V-ปรับโหมดการทำงาน-3-ระบบ-i.270985842.6451843458

Edited January 4, 2021 by BritManToo

SunshineHarvey7 · January 4, 2021

19 minutes ago, SunshineHarvey7 said:

can those GTIs be set up as a "hybrid" inverter--being able to charge off the grid but not feed power back into the grid? (reasons already explained above)

Basic question here--are all GTIs the same as a hybrid but with the OPTION of being able to feed power back into the grid AND the option of working with batteries or without (daytime use only)? (Are all GTIs set up to be able to NOT feed power back into the grid? And are all GTIs able to work with batteries?)

BritManToo · January 4, 2021

15 minutes ago, SunshineHarvey7 said:

Basic question here--are all GTIs the same as a hybrid but with the OPTION of being able to feed power back into the grid AND the option of working with batteries or without (daytime use only)? (Are all GTIs set up to be able to NOT feed power back into the grid? And are all GTIs able to work with batteries?)

GTIs only take power from solar panels and feed into the grid at the same frequency and voltage.

No AC on your grid = no power generated by the GTi.

Hybrid inverters do everything but appear (to me) to be overpriced (7kbht and up).

I have no real need for them, unless TEOTWAWKI approaches.

My local PEA is my battery, until battery technology vastly improves, and the price vastly reduces.

I have solar for two reasons.

1. Reduce my electricity bill.

2. Provide seamless power for my PC/xbox/TV/NAS/Fibre internet when the PEA ducks out for a second/minute/hour.

Edited January 4, 2021 by BritManToo

SunshineHarvey7 · January 6, 2021

On 1/3/2021 at 5:28 PM, BritManToo said:

October was very wet in CM, my 5 panels produced 117 units.

December totally dry, 149 units ........... so down to 78% in the three wettest months August/September/October.

@BritManTooDid I understand correctly that you live in the Chiang Mai area? I'm curious how the smoky season affects the performance of your panels -- or anyone else's. I'm guessing performance drops by at least 20%.

BritManToo · January 6, 2021

3 hours ago, SunshineHarvey7 said:

@BritManTooDid I understand correctly that you live in the Chiang Mai area? I'm curious how the smoky season affects the performance of your panels -- or anyone else's. I'm guessing performance drops by at least 20%.

Makes no significant difference.

maxpower · January 6, 2021

3 hours ago, SunshineHarvey7 said:

@BritManTooDid I understand correctly that you live in the Chiang Mai area? I'm curious how the smoky season affects the performance of your panels -- or anyone else's. I'm guessing performance drops by at least 20%.

Air pollution is choking solar energy around the world | Popular Science (popsci.com)

BritManToo · January 7, 2021

On 1/4/2021 at 10:25 AM, SunshineHarvey7 said:

How long have you been using your SuOER GTIs?

My 600w Suoer stopped working after 18 months.

it was totally dead this morning, PV inputs reading 0.2V, all the lights and meters off.

unplugged everthing, solar panels both 40v, put them back on the wire not plugged into the GTI, still 40v.

Plugged everything back together, switched it on and it's all working again, worked all day.

GTi meter has counted 42hrs this month ....... while the other GTI meter has counted 70hrs ........ so it had stopped working for around 3 days without me noticing.

How very odd, that cost me 5KWhr.

SunshineHarvey7 · January 7, 2021

53 minutes ago, BritManToo said:

My 600w Suoer stopped working after 18 months.

it was totally dead this morning, PV inputs reading 0.2V, all the lights and meters off.

unplugged everthing, solar panels both 40v, put them back on the wire not plugged into the GTI, still 40v.

Plugged everything back together, switched it on and it's all working again, worked all day.

GTi meter has counted 42hrs this month ....... while the other GTI meter has counted 70hrs ........ so it had stopped working for around 3 days without me noticing.

How very odd, that cost me 5KWhr.

Hmmm. No clue why it stopped? No error or fault codes? Strange. Must be getting close to the end of the warranty! ????

Crossy · January 7, 2021

These things happen, turn it off and back on again and it's fine. Just pray the software chaps aren't moonlighting from Airbus.

The more expensive systems with remote monitoring allow you to check, er, remotely, if anything is awry.

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