38 minutes ago, Pink7 said:

Hi Bandersnatch. Can you share some info on Inverter and battery capacity vs ability to fully offgrid? 

 

Pink

I'm sure B will chime in.  

 

I can give you our short experience (since 4 Aug 2022), and with the best & worst sun conditions. 

 

Based our system on PEA monthly usage at rental townhouse w/ 1 sm AC.   Used 600-700 units  / kW a month.  Better house build and components, and we haven't broke 600 kW a month yet.  That's w/ 2 larger ACs, but very efficient inverters.

 

8kW hybrid inverter, w/20 kW ESSs.  Started with 10 kW ESS, then paralleled a 2nd in.  We are basically off grid.   Don't think with our usage, we could do it with 5kW inverter & 10kW ESS, as really a bit limiting, and would need to be super conservative, on the week of krap weather; heavy overcast & rain.

 

Some days it took all day, to top up the ESS (10kw), and not always 100%.   With minimal use, although, since so overcast, ACs really not needed.  One reason we added the 2nd ESS, along with having a digital PEA meter, so no roll back for us.

 

Good days, ESSs top up in 2-3 hrs, all of 10+kW, as we don't go below 50% on ESSs / 10kW of 20kW that we have.

 

If haven't seen yet, link below for our system:

https://aseannow.com/topic/1268214-solar-8kw-hybrid-inverter-w10kwh-upgraded-to-20kwh-in-sept-2022-essbattery-not-diy/

 

2 hours ago, Pink7 said:

Hi Bandersnatch. Can you share some info on Inverter and battery capacity vs ability to fully offgrid? 

 

Pink

I have been planning to do a video on this for some time, but I am not sure how to make it without me just talking over a bunch of numbers on a  spreadsheet.

 

First thing to do is to determine what load you need to cover from the batteries. I use a device with CT clamps to monitor power use by the house and a second for my EV charging. An easy example would be assuming a 1kW load all night. (This is just an assumption for example purposes only)

 

 

 

Next determine how many hours will the house be running off batteries, this will vary from summer to winter. It is best to ignore the first and last hour of the day that your solar is producing.

 

 

 

 

So let's assume 14 hours need to be covered at 1kW usage i.e. 14kWh.  Let's assume you initially plan to buy 2x9kWh lithium batteries =18kWh you would probably think that this would easily cover night time usage of 14kWh

 

First thing to consider is depth of discharge. Lithium is normally good for 80% DOD so your 18kwh is now down to 14.4kWh. However, your inverter may have it's own idea of what the DOD of your batteries should be. The Growatts stop discharging from Li batteries when they get to 22% state of charge (setting #12) 18kWh x 78% = 14.04kWh.

 

 

Next you have to consider the efficiency of the inverter. There is always some efficiency loss when converting from DC to AC.

 

 

The Growatts have a peak efficiency of 93% - it may drop lower than this but let's use 93% for now. 14.04kWh x 93% = 13.06kWh

 

 

Another factor that is often overlooked is that the inverters require power to run and this is not included in the inverting efficiency. The power used by the inverters is not included in the household load calculations. which is measured after power has been sent from the inverters.

 

 

 

 

60 Watts, so 2 inverters would use 120 Watts per hour x 14 hours  =1.68kWh 

 

13.06kWh - 1.68kWh = 11.38kWh useable power from 2x9kWh lithium batteries over 14 hours. So you probably need 3 and not 2 x 9kWh batteries. 

23 minutes ago, Bandersnatch said:

I have been planning to do a video on this for some time, but I am not sure how to make it without me just talking over a bunch of numbers on a  spreadsheet.

 

First thing to do is to determine what load you need to cover from the batteries. I use a device with CT clamps to monitor power use by the house and a second for my EV charging. An easy example would be assuming a 1kW load all night. (This is just an assumption for example purposes only)

 

 

 

Next determine how many hours will the house be running off batteries, this will vary from summer to winter. It is best to ignore the first and last hour of the day that your solar is producing.

 

 

 

 

So let's assume 14 hours need to be covered at 1kW usage i.e. 14kWh.  Let's assume you initially plan to buy 2x9kWh lithium batteries =18kWh you would probably think that this would easily cover night time usage of 14kWh

 

First thing to consider is depth of discharge. Lithium is normally good for 80% DOD so your 18kwh is now down to 14.4kWh. However, your inverter may have it's own idea of what the DOD of your batteries should be. The Growatts stop discharging from Li batteries when they get to 22% state of charge (setting #12) 18kWh x 78% = 14.04kWh.

 

 

Next you have to consider the efficiency of the inverter. There is always some efficiency loss when converting from DC to AC.

 

 

The Growatts have a peak efficiency of 93% - it may drop lower than this but let's use 93% for now. 14.04kWh x 93% = 13.06kWh

 

 

Another factor that is often overlooked is that the inverters require power to run and this is not included in the inverting efficiency. The power used by the inverters is not included in the household load calculations. which is measured after power has been sent from the inverters.

 

 

 

 

60 Watts, so 2 inverters would use 120 Watts per hour x 14 hours  =1.68kWh 

 

13.06kWh - 1.68kWh = 11.38kWh useable power from 2x9kWh lithium batteries over 14 hours. So you probably need 3 and not 2 x 9kWh batteries. 

Thanks for that info Bandersnatch. Your inverters is not connected to the grid if i have understood correct? 

 

Pink

4 minutes ago, Pink7 said:

Thanks for that info Bandersnatch. Your inverters is not connected to the grid if i have understood correct? 

 

Pink

I pay ฿40 a month to have access to PEA if I need it, but most of the time PEA is switched off at the breaker

1 hour ago, Bandersnatch said:

I pay ฿40 a month to have access to PEA if I need it, but most of the time PEA is switched off at the breaker

@Pink7

As is ours, though as B is, we're still conx to PEA.  I think this month will have -0- use, or maybe 1 kW/unit, as wouldn't want them to think it's broke and replace it.   Though they may screw up and give us a 'spinning' meter.    That would be nice.

 

Past couple months, our PEA bill was about 20 units and around the 100 baht mark.   As we have an EV, and new wall charger (7.4kW) for that, which is on the grid.  Did test and use a couple times, hence the past couple usage bills from PEA.  Unless needing a fast top up for the EV, we won't be using the EV wall charger, or the grid at all in the future.

 

 

12 minutes ago, KhunLA said:

@Pink7

As is ours, though as B is, we're still conx to PEA.  I think this month will have -0- use, or maybe 1 kW/unit, as wouldn't want them to think it's broke and replace it.   Though they may screw up and give us a 'spinning' meter.    That would be nice.

 

Past couple months, our PEA bill was about 20 units and around the 100 baht mark.   As we have an EV, and new wall charger (7.4kW) for that, which is on the grid.  Did test and use a couple times, hence the past couple usage bills from PEA.  Unless needing a fast top up for the EV, we won't be using the EV wall charger, or the grid at all in the future.

 

 

Thats  nice that you able to reduce PEA to near zero. I want to try run my Growatt inverters without grid connect for less chance for any issues so i try double check my plans before next step. My plan is 9.5 kw panels and 26kw (2 x280A 48v) battery. We currently use 20-25kw per day from PEA. How this will ad up ..or not with different weather types i dont have much idea on..Time will show.

 

Pink

 

Pink

34 minutes ago, Pink7 said:

How this will ad up ..or not with different weather types i dont have much idea on

The last time I drew power from the grid was during Super Typhoon Noru in September last year. 3 hours after I started to use grid power the grid went down for 8 hours.

 

 

 

50 minutes ago, Bandersnatch said:

The last time I drew power from the grid was during Super Typhoon Noru in September last year. 3 hours after I started to use grid power the grid went down for 8 hours.

 

 

 

Smart that you have grid opportunity on inverters and jus enable it when needed.

 

Pink

On 1/12/2023 at 7:04 PM, Bandersnatch said:

The last time I drew power from the grid was during Super Typhoon Noru in September last year. 3 hours after I started to use grid power the grid went down for 8 hours.

 

 

 

With grid in to inverter turned off on breaker you still connected to grid ground/earth?

 

Pink

1 hour ago, Pink7 said:

With grid in to inverter turned off on breaker you still connected to grid ground/earth?

 

Pink

Yes, as the breaker box on the wall inside house is the grounding, to earthing rod.   We have a breaker on the inside of the perimeter wall, about 2 meter length of wire from the PEA meter.  That's where I turn off the grid.

 

Then on the breaker box, it has the lead in for grid and solar, with their own breakers, incase you wish to turn one off.   Some folks without solar, will dedicate the other breaker to an external generator.

 

With that, the house should be grounded, hopefully avoid any electrocutions from appliance.   Though all bets off, if house hit by lightening.  Not a whole lot will protect you from that, except luck.  If so, hopefully not too much gets fried, component wise.

 

ESSs for us, igniting, would be the biggest issue, as they are located indoors, in the entrance foyer ????

46 minutes ago, KhunLA said:

ESSs for us, igniting, would be the biggest issue, as they are located indoors, in the entrance foyer ????

 

If they are LiFePO4 rather than Li-ion there's very little risk of them going into thermal-runaway ???? 

48 minutes ago, KhunLA said:

With that, the house should be grounded, hopefully avoid any electrocutions from appliance. 

Would point out modern hybrid inverters are very quick to turn themselves off in the event of a problem. 

My kid managed to short out her bedroom socket shortly after I installed the system.

All the electricity was turned off and alarms blaring before any breakers flipped.

2 hours ago, Pink7 said:

With grid in to inverter turned off on breaker you still connected to grid ground/earth?

 

Pink

My solar system and house electrics have separate ground rods.

11 minutes ago, Bandersnatch said:

My solar system and house electrics have separate ground rods.

I has start thinking about doing same. Do you have same ground for inverters and surge arresters or they are separate grounds?

 

Pink

15 hours ago, Pink7 said:

I has start thinking about doing same. Do you have same ground for inverters and surge arresters or they are separate grounds?

 

Pink

A ground rod was installed when my first solar system was fitted. My installer added a second when my system was expanded in 2021. I can’t remember now what the setup was, sorry. 

Quick summary of the cost of my system and payback

 

Payback:
Main Components
20,000 Watts of PV @ ฿9/W = ฿180,000
9kWh LiFePO4 Batteries ฿68,000 x 3 = ฿204,000
Inverters ฿36,000 x 3 = ฿108,000
= ฿492,000
 
Savings: 
Gasohol saving ฿5,000/month
PEA saving ฿3,500/month
= ฿8,500/month 

฿102,000/Year saving 
Payback = 5 Years

 

these figures are over a year old so have changed a bit.

2 hours ago, Bandersnatch said:

Quick summary of the cost of my system and payback...
... Payback = 5 Years

Those of us with solar, really can't emphasis enough, that everyone, if possible, should have some version of a solar system, no matter how small or large, on or off grid, or mix/hybrid.  

 

Our monthly bills at rental w/PEA ran between ฿3000-3500 a month for 600-700kW / units.

 

At the house now, using solar, we just broke 600kW for first time, during this billing cycle.  Used 2kw of PEA this billing cycle.

 

I kind of overestimated our use, and a system larger than really needed, but also have EV now, which wasn't really planned when house designed.

 

฿3000-3500 for PEA savings

฿3000 for petrol savings vs ICE use

 

System cost ฿445k (installed), having ESSs for overnight

฿445k ÷ 6k = 74 months = 6+ yr ROI

Without the EV, maybe 10 yr ROI, as we haven't really used the ACs much since Aug 2022 installation.  That will increase Feb, Mar, Apr & May.

 

Our system:

https://aseannow.com/topic/1268214-solar-8kw-hybrid-inverter-w10kwh-upgraded-to-20kwh-in-sept-2022-essbattery-not-diy/

 

4 hours ago, Bandersnatch said:

Quick summary of the cost of my system and payback

 

Payback:
Main Components
20,000 Watts of PV @ ฿9/W = ฿180,000
9kWh LiFePO4 Batteries ฿68,000 x 3 = ฿204,000
Inverters ฿36,000 x 3 = ฿108,000
= ฿492,000
 
Savings: 
Gasohol saving ฿5,000/month
PEA saving ฿3,500/month
= ฿8,500/month 

฿102,000/Year saving 
Payback = 5 Years

 

these figures are over a year old so have changed a bit.

But the gasohol savings are not really (or not entirely) a result of installing solar. Even without installing solar, you could still have bought an EV replacing your THB 5k gasohol bill with lets say an additional THB 2k on your PEA bill for charging. 

 

In reality, only THB 2k of your savings on transportation costs is down to installing solar, the remaining THB 3k is because you invested in an electric vehicle. So your monthly savings from installing solar is THB 5.5k giving a payback time of 7.5 years.

 

Note, I don't know how many kWh you use driving, so the THB 2k I quoted is just an example.

7 minutes ago, Sophon said:

Note, I don't know how many kWh you use driving, so the THB 2k I quoted is just an example.

We had the MG ZS ICE for 2 years prior to getting the EV version.   Put shy of 20k kms on average those 2 years, so just shy of 40k kms when sold.

 

Didn't get best kpL, and averaged 10 kpl.

20k ÷ 10 kpL = 2000 X ฿35 = 70k ÷ 12 months = ฿5833 monthly

 

To be fair, half of our kms are out & about, overnight, but when local, we topped up the ICE twice a month, locally, unless overnighting somewhere afar..   Staying local, we energize 100% with solar at home.

 

Now I drive a lot more, locally, since it cost nothing, as long as less than 250 kms r/t, which we do now, since it's basically free, charging back at the house w/solar. 

 

Nothing while out for the day w/ICE, a view, coffee shop, a munch, is worth paying ฿875 (25 L X ฿35) to go to, locally.  Now we do.  Actually the best part of having the EV, as I'll actually explore locally.

 

When overnighting, and further destinations, Charging Station vs Petrol, much cheaper, but that's for another thread.

4 hours ago, Sophon said:

But the gasohol savings are not really (or not entirely) a result of installing solar. Even without installing solar, you could still have bought an EV replacing your THB 5k gasohol bill with lets say an additional THB 2k on your PEA bill for charging. 

 

In reality, only THB 2k of your savings on transportation costs is down to installing solar, the remaining THB 3k is because you invested in an electric vehicle. So your monthly savings from installing solar is THB 5.5k giving a payback time of 7.5 years.

 

Note, I don't know how many kWh you use driving, so the THB 2k I quoted is just an example.

The two questions I am always asked are:

 

1) how much was your solar?

 

2) how long before you get your money back?

 

Those are the two questions I have answered.  My answers are based on my personal circumstances. 

 

21 hours ago, Bandersnatch said:

The two questions I am always asked are:

 

1) how much was your solar?

 

2) how long before you get your money back?

 

Those are the two questions I have answered.  My answers are based on my personal circumstances. 

 

Talking about profit / Roi, it was never ever on my mind when I started with Solar.

 

People called me crazy when I installed (now 22) 2500 Lt water tanks to collect rain water to provide the House with Clean water (don't want a filter system for our well (no idea why, but I am just not to keen to have one) and trust rain water more then well water (and those filters)

 

Someone told me that I have water on a Industrial scale, but believe it or not 50k+ Lt of water are just enough for the dry period (will have approx 2-7 tanks left) as you use more water then you know it.

 

21 hours ago, MJCM said:

Talking about profit / Roi, it was never ever on my mind when I started with Solar.

 

People called me crazy when I installed (now 22) 2500 Lt water tanks to collect rain water to provide the House with Clean water (don't want a filter system for our well (no idea why, but I am just not to keen to have one) and trust rain water more then well water (and those filters)

 

Someone told me that I have water on a Industrial scale, but believe it or not 50k+ Lt of water are just enough for the dry period (will have approx 2-7 tanks left) as you use more water then you know it.

 

 

Likewise, I am always getting the spanish inquistion on what I paid for my solar system and what the payback is. Fortunately it is pretty easy to calulate the savings = Previous PEA Bill + Previous Gasohol Bill neither of which I pay now thanks to solar.

 

Funny that nobody ever asks what I pay for water security. Admittedly we are not on city water so I would have to do something, but most people around here have a small surface pump and a 20m well and when it dries up they get water trucked in. The fact that the trucks look identical to the “Honey Trucks” that are used to empty septic tanks doesn’t seem to bother them.

 

What i’ve done is a bit more expensive, but it gives me drinking water; household water and water for the garden.

 

8 minutes ago, Bandersnatch said:

 

Likewise, I am always getting the spanish inquistion on what I paid for my solar system and what the payback is. Fortunately it is pretty easy to calulate the savings = Previous PEA Bill + Previous Gasohol Bill neither of which I pay now thanks to solar.

 

Funny that nobody ever asks what I pay for water security. Admittedly we are not on city water so I would have to do something, but most people around here have a small surface pump and a 20m well and when it dries up they get water trucked in. The fact that the trucks look identical to the “Honey Trucks” that are used to empty septic tanks doesn’t seem to bother them.

 

What i’ve done is a bit more expensive, but it gives me drinking water; household water and water for the garden.

 

I have a few water thanks myself and a purifier for drinking water and i use to tell wife that this is best investment ever so we could stop buying water bottles.

 

Pink

31 minutes ago, Pink7 said:

I have a few water thanks myself and a purifier for drinking water and i use to tell wife that this is best investment ever so we could stop buying water bottles.

 

Pink

Water tanks ...

37 minutes ago, Pink7 said:

I have a few water thanks myself and a purifier for drinking water and i use to tell wife that this is best investment ever so we could stop buying water bottles.

 

Pink

Same same here.  Think we have six 2k L tanks, and strictly for drinking rain water once passed through 2 stage counter top filter.  Far less PPM than filtered tap water, and damn near free ???? vs bottled from Makro.

 

On topic ... same as solar or EV, a larger initial investment, that will pay for itself for decades.

 

 

How do you guys handle the initial rain water collection?

I suppose you have a metal roof.

So the first rain, takes all the bird <deleted> and dust away. How do you switch to fill the "clean" water in your big bottles ?Or do you have a filter?

 

On 1/30/2023 at 10:18 PM, TronxII said:

How do you guys handle the initial rain water collection?

I suppose you have a metal roof.

So the first rain, takes all the bird <deleted> and dust away. How do you switch to fill the "clean" water in your big bottles ?Or do you have a filter?

 

I have a "first flush" system. I also have 2 separate filter systems  - one for household water and one for drinking.

 

 

The first flush system leaves any dirt at the bottom of the first flush and opening the valve flushes it away. I tend to open for the first rain of the season and a couple of times after that.

 

 

 

Maybe we should add "off-grid living" to the forum heading?

 

And "teotwawki prepping"?

 

25 minutes ago, Crossy said:

Maybe we should add "off-grid living" to the forum heading?

 

And "teotwawki prepping"?

I'm prepped ... Solar, transport & drinking water

... garden is getting there.  Daughter pointed out our greenhouse (45+m²) will be 50% larger than her condo ????

 

Plenty of blades to deal with the walkers ????

5 hours ago, Crossy said:

And "teotwawki prepping"?

I had to google that one!