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Help needed to plan and design my OFF-GRID system


Off_grid

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We decided that we will go Off Grid very soon but will keep the Eskom utility active for a few months once installed.

So I contacted 3 Solar installers and provided them with our usage and requirements. Each of the 3 gave me a design and components list, but all 3 were TOTALLY different and I formed an opinion that most installers are in it to make BIG money out of you rather than what is best for your requirements.

This made me realise that I will have to do my homework and ask for some help and suggestions from people with knowledge and experience in this field. 

Suggestions on the design and equipment as well as other comments and Tips and Tricks will be appreciated .

 

This is what our needs are:

Go totally off grid as soon as possible (because we pay about R2540.00 pm only for the Eskom network and facilities per month regardless whether we use electricity or not).

Back-up power will be provided by a 12kVa Generator

Use one of the following 2 battery options (unless there is a very good reason to use something else) - Pylontech US3000 or Blue Nova 52V LifeYPO4

Stick to products with a good reputation, warranty and support

We use 1.8kWh per hour at night. (Mainly Security systems such as Alarm, CCTV, Security lights outside, a refrigerator and 2 Freezers)

During daytime we use roughly 2.5kWh per our on average

Total kWh is 56kWh per day. We are in the process of reducing the total requirment by replacing certain components) Geyser and stove replace with Solar and Gas.

Pitched corrugate iron roof that face North with a total span of about 20m (First 10m of roof get some shade till about 9am. Other 10m if full sun the whole day)

House/Office also have about 7m of pitched corrugate iron roof facing East and 7m Facing West (with no shade during daytime)

We aim for a battery bank of 32 to 42kWh (Usable between 25.6  and 33.6kWh).

I would appreciate any advice of the design, size and components to use. (Various Victron components were on most of the installer's lists) 

 

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Hi  @Off_grid

I would suggest start with power saving, get the geysers replaced with solar geysers and stoves and ovens changed to gas, replace your lights with LEDs. Once this is done you can monitor usage again. Eliminating the top users of power prior to investing in solar will either save you a lot on your solar setup, or allow you to get the best there is.

The reason i say this is cause my usage was pretty much bang on your usage 50-60kw a day, and the above mentioned changes allowed me to go off-grid and i am now using around 20-30kw a day without any quality of life changes.

 

Edited by stoic
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1 minute ago, Jaco de Jongh said:

Welcome @Off_grid

May I ask in which area you are? If you know MR T, you might be in my area.. 

Hi Jaco, Thanks for the welcome.

Must say that this is one of the best forms I have ever joined, filled with lots of information. Too much information for e newbie like me to know where to find what I need.

I will update my profile with the required info, but I am from Lichtenburg, about 60km West of Lichtenburg in the North West province. 

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5 minutes ago, stoic said:

Hi  @Off_grid

I would suggest start with power saving, get the geysers replaced with solar geysers and stoves and ovens changed to gas, replace your lights with leds. Once this is done you can monitor usage again. Eliminating the top uses of power prior to investing in solar will either save you a lot on your solar setup, or allow you to get the best there is.

The reason i say this is cause my usage was pretty much bang on your usage 50-60kw a day, and the above mentioned changes allowed me to go off-grid and i am no using around 20-30kw a day without any quality of life changes.

 

Thanks Stoic, we have done quite a bit to reduce our energy usage and brought it down from about 70kWh to about 50 and going down.  Geysers and stove replaced. Aircons replaced with Evaporator for cooling and Anthracite stoves/heaters for heating . Borhole pump also changed to solar and use the Wind-pump to water the garden.

Not sure if we will manage to go below 40kWh, but yes we can still do a lot. Reason why we use so much is because the house is used as an office too, so there are always people working on Laptops and screen (32" LCD TV's) during daytime. Security and perimeter lighting is also consuming a lot at night, which are essential on a farm in a remote area.

If I size for max 50kWh and I manage to bring it down steadily, I will have more backup for those rare occasions where the sun is not shine a lot for a few days in a row. Not that that happens here very frequently. But I am still aiming to reduce my usage at night as the good batteries are extremely expensive.

Mind sharing with me the details of your off-grid system. I know every installation is different due to many factors, but sometime you get very good ideas from what others have done.

Thank you for your reply and advice. Much appreciated.

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This won't be cheap, it will be big money.

That 2.5K pm might be worth keeping after you've done your sums. ( You don't mention the size of your supply -1ph or 3ph)?

Before we get bogged down in small details.

My off-grid thoughts are:

1. You get plenty panels, enough panels so that you never need that generator (or your batteries) on a cloudy day. That's about 4 times more than you need on a sunny day. Buy your panels by the pallet, and preferably all at once. Panels that match can really help with flexible configurations to squeeze the most out of your equipment. (I'll expound on this reasoning, if you want).

2. You should go for East-West string combinations as much as possible, you'll always have too much power at noon, you want to start making decent watts at dawn, and only stop at dusk. A longer solar day is better that a whole heap of unusable power at noon. Don't go less than 15 degree slope ( so they are self- cleaning in the rain). Flatter panels make more power when it's overcast.

3. Go lithium or big OPVz (both very expensive.) Site batteries were they will be cool and not subject to temperature swings.

4 Use a combination of AC -coupled inverters and DC MPPTs with hybrid inverters. Without starting a war, I only have experience with Victron and I think they are good. Use the AC-coupled PV inverters for strings that are further away to make DC cabling cheaper. High voltage DC MPPT's are expensive and not as high voltage either.

5. 48V, obviously, but consider battery to inverter cable runs at 48vdc, they will be carrying a lot of current so you want them as short as possible.

6. Get a clip-on ammeter, an MC4 crimper and an hydraulic crimper and consider safety working at heights.

 

 

 

Edited by phil.g00
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In your situation a good generator is cheaper than too many batteries, so if you size your batteries to keep you going overnight, and then use a generator for the odd cloudy day you will save on batteries. Also if you have a big power draw for some reason, just run the generator.

When I went off grid Eskom was charging R1300 odd for connection plus all those other charges, R2500 now  just makes me smile!

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56 minutes ago, phil.g00 said:

This won't be cheap, it will be big money.

That 2.5K pm might be worth keeping after you've done your sums. ( You don't mention the size of your supply -1ph or 3ph)?

Before we get bogged down in small details.

My off-grid thoughts are:

1. You get plenty panels, enough panels so that you never need that generator (or your batteries) on a cloudy day. That's about 4 times more than you need on a sunny day. Buy your panels by the pallet, and preferably all at once. Panels that match can really help with flexible configurations to squeeze the most out of your equipment. (I'll expound on this reasoning, if you want).

2. You should go for East-West string combinations as much as possible, you'll always have too much power at noon, you want to start making decent watts at dawn, and only stop at dusk. A longer solar day is better that a whole heap of unusable power at noon. Don't go less than 15 degree slope ( so they are self- cleaning in the rain). Flatter panels make more power when it's overcast.

3. Go lithium or big OPVz (both very expensive.) Site batteries were they will be cool and not subject to temperature swings.

4 Use a combination of AC -coupled inverters and DC MPPTs with hybrid inverters. Without starting a war, I only have experience with Victron and I think they are good. Use the AC-coupled PV inverters for strings that are further away to make DC cabling cheaper. High voltage DC MPPT's are expensive and not as high voltage either.

5. 48V, obviously, but consider battery to inverter cable runs at 48vdc, they will be carrying a lot of current so you want them as short as possible.

6. Get a clip-on ammeter, an MC4 crimper and an hydraulic crimper and consider safety working at heights.

 

 

 

@phil.g00 , big money it will be but I believe it could be paying for itself in less than 10 years. Still busy doing some calculations on this.

In the last 6 years the monthly Eskom installation charge went up from R1648 to R2540 per month. With the current financial crisis at Eskom this will increase even more rapidly in the years to come. If I take this fixed monthly fee, escalate it at a moderate increase of 10% per year, I will pay a minimum R453461.20 over the next 10 years without using a single watt of electricity. Just doing this calculation was an eye opener for me

In the short run I should maybe looking at a phased approach by only installing 50% of the planned battery capacity and only run essentials like CCTV, Lights and Alarms  off the battery while using eskom supply for the rest. We still have the old meters that can be turned back if I push energy back into the grid when I have excess supply during day time. Will just make sure I keep my eskom usage as close as possible to 0kWh.  

I currently have 3 phase supply, but plan to convert the house/office to single phase as it sounds easier to implement. Not 100% sure if this is correct, but this is my understanding for now. 

In my workshop which is only used occasionally, I will use my existing 12kW 3 phase generator to run the 3 phase machinery and other high current single phase machines when needed.

One of the small rooms inside the house will be converted to house the batteries and inverters. The plus side of this is that the temperature can be kept to about 25 degrees as it will get cooling from the evaporator. So batteries and equipment will be very close to each other and in a secure location.

Going East/west orientation on the panels is also something I am considering but I will have to increase the number of panels. 

Aiming for Lithium at the moment as I do not have any knowledge on OPV's.

Can you recommend any good AC-Coupled inverters so that I can investigate this. No sure how expensive this alternative will be.

Thanks for your thoughts and information.

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1 hour ago, DeepBass9 said:

In your situation a good generator is cheaper than too many batteries, so if you size your batteries to keep you going overnight, and then use a generator for the odd cloudy day you will save on batteries. Also if you have a big power draw for some reason, just run the generator.

@DeepBass9 Thanks, that sounds like a very good idea as good batteries seems to be close to 50% of the total project cost.

See my calculation on the fixed grid fee. Paying that will cost me close to 500,000.0 over the next 10 years if there are no major increases.

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14 hours ago, Off_grid said:
16 hours ago, DeepBass9 said:

In your situation a good generator is cheaper than too many batteries, so if you size your batteries to keep you going overnight, and then use a generator for the odd cloudy day you will save on batteries. Also if you have a big power draw for some reason, just run the generator.

@DeepBass9 Thanks, that sounds like a very good idea as good batteries seems to be close to 50% of the total project cost.

See my calculation on the fixed grid fee. Paying that will cost me close to 500,000.0 over the next 10 years if there are no major increases.

I second this logic, however I think I'd over-panel for a cloudy day, in lieu of relying too heavily on a generator. Panels are just so easy and long-lasting.

Maybe some combination of both?

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In winter I usually run my generator for about 2 hours in the morning to give the batteries a bit of a boost, and run the toaster, microwave etc. Last time I ran the generator was probably mid August, and I've been running entirely on solar since then. The most generator use is in late autumn actually, when you get shorter days, and more clouds, even more than mid winter which is usually very clear skies. 

I use 15-18 kWh/day so if you scale up my system by about 3 times, you should be in the right ballpark.

My batteries are now at 95% at 1:30pm, so  I am bit overpanelled, although it is almost midsummer.

As was pointed out above, it is cheaper to save power or replace power sucking appliances, rather than trying to power your inefficiencies using solar, but I think you get that already.

Edited by DeepBass9
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16 hours ago, Off_grid said:

Can you recommend any good AC-Coupled inverters so that I can investigate this. No sure how expensive this alternative will be.

I buy PV inverters secondhand on Ebay from the UK. I pay about £50 per kW on average. Probably another 50 quid on top of that in local shipping.

I've learn't to buy models under 21kg ish, then I just pay for an extra suitcase (£65) when I fly to SA twice a year.

An overweight suitcase (23kg+) is a further £65, but they often just "Tut, tut" and don't charge you in Ireland, (where I am based.)

Once a year, I have my 2 sons with me, we can take quite a few inverters between us.

Fronius, ABB, Solis and SMA all work with frequency shifting. SMA are good but quite heavy.

I already have 7 assorted to come with me in 2020. I took 6 across last year. One was a dud.

 

Edited by phil.g00
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1 hour ago, DeepBass9 said:

In winter I usually run my generator for about 2 hours in the morning to give the batteries a bit of a boost, and run the toaster, microwave etc. Last time I ran the generator was probably mid August, and I've been running entirely on solar since then. The most generator use is in late autumn actually, when you get shorter days, and more clouds, even more than mid winter which is usually very clear skies. 

I use 15-18 kWh/day so if you scale up my system by about 3 times, you should be in the right ballpark.

My batteries are now at 95% at 1:30pm, so  I am bit overpanelled, although it is almost midsummer.

As was pointed out above, it is cheaper to save power or replace power sucking appliances, rather than trying to power your inefficiencies using solar, but I think you get that already.

I was also thinking to go to about 58.5kWh on a sunny winters day. This is 40 x 380W panels at 5.5 hours per day (30% loss included). "On a clear summers day it should give me 74.5kW.

On overcast days I will use the generator to boost batteries levels if needed.

I see that if I buy 2 pallets (56 panels) I can get them at R4.63/kW (AE-Solar Mono panels). Warranty looks very good, but not sure how they measure up against the more popular Canadian solar panels when it comes to price, performance and reliability. I will buy a few spare panels. 

Still have a few appliances to change, but will expand on security which might cancel each other out.   

Edited by Off_grid
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18 hours ago, Off_grid said:

We still have the old meters that can be turned back if I push energy back into the grid when I have excess supply during day time. Will just make sure I keep my eskom usage as close as possible to 0kWh.

You wont get away with this forever, and you'll probably have to do the connection yourself.

But, if you can avoid detection and the meter man seeing the disc spinning backwards, it presents the lowest hanging fruit.

North -facing panels and grid-tie PV inverters using ESKOM as your battery you will be realizing savings for the minimum outlay straight off.

I'd bank the savings though so you can get to a full offgrid situation though, 'cause if you get copped you might be off-grid sooner than you planned to be.

 

 

Edited by phil.g00
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Solis grid tie inverters are reasonably priced in SA. 

For the grand off-grid plan in the future, these are some constraints:

You need a ratio of not more than 1:1 (PV inverter kW: Hybrid inverter kW) and 5kWh of Lithium battery/1.5kW of PV inverter or alternatively, 5kWh of LA battery/1kW of PV inverter.

You will need a DC MPPT as well, because your batteries go flat the hybrid inverter wont make AC and if there is no AC the PV inverters wont start to charge the batteries again. So a DC MPPT breaks that deadlock situation. Use the DC MPPT from your closest strings to save on cabling. There are DC MPPT's that have a built in PWM output to drive an SSR that can be used for resistive opportunity loads at peak times. (Midnite and Outback)

Get a PV inverter with two MPPT's built in, (the more MPPT's the better the efficiency), then these can be optimized with E-W strings to be pumping power all day. PV strings are normally 25% over-sized kWp for the inverter.

 

 

Edited by phil.g00
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23 hours ago, stoic said:

I would suggest start with power saving, get the geysers replaced with solar geysers and stoves and ovens changed to gas, replace your lights with LEDs. Once this is done you can monitor usage again. Eliminating the top users of power prior to investing in solar will either save you a lot on your solar setup, or allow you to get the best there is.

To support what @stoic says, I would get a whole bunch of these:

They work well to schedule loads so as to minimize power peaks, and the also meter power(kW) and energy(kWh) which is very useful in your planning stage.

Someone has commented on Aliexpress that they don't fit a ZAR plug, but they do.

https://www.aliexpress.com/item/4000130920613.html?spm=a2g0s.9042311.0.0.27424c4dpsNsjZ

ZAR smart plug.JPG

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