Grid tie solar in a generator-based environment? (split from the Solar Car Port thread)

[driver52]

11 hours ago, Crossy said:

The golf-cart cells are about 280 x 182 x 71 mm and weigh in at 4.2kg each. You need 16 of them for a 48V pack like that. The used 200Ah ones come in at about 1,600 Baht a pop.

I'm totally gobsmacked how cheap those are! Wish they were that cheap in Europe ????

[Crossy]

16 minutes ago, driver52 said:

I'm totally gobsmacked how cheap those are! Wish they were that cheap in Europe ????

 

These cells are well used and are down to about 80% of rated capacity but good for experimentation, and treat them gently they should be good for a decent number of cycles.

 

[ExpatOilWorker]

On 8/16/2021 at 11:45 AM, Crossy said:

but the hybrid inverter doesn't appear to be grid tie so your load must remain below the inverter maximum output.

How did you so easily conclude the inverter is not full grid tie in?

Do you have a link that explains the different types of grid tie in inverters?

Too many commercial sites are clouding my search.

 

 

[Crossy]

I did say it didn't "appear" to be grid-tie, I can't find an on-line manual so cannot be certain. It does say it can be operated without batteries but how it performs is unknown.

 

https://www.lazada.co.th/products/hybrid-inverter-off-grid-mppt-100a-anern-35-55-kw-anern-wifi-i2123652088.html

 

Specifically sold as an off-grid hybrid, it also doesn't mention parallel operation if it did do parallel it would be mentioned.

 

 

[ExpatOilWorker]

1 minute ago, Crossy said:

I did say it didn't "appear" to be grid-tie, I can't find an on-line manual so cannot be certain. It does say it can be operated without batteries but how it performs is unknown.

 

https://www.lazada.co.th/products/hybrid-inverter-off-grid-mppt-100a-anern-35-55-kw-anern-wifi-i2123652088.html

 

Specifically sold as an off-grid hybrid, it also doesn't mention parallel operation if it did do parallel it would be mentioned.

 

 

It is rather confusing for a layman. 

Why is an off-grid inverter still connected to the grid?

 

Anyhow, here is the manual. 

 

wifi-monitoring-hybrid-solar-inverter-manual.pdf

[Crossy]

24 minutes ago, ExpatOilWorker said:

It is rather confusing for a layman. 

Why is an off-grid inverter still connected to the grid?

 

It is indeed confusing, not helped by "marketing", I've got meetings all morning but I'll try to put something simple together, it might be worth a pinned thread.

 

If you understand an off-grid system (panels, battery, inverter), then add a mains battery charger and you have an off-grid hybrid. If there's not enough solar the DC energy is topped up from the grid via the charger.

 

[Crossy]

6 hours ago, ExpatOilWorker said:

It is rather confusing for a layman. 

Why is an off-grid inverter still connected to the grid?

 

Just for you ???? 

 

 

 

[Crossy]

@ExpatOilWorker something like this might suit your purposes. Four 5kW off-grid hybrids with parallel kits for a max 220V output of 20kW.

 

https://www.aliexpress.com/item/33002096587.html

 

I've used this seller in the past with excellent results, they will also ship "Thailand Special Line" which means there's no duty/VAT to pay at this end (and the shipping cost is the same as FedEx).

 

[tjo o tjim]

On 8/18/2021 at 6:23 PM, ExpatOilWorker said:

It is rather confusing for a layman. 

Why is an off-grid inverter still connected to the grid? 

 

It is a good application for when you have a critical load that you want to run off solar as much as possible, but use the grid as a backup.

 

Speaking to your broader issues, I wonder why they never put solar panels on the water tank, at least to try to offset some of the diesel use.  By far, that is the best place for solar on that system.  A battery would need to be down by the generators because of how it was set up.

[ExpatOilWorker]

On 8/17/2021 at 10:58 AM, Muhendis said:

This is a lot simpler than you might think. You only need to worry about the biggest loads. If you work it backwards from the maximum power capability of the inverter which is 5.5 kw. First there is the short duration peak power capability which is 11 kw Divide that by 9 = 1.22kw (I use nine times for startup current under load). Look for any of your motors which get anywhere near that. Have a think about what else may be already running at that time (fridge for example). If you're still less than the short duration peak then there is nothing to worry about. Worst case scenario is, of course, all motors switched on at precisely the same time. That's never going to happen.

This is good advise and it firmly puts me in the grid tie in hybrid camp.

The 1,800 W vacuum cleaner alone will have a start load higher than the inverter can handle on its own.

[Muhendis]

1 hour ago, ExpatOilWorker said:

The 1,800 W vacuum cleaner alone will have a start load higher than the inverter can handle on its own.

That's not entirely true. The vacuum cleaner motor will be a series wound motor in which the current flows through both the commutated armature and the field windings. Due to the inductance of these windings, the startup current for this type of motor will always be less than an induction motor. The figure of 2½ times rings a bell but I am relying on memory for that. 

Having said that, I think you are right to doubt the capability of a 5.5kw inverter to run your household electrics unaided. I have an 8kw inverter which has a transformer output driven by 10kw capable electronics and I consider that to be the bare minimum. When I did my power consumption spreadsheet the requirement came out for a 12kw system. I had to do a bit of careful manipulation of the figures to adjust the times when power requirements were occurring simultaneously. Also I had to allow for battery charging. My woodworking machines (fractional horse power motors) are fine with that inverter. 

Edited August 21, 2021 by Muhendis
additional info.

[Opossum]

Hi

 

on page 17 of the manual, it says that this inverter is made for AGM and flooded batteries. Can one still combine lithium batteries with this inverter?

 

regards

[driver52]

3 hours ago, ExpatOilWorker said:

The 1,800 W vacuum cleaner

crazy man! the EU has a limit on 900w and 80 decibles, yes I know they are powered crazed loons but every now and again they do something useful ????

[Muhendis]

1 hour ago, Opossum said:

Hi

 

on page 17 of the manual, it says that this inverter is made for AGM and flooded batteries. Can one still combine lithium batteries with this inverter?

 

regards

Yes. There is the user define option in battery selection. With that selection the charge voltage etc. can be set to whatever is required.

[ExpatOilWorker]

On 8/18/2021 at 4:51 PM, ExpatOilWorker said:

85 KVA Cummins, but as you can see bearly idling at 3 kW.

Even a small solar system could easily overwhelm the grid at high noon.

I could go down and take a reading late at night, when everyone are using aircons, but I might never return from such a risky endeavor if I encounter the local wildlife. The night belong to the jungle.

 

Just got my first electricity bill from the genset: 25 baht/Kwh!

 

The genset is consuming 3,400 l of diesel to produce 4,000 Kwh. Because it is running at near idle only 10% of the energy in the diesel is converted to electricity. Solar kind of put this antiquated technology to shame.