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Re: Offgrid solar project

Posted: Fri, 24 May 2019, 12:54
by Richo
A XP power HDS3000PS36 trimmed to 31.5V would be about right.

Re: Offgrid solar project

Posted: Fri, 24 May 2019, 13:19
by Richo
Oh and in the 32V/36V system it wouldn't be practical to connect a battery pack.

So you either have the 32/36V system and never have a battery.
OR you go with the 48V system and use PV controllers and have the option of a battery.

Re: Offgrid solar project

Posted: Fri, 24 May 2019, 18:43
by David57
Hi,
I have now the 32 solar panel, each 310W.
I try now to first regulate each panel at 28-29VDC, so i can have 16 strings of 2 panel, or one of 16// + 16//.
The max power that regulator dissipate is from 0 to 35W, depending of solar power, current, panel temp.
At 10A, voltage isn't very higher 28-29V, and when panel is hot, voltage is lower.
The regulator is extremely easy for a cost of 10€ pro panel.
And if the current that I pull down the voltage panel under my 28 or 29 V, the regulator take no power and no voltage.
May be is not a good way for today technology, but it's easy, no programming bug, panels can be added.
That's on paper, I receive components next week to do the first test.

What do you think for this way ?
I open a blog page for this project this week-end for photos, scheme and all details.

Re: Offgrid solar project

Posted: Fri, 24 May 2019, 20:32
by David57
If the working voltage must be change, I prefer go with upper voltage than a lover voltage to not increase current and reduce the size on cable.

Re: Offgrid solar project

Posted: Mon, 27 May 2019, 12:44
by Richo
Yeah 15kW / 48V is 312A :o
30V would make it 500A :o :o

I always have the preference for redundancy.
Splitting it into 3 makes it 5kW/ 48 V is 100A.
Which is more reasonable.
Then you can have 3 x 100A cables back to a main junction point near the inverter.

Obviously if you can only fit less than 3kW per structure then you have 62A.

Re: Offgrid solar project

Posted: Tue, 28 May 2019, 12:59
by David57
That's a maximum power capacity, I've never use the 12kW that grid permit.
Many possibility for inverters, independant on 2 or 3 output lines or working in parallel on same line.
How are working 3 inverters in parallel ? For 300W, each give 100W or one give 300 and 2 are on standby ?
I finally take a first Meanwell DPU-3200-48, a little more power, up to 5 in parallel, but problematic on three phase, so 3 if ok, 3 to 4% less loss power. 180A/48V with 3.

Re: Offgrid solar project

Posted: Tue, 28 May 2019, 15:41
by T1 Terry
Unfortunately no one has come up with a staged output parallel inverter set up, so the very light loads are spread across all the paralleled inverters making the delivery efficiency very poor at light loads.
I've been trying to get the professor (at one of the Chinese factories my China contact has close ties with) to design and build such a thing as a progressive start up inverter system for me, yes, no problems was the first response .... until he discovered there wasn't any such thing available to copy ..... been waiting 3 yrs now :lol:

T1 Terry

Re: Offgrid solar project

Posted: Wed, 29 May 2019, 12:20
by David57
The loads specs are always show, but it's not the normally usage of inverter, generally 1 to 10% load is a normal usage of 90% of time.
3 x 5kVA inverters in parallel take 150w to show time on oven in kitchen !
Is standby mode compatible with electronics devices ? For lights and resistiv charge is ok, but many devices haven't switch button on/off and staying in sleep mode.

Re: Offgrid solar project

Posted: Wed, 29 May 2019, 12:31
by Richo
David57 wrote:
Tue, 28 May 2019, 12:59
Many possibility for inverters, independant on 2 or 3 output lines or working in parallel on same line.
How are working 3 inverters in parallel ? For 300W, each give 100W or one give 300 and 2 are on standby ?
So I mean the 3 independent DC solar lines come back to ONE DC bus voltgate (48V).
If the fuse pops for some reason you still have 10kW out of 15kW of solar still running the 48V line.

Rather than have one big inverter supplying the whole house I thought have an inverter for each circuit.
For example I have:
a circuit that runs the power points along the front section of the house.
a circuit that runs the power points along the back section of the house.
a circuit that runs all the lights.
a circuit that runs the Air conditioner.
and a circuit for the Oven.

5 circuits all up so 5 inverters.

Would you rather the whole house go without power or just a section if a part fails?

Re: Offgrid solar project

Posted: Wed, 29 May 2019, 12:39
by Richo
T1 Terry wrote:
Tue, 28 May 2019, 15:41
Unfortunately no one has come up with a staged output parallel inverter set up, so the very light loads are spread across all the paralleled inverters making the delivery efficiency very poor at light loads.
I do understand your point.
When I say such things to a colleague he reminds me not to worry about it and get more power :lol:

Do you really want to live where a Wh make the difference between having the lights on or off?

Re: Offgrid solar project

Posted: Wed, 29 May 2019, 12:52
by Richo
When I did my last calculations I needed the first 2kW of a PV system just to offset the monthly Electricity supply charge.
So to me its all in or all out.

Obviously for France the story is different due to more cloudy/sunless days.

Re: Offgrid solar project

Posted: Wed, 29 May 2019, 19:01
by David57
Just one 48VDC line where all solar current are added.
The independent inverters or parallel inverters, is more to be free to change one by other without staying in the same model, in 5 or 10 years, i'm not sure to find a compatible model that work with other.
The grid stay so it's never a problem to switch on it, the time to receive replacement parts.
It's offgrid system, at point of view, the complement it's given through 230VAC/48VDC converter.

Re: Offgrid solar project

Posted: Thu, 30 May 2019, 12:35
by T1 Terry
I thought about setting up a system with a very small PSW inverter feeding in through the paralleled inverter array to power light loads. As soon as a load high enough to trip out the small inverter was sensed, the parallel inverter group went into UPS mode, the small inverter was disconnected from the supply side to allow it to reset and it remained disconnected until the excess load passed and the small inverter output would be able to support the minimal loads again.
I haven't managed to get past the ideas stage yet. It can already be done with the Victron Quattro inverters by dialling the input current back to a few amps, as soon as a load greater than that is sensed the inverters support the mains supply by what ever is required up to their maximum capacity. Great bits of gear, but the price :shock:

T1 Terry

Re: Offgrid solar project

Posted: Thu, 30 May 2019, 12:52
by Richo
David57 wrote:
Wed, 29 May 2019, 19:01
Just one 48VDC line where all solar current are added.
The independent inverters or parallel inverters,
Independent inverters.
Different sizes.
Any model.
Keep a spare - If one fails just swap it out.

Does your house run separate circuits?
DC_Home1.jpg
DC_Home1.jpg (85.66 KiB) Viewed 638 times

Re: Offgrid solar project

Posted: Fri, 31 May 2019, 03:22
by David57
Yes, actually, the circuits are made so :
3 phases that arrived
each phase go on one 10A light circuit that powered 8x10A light circuit.
each phase go on one 16A circuit that powered 16x16A circuits for plugs and other devices.
The 3 phases are equalized.

Re: Offgrid solar project

Posted: Sun, 02 Jun 2019, 17:12
by David57
Modern Meanwell AC to DC converter are a bad way for this application, I read 0,54A without any charge, and after one hour, the side become warm. about 35 to 40°C with 20°C ambiant temp.
Fans always on.
I send it back to store.
I trying now with 600VA toroïdal transformer.
I can plug and unplug to not use all when low power is asked, but does make a control circuit for that to plug rapidly, with a control of the five or ten first alternances to limit the inrush power that can be very big with this type of transformer.
After, classic Gretz with diodes and capacitor.
Coupled by three to equilibrate phases.
Regulator seems to be ok under panel to have 28V pro panel, 56V with each paar.
An aluminum plate from 3mm x 992mm x 100mm should be great to dissipate.
I've mesure Rth=1.5 with an aluminum plate of 1mm x 190mm x 400mm.