Offgrid solar project

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David57
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Offgrid solar project

Post by David57 »

Hi,
I have a project of photovoltaic installation in France.
Without complicated authorisation, we can't send current on grid, on heart we can not do the same thing than on house, very complicated.
I have a tri phased 12KVA counter at home, but 9KVA is enought on a monophased installation.
I think to plug 3 230VAC to 48VDC Meanwell 3KVA to have the 9 KVA that I need, on 48V, the 3 phases are equalized.
With one diode, no current can return on grid.
This current go directly on inverter.
Solar panel (from 15 to 30KWC) go on inverter too, regulated at max 55V, so inverter take current from solar first, and from grid if not enought.
In some years, if battery cost is lover, it's easy to add on this system, or wind turbine, or everything that can give more than 48VCC.
It's should be possible to use the unused solar energy to heat water or air from VMC.
The question is the choice for inverter. 3 x 5048 in mono or 3 5048 in tri phase ? Model ? who's take the less current at night ?
Or inverter that just do 48V to 230V ? But i have not see model that work in parallel.
Someone has allready do that ?
Thank you,
David.
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Re: Offgrid solar project

Post by coulomb »

David57 wrote: Sun, 28 Apr 2019, 01:09 ... in France. Without complicated authorisation, we can't send current on grid...
Huh. Strange, when neighbouring Germany seems to be leading the world with high penetration renewable energy. I wonder if it's something to do with the large proportion of nuclear power in France.
I have a tri phased 12KVA counter at home, but 9KVA is enought on a monophased installation.
I think a little is getting lost in the translation here. I assume you mean that you have a meter (counter) that maxes out at 12 kVA, but you think that your loads will never exceed 9 kVA, and you could live with single phase if needed.
I think to plug 3 230VAC to 48VDC Meanwell 3KVA to have the 9 KVA that I need, on 48V, the 3 phases are equalized.
Yikes. That's a large battery charger. But you seem to want to at least start without a battery. That's quite unusual, and I'm not sure it would work. Firstly, I don't see how it could respond to sudden demands properly. Also, it would have to be a special kind of solar charge controller, to work with no battery. Also, if you could solve all that, in the event of a grid failure, it would collapse any time that loads exceeded solar power. But I assume power is very reliable where you are.
With one diode, no current can return on grid.
? You can't block return power with a diode on an AC circuit. But the fact that the Meanwells are straight AC to DC converters should mean that there is no possibility of feeding power into the grid.
Solar panel (from 15 to 30KWC) go on inverter too, regulated at max 55V, so inverter take current from solar first, and from grid if not enough.
15 to 30 kWp is again a quite large installation.
The question is the choice for inverter. 3 x 5048 in mono or 3 5048 in tri phase ? Model ? who's take the less current at night ?
To operate without a battery, you'll need a model with the high voltage Solar Charge Controller. All the PIP-5048 series are quite high in self consumption. With all that solar power, you would some (possibly a lot of) auxiliary charge controllers (each 5 kW inverter can only handle about 4.5 kW of PV panels).
Or inverter that just do 48V to 230V ? But i have not see model that work in parallel.
I'm not aware of any that can operate in parallel. But for three phase, three single phase inverters would work.

It's a grand plan, David, but I think you really need to sort out some practical issues. Read up on batteryless inverters; I read somewhere that they restrict the loads to a small fraction of available PV power, for example. I don't believe that there are a lot of batteryless installations, so this is fairly new territory, especially for large systems such as the one you are thinking of.
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Re: Offgrid solar project

Post by David57 »

You can see a first plan on what i want to do on attached file.
Diodes can only routing DC current.
I already have my old Studer 3548SI inverter, that is just an inverter without charger. I use it before connected on grid.
Solar in France is just a big joke, i have many offer for 6kwc with a wooden carport for 25000 to 35000, for auto-consume, with micro-inverter.
I buy current 0.16€/KW, and sell price if i take this contract is 0,10€/KW.
I can buy 15KWc new mono black solar panel 310Wc at 5000€.
For one year, i need 12000KW from grid.
So 15KWc cover on theory with battery, 30KWc cover largely, even cloudy days with battery.
Actually, battery cost is as better condition, at 0,10€/KW, based on buy cost, battery life, and total energy accumulated and giving during life.
Battery cost should be lower with time, grid current cost will grow up, battery become more interesting.

All my devices are on mono, so it's not a problem to switch in mono, but with 100m from counter to home, i cannot switch counter on mono.
12KVA is just to have enough on each phase, 9KVA, even 6KVA is enough on total, but it's limit at 3KVA or 2KVA on one phase.
Bigger consumer are on different phase.

All in one inverter offer a dream installation, but one serie cannot use high voltage string (longer distance between inverter and panel with smaller cable), other serie accept high voltage string but cannot use at same time grid and solar. And it's closed to adding new energy possibility such wind, hydrogen cell...
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Richo
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Re: Offgrid solar project

Post by Richo »

David57 wrote: Sun, 28 Apr 2019, 17:35 So 15KWc cover on theory with battery, 30KWc cover largely, even cloudy days with battery.
How many solar hours do you get?
In Perth Australia we get 4.2kWh/kW/day as a yearly average.
So a 15kW PV system is 63kWh per day and 22,995kWh per year.

Will the meanwell 3kW 48V power supplies be happy in parallel?
So the short answer is NO but the long answer is YES.
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Re: Offgrid solar project

Post by David57 »

I have 3KWc for selling at 0,65€/KW and 6KWc at 0,46€/KW, that product 2600 to 3000KW and 5300 to 5800KW respectively.
3KWc product max by a day 18KW on summer and 3 KW on winter, but can be 0kw during a day or exceptionnaly 2 or 3 week wenn snowing, I have see that just one year. Based on the last 9 years.
30KWc is overkill on summer, but on winter, the day are very short, sun doesn't go very high, with cloudy days.

Meanwell are parallel working capable by a sharing current communication port and can be use in medical equipment.
A second port can be plug on charge to mesure cable loss and adapt output voltage to correct it.

It's not "i take 3 piece connect in parallel and, magic, it's work", that's on the specs with scheme.
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Re: Offgrid solar project

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David57 wrote: Sun, 28 Apr 2019, 01:09 I think to plug 3 230VAC to 48VDC Meanwell 3KVA to have the 9 KVA that I need, on 48V, the 3 phases are equalized.
David57 wrote: Mon, 29 Apr 2019, 14:27 It's not "i take 3 piece connect in parallel and, magic, it's work", that's on the specs with scheme.
Oh I see.
I also notice on the specs say:
Maximum output current at parallel operation=(Rated current per unit)×(Number of unit)×0.9
Which is 8100W not quite the 9 kVA.


So is the issue deciding between the expensive contract but getting money for feeding onto the grid OR getting a cheaper system with no grid feed but more options for upgrades?

Do you know what goes in the blue block between solar panels and 48V diode?
So the short answer is NO but the long answer is YES.
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Richo
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Re: Offgrid solar project

Post by Richo »

So here is what I suggest.

Ditch the diodes as I don't think you need them - I'm in the process of confirming this.
Modularise the solar panels with LINKABLE MPPT 48V charge controllers.
Add a 48V 5760Wh LTO battery pack to provide system stability and 1hr+ of battery backup.
Turn down the Voltage on all the RSP3000 to as low as they go (~43V) while still within the 0.2V parallel spec.
Remove the over-current hiccup mode link so it goes into constant current mode.

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So the short answer is NO but the long answer is YES.
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Richo
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Re: Offgrid solar project

Post by Richo »

Going like for like the Studer VS-70 is EUR$838ea.
With 12 Solar panels in series this is 397V at peak power and 482V Open.
At 310W each 12 panels would be 3720Wp for each VS-70.
And the panels, as you said, would be EUR$1250 for 12.

So each block is EUR$2088 for 3720W.
AND 4 blocks is 14880W of solar and EUR$8352.

The RSP3000-48 are EUR$425ea so EUR$1275 for all 3.

The 5760Wh LTO battery would be EUR$2415.

All up EUR$12042.
Plus cabling, fuses, misc installation bits etc...
And a Butt load of time.

On the plus side since it's modular you don't need to buy it all at once.
So the short answer is NO but the long answer is YES.
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Re: Offgrid solar project

Post by David57 »

It's a good way.

But how can I know how many unused solar power is available ?
And is solar MPPT price correct vs more solar panel with simple PWM or just one transistor that absorb the excessive power on each panel, it's like a pig, but we speaking from "free" power.
Studer make very good devices, but very expensive.

I have see LiFePo bat with BMS, is LTO safe too ? And for BMS ?

The contract for selling stay in place and I stay connected on grid, but virtually disconnected, system can run without grid ans never send on it.
I have 3 counter, one for home consumers on one cable, and on another cable, one for solar selling, and one that stay to 0 to see if i not take current from grid. One contract for buy, one for sell, totally separated. Easy !

I think beginning system with just AC/DC and DC/AC converter to testing, then adding solar panel so i can see how it run, and first, cover the computer, modem, cameras... that run 24/24
Time to data logging all current needing, and switching some consumer on grid on winter, on solar on summer, such oven, electric plate, heat pump.
Battery must be sized to cover all in summer, but just stay as UPS on winter.
On summer, i need 20KW for 24H.
The correct point must be find for bypassing the converter minimize the loss of system cost.
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Re: Offgrid solar project

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David57 wrote: Sun, 28 Apr 2019, 17:35 I already have my old Studer 3548SI inverter, that is just an inverter without charger. I use it before connected on grid.
Is the 3548Si the 48V DC to 240Vac inverter you plan to use?
I couldn't find any data on this part.
So the short answer is NO but the long answer is YES.
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Richo
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Re: Offgrid solar project

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David57 wrote: Wed, 01 May 2019, 19:27 But how can I know how many unused solar power is available ?
And is solar MPPT price correct vs more solar panel with simple PWM or just one transistor that absorb the excessive power on each panel, it's like a pig, but we speaking from "free" power.
Studer make very good devices, but very expensive.
Well I was going like for like.
There may be other devices that do the same job that are cheaper.

It isn't as easy as connecting solar panels through a diode to a 48V line.
And it isn't realistic to connect 15kW of PV with one MPPT or transistor.
So the short answer is NO but the long answer is YES.
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Re: Offgrid solar project

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David57 wrote: Wed, 01 May 2019, 19:27 I think beginning system with just AC/DC and DC/AC converter to testing, then adding solar panel ...
Well I think that is a good place to start.
If you run a regular 48V-240V DC/AC sine wave inverter to your house most of these have an input range of 41-60V DC.
So the RSP3000-48 is fine.

Now if you added a 310W solar panel to the 48V line, with a diode, the output of the panel will be 33-40V.
This is below the RSP3000-48 and inverter so the panel will never add power onto the 48V line or power up the inverter.
Putting 2 panels in series the voltage is 66V-80V which is above the input voltage of the inverter and cause damage.
So you will need a boost or buck converter (MPPT) to connect the solar panels to the 48V line.

Most MPPT solar regulators wont handle 15kW.
So they need to be linkable to get to 15kW.

When the sun shines the solar makes 48V and ALL the power goes to the house.
When you draw MORE than the panels can provide the 48V line will droop down to the ~43V of the RSP3000-48.
So the difference is then drawn from the grid.

When the sun goes down the power only comes from the RSP3000-48.

It's all self regulating.
The only issue is if the MPPT controllers are happy without a battery.
So the short answer is NO but the long answer is YES.
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Re: Offgrid solar project

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David57 wrote: Wed, 01 May 2019, 19:27 Battery must be sized to cover all in summer, but just stay as UPS on winter.
On summer, i need 20KW for 24H.
But you wouldn't use all 20kWh during the night?
Once you have solar you can shift most of your heating, cooling, washing etc to the day when the sun shines.
Even 10kWh over 14 hours of "night" is still an average power of 700W - Fridge, TV, some lights, computer...
Taking into account sleeping for 8 hours that's 8hrs of 200W of idle and 6 hours of 1400W of fun.

10kWh is double the battery size what I said in a previous post.
David57 wrote: Wed, 01 May 2019, 19:27 The correct point must be find for bypassing the converter minimize the loss of system cost.
I'm assuming in winter you want to bypass the whole system and run the grid direct to the house.
I wouldn't bother - especially once you have a battery.
So the short answer is NO but the long answer is YES.
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Re: Offgrid solar project

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David57 wrote: Wed, 01 May 2019, 19:27 I have 3 counter, one for home consumers on one cable, and on another cable, one for solar selling, and one that stay to 0 to see if i not take current from grid. One contract for buy, one for sell, totally separated. Easy !
See this is where Australia differs.
We don't have this.
Even for 3-phase it's just one bi-directional meter.

You could put a transfer switch between the DC/AC inverter output and the house and feed in one of the grid lines direct to the switch.
This would bypass the entire system for winter.

What is the electricity "service cost" which is the daily cost of having the power to hour house? NOT the kWh unit charge for consuming the power.
There must be cost cross over to have the power disconnected to your house completely - toally off grid.
So the short answer is NO but the long answer is YES.
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Re: Offgrid solar project

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David57 wrote: Wed, 01 May 2019, 19:27 I have see LiFePo bat with BMS, is LTO safe too ? And for BMS ?
LTO is the same as LiFEPO4 but with titanium added to electrode.
They should be safer than LiFePO4.
They should be more tolerant of over charge and discharge.
Some have suggested no BMS for LTO.

For a 48V system there are 20 LTO batteries in series.
So you may need 20 battery monitor modules.
Someone will make these already.
So the short answer is NO but the long answer is YES.
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Re: Offgrid solar project

Post by David57 »

First, I wouldn't operate with a unique 15KW power source, I see 3 possibility for this moment :
- One panel, one mppt boost converter, one DC output, for each panel.
- Two panel in serial, one voltage limiter, one DC output, for each paar.
- 9 panel for exemple, one MPPT buck converter, one DV coutut, for each string.

Electricity cost is very complicated :
Price for counter 12kVA, cut at 12kVA on total of 3 phase or 4kVA on one phase : 13.31€/month with price day/night + VAT 5,5%
Price for kWh from 6h30AM to 22h30PM : 0.0988€/kWh + VAT 20%
Price for kWh from 22h30PM to 6h30AM : 0.0715€/kWh + VAT 20%
Tax for public service of electricity : 0.0225€/kWh + VAT 20%
Tax for departement-region : 0.00323€/kWh + VAT 20%
Tax for transport of electricity : 5.32€ for 2 month + VAT 5.5%
Easy, doesn't ?

For selling, on earth, cannot, on roof on tile, one price, on roof at place of tile, better price, and must pay 60€/year for added counter and access to the grid.
Autoconso is not possible with panel on earth, just on roof or carport, not possible by autoconstruction if reject solar power on grid, and company ask about 25000 to 35000€ for carport with 6kWc panel with one microinverter on each panel, what is injected on grid is buy at 0,10€/kW

If solar power is>3kWc or >1,810 meter from earth, I must ask for authorization to mayor.
If i install many group <3kWc en under 1,80 meter high, it's not necessary.

The diode are just here for protection, the current cannot go on the wrong side, even grid fall out. The RSP3000-48 never receive current from panel.
A transistor can limit voltage on each branch :
As the Ohm Law say, the current is the sum ot each branch.
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Re: Offgrid solar project

Post by David57 »

See this page for selling prices :
https://www.picbleu.fr/page/tarifs-d-ac ... voltaiques
The market is very closed.

I must try if it is possible to instantly switching from one source to other for oven or electrical plate, with two triac at the moment of the two lines are on zero volts, and running on same direction.

On winter, i'm ok two take current of battery, but a little part as summer, for battery life and in case of grid fall.
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Re: Offgrid solar project

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Re: Offgrid solar project

Post by Richo »

Ah so the minimum is 45.6V before your inverter shuts down.
And it doesn't say anything about connecting solar to a 48V system only 12V or 24V.

I'd sell it and get something else since you probably wont connect solar to it and has a high shutdown voltage.
So the short answer is NO but the long answer is YES.
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Re: Offgrid solar project

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David57 wrote: Thu, 02 May 2019, 18:26
- Two panels in series, one voltage limiter, one DC output, for each pair.

A transistor can limit voltage on each branch :
As the Ohm Law say, the current is the sum of each branch.
Please forget this idea its not really practical.
So the short answer is NO but the long answer is YES.
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Re: Offgrid solar project

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David57 wrote: Thu, 02 May 2019, 18:26 Electricity cost is very complicated :
Price for counter 12kVA, cut at 12kVA on total of 3 phase or 4kVA on one phase : 13.31€/month with price day/night + VAT 5,5%
Price for kWh from 6h30AM to 22h30PM : 0.0988€/kWh + VAT 20%
Price for kWh from 22h30PM to 6h30AM : 0.0715€/kWh + VAT 20%
Tax for public service of electricity : 0.0225€/kWh + VAT 20%
Tax for departement-region : 0.00323€/kWh + VAT 20%
Tax for transport of electricity : 5.32€ for 2 month + VAT 5.5%
Easy, doesn't ?
So this is similar to our time of day charges.
Peak, off peak, shoulder and weekend rates.

Still your power is cheap compared to Australia.
So the short answer is NO but the long answer is YES.
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Re: Offgrid solar project

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David57 wrote: Thu, 02 May 2019, 18:26 For selling, on earth, cannot, on roof on tile, one price, on roof at place of tile, better price, and must pay 60€/year for added counter and access to the grid.
Autoconso is not possible with panel on earth, just on roof or carport, not possible by autoconstruction if reject solar power on grid, and company ask about 25000 to 35000€ for carport with 6kWc panel with one microinverter on each panel, what is injected on grid is buy at 0,10€/kW
So given a 15kW system with NO grid feed is EUR$12k and 6kW system with grid feed is EUR$25k I think the answer is clear.
Don't feed onto the grid.
Especially if it follows Australia where the feed in price drops.
From the web site in your link it says new buildings must have solar by 2020.
So you will end up with a grid surplus and so the feed in price drops.
So the short answer is NO but the long answer is YES.
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Re: Offgrid solar project

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David57 wrote: Thu, 02 May 2019, 18:26 If solar power is>3kWc or >1,810 meter from earth, I must ask for authorization to mayor.
If i install many group <3kWc en under 1,80 meter high, it's not necessary.
So is this ONLY if you feed into the grid?

I understand the local council may have height restrictions - not just for solar.
But can you put 15kW on your house or on your property (under 1.8m) without submitting to the mayor?
So the short answer is NO but the long answer is YES.
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Re: Offgrid solar project

Post by David57 »

The law say "no" for more than 3kWc, one the same surface.
The law say nothing about many smaller surface, so...

I can put a small garden house from 1x1m on each coin of property, but not one of 2x2m without asking. Same case.

- Two panels in series, one voltage limiter, one DC output, for each pair, why is is not possible ? it's the same thing than many battery in parallel, no ?
While each branch is protected to never run as receiver, all branch are added and giving the current that is ask by inverter, no more

This inverter is 18y old, and have just one 48VDV input and one 230VAC output. No mere functionality.

The current cost must grow up rapidly, we have many old nuclear power plant. And who pay for that ?
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Re: Offgrid solar project

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David57 wrote: Fri, 03 May 2019, 19:53 The law says "no" for more than 3kWc on the same surface.
Ah way to go for promoting renewable energy.

We used to have councils that wouldn't allow solar panels on the roof that faces the road.
How things have changed.

Perhaps you are just ahead of your time ;)
So the short answer is NO but the long answer is YES.
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