Planning an off-grid hybrid solar system

[Encid]

I have been reading this forum with great interest for a while now, and as some of you know I am planning to build a new house (2 actually... a guest house as well as a main house) on our farm land in Isaan.

Details and progress of that particular project can be found in this topic.

 

Anyway, I recall @Crossy when asked if he would do the same again about 7 months ago in another topic responded as follows:

 

On 6/21/2022 at 4:31 PM, Crossy said:

If I was doing it all over again with a decent budget rather than going bitsa-expansion I might go for a big off-grid hybrid system, say 20kW (4 x 5kW inverters in parallel) and run as a whole-house UPS as well as solar. No export of course, but being DIY that's not officially available anyway.

I kinda like that line of thinking... it provides for redundancy should one of the inverters fail or die, and also gives total independence from the increasingly expensive PEA supply which would only be used to top up the batteries or "help" the solar array if the sun is feeling tired.

 

Our new house will have plenty of roof space, so at the moment I am thinking to have 4 strings of 10 PV panels each connected in parallel to 4 x 5kW inverters supplying domestic 220vAC power and also a 27kWh ESS.

 

And of course I have worked up a plan for locating PV solar panels on the roof of the Main House.

The layout allows for plenty of access for cleaning/maintenance as well.

The house location will be at 15⁰ 40' 45.1" N.

 

I was thinking about installing 40 x 540W panels (21.6 kW) as per the sketch below.

Panels 1-10 and panels 27-36 facing South (total 20 panels.

Panels 11-14, 21-26, and 37-40 facing East (total 14 panels).

Panels 15-20 facing West (total 6 panels).

 

This would preserve the appearance of the U-shaped house (which faces East) and enable us to extend the working collection day of the panels by collecting more solar energy earlier in the day from the East facing panels, and again later in the day from the West facing panels, and also avoiding the midday peak in production that is associated with panels that all face South.

 

Future additional panels could be mounted on top of the carport if required.

 

 

I will be most interested in feedback/suggestions from members who have their own solar installations on this proposed arrangement.

 

Also I would like to hear of suggested or recommended  manufacturers/suppliers.

[BritManToo]

6 minutes ago, Encid said:

I will be most interested in feedback/suggestions from members who have their own solar installations on this proposed arrangement.

There is no reason to point PV panels anywhere but South (or as South as you can get).

[UWEB]

I'm planning a 8 Kw System as well and my Panels will face in west, south and aest direction as well. Solar Panels I will use Longi 540W ones and Inverter Huawei or Solax.

[Crossy]

@Bandersnatchis your man for this kind of system, including pointing panels in "non-optimal" directions.

 

Certainly, make as many panels as possible point south or close to it.

 

West pointing panels will extend your generating day into the evening at the expense of less peak output, east pointing panels will start generating early but don't seem to be as effective as the west pointers.

[Encid]

37 minutes ago, UWEB said:

Solar Panels I will use Longi 540W ones

I was thinking along the same lines... the LONGi Solar LR5-72HPH 540M Mono-PERC Half Cells are currently selling for around 5,700 baht each.

Trina Vertex Backsheet 540W Mono Half Cut Cells are currently selling for around 6,590 baht each. 

Sunenergy Mono 540W Model SUN540-72M-H8 Half Cells are currently selling for around 6,500 baht each.

Jinko 545W Mono Half Cut Cells are currently selling for around 6,690 baht each. 

POWITT 540W High Efficiency Solar M10 Mono Half Cells are currently selling for around 8,200 baht each.

[Crossy]

Do be aware that the "big" panels are, in fact, well, big!

 

You're not getting 540W in a panel the size of a 350W ???? 

 

They are also 'kin heavy!!

 

Unless you are really tight for space you will likely get more bang-per-buck from the older, smaller (power and size) panels. Do your sums carefully.

 

 

 

[Bandersnatch]

51 minutes ago, Crossy said:

pointing panels in "non-optimal" directions

I've got a video about that ???? 

 

 

[Encid]

55 minutes ago, UWEB said:

Inverter Huawei or Solax.

I would not consider Huawei inverters because you are locked into using their own very expensive batteries (about 4 x cost of similar sized kWh 48V batteries).

The inverters are fine for an off-grid system, but their batteries make them too expensive for a hybrid system.

 

Sofar, Solax, and Growatt are the three main inverter manufacturers I am looking at currently... but am open to suggestions for others.

[Encid]

3 minutes ago, Crossy said:

They are also 'kin heavy!!

Yep... about 29kg each!

[Crossy]

2 minutes ago, Encid said:

Yep... about 29kg each!

 

Does your health insurance cover hernias?

[Encid]

26 minutes ago, Bandersnatch said:

I've got a video about that ???? 

Thanks @Bandersnatch... solar curtailment is exactly what I want to avoid by an having earlier in the day start and a later in the day finish generating window.

 

Having nowhere to put the excess generated power in the middle of the day is something I want to avoid.

 

First question about your video... do the panels on your ground-mounted solar water heater face west or do I have my directions confused?

 

And second question, what is the slope of your roof on the lower level?

 

You mention the fact that even the north facing panels receive some sun during the day.

My build will have a flat roof, so the PV panel supports will need to be designed to enable a slope.

[Encid]

21 minutes ago, Crossy said:

Unless you are really tight for space you will likely get more bang-per-buck from the older, smaller (power and size) panels. Do your sums carefully.

Thanks for that suggestion... I will do a panel layout based on say 340W panels to generate a similar 22kW feed to the 4 x 5kW inverters.

The cost of the panels will decrease, but the cabling will increase.

[Bandersnatch]

58 minutes ago, Encid said:

do the panels on your ground-mounted solar water heater face west

Yes they do - not ideal but the insulated 200L tank is still warm enough in the morning. Location chosen to be as close as possible to the wet rooms in my house (Kitchen, Laundry, filter/pump room and Bathrooms) which are all located together on the East wall of my house. Facing the solar thermal east would have it facing a wall.

 

 

58 minutes ago, Encid said:

what is the slope of your roof on the lower level?

My house is in Surin Province which is 15 degrees North. The best compromise angle for winter/summer sun is 15 degrees which is the slope of my roof on all sides.

[BritManToo]

48 minutes ago, Encid said:

Thanks for that suggestion... I will do a panel layout based on say 340W panels to generate a similar 22kW feed to the 4 x 5kW inverters.

The cost of the panels will decrease, but the cabling will increase.

Not sure why the cabling cost would increase.

Run from inverter to PV string can be standard 2.5mm twin.

PVs mainly plug to each other.

[Muhendis]

25 minutes ago, Encid said:

Having nowhere to put the excess generated power in the middle of the day is something I want to avoid.

There is no such thing as "excess generated power". 

 

The sun shines whether you make use of it or not.

 

Just because you are not using the available electricity it produces is not a problem.

 

The fact is, it is there if you need/want it.

 

Imagine the situation where you have available 5kw of solar power but you have a sudden unplanned requirement for 6kw. You need to have that extra 1kw sitting there for that sudden requirement.

 

So you need to have available as much power as you think you will need +20% for the extras you forgot in your calcs. and for future expansion.

 

The "excess generated power" does not do any harm but just sits there enjoying the sun shine waiting for the time it's needed.

 

In detail.

With no current being taken (I=0Amps) the panel voltage (E) will go to its maximum possible and no higher (Voc) so from W=EI power (W) is zero. 

As current is drawn so the panel voltage will reduce. When the maximum current is reached (Imax) the power will be the sum of the current flow and the voltage of the panel at that point.

In a manner of speaking, if there is no current flow then there is no power to be referred to as excess.

[Pink7]

4 hours ago, Encid said:

Thanks for that suggestion... I will do a panel layout based on say 340W panels to generate a similar 22kW feed to the 4 x 5kW inverters.

The cost of the panels will decrease, but the cabling will increase.

You can get very nice deals on 340w now, check out for example Global House.

 

 

Pink

[007 RED]

@Encid As @Crossy mentioned earlier, those 450W panels are big, very big both in physical size and weight !!!!

 

Most specs that l've seen for 450W mono half cuts are around 2384 x 1303 x 35 mm and they weigh a mere 38.5 kg each.

 

Good luck with your proposed project it sounds mind blowing.

[KhunLA]

7 hours ago, Encid said:

Having nowhere to put the excess generated power in the middle of the day is something I want to avoid.

Having excess available production, is a good thing, for that week of total krap weather.  Some days, we barely topped up the ESSs (20kW).  Since so overcast, didn't really need the ACs, but a few days of that, and you'll wish you had the extra panels / production ability.

 

https://aseannow.com/topic/1268214-solar-8kw-hybrid-inverter-w10kwh-upgraded-to-20kwh-in-sept-2022-essbattery-not-diy/page/4/#comment-17734118

 

One day in August, we produce 49kWh, sending about 15 to the grid.   Yesterday we produced 34kWh, used 32.9kWh, since charging the car. 

[JBChiangRai]

I did something similar, 54 panels of 400w, 3 of MUST 5.5Kw Hybrid inverters, 28.8KwHrs of LiFePo4 ESS, the inverters didn't export properly so I added 3 of MUST 6Kw Grid-Tied inverters and moved all the panels over to that and reconfigured the Hybrid inverters as whole house UPS. Generally, we are producing between 55 and 85KwHr’s per day (more when I charge the car).

 

My total cost was a tad under 500k baht.

 

Lessons I learned, MUST Hybrid inverters don’t like exporting, MUST Grid-Tied inverters can have their settings altered to push more power out by increasing the upper voltage cut off.

 

If I was to do it again, I would have gone Grid-Tied only with a backup diesel generator, either 2 of 6Kw inverters or 3 phase 15Kw inverter and saved half the cost. I wouldn’t buy any export capable inverter unless I could tweak the export settings.

[HarrySeaman]

Encid, since "The house location will be at 15⁰ 40' 45.1" N. " you simply angle the solar panels from the same 15⁰ 40' 45.1" angle to the South from horizontal to get the maximum energy generation over the course of a year.  The only reason for not doing this is if you are willing to spend a lot of extra money for sun tracking panels.

 

The 15⁰ 40' 45.1" angle to the South is the best compromise because your home's location is North of the Equator.  It is better to eliminate the panels at other angles and increase your energy storage capacity with the money saved on panels.

[Pink7]

Much interesting info here.. I had to think over my plan as a last opportunity before adding my panels to roofing. So plan is 7s2p on each side. each side to its own Inverter. i have 12 degree North and 192 degree south. My roof angles about 15 degree. Plan is panels on the outer part of garage because of longer sun time. In afternoon house give some shadow on the part of roof nearest hose. Should I consider all panels on South side??

 

[Muhendis]

15 hours ago, BritManToo said:

Run from inverter to PV string can be standard 2.5mm twin.

That depends on the length of the cable and the maximum current it's required to carry.

My installation for example, generally runs at about 120v but the current from each of the two strings could be as much as 30A.

My cable length is under 10M (20M there and back-again) but I use 16mm² from the combiner boxes to the charge controllers.

That is probably an overkill since at 30A the losses would be about 22W

If I were to use 2.5mm² the losses would be about 144W which although not alarming, is considerably higher than I would be comfortable with.

[BritManToo]

35 minutes ago, Muhendis said:

runs at about 120v but the current from each of the two strings could be as much as 30A.

My string is 320v and 7A max. 

[Muhendis]

33 minutes ago, BritManToo said:

My string is 320v and 7A max. 

That would be about 7.8W loss for a 20M length of wire which I would guess is negligible using 2.5mm².

320V is high but I guess that's the trend.

What is your MPPT range?

[BritManToo]

8 minutes ago, Muhendis said:

What is your MPPT range?

150v to 450v.

[Encid]

14 hours ago, Pink7 said:

You can get very nice deals on 340w now, check out for example Global House.

 

 

Pink

Their online store prices have not changed for the past 5 months. 

 

See also this topic.

 

[Pink7]

25 minutes ago, Encid said:

Their online store prices have not changed for the past 5 months. 

 

See also this topic.

 

I got mine 330w panels for 2990. but the price was in the store only.

 

Pink

[Bandersnatch]

4 hours ago, HarrySeaman said:

It is better to eliminate the panels at other angles and increase your energy storage capacity with the money saved on panels.

That has not been my experience with solar here in Thailand  - maybe you could share your solar setup here to help explain what you are suggesting.

[Bandersnatch]

1 hour ago, Encid said:

Their online store prices have not changed for the past 5 months. 

 

See also this topic.

 

As a matter of interest here is the Global House price for solar from 2018 ????

 

[BritManToo]

1 hour ago, Pink7 said:

I got mine 330w panels for 2990. but the price was in the store only.

No stock in Chiang Mai as usual.