Solar pergola -advice needed

[erik.calco]

@ilia.vikhman I was very inspired by your project to look at building a pergola over my patio. I was originally thinking of doing a pavilion.

After much thought, the biggest risk is wind. It's a structure that takes advantage of wind flow through it to not require common stability enhancements. Adding solar panels changes that. Have you calculated wind loads? Perhaps there are students on campus who are learning to do these types of calculations.

 

[ilia.vikhman]

@erik.calco i'm so happy that my project was inspired someone(except me hh) , acttully i don't know if you read it but my project is still in the process the pergola going to be built in the end of the month and the solar part in December(as you saw i have some issues with battery sizing.

and regarding the wind-load and etc. So because i'm doing this project in university , they have a forestry/wood department that specialized in constructing building from wood, So all of this covered by them (we just had to make sure that there enough space for the solar panels)
one thing that they said(regarding safety features) that they will use(something like this) :


i hope i was helpful ..my advice that maybe you will wait till i finish(+post some pictures) and will have more knowledge to share ☺

 

[erik.calco]

@erik.calco i'm so happy that my project was inspired someone(except me hh) , acttully i don't know if you read it but my project is still in the process the pergola going to be built in the end of the month and the solar part in December(as you saw i have some issues with battery sizing.

and regarding the wind-load and etc. So because i'm doing this project in university , they have a forestry/wood department that specialized in constructing building from wood, So all of this covered by them (we just had to make sure that there enough space for the solar panels)
one thing that they said(regarding safety features) that they will use(something like this) :
View attachment 2079

i hope i was helpful ..my advice that maybe you will wait till i finish(+post some pictures) and will have more knowledge to share ☺

In spring, when you get 50+ mph winds, you definite have to report back with picts. lol

I love it and really hope it works. If you can get the plan/schematics/BOM from the forestry/wood department, I'd be forever grateful!

 

[ilia.vikhman]

@erik.calco
I love it and really hope it works. If you can get the plan/schematics/BOM from the forestry/wood department, I'd be forever grateful!
Sure i will share once i will have it

In spring, when you get 50+ mph winds, you definite have to report back with picts. lol
i think you have a little mistake ...i'm from Europe(in my location it't wind-zone I, less then 25 m/sec)

 

[erik.calco]

@erik.calco
In spring, when you get 50+ mph winds, you definite have to report back with picts. lol
i think you have a little mistake ...i'm from Europe(in my location it't wind-zone I, less then 25 m/sec)

You got me there. Never heard "m/sec" until now. So, when you get that unusual wind storm, over 25m/sec works ;p ....

 

[eddie1261]

Just build it with lattice and an open beamed roof concept like a true pergola should be. If you don't create a sail it won't catch the wind. And 50 mph winds should not be an issue. Houses face higher winds than that and while a roofing shingle may come off once in awhile, the sheathing under it doesn't. If you have tornado level winds it won't matter, as it will be gone no matter what.

 

[FilterGuy]

Hi Guys ! i made some calculation yesterday(first time for an off-grid system) can you please advice that i'm on the right way

Location :East Europe,

Isolation

2,86 PSH

Consumption

	Rated Power[W]	AC/DC	Amount	hours per day	Total consumption daily (wh/day)
Phone Charge (USB)	2.5	DC	4	3	30
PC charger	65	AC	2	3	390
				Total Wh	420

days of autonomy	3 [Days]
Total Wh needed from Battery	1260 [Wh]
Total Ah needed from Battery(12V)	105 [Ah]
PV array needed	441 [W]
Inverter AC needed size	156 [W]

Charge controller: =275*2/12=46 [A]

Final sizing(components)


1. PV panels =CS6K-275W(see attached Datasheet), 2 pc

2.Battery=12V, 90 Ah ,1 pc

https://www.ev-power.eu/LiFeYPO4-batteries-12V-1-1/Lithium-Battery-12V-90Ah-WB-LP12V90AH.html?cur=2

3.Charge controller ,1 pc

https://www.ev-power.eu/Victron-Ene...controller-100V-50A-Bluetooth.html?cur=2#tab3

4.Inverter, 1pc(little bit over sized ...i know)

https://www.ev-power.eu/Inverters-D...ml?cur=2&listtype=search&searchparam=Invertor

It looks like you are on the right track! However, if the pergolas are popular, you are likely to see more than 3hrs/day use. I could see a student sitting there for several hours working on homework. However, as others have mentioned, the daylight usage could be entirely from solar, so you only have to worry about night-time use. (Hint: When I was in college, must of us were night owls)

I notice you are calling out the LiFeYPO batteries. Is there a reason for this? Supposedly they can handle temp extremes better but they tend to be a lot larger per W-hr.

 

[ilia.vikhman]

It looks like you are on the right track! However, if the pergolas are popular, you are likely to see more than 3hrs/day use. I could see a student sitting there for several hours working on homework. However, as others have mentioned, the daylight usage could be entirely from solar, so you only have to worry about night-time use. (Hint: When I was in college, must of us were night owls)

I notice you are calling out the LiFeYPO batteries. Is there a reason for this? Supposedly they can handle temp extremes better but they tend to be a lot larger per W-hr.

Thank you very much for your input!

 

[ilia.vikhman]

here it coming....

 

[erik.calco]

here it coming....
View attachment 3008

That going to fit through the door? lol

You ever get a diagram of the design of the structure? I am learning a lot from your picture, being new to building wood structures. I can't tell exactly how you have those top boards mounted (red lines). I assume the top of the 4x4s go up to the bottom of those boards (left green). I also see you have a support for the top boards (right green diagonal). Are these assumptions correct?

 

[Craig]

here it coming....
View attachment 3008

Nice work!

 

[FilterGuy]

The A photo doesn't have a table, but that would certainly fill in the "empty" space. Do you have any images representing the final idea?

I'm thinking the table top could be on a pedestal, and all the gear hidden inside. The wire from the panels hidden in a "hollow" support post (e.g., four 2x4's rather than a single 4x4's so there's a hidden hole in the center) then run underneath to the pedestal. This way you don't have to worry about squirrels or students picking at the wire's insulation. I'd also use a sealed inverter so you don't have to worry about ventilation/weather.

As to the battery size, it really depends on how much power you expect to be drawn during non-sun hours. For example, let's say you want six students with 6 laptops, each drawing 50 watts of power and you expect it to be used on average of 10 hours a day. Let's also say you want a string of led christmas type lights to run 24x7 to jazz it up and they use 10 watts. So you need:

6 laptops x 50 watts x 10 hours = 3000 watt hours
24 hrs x 10 watts = 240 watt hours.

Let's assume an 80% efficiency for the battery, inverters, and wiring; so total battery power is 3240 / .8 = 4000 watt hours.

Let's assume from the insolation map you get 5 for the equivalent "full" sun hours, so you'd need 3240 / 5 / .8 = 810 watts of panels. Or 3 of the 325 watt Canadian Solar panels.

For the battery, let's assume 12V, so 4000 / 12 ~= 350 Ah. Or if you want an extra day to insure it works through a gloomy day that's 700 Ah @ 12V.

If you want to stick with those 60 Ah Victron Gel lead acid batteries you'd want to limit the depth of discharge to 50%, so that bumps it up to 700 or 1400 Ah. At 60 Ah per battery, you'd need 12 to 24 and that's a lot to put in parallel. Even then you'll probably only get 5 years out of them. This is where lithium shines, longer cycles and greater depth of discharge.

If you want it to work in cold weather, you'll need to look at the data sheet to see how much it'll lose with temperature. You should probably also check the draw rate; a 60 Ah lead acid battery is only 60 Ah if you're pulling less than 3 amps from each battery. See the Battery FAQ for all the fun details.

I agree that the battery is small. However, one factor is that some of the usage will be in the daytime and the power will draw directly from the solar panel. In fact, depending on where it is, the usage might be almost entirly in the daytime.

The A photo doesn't have a table, but that would certainly fill in the "empty" space. Do you have any images representing the final idea?

I'm thinking the table top could be on a pedestal, and all the gear hidden inside. The wire from the panels hidden in a "hollow" support post (e.g., four 2x4's rather than a single 4x4's so there's a hidden hole in the center) then run underneath to the pedestal. This way you don't have to worry about squirrels or students picking at the wire's insulation. I'd also use a sealed inverter so you don't have to worry about ventilation/weather.

As to the battery size, it really depends on how much power you expect to be drawn during non-sun hours. For example, let's say you want six students with 6 laptops, each drawing 50 watts of power and you expect it to be used on average of 10 hours a day. Let's also say you want a string of led christmas type lights to run 24x7 to jazz it up and they use 10 watts. So you need:

6 laptops x 50 watts x 10 hours = 3000 watt hours
24 hrs x 10 watts = 240 watt hours.

Let's assume an 80% efficiency for the battery, inverters, and wiring; so total battery power is 3240 / .8 = 4000 watt hours.

Let's assume from the insolation map you get 5 for the equivalent "full" sun hours, so you'd need 3240 / 5 / .8 = 810 watts of panels. Or 3 of the 325 watt Canadian Solar panels.

For the battery, let's assume 12V, so 4000 / 12 ~= 350 Ah. Or if you want an extra day to insure it works through a gloomy day that's 700 Ah @ 12V.

If you want to stick with those 60 Ah Victron Gel lead acid batteries you'd want to limit the depth of discharge to 50%, so that bumps it up to 700 or 1400 Ah. At 60 Ah per battery, you'd need 12 to 24 and that's a lot to put in parallel. Even then you'll probably only get 5 years out of them. This is where lithium shines, longer cycles and greater depth of discharge.

If you want it to work in cold weather, you'll need to look at the data sheet to see how much it'll lose with temperature. You should probably also check the draw rate; a 60 Ah lead acid battery is only 60 Ah if you're pulling less than 3 amps from each battery. See the Battery FAQ for all the fun details.

I agree the battery seems too small, but some (Most? , All?) of the usage will be during the day and the power will be coming directly from the solar panel.

Also, the Christmas lights are a nice touch but they are 1) optional and 2) could be limited to early evening (say 4 hours).

 

[ilia.vikhman]

That going to fit through the door? lol

You ever get a diagram of the design of the structure? I am learning a lot from your picture, being new to building wood structures. I can't tell exactly how you have those top boards mounted (red lines). I assume the top of the 4x4s go up to the bottom of those boards (left green). I also see you have a support for the top boards (right green diagonal). Are these assumptions correct?

View attachment 3013

honestly ..i have no idea how this built(this my partner responsibility) my job to come after and build the PV

 

[Vlad-Solacity]

honestly ..i have no idea how this built(this my partner responsibility) my job to come after and build the PV

Hey ilia,

A few comments regarding sizing your system.

- A Victron charge controller is too expensive for such an application. There are various other brands that make a decent quality charge controller at a lower price. Indeed, Victron charge controller can communicate with an app, do you really need it though? You can go with any MPPT charge controller between 20Amp and 40 Amp that will do a trick. Take a look at the spec of a charge controller, in some cases, the charge controller has its max input power, so the undersized charge controller may prematurely brake. I would recommend going with 30Amp is the most cost-effective solution. In summer, you will lose some energy as 550W of panels can potentially generate around 39Amps and not 46 previously calculated. You can go with 40Amps if it fits your budget, the price difference is negligible.

- Regarding the batteries, the type of the battery chosen will not work in winter in your application as lithium-ion can't be charged when the temperature is below freezing (0 Celsius Centigrade), the BMS will cut off the battery. Please note, you can discharge but you CAN'T charge the battery at low temperature. You would look at the AGM/GEL batteries that are basically free of maintenance. It will work, though they do have some limits. The size should be around 215Ah 12V. Why so? The lead-acid batteries can't be discharged to the ground/ 0% state of charge, it just will kill the battery. Normally, they have 50% of usable stored energy that you can use on a regular basis without damaging the battery. Actually, you can from time to time discharge the AGM/GEL battery up to 20% SOC (state-of-charge), then you should fully charge them after that. Also, lead-acid batteries (AGM/GEL) absolutely must see a full charge once per 2- max. 4 weeks. Not following all of this will shorten the number of cycles thus killing the battery very soon. For AGM lead-acid batteries the recommendation is to use 20% of the Ah rating for charging.

- Regarding the inverter. The size is 200W. You don't have any appliance that requires more than that.

Cheers,
Vlad

 

[ilia.vikhman]

Hey ilia,

A few comments regarding sizing your system.

- A Victron charge controller is too expensive for such an application. There are various other brands that make a decent quality charge controller at a lower price. Indeed, Victron charge controller can communicate with an app, do you really need it though? You can go with any MPPT charge controller between 20Amp and 40 Amp that will do a trick. Take a look at the spec of a charge controller, in some cases, the charge controller has its max input power, so the undersized charge controller may prematurely brake. I would recommend going with 30Amp is the most cost-effective solution. In summer, you will lose some energy as 550W of panels can potentially generate around 39Amps and not 46 previously calculated. You can go with 40Amps if it fits your budget, the price difference is negligible.

- Regarding the batteries, the type of the battery chosen will not work in winter in your application as lithium-ion can't be charged when the temperature is below freezing (0 Celsius Centigrade), the BMS will cut off the battery. Please note, you can discharge but you CAN'T charge the battery at low temperature. You would look at the AGM/GEL batteries that are basically free of maintenance. It will work, though they do have some limits. The size should be around 215Ah 12V. Why so? The lead-acid batteries can't be discharged to the ground/ 0% state of charge, it just will kill the battery. Normally, they have 50% of usable stored energy that you can use on a regular basis without damaging the battery. Actually, you can from time to time discharge the AGM/GEL battery up to 20% SOC (state-of-charge), then you should fully charge them after that. Also, lead-acid batteries (AGM/GEL) absolutely must see a full charge once per 2- max. 4 weeks. Not following all of this will shorten the number of cycles thus killing the battery very soon. For AGM lead-acid batteries the recommendation is to use 20% of the Ah rating for charging.

- Regarding the inverter. The size is 200W. You don't have any appliance that requires more than that.

Cheers,
Vlad

@Vlad-Solacity thanks for you inputs , regarding the charge controller-unfortunately i cant use more then 20 A otherwise the charging rate will be too much for the battery .

 

[Vlad-Solacity]

@Vlad-Solacity thanks for you inputs , regarding the charge controller-unfortunately i cant use more then 20 A otherwise the charging rate will be too much for the battery .

Are you going to proceed with the 105 AH lithium-ion battery, the one you chose earlier?

 

[Supervstech]

For the uses described here, the panels will be far in excess of battery capacity. Low cost inverter, and 24v usb quick charge outlets.

Are homeless an issue? Because free power for phones and computers can be an attraction...

Also, hackers target usb hubs, so use security screws on the coverplates.

 

[ilia.vikhman]

Are you going to proceed with the 105 AH lithium-ion battery, the one you chose earlier?

Hi, 110 Ah but not the lithium..where did you saw lithium datasheet?

 

[ilia.vikhman]

For the uses described here, the panels will be far in excess of battery capacity. Low cost inverter, and 24v usb quick charge outlets.

Are homeless an issue? Because free power for phones and computers can be an attraction...

Also, hackers target usb hubs, so use security screws on the coverplates.

No i don't think that homeless would be an issue ..BTW i never saw homeless with laptop ?
and what you mean by "security screws" ? @Supervstech

 

[Supervstech]

No i don't think that homeless would be an issue ..BTW i never saw homeless with laptop ?
and what you mean by "security screws" ? @Supervstech

They dont often have laptops, but they all have phones

Security screws are screws that are designed so they go in, but cannot be taken out.