Author Topic: EEVblog #484 - Home Solar Power System Installation  (Read 65967 times)

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Offline elektrinis

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Re: EEVblog #484 - Home Solar Power System Installation
« Reply #175 on: June 23, 2013, 08:07:19 am »
Hey Dave. I may have a money-saving solution for you. Sorry I did not read all 12 pages and it may have been suggested already.
What I am suggesting is to add a buffer battery. Not a crappy lead acid one, but today's quality lithium one. These (sinopoly LiFePO4 for example) are quite cheap and hold thousands of full cycles or tens of years of calendar life. And they have no capacity loss (Peukert's effect), are very safe, etc (those are used on some electric cars, but especially in power grid, large (multiple MWh sized) UPSes, etc).

Battery management and integration is the tricky part, but here I have another solution. :) My company is producing battery management system (BMS) for lithium batteries, which is well integrated with SMA converters. Our BMS is very popular in Germany and other solarized countries. Check it out:
http://www.elektromotus.lt/en/products/battery-management-system-bms
http://www.elektromotus.lt/wiki/index.php?title=Main_Page&Itemid=155
« Last Edit: June 23, 2013, 08:19:40 am by elektrinis »
 

Offline hpnut

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Re: EEVblog #484 - Home Solar Power System Installation
« Reply #176 on: July 09, 2013, 02:14:31 pm »
Hello all.  This is continuation of the 2.5kWp system installed at my home. 

Today was Testing & Commissioning day by my utility provider Tenaga Nasional.  System was successfully commissioned  at 1100h.  It was raining and we had overcast cloud too, until around 1600h.  At 1900h sundown, the panels stopped production.  Total production was 6kWh and 5kWh exported.  Here are some photos.

Arjunaidi from Putrajaya, Malaysia
 

Offline hpnut

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Re: EEVblog #484 - Home Solar Power System Installation
« Reply #177 on: July 09, 2013, 02:18:15 pm »
more photos
 

Offline hpnut

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Re: EEVblog #484 - Home Solar Power System Installation
« Reply #178 on: July 09, 2013, 02:50:46 pm »
I also installed a Sunny Boy WebBox to view inverter performance data.
 

Online timelessbeing

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Re: EEVblog #484 - Home Solar Power System Installation
« Reply #179 on: July 27, 2013, 04:30:35 am »
Great video, Dave. Have you calculated how long it will take to break even on your investment?

I wonder why the installer didn't adjust the height of the rails on the brackets to offset the "undulating" roof structure.  I know in the end it doesn't really matter... but the brackets have elongated holes, why not use them to make the rails straight?
or take it a step further, and tilt the panels towards noon-day sun position. The angle of incidence to the sun affects output does it not?

Why are PV panels connected in series rather than parallel? Is it because the higher voltage reduces losses? You can use cheaper, thinner conductors? It's going to increase the costs of components in the inverter though right?
 

Offline mtdoc

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Re: EEVblog #484 - Home Solar Power System Installation
« Reply #180 on: July 27, 2013, 05:43:27 am »

Why are PV panels connected in series rather than parallel? Is it because the higher voltage reduces losses? You can use cheaper, thinner conductors?

Yes, less losses and because voltage needs to be well above utility voltage for mppt conversion before inverting. Typical individual panel Vmp is about 30V

Quote
It's going to increase the costs of components in the inverter though right?

No, more volts means less amps= less copper= less money.
« Last Edit: July 27, 2013, 05:45:09 am by mtdoc »
 

Online timelessbeing

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Re: EEVblog #484 - Home Solar Power System Installation
« Reply #181 on: July 27, 2013, 06:01:37 am »
No, more volts means less amps= less copper= less money.
I was thinking higher voltage rated caps, transistors etc.. but maybe it's insignificant compared to copper costs.
 

Offline SeanB

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Re: EEVblog #484 - Home Solar Power System Installation
« Reply #182 on: July 27, 2013, 09:48:30 am »
600V caps are about the same price as 400v units, basically the same construction just a thicker oxide layer grown on the surface. The transistors in any case will be 1000V or 1200V units, so no cost difference. Copper losses will be the same, but the thinner wire used costs less, and the thinner board copper is cheaper and means you can have narrow traces on the same board as broad power traces.
 

Offline mtdoc

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Re: EEVblog #484 - Home Solar Power System Installation
« Reply #183 on: July 27, 2013, 06:31:38 pm »
It's not the copper or losses in the electronics that's the issue.  It's the DC voltage drop in the wire run from panels to inverter or charge controller if battery based system. You generally want less than a 2% voltage drop from array to inverter or controller. This can mean fat, expensive wire.

If the PV is on the homes roof then the wire run may be a short wire run and it's not as much of an issue. But if the house is large enough so that the PV array is quite a ways from the electronics or if the array is on a ground or pole mount away from the home - this becomes a major consideration.

It's a bigger  issue for battery based systems (off grid or grid tied with battery back up).  The charge controller generally have lower max input voltages and you don't want the individual string voltages too far above battery bank voltage (12, 24 or 48V nominal) for mppt conversion efficiency sake.

 

Offline starchild

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Re: EEVblog #484 - Home Solar Power System Installation
« Reply #184 on: August 13, 2013, 09:12:07 pm »
Hi chaps.

I haven't read anything here about deploying micro inverters instead of a string inverter.

I use a lot of home automation and am really interested in using every last bit of power from an installed PV system and not allowing it back to the grid - the intelligence that I can build into my HA brain will hopefully help me do that. However I want to get very granular data to model what's going on and the data extracted from each individual panel by way of these micro inverters is what I need. It will of course add to the installation cost but there is also a saving by way of increased panel efficiency as the effect of shading will be reduced - and I'll get a considerably longer life than I would from the string inverter. Cabling and switchgear is also simplified as it's plain old mains voltage.

Anybody investigated the pro's and con's and got any real world experience?

I've only found two manufacturers and I'm limited to one of them, Enecsys, as the other (Enphase) uses power line communication which is very likely to cause issues as I employ X10 as my automation protocol on the mains wiring.

I'd love to store any excess energy and use it in the evening but battery storage is way too expensive - and those cells don't have a very long life expectancy!
 

Offline DrGeoff

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Re: EEVblog #484 - Home Solar Power System Installation
« Reply #185 on: August 13, 2013, 10:22:30 pm »
With some new and interesting technology in the supercap area, it would be interesting to see if using a supercap behind each panel to store charge and make it available to the inverter when the panel is dark would be an interesting power storage mechanism.
Was it really supposed to do that?
 

Offline DrGeoff

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Re: EEVblog #484 - Home Solar Power System Installation
« Reply #186 on: October 07, 2013, 12:08:57 am »
Dave,

Any updates on the efficiency or power measurements after a while of using it? Particularly after the few hot days we've had?
Was it really supposed to do that?
 

Offline bronzies

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Re: EEVblog #484 - Home Solar Power System Installation
« Reply #187 on: October 07, 2013, 02:18:58 am »
I really enjoyed this video, i think videos that cover the really practical aspects of electric circuits like PVs and stuff come second only to the tear downs of good mobile gadgets like the nook teardown (that was my absolute favorite! especially the part about the "magic" light scattering. so funny to listen to an electronics engineer talk about materials engineered to scatter light or something else non-electricy!) please keep em' coming!
 

Offline jnissen

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Re: EEVblog #484 - Home Solar Power System Installation
« Reply #188 on: October 07, 2013, 03:31:47 am »
Looks like September 18th was the last communication with the PVOutput web site. Perhaps Dave pulled the plug on the communication or he has not checked it lately? Are you using another monitoring system now?
 


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