Author Topic: EEVblog #484 - Home Solar Power System Installation  (Read 66310 times)

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Online digsys

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Re: EEVblog #484 - Home Solar Power System Installation
« Reply #100 on: June 17, 2013, 05:05:54 am »
Quote from: DrGeoff
Damn right there. Vanadium redox batteries looked promising, but they seemed to have stalled, Otherwise not much really suited to a domestic situation with minimum maintenance and reasonable lifetime. 
I've a few friends with farms, or are greenies, that are completely off-grid. They just buy 2nds in SLAs or even wet-type for next to nothing,
load them onto pallets, add a paint shaker for wet cells (shaken 1hr per day use) and bob's your uncle. Recycled and dirt cheap storage.
A few I know even run their cars / trucks with 2nds. I know it's not for everyone.
Hello <tap> <tap> .. is this thing on?
 

Offline Lightages

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Re: EEVblog #484 - Home Solar Power System Installation
« Reply #101 on: June 17, 2013, 05:11:01 am »

He created a battery backup system for his house that costs about 700 pounds, and can power everything for eight hours and only the essentials for three days.  I wonder if, connected to a solar system in a clime that works in (the UK isn't, apparently, such a clime) if it could double as a smoother.

Sorry to be a bit of a skeptic about his claims for that backup system but he has nowhere hear enough batteries for his claims if he uses energy like most people. Of course he is not like most people.

I have a 48V system with 750AH of capacity.This is enough to run my house for a day. His capacity looks rather much lower, much much lower. He would be lucky to run his house for 3 hours IMHO and the essentials for maybe a day.
 

duskglow

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Re: EEVblog #484 - Home Solar Power System Installation
« Reply #102 on: June 17, 2013, 05:14:14 am »
Sorry to be a bit of a skeptic about his claims for that backup system but he has nowhere hear enough batteries for his claims if he uses energy like most people. Of course he is not like most people.

I have a 48V system with 750AH of capacity.This is enough to run my house for a day. His capacity looks rather much lower, much much lower. He would be lucky to run his house for 3 hours IMHO and the essentials for maybe a day.

This guy is rather famous for blowing stuff up with high voltage, so his not being "all there" is kinda somewhat of a very entertaining given.  That said, he did demonstrate that his system works with everything powered up for at least a little while.  So, you're perfectly justified in being a skeptic, but he did demonstrate that it works at least somewhat as advertised, and who knows, maybe that's at least enough to save up some of the excess generated during the day for the night.
 

Offline manicdoc

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Re: EEVblog #484 - Home Solar Power System Installation
« Reply #103 on: June 17, 2013, 05:25:55 am »
Hmm, that is crazy. I must admit I have been toying with the idea of getting rid of the mindless controller and hooking it up to something more intelligent. I have an integrated alarm (Comfort) and lights (CBus) via Linux box. Although want to split that function off to a really small form factor dedicated box (PC104); has a database in it, so can't really be a micro controller solution. This could be the straw that convinces me to do it..

The system I designed uses a little PIC18 + 10bT ethernet module I developed that has all the I/O on it and have several of these scattered around the house on a network. They talk to a linux box which has the event handlers and databases and web interface to allow monitoring and control functions. Since I have the Linux server running 24/7 for mail server, dns cache and other things, there was no problem adding the control system to it. It's fairly lightweight in power consumption, just a core-2 processor on a motherboard and a couple of enterprise drives.
This has been running for several years now and I have some nice trend plots of temperature and other measurements that allow me to evaluate aspects of the house design and make improvements where necessary.

Okay, I have structured cabling so easy to drop network where needed. You have peeked my interest - any more details, or would it just be as practical to use one of the off the shelf network to IO boards available now...
 

Offline montoyaaguirre

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Re: EEVblog #484 - Home Solar Power System Installation
« Reply #104 on: June 17, 2013, 05:58:33 am »
Thanks for this episode. It was great!

I live in Mexico and it seems to be the Home Solar Power System Paradise.

In Mexico we have a single electricity company and it's run by the government. They don't pay you for the energy you supply to their network. Instead, they only charge you for the difference between the kWh you take from the grid minus the kWh you supply. This means that you don't have to skim on the power consumption during night as long a you produce enough kWh hours during the day. If you supply the same amount of kWh that you consume in a given month you will get an electric bill for $0.00  If you supply more kWh than what you consume each month, you can save it for the next month up until 12 months.
Did I mention that we get 14 Hours of sun daylight in summer and 11 in winter?

Our daily energy consumption is 20kWh during summer and 12kWh during winter. Am I crazy for not having my home solar power system yet?
« Last Edit: June 17, 2013, 06:12:52 am by montoyaaguirre »
 

Offline DrGeoff

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Re: EEVblog #484 - Home Solar Power System Installation
« Reply #105 on: June 17, 2013, 06:07:17 am »
Okay, I have structured cabling so easy to drop network where needed. You have peeked my interest - any more details, or would it just be as practical to use one of the off the shelf network to IO boards available now...

The modules have 8 digital inputs, 8 digital outputs, 8 1-wire temperature ports and 4 analogue inputs. Separate termination modules are used to add relays, opto-coupling of DI's, conditioning for analogue inputs and termination for 1-wire sensors. There's also a couple of serial ports, again termination modules can be used to turn these into RS232 or RS422 ports. Power is 12VDC and the network connection is 10bT. The Microchip IP stack compiles for it, using a custom BSP and the protocol I use is an encrypted UDP protocol between the Linux server and the remotes. On the Linux server there is a custom event manager that manages the queue of incoming and outgoing events to and from the remotes, and interfaces with the database. The web system interfaces with the database as well.
I can put up some circuits and also have a PCB (100mm x 100mm) for it.
Was it really supposed to do that?
 

Offline EEVblog

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Re: EEVblog #484 - Home Solar Power System Installation
« Reply #106 on: June 17, 2013, 07:10:08 am »
I noticed you commented your house doesn't have eaves. That is an unfortunate aspect of contemporary house building in Australia. You could be adding to your A/C load in summer if the walls are radiating heat inside.

Our house isn't bad thermally. Insulation in the walls an roof do a reasonable job.

Quote
I'd be interested in just how much you modify your lifestyle to extract maximum benefit. Are you going to be out one day in the sun and thinking "I really should be home doing the dishes"?  :)

We have a lifestyle that suits this. I work 5 minutes away and come and go a lot. The wife is home 3 days a week. Things like washing can be automated time wise.
Two obvious ones are washing clothes and dishes, both can now be done during daylight hours. And any aircon use can be done during the day too to warm up or cool down for night time.
 

Offline ttp

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Re: EEVblog #484 - Home Solar Power System Installation
« Reply #107 on: June 17, 2013, 08:30:59 am »
There's an IR port which moght be interesting to connect to, and I got the meter manual from an online source which has the commands and button sequences. No detail on the interface though, but it is probably fairly rudimentary since the meter reader bloke uses it.

Try to google for IEC62056-21. IEC62056 is a international standard Data exchange for meter reading, tariff and load control, Part 21 - Direct local data exchange.
 

Offline madires

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Re: EEVblog #484 - Home Solar Power System Installation
« Reply #108 on: June 17, 2013, 10:17:52 am »
is an example of an absurdly neat US (and apparently canadian too, given by the original file name)

Neat freak here - looks just like mine!  :-+ I am proud of my absurdly neat wiring  :)

When wiring becomes an art :-)
 

Offline madires

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Re: EEVblog #484 - Home Solar Power System Installation
« Reply #109 on: June 17, 2013, 10:24:22 am »
Only if you get smart meters. They didn't install those on mine, so it seems they have no way to know my time of day usable to put me on such a scheme.
Smart meters are more popular and possibly mandatory for new installations in VIC?

We didn't have a choice. They were mandatory when the new house was built. I have 3 phases coming in and three smart meters (one includes the ripple control receiver as well). The metering box is on the outside wall and the distribution panel with around 30 RCD's on it is on the inside wall of the garage.

Smartmeters are mandatory too for new houses over here, or if you novate the main distribution panel.
 

Offline manicdoc

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Re: EEVblog #484 - Home Solar Power System Installation
« Reply #110 on: June 17, 2013, 11:00:04 am »
Okay, I have structured cabling so easy to drop network where needed. You have peeked my interest - any more details, or would it just be as practical to use one of the off the shelf network to IO boards available now...

The modules have 8 digital inputs, 8 digital outputs, 8 1-wire temperature ports and 4 analogue inputs. Separate termination modules are used to add relays, opto-coupling of DI's, conditioning for analogue inputs and termination for 1-wire sensors. There's also a couple of serial ports, again termination modules can be used to turn these into RS232 or RS422 ports. Power is 12VDC and the network connection is 10bT. The Microchip IP stack compiles for it, using a custom BSP and the protocol I use is an encrypted UDP protocol between the Linux server and the remotes. On the Linux server there is a custom event manager that manages the queue of incoming and outgoing events to and from the remotes, and interfaces with the database. The web system interfaces with the database as well.
I can put up some circuits and also have a PCB (100mm x 100mm) for it.

Hmm, most tempting. What I'm thinking at the moment is:

- Analogue input x 2 for the temperature probes
- Mains switching ouput x1

But within 4 meters of this is a 6 way irrigation controller that could be made controllable from the center. So adding in a 6 way 24v rated switching would cover that. Would be good to also pull in the rain sensor (1 digital input).

I'd really like to get all this controlled from a dedicated small box PC with the Comfort and CBus tie in - currently everything including the kitchen sink is running on the one box (Samba, email, dns cache, web proxy, spam assassin, etc).
 

Offline DrGeoff

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Re: EEVblog #484 - Home Solar Power System Installation
« Reply #111 on: June 17, 2013, 11:31:19 am »
Okay, I have structured cabling so easy to drop network where needed. You have peeked my interest - any more details, or would it just be as practical to use one of the off the shelf network to IO boards available now...

The modules have 8 digital inputs, 8 digital outputs, 8 1-wire temperature ports and 4 analogue inputs. Separate termination modules are used to add relays, opto-coupling of DI's, conditioning for analogue inputs and termination for 1-wire sensors. There's also a couple of serial ports, again termination modules can be used to turn these into RS232 or RS422 ports. Power is 12VDC and the network connection is 10bT. The Microchip IP stack compiles for it, using a custom BSP and the protocol I use is an encrypted UDP protocol between the Linux server and the remotes. On the Linux server there is a custom event manager that manages the queue of incoming and outgoing events to and from the remotes, and interfaces with the database. The web system interfaces with the database as well.
I can put up some circuits and also have a PCB (100mm x 100mm) for it.

Hmm, most tempting. What I'm thinking at the moment is:

- Analogue input x 2 for the temperature probes
- Mains switching ouput x1

But within 4 meters of this is a 6 way irrigation controller that could be made controllable from the center. So adding in a 6 way 24v rated switching would cover that. Would be good to also pull in the rain sensor (1 digital input).

I'd really like to get all this controlled from a dedicated small box PC with the Comfort and CBus tie in - currently everything including the kitchen sink is running on the one box (Samba, email, dns cache, web proxy, spam assassin, etc).

The remote I have in the tank room monitors the rainwater water tank levels and also the HWS temperatures, external light sensor and controls a 4-way irrigation system (4 24VAC solenoids on a manifold). The 1-wire DS1820B probles are a very easy option for temperature sensing, which was why I added the 8 1-wire ports to the module. The module itself also has a temperature sensor onboard, so the local temperature can be monitored inside the box. As far as switching loads, that will depend on the relays you end up using. The module outputs are open-collector 1A transistors, which is usually plenty for controlling a relay. The external termination modules are used for this purpose.

That's what I do with the Linux server that runs on the home network. It serves email (with spamassassin), dns caching, local intranet, media server (audio and video), svn repositories, samba drives, databases fro my electronic parts cataloging and BOM system, event management and control/monitoring system. External access is also allowed via SSL with client certs, so when I'm overseas I can check up on things or get access.
Was it really supposed to do that?
 

Offline tecman

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Re: EEVblog #484 - Home Solar Power System Installation
« Reply #112 on: June 17, 2013, 03:38:31 pm »
Dave:

One note.  The loss of power at higher temps is mainly due to the -2.2mv/c temco of voltage for silicon.  The voltage drops with increasing temps, and thus the power.  Here in NW USA we get max output in winter, but the sun is also at its lowest output for us.

I installed a 9.2 KW system about 18 months ago.  My end cost, after rebates and incentives, was about $ 10K.  To date I have averaged 1 MWH/month.  I did research before finalizing the system.  The Sunny Boy series was limited in the 10 KW range and after looking at other brands I opted of a Fronius.  One item that steered me in that direction was a wider (lower) range of DC input voltage.  This was an advantege in worst case conditions.  I have an ethernet interface that I can monitor the system from any internet connection.

I did the install myself.  It is on a ground mount about 30 meters from the house.  Roof was not big enough and partly shaded by trees.  In out state we have net metering, so overages in production are at the same feed-in rate as usage.  Annual overages are paid out, but I only generate about 60% of my total annual use so I always pay to the utility on an annual basis.

With my system I have had no issue with RFI or harmonic noise.  So far it has all worked very well.

paul
 
 

Offline Monkeh

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Re: EEVblog #484 - Home Solar Power System Installation
« Reply #113 on: June 17, 2013, 04:08:12 pm »
Fronius

Have you looked into extracting generation data from it without buying one of their stupidly priced converters?
 

Offline tecman

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Re: EEVblog #484 - Home Solar Power System Installation
« Reply #114 on: June 17, 2013, 05:18:03 pm »
Fronius

Have you looked into extracting generation data from it without buying one of their stupidly priced converters?

I ended up buying one of their converters.  I did, however, get a really good price on it, so I didn't feel too bad.  The data from the inverter is RS485 and the protocol is published.  I could have messed around and cobbled together a ucontroller to read the data, but when I was installing it I did not have the spare time to be messing around with it.  So I bit the bullet.

paul
 

Offline Monkeh

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Re: EEVblog #484 - Home Solar Power System Installation
« Reply #115 on: June 17, 2013, 05:20:48 pm »
Hmm, got a link to the protocol docs?

Time to get cobbling together.
 

Offline Alexei.Polkhanov

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Re: EEVblog #484 - Home Solar Power System Installation
« Reply #116 on: June 17, 2013, 07:26:36 pm »
Just generate a waveform that is in phase with and slightly higher voltage than the mains. It's very similar to a synchronous motor drive.
Hmm what happens when one of your neighbors will connect his inverter to mains? He will try to be slightly higher, slightly ahead too. Then they going to race, who is higher?
 

Offline tecman

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Re: EEVblog #484 - Home Solar Power System Installation
« Reply #117 on: June 17, 2013, 07:36:50 pm »
Just generate a waveform that is in phase with and slightly higher voltage than the mains. It's very similar to a synchronous motor drive.
Hmm what happens when one of your neighbors will connect his inverter to mains? He will try to be slightly higher, slightly ahead too. Then they going to race, who is higher?

You assume (at least in the US) that the grid is a very low impedance system, and small inputs/outputs to the grid will not have any noticable effect on the grid's voltage or frequency.  It would take many 10's of megawatts to move things enough to be seen.

paul
 

Offline tecman

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Re: EEVblog #484 - Home Solar Power System Installation
« Reply #118 on: June 17, 2013, 07:45:59 pm »
Hmm, got a link to the protocol docs?

Time to get cobbling together.

I do have a manual on the interface that I had downloaded from Fronius, titled "Fronius Interface".  I can not find it on their site, after a quick look, but perhaps if you dig you can find it.

paul
 

Offline Alexei.Polkhanov

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Re: EEVblog #484 - Home Solar Power System Installation
« Reply #119 on: June 17, 2013, 08:13:50 pm »
You assume (at least in the US) that the grid is a very low impedance system, and small inputs/outputs to the grid will not have any noticable effect on the grid's voltage or frequency.  It would take many 10's of megawatts to move things enough to be seen.
Grid is clustered into small sections. I heard from actual home owners that they had problems when several inverters operate in same area/street for example.

Also all inverters will have to shut off, somehow, automatically when mains are turned off otherwise how utility company going to work on power lines? I am not entirely sure how that "turn-off" feature works, but there have to be something otherwise it is a big problem.
« Last Edit: June 17, 2013, 08:58:49 pm by Alexei.Polkhanov »
 

Offline Leon

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Re: EEVblog #484 - Home Solar Power System Installation
« Reply #120 on: June 17, 2013, 09:02:02 pm »
A normal inverter will always shut down operation when the AC signal is lost. Some have an "island" mode in which they can still power the house, but in all cases there will be no AC generated for the outside world.
 

Offline Alexei.Polkhanov

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Re: EEVblog #484 - Home Solar Power System Installation
« Reply #121 on: June 17, 2013, 10:04:28 pm »
A normal inverter will always shut down operation when the AC signal is lost. Some have an "island" mode in which they can still power the house, but in all cases there will be no AC generated for the outside world.
Yes, obviously it works somehow.  I have done some Googling, I found lot of references to IEEE 1547 which is the standard that describes "distributed" power generation signalling or something like that.

But after looking at 50 PowerPoint decks I am still not sure how exactly does it work in simple case when lets say 2-3 houses have inverters running on same street?  They somehow to turn off when "they do not detect presence of grid". How does your (micro) inverter see difference between AC power supplied by your power company and your neighbor's inverter?

 

duskglow

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Re: EEVblog #484 - Home Solar Power System Installation
« Reply #122 on: June 17, 2013, 10:09:58 pm »
Interestingly enough, Wikipedia has a pretty thorough treatise on this problem and some solutions.

http://en.wikipedia.org/wiki/Islanding
 

Offline mtdoc

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Re: EEVblog #484 - Home Solar Power System Installation
« Reply #123 on: June 17, 2013, 11:21:16 pm »
I have a 4500 watt "Grid Interactive" system which means I am grid tied with battery back up so that I have power in case of grid failure - which is not uncommon where I live.

In the US all grid tied or grid interactive inverters must meet UL 1741 anti islanding certification. I'm not sure if  IEEE 1547 is necessary but my inverter meets it as well.

BTW - many people in US areas with unfavorable electricity rate structures (peak, off peak differences etc) use grid interactive systems to allow them to be totally "off grid" during high cost hours and grid tied during low cost hours.

Makes no difference for my system since I pay a straight $0.065 per Kwh am net metered and get an extra $0.18 for my PV production.

 

Offline Dreso12

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Re: EEVblog #484 - Home Solar Power System Installation
« Reply #124 on: June 17, 2013, 11:23:56 pm »
For PV inverters connected to the grid it is mandatory to have an anti-islanding mode. This works by constantly monitoring voltage and frequency of the grid, if there is a deviation the inverters stop working. The idea is to avoid having hazardous voltages if an area of the grid which is disconnected, for example for maintenance.

Depending on the country the maximum/minimum values varies, but the ranges for voltage and frequency are small, it is necessary as if you have many inverters in one disconnected area of the grid they can feedback each other and continue to work so the ranges have to be small. This is why if you are in a poorly cabled area at the end of the grid you can have problems if many inverters are connected as the voltage can increase over the limits and start connecting/disconnecting.
 


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