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Author Topic: How to make best use of Engergy created - technical question  (Read 5870 times)
bautsche
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« Reply #15 on: April 23, 2016, 01:01:38 PM »

heatherhopper: Yes, I could theoretically produce 6.565kWp with the solar panels, counting both south facing AC coupled (9*285kWp), east facing DC coupled 6*250kWp and west facing DC coupled 10*250kWp. This is of course not very likely, not least because of the differing orientation of the panels. A long time ago I had a look at this: http://www.solarguide.co.uk/solar-pv-calculator It allows you to calculate the potential yield of your panels and east and west pretty much work out at 50% of south facing panels... That anecdoteally matches with my actual experience.
I think ultimately, I should get a charge controller for the direct connected panels though...

Re generator raising the frequency: it inevitably will, I was thinking of actually mounting any frequency sensing equipment with the SI and thus my control panel. I can then do logical ands between whether the generator is running (bearing in mind it could also be started by the Trace, which is unlikely, but possible) and the frequency of the grid. I can then send a control signal (or several once I get around to having more than one dump load, but that's a project for another year) to my dump loads and start them via relay.

I'm struggling with the various names of the various bits of kit I will want, so your post is very useful and will allow me to search the internet for parts...

Every time I do a bit more work on this, I wonder if I wouldn't be better off dusting up my old assembler programming skills and/or investing some time in the openhardware movement and actually programme something to do all the clever stuff for me. With a couple of pieces of sensing equipment (voltages, currents, frequency) you could then easily programme very complex scenarios instead of implementing them in discrete bits of hardware. Arduino or Raspberry Pi seem to spring to mind. I suspect this is going to be a much larger project though....

Of course, since all of this is home made and self-installed and I'm off grid, I get neither feed-in tariff nor generation tariff, so I'm not fussed about not using electricity, I'm more fussed about the fact that I might also save me some oil by not having to run the water heater so often...
This in and of itself is of course another interesting project as the combined cooker and water heater (an alpha range, keep hand off if you have any sense everyone, the current owners are doing their best to kill off any spare parts) has been installed by the previous owners and god alone knows what they were thinking when they were wiring the thing up, but the upshot is, there's no temperature control on the water tank, it's just a case of "we'll run it three times a day and hope the water is hot enough but not too hot"....
The water tank needs rewiring and the cooker replacing, it's had so many bodges to keep it going for "just a bit longer"...
Anyone fancy sponsoring me or telling me next week's lottery numbers is very welcome....  Grin

Eric
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billi
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« Reply #16 on: April 24, 2016, 12:09:33 AM »

Hi Billi.

Perhaps I don't fully appreciate how charge controllers work, but wouldn't I have to completely disable any and all protections on the SI and SB? The charge controller just works on battery voltage, doesn't it? If so, I could already do that with the Trace inverter. What stops me from doing it is that I'm disabling the SI's protection of the battery bank.....
Eric


 Have not read  and found much  positive  information about AC coupling  and battery care ,  as an ideal solution   , I always  would let allow  a charge-controller  to do  the final charge


But in your case it sounds  like that you just have to switch the Trace on  to power the immersion  .... there should be a relays that can be programmed  ....  no ?






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1.6 kw and 2.4 kw   PV array  , Outback MX 60 and FM80 charge controller  ,24 volt 1600 AH Battery ,6 Kw Victron inverter charger, 1.1 kw high head hydro turbine as a back up generator , 5 kw woodburner, 36 solar tubes with 360 l water tank, 1.6 kw  windturbine
bautsche
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« Reply #17 on: April 24, 2016, 07:13:43 AM »

Hi Billi.

Yes, that was exactly what I thought, but alas, the SI's battery protection very effectively prevents the battery voltage from going too high, so I'd have to start the immersion heater way too early in the charge cycle... Sad
That's potentially very expensive as it might mean I've just used electricity that could have gone into the batteries to power the immersion and I then have to run the generator to produce more electricity...

Eric
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billi
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« Reply #18 on: April 24, 2016, 11:39:46 AM »

Hi Eric  , what make is your chargecontroller ?  and how much kW PV do you have in total  ?  Is it 4000 watt via a chargecontroller   and the rest via a GTI ?


The outback MPPT charger or the Midnite classic ( i think )  both have a   mode  to fully charge a battery bank , but  pass on surplus  via a relays to an immersion  , so say the battery charge only needs 1500 watt , while in absorption charge , but the PV is generating in total say 3000 watt , then those 1500 watt surplus  is diverted into the immersion  via a PWM   method  signal

Something to read about here http://solarhomestead.com/diversion-load-for-skystream/  or on the outbackforum "how to use every electron"

I considered that years back   , and studied the details on the outback forum  , but that would have meant  to 100% make sure that all power  is consumed    and that the solid state relays  that would have been needed  to work with the Outback controller  would have to operate bullet prove  ....   so i got some wet feet  and  decided to just let my Victron Inverter relays  switch/ control    the immersion / radiator in winter

not as elegant and efficient  but less money and brains spent

I never made it to get a heatpump for hot water ( that was a dream from the start)  and as they are costing bellow 1000  its still a good option for us offgriders  as they  use only about 1/3   of power

So switching on something that uses 700 watt instead 2500 (for the same amount of hot water)   is  more or less a now brainer with that amount of PV you have ( and still get the battery full)

.... I am still thinking loud  about options..... Tongue

Is there a reason  why your SB3800  has only under 3000 w of PV ?  and  do you think  the immersion with only 1500 watt would make more sense/ act more gentle  ?


Billi
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1.6 kw and 2.4 kw   PV array  , Outback MX 60 and FM80 charge controller  ,24 volt 1600 AH Battery ,6 Kw Victron inverter charger, 1.1 kw high head hydro turbine as a back up generator , 5 kw woodburner, 36 solar tubes with 360 l water tank, 1.6 kw  windturbine
bautsche
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« Reply #19 on: April 24, 2016, 11:58:21 AM »

Hi Billi.

I'm using the Sunny Island as a charge controller. The DC coupled solar doesn't have any charge controller associated with it. I know that's a whole in the setup and will, some day, be fixed... Wink

My problem is that I want the bank to charge, but the SI is very effective at reducing the charge rate towards the end of the charge phase, so it's not a simple on/off scenario. This way however, the battery voltage never gets "too" high, or put another way, high enough to trigger my overvoltage relays on the Trace.

I agree with you that smaller steps of dump loads would make life much easier, but that's a project for another day when I replace the hot water tank (at the going rate, there'll be very little left from the original place that we bought, already every single technical item on the farm has failed and been completely replaced. the only thing still hanging on is the hot water system and cooker - no we don't have central heating, don't go there....).

The SB3800 only has 9 panels on it. That's the limit of space I have on the only south facing roof.
See also here: http://www.navitron.org.uk/forum/index.php/topic,26880.0.html

Eric

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heatherhopper
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« Reply #20 on: April 25, 2016, 11:10:33 AM »

Quote
Re generator raising the frequency: it inevitably will, I was thinking of actually mounting any frequency sensing equipment with the SI and thus my control panel. I can then do logical ands between whether the generator is running (bearing in mind it could also be started by the Trace, which is unlikely, but possible) and the frequency of the grid. I can then send a control signal (or several once I get around to having more than one dump load, but that's a project for another year) to my dump loads and start them via relay.
Why can you not use the generator start signal (from either/both inverters) to drop a contactor on the feed to any dump load while the generator is active - simple load shedding? You did say you have spare control signal cabling, would this be adequate to provide the signal to the location of the hot water tank? This is what I do for my primary dump loads although they are relatively local to the SI so cabling is minimal.
A Frequency Protection Relay (I use Eltime relays but the Hobut you quoted is similar) and contactor on the immersion side of that load shedding contactor is then all you need for the single dump load. This would give on/off control and 3kW is probably too big for your generation potential but you could substitute the Frequency Protection Relay with a Frequency Transducer and SSR - the Transducer providing a low voltage signal to drive the SSR in direct proportion to frequency variation.
Sorry to belabour the subject but if you do find a better solution to fit with an SI as your main charge controller I would be very happy to hear about it. If you start adding DC charge controllers into your system I think you will almost inevitably have to go down the route Paul has taken to get it working satisfactorily. Note that Midnite make controllers that communicate directly with the SI so maybe worth a look but so are used GTIs for AC coupling.
If you are willing to start some programming then this will broaden your options but personally I have more fun brushing nettles over my eyeballs.

Quote
Have not read  and found much  positive  information about AC coupling  and battery care ,  as an ideal solution   , I always  would let allow  a charge-controller  to do  the final charge
billi - I am always a bit puzzled by what you believe an SI does so significantly differently when controlling the charging of a battery bank.

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« Reply #21 on: April 25, 2016, 11:32:36 AM »

Quote
Quote
Have not read  and found much  positive  information about AC coupling  and battery care ,  as an ideal solution   , I always  would let allow  a charge-controller  to do  the final charge
billi - I am always a bit puzzled by what you believe an SI does so significantly differently when controlling the charging of a battery bank.
me too


Just a question ,  is the Sunny Island allowing a daily absorption charge ?
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1.6 kw and 2.4 kw   PV array  , Outback MX 60 and FM80 charge controller  ,24 volt 1600 AH Battery ,6 Kw Victron inverter charger, 1.1 kw high head hydro turbine as a back up generator , 5 kw woodburner, 36 solar tubes with 360 l water tank, 1.6 kw  windturbine
bautsche
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« Reply #22 on: April 25, 2016, 11:33:00 AM »

Why can you not use the generator start signal (from either/both inverters) to drop a contactor on the feed to any dump load while the generator is active - simple load shedding?
Sorry, that's exactly what I meant.

A Frequency Protection Relay (I use Eltime relays but the Hobut you quoted is similar)
It's impressive how when you search for specific stuff on the internet for electronics, it's very hard to find. I had not found the eltime ones, but putting eltime in the search string does of course.... I think I might stick with eltime, I've had kit from them in the past and never had any trouble...

3kW is probably too big for your generation potential but you could substitute the Frequency Protection Relay with a Frequency Transducer and SSR - the Transducer providing a low voltage signal to drive the SSR in direct proportion to frequency variation.
That sounds like the way to go, possibly. I'll have to look into this.
What I have on the drawing board at the moment is a delay timer before the signal is given (just a few minutes to make sure that it's not just a case of brief moment of more sun) and another delay keeping the dump load active for say 30mins post frequency going down again. I appreciate that what this'll do is make the battery go up and down a bit, but 30mins shouldn't be too bad...

Sorry to belabour the subject but if you do find a better solution to fit with an SI as your main charge controller I would be very happy to hear about it. If you start adding DC charge controllers into your system I think you will almost inevitably have to go down the route Paul has taken to get it working satisfactorily. Note that Midnite make controllers that communicate directly with the SI so maybe worth a look but so are used GTIs for AC coupling.
Just had a look at the Midnite ones. The issue I have with all of the charge controllers is that I might just as well go for a Sunny Boy, price wise and then have all my kit definitely working together. (a model that's just become obsolete will do me fine and there seem to be plenty around that installers don't want to put in anymore on account of a newer model being available that are still brand new in the box.)
The roof that the direct connected panes are one is that of a shed that is slowly but surely disintegrating. I'm kind of tempted to leave it as it is and hope I come into 30k soon to replace the building. The panels can then go back up with a Sunny Boy controlling them....

Eric
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bautsche
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« Reply #23 on: April 25, 2016, 11:33:23 AM »

Just a question ,  is the Sunny Island allowing a daily absorption charge ?

Yes, it does.
Eric
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heatherhopper
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« Reply #24 on: April 25, 2016, 12:06:02 PM »

Quote
It's impressive how when you search for specific stuff on the internet for electronics, it's very hard to find. I had not found the eltime ones, but putting eltime in the search string does of course.... I think I might stick with eltime, I've had kit from them in the past and never had any trouble...
I've also found general searching frustrating. For this kind of thing you need to look for industrial suppliers. My Eltimes are several years old and still fine. Go for "over-protection" specifically. They come factory preset to your trigger frequency and delay time specification and have potentiometers for further adjustment but these need some fiddling to get just right if you do need to adjust. 

Quote
That sounds like the way to go, possibly. I'll have to look into this.
What I have on the drawing board at the moment is a delay timer before the signal is given (just a few minutes to make sure that it's not just a case of brief moment of more sun) and another delay keeping the dump load active for say 30mins post frequency going down again. I appreciate that what this'll do is make the battery go up and down a bit, but 30mins shouldn't be too bad...
Delay timer should work fine - I operate my on/off in real time (necessary with the turbine but maybe not so with PV only) and the battery variation is minimal. I have found 1kW loads are ideal but also have 2kW and 3kW loads all in a rising frequency series. Frequency change in my system is not too rapid but this depends as much on Inverter and battery size as generation I imagine. There is some light flicker if more than one 3kW load is operating. Changing to proportional control is just a logical improvement.

Quote
Just had a look at the Midnite ones. The issue I have with all of the charge controllers is that I might just as well go for a Sunny Boy, price wise and then have all my kit definitely working together. (a model that's just become obsolete will do me fine and there seem to be plenty around that installers don't want to put in anymore on account of a newer model being available that are still brand new in the box.)
The roof that the direct connected panes are one is that of a shed that is slowly but surely disintegrating. I'm kind of tempted to leave it as it is and hope I come into 30k soon to replace the building. The panels can then go back up with a Sunny Boy controlling them....
Couldn't agree more - long live AC coupling with second hand stuff!
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Off grid AC coupled, 6kW Proven, 2.8kW PV, SMA SI/SB/WB Inverters, 4x576ah Rolls batteries @ 24v, 25kW Biomass Boiler, Wood Stoves, Spring/Well water. Sorry planet - I did try.
heatherhopper
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« Reply #25 on: April 25, 2016, 12:18:59 PM »

Quote
Just a question ,  is the Sunny Island allowing a daily absorption charge ?
The SI performs the same charge routine as any other good charger. It has rather more scope for adjustment of the different stages than say a dip switch configurable charger and I imagine therein lies some of the problems people might have.
Frequency Shift seems to attract some myth - it is perhaps most usefully treated in off-grid set-ups as a simple varying signal representing battery voltage for controlling external functions both on the SI grid and external to it.
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« Reply #26 on: April 25, 2016, 12:36:42 PM »

Ok  , i did not realize or have read different ,  that one can  have a daily absorption charge  ....easily programmed

Anyway SI is just /was  an off grid inverter


One Chargecontroller like the Outback FM 80  or the midnite classic  or a Studer 120 will cope with more than 5000 watt of PV  and one gets 1-2 controllable relays with them

I have not found an easier solution yet ,

Beside those Taiwan inverter /chargers

Billi



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1.6 kw and 2.4 kw   PV array  , Outback MX 60 and FM80 charge controller  ,24 volt 1600 AH Battery ,6 Kw Victron inverter charger, 1.1 kw high head hydro turbine as a back up generator , 5 kw woodburner, 36 solar tubes with 360 l water tank, 1.6 kw  windturbine
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« Reply #27 on: April 25, 2016, 03:14:59 PM »

billi - I'm sure that if anyone was setting up a new system the controllers you mention are very good candidates.
Trouble is Eric already has a system established with both his primary PV AC coupled and a SI grid established. Adding new DC controllers into the mix can, of course, be done but as has been well demonstrated there are complications using them with a SI and AC coupled GTI and I would question whether this is sensible since it could mean making the GTI and/or a large chunk of the SI functionality redundant - rather different to already having all the different gear and making best use of it like Paul has done.
The original post was all about easily diverting excess power to an immersion in the current set-up which is why I suggested Eric needed to consider where he was heading in my first reply. It can all be done one way or another but if not thought through could become a real mishmash of competing components, some of which are a little too expensive to have sat around largely idle.
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« Reply #28 on: April 25, 2016, 10:42:41 PM »

Hi HH  , sure a mix as we know , can be quite complex


That why i said in my first post,  let a chargecontroller do the whole  and  forget about the AC -coupling / or and  leave it to the controller  to do the charge  ,  and just use the AC -coupling in bulk mode


Billi



Sure i did not  read  the 300 meter distance , so    48 volt DC over 300 m  is not sounding very clever as an  idea Billi .....  fight , but an outback FM chargecontroller can as well be used to switch on AC  ideas like the Trace inverter powering the 3 kw immersion .... after absorption 
« Last Edit: April 25, 2016, 11:03:21 PM by billi » Logged

1.6 kw and 2.4 kw   PV array  , Outback MX 60 and FM80 charge controller  ,24 volt 1600 AH Battery ,6 Kw Victron inverter charger, 1.1 kw high head hydro turbine as a back up generator , 5 kw woodburner, 36 solar tubes with 360 l water tank, 1.6 kw  windturbine
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