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Author Topic: How to make best use of Engergy created - technical question  (Read 5958 times)
bautsche
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« on: April 22, 2016, 01:46:56 PM »

All.

It seems to be the time for stupid questions, my apologies.

A bit of background first:
I've got a Sunny Island 5048 inverter which shares its 48V lead acid battery bank with a Trace SW4048. The trace sits there and does nothing, but it's available as a backup should the SI fail.
Also directly attached to the battery bank is an array of 16 250W panels, but they are half east, half west facing.

I now have a Sunny Boy 3800 which has 9 285W panels, south facing, but that's on a different building and I don't fancy running in any control cables as it would require digging up the farm track.

I have an ideal dump load in the form of a 3kW immersion heater in the water tank in the house, but again, that's about 300m away, but there are spare pairs of control cables going between the house and the location of the Sunny Island, Trace and batteries.

I'm wondering what people would suggest I use to divert excessive energy into the immersion heater.
As it stands, when the battery bank runs full during a sunny day, the SI simply raises the grid frequency which causes the Sunny Boy to reduce output. So far so good.
I guess, I'm not that keen to shut that safety feature down (not that I'm totally clear on how I would do it if I wanted to, I think it would require changes to the Sunny Boy (tell it that it's on a fixed grid, not off grid) and the Sunny Island (something with the charger settings, but I'm not clear what).
I have considered using a frequency dependent switch, but the minute the immersion heater comes on, the SI would lower the frequency again and it would turn itself off again. Also, such a device doesn't seem readily available and I wonder how easy it would be for me to come up with a sufficiently precise circuit to achieve this.
What I originally wanted to do is go on battery voltage (which I can easily do with the built-in relays of the Trace inverter), but the Sunny Island's turning down of the output of the Sunny Boy very effectively prevents the battery voltage from going "too" high.
I have also considered using the Sunny Island's Load Shedding function in reverse, i.e. based on the SOC of the batteries turn on Relay 2, I can then invert that signal and logically and it with "is the generator running" and I should be OK. This would be a very custom solution though....

This situation cannot be unique, so I was wondering what other people are doing?
Any great suggestions, advantages, disadvantages to your methods?
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billi
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« Reply #1 on: April 22, 2016, 02:16:52 PM »

Hi , perhaps i do not understand all , but just use a charge controller and  dump  the surplus ...

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heatherhopper
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« Reply #2 on: April 22, 2016, 02:20:35 PM »

Wrestled with this very SI based situation myself.
I have been operating a series of frequency protection relays to control different sized immersions and heaters for a few years now and it works very well - a little on/off perhaps to be ideal but nonetheless keeps everything AC coupled, Turbine and PV at full output and the SI retains full control of battery charging. Did have some DC coupled generation a while ago and it worked fine with that mix also.
Currently installing frequency driven SSRs to replace (at least at the lower end) the frequency relays and give proportional control of the primary immersions. Should be done in the next week or two (depending on weather!) and I'll let you know how this works out.
None of this comes cheaply when you add up all the bits and pieces.
Others on here adopt different approaches which seem to work well - camillitech and Nowty notably with the former's perhaps more applicable for your mixed AC/DC system.
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bautsche
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« Reply #3 on: April 22, 2016, 03:29:12 PM »

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
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nowty
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« Reply #4 on: April 22, 2016, 04:14:15 PM »

I use a solamiser (similar to an immersun solar diverter) to heat a hot water tank with my Off Grid system, keeps the Sunny Boy maxed out all day after the batteries are full.

Its been running for over a year now and has doubled my solar yield.

However it will only work with an AC coupled system, sounds like yours is DC coupled.

See post below for more info.
http://www.navitron.org.uk/forum/index.php/topic,23664.msg275079.html#msg275079
« Last Edit: April 22, 2016, 04:23:31 PM by nowty » Logged

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Hot water storage of 15+ kWh.
Heat storage of 15+ kWh.
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camillitech
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« Reply #5 on: April 22, 2016, 05:53:11 PM »

Hi Eric,

I'm guessing your SB3800 is 'AC coupled' on a building quite away from everything so you're just using existing cable that goes to that building. Basically then that rules out a charge controller for that then. What are you using to regulate the east/west array? It seems to me that your only option is to dump as AC into the immersion due to distance to the house and cable issues.

There are many ways of doing what you require, just one of these connected to your immersion would probably be the simplest http://www.windandsun.co.uk/products/Energy-Monitoring-and-Control/Frequency-Controlled-Switches#.VxpKl_krLIU I'm guessing HH uses something similar. There may however be some conflict with your DC coupled array, depending, I guess on what sort of charge controller you have and what it's settings are. The SI is very particular on how it charges the batteries so you could end up with a dump load fire if you have one. You always need to keep the controller settings higher than the SI's.

Using the Trace or SI relays would also work, if not a little 'clunky' but for that you'd be better turning off the FSPC, not a problem if you have a controller capable of diverting all the excess DC when the stat opens.

My system incorporates a circuit designed by Hugh Piggott that uses PWM Tri Stars to trigger SSR's into immersions. It has the beauty of diverting the AC smoothly (like an Immersun) but falls back to the DC PWM if the stat opens or the immersion fails. Again, my FSPC is off.

By far the simplest and easiest, is of course to ditch the FSPC and just divert excess DC into your immersion. However, with large properties and array's/batteries/inverters miles from your tank this is seldom practical. If it is possible though, I've a 3kW 48V DC immersion element you're welcome to have.

Good luck, Paul
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http://lifeattheendoftheroad.wordpress.com/

'Off grid' since 1985,  Proven 2.5kW, Proven 6kW direct heating, SI6.OH, 800ah Rolls, 4.75kW PV ,4xTS45, Lister HR2 12kW, , Powerspout pelton, Stream Engine turgo, 60 x Navitron toobs and a 1500lt store. Outback VFX3048 and 950ah forklifts for backup,
bautsche
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« Reply #6 on: April 22, 2016, 07:03:19 PM »

Hi Nowty.

I've had a look at the Immersun. Looks like a neat way of doing it, but the Sunny Island and the Sunny Boy are about 20m apart with the concrete farm drive in between.... I think that rules that solution out, otherwise, that looks like it would have been a great idea.

Paul: I'm not really controlling the DC coupled panels at all. I know I should, because if my loads were to fall away for some reason (digger through cable or something), the DC coupled panels could destroy the battery bank. Ideally, I should have a charge controller in between, but alas.... As it stands, the DC coupled panels rarely generate (much) more than my standing load (side job in IT, computers are always running, so is the lighting in the poultry sheds, freezers for the pork we sell, etc.). Only with the new AC coupled array am I finally seeing the batteries being recharged during the day, so the generator doesn't need to run over night.
I think the frequency controlled switch you have liked to, sounds like just the ticket. The house unfortunately is too far away to use low DC voltage to drive a heater over the existing cable, and putting a new one in would involve ripping through concrete drive (twice) and a 300m or 350m run of cable, so that's not in the budget or available time, unfortunately.... ;-)

The other advantage of the frequency controlled switch is that it'll also dump the power from the DC coupled panels (provided of course the cable in between doesn't go) as the SI will still try to up the frequency as it doesn't know if there is any AC power being generated as well as the DC power it sees, so it will try and tell any AC power source to scale back by upping the frequency even if there isn't any AC power source left.

Thanks for all your pointers guys, very much appreciated.
Eric
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marcus
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« Reply #7 on: April 22, 2016, 08:49:11 PM »

I'm not sure I've got the layout right in my head, but I'm thinking the immersun might work:

the SI and the SB are 20m (and a concrete track) apart with no comms lines. The immersion (house) is 300m away but there are spare control cables available (between the house and SI? ).

if that's the right layout then I'd have the immersun at the house in the immersion circuit with the controlling current-transformer at the SI connected via a pair of control cables - assuming the Immersun can cope with 300m of cable in it's CT line. I don't think it matters where the SB is.
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camillitech
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« Reply #8 on: April 22, 2016, 09:16:56 PM »

I'm not sure I've got the layout right in my head, but I'm thinking the immersun might work:

the SI and the SB are 20m (and a concrete track) apart with no comms lines. The immersion (house) is 300m away but there are spare control cables available (between the house and SI? ).

if that's the right layout then I'd have the immersun at the house in the immersion circuit with the controlling current-transformer at the SI connected via a pair of control cables - assuming the Immersun can cope with 300m of cable in it's CT line. I don't think it matters where the SB is.

Hi Marcus,

how would the Immersun know when it was to work? The current needs to 'backfeed' into the SI to charge the batteries via the SI. I'm sure there is a way of doing it that way but I can't think of it right now.

Eric,

think you'll be fine without the controller with all that 'base load' but have you got a shunt and is it wired correctly? The system will work OK without it (mine did for months) but it'll work far better if the SI can accurately monitor what those 'DC coupled' panels are doing.

Cheers, Paul
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http://lifeattheendoftheroad.wordpress.com/

'Off grid' since 1985,  Proven 2.5kW, Proven 6kW direct heating, SI6.OH, 800ah Rolls, 4.75kW PV ,4xTS45, Lister HR2 12kW, , Powerspout pelton, Stream Engine turgo, 60 x Navitron toobs and a 1500lt store. Outback VFX3048 and 950ah forklifts for backup,
marcus
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« Reply #9 on: April 22, 2016, 10:07:26 PM »

Quote
Insert Quote
Quote from: marcus on Today at 08:49:11 PM
I'm not sure I've got the layout right in my head, but I'm thinking the immersun might work:

the SI and the SB are 20m (and a concrete track) apart with no comms lines. The immersion (house) is 300m away but there are spare control cables available (between the house and SI? ).

if that's the right layout then I'd have the immersun at the house in the immersion circuit with the controlling current-transformer at the SI connected via a pair of control cables - assuming the Immersun can cope with 300m of cable in it's CT line. I don't think it matters where the SB is.

Hi Marcus,

how would the Immersun know when it was to work? The current needs to 'backfeed' into the SI to charge the batteries via the SI. I'm sure there is a way of doing it that way but I can't think of it right now.

well I was thinking the current trans of the immersun would be on the output of the SI (connected via the available (?) control cables) and so the immersun would divert to the I/H when the current started to backfeed into the SI - i.e. the current trans need to be at the SI, 300m from the house, although I still don't know if it can handle that distance on the sense circuit.
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camillitech
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« Reply #10 on: April 22, 2016, 11:14:46 PM »



well I was thinking the current trans of the immersun would be on the output of the SI (connected via the available (?) control cables) and so the immersun would divert to the I/H when the current started to backfeed into the SI - i.e. the current trans need to be at the SI, 300m from the house, although I still don't know if it can handle that distance on the sense circuit.

Hi Marcus,

but the current needs to flow into the SI to charge the batteries and out to service the loads. When the loads are light the SB feeds them with surplus going into the SI to charge the batteries and when loads are heavy current flows the other way. The Immersun has no way of knowing when the batteries are full unless you tell it, Nowty sorted something out,

QUOTES
“Are you certain , that  enough  Sunny Boy s power flows backwards into the Sunny Island to charge the batteries ?”

“The trouble is that you are likely to end up with flat batteries if you are using the Sunny Island as a charger.”


I won’t end up with flat batteries because when I have wired the system up properly the immersun type device won’t be able to turn on until the batteries are fully charged.

I already use the Sunny Islands multifunction relay when the batteries are 90% (highest setting the SI will allow) + cascade that with an external time delay relay of 1 hr to switch my grid circuits to “off grid” early in order to increase the yield. This has worked very well over this summer.

I will add in another 1hr time delay relay, so the immersun type device will only turn on when the batteries are 90% + 2 more hrs charge. From that point the immersun type device will guarantee no discharge from the batteries, even when the sun goes behind clouds.

In the summer months 90% + 2 hrs will still be reached mostly before midday. Still plenty of time left to heat up a 150 litre water tank with 10 units or so.

I did note in my experiment yesterday that the immersun type device was allowing nearly 200w to flow into the Sunny Island so it should also keep it nicely topped up on float too.


http://www.navitron.org.uk/forum/index.php/topic,23664.msg275112.html#msg275112

However, there was a little more to it than fitting the current sensor. I'm sure I spoke to a man at Solic about this and he reckoned a 100m max between the sensor and that particular device (the MkI Solic) though things may have 'moved on' since then.

Cheers, Paul
« Last Edit: April 22, 2016, 11:17:26 PM by camillitech » Logged

http://lifeattheendoftheroad.wordpress.com/

'Off grid' since 1985,  Proven 2.5kW, Proven 6kW direct heating, SI6.OH, 800ah Rolls, 4.75kW PV ,4xTS45, Lister HR2 12kW, , Powerspout pelton, Stream Engine turgo, 60 x Navitron toobs and a 1500lt store. Outback VFX3048 and 950ah forklifts for backup,
marcus
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« Reply #11 on: April 22, 2016, 11:49:31 PM »

oh ok, I probably didn't read through nowtys solution properly TBH, and i did have my doubts about 300m runs for the immersun anyway.
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bautsche
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« Reply #12 on: April 23, 2016, 07:57:39 AM »

Hi Paul.

Yes, I have the shunt. I did operate mine without one for a short while, long before any solar panels came into it. But I was using a three phase generator (this is where all sorts of people are going to shoot me on account of the imbalanced load to the generator now) and I had one phase connected to the SI and one to the Trace to charge the battery bank. Worked only for a couple of weeks before the SI went potty about what the state of charge of the battery bank may be... :-O

The shunt works nicely. I'll have to upload a pic of my set up one day, I'm (surprise, surprise) quite proud of my handywork... ;-)

Marcus: the way the clamps work, I seriously doubt they would do a 300m run, very short runs only as a rule. There's very little voltage and very little current on these, they will not survive long cable runs. The Immersun, if I understand it correctly, needs to understand the difference between electricity generated and electricity used, so the clamps as per nowty's solution would need to be on the SI and the SB to get that measurement, too. And there's no cables between the array/SB and the SI other than the power cable.... :-(

Paul: I've also found this on the internet: https://www.hobut.co.uk/protection-relays/frequency-protection-relay
Should allow me to build my own http://www.windandsun.co.uk/products/Energy-Monitoring-and-Control/Frequency-Controlled-Switches#.VxpfKtXqwlB
Just need to work out what comes out cheaper.... ;-)

Thanks again everyone.
Really appreciated.
Eric
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heatherhopper
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« Reply #13 on: April 23, 2016, 10:24:19 AM »

Eric
Having been through this decision process myself I suggest it might be worth taking stock of exactly what you want to achieve before you start purchasing the bits - as I said in my earlier reply it can get expensive. It would appear you are leaning towards a similar AC side solution to my own which I consider the best particularly if you don't want or already have DC chargers. The Immersun type device solution seems to rule itself out due to your grid layout but the solution that Nowty uses (based on SOC) is not ideal for off-grid situations anyway if you have generating capacity in excess of your SI charging capacity. Bear in mind that the SI charge control is effectively compromised if you have DC generation and don't have sufficient AC coupled diversion - this where Pauls solution comes in.

If you want to simply divert to a single 3kW immersion and allow the SI to frequency shift and throttle any generation above that then either the Amber product from windandsun or a frequency protection relay coupled with a single contactor will work fine. These can be installed anywhere on the SI Grid. I have a couple of the original Amber plug-in type switches still operating four years down the line. They do have a mandatory random time delay built in though which is not ideal for my purposes (I need immediate response) and the trigger frequency is only selectable by dip switch so limited. Frequency protection relays are available from several manufacturers and can be ordered factory preset but also have potentiometers for fine adjustment - I find you need to use this in practice if you have more than one installed and want diversion loads to operate in series.

If you want to divert all excess power (you have potentially >4.5 kW?) to a useful destination (and why wouldn't you) you will need a bigger immersion or more switches/relays.

Ideally proportional control of any diversions is where you wan to be. I am installing a frequency transducer to provide a proportional control signal to drive phase angle SSRs controlling the ouptuts of various immersions/heaters in parallel backed up by the existing frequency relays. I have considered using an Arduino or PLC to filter the transducer signal for series control but it all became a bit cumbersome and this can always be retrofitted. An Arduino or similar could be configured to replace the transducer I guess but again this is all too much leg work for my liking.

Depending on where you source from the Amber switch and frequency relay/contactor are similarly priced at around £100 and cheaper than the better Immersun type devices. A frequency transducer (factory set for a specified range) is £100-150. SSRs range from <£50 to £50-100 depending on quality, size and inclusion of heatsink.

If your generator delivers a variable frequency you will need a method of isolating any frequency controlled diversions when it is operating unless you want to burn diesel to heat water and/or have any protection contactors dropping out and the SI SOC going temporarily wobbly in low battery situations. Easily done with a load shedding contactor controlled by an SI relay but if diversions are on different circuits/spurs you would need extra contactors.
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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.
nowty
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« Reply #14 on: April 23, 2016, 11:56:18 AM »

All,

Just to clarify a few things with my system.

1)   The current sensing clamp can be anywhere on the live wire between the SB and SI subject to (2).

2)   The loads MUST be between the SB and the current sensing clamp.

3)   An “Immersun 2” will not work, I have tried it and its anti flicker characteristics make it too slow to act and the SI changes the frequency too quickly. I use a Solamiser and it works, it dumps the power to the immersion heater faster that the SI can change frequency. I.e. if the SI changes frequency first, then the SB backs off and the Solamiser thinks there is not enough power available to dump.

4)   The Solarmiser does not know about SOC of the batteries, I use the SI multifunction relay and a cascaded delay timer relay to turn on the Solamiser. After much experimentation the delay timer is now only set to 30mins. But I quite often turn the dump off towards the end of the day to allow the batteries to complete an absorption charge.

5)   If the SI goes into FLOAT charge, it will not work as there is not enough current flowing into the batteries to fool the Solamiser to think its exporting enough to dump power to the water heater. Therefore you need to set a very long boost charge, or manually turn on a manual EQ charge if the SI is already in FLOAT charge.

6)   You need to limit the output of the SB to the immersion power + other normal loads (in my case 3.3kW)  because if I leave it at 4kW, then even if the water heater is on, the SI will continue to overcharge the batteries and reach FLOAT charge (as in 5 above).

7)   I only use the Solamiser between mid Feb and end of Oct as not enough power to dump in the winter months.


I know I might be compromising my batteries slightly by starving them of full charges but the Solamiser has more than doubled the yield and therefore increased my FIT income alone on this system from £300 to £700 annually which is more enough to fund battery replacements. Plus almost unlimited hot water between March and Sept.
« Last Edit: April 23, 2016, 03:25:27 PM by nowty » Logged

11kW+ of PV installed and 56+ MWh generated.
Lithium battery storage of 50+ kWh.
Hot water storage of 15+ kWh.
Heat storage of 15+ kWh.
6kW Ground source heatpump.
EV BMW i3 (another 30+ kWh's of storage).
260,000+ litres of water harvested from underground river.
Home grown Fruit and Veg.
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