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There are two articles Diverting Surplus PV Power that you can read, or if you want a complete kit or even a ready-built unit, Robin Emley can supply you at www.mk2pvrouter.co.uk/

Both systems measure on a cycle by cycle basis (i.e. two orders of magnitude faster than your system) and will operate completely independently and need neither user input nor supervision. However, you can still override the system should you need to use the immersion heater when no surplus PV is available and the store of hot water is depleted. 

If you feel a need to gather data before you embark on the energy diverter, then an emonTx and current transformer on your PV infeed will give you that information - by default every 5 or 10 seconds. You could arrange for that data to feed in to your PC, given a suitable serial interface and software.

Thanks Robert.  Here is my latest batch of pre-built units nearing completion :) 

Robin

Thanks for your advice Robert I have just had a quick look but obviously need to work out what I would need exactly  as at first glance I'm still confused lol

I'm very tempted with a pre-built one when I work out what it will cost !

I'm thinking I might be able to use my present setup to switch the power to a room heater or something when the hot water is up to temperature by routing it via a relay controlled by my PC.

The only problem with that is that when I get most power I don't need the heat eg summer.

some days in the summer I must be exporting over 30kwh easily and my hot water only uses between 4kwh-7kwh per day.

I just cant think what else to use it for?

anyway thanks again

Mike

I fully understand the confusion. Just keep on asking.

Either of the diverters will automatically balance whatever surplus power remains, therefore if your present system decided that the water might be hot enough, then you could switch a heater on and the immersion would automatically throttle back to suit. Of course, if you go for Robin's multi-load solution, the diverter knows when the tank thermostat has opened (or rather, it knows that it is unable to dump energy into the primary load) and it starts dumping into the next one. You can have the loads controlled by radio if you wish.

If you're happy messing about with mains power and sourcing components, you might save some money by building from scratch. Personally, I'd go for Robin's kit, as it's now a well-proven design. (And I'm not saying that just because I crawled all over the design throughout the development, chucking spanners in wherever I could...)

We're well aware of the problem of usefully employing the surplus energy, unfortunately, there isn't a viable solution. The best idea I could come up with was a very well-insulated swimming pool and a heat pump. I once heard someone suggest you feed into a diesel generator, and wait for the oil to start brimming over the top of the tank. He was joking. If only that were possible.

Mike,

I can also endorse Robin's system as I was one of the early adopters. It has worked well for me for 9 months now and Robin continues to provide support when asked - you will not go wrong here. It also sounds as if you have the technical ability to understand it too.

We all face the problem of what to do with the surplus when the water is hot. I have built a system to DESTRATIFY the water in my tank (mix it up) so that I can then add more energy into the tank to get more hot water. I will be posting the design to this Forum soon when I have done a few more tests.

When that is done I intend to switch on a battery charger to charge a deep cycle 12V battery for background LED lighting and then pump water in my garden for a gravity fed plant irrigation system.

Peter 

I too have been running a home made version using Robins code for well over a year now and it has been absolutely flawless, though I keep developing it further. I now have 10 SSRs running on it. I also have set up time delays ( both on and off) for some of the loads and have different sequences for turning loads on and off.

Robin's design is not only rock solid, but adaptable too. It runs fine on my split-phase 60 Hz system. (I'm in the US)

Nice looking set of pre-builts there Robin. Looks like business is good!

Robert Thank you  for your comments and advice It looks as if setting up more than one load is going to be trivial !

Peter It' will be interesting to see how you are destratifying the tank? and I'd love to know what you are controlling with your 10 SSD's Tinbum !

I just had a thought that I could have a heater  turn on in the winter and a Aircon in the summer. although to be honest I don't need aircon lol

I have thought about a GSHP. That would soak up all the surplus and then some! and in the summer heat the water and send it back to the soil as a heat bank.  I can't imagine that would work though lol.

Getting back to the MK 2 PV does it have any way to send data back to my PC ?  I love to generate graphs ;)

loads controlled by radio! is that included in the Kit ? I did see something about RF but wasn't sure what it meant.

Is there a User Guide that explains exactly what you can achieve with the full kit? would save me badgering you :)

I had a look at the downloads but couldn't see one.

thanks again

Mike

Have you found Robin's Mk2 Code variants and associated tools? It will take you some time to understand this and check the posts that are linked, where you will find a detailed explanation and often the rationale for the design, but if you are unsure of what you are trying to do, I think it will be worthwhile, and should answer most of your questions.

I'm planning on running GSHP and ASHP on mine, hence the time delays and load sequence additions.

Thanks all, I will have a longer look through the code variants and then contact Robin.

I had a look at the cct and can see no data outputs so that's a pity as I will have to get off my backside to check it :)

GSHP AND ASHP ! I'm impressed lol

Hi guys, just to recap:

My original Mk2 PV Router design was intended to run on an Arduino Uno, but works just as well on an emonTx V2.  Supporting info, nominally written by yours truly but with much assistance from our Editor-In-Chief, is in the online article  Diverting surplus PV Power which is linked from the OEM Home page.

Later versions of my Mk2 code provide additional features such as anti-flicker, multiple loads, and the ability to have a dump-load controlled by RF.   An alternative version of PV Router code, which also runs on the same hardware, has been developed by Martin Roberts.  This is based around a PLL technique, a full description being available at http://openenergymonitor.org/emon/pvdiversion/pll.  Unlike my own code, Martin's sketch supports the transmission of data for data-logging purposes.

To construct a complete unit for diverting surplus power has always required additional items such as DC and AC power adaptors; also, safety aspects for 240V AC use need to be taken into account.  To address these points, I've designed my own self-contained version of the hardware.  This is now available for purchase in various forms from my website at http://www.mk2pvrouter.co.uk

My new implementation includes two current sensors.  One is to support the main operation of the router, i.e. to balance consumption with generation.  The second channel is available to provide an accurate measurement of the amount of energy that has been diverted each day.  With a minor change to the software, the second channel could equally well be used to measure and display the total amount of energy that the PV system has generated.  This might be of interest to anyone whose inverter is in an inconvenient location.

An RF facility is available on the main PCB but I've so far not used this feature in any code that's been released for the new hardware.  Existing Mk2 code can be run on the new hardware, the analog IO pins just need to be reallocated.  For ease of PCB layout, my new board uses AIO pins 3-5 for the V and I sensors rather than the lower numbered ones.   RF-enabled code will no doubt appear in due course, including the routine transmission of data for use by emonGLCD and/or emonCMS.

Since opening up my online Shop a month ago, I've built & sold six complete systems, and a similar number of kits.  This venture is a totally new challenge for me, and seems to be going well so far.  Hope I'll be able to cope as the weather improves.  Thanks for all the kind words.

Hi Robin

Indeed my inverter is in a very inconvenient position (My Loft) so data logging would be very helpful.

If I understand your post (which I'm not sure I do) you can possibly supply all or most of what I would like?

Ideally  I would like to log my import and export and the diverted power straight back to my PC either wirelessly or ethernet.

I have an extensive one wire setup and might be able to piggy back the cat 5 cable for ethernet  but it wouldn't be much trouble to lay new cat5 when I install the mains cable up to my immersion as there is a network hub in the immersion cupboard.

I have had a good look at the relevant articles but being such a newcomer to this, I am getting confused by all the acronyms and references to other boards that I've never heard of. I reckon I'll need a good day or two to try to work out what it's all about. :(

should I email you direct?

Mike

Mike,

I'm fairly confident that I could supply you with the necessary control equipment to divert surplus power to your immersion.  Also, to display the energy flow along a second AC path, either for the immersion feed or the output from your inverter. 

The routine transmission of data by RF is straightforward enough, I've just not included this in the only sketch that has been published thus far for the new hardware.   At the far end of the link, you would need one of the standard receiving devices, i.e. a nanodeRF or an RF-enabled Raspberry Pi (hope I've got that right!)

Feel free to send me a PM.

Robin

Robin I sent you an email to your shop enquires address

Mike,

I am using a 12v DC pump rated at 11Ltr/min attached to a reversed Surrey Flange at the top of the cylinder. The pump is mounted externally on the top of the Surrey flange and draws water from the bottom of the tank through a long dip tube.

It destratifies the tank with a top to bottom difference of 20C. My pal has a similar motor but he has installed his inside the tank, submerged. We are comparing results. The internal pump has the advantage that less plumbing is required but installation and access (through the immersion heater flange) is a bit of a bother and needs some tidying up. The external pump creates external pipe joints, needs a vent pipe and other bits of bother but installation maintenance and access is a breeze.

We both pump cold water from the bottom of the tank into the hot water at the top. This cold water heats up as it falls through the hot so we 'deepen' the layer of hot water from the top down. We reduce stratification but we do not eliminate it

Still, they both work. On a good day I can get 85C at the top of the tank and 65C at the bottom. Without destratification the bottom of the tank is 20C. If I hook up a more powerful 500W shower pump I can get to 5C difference but the pump is a bit brutal. The range of 12v DC low-ish flow rate pumps that can take 85C water is limited.

I use LM 35 temperature sensors araldited onto the tank and a current coil to give Irms as a proxy for PV. If the tank top gets to 85 celcius and there is enough PV I start the pump with latches up and runs till Tdiff < 20C. I drive the 12V pump from a separate supply and trigger it from a Darlington pair of transistors off the Arduino digital output. It takes about 15mins to get Tdiff to 20C in my 170 ltr tank

This system is separate to the PV Diverter. I use 2 Arduinos at the moment to prove the concept and also drive a temp display system.

The control is simple and can be improved many fold - that is why I will post it for the coders to get cracking with PID control and other niceties. However 'bang bang' control is good enough for now. 

For me at the moment though its all about the hydraulics and the plumbing, less so the control system. 

I will do a posting soon with pictures and parts so the Forum members can pick the bones out of it all

Presume I start a new topic called DESTRATIFICATION as this one is getting long now and destrat is a different subject?

Peter

There's been plenty of talk about de-stratification on this forum in past months, so it may not be necessary to start a new thread.

Mike,

I have just built Robin's Mk2 PV dump and it works a treat; if you are like me  with plenty of time on your hands it will certainly keep you occupied for hours and hours and ........ if not I would go for one of Robin's solutions, they are very reasonably priced and a lot cheaper than the commercial solutions and in my opinion are far better.

Regards

Paul

Thanks, Paul, for those kind words, much appreciated. 

Setting prices for my offerings was a tricky part of the operation.  With my product not being directly comparable with commercial solutions, it was difficult to know where it should be pitched.  In the end I just went with what felt right.