Looks interesting, thanks for the pointer. we looked at the emma system and with the help from some of the guys on here quickly worked out a better return on investment for us was to insulate our wax tanks to a better level. But it would be interesting to hear what people think of this.

There suddenly seems to be a profusion of devices like this. Here is a list of what I know about (prices are inclusive of VAT and may not be the lowest available, particularly in the future!).

Devices that turn on a fixed load:

1. Intelligent Solar Immersion Heater Switch Mark II, http://solarimmersionheaterswitch.co.uk £229

2. SolarDivert, http://www.solardivert.co.uk/index.html £369

3. Immersion Heater Relay, http://www.rudgerenewables.co.uk/intelligent-power-management/our-immersion-heater-relay-unit £160

4. Variety of home-brew devices, e.g.:
i) Arduino-based at http://openenergymonitor.org/emon/node/217
ii) http://www.navitron.org.uk/forum/index.php/topic,16274.0.html (link from first post of jamesingram below)
iii) Another approach described in the body of the first post of jamesingram below

Devices that vary current according to excess available:

A. EMMA, http://www.coolpowerproducts.com/uk/emma.html >£1000?

B. ImmerSUN, http://www.immersun.co.uk £444

C. S&G Wooldridge Solar PV Controller, http://www.sgwooldridge.co.uk/cms/solarpvswitch £474

D. Sunny Home Manager, http://www.sma-uk.com/en_UK/products/monitoring-systems/sunny-home-manager.html - appears to be a German product allegedly launching in the UK in 2012 but haven't seen a price. And maybe this should go into the first class - haven't looked in detail at the technical capability.

E. [Allegedly forthcoming in late 2012] Add-on to Energeno's Wattson energy monitor, http://blog.diykyoto.com/2012/04/upcoming-products.html

If anyone knows of others, post below and I'll try to edit this post to add them to the list!

Apparently Chris Rudge is going to review some products "in due course", according to the editor's comment at http://www.yougen.co.uk/blog-entry/1955/Can+I+connect+solar+PV+to+my+storage+heaters'3F/

My only interest in all of this is that I'm planning to install a product next year to make use of my excess solar PV. In my view, the second class of products above - i.e. the ones that vary current to make use of all of the available excess (but no more) - is greatly preferable if available at a reasonable cost. My strong inclination at the moment is therefore towards the ImmerSUN.

I'll put a pointer to this thread on a couple of old GBF threads on this issue, to try to keep all new discussion here (those threads are at http://www.greenbuildingforum.co.uk/forum114/comments.php?DiscussionID=8653 and http://www.greenbuildingforum.co.uk/forum114/comments.php?DiscussionID=8456 ).

I'd wait a year and they will all be loads cheaper by then.

james,
I realise you didn't come up with this, nor have you tried it yourself, but I'm wondering why you need 2 photocells. Presumably if the one looking at the red LED on your meter, only switches 'on' the immersion when the red LED is on continuously, (ie. exporting) then the presence of sun is not relevant? If that works, it's a fantastic solution - worth a shot for a tenner, even if it doesn't quite work.

Yes, thanks jamesw for the detailed list of systems out there. I agree , the ones that reduce the current to make all excess power available appear superior,and more to my liking.
I guess they work like an electronic load controller on a non grid connected water turbine, putting power not currently being 'used' into 'ballast' loads (resistive only).

We've just taken delivery of our first Immersun unit. After reviewing all the options on the market, I'm convinced these are the best, with direct monitoring of the exported generation levels, and control of the power being sent to the immersion heater so that it always remains just below the spare generated power available.

There's also a timer option so that you can ensure that the tank is hot at the end of the day via the immersion heater, and / or control a secondary heat source, and each unit has the ability to control 2 immersion heater circuits one after the other.

plus it actually looks like a well built piece of kit rather than something someone's put together in their shed after a visit to maplins.

We've previously used the relay function on the SMA inverters to trigger a contactor, but this is a right pain to install as it needs a 1-2kW Immersion heater fitting, which can be a nightmare to do, plus control cables from the inverter to the consumer unit, and customers just find it confusing to use as they have to leave the immersion switch permanently on (yes, people do seem to have a problem with this idea).

fwiw, we're offering them locally fully installed for £499 inc vat, or less if installed at the same time as a PV system, or other measure such as a voltage optimsation unit.

I do have some issues with the concept of this technology when replacing water heated by a condensing gas boiler, but the first unit at least is going in to a place that already uses the immersion heater only, and tbh we've been having so many problems making conventional solar water heating work financially without the RHI in place that I've come around to this as being a more practical and cost effective solution to that issue for a lot of people.

if we're doing links, I'll put mine up for anyone wanting more info about the unit. I won't be offended if it gets removed though.

http://www.leeds-solar.co.uk/energy-saving/immersun

Does your inverter have a relay in it that can be used for this, some do.

I finally went with a Sola Controla which as discussed above diverts excess microgenerated power, however much or little there is. Can be directed into any resistive load ( immersion, storage heater etc). They do a 3 and 6kw version which seems to work well here with wind turbine and pv's.

One which claims to use all the excess power and is quite a bit cheaper than most (~£230). No connection with company etc.

solarimmersion.co.uk - sounds similar to a few others, and looks identical to the solarimmersionheaterswitch product, but it reads as though they have sorted out the flicker problems reported on some of the other switching systems

Posted By: ImmersionAlso add the Intelligent Immersion model I2 www.intelligent-immersion.co.uk to the list. At £199 it is the cheapest available that offers full proportional control. It is a quality built unit and not a cheap and unreliable PCB in a flimsy box like some. Also no flicker.

A blatant commercial plug.

Unlike some other forums, which I am probably not allowed to mention here, there is nothing said about recommending products in the sign up T&Cs for this site. A forum that can not mention/recommend/warn of products is not very useful to the many who trawl these forums looking for such info. I was recommended to this site by someone who thought it may be a more enlightened place to be a member.

Posted By: ImmersionA forum that can not mention/recommend/warn of products is not very useful to the many who trawl these forums looking for such info.

Many products receive such comments here on GBF, but a mention/recommend/warn from an established forum poster reporting on user experience of a product is a very different thing to someone joining the forum and using their initial posts to highlight their own product.

Like Ed Davies, I think you may well have a product worth considering, but if anything your promotion methods are currently more likely to put me off than attract me, sad to say.

Posted By: bxman
Jamesw acted in good faith who has the right to stop him I would like to know.

???
I can't see that anyone has shown any objection to Jamesw's list (posted nearly a year ago). Indeed there's at least one "Thanks".

Forum members that post adverts disguised as a discussion will be banned from the forum.

My emphasis.

If Mr Chase had declared his interest/connection more explicitly than just his choice of user name then I don't think anybody would have cared¹. His² subsequent removal of his name from his profile just dug the hole a bit deeper.

¹ Actually, quite the contrary - it would have been an indication of relevant experience.
² I'm assuming he edited his profile himself. If not then apologies.

Very sorry, your T&Cs at sign up should be clearer on this. I wanted to add a story that now won’t make as much sense after removing from it all model and company names to try to keep within your rules.

A PV installer we know bought a couple of other units as they had forgotten to order new stocks of our model from the supplier in time. Both these units had to be removed within weeks, which cost them around £500 each in materials and labour, i.e. most/all of the profit on the whole PV installation job. One unit had failed despite the manufacturer’s 10 year warrantee and the other was not liked by the customer, who demanded a different unit, as he had originally been promised one of ours. After installing our model all was well.

I would mention the model name that was rejected as a warning to others, but you probably will not allow this. Suffice it to say that is quite a well known unit despite not being mentioned above. Unlike many others it does not contain a load fuse, so most shorts/failures of the immersion will blow a vital component in the unit – bad design practice. Even with the warrantee cover the installer is still likely to end up with the bill for 2 site visits, one to remove the failed unit and one to install the replacement.

Do we not therefore need proper assessments/reviews of these units here?

For the sake of those thinking of buying a unit some of the questions you ought to be asking are:-

• Performance – how close to zero export does it get and how quickly does it react to load and generation changes? How much waste heat does it give out?
• Reliability – is it well made in adequately strong box with high MTBF and long warrantee?
• Safety – is it well made to good design practices with proper fusing and does it pass all relevant legal and EMC standards, including flicker?
• What display is provided to indicate the unit is functioning and where the various energy flows in the system are going to?
• Looks and size – will it look OK where I want to place it?
• If the sensor position and unit are not close can the sensor wire be extended?
• Does it control second loads?
• How easy to install and set up? Technical consumers like lots of things to fiddle with, PV installers do not as is slows them down and leads to call backs when controls get mis-set.
• Good installation documentation?
• What technical support is given?

And that is not bigging up us as we can’t fully tick all those things, e.g. we don’t have an LCD display, partly for reliability reason as they are not likely to last the intended life of the PV system.

One final question, how to you arrange notifications for when posts are replied to? Can’t find that tick box.