PV immersion heater proportional control

[echase]

I have no reason to doubt that he has the years worth of data that he says he has, though I do think the savings figures he's supplying look quite high, and probably relate to relatively high hot water consumption levels eg family houses rather than single or 2 people households.

The first prototype Intelligent Immersion was installed in mid 2011 and was followed shortly by many other prototypes. Some were connected to monitoring systems from late 2011 logging them every 5 minutes. The first production versions were in early 2012 but not in the II name. They are now available under the new company structure so technically you are correct that some of the analysis comes from units not marketed by Intelligent Immersion Ltd but, especially since late 2011, it is essentially the same software and hardware. It’s been improved but, as the method of operation is the same, data from over a year ago is still valid.

If you think I am optimistic then some others are quoting much more than I do. I did the analysis partly because I was concerned about these optimistic predictions and wanted to see where the truth might lie. You are right that a 1-2 person household may get less benefit but not say if they use baths whereas the larger household uses short showers. It is not possible to give a better result without collecting statistics for a large range of houses. Not seen anyone else who has been willing to publish any statistics. It isn’t that easy to do because unless you have a whole year of statistics you have not measured the full annual solar cycle. Our full data set exceeds 1million datapoints.

Navitron don’t like mention of any product that they don’t sell/promote themselves.

 

[Gavin A]

well, I know that our 80 tube solar water heating system (east facing, small 47mm tubes) produces around 1000kWh a year of usable energy, as we've been monitoring it for 3 years, and that's in a house with 4 people.

It equates to around daily showers for 3 people, so I think that 1400kWh is going to be pretty top end.

tbh I suspect that your tanks are probably leaking heat quite badly. The tank we're monitoring loses around 1.5-2kWh a day in heat, and it's got 50mm of insulation - if you're heating older tanks with 25mm jackets then this heat loss is likely to be more like 3-4kWh a day if they're being heated during the day, with most of the use actually being the next morning.

So while I can see that the figures could be right for the actual power going into the immersion, I'd suspect that it's not actually replacing that level of heat input unless the house previously had the tank being heated all day long or something. I certainly doubt that this level of savings could be made in any house with less than 3 people living in it.

ps I've also had similar discussions with another supplier who was making much less possible predictions.

 

[echase]

Gavin

In pre solar days the main loss I would have thought is in short cycling your boiler if you leave it on all the time. It may say fire up for just 5-10 minutes many times a day and in between the on times >95% of the heat in the boiler and pipes is lost/not useful in summer. Most people though may top their tank up twice a day which keeps their water quite hot all day so I can’t see the overall heat loss per day changing a lot, depending on whether it’s heated all day or with one or two top ups. Newton’s Law of Cooling. Have no hard data on this though.

The limitation on a PV water heating system is not usually production of spare export but the ability to absorb it into the tank.

Two of our systems had 2 loose blankets added on top of the normal foam insulation and the temperature in the airing cupboard went down dramatically. On one of these it makes a top up at 7pm if the sun that day is inadequate and has hardly lost any temperature by next morning. This PV controller only inputs about 750kWh to tank as it has a small solar thermal system as well, limiting the amount the immersion can do, and the couple are quite abstemious with water. But as the summertime heating is full price electricity and wintertime is gas, 750kWh represents nearly £100 pa saved so payback is around 2 years. As it’s been in service for 2 summers and actually cost less than £200 for a prototype it has probably recovered all its cost already. The solar thermal system was hardly going to recover its cost in >10 years and will get removed as it has got reliability problems.

Our data is mostly for London and Hampshire. Afraid we don't have any monitoring on systems much further north. Clearly you have less sun in Leeds but there are UK places with more like south west of England. I am not sure where in UK is considered to be average. Solar thermal is quite popular in Scotland I hear.

That could be said to be regional bias but remember that there is more population and probably more PV in the southern half so any averaging of results would be biased towards the south. We use to quote lower figures for energy into immersion until the real measurements came in and it became apparent that most PV systems, at least in the southern half of UK, are well exceeding their MCS predicted figures, e.g. Hampshire is around 50% higher and every 10% extra is more than 10% extra available to the immersion as the house load does not increase.

Whether the payback is 1 or 4 years could be said to be not that important, the important point is that it is much better than almost any other product in the energy saving market, barring draught proofing strip, and so earns more money than leaving it in the building society.

The Immersun tells you the amount of energy saved today. Does it not accumulate this value over a year to tell the annual saving and so are there any figures for this available? Rumored to be a pseudo measurement based on counting the on cycles of the burst firing, rather than a real current measurement into immersion, but this should be quite accurate.

 

[lydart]

I see that the SolarImmersion introductory price has now ended.

Gone up by £50 to £249.

 

[echase]

The Intelligent Immersion costs less than that and there is stock available now for immediate shipment.

 

[lydart]

My Solarimmersion switch (Mk 3) has just been delivered.

 

[Gavin A]

you're asking that question on the public forum.

 

[MicraShed]

^^ It isnt hugely difficult to find the retail price of the Immersun out on t'internet.

I cant say I begrudge paying what I did to have it supplied & installed because its not just a case of paying for the device, the VAT and some chap to drive round to the house and fiddle about losing an hour or so of his life installing it and setting it up.
Its all the associated stuff that goes with that - knowing if i have a problem I have a port of call to discuss it and likely some support.

Its been bitterly cold today here in Granada-land and yet in between flurries of snow its been heating the water up a treat.
Happy?
Oh yes.

 

[Gavin A]

^^ It isnt hugely difficult to find the retail price of the Immersun out on t'internet.

he's asking about the trade price though.

You're being reasonable about it, but some customers seem to not understand the concept of a business needing to pay staff wages and running costs on top of the actual cost of the equipment, never mind the time spent researching the equipment, training staff etc.

 

[infinity]

post removed, sorry was not thinking...

 

[mixit]

I have recently commissioned a 5kw wind turbine.
I requested a device to reduce export of power and they offered and fitted the immersun.
The switch has most of the bells and whistles I wanted but unfortunately my lights flickered to such an extent, when the surplus was being fed into the immersion, that I complained.
The turbine company researched the switch more carefully and decided the device was not really legal as it had no approval, so they want to remove it. This, they say, applies to all burst fire switches.
I checked out as many switches as pos and believe the Solar immersion does not use this system.
It has more or less the same options as the Immersun so I will opt for this if the turbine company agrees with me. Electronics are a bit mind blowing.

I believe it is essential to have at least 2 circuits to switch to, however what I would really like is a device which can remotely, via the ring main, switch on a selection of loads with sensing switches using various frequencies.
This would allow loads drawing from a ring main to take power when it is available or in rotation.

Regarding the immersion heater, If I cant find the remote switching I propose to EXTRACT heat from the tank when it is fully hot by running a selection of radiators through the indirect coil. This will cool the bottom area and the power will be redirected to the tank to replenish it. The pump would run when the relay diverts to the second service.
If anybody sees a flaw in this please advise.
MOST especially, if there is an electronics wizard out there will he direct me to a remote switching product.
Perhaps the switch manufacturers who read and contribute to this discussion could consider adding this to their product.

 

[echase]

I believe it is essential to have at least 2 circuits to switch to, however what I would really like is a device which can remotely, via the ring main, switch on a selection of loads with sensing switches using various frequencies.
This would allow loads drawing from a ring main to take power when it is available or in rotation.

Regarding the immersion heater, If I cant find the remote switching I propose to EXTRACT heat from the tank when it is fully hot by running a selection of radiators through the indirect coil. This will cool the bottom area and the power will be redirected to the tank to replenish it. The pump would run when the relay diverts to the second service.
If anybody sees a flaw in this please advise.
MOST especially, if there is an electronics wizard out there will he direct me to a remote switching product.
Perhaps the switch manufacturers who read and contribute to this discussion could consider adding this to their product.

The Intelligent Immersion model i2 will do your basic function without flicker but we can’t do the extras that you ask for with the standard product. Certainly can look at it but I suspect that it would add so much to the price of any product that it would not be cost effective in terms of payback. It’s the law of diminishing returns in that the basic function of one immersion is very cost effective but every extra load that you set up to be fed is less and less beneficial in terms of the cost of providing the function versus the electricity saved/used.

It strikes me that 2 output controllers have some design compromises in terms of the way the second load is triggered, like time delays before it is switched in and back again. You have to make some big assumptions when setting the timings. This results in significant time periods when the generated electricity is being exported or redirected to the wrong load. Would not a simple tank thermostat, that switches over to the second element when the top half is hot, do the function better?

I have taken some flack on forums for pointing out the flicker problem with burst fire devices so it’s good to see that some others do agree with me.

 

[Earthstore]

What about a heat escape radiator plumbed into your hot water cylinder, basically when your cylinder is up to temperature the hot water would circulate through a radiator.

Just a thought.

 

[GOL]

@mixit - there are many instances where light flickering is only the visible effects of such load switching devices available in the market. Majority of which require hard-wiring and citing in and around the consumer unit, hence why some installers will not touch these products with a barge pole.
Your turbine company is correct in their conclusion that the method of Burst Fire TRIAC is not particularly "legal" in any circumstance, due to the method in which the devices proportionally control resistive loads.

No doubt, I feel there is a gap in knowledge available to the marketplace regarding the particulars in how these products work and whether they actually comply to all of the domestic regulations outlined. Hence, I feel these forums are an excellent way for people to come together, learn and understand more about the products available and how best to go about saving energy!

Unfortunately, some of these market products have a very short-termist perspective in their lifeline. I personally believe they will eventually be looked at more closely, in a dim light by DNO regulators and energy suppliers. However, that is not to say that all devices can be painted with the same brush.

The idea to monitor and manage loads within a household is really the next step for any micro-generation system. The immersion has received a lot of attention as this is a prime candidate, being able to store that energy generated as hot water to make use throughout the day - a no brainer! However, not all households have immersion tanks..

Do not forget, this is not the only electrical appliance available in the household!!

 

[danesol]

So apart from the cost deferential, what are the advantages if any, of the Immersun unit over say the Solar immersion mk3 Switch for example ??