Divert excess PV energy to "heat" hot water cylinder

I have been testing a number of these units. They each have various ways of turning on a dimmer switch on your immersion. I haven't tested this particular unit, but I think it uses phase angle. This causes distortion on the grid. That may or may not pose a problem for your neighbours. The devices generally work well, but might cause your inverter to become more noisy.

rolion wrote: »

Thanks,good and valid point.

According to thier FAQ...
"The Solar iBoost+ uses a special switching method to switch power into the immersion heater, this technology does not cause flicker on electrical circuits."

Which device do you recommend, please !?

Last week I would have recommended Immersun, but they just went bust. That's why I'm testing other models....

rolion wrote: »

Seen that too ... with regrets, any idea the reason behind it ?

I guess the problem was that their high frequency switching made the unit a lot more expensive...

rolion wrote: »

Ive searched online ideas on how to do it properly but nothing good.
I dont think the 3Kw immersion element in the hot water cylinder could create an efficient solution that will cover my PVs production,nonFIT payment and the house comfort zone.

I'm inclined to go with a Aquarea HeatPump that will be "powered" day time by the PVs and keeping hot water at a constant temerature in a dedicated stainless steel cylinder,dedicated for heating and ufh.

Problem with using solar of any sort for space heating is that it works best when you need it least. Solar is great for summertime hot water when the oil boiler or whatever is on holidays, but you will struggle to run a heat pump on solar in the winter, and it would be cheaper instead to run it at night on off-peak power. Maybe a boost at noon on the PV, but not the whole day.

Sir Liamalot wrote: »

Find anything interesting yet?

Yes - found one model that just switches the immersion on and off every few seconds. Seems the meter rounds up or down to watt hours, so this works with the meter. However, it causes flicker in tungsten filament light bulbs. Why you would have those on at the same time as a solar panel is a question, but it doesn't happen with LEDs.

Also, there is a product coming to market in 3 months time which will function much the same way as Immersun, or so I am told.

rolion wrote: »

Taking in consideration that no FIT payment, I suggest to connect the output of the inverter directly to the cylinder'immersion.
In that way,direct unconditional supply of electricity towards hot water,for heating and/or for washing.
....

Not sure whats happening when FIT in,but Q is when !??

Re FIT, Minister yesterday said 2017. Didn't say which end of it. Anyone here in his constituency? (Roscommon).

You can't do what you suggest and just connect the inverter to the immersion. It need a grid and proportional control of some sort.

Sir Liamalot wrote: »

I thought the Immersun was/is PWM?

I'm looking at a prioritising islanding system so I'm disinclined to hard switch anything and I'd rather avoid spikes and dips.

Yes - Immersun was/is PWM. I meant any device that uses phase angle and a triac. Immersun is more sophisticated than that

rolion wrote: »

Hi,
I think im going to take my chances with the iBooster once i get the panels fitted.
They specified on their web site that is not creating flickering(s).

Phase angle doesn't cause flickering lights, but does distort the grid. A few comparisons with their bankrupt competitors HERE.


Scope of our grid when operating 2kw load on phase angle at half throttle see attached.

mr chips wrote: »

Could something like this also be used to divert power to storage heaters as well as the immersion? Just thinking that the array could be put to better use than heating more water than we need each day.

Yes, you can heat any load. Some of these devices have two relays, so when the cylinder is full of hot water and its thermostat cuts out, the device sends electricity to a storage heater.

However, on months when you have meaningful amounts of surplus electricity, it will tend to have been sunny and heating may not be required. I always caution against using solar anything for space heating.

mr chips wrote: »

Thanks for the quick reply. We have a boiler here and a traditional plumbed central heating system with radiators, but with a 4kW solar array in place already I'm wondering whether the addition of a few second-hand storage heaters would be worth doing, not as a replacement for the existing system but as an addition. I'd happily divert power into three or four storage heaters if it helped to meaningfully reduce our net use of oil - as time goes by, the power we'll need for lighting even in winter will gradually diminish as bulbs are replaced with LED/energy-saver equivalents etc.

On a related topic, recently I've seen a number of micro wind turbines online with a claimed output of e.g. 400W. Some of these seem ludicrously cheap, with prices in the few hundreds or even less (this is no doubt reflected in the quality of product), but I'm intrigued by the notion that it might be possible to enhance the output of the solar array, especially in wintertime, without having to spend thousands more on kit. Is that essentially a pipe dream, or are there reliable versions such turbines out there?

The heat you would get in the winter is really insignificant. See attached simulation of the output for a 14 panel system. The energy from Oct to March wouldn't really do a lot for more than one storage heater.

Micro wind was once cheaper than solar PV, but that has changed as PV fell in price. A 400W turbine isn't going to produce much - particularly in a built up area. Even trees 100m away have a drastic effect on a small wind turbine. In the USA, they mount small turbines on towers 30m high but that'll cost yer.

Having had some feedback from the installer, he thinks that small-scale wind-turbines like the sort I'm thinking of haven't yet reached the level of reliability that would justify the risk/outlay.

In terms of using power from the panels to contribute to heating the house, he said that infra-red panel heaters may be a viable option as they draw a lot less power. Simplistically speaking, they work by raising the temperature of the solid objects in the house rather than heating the air, so are more akin to sunlight (if I understand correctly). The type of unit I'm talking about can be seen at http://www.infraredpanelheaters.com/shop/categories/Standard-Panels/ or at https://www.herschel-infrared.com/product/inspire-white/

Anybody used this sort of thing before - is it effective?

Thanks for that. Several times a week I spend part of the day at home, so it might actually be worth having one in the room I mainly use. That would at least mean I wouldn't have to heat a whole floor of the house just to be comfortable, assuming it's effective! Going by the links above, I'd probably need one of the 850 watt versions.

As mentioned, my solar array is 4kW and getting the best out of the panels has simply meant changing when to run the washing machine, immersion etc so as to get it all done earlier in the day. In fact, using the immersion to heat water for later use has meant we burn significantly less oil, which is great. But despite all that, during daylight hours there's nearly always a surplus of power, even on the days when I'm at home for the afternoon and am using the PC, kettle etc (obviously, with light & TV etc being used in the evening, we still import power from the grid when it's dark).

While the array is very effective at providing hot water, there's no point in devoting all the surplus energy primarily to that, even through the winter months - ultimately we would end up with much more hot water than we need, as there's just the two of us in the household. Rather than export surplus energy to the grid, I want to figure out the best way of using the power in a way that's useful to us, rather than e.g. heating a lot of water just for the sake of it. This is why I was wondering about the possibility of storage heaters, infrared heaters etc, as it'd be nice to further reduce the amount of oil we go through, especially when the solar power is "free".

I'll have a think about other possibilities for over the winter, such as how to dry laundry when hanging clothes outdoors isn't an option - it'd probably be more efficient to put wet clothes in a small room with a dehumidifier, rather than running a load through the tumble dryer.

rolion wrote: »

Lads,i need your avice please : if i have solar tubes on the roof that does a great job ..do i still need / justify these diverters !?
I mean,doing the maths,a proper diverter cost me around €400 by the time is fitted...how much im i going to gain OR lose with/without it ?
Thanks.

I think if you have tubes, you can't justify that diverter. I'd just time the washing machine etc., and try to maximise daytime use.

Sorry, I probably won't be much help to you here - I've put the wind turbine idea on hold for the time being, as the consensus opinion I've had from a couple of different sources is that microturbine technology hasn't become reliable enough for the sort of scale I'm looking at. If you want to look into it more closely yourself then on the face of it, one of the better value ones I had come across was the one I linked to in post #23 above -

https://www.amazon.co.uk/Tumo-Int-Blades-Turbine-Generator-Controller/dp/B01JFU7IQO/ref=lp_10648601031_1_1?srs=10648601031&ie=UTF8&qid=1473863641&sr=8-1

... which claims to produce up to 2kW of power and is priced at under 1500. But I hadn't delved any deeper into that one in terms of checking out the supplier etc, so I'm not in a position to make any recommendations about it - for all I know, it could be an expensive ornament.

The key advantage of solar over wind is that it's solid-state, i.e. no moving parts, which means the potential for wear & tear is virtually nil and you won't face much in the way of costs & hassle over the lifetime of the array - in 20 years' time, mine is expected to still be operating at 80% efficiency at a minimum. As one person I spoke to said, "Wind is great when the power output you're looking at is measured in megawatts, but the reliability for small-scale projects just isn't there yet."