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Author Topic: An idea - background heating.  (Read 8709 times)
Andy_WSM
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« on: September 10, 2013, 12:01:19 PM »

I've got a 3.92kWh array on the roof on the older FIT rate, paying for itself nicely and supporting my otherwise rather large electrical demand.

My bungalow is heated using wall mounted electric radiators (no gas) and the hot water with a 12kW instantaneous heater (I know, I know, but at least there are no standing losses!).

So here's the plan that is hatching in my mind right now...

Collect up a few unwanted / unloved bathroom sized storage heaters (I'm thinking 3) which are each rated at 0.85kW (so 2.55kw total load) with an approx storage capacity of 6kW each. - Use a proportional controller to drop the excess power I generate and currently send to the grid (to be lost in the network somewhere) into the 3 storage heaters.

The heaters could be installed into the kitchen, the hallway and the bathroom and just left on "max input" and a low output, so they collect as much spare power as is available & slowly release heat during the afternoon & evening taking the load off the electric radiators (and the peak time metered electric consumption) and keeping the chill off the house. I know they would only really be effective Oct, Nov, Feb & March from previous experience, but there are plenty of cold & sunny days that I could collect about 10kW of power to use as heat in the evening when I need it...

In these 3 strategic locations they would also act as frost prevention meaning when I go on my Winter holidays I can leave the electric radiators off rather than on low.

Thoughts?

Have I overlooked something? It seems too easy / inexpensive to implement?!
« Last Edit: September 10, 2013, 12:03:42 PM by Andy_WSM » Logged

North Somerset. 3.92KWp SE facing PV system.

djh
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« Reply #1 on: September 10, 2013, 12:22:48 PM »

Do you know how much energy your panels generate in those months? Perhaps you have recorded your generation, or you could estimate it on the PVGIS site or elsewhere. If you start from those numbers and compare them to how much electricity you normally use to heat your bungalow in those months, you can see how much help the storage radiators would be.

I suspect that the answer will be that it's not worth the effort, and I'd suggest that you might want to think about improving your insulation first.
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Cheers, Dave
Andy_WSM
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« Reply #2 on: September 10, 2013, 12:33:24 PM »

Thanks for the input.

I don't think it would cost more than not very much to set up. I can make a proportional control circuit, I probably won't need to spend more then 30-40 on bits to do this. If I can get hold of some second hand storage heaters these would be inexpensive also.

I have the archive data for my generation since June 2011 when the system went live.

October 2012 was very variable, the lowest being just 2kW in a day, the highest about 17.
November 2012, lowest about 1kW (think it was snowing!) and highest 12kW.

December not worth mentioning because although I generated just over 8kW some days, very little of this would have escaped to the grid.
The way I figure is that every kW I can prevent being exported is a kW less I have to pay for peak rate electricity in the evenings...
Even releasing the heat into the bungalow through the night must reduce the heat load the next morning?

I've already had the walls insulated & stuffed the loft to the hilt with rock wool. I also insulated under the floors as I've decorated each room.

I don't use HUGE amounts of energy for heating as I have the advantage that electric heating is easily zoned, but anything less is a bonus surely?
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M
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« Reply #3 on: September 10, 2013, 12:33:55 PM »

Hiya Andy - this isn't a million miles away from an idea I asked about on here a few months ago. To install a split system A/C unit, then use it as an ASHP in the 'shoulder' months, when air temp isn't too low, but some additional heating is needed (Mch/Apr & Sept/Oct) and spare PV gen is available. This way you'd get a COP multiplier on top of your electric heating.

I haven't progressed this any further (yet) but with GCH it probably isn't worth it for me. But for you with electric heating, if the kit is around 500 + install, possibly 1kW in and 3+kWs out, then might be worth considering.

More theory than anything else at this stage and not sure if you could use proportional diversion, probably weather forecast and MarkI eyeball, but if you do end up using a mix of PV and import, at least the COP should offset the import.

Mart.
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Just call me Mart.     Cardiff: 5.58kWp PV - (3.58kWp SE3500 + 2kWp SE2200 WNW)
Andy_WSM
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« Reply #4 on: September 10, 2013, 02:11:25 PM »

That's an interesting idea, but would need a lot of manual control. I can't think of any way of automating the use of a heat pump (that the heat pump would withstand for long, i.e. can't do lots of stop-start cycles) - and of course proportional control is out.
« Last Edit: September 10, 2013, 02:18:03 PM by Andy_WSM » Logged

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Tiff
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« Reply #5 on: September 10, 2013, 03:27:56 PM »

Andy, I get the impression you have the ability to make things yourself, so how about converting a second hand air condition/dehumidifier to a homemade heat pump. Would probably draw anywhere between 300w and 1kW and could be left running all the time on sunny days, I'm sure that a COP of least 2 must be possible, maybe more. You would at times be importing, but I'm sure the gain would outweigh the loss.
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RIT
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« Reply #6 on: September 10, 2013, 09:39:41 PM »

Hiya Andy - this isn't a million miles away from an idea I asked about on here a few months ago. To install a split system A/C unit, then use it as an ASHP in the 'shoulder' months, when air temp isn't too low, but some additional heating is needed (Mch/Apr & Sept/Oct) and spare PV gen is available. This way you'd get a COP multiplier on top of your electric heating.

I haven't progressed this any further (yet) but with GCH it probably isn't worth it for me. But for you with electric heating, if the kit is around 500 + install, possibly 1kW in and 3+kWs out, then might be worth considering.

More theory than anything else at this stage and not sure if you could use proportional diversion, probably weather forecast and MarkI eyeball, but if you do end up using a mix of PV and import, at least the COP should offset the import.

Mart.

I have the same idea/plan on the todo list, the key things I have noted about doing this.

- Selecting an A/C unit that is described as an Inverter Heat Pump as this will draw a variable current based on its load.

- Even if you end up using a high % of import power as long as the COP is above your electricity cost / your gas cost you are doing OK.

- A heat pump is very effective if you need spot heating within a home, so is very good for a low occupancy home where you just want one key room heated as a gas boiler can be very bad at doing this.

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car-mark
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« Reply #7 on: September 11, 2013, 12:24:42 AM »

Hi there

I agree with most of the above. We have storage heaters on our semi modern bungalow. No gas, oil do not like. The first year of moving in we froze as the heat output was not enough.
The house had reasonable insulation cavity wall, 50mm ep for the floor and about 100mm rock-wool in the loft. The following summer the energy companies were giving away loft insulation so am upgrading to 300mm as we decorate and upgrade each room.

Our heating improvements were varied, add wood burning stove to the lounge made that room habitable in the winter. combine reversible heat pumps (make them inverter as mentioned above) Note cheaper inverters are not as good as good names. This allows heating with a storage heater and thermostatic control with the air con units.

Mart the problem with air con units in the swing months is frosting up. the air is "wetter" and you spend more time deicing than in the depths of winter when the air can be "dry"

Have started the experiment that was mentioned in the OP. I have installed a 1.2kw storage heater of proportional control in the mode of calypso ray, will probably need to turn it on in the next week will keep posted on if it works.

mark
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Andy_WSM
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« Reply #8 on: September 11, 2013, 03:02:55 PM »



Have started the experiment that was mentioned in the OP. I have installed a 1.2kw storage heater of proportional control in the mode of calypso ray, will probably need to turn it on in the next week will keep posted on if it works.


This is the route I am going to go.

I managed to get hold of a second hand 0.85kw Storage heater that will be dropped off tomorrow. It's the perfect size to pop into the bathroom and should stop the 750W oil filled radiator in that room coming on very often, if at all. So although the saving won't be huge, it's a saving, for little outlay.

If it works well I shall put a second one in the living room. I have room for a 1.5kW storage heater to go in there without being in the way. Whilst it won't be enough to stop the need for a radiator entirely, it will certainly help keep the temperature comfortable and may even stop the need for the radiator to be on some evenings.
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Andy_WSM
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« Reply #9 on: September 12, 2013, 03:47:33 PM »

So, today I fitted a "SolaMiser" (cost 130, much less time consuming for me, seemed like a good deal, easy to fit "package".) and a second hand small storage heater in the bathroom. I connected it all up around 12:30pm, so missed the morning Sun, but have diverted 5kW into the storage heater this afternoon whilst only producing 10kW all day with mostly an overcast (typically Autumnal) day. I can see this has enough potential to justify a small outlay, but I wouldn't want to many spend hundreds of s doing it. I'll see how this performs for a few days, then go on the scavenge for a small storage heater for the hallway and probably stop at that.
« Last Edit: September 21, 2013, 07:14:59 AM by Andy_WSM » Logged

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SABGLA
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« Reply #10 on: September 14, 2013, 04:54:44 PM »

I would really like to hear how you get on. I have a combi boiler and so no water tank, therefore i cant use any of the nice immersion devices people always talk about. This would potentially be a great way for me to store some of the energy generated during the day and save some gas.

SAB
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Andy_WSM
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« Reply #11 on: September 14, 2013, 05:06:15 PM »

Well, it's on day 3 and appears to be working well.

Yesterday the storage heater only took 3kW of charge as it was a very autumnal day (wet!) and the system only generated 8kW all day. However, this morning was a chilly 8C outside and the residual heat from the storage heater kept the bathroom at a comfortable 20C. The living room was a less pleasant 15C.

Today has been a day of patchy sunshine and the storage heater has taken nearly 3/4 of a full charge of 4.1kW, so expecting the bathroom to remain warm through the night. Generated 13kW today and haven't been here to use it (although did leave the dishwasher timed to run at mid-day) so I think I could easily have diverted the same sort of power into a second storage heater - which is still on the "to do" list.

The way I see it is that 4kW of "free heat" is not to be sniffed at, potentially reducing the heat load of the house by the same figure will add up to a substantial saving over the Winter months.

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Andy_WSM
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« Reply #12 on: September 15, 2013, 03:51:46 PM »

Day 4. A perfect example of why this should be background heat only...

Storage heater was still pumping out heat when I woke the morning. Bathroom lovely & warm.

It's never really got light here today though, thick cloud and rain for most of the day has left my PV production at just under 3kW! With no surplus to go into the storage heater.

P.V. System has peak at a few hundred watts today and has been outputting just 50W all afternoon. Crazy!
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SABGLA
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« Reply #13 on: September 16, 2013, 03:01:28 PM »

Sounds good. I am getting more interested in giving it a go.

What Solamiser did you get? there seem to be three options:

Standard - Heat hot water with up to 7kWh then optional load for the rest of the day
Early       - Heat hot water with up to 5kWh then optional load for the rest of the day
None       - Heat hot water all day

how much energy can you put into a storage heater? Can you overload the heater if you have a particularly sunny day? or maybe the solamiser handles that.

Did you just wire the output of the solamiser to the heater (never used one so not sure how they connect up)?

SAB
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Andy_WSM
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« Reply #14 on: September 16, 2013, 03:06:10 PM »

The last option - so I can divert any & all excess power. The storage heater has a "charge control" which I have left on Maximum i.e. I want it to collect as much heat as possible. It will simply switch off when it is at maximum temperature.

Today has been one of those cold & Sunny days -perfect for this experiment.

I've been able to keep a 2kW oil filled radiator ticking over on the thermostat in the living room keeping it at 21C and the times when it isn't drawing current the Solarmiser has diverted the surplus to the storage heater, with some energy going back into the grid.

I'll update with figures later, but think it will be another 4kW or so into the storage heater with everything else keeping the house warm today Smiley
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