Choice of intelligent switches ?

Martyn1981

Cheers Z, glad you could see where I was going (or should that be, coming from). Once my brain had locked on to the SC savings and lower capital costs the pondering kicked in.

The only other thing I can think of is the CH pump leccy use. Mine is 95W, but I suppose you could class that as useful heat, so maybe it's not relevant, or perhaps the 'normal' leccy cost v's gas cost of that 95W is relevant, hmmm.

Doesn't really work for me, with off south, shallow panels, but perhaps a serious consideration for a large roofed Passivhaus.

Ok, running with this idea, now PVGIS'd a 50deg roof, south facing with 8kWp for my location (so good, but not brilliant). That gives an average generation of 272kWh's for Dec (Nov 359, Jan 299, Feb 416) so 8.77kWh's per day average in Dec.

Hope I'm not making this up, but I've got the figure of 8kWh's per day for heat in my head for Passivhaus, but that might be an average (or total nonsense!). Of course PV, wind etc doesn't have to cover demand, just contribute, but it's interesting.

I'd guess that to minimise import and maximise the efficiency of such a structure, a good intelligent switch would be essential.

Mart.

zeupater

Martyn1981 wrote: »

... Hope I'm not making this up, but I've got the figure of 8kWh's per day for heat in my head for Passivhaus, but that might be an average (or total nonsense!). Of course PV, wind etc doesn't have to cover demand, just contribute, but it's interesting. ...

Hi

Basically, you're well out unless the house is ~200sqm .... more like (from memory) 15kWh/sqm/yr for space heating with a total of 120kWh/sqm/yr for all energy with both criteria being met ...

We meet the total criteria easily and still have a way to go on the space heating although we cannot ever reach the required level of airtightness and insulation in a semi-conventional build property without demolishing & rebuild.... still trying though ....

HTH
Z

Martyn1981

zeupater wrote: »

Hi

Basically, you're well out unless the house is ~200sqm .... more like (from memory) 15kWh/sqm/yr for space heating with a total of 120kWh/sqm/yr for all energy with both criteria being met ...

We meet the total criteria easily and still have a way to go on the space heating although we cannot ever reach the required level of airtightness and insulation in a semi-conventional build property without demolishing & rebuild.... still trying though ....

HTH
Z

Evening. Sorry, being a bit slow today. Not trying to defend that 8kWh figure I gave, as I honestly can't remember if I made it up, but if a 10m by 10m footprint is reasonable, then:

15kWh/sqm/yr = 1,500kWh, divide that by 180 days = 8.33kWh's per day. Is that just a total coincidence, and I'm comparing apples with oranges?

Does the sqm refer to the footprint, or the total floorspace?
Is 180 days reasonable? Normally our heating goes on late September and off late Mch, but last year and this are anything but normal, so perhaps more like 7 months rather than 6 months. Then solar gain covers the rest. In fact our roof velux stays 'cracked' and vents the house the other 5 to 6 months.

Apologies for this tangent, just trying to get some numbers in my head for late night / early morning pondering.

Mart.

counting_down_the_days...

Smart meters are currently not compatible with export meters :j However, at 3p a unit, I'd rather heat my water.

Mart, sorry that got way to complicated for me, however, in response to saving on your oven cooking. I have a combination microwave, you can use it as a normal fan oven, it heats up much quicker, I'm sure it's less watts :huh: and it's big enough to feed a family - we do have a large one. I couldn't be without it.

Martyn1981

counting_down_the_days... wrote: »

Smart meters are currently not compatible with export meters :j However, at 3p a unit, I'd rather heat my water.

Mart, sorry that got way to complicated for me, however, in response to saving on your oven cooking. I have a combination microwave, you can use it as a normal fan oven, it heats up much quicker, I'm sure it's less watts :huh: and it's big enough to feed a family - we do have a large one. I couldn't be without it.

Hiya, and cheers.

Regarding cooking, this is more of a 'dumb' switch than an intelligent one, but we started using a slow cooker when we got PV.

Absolutely brilliant, and it effectively shifts some evening leccy demand into long 'gentle' daytime generation, so an environmentally friendly dinner.

Mart.

zeupater

Martyn1981 wrote: »

Evening. Sorry, being a bit slow today. Not trying to defend that 8kWh figure I gave, as I honestly can't remember if I made it up, but if a 10m by 10m footprint is reasonable, then:

15kWh/sqm/yr = 1,500kWh, divide that by 180 days = 8.33kWh's per day. Is that just a total coincidence, and I'm comparing apples with oranges?

Does the sqm refer to the footprint, or the total floorspace?
Is 180 days reasonable? Normally our heating goes on late September and off late Mch, but last year and this are anything but normal, so perhaps more like 7 months rather than 6 months. Then solar gain covers the rest. In fact our roof velux stays 'cracked' and vents the house the other 5 to 6 months.

Apologies for this tangent, just trying to get some numbers in my head for late night / early morning pondering.

Mart.

Hi

I've always understood that passivhaus is based on floor-space, not footprint (which makes sense), therefore the house would need to be 10mx5m (/7mx7m etc) if two-floors.

In a way your figures are correct based on a 180day heating season on a 100sqm property, however the majority of passivhaus builds I've actually been in tend to be designed with the aim of keeping heat in rather than maximising solar gain (ie small windows) which leads to a longer heating season .... I know that this is generalisation and solar efficient houses are being built, but it seems that passive solar and passivhaus are different animals in today's terms as whatever the quality of the glazing it still leaks considerably more heat than a well insulated solid wall ....

A good friend has had a low-mass passivhaus for a few years and has so-far had to provide a certain level of heating most months, summer included. One issue which came to light between planning the house and living in it is the improvement in thermal efficiency of electrical items (LED TV, LED lighting etc) which has created a background device heating shortfall which needs to be made-up by direct space-heating .... I'd guess that if this is the case in the majority of passivhaus builds then someone will need to address the balance between the space heating and total energy criteria and that's why the total energy figure is so high ....

Perhaps one of the architects who frequent these boards could provide comment ....

HTH
Z

Martyn1981

zeupater wrote: »

Hi

I've always understood that passivhaus is based on floor-space, not footprint (which makes sense), therefore the house would need to be 10mx5m (/7mx7m etc) if two-floors.

In a way your figures are correct based on a 180day heating season on a 100sqm property, however the majority of passivhaus builds I've actually been in tend to be designed with the aim of keeping heat in rather than maximising solar gain (ie small windows) which leads to a longer heating season .... I know that this is generalisation and solar efficient houses are being built, but it seems that passive solar and passivhaus are different animals in today's terms as whatever the quality of the glazing it still leaks considerably more heat than a well insulated solid wall ....

HTH
Z

Thanks again, that all makes perfect sense. It also explains some of my confusion over heating times. Given that I started with a 1930's semi (sows ear), I've always assumed that I have anything but an efficient house (silk purse). Which has led to further confusion when people talk about heating houses for 10 months of the year, and the benefits of old bulbs v's CFL's (now LED's).

Rather than mess around, we just winter'ize our house, when the heating needs to go on (around late Sept). The heating gets switched on, TRV's get dialled down (to stop them jamming on during warm summer temps), the hallway floor gets its (ugly) winter lino, and the loft stairs get their heavy thermal curtains. Then the reverse around early April (but not last year, or this one yet).

Back to the fictional, super PV'd, Passivhaus, from what you say, the extra generation would probably solve any extended heating needs, since generation outside of Dec and Jan gets big - fast. But getting rid of all the extra export may be a problem. The June generation figure was about 900kWh's. So DNO approval for higher export needed (I have 5.9kW approval).

Or .... and back on (thread) track, a diversionary switch to hot water (or another form of battery). I've mentioned this before, but it is expensive and for larger scale generation at present - the EMMA GVS. This diverts generation when export is approaching DNO limits. It is actually getting approval from more DNO's, thus allowing kWp installs that would otherwise be refused or reduced.

So, avoiding the debate on export, CO2 emissions etc etc, in the right application these switches could allow for larger PV systems to be installed. Larger PV almost certainly means cheaper PV (per kWp), cheaper PV means quicker to reach viability.

Early days, but lots of promising ideas.

Mart.

zeupater

Martyn1981 wrote: »

Thanks again, that all makes perfect sense ....
.... Early days, but lots of promising ideas.

Mart.

Hi

As everything seems to have calmed down a little, I'll try to bring the thread back on topic bringing passivhaus, solar pv, Air/Air heatpumps (/aircon) and switching control together.

If one of the major Air/Air fully modulating heatpump manufacturers modified the control system of their units from modulating on temperature/heating demand and added the ability to modulate heat output (/power draw) by available pv excess generation then your passivhaus/pv heating quandary would be addressed - I'd certainly be interested in a system to provide additional heat in Spring & Autumn. Other variants would obviously include Air/DHW (Domestic Hot Water) which would probably be a realistic (/desirable) energy efficient alternative to devices which simply divert power (Immersun/EMMA etc).

HTH
Z

albyota

zeupater wrote: »

Hi

As everything seems to have calmed down a little, I'll try to bring the thread back on topic bringing passivhaus, solar pv, Air/Air heatpumps (/aircon) and switching control together.

If one of the major Air/Air fully modulating heatpump manufacturers modified the control system of their units from modulating on temperature/heating demand and added the ability to modulate heat output (/power draw) by available pv excess generation then your passivhaus/pv heating quandary would be addressed - I'd certainly be interested in a system to provide additional heat in Spring & Autumn. Other variants would obviously include Air/DHW (Domestic Hot Water) which would probably be a realistic (/desirable) energy efficient alternative to devices which simply divert power (Immersun/EMMA etc).

HTH
Z

Hi

This is pretty much the set up I have, 3.04kWp PV with 8.5kW Ecodan, I have it timed for producing the domestic hot water at midday for about an hour, then goes back to heating the UFH.

Edit, sorry, just read again, you are referring to air to air, however, these do modulate using inverter technology.

zeupater

albyota wrote: »

Hi

This is pretty much the set up I have, 3.04kWp PV with 8.5kW Ecodan, I have it timed for producing the domestic hot water at midday for about an hour, then goes back to heating the UFH.

Edit, sorry, just read again, you are referring to air to air, however, these do modulate using inverter technology.

Hi

No problem, I guess that it would work with ASHP or GSHP too as long as the heating duty wasn't too great. I was really thinking about small heatload systems up to around 2.5kW(ish) which would hopefully modulate the power requirement (given appropriate control) down to a level which a typical pv system would supply in overcast but bright conditions. The modulation of heat output and operation of the HP would be controlled by the available excess generation in a similar way to how the Immersion/EMMA systems work with the exception that it would be integrated into the HP control system alongside the existing temperature control .... considering that the change to the logic control unit and the input/interfaces of the HP would be pretty minimal, the cost implications,(including the relevant clamps transmitters) on the system should be quite small.

HTH
Z