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@twrch
Try these.
But in the mean time “efficiency”. It’s not that we are giving people less power - brutally we don’t really care, particularly as it doesn’t really change network utilisation much because as you note the current changes less than the power. It’s that if peoples appliances run at a lower voltage they run more efficiently and need less power.
And as for appliance manufacturers cottoning on, in practice they probably already have. A CE marked appliance will have its efficiency sweet spot somewhere around the perceived usual voltage, and even with voltage harmonisation, GB voltages are higher than average in Europe. So probably the sweet spot will be tuned a bit lower than we see in this country.
As for EV chargers, they probably are constant power devices (though they don’t have to be, that can be designed in or out), but they probably aren’t constant efficiency devices.
Taking a silly example, and EV chargers will be far more complex, if I put 220V into your phone charger do you think it will run hotter or cooler than if I put 250V in? I don’t know, but I suspect it will be cooler at 220V. That’s energy that was never charging your phone.
Is that the whole of the efficiency gain, I doubt it, but it’s more convincing than the resistive load that although it runs at a lower power runs for longer. My suspicion is that the long run energy reduction from lower voltages into resistive loads is actually negligible, due to thermostats, bimetallic strip switches and people simply letting things run longer. It’ll work for OC6 load reduction though as that is about power not energy.
@maxtorque the concept of a massive thermal store + heat pump sounds interesting. Do people actually deploy such solutions?
I'd be wary of burying such a thing because of future maintenance issues, probably because of my chemistry teacher's story of a buried HCl pipeline that leaked at the papermill he used to work out that nearly took out the town's main water main...
I haven’t read this whole thread but please don’t make the mistake of thinking you can use solar pv generation for heating your house, even with batteries. For the months you need to heat a house you generate bugger all with pv and batteries won’t store from September to February. And whoever just built a new house with electric ufh. I’m so sorry for you but you were given terrible advice, passive house or not.
By definition a passive house requires so little heating it really doesn't matter what type of heating you choose:
The Space Heating Energy Demand is not to exceed 15 kWh per square meter of net living space (treated floor area) per year or 10 W per square meter peak demand.
For a 100m2 that's 1500 kWh per year or 1kW peak demand.
In terms of cost electric ufh would cost you £225 at 15p/kWh. In terms of being able to power that with pv in December you'd need about 30 high output panels angled for Winter sun, fewer if they were sun tracking. The rest of the year you'd be exporting leccy.
Edit: Our house requires about double the passivhaus standard of heating. Partly because it's retro-insulated and still has a few thermal bridges where internal walls meet external walls, but also because Madame won't put up with 18°C when sitting working. It require's about 3000kWh a year which means a couple of m3 of wood or one oil-filled radiator, just one for the whole house.
You can’t heat a house on pv as most of the time the sun dosnt shine in the winter in the uk and if it is shining you won’t actually need to add extra heat. I do actually live in a passive house and I am also a passive house consultant. Direct electric heating isn’t considered sensible in passive houses, maybe in tiny flats in some instances. It is a mistake to only look at the heating load in a passive house. You still need to heat hot water so why not use that source to also heat the house?
I’m interested in this notional amazing house that is only 100m2 yet somehow has roof space for 30 solar panels that can produce power in the middle of the night to keep up with the 1kw heating load.
You know how much the temperature of a house varies once it's well insulated? Not very much at all. We never ever heat at night. I rarely, very rarely heat in the day before 17:00. It's currently (12:57) 18°C having not heated since yesterday evening, I'll have a burn when Madame gets home and that will get it up to about 20°C. When it's below zero outside I refill once or twice in the evening.
Hot water? The solar thermal provides for our needs for 6-7 months. The rest of the year the solar thermal tank feeds a normal electrical tank which takes the water up from tepid to shower temperature. The solar thermal divides domestic hot water heating electricity demand by about four. It thermo-syphons so requires no pumps, electrics or maintenance beyond a twice yearly panel clean and once a year fluid top-up.
Not my house, but you get the idea. 30 panels is achievable on many houses. I've only got 14 but will add some more when the current feed-in contract ends.
Not my house, but you get the idea. 30 panels is achievable on many houses.
That house isn't 100sqm.
Mines 130sqm I've got 12 on my roof. Might get another 2 on if I pushed it ....
That house is an irrelevant example. It is clearly much bigger than 100msq and does not have a roof design you would normally find in uk housing stock. Lots of uk houses are unable to even fit 3.7 kw of solar, which generate almost nothing on dull winter days.
Mine's 68m2, I've got 14, there's space for another one and space for another 10 on the garage.
For some people it's possible for others it's not.
What is possible for the vast majority of households including you Trail-rat is vastly upgrading insulation standards.
The roof is the only thing most households get anywhere near acceptable standards.
A insulated cavity wall is about R=1.5. You can get to R3.5 with 10-12cm of insulation on the inside of a wall which will have none of the risks of insulating the cavity (you'll complain about losing living space until you realise that removing radiators will gain you that space back). Current double or triple glazing will drop uw to 0.9-1.2. Insulating under thee floor is often not done at all. If you have sanitary space it's easy to get to R=3 for the floor. Secondary double glaze doors or fit double doors and insulate what you can.
Insulating under thee floor is often not done at all. If you have sanitary space it’s easy to get to R=3 for the floor. Secondary double glaze doors or fit double doors and insulate what you can.
This is next weeks job for me and son no.1, suspended floors (thankfully the house was built on a concrete slab and there's enough room to crawl about) with no insulation currently. 200mm loft insulation with a breathable membrane will be going in next week. Loft is already 300mm thick and previous owner had cavity wall insulation carried out.
Back to your strong assumption game there I see.
You are aware I removed the back of my house and rebuilt it 3m further away with 150mm insulation in the wall and the roof.
And 150mm (maybe more can't remember and can't tell from the build photos)in the floor tbh if all I'm aiming for is your heating outlined above then I'm already there. Our oil heating hasn't used 1 bar the whole year (140l)
For me the next move to reduce the dependence on oil is to fit a thermal store/water tank of some kind and use the immersion dump for that.
And once cost come.back down I'll get the front windows modernised to match the rear.
You'll stop dissing EVs one day. 🙂
Did you miss the thread where I'm looking at buying outright twizzy for my local usage /client visits once they start up again ?
No, I didn't. Only fools don't change their minds, eh!