JohnMo

Surely that never happens 😜

That would be right! We're being ripped off like everyone else

Looked at Scotland's production profile, it has approx 10% of all production installed capacity as gas, the rest is renewables and nuclear. General average of 97% of electrical generation comes from a none CO2 source. Gas is pretty much only used as and when needed.

Nice, but well over budget. Or on budget in some other alternative reality, like some of these builds on TV tend to be.

I read Stiebel Eltron ASHP manual a while ago, it went in to exactly what the min flow and system volume you were to provide for their heat pump. If you could not provide both the flow and system volume you had to add a buffer to meet or exceed those requirements. Making the sizing or need of a buffer pretty easy. May be worth finding a Stiebel Eltron manual for size heat pump and see what it says.

You may be better running in weather compensation mode anyway, so it runs at very low flow temps, so get a better CoP. Run in day and overnight in set back mode (2-3 degrees lower temp), and normal mode when your home.

Is that 14 zone (thermostat with time control) or 14 UFH loops? If it's zones I would reduce to one upstairs and one downstairs. Use the thermostat as a limit stop, tune flow temp and rates to get room temp where you need them. I would say your flow temperature is set incorrectly. For cylinder heating (45-46 cylinder temperature) you would need a slightly high flow temp 50ish, otherwise your heat pump will struggle to get the cylinder up to temp and use needless energy. For UFH your flow temp should be no more than about 30.

None of options are easy. I want to install some more panels on a wall on the drive, no shading, but wife says no.

Your getting a CoP of less than two. I would be looking at flow temperature for UFH and hot water cylinder, you should be Getty a higher efficiency than you appear to be doing. Other things that effect efficiency Too many zones, cause short cycling To many many on/off cycling of heating timers and thermostats

You can also change the angle. Vertical mounted panels flattens the output curve, a more flat mounting position, decrease winter output in favour of summer production. Best idea is mess with tool linked to previously, to get a system that suits you and your available mounting positions.

Just size the array to suit your needs, make it smaller

Just use a normal string inverter but add Tigo optimisers to each panel.

I just purchased a lot of ultra signature composite decking planks, they come with a 25 year warranty, so hope I don't get an issue.

No to human, but the way we are going we kill our selves off. Cows yes. They could be banned, they emit loads of methane also

They only bothered with CO2 emissions reduction - blunt stick approach will do

Another way I found was (in US units) V= t(Qhsmin – Qloadmin)/500(delta T) V = minimum buffer tank volume (gallons) t = minimum heat source on time (minutes) Qhsmin = minimum stable heat output of heat source (Btu/hr) Qloadmin = minimum concurrent heating load when heat source is on (Btu/hr) ΔT = change in average tank temperature during minimum heat source on time (ºF)

MCS give this as formula with a worked example. Looking at the system volume. Example: A 12kW nominal inverter controlled heat pump unit (at 7oC ambient and 35oC water flow) can provide an output of 4kW at maximum turn down (minimum output) at an ambient of 12oC and weather compensated flow temperature of 30oC. What is the minimum water content to ensure cycling does not exceed six starts per hour? Assume acceptable temperature drop of fluid is 5oC and the fluid has a SHC of 4 [kJ/oC kg] because it has antifreeze in it (normally 4.18[kJ/oC kg]) Total heat energy required: 4 [kW = kJ/s x 60/6] [minutes/number] x 60 [secs/min] = 2,400 [kJ] Mass of water required [kg] = 2400 [kJ]/(4 [kJ/oC kg] x 5 [oC] = 120 [kg] Assume 1 kg of water = 1 litre, therefore 120 litres required.

It's a difficult call, you can build a basic house quite cheaply, the costs go up with the outside finish, floor finish and kitchen and bathrooms and glazing. Plus bells and whistles that may not be needed. Your going to have to do lots yourself to make it work. GSHP, PV, will kill the budget unless your in the digger doing the trenches, even then you may not see change out £6-7k for GSHP. Your rear glazing may need to be simplified (made smaller, dump bi folds etc), to make the budget work, AC is another £1-2k plus F gas engineer to install. If it were me, and I really needed to control the budget. Find a builder you like, use their preferred build method, render finish, insulate really well, make a reasonable air tightness, to allow MEV, dMEV ventilation that is humidity sensitive, so it ventilates only when needed. Drop the Juliet balcony, drop bi folds and make french doors with fixed panel either side, ASHP, UFH downstairs (single zone) radiators in bedrooms. Find a kitchen install company work with on a good kitchen design, but give them a small budget. Same with bathrooms.

We used real stone cladding, they do a black slate. https://www.realstonecladding.co.uk/black-slate

Just watch your not getting taken for a ride with pricing. To buy the parts you are looking circa £1k per kWh, the bigger the array the more economical it becomes. If you any risk of shadow that includes clouds you need optimisers on each panel. You need an external DC isolation switch even if the inverter has one. It is likely the inverter could fail before the panels, the additional DC isolation allows the inverter to be removed safely.

https://re.jrc.ec.europa.eu/pvg_tools/en/ Use the tool, to get a good estimate of output by month

Little confused. In Jan your output from PV for the month will be around 150kWh, some days the output will be zero, but if we average to 31 days of equal generation, 4.8kWh per day. Even getting a CoP of 4, that less than 2 hours of running the heat pump. So full use from PV without any other loads. In summer you are generating circa 400kWh per month, 13kWh per day, a couple of hours doing hot water, would 5.6kWh, other background uses, washing machine, dishwasher etc plus immersion to bump up cylinder temp to max, all the PV is used.

You don't mention size of ASHP nor PV array size. We have 3.1kW of PV and gas boiler (so should be easier for you to self use). Since middle of June I have exported 43kWh (5 to 600kWh generated), this was only exported because my immersion was miss reading and only charging the cylinder to 55 degC. This has since been fixed and now exporting nothing.

Does that make sense? A storage combi should give you an endless supply of hot water, at better flow rates than a normal combi. Our Atag combi was doing two high flow showers at a time this weekend without complaint from the boiler or the users.

Have you got a huge gap in your insulation between roof and wall?