Ed Davies

OTOH, having your charger track the spare output from your PV panels would be nice (and doesn't need any connection external to your household).

Roughly speaking, for constant absolute or specific humidity [¹], the RH doubles for every 10 °C drop in temperature so if there's temperature difference of about 20 °C between indoors and outdoors the outside RH would be just about 100% if it's 27% indoors. [¹] I forget which, it doesn't make much difference anyway.

Yes, Wago DIN rail connectors is the best I can think of, too, but I can't help feeling that for the number of connections involved there could be a neater and more economical solution.

@scottishjohn, absolutely. Using solar thermal for DHW pre-heat and also for space heating is my plan but not using the same tank for the two jobs. However, this thread is about using an ASHP with a Sunamp - my post you were originally responding to was about using the ASHP to preheat the water going into the Sunamp. I just mentioned my intention to use solar thermal in a similar way. Let's not derail the main discussion - start a separate one if you want to.

Your post covers two separate issues: 1) interseasonal (or nearly so) storage for space heating and 2) use of solar thermal for DHW pre-heat. Only the second is on topic for this thread so I'll address that. Exactly. That's ideal for pre-heating DHW to then be topped up to the temperature it'll actually be used at by a SunAmp or whatever so a large buffer tank is not required, just one to cover a day or two's usage which won't be much different from a normal domestic DHW tank.

Accidentally posted while linking your name - post fixed now.

Actually @SteamyTea quoted that. Still, it's not quite how the term is typically use now: what people mean is IR around 10 µm rather than specifically longer than that wavelength. 8 µm radiation would be considered far IR, for example. Thermal infrared cameras detect far IR but definitely pick up wavelengths shorter than 10 µm.

Ring finals: more complex testing, fail dangerous, less flexible, just to save a roll of cable. They made sense in 1944 when the assumption was space heating would be from multiple direct electric heaters and copper was in short supply but do they in 2019 when the sockets in most rooms, except the kitchen, won't draw a total of more than a few amps? So, for lighting, what's the actual distribution panel? A cupboard full of Wago connectors or something a bit more structured?

Maybe just nicked a toenail. No reason you can't use the 50mm insulation you've got with more underneath. The tricky bit with insulation between joists is thinking about what moisture will do and how it'll dry out properly, particularly if the insulation goes below the joists. Understand you have 300mm (from top of joists?) do ground level - how deep are your joists?

I like SketchUp but, yes, it does require some learning as its use of the control, shift and mouse buttons is err… unique. It's well worth watching a few YouTube tutorials on the basics to avoid some frustration. I've two blog posts on tricks with using it, the second of which contains some links which might be helpful: https://edavies.me.uk/2012/12/sketchup-component-layers/ https://edavies.me.uk/2014/01/sketchup-components-and-groups/

That's completely pointless. PV panels are fine in direct sunlight if you don't take the energy away, unlike some solar thermal panels. They just radiate away the excess as thermal infrared in much the way that any similar-coloured object left out in the sun would. If the house and the distribution network both don't want the power then just don't take the DC current needed for it. The only “issue” is making sure either the generation or the export (depending on your chosen interpretation of the rules) is limited to 16 A/phase in a manner which is approved by the DNO. I highly doubt they'd accept blinds over the panels, however operated or controlled, for that purpose. Summer isn't usually the time of peak production, anyway. Normally that happens in late spring. E.g., for south-facing panels at 35° inclination near Kirkcudbright the peak month, according to PVGIS, is May.

Either you use it in the house or the inverter sees that the export current is approaching 16 amps and stops taking so much power from the panels by taking less current and allowing the panel voltage to rise above Vmpp so the extra power gets dissipated as heat in the PV panels. Obviously, if you've got a good use for it in the house then it's better it goes to that. However, whatever diverter or other mechanism used to control that doesn't have to be one accepted by the DNO if they accept the export limit of the inverter as a backstop.

I doubt it does.

For reference, here's the actual law: http://www.legislation.gov.uk/uksi/2002/2665/regulation/22/made It seems to me that there are three possible interpretations of the 16 amp limit: 1) 16 amps per source of energy (so you could have two separate PV systems producing a total of 32 amps). 2) 16 amps total generation per installation. 3) 16 amps maximum export from the installation, so you can generate more so long as you can convince the DNO that not more than 16 amps will be exported. 1 is obviously silly but looking at the wording of the SI isn't obviously ruled out. 2 seems to be @willbish's DNO's interpretation. Assuming 1 is eliminated it's not a mad reading of the legislation. However, 3 is what's been widely understood on other forums. How you convince them has been a bit DNO dependent. IIRC, Western Power used to accept one particular diverter for this purpose. I think there are now inverters which operate with a current clamp so they'll limit export, i.e., they'll generate more than 16 amps so long as you're using the excess in house, which are accepted by some DNOs. My understanding of the reasons for the change from G59 to G98 (I'm assuming @ProDave's got the numbers right here, I can't remember them) is that under the old rules the inverters would all drop out simultaneously when the frequency got low. The worry, particularly in Germany, was that if the grid was struggling as indicated by low frequency and voltage, it could happen that all the PV (and small-scale wind) could drop out together resulting in a cascading failure. Under the new rules they drop out more slowly likely resulting in a more managed and local failure.

Of course. They won't get really hot if it's cloudy but they would put some warmth in. Probably better to have some plastic pipe or something keeping the fluid in the panels and the acid separate, though. ?

@Onoff Didn't you have some solar thermal tubes? Did any survive?

Lots of ways to calculate this but whatever, it looks like there's a decimal point slip in there so it's probably more like 1.3 tonnes rather than 13 tonnes of CO₂. The current carbon index of the grid (total CO₂ emissions / total generation) is not very interesting from this point of view. Generally speaking, low-carbon power sources (renewables and nuclear) do their thing at whatever rate they can manage at the moment then gas makes up the difference. This means that any additional renewable generation (used sensibly) directly reduces the amount of gas burned so should really be “scored” at minus the emissions rate for a closed-cycle gas turbine, not the grid average at that moment.

There are stories, possibly apocryphal, that requests for confirmation that there's no TPO has triggered the making of a TPO so probably best to leave the enquiry to within days of work starting.

Is there an NRV on the cold feed to the tank to stop heated water flowing back out of the cold tap? Without an NRV it wouldn't in normal operation but might if, say, the cold supply was turned off.

Wholesale electricity prices in the UK have gone negative but I think it's only for very short periods, like a few times ever. I don't remember but rather doubt it was in the winter, more like breezy summer nights I'd expect. It happened first and more often in Germany. With the increasing amount of battery storage and so on on the grid I really doubt domestic users would make anything much this way on a smart meter but they might get some very cheap electricity. Not that up to date on it all, though.

I didn't see them claim that. I think it just switches off its charging when the grid's having a bit of bother. One size doesn't fit all. There are places were you can't have a heat pump and can't have gas where direct electric is pretty much the only option. E.g., many flats and perhaps some houses in conservation areas. Something like this would be a big step up from direct-to-room electric heating ('cause you can charge it on E7 or whatever) and be more comfortable and controllable than traditional brick-to-air night-storage heaters if it's practical to put in wet radiators or UFH.

I'd think that wind load would be more significant than the weight of whatever plausible material you might use. Scaffold sheeting might be worth looking at. Mine, as shown in that blog post, failed but the initial failures were mostly due to the ropes I used to tie the sheets to the frame chaffing through on the corners of the timbers. Only when a few of those had failed and largish areas were flapping around did the scaffold sheeting itself start to rip. There do bungee-like cords with plastic bits on the ends to stitch the edges of that sheeting to scaffold poles - they'd probably do a lot better than ropes round squared-off timber.

Do you mean SWA?

That must be a quite recent change then,

@gc100, which country are you in? The rules vary between UK countries but in, for example, Scotland, a turbine in open countryside could well be permitted development, i.e., not need planning permission as such though there's a bit of bureaucracy to go through to check it meets all the rules.