Ed Davies

For YouTube on mainstream climate science then you could do a lot worse than this video, even though it's almost a decade old:

Sorry, I should have been clearer: when I wrote “solar cycles” I meant the cycles in the parameters of the Earth's orbit and orientation which affect solar input to the Earth, the Milankovic cycles, not the cycles in the solar output. Correction made above. It's not just the biosphere fixing carbon, it happens purely by chemical means as well. That the fixing is temperature dependent and that it forms a long-term feedback to stabilize the temperature is well known. That variations in insolation and tectonic uplifts can affect this is also well established. See for example: http://www.columbia.edu/~vjd1/carbon.htm , especially the very last section: “The Climate Buffer”. I'm sure I've read more definitive articles on the subject but not for a while (a decade or so, it's really basic stuff) and I can't remember exactly where. No, temperature affects CO₂ and CO₂ affects temperature.

After some contemplation, a more succinct answer: 1) Yes, over billions of years CO₂ is on the decline due to the increasing brightness of the Sun. 2) Yes, over 10's of millions of years CO₂ is on the decline (I think because of the uplift of the Himalayas and Tibet, but maybe I'm misremembering this). 3) Yes, over thousands of years temperatures have been on the decline due to solar Milankovic cycles. But, we've already emitted enough CO₂ to deal with the possibility of 3 kicking us into a new glaciation. Current emissions are irrelevant on the timescales of 1 and 2. So our priorities should be set on not getting ourselves back to the mass extinction near the beginning of 2.

@epsilonGreedy, I really don't think your graph supports the notion “that global CO2 levels are in a longterm decline that started with the arrival of life on planet earth”. For starters, there was a huge increase from 350 to 200 million years ago. It is true that over much shorter intervals (the 65 million years or so, since about when the non-bird dinosaurs went extinct) there's been an overall decline in CO₂ levels. Note, though, those peaks in @JSHarris's graph in box b around 55 million years ago. This was the PETM which was another mass-extinction event. Since then CO₂ levels have indeed been declining steadily resulting in the current ice age (which started 2.5 million years ago or so) and in which human civilization appeared in the current interglacial which started about 12'000 years ago. We've already put out enough CO₂ to delay the onset of the next glaciation by many thousands of years. It's even possible that humans had already done that via agricultural land-use change prior to the industrial revolution. So there really isn't anything urgent to do from that point of view. Long term (multiple millions a few billions of years) there will indeed be a problem with reduction of CO₂. The Sun is gradually getting brighter which will result in long-term feedbacks in the carbon cycle reducing the amount of CO₂ to the point where photosynthesis won't work. CO₂ is pretty long lived in the atmosphere but burning some LPG today isn't going to make much difference on these timescales. Humans, if still around, will have to come up with another plan then. Somewhat shorter term, current CO₂ emissions clearly are raising Earth's temperature and messing with the climate. As the graph @JSHarris quotes shows, the PETM is a plausible model for the results; compare the CO₂ levels in the various possible concentration pathways in box d with the bump on the left of box b.

Woz at? Typo for PUR? Something else?

Or solar thermal.

But there are probably many rural lines where there's a bigger voltage swing. It's the DNO's problem, of course, but still interesting to consider the consequences.

Good point, the ESQCR specify the nominal voltage (230 V) and allowed tolerance (+10/-6%) but don't say anything about the rate of variation or similar within that band. I expect quite a lot of equipment would be unhappy if the supply kept changing between 216 and 253 volts every few cycles even though that's literally within the spec. E.g., if you're living in the same road as a bunch of @ProDaves who all turn their immersions on and off at that sort of rate.

The security of the mobile phone network as such ought not to be too relevant as the data sent in each direction between the meter and the control centre is encrypted and signed. GCHQ intervened in the design process to fix some loopholes in that protocol because they were worried about the potential national infrastructure vulnerabilities. Whether the data centres will be kept adequately secure in the long run is a different question, though. If they ever leak the private keys needed to control peoples' meters things will get interesting.

Ah, that makes sense. I'd assumed filling the tank. I always do to get the price breaks, e.g., I think the supplier here has one at 750 or 800 litres so it's not worth messing around with a 1000 litre tank, just fill it. Still, if you want to do measurements that'd be an additional argument for filling up to get to a better defined level.

Yes, they sound plausible. The 11 kWh/litre is probably a tad optimistic but given the other guestimating (e.g., of the efficiency and extrapolation to annual usage) it doesn't really matter. How does filling up with 500 litres lead to you reckoning you've used 600 litres? Here's my similar estimate: Burning Oil . 1 kWh = 3.6 MJ Why estimate annual usage if you're wonder what a beck which runs mostly in winter will contribute? Wouldn't it better to compare with just winter usage, anyway?

True, but not as significant as you might think.

OK, that makes less difference than I thought. Still, the buffer tank will be at room temperature when the UFH is off so will still raise the incoming cold water from something like 8 °C to around 19 °C.

Talking to my crofting neighbour, who probably knows more about fences than most, I asked if concreting in the fence posts would just make them rot by trapping water. Yes, says he, eventually, but it's the bit just about ground level that rots first whatever you do so you might as well make them solid.

@JSHarris, you prewarm the cold water going into the Sunamp with a UFH-temperature buffer, don't you? So the costs for doing direct heating for all your hot water heating would be a bit higher, wouldn't they? If not then 4.6 kWh per day for two people is quite low. The usual rule of thumb is 3 kWh/person/day.

Yep, we're furiously agreeing. I and @ProDave are just clarifying why that argument wouldn't apply to these NexGen heaters.

Indeed, that's at least a plausible claim. But in this particular case these NexGen heaters are designed to be under the floor or in the wall so I can't see how they can affect the radiation from the surface - it'll just radiate, convect and conduct as it would with any other heater as a function of its temperature.

@JSHarris gave some reasonable links for background. More specifically, I use Thunderbird for all my email (and have since it was Netscape Communicator) which has a plugin called Enigmail which handles it reasonably straightforwardly once you understand the basics of public and private keys, etc. The underlying Pretty Good Privacy (OpenPGP) standard and its most common implementation, GNU Privacy Guard (GPG, which Enigmail uses behind the scenes), are pretty gnarly to use but there's been a steady stream of standard setting, etc, to paper over the cracks. In particular, the original idea of PGP was that people would verify and sign each other's keys then other people who knew them could know to trust further keys via what was called the web of trust. This sort of worked in some circles but never really took off more widely. Now there's more of a move to automatically include key information in the email header to use a principle of trust-on-first-use (TOFU) so you build up trust in a key via a conversation and get an alert if somebody suddenly seems to start using a different key. This is also the way the more secure messaging services like Signal work. It's not something that'll be universally adopted overnight but a steady move to more signing and encryption would help a lot with security, IMHO. OTOH, it's the software that's fundamentally broken, not your MiL, if clicking on a link can install malware. Telling people not to click links is just a temporary workaround at best. Telling people not to put private information into websites they haven't verified might be more useful if verification was a bit easier.

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 Sorry, I didn't think my comment needed the “/sarcasm” tag. Indeed you can't send money by email but with digital signatures you can verify that an email updating bank details, or whatever, is valid. In less technically-backward countries (e.g, Austria, Estonia, Switzerland and, I think, the Netherlands) use of digital signatures with keys signed by government entities is pretty routine. Here the government just tries to ban secure cryptography. -----BEGIN PGP SIGNATURE----- iQGzBAEBCgAdFiEEklM8otTd5M2cZSSDAHFYLlN5hIEFAly2U6kACgkQAHFYLlN5 hIF8ogv+Ne9TMHtLrEWAoAj9PLEiTy29wmEbjZpo0zntuQEuI9nU19VennDG/fe8 UQeaTtCh1Q7UWt7RbZSJqXyjN0s/pWhtZ76crQnAn0maFud4EPjGe7B57XqBlFoh PNkoL0PD8d72YDS0xHiKi2HooY4PKBWCoruuXAPO4RgcEb8e3/0Sc/m88SHwK4yS vPgDha2DCLHqz3tfyVuAkajPcsEsiboOBwiykB+P+BQu2aGqaxtTqwee595oBxih 0Mkrxo2oyOMVhxzYLN20RYh30q6IeZXB8/ClaCX6Kp55Er2g9OimYslvW/N2ACdB gaMSYBCrWuXB67lLgMtNGOrxCgrXp37hwBtQx9fQIcU1vMfTX5R4ZU+dg54E/5/x oXsqqKEbvr3LVA0X0+VfL25HThoP1tlS5N3/OMIMn/wzif9EaRD5nSPEm5rtVpaR WFrBHZNHb9XFhUOsVxYshxQTCti6RY3iByaqDo3OPnKKb8YJZj4L2XcEpiFmjDcu GDsysJFO =hpOA -----END PGP SIGNATURE-----

But we all digitally sign our emails, don't we?

Bearing in mind that heating for hot water is likely to be in the same ballpark (e.g., 3 people x 3 kWh/peep·day x 365 days/year = 3285 kWh/year) you'll get almost as much reduction on that with an ASHP. Obviously depends on the number of people and your water usage. At a COP of 3 on an ASHP and assuming £0.17/kWh your total heating bill would be >>> (3 * 365 * 3 + 226 * 15) /3 * .17 378.25 Take off the standing charge and boiler servicing costs and work out how long the payback on gas connection would be. It seems to me this is one of the places where it really doesn't cost that much financially to be a little less un-green.

Getting back to the original topic, I too don't think a thick slab is all that necessary and may sometimes be harmful. In general, I don't think living too close to the thermal store is a good idea. This is a generalization of concerns that Earthship-style designs are not likely to work too well for houses with significant temperature swings with longer than diurnal periods. E.g., the Hockerton houses get cooler than I would be happy with in the winter. Presumably this could be fixed by harvesting more heat in the summer and autumn but the cost of that would be having the houses hotter than would probably be comfortable. A thick slab seems to do three things: 1) provide structure so that localized loads are spread over the insulation below, 2) act as a heat store so that timed heat sources (e.g., solar or E7) can be used 24 hours. 3) act as a buffer to moderate the room temperature. I don't know about (1). I've previously suggested CLT for this but nobody seemed much interested. Whatever, it seems to me there's better ways that don't involve so much embodied emissions. The problem with the slab as a heat store is that there's very little temperature variation which can be tolerated so the usable heat capacity is quite small. This is because there's no control of the way heat comes out of the store. So we're left with it acting as a buffer to moderate room temperature. That's an awful lot of concrete to use to avoid a relatively simple control problem.

Bear in mind that you can (usually, depending on the heat pump/controller model?) run the ASHP at different temperatures depending on what it's heating. AIUI, the usual thing is to run it in either of two modes: UFH or DHW. When you want to heat the DHW you stop heating the UFH for a while. You can then set the flow temperatures differently for the two modes.

It'd only be strange if actual changes in outdoor CO₂ or O₂ proportions directly affect air quality (i.e., human health). It's well understood that indoor CO₂ concentrations can have such an effect but I know of no reliable evidence that the relatively small variations in outdoor CO₂ or even smaller changes in O₂ levels matter. The fact that air quality survey equipment does not routinely report O₂ levels is at least an indication that those responsible for the measurements don't think O₂ level changes matter. They could be wrong, of course, but I think more than a small set of measurements from equipment not intended for that purpose would be needed to be at all convincing. (The steady increase in overall outdoor CO₂ levels does have indirect effects on human health via climate change and ocean acidification. However, measuring levels on a day-to-day basis in city centres, etc, won't tell us much interesting about that.)