I've always been surprised that nobody has done home cogeneration for heat and hot water. Seems like an absolute no-brainer way to get a lot more mileage out of gas.
I read about a Mitsubishi home gas cogeneration system many years ago (10 ish). I think they haven’t taken off because they are expensive, only suitable in certain climates, and significantly less efficient at producing electricity from gas than a recent model combined cycle gas power plant.
Even if it were pitifully inefficient at making electricity it would still be better than just burning gas for heat, which wastes all of its thermodynamic work potential. Waste heat is still heat.
In Iceland, they cogenerate hot water and power due to the abundance of geothermal. Not exactly a common case that's replicable everywhere, but mildly interesting.
Genuine, this-never-occurred-to-me question: are there lots of people out there with boilers that DON'T do this, or areas where it is not normal?
If so - this might explain something that's been mildly irritating me. When looking for alternatives to fuel-burning boilers it seems easy to find positive stories about space heating - and much less info on water heating, to the point where it's starting to look like maybe some of these options might not be great. Water heating is my largest home energy usage and space heating very little because it is grossly overrated; if you are not really unwell an indoor temperature around 10 c is quite pleasant, so I tore my (rubbish) radiators out in 2017 and never looked back. This is making it surprisingly hard to figure out what replaces the boiler. If the marketing is aimed at pure heating boiler replacers, this difficulty is at least easier understood if not easier solved.
I would personally not like to live in 10°C but I prefer hot climates. 15°C I could do. How do you keep the temperature above 10°C? Or is the outside temp rarely below 10°C?
Thanks! that looks technically similar to the heat pumps aimed at space heating but a bit better - perhaps there's an efficiency in it being meant to do just one job? It looks like it (or its ilk) might be a good fit for me.
Outside wobbles around -2 to 8 in winter here, inside rarely less than 6, which is nippy but not dangerous. A not very insulated house with solid walls (this one's from about 1890 and has only had the easy things done) doesn't really sink to outside temperature if you live in it, cook, have appliances etc. There are plenty of heat inputs, just they do another job first. Hence my interest in water heat, I think it would start to be grim without it. Stove for a small number of really cold evenings, plus visitors. It would be a really bad idea to use it all the time but it would be hard to fit a radiator-type system to the job of "one hot room occasionally".
> Genuine, this-never-occurred-to-me question: are there lots of people out there with boilers that DON'T do this, or areas where it is not normal?
I understand that american indoors heating is mostly done through HVAC. Since in that case the heater would be heating the air directly, you'd need a separate boiler. Heating water to heat the air makes sense when water is your transfer medium (e.g. hot water radiators), less so when the air is.
So I expect US homes usually have separate air furnace and boiler, whereas in e.g. europe where water central heating is common you'd usually have a combined furnace/boiler.
Draughts :-) It's an old place, it doesn't seal. That and sleeping in rooms with the window open just a crack as much as possible. Mould tends to hit when people obsessively seal everything up.
I still have a condensation problem in a few specific places I have to keep an eye on. It's not general.
I think he's asking about the common trap people seem to fall into where, trying to keep heat in, they shut down air changes too far. Human breath puts a surprising amount of moisture into the air, and cooking can too. If you let that build up and have a cold wall it can build up a film of damp very quickly and if it's left damp and cool it can encourage mould. That kind of bad air quality is far worse than a bit of a chill.
