Comment by samwillis | Hacker News Reader

Comment by samwillis | Hacker News Reader

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I believe the idea is that it solves two problems simultaneously, using excess wind when it’s available and making our domestic gas supplies “greener”.

The vast majority of uk homes have gas powered central heating (hot water radiators), there is no good route forward to upgrade/replace all of this infrastructure to make it “green”. You can’t economically run a hot water central heating system using an electric heat pump, the required temperatures are too high, so you either need to rip it out and replace the whole system with a modern one or at least either replace all the radiators with underfloor heating or masive wall mounted radiators (very expensive for the 10s millions of homes, this isn’t just a new boiler).

A hybrid hydrogen/natural gas or synthetic gas is a way to go green but keep the existing infrastructure either with a new boiler or hopefully minor component changes.

So while it may not technically be “best usage” in the academic sense, it could be argued that it is a sensible use economically for the UK.

If you have to use electricity to produce hydrogen it is more efficient to instead use that electricity directly for hot water and a heat pump for space heating. There is no need to 'rip it out and replace the whole system' to use a heat pump; an air to air heat pump as used in many Scandinavian homes can be fitted at much lower cost without disturbing the existing central heating at all.

I don't understand why heat pump solutions in the UK are so expensive. An air to air heat pump from Samsung can be had for a thousand pounds and installation for another five hundred here in Norway; see https://www.elkjop.no/product/hjem-og-husholdning/oppvarming... for instance.

This is rated for room areas up to 100 m2 so plenty enough for the average UK home. Buy two if you want the upstairs heated separately.

> I don't understand why heat pump solutions in the UK are so expensive. An air to air heat pump from Samsung can be had for a thousand pounds and installation for another five hundred here in Norway

Hot air heating is missing in discussions in the UK. I don't know why; I speculate that it's because it got a bad reputation in the 1980s when it was fitted to new build houses and is perceived as ineffective. Certainly the conversations I've had with people all go "I ripped out the hot air system and replaced it with (conventional) hot water radiators and a gas boiler and the house is toasty warm". The draughty nature of UK housing may also be a factor.

What's the situation in Norway and other countries? Is hot air heating widely used? In what kinds of properties do you use air to air heat pumps?

> What's the situation in Norway and other countries? Is hot air heating widely used?

Central heating of any kind is rare in Norway. There is widespread use of underfloor heating (either water borne or electric) in bathrooms. Its fairly common in living rooms too but definitely not the majority.

Most people use electric panel heaters and a wood burner. In the past we used quite a lot of paraffin burnt in a pot burner in the centre of the house which could keep most of my 130 m2 house warmer than we wanted. That's no longer allowed so I burn wood (compressed wood waste from sawmills).

> In what kinds of properties do you use air to air heat pumps?

All kinds of free standing houses, terraced houses. My next door neighbour has two, one for the ground floor and another for the bedrooms in the floor above.

The only thing holding me back from getting a heat pump is that the wiring in my house is not up to it so it would be a substantial extra cost to get that upgraded. That's not a problem for most UK houses or recently built Norwegian ones.

In this small town of 6000 people I think that probably one in four of the detached and semi-detached houses have air to air heat pumps.

US single family homes are, by a large margin, primarily heated via the central air system (the same ductwork that supplies cold air in summer).

My experience with both is that I prefer central air heat. That said, they will perform worse in a drafty house- air is a very poor carrier and storage medium for heat compared to water, so if you have a room with a draft away from your thermostat, it'll get colder faster; a radiator in the room would essentially act as a heat bank.

> There is no need to 'rip it out and replace the whole system' to use a heat pump; an air to air heat pump as used in many Scandinavian homes can be fitted at much lower cost without disturbing the existing central heating at all.

I understood that heat pumps work more efficiently in homes that are a) well insulated, and b) where the heating system is designed to work at lower temperatures (bigger radiators/underfloor heating and appropriate pipes). Whether or not a & b are must-haves or nice to have I'm not 100% sure about - I guess it depends.

(see e.g. https://energysavingtrust.org.uk/advice/in-depth-guide-to-he... - Designing and operating your heat pump system)

Homes that use gas in the UK typically have a gas boiler that provides both hot water for heating and domestic use (taps). They heat the water on demand, there is no facility for storing the water. Heat pumps as we have now cannot be used like that, they will slowly extract heat from the source (e.g. the air) and use it to heat up water in a buffer tank (typically a few hundred litres) - so retrofitting would mean not just replacing the boiler, but finding space for a large water tank.

A better alternative is thermal batteries, which can charge when electricity is cheap. This has actually been around for a long time in the UK as storage heaters, but now systems are coming to market that can be used to replace traditional boilers and provide hot water:

https://sunamp.com/residential/

Fascinating product that I did not know existed. Am I reading the specs correctly they these only lose about 3/4 a kWh every 24hrs without energy?

I looked into Sunamp last year as they sounded idea for us when redoing our heating. They seem to have had many teething problems, including the control circuit boards having fundamental problems, and people having the battery contents expand and warp the cases.

If you're interested in going that route, have a look at https://www.google.com/search?q=sunamp+review+site:forum.bui...

That heats one 100m² room, doesn't it?

A typical English¹ house has several rooms, and is heated by a central boiler and a pump circulating hot water through radiators.

Converting the house to air-based heating would require several such units, or else some other type of unit and pipes to move the air to the various rooms.

¹ Used intentionally, I know electric resistive heating is/was more common in parts of Scotland.

> That heats one 100m² room, doesn't it?

A lot of both Norwegian and UK homes have open plan main floors.

Just leave all the internal doors open. The average family home in the UK is less than 100 m2 all told. A pair of air to air heat pumps would easily heat the two floors.

And of course the UK really should insulate houses better.

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