What is the going cost for boiler replacement these days

[jimmy_s]

Mike

I agree, I have argued with clients on this point and have walked away from projects where they wouldn't listen, but ASHP's do seem to be getting better.
The COP depends ultimately on the suction and discharge pressures that the compressor has to work against and also the thermodynamic properties of the refrigerant. I am waiting on the proper info on the new Vaillant R290 (propane) ASHP but on paper it looks pretty decent.

 

[Just4Fun]

When you realise that electricity is typically generated with an efficiency in the low 30% range ...

That applies in the UK, but not everywhere. Combined heat & power (CHP) plants here in Finland typically run at over 80% efficiency. Maybe the UK should bite the bullet and invest in that approach. Expensive to retrofit now but in the long term it could pay off.

The housing estate in the UK where I grew up had all the roads dug up last summer to fit fibre optic cables. Then in the autumn they were dug up again to renew the gas mains. Why couldn't these have been combined and, at the same time, have pipework for a district heating system installed? The additional cost would have been a cheaper way of providing that infrastructure to be ready for replacing individual gas boilers in each home.

 

[D_W]

......The SCOP of the newer air source heat pumps are a lot better than they used to be.......

Claimed figures and actual in-use figures are very much like claimed MPG figures for cars. Real life COP figures of 2 are rare. When you realise that electricity is typically generated with an efficiency in the low 30% range, and with losses in the distribution the energy efficiency of the electrickery which actually arrives in your house is typically in the 25% to 30% range. It doesn't take a second on the back of an envelope to work out that in energy terms you would be way better off burning the oil or gas directly in your house in a modern efficient condensing boiler (efficiency, depending on how it is calculated, of 80%+........with claimed 95% + being worth another pinch of salt) than you would going the circuitous and inefficient route of burning it in a power station, converting that heat to steam to generate electricity to send miles down the wires where it is converted back into heat.

Of course, if all our power came from renewables, and there was capacity in the distribution system, then heating by electricity would be fine, despite its enormous inefficiencies. It doesn't, so it isn't.

here in the states (comment withstanding again about particulates), california is going so far as to get nat gas appliances out of circulation (dryers, cooktops/ovens, etc) for a simple reason - they're trying to control emissions of unburned gas and get everyone on grid as generation changes.

When you talk about something like oil instead of natural gas-generated electricity, you have to include the fact that there's quite a lot of energy spent in faffing about with the oil (probably so than there would be if you were burning gasoline in a car). And there's a quite a bit of filth released burning oil compared to natural gas.

What the energy company does to generate a converted BTU of electricity will be at far less cost than you burning oil, and the idea that you're burning a btu and 0.95 of it goes into your living space is a bit funny (and if it does exist, it erodes as the equipment gets old).

We burn gas here for heat. I pay about double the amount that the power generation company does. If I burned oil, i'd be done burning oil at this point and go to a geothermal system for one simple reason. a 100% efficient electrical coil probably has about 3.5 EER. with an ambient outdoor temperature of 45 degrees F (probably about 8C), the system uses one kilowatt to generate 21,500 btu of heat. You can pencil that out. It's probably more efficient to exchange heat with the outside air (which is where most of the heat is coming from) than it is to burn fuel and transfer the heat from the burning through your system.

The case where I'm not peeing into the breeze here with natural gas is that it gets much colder here than there. below 0F at night several times a year. The only thing that makes that swing efficiency wise is geothermal, where you get the favorable equivalent of the heat exchange mentioned above all the time because the exchange is going on with the ground. The trouble is, a 5k heat pump install (if you had such a thing air to air) becomes about 15k here in the states and it doesn't pencil out yet with nat gas. It does with oil (keeping in mind that we will spend more btus per square foot because our average fall and winter temperature will be lower than probably anything in the UK, and definitely lower than much of it).

The overall EER rating (vs. seer) of my 21 SEER system is about 14 or 15 (I don't remember exactly, but it's one of those). If we hit that target on the heat side, we're still as efficient or more efficient than your oil burner 14*0.25 vs. 3.5*0.9 or so). With less particulate in the air by a long shot.

 

[jimmy_s]

DW, yes I would think for you guys where the external ambient drops considerably ASHP are not an option and GSHP are the only way to go. In order to get a decent COP you will need a decent ground collector heat absorbtion rate either by having a large ground loop which is essentilally a large solar absorber or a number of boreholes. In the UK these have often been undersized resulting in poor COP's. Its always been hard to justify heat pumps here if nat gas is available financially (not carbon emissions) but against oil it often works out better. I've never been that keen on air source unless in areas such as Shetland where the weather is rough but low temperatures are rare (providing the coils are treated for salt spray). But I like to keep an open mind and think they are getting better for the UK climate.

 

[jimmy_s]

Just4fun - yes very little large scale CHP schemes over here - a few combined gas turbine/ steam jobs but not that many. We do a few small scale localised CHP schemes. Very few with gas turbines, mostly IC engines - have done some off grid CHP but generally small scale using natural gas or LPG. Looked at gassification and biogas feeds from mesaphilic and thermophilic AD plant but its difficult to get these funded. Larger scale wind power has been popular and battery storage systems also. Been looking at some unusual (to me anyway) battery sytems (sulfur/sodium). Molten sodium is not the best though!

 

[D_W]

DW, yes I would think for you guys where the external ambient drops considerably ASHP are not an option and GSHP are the only way to go. In order to get a decent COP you will need a decent ground collector heat absorbtion rate either by having a large ground loop which is essentilally a large solar absorber or a number of boreholes. In the UK these have often been undersized resulting in poor COP's. Its always been hard to justify heat pumps here if nat gas is available financially (not carbon emissions) but against oil it often works out better. I've never been that keen on air source unless in areas such as Shetland where the weather is rough but low temperatures are rare (providing the coils are treated for salt spray). But I like to keep an open mind and think they are getting better for the UK climate.

air source are sold here (whole house) in developments where natural gas isn't available. Usually ASHP, propane and GSHP. Propane is sort of a racket and a very expensive way to heat here. Older houses often have oil, but new builds don't generally (I guess because of the plumbing ...who know , oil here is generally water circulation through the entire house. Only popular in floors at this point). I guess the people who get air source are just paying a large bill in the winter - don't know. As you say, natural gas is available where I am and I doubt there's anyone in my township not burning it. Trees fall here in the woods and rot. I've only seen one person in the last 10 years hauling firewood (he's heating a large freestanding garage).

 

[jimmy_s]

DW - it sounds about the same in the UK. Propane for most is very expensive. One of the exceptions are caravan parks, who seem to be able to buy it for similar costs to natural gas and can make propane fired CHP work financially.

I am interested to see how we get on with the hydrogen. I once worked on the main UK gas boosting network where they they meter the gas entering the country and control the gas boosters etc throughout the UK. I seem to recall that sections of the network were humidified as the joints in the pipes leaked if the gas was too dry. Not sure how thats going to work with hydrogen injection. I'd think there's going to have to be a lot of investment before it gets off the ground.