How much energy does a condensing boiler save? is it worth worrying about?

[Gasplumber]

My view lol condensing boilers ain’t worth nothing if the it’s not actually condensing.
Although lack of servicing usually means an emergency call out to clean out a condense

I’d still rather have a old heat only without a thermostat just set low on boiler stat all day

 

[John D v2.0]

Do you have a plume at the terminal? If so you are not harvesting all the latent heat. The latent heat amounts to 0.93KW/cu m and the EU reckons you're lucky to get around 0.4kw of that if your return is 41 degrees.

Controls may modulate the boiler flow and of course return which if low enough provides the opportunity for condensation on the exchanger surface but this only happens if enough sensible heat has been removed first. e.g the return enters the boiler at 40 but one exchanger may have 2% of it's surface at that low temperature a better exchanger 5%.

Indeed although unless you get the flow exhaust back to the equivalent temperature and humidity that they entered then there's some energy being lost out the flue.
Perhaps eventually we will have flue gas heat pumps to warm the intake air, but if you had the space, a large flue heat exchanger would probably be more economical.

 

[ericmark]

Seem to remember some boilers had a Sterling engine generator running on the flue gas heat.

 

[hard-work]

Seem to remember some boilers had a Sterling engine generator running on the flue gas heat.

Navien do one:
Navien Hybrigen SE
https://navienuk.com/products/hybrigen-se/
The integral Stirling engine generates 1KW of electricity. The average house needs around 800w. £6,000 to buy, but 25% lees than Viessmann.

Here is a moving cutaway of the Stirling engine.

Viessmann also do a Stirling boiler:
https://www.viessmann.co.uk/products/combined-heat-and-power

 

[hard-work]

If you had solar PV panels on the roof coupled to a Tesla Powerwall battery, I doubt you would need a Stirling boiler. But a Stirling in flats looks a good way to go. Problem is payback time. The bigger the property and the more it is used the quicker the payback. With these Stirling boilers you sell electricity to the grid when you do not use it.

 

[JohnD]

If you had solar PV panels on the roof coupled to a Tesla Powerwall battery....

Then you would be a person who does not understand cost/benefit analysis or DCF.

Or maybe just a person who likes tipping money down the drain.

 

[hard-work]

Then you would be a person who does not understand cost/benefit analysis or DCF.

Or maybe I do. Soon gas boilers will be outlawed in new builds, It is going all electric - which I welcome. Get used to it.

The Powerwall:

 

[ericmark]

You will note that link was in my last post to Navien when my son was living on a narrow boat we looked at the Whispergen also a Stirling engine. The whole idea of combining electric generation and heating is rather old, I remember visiting a farm in Tywyn in Mid Wales where the generator had been in a shed across the drive from house, and the cooling water also heated the house, electric was DC I would guess 110 volt with a bank of batteries in the house cellar, however is with oil central heating fuel had to be delivered, and it was noisy.

The alternative technology centre built a house with very thick walls, been years since I have been there, seem to remember made of straw bails, but 2 foot thick walls are not really practical, and today most the ecology ideas are only viable if there is some government grant.

The interest rate means in the main pay back has to be 25 years or less, after 25 years the interest means not worth considering, and even our best power stations we are only looking at 25 years life, there are a few, as well as Dinorwig Power Station there is Maentwrog the oldest hydroelectric power station in Snowdonia, built 1928 but these are unusual.

And the same applied to power in the home, 25 years is tops for any pay back, and although my old gas boilers are some 40 years old, I don't think the new gas boilers will last that long, so really most people want a pay back in 5 years not 25 years, can't really get a mortgage on the boiler.

But the government sticking their finger in can so easy mess things up, if things start to improve gradually if there is some unforeseen problem we find out before it is done too much, but when you have all new build houses with zone valves and no real idea on how to control boilers with just two zones by it seems the house designers, all they seem to want is a tick in the boxes, the system does not need to work, and national campaigns on how to control your home from your phone.

I can see the point in the heating turning off when you both leave the house, and turning back on when either of you return, but I don't want to have to get the phone out as shown in the advert, I want it automatic, (geofencing and occupancy detection) but it needs that occupancy detection, picking up grandchildren from school and taking them to a cold house, and having to phone their dad at work so he can turn heating on is not an advance to simple times, they finish school same time every day, no need for all the phone rubbish. I can just see the school teacher when she finds the kids have smart phones so central heating will work?

 

[denso13]

Then you would be a person who does not understand cost/benefit analysis or DCF.

Hey John, you're the one saving almost £170 per annum with your new boiler. That would payback the outlay for solar panels and a powerwall in about 70 years, what's not to like?

 

[denso13]

You are also not very good a sums either.

You're right, given servicing and life cycle replacements it's probably much longer than that.

 

[JohnD]

I have calculated cost and benefit of a powerwall. It has a negative return for me.

So, incidentally, does an Immersun.

 

[hard-work]

Amazing, these people say it is feasible. One with no PV panels as well:

"What I have seen of his figures, we can confidently say the system works".

 

[hard-work]

Is a Tesla Powerwall 2 Worth the Money?

 

[hard-work]

Once Powerwall batteries drop in price, with others making them, a few do, they will be everywhere. New builds designed for them and solar PVs will be cheap to build over a PV retrofit.

A Powerwall battery can be fitted in a hall cupboard in a flat.

 

[hard-work]

ericmark, The alternative technology centre built houses that needed no heating or cooling with little, or no, technology involved in heating or cooling them - natural homes. They way to go. But as the UK is backwards in many respects, we have the oldest housing stock in western Europe, insulation can only go so far in our crumbling, full of air leaks rabbit hutches. So, Powerwalls, PV panels, heat pumps, etc, then become feasible.

An Intergas gas boiler will last 25 years at least. Fit it properly, with a decent system, with regular servicing, then it will last and last. If you want the heating to turn on and off as you go in and out the front door, then photo cells can do that. They also work well with secondary circulation pumps.