Boiler-Heat Pump Hybrids

[SteamyTea]

  On 29/11/2024 at 20:23, sharpener said:

Pumped storage. Air under pressure in underground caverns/salt mines/depleted oil fields.

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Yes.

This is my favourite after thermal storage at point of delivery i.e. in my airing cupboard.

[sharpener]

  On 29/11/2024 at 20:44, SteamyTea said:

Yes.

This is my favourite after thermal storage at point of delivery i.e. in my airing cupboard.

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Just read a feature in the Economist predictions for 2025. To the foregoing list we can add:

 

• Chinese firm HiNa to start industrial production of grid-scale sodium battery technology in 2025. (I remember sodium-sulphur being the great hope for electric cars >30 years ago.)
• US co Form Energy are developing iron-air batteries and
• Italy's Energy Dome uses CO2 under pressure instead of air, both to start construction of US plants next year.

Over-capacity in Chinese EV battery manufacutre means capital cost of solar + batteries now less than new coal plant in China or new gas-fired in US.

 

 

[Beelbeebub]

  On 01/12/2024 at 12:50, sharpener said:

Chinese firm HiNa to start industrial production of grid-scale sodium battery technology in 2025. (I remember sodium-sulphur being the great hope for electric cars >30 years ago.)

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I think these are Sodium ion batteries rather than sodium sulphur. Basically the same tech as Lithium ion but with sodium (it's obviously more complex than that but that's the quick view). The big advantage being that sodium is very much cheaper and more availble than lithium. As a bonus the batteries are apparently longer lasting, less explosive and can withstand discharge to zero (making shipping much safer).

 

There is a company looking at the molten sodium sulphur tech which has some interesting advantages or at least ways of thinking of the disadvantages (primarily the high temps needed) as advantages.

  On 01/12/2024 at 12:50, sharpener said:

US co Form Energy are developing iron-air batteries and

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IIRC these are extremely low energy density on volume and weight but have the advantage of being very cheap per kwh. For long term grid use the space/mass is not a problem.

[SteamyTea]

A look at the periodic table will show why Lithium has become the go metal for storage.

 

If you want cheap, reliable and recyclable, then lead acid works a treat.

Edited December 1, 2024 by SteamyTea

[Beelbeebub]

  On 01/12/2024 at 16:51, SteamyTea said:

A look at the periodic table will show why Lithium has become the go metal for storage.

 

If you want cheap, reliable and recyclable, then lead acid works a treat.

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I don't think the life cycle costs of LA batteries is very good. They tend not to have very many cycles before needing to be replaced.

[SteamyTea]

  On 01/12/2024 at 17:46, Beelbeebub said:

I don't think the life cycle costs of LA batteries is very good.

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I am not sure now, lithium has reduced a lot in price, but a few years ago, they were by far the cheapest.

They are the most mature technology though, well understood, and easily recyclable.

 

Thermal storage is still the cheapest and most reliable.  At 7p/kWh (if you can get that rate) there is price parity with natural gas, with much simpler technology.

[Beelbeebub]

So. I had a gander and found this LA battery setup

 

https://www.photonicuniverse.com/en/catalog/full/359-24kWh-48V-500Ah-AGM-deep-cycle-battery-bank-with-metal-racking-24-x-2V-batteries.html

 

24kwh, £2k

 

Whilst a 9.5kwh Li pack is just over £3k.

 

https://www.green2go.co.uk/givenergy-9-5kwh-lifepo4-unlimited-battery-integrated-dc-breaker-giv-bat9-5.html

 

So game set and match for LA....right? 24kwh for 2k vs only 9.5kwh for £3k.

 

Except the LA has a cycle life of 1200 cycles *at 30% DOD*.  So it's really an 8kwh usable pack ie comparable to the Li pack and is only warranted for  1200 cycles/1 year, about 4 years daily use.

 

The Li pack has an unlimited /12y warranty.

 

So over the 12 years of the Li pack you will have had to buy 3 LA packs or £6k.

 

LA's have had over a century to get cheaper and better. They are currently pretty much at their peak cost/performance point - plus they are made in vast volumes so there isn't much scope for reducing manufacturing costs.

 

Li batteries and their cousins like Sodium ion are only at the start of thier development cycle. Volumes are still increasing, performance is still improving.

 

 

I looked into solar PV 15 years ago when building my old house. And ran up against the battery issue. I couldnt find a way to make it work. So I went with solar thermal.

 

Now it would be easy to sort out a battery PV system.

[sharpener]

  On 01/12/2024 at 15:08, Beelbeebub said:

I think these are Sodium ion batteries rather than sodium sulphur.

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  On 01/12/2024 at 15:08, Beelbeebub said:

There is a company looking at the molten sodium sulphur tech which has some interesting advantages or at least ways of thinking of the disadvantages (primarily the high temps needed) as advantages.

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Yes. The sodium-sulphur chemistry had the extreme disadvantage for EVs (as we now call them) that if you don't/can't maintain them hot enough to keep the sulphur molten they are completely bricked.

 

For completeness I should have mentioned the bromine-based flow batteries, which I like as a technology as the dimensions of power (size of flow cell) and energy (size of tanks) are determined quite separately.

[SteamyTea]

  On 01/12/2024 at 20:54, Beelbeebub said:

So. I had a gander and found this LA battery setup

 

https://www.photonicuniverse.com/en/catalog/full/359-24kWh-48V-500Ah-AGM-deep-cycle-battery-bank-with-metal-racking-24-x-2V-batteries.html

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Brilliant.  Well worth knowing.

There was a program on the World Service the other night about this, but I fell back to sleep during it.

[Beelbeebub]

  On 02/12/2024 at 00:16, sharpener said:

Yes. The sodium-sulphur chemistry had the extreme disadvantage for EVs (as we now call them) that if you don't/can't maintain them hot enough to keep the sulphur molten they are completely bricked.

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The newer versions are interesting. They imply that if they go cold they simply stop working until they are reheated. Essentially go into hibernation.

 

They also reframed the high (250-300c from memory) operating temp. Yes that's hot, but no hotter (cooler even) than temps encountered in an internal combustion engine. They use modern insulation materials to keep the heat in. 

 

But they also claim advantages to such high temps. Firstly, given all normal environmental temps are well below the operating temp the battery doesn't really notice the difference operating in 50C desert.  Secondly the high temps mean dissapating the waste heat from internal resistance (charging and discharging) can be done with an emitter at 250-300c.  Whereas a normal battery has to dissipate a few Kw at 40C.  So the molten battery can use simple air cooling with a variable speed fan and a much smaller airflow.

 

Whether or not anything comes of it, I thought it was an interesting alternative approach.

[Beelbeebub]

  On 02/12/2024 at 04:57, SteamyTea said:

Brilliant.  Well worth knowing.

There was a program on the World Service the other night about this, but I fell back to sleep during it.

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A occupational hazard listening to the world service 😁

[JohnMo]

So based on a topic by @Beelbeebub I have been playing with my system and in the most part trying to get a system not connected in any part to the internet. This is now in place. No internet connectivity to anything that controls, but do some internet monitoring.

 

Have used a wiring centre, with lots of good features. It has a wireless outdoor sensor, can do Opentherm WC for boiler control, also has volt free NO and NC contacts, maybe able to use these to allow heat pump to run or stop it running - needs some thought. You can set an outside temperature threshold for the boiler to come on, so if average temp above X degs boiler is not started.

 

It has wired/wireless room sensors (not thermostats), the wiring centre can then be set with schedules and individual room hysterisis and target temperature. It can do cooling control based on humidity thresholds etc.

 

The controller I purchased is branded Polypipe, but also marketed by several others including Roth, but think made by Tech Controllers. The one I am using is being sold on eBay and was never formally released on sale. Bit to complex for the UK market, I suspect.

 

I have no actuators in the system, so it's all a single zone. Each room will have a sensor, but only two will be utilised for boiler control kone in hall and other in kitchen). So either can call for heat, both off to stop heat.

 

Running WC mode via Opentherm, and have an outside temperature threshold for the boiler to heating based on 5 degs averaged over 24 hours (this setting will need fine tuning). Heat pump settings or controls are not changed. Have found the heat pump runs only as needed.

 

Room sensors were £11, plus a Roth sensor with humidity £49

Wiring centre £149

Purchased a remote display/controller also (not needed) £49

Wireless outside sensor (no holes in the walls) £29.

 

 

Room sensor

 

Remote monitor - only two room connected at the moment.

 

 

[Beelbeebub]

Very interesting. 

 

Is there any data logging facility? 

 

You mentioned you don't have any actuators, does it have the facility for zones? Can it handle hot water production? 

 

 

[JohnMo]

  On 18/01/2025 at 10:42, Beelbeebub said:

Is there any data logging facility

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Yes you can get an internet module for remote control, logging etc.

 

 

  On 18/01/2025 at 10:42, Beelbeebub said:

You mentioned you don't have any actuators, does it have the facility for zones? Can it handle hot water production

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Yes this unit does 8 zones, 4 loop actuators per zone, directly and also allocate loads of additional ones from other zones if you want. It can also communicate to loads of slave controllers, think it can do 48 zones.

 

Yes has hot water timer and uses zone 8 for this, has a 230v output. May do this at some point.

[Beelbeebub]

  On 18/01/2025 at 10:52, JohnMo said:

Yes you can get an internet module for remote control, logging etc.

 

 

Yes this unit does 8 zones, 4 loop actuators per zone, directly and also allocate loads of additional ones from other zones if you want. It can also communicate to loads of slave controllers, think it can do 48 zones.

 

Yes has hot water timer and uses zone 8 for this, has a 230v output. May do this at some point.

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Thats impressive. 

 

Do you have any links? 

[JohnMo]

The wiring centre I bought

 

https://www.ebay.co.uk/itm/315153782771?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=KzwJTGtMQAi&sssrc=4429486&ssuid=8KgwDlAbTJS&var=&widget_ver=artemis&media=EMAIL

 

Same seller has the remote screen listed also.

 

Sensors

https://www.ebay.co.uk/itm/267046429821?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=grAjxs1RQGq&sssrc=4429486&ssuid=8KgwDl

 

Other units similar but different based on the same package 

 

Roth 

https://www.roth-uk.com/products/control-systems/roth-touchliner-sl-wireless-system

 

Other seller, think it's the maker but not sure

 

  On 18/01/2025 at 10:17, JohnMo said:

https://tech-controllers.com/k/floor-heating-controllers Controllers

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[Roger440]

  On 18/01/2025 at 10:17, JohnMo said:

So based on a topic by @Beelbeebub I have been playing with my system and in the most part trying to get a system not connected in any part to the internet. This is now in place. No internet connectivity to anything that controls, but do some internet monitoring.

 

Have used a wiring centre, with lots of good features. It has a wireless outdoor sensor, can do Opentherm WC for boiler control, also has volt free NO and NC contacts, maybe able to use these to allow heat pump to run or stop it running - needs some thought. You can set an outside temperature threshold for the boiler to come on, so if average temp above X degs boiler is not started.

 

It has wired/wireless room sensors (not thermostats), the wiring centre can then be set with schedules and individual room hysterisis and target temperature. It can do cooling control based on humidity thresholds etc.

 

The controller I purchased is branded Polypipe, but also marketed by several others including Roth, but think made by Tech Controllers. The one I am using is being sold on eBay and was never formally released on sale. Bit to complex for the UK market, I suspect.

 

I have no actuators in the system, so it's all a single zone. Each room will have a sensor, but only two will be utilised for boiler control kone in hall and other in kitchen). So either can call for heat, both off to stop heat.

 

Running WC mode via Opentherm, and have an outside temperature threshold for the boiler to heating based on 5 degs averaged over 24 hours (this setting will need fine tuning). Heat pump settings or controls are not changed. Have found the heat pump runs only as needed.

 

Room sensors were £11, plus a Roth sensor with humidity £49

Wiring centre £149

Purchased a remote display/controller also (not needed) £49

Wireless outside sensor (no holes in the walls) £29.

 

 

Room sensor

 

Remote monitor - only two room connected at the moment.

 

 

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Good stuff.

 

Keeping the internet away from systems in the house is key for me.

 

Have you ever posted a schematic or similar of your complete set up? Id love to get my head round it, as you seem to have all the sensible things i consider important, without needless crap.

 

 

[JohnMo]

  On 18/01/2025 at 22:57, Roger440 said:

Have you ever posted a schematic

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I have but I need to update it, which I can do hopefully today or tomorrow. Will post it up.

[JohnMo]

@Roger440

 

Sorry for the delay forgot all about the schematic.

 

Seems to work well

5 degs and below for at least 6 hrs, is needed to allow the boiler to run. All other times ASHP runs.  ASHP set up via Home Assistant to take excess PV when battery is above a set charge and generating enough PV to get a decent run time. Past few weeks nearly all heat pump running has been on excess PV - so zero cost, boiler had no need to start because house was warm enough.

 

No excess solar yesterday and down to 1 deg overnight. Heat pump ran for about 2 hours and the at first defrost, the boiler picked up the drop in flow temperature and started up, it did the rest of the heating overnight.

Heating Layout and Control.xlsxFetching info...

[JamesPa]

Like it.  No system separation for the heat pump, only for the boiler, max efficiency.  Why cant installers think like this? (rhetorical question)

 

is the boiler used to reduce cost or because the heat pump does not have sufficient capacity?

[JohnMo]

  On 24/03/2025 at 09:15, JamesPa said:

is the boiler used to reduce cost or because the heat pump does not have sufficient capacity?

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More an experiment to see what I could do with a boiler, that was almost new and just sitting there - not wanting to give it away, really.

 

5 degs was the lowest temp I could set the controller to to enable heating.  But we aren't that far from the coast and can get defrosting at about 5 degs.

 

When we get defrosting CoP drops to about 3.  We pay 13p overnight, so about 4.3p per kWh (0030 to 0730), gas is 5p and not quite 100% efficient, so pretty much like for like pricing. But once a sustained below zero the heat pump runs in the expensive period (0730 to 0030) at 30p, so getting towards twice the price for electric, compared to gas for the same kWh delivered.

 

So overall a little cheaper, but not much - if I had to pay for hybrid system not really worth it.

[marshian]

Great work - I like that idea a lot

[JohnMo]

Today has solar excess so floor is being buffered from heat pump. So unlikely any additional heat will be needed overnight.

 

Average heating cop is 4.47, but as day temp increases, the CoP also goes up even with rising flow temp.

 

[Roger440]

  On 24/03/2025 at 09:06, JohnMo said:

@Roger440

 

Sorry for the delay forgot all about the schematic.

 

Seems to work well

5 degs and below for at least 6 hrs, is needed to allow the boiler to run. All other times ASHP runs.  ASHP set up via Home Assistant to take excess PV when battery is above a set charge and generating enough PV to get a decent run time. Past few weeks nearly all heat pump running has been on excess PV - so zero cost, boiler had no need to start because house was warm enough.

 

No excess solar yesterday and down to 1 deg overnight. Heat pump ran for about 2 hours and the at first defrost, the boiler picked up the drop in flow temperature and started up, it did the rest of the heating overnight.

Heating Layout and Control.xlsx 23.24 kB · 7 downloads

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Excellent. Much appreciated.

 

Some questions.

 

What is POD?

What is CCT?

You say the ASHP is set up to use the excess PV. How is that actually done? Is it a off the shelf device, or something you sorted out yourself?

 

[JohnMo]

Pod - my summer house (heated all year)

 

CCT - close coupled tee

 

  On 24/03/2025 at 19:59, Roger440 said:

You say the ASHP is set up to use the excess PV. How is that actually done?

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ASHP, can run two temperatures, set via a zero volt contact.

 

Shelly relay is used to switch between the two settings.

 

Shelly control is via home assistant, it monitors battery state of charge and PV output. So if battery state of charge is above 97% and PV is generating more than 600W, ASHP runs and stays running until battery drops to 95%. Have a similar setup for the immersion. Idea is I never let battery get to 100% charged and export little or no electricity.