Using solar (and attached direct) cylinders as heat stores

[GregKaye]

Hi, this is all at the stage of considering theoretical possibilities but I'd really appreciate comments and guidance on the workabilities of the ideas proposed:
(multistage diagram then explanation):

(if that didn't work try this: Imgur).

One positive with the ecological movement for many of you guys is that it may bring in a lot more work into plumbing trades. Many ecological groups are saying one of the most effective ways of keeping within renewable provision (via, heatpumps and hydrogen and biogas boilers) is to store heat in between times when provision is high and within times when the wind stops blowing.
Many have also recognised that water is a great resource for holding heat.
The diagrams represent my best attempt so far to show how this might happen. The solar cylinder is used because it has two coils.
Are there products on the market that have three coils?
If there are two tanks, one for summer and the other added for winter, how could the relationship between the tanks work? At what beneficial heights on solar cylinders are there outlets and how could these outlets best fit in with a parallel cylinder and radiators etc? Would additional pumps be required?
You'll be well aware of the heat capacity of water and I doubt you've got great affection for ice. The heat pump idea tries to tap into the latent heat of water (which gives off an energy equivalent to the energy in water that's 79.5° above ambient heat.
Renwable energy providers may begin giving cheaper rates when their production levels are high so it would be great to find systems that can fit.
Cheers.

 

[ShaunCorbs]

TBH solar isn’t a diy install I would get an approved company in to design what you want and install

 

[GregKaye]

TBH solar isn’t a diy install I would get an approved company in to design what you want and install

Thanks and yes - its definitely not a job for me. This is more looking at the kind of new developments that councils might support. It's a concept that I'm trying to explore.

 

[SimonG]

Looks like ball cocks to me.

The wheel is still round, worked for quite a while.

If your serious get a renewables company in and pay them to create your heating and hot water system.

 

[SimonG]

Damn autocorrect

 

[GregKaye]

Looks like ball cocks to me.

The wheel is still round, worked for quite a while.

If your serious get a renewables company in and pay them to create your heating and hot water system.

What are your criticisms of it?
If you can find me a renewables company that can show how the heat stored in water can be later used for heating I'd be grateful.
Thanks.

 

[gmartine]

I'd go for a battery array to store all that gym work. 😉

 

[GregKaye]

I'd go for a battery array to store all that gym work. 😉

Each to their own 🙂
I'm looking at people who don't want to use energy at times when renewables aren't producing it and who also don't want to get cold.😕

 

[GregKaye]

It would also be great to get msg comments if people don't want to reply here.

 

[ShaunCorbs]

Each to their own 🙂
I'm looking at people who don't want to use energy at times when renewables aren't producing it and who also don't want to get cold.😕

So your looking to sell an idea ?

 

[GregKaye]

So your looking to sell an idea ?

Trying to save the world. 🙂

 

[ShaunCorbs]

Trying to save the world. 🙂

Time to pay the pros to design something for you to pitch then

 

[gmartine]

Each to their own 🙂
I'm looking at people who don't want to use energy at times when renewables aren't producing it and who also don't want to get cold.😕

How do you intend powering the heat pump when no-ones in the gym?

 

[GregKaye]

Time to pay the pros to design something for you to pitch then

A scheme to use hot water as a heat store would be great. Any suggestions from the pros here???

 

[GregKaye]

A scheme to use hot water as a heat store would be great. Any suggestions from the pros here???

If you are saying that storing heat in water for later use in heating then fine. Why? What is wrong with the idea? If you are saying that there is a problem with the execution, what?
You're pros.
Can you please specify what the issue is?
Thank-you.

 

[ShaunCorbs]

A scheme to use hot water as a heat store would be great. Any suggestions from the pros here???

Nope

 

[Sharp Point]

hi Greg, I totally get your idea and it does have legs. You won’t get much from most on here, they’ve been doctrinated into following the rule book. I like how you’re looking outside the box and hope you can get it going.
Try this place, I use to frequent it for years and brushed up my renewable knowledge prior to specialising in solar.

Navitron Renewable Energy and Sustainability Forum - Index

Good luck

 

[Sharp Point]

So you’re trying to build an inter-seasonal thermal store?
You’ll see some on that forum, that are behemoth and buried in the ground with differing types of heat exchangers to heat ufh/ rads/ greenhouses

And hot water.

 

[GregKaye]

hi Greg, I totally get your idea and it does have legs. You won’t get much from most on here, they’ve been doctrinated into following the rule book. I like how you’re looking outside the box and hope you can get it going.
Try this place, I use to frequent it for years and brushed up my renewable knowledge prior to specialising in solar.

Navitron Renewable Energy and Sustainability Forum - Index

Good luck

Thank-you. I also asked a question in a different thread about buffer tanks.
Another ideas is to reign back abit on the difference of my idea above. I got to thinking that maybe the boilers could be directly connected to the boiler/heater/heat pump but on the heater side, to have a loop from the cold and the hot going somewhere else hot such as in the solar cylinder. Maybe some kind of valve might be able to shift flow into the cylinder when it's decided to stand the heater down.
I see a problem, not stated by the "pros", that the radiators are getting heat second hand. Maybe there are ways around that.

 

[GregKaye]

So you’re trying to build an inter-seasonal thermal store?
You’ll see some on that forum, that are behemoth and buried in the ground with differing types of heat exchangers to heat ufh/ rads/ greenhouses

And hot water.

To start with I'm just looking for something that will stop things getting cold within a few hour on a winters day.
Heat pumps? They'd still need one unit of electric for every 4 units of heat delivered. One time last year the direct contribution of renewables to total UK consumption fell beneath 1%. I'm looking for options to totally stop all but the most minimal of power consumption.

 

[chris watkins]

Water as a storage medium is good but not good enough I am afraid, you would just need to store to much of it.
They are looking at gas to liquid (& back) systems as I understand it, as changing state you can store much more.

 

[Sparkgap]

Looks similar to a wet (heating only) system I installed years ago at an outdoor centre. Place was off-grid and previously relied on a generator which had been replaced by a wind turbine and solar PV feeding battery storage & inverters with the genny as backup. Existing turbine controls dumped excess energy into a large resistor heating up the locality once the batteries were charged. We fitted a 1000L buffer tank with 4kW immersion heaters (8x500W) switched by the existing controls so instead of wasting energy it was used to preheat the tank. Heating was weather compensated with 3-way valve. According to the site manager the boiler hardly ran at times in spring and autumn.
Water might not be the best material for thermal storage but it's the easiest to install without getting expensive.

 

[OffshoreGas]

Hi Greg,

The problem with your idea of storing energy as heat is basic thermodynamics and efficiencies.

No process is 100% efficient, every time you convert one form of energy to another there are losses, think of your car for example. You put fuel in the tank and want to convert it to movement, but you also get waste energy such as heat/noise. Your proposed system has lots of heat exchanges which would be inefficient.

The other problem is heat loss, if you stand a cup of tea on your desk it would cool in say 2 hrs to be the same temperature as the room. If you store hot water in a tank you've got the same problem. You can add insulation it suffers from diminishing returns, the first 50mm may reduce heat flow by 75% but if you want to reduce it by another 15% you may have to have 20mm of insulation.

Litium ion batteries work well for energy storage in the medium term due to low self discharge. This may be worth looking at instead of heat?

 

[oz-plumber]

The solar on the system you have shown will have very minimal impact on heating the cylinder.
Generally the solar pump will only switch on when the temperature of the water in the collectors is 2 degrees above the stored water temperature in the cylinder.
It may come on in winter, but it will be switching on and off all the time.
As for running the radiator panels off a coil in the cylinder, that would also be very hit and miss also.

You could introduce more refrigeration principles into your desired system, but as soon as you introduce refrigeration ( heat pump ) systems, costs start exploding.

I understand what you are trying to do, I have been looking into environmental system for years - can't find anything that will return the outlay before some of the system components die.
eg: 10 years - you would never see a financial benefit out of installing the system

 

[Stigster]

If you are saying that storing heat in water for later use in heating then fine. Why? What is wrong with the idea? If you are saying that there is a problem with the execution, what?
You're pros.
Can you please specify what the issue is?
Thank-you.

Long post alert!

Here in Guernsey a local company used make a product called Ecostor. They are no longer available after they never achieved popularity and had some performance issues in day to day use.

It was a large unvented cylinder with a six kilowatt immersion, a coil for connecting either an oil boiler or heat pump and a second coil for solar. There was a heat exchanger mounted on the outside of the unit to provide hot water. The cylinder was heated by the solar coil when conditions were right with the immersion as a backup and also as I mentioned connected to a boiler or heat pump.

The water in the cylinder was not what came out of your taps, but rather a thermal store. This stored water was pumped both through the heat exchanger for on demand hot water and through the rads to do the central heating.

The problem was that you more or less had to choose whether you have a warm house or hot water. If you came home from work and put the heating on, good luck getting enough hot water for a family to use in the evening as the heat was lost too quickly to the room heating. Likewise, long showers or big baths would deplete the heat store and your heating would not perform adequately. If used very carefully and in a specific way with timings it would work. Likewise for very small properties like flats, it worked ok.

There was never enough stored heat to do both jobs and the immersions ended up being used most of the time which kind of defeated the purpose of the system. Sorry for the long post but these things were never liked here and are no longer available as far as I know. I've got one here in the workshop as a demo model but I've just finished ripping it out as our apprentices really don't work on them enough to dedicate the space any longer.

 

[chris watkins]

Thermal stores are still available & still have there place but as said before the amount of hot water (heat energy) you would need to store to provide for domestic heating & HW often means they are impractical.

 

[Sharp Point]

Great products, in behemoth sizes. Akvaterm thermal stores.

:: In English

 

[GregKaye]

Long post alert!

Here in Guernsey a local company used make a product called Ecostor. They are no longer available after they never achieved popularity and had some performance issues in day to day use.

It was a large unvented cylinder with a six kilowatt immersion, a coil for connecting either an oil boiler or heat pump and a second coil for solar. There was a heat exchanger mounted on the outside of the unit to provide hot water. The cylinder was heated by the solar coil when conditions were right with the immersion as a backup and also as I mentioned connected to a boiler or heat pump.

The water in the cylinder was not what came out of your taps, but rather a thermal store. This stored water was pumped both through the heat exchanger for on demand hot water and through the rads to do the central heating.

The problem was that you more or less had to choose whether you have a warm house or hot water. If you came home from work and put the heating on, good luck getting enough hot water for a family to use in the evening as the heat was lost too quickly to the room heating. Likewise, long showers or big baths would deplete the heat store and your heating would not perform adequately. If used very carefully and in a specific way with timings it would work. Likewise for very small properties like flats, it worked ok.

There was never enough stored heat to do both jobs and the immersions ended up being used most of the time which kind of defeated the purpose of the system. Sorry for the long post but these things were never liked here and are no longer available as far as I know. I've got one here in the workshop as a demo model but I've just finished ripping it out as our apprentices really don't work on them enough to dedicate the space any longer.

I'd imagine the people developing it thought this will change everything. At this stage I think things like some buffer tank use and use of thermal stores are mainly for people with real ecological commitment.
I'd imagine that a conventional design of system with one of those devices added in would work.
If people actually stopped using energy when renewables were in short supply then the government might think again about all its expensive non renewable investment.
Thanks for th einfo

 

[Welder]

So you’re trying to build an inter-seasonal thermal store?
You’ll see some on that forum, that are behemoth and buried in the ground with differing types of heat exchangers to heat ufh/ rads/ greenhouses

And hot water.

THere are plenty of people who are doing similar things. One thing I would say to you now is that having pressurised solar panels is a nightmare. THere are plenty of examples now of open vented solar systems are they prove far more reliable than closed systems. Google a guy called Eric Hawkins (he's on Twitter I know). He'll be a good resource as he has an open vented heat recovery system for cooling PV panels so they are more effecient.

 

[chris watkins]

Dave, can I ask why they are a problem & are we talking about directly filled or heat pipes?
I teach solar but must confess haven't got a much practical experience, so always interested.

 

[Sharp Point]

Yes, why are they problematic?

 

[Welder]

Dave, can I ask why they are a problem & are we talking about directly filled or heat pipes?
I teach solar but must confess haven't got a much practical experience, so always interested.

My honest answer is I dont know. My experience of solar has only been to ultimately rip em out as they have leaked like sieves. Three instances of calling designers/maintainers back to check, service & refill again and again. Custs all got fed up & ripped em out (including p1ss poorly insulated thermal stores) and instead put in well insulated & controlled UVCs. Last one has halved her gas bill.

From what I know, the pressurisation is a pivotal problem. Ive had vessels fail so they obvs cause leaks as systems go mental. Ive heard vessels don't last too long in such agressive & hostile environs. Thinking about it, no std rubber diaphragm will stand 120c for too long and each was a std htg type vessel.

 

[Welder]

Thermal stores are still available & still have there place but as said before the amount of hot water (heat energy) you would need to store to provide for domestic heating & HW often means they are impractical.

Remember water is actually a rubbish medium for heat transfer as it's shc is so high. We'd be better off using a different medium but it'd be more expensive and less 'simple' to service.

 

[Sharp Point]

Thinking about it, no std rubber diaphragm will stand 120c for too long and each was a std htg type vessel.

If the vessel was installed in a non stagnation area, the vessel would see no more heat than a standard vessel. Poor installers screwing it up for the customer

 

[Welder]

If the vessel was installed in a non stagnation area, the vessel would see no more heat than a standard vessel. Poor installers screwing it up for the customer

What's a non stagnation area? #IgnoranceIsBliss

 

[Sharp Point]

What's a non stagnation area? #IgnoranceIsBliss

Lol, I’m sure I don’t need to tell you😉

 

[chris watkins]

Or use intermediate vessel, but it is more likely no maintenance on the vessel caused problems.

 

[Welder]

Lol, I’m sure I don’t need to tell you😉

Oh yes you do - please.

 

[Welder]

Or use intermediate vessel, but it is more likely no maintenance on the vessel caused problems.

Thing is, with an open vented system there are no vessels to cause those problems! Regardless, even for systems just ten years old the energy they consumed via their thermal store aspect was simply huge as they were all so poorly controlled.

I do see the benefit of solar but I'd never entertain a thermal store neither would I entertain a sealed/pressurised system. Of course what I do not understand is how one would 'lose' the heat if it wasn't a thermal store. Perhaps it needs to be, is a bigger metalic thermal mass heated using solar but designed more like nuclear fuel rods calculated to absorb huge amounts which can then be lowered into a medium to heat our water. Then we go back full circle to the shc of water and it being a b1tch to heat up...

I need a beer!

 

[chris watkins]

I need a beer!

Your overheating Dave😀

 

[GregKaye]

Thermal stores are still available & still have there place but as said before the amount of hot water (heat energy) you would need to store to provide for domestic heating & HW often means they are impractical.

thanks.
its appreciated to get advice from an actual pro 🙂

 

[GregKaye]

Looks similar to a wet (heating only) system I installed years ago at an outdoor centre. Place was off-grid and previously relied on a generator which had been replaced by a wind turbine and solar PV feeding battery storage & inverters with the genny as backup. Existing turbine controls dumped excess energy into a large resistor heating up the locality once the batteries were charged. We fitted a 1000L buffer tank with 4kW immersion heaters (8x500W) switched by the existing controls so instead of wasting energy it was used to preheat the tank. Heating was weather compensated with 3-way valve. According to the site manager the boiler hardly ran at times in spring and autumn.
Water might not be the best material for thermal storage but it's the easiest to install without getting expensive.

Thanks, its also easy to get the heat out of water which, at times when people might not want to use much energy, has its own value.

 

[GregKaye]

Remember water is actually a rubbish medium for heat transfer as it's shc is so high. We'd be better off using a different medium but it'd be more expensive and less 'simple' to service.

That's new to me. I thought that a high specific heat capacity was a good thing. I thought it meant that more heat could be contained.

 

[Welder]

That's new to me. I thought that a high specific heat capacity was a good thing. I thought it meant that more heat could be contained.

It's that double edged sword Greg. Reasonable retention but hard as hell to heat.

 

[Brambles]

We design and instal, one off renewable energy solutions, generally for larger properties or small commercial premises. In essence your scheme is viable, but would require a fairly complex control system to optimise the performance - the inclusion of the intermittent heat pump (gym powered) significantly adds to the complexity of the system. Heat pumps ideally need to be operational 24/7

In general, if you can design around standard components a neater more economic solution would be achieved.

Three or four coil tanks are only viable with tank capacities greater than 500 litres.

If you are looking for the system to be granted RHI status, then it would need to be designed strictly in accordance to the RHI scheme rules

Hope this helps

 

[Chrisjones.7976]

To store enough water for heating isn't on. You would need a massive amount of storage, just think how much water is contained in a central heating system & multiply it by the number of changes you need to keep the house warm. Yes you can get 3 coil cylinders, I have one, the intermediate coil above the solar one is heated by a wood stove, the boiler heats the top one. I also have an immersion heater which is fed by PV solar panels to stop the surplus electricity going back into the grid.

Regards

Chris

 

[Stigster]

To store enough water for heating isn't on. You would need a massive amount of storage, just think how much water is contained in a central heating system & multiply it by the number of changes you need to keep the house warm.
Chris

This was exactly the problem with our local brand Ecostor heatstores. You put the heating on in the morning and your thermal store was full of luke warm water in about an hour, no good for bathing in conjunction with that. Ecostor were usually 300 litres volume I believe and even that would only work with very careful timed use of the system or in a bedsit with 2 rads and one shower, usually electric!