Thermo dynamics for hot water that runs off atmosphere

[steve k]

Although I have gracefully bowed out of this discussion. I see no reason why I can not provide real life facts.

A friendly competitor of mine who i was chatting with today, informed me that in the recent cold weather, a system he had been monitoring has taken 7 hours to recover a depleted 200l tank back up to 55 deg C. (from 5 deg C entering)

Steve

 

[jason121]

I got called to look a 16kw ground source pump, time water got to house it was 30 degree, left buffer tank at 40, thou the buffer tank was ony 200 litres.

 

[Worcester]

@SteveK - do you (or he) consider that good or bad?

 

[Gavin A]

Yes they did a full evaluation which did cost a lot of money but nothing even close to trying to defend a case in court from a consumer looking for their money back plus compensation.

Very few if any will save money using the system because there are more issues at large than the warped performance figures.

That said the theory is good and there is a better chance of a return from the larger commercial system however it must be used bivalent instead of the stand alone recommended by the manufacturer.

Do you mind me asking what methodology they used?

Did they test it with varying wind and solar input levels, or just in static air at different air temperatures?

If the latter then I'm not surprised it didn't come out too well.

 

[steve k]

@SteveK - do you (or he) consider that good or bad?

Bad enough for him to cancel a presentation to his local council he had planned, and pull out of the market.

Me?, I'm a simple refrigeration engineer and I have chosen not to express my opinion on this thread. But I will present real life facts as they become apparent.


Steve

 

[peteheat]

Do you mind me asking what methodology they used?

Did they test it with varying wind and solar input levels, or just in static air at different air temperatures?

If the latter then I'm not surprised it didn't come out too well.

The system was installed with the panel on the roof facing south, the hot water was taken from the cylinder two ways (different tests) the first using a timed release of hot water (very wasteful) to simulate domestic usage the most taken from a 280L cylinder was 100 litres at a time.

The second was using a system link which allowed it to dump the heat into their central heating system.

The entire procedure lasted over six months.

 

[steve k]

Today's observations on a 200l cylinder:

Ambient - 2.5 deg C
Compressor draw - 3.6 amp
Water entering - 8 deg C
Raise - 24 deg C (to 32)
Time - 90 mins

I did check today if the immersion was on during initial warm up. It wasn't.

 

[Gavin A]

Today's observations on a 200l cylinder:

Ambient - 2.5 deg C
Compressor draw - 3.6 amp
Water entering - 8 deg C
Raise - 24 deg C (to 32)
Time - 90 mins

I did check today if the immersion was on during initial warm up. It wasn't.

I get that as being a COP of 4.3ish, depending on what the grid voltage was (figure given is for 240V / 864W / 1.3kWh electrical input, 5.58kWh heat required to heat 200l of water by 24 deg), and if that was the ampage for the entire time.

That's none too shoddy. What was the weather like?

 

[steve k]

My measured voltage was 243v, the amp draw fluctuated between 3.2 and 3.6a. The weather was 2.5 deg C, windy and cloudy.

Steve

 

[Gavin A]

I thought it would have been windy, or sunny.

obviously this would be at the point where the heat pump was operating more efficiently due to the lower output temps, and would presumably drop off the COP as the output temperature rose to 55deg, but still a COP of 4.25 at 2deg external air temp is pretty good.

 

[vincentmcconnel]

info

Can you email me some info ?
[email protected]

 

[Michael.P]

Re: info

I have read all posts in this thread with great interest. I am about to chuck away my combi boiler and install a 400 litre thermal store to keep up with increased central heating and DHW requirements. (i am doubling the floor area of my property and adding a further bathroom). The thermal store will be heated by various sources. A mains gas boiler, a multifuel stove and also an electric heat source powered by effectively free of charge excess electricity produced by my 4kw solar PV array and diverted using an immersun unit. I could simply use an immersion heater, but thermodynamics has caught my eye. I can buy and install a single panel thermodynamic system myself for around £2000 (including F gas installation). As the electricity is 'free' and looking at the claims for thermodynamic systems i think the investment could well be worth it. Does anyone have any views on this idea, any input would be gratefully received, thanks, Michael.

 

[jason121]

Interesting. Can you explain further why mixing all the the forms of heating into one store.
How will you combine the thermodynmaics system into the thermal store?
Where abouts are you in East Midlands. Sorry about or the questions just interested

 

[Michael.P]

Interesting. Can you explain further why mixing all the the forms of heating into one store.
How will you combine the thermodynmaics system into the thermal store?
Where abouts are you in East Midlands. Sorry about or the questions just interested

I need a big thermal store as i will have 18 rads and 5 underfloor circuits and 3 bathrooms to service. I didnt want to heat it using just gas as i am trying to keep running costs down. I have a steady supply of free wood for the multifuel stove (winter) and the free surplus from the PV (summer) to this end. If i use thermodynamics it will be via an indirect coil in the bottom of the thermal store (one usually used for solar thermal). The store needs to be 75C at the top, the bottom will run cooler as it is where the return pipes from the heating circuits come back in. I'm hoping that the advertised 55C will work at the bottom of the store....... I am based near Ashbourne, Derbys.

 

[jason121]

i thought thermodynamics had to be on its own cylinder as it works with F gas

 

[The Solar King]

400 litre thermal store is way too small. This will be little more than buffer tank. This needs to be correctly sized for the job in hand and the range of heat inputs. Immerses need to be correctly located so it can be used for hot water only in the summer. You will probably find you need a tank of at least 2000 litres. Are you planning to use an internal heat exchanger or an external plate heat exchanger for hot water?

with regard to thermodynamics, read all the threads on this site before making a decision. They are currently excluded from MCS and RHI. You could be far better off with traditional solar thermal.

 

[Earthstore]

400 litre thermal store is way too small. This will be little more than buffer tank. This needs to be correctly sized for the job in hand and the range of heat inputs. Immerses need to be correctly located so it can be used for hot water only in the summer. You will probably find you need a tank of at least 2000 litres. Are you planning to use an internal heat exchanger or an external plate heat exchanger for hot water?

with regard to thermodynamics, read all the threads on this site before making a decision. They are currently excluded from MCS and RHI. You could be far better off with traditional solar thermal.

I agree, just one point though, if Micheal P has gas into his heatstore, then will he still be eligible for the RHI?
I believe it is a good idea to have several heat sources to a heatstore although it can make it a little difficult to set up, as ideally at any point in time you want the "free heat" to be used first, IE logs in your case, however your "free heat" will change daytime/nighttime, winter/summer.
Complex but possible, get it right and it would be fantastic.

The jury is still out on thermodynamics, as an addition to your heatstore, personally, if it was in my budget I would give it a go, but I would not rely on it, but in twelve months time you may be telling us great it is.

 

[jason121]

If still has gas boiler a meter will have to be fitted on the heat pump to qualify for RHI i believe

 

[Michael.P]

i thought thermodynamics had to be on its own cylinder as it works with F gas

I was thinking of using one of the magic box systems which basically outputs the water at 55C from the box. Feeding this to an indirect coil distances the F gas from the thermal store. I hope i am correct?

 

[Michael.P]

400 litre thermal store is way too small. This will be little more than buffer tank. This needs to be correctly sized for the job in hand and the range of heat inputs. Immerses need to be correctly located so it can be used for hot water only in the summer. You will probably find you need a tank of at least 2000 litres. Are you planning to use an internal heat exchanger or an external plate heat exchanger for hot water?

with regard to thermodynamics, read all the threads on this site before making a decision. They are currently excluded from MCS and RHI. You could be far better off with traditional solar thermal.

The hot water is created indirectly by running mains pressure cold thru the store via a high recovery stainless coil. See eco-equipped.com for the products. I will use an EC solar 400 with an add on to run UFH indirectly. I cant use solar thermal as the only roof available is north west facing.....not worried about RHI payments, i just thought that thermodynamics might be a better way of using the excess from the PV array