thermodymic panel for water heating

1echidna

Ref http://www.e3renewables.com/wp-content/uploads/2011/06/Energie-Brochure.pdf

1 panel
Tank 200 litre min Compressor 390W (min power) Max thermal output 1690W

2 panel
Tank 200 litre min Compressor 595W (min power) Max thermal output 2800W

These figures are produced by the manufacturer. Note the compressor power figures are minimums and the heat outputs are maximums with no claims about COPs or whether indeed the low compressor power can occur concurrently with the high heat output..

zeupater

1echidna wrote: »

Ref http://www.e3renewables.com/wp-content/uploads/2011/06/Energie-Brochure.pdf

1 panel
Tank 200 litre min Compressor 390W (min power) Max thermal output 1690W

2 panel
Tank 200 litre min Compressor 595W (min power) Max thermal output 2800W

These figures are produced by the manufacturer. Note the compressor power figures are minimums and the heat outputs are maximums with no claims about COPs or whether indeed the low compressor power can occur concurrently with the high heat output..

Hi

My opinion would be that the maximum thermal output would be when the water was at it's coldest and therefore the refrigerant return temperature to the evaporator would be lowest, therefore the compressor would be running at it's lowest loading and the system therefore at it's highest COP ...

As the water heats, the return temperature to the evaporator increases and the panel becomes less able to absorb energy through conductive transfer, the control system will likely need to increase the duty on the compressor to compensate in order to achieve the higher condenser temperatures to heat the water to 55C ... this is why I would take the minimum rated power of the plate over the maximum rated power of the compressor as being a more realistic COP and that's where the COP of 3.1 came from in a previous post #71, which is exactly the same performance level as claimed by 'Ecocute' systems made by many of the largest heatpump manufacturers in the world, using some of the most efficient compressors in the world, and mainly being major electronics brands, some of the most efficient control systems in the world ....

HTH
Z

1echidna

zeupater wrote: »

Hi

My opinion would be that the maximum thermal output would be when the water was at it's coldest and therefore the refrigerant return temperature to the evaporator would be lowest, therefore the compressor would be running at it's lowest loading and the system therefore at it's highest COP ...

As the water heats, the return temperature to the evaporator increases and the panel becomes less able to absorb energy through conductive transfer, the control system will likely need to increase the duty on the compressor to compensate in order to achieve the higher condenser temperatures to heat the water to 55C ... this is why I would take the minimum rated power of the plate over the maximum rated power of the compressor as being a more realistic COP and that's where the COP of 3.1 came from in a previous post #71, which is exactly the same performance level as claimed by 'Ecocute' systems made by many of the largest heatpump manufacturers in the world, using some of the most efficient compressors in the world, and mainly being major electronics brands, some of the most efficient control systems in the world ....

HTH
Z

I feel that I am one stage further along the line to understanding this system. I have ascertained that the compressor doesn't have an inverter, is not direct current and therefore is not a variable speed device.

Really though to determine various cases within the design envelope you need to consider compressor, evaporator, condenser performance and expansion valve control.

All I can say I think is that there is the potential to pump more refrigerant at high ambient temperatures and sunshine giving high evaporator pressures and low condensing pressure (low water temp). This is because the gas will have a higher suction density and the pressure ratio will be lower. A lot depends on compressor characteristics as well as the performance of the other parts of the system.

Martyn1981

OK, yet another stupid question (but at least I'm listening and learning), how important is humidity to all of these calculations?

Mart.

zeupater

Martyn1981 wrote: »

OK, yet another stupid question (but at least I'm listening and learning), how important is humidity to all of these calculations?

Mart.

Hi M

For absorbing radiation, absolutely nothing in isolation .... that's why I'm trying to describe the process as being in a vacuum in order to remove the complex interaction between the various forms of heat transfer.

In reality, when looking at the 'real world', humidity will have a pretty significant effect on the very complex exchange of heat, which has been touched on before ...

High humidity will carry more energy (per unit volume of air) for conductive transfer and condensation will release this energy, initially boosting the efficiency of the plate .... however, the condensation will immediately freeze, form ice and insulate the plate from the remainder of humid airmass, thus reducing the temperature differential between the surface of the evaporator unit (was metal, now ice) and the atmosphere, so capacity to transfer heat through conduction reduces and the system efficiency drops .... The frost/ice will be white, which reduces both the emissivity and also therefore the absorption of the plate and will reflect a pretty large proportion of any daytime solar gain, also effecting the nighttime (&daytime) 'black body' heatloss/gain budget if this is considered significant (I believe it's not) .... As a result of this the system will need to (/should be capable of) entering a 'defrost' mode, which could be by simply switching off for a while, or heating the plate in order to force the ice to melt, and slide off, describing either a significantly longer total cycle time to deliver heat to the HW cylinder, or a less significant increase in time with an associated loss of efficiency ....

HTH
Z

1echidna

The only thing I can add to what zeupater has said is to consider if there were parts of the operating envelope when the pressure in the evaporator were sufficiently high for evaporation to be occurring above 0C. Ambient temperatures would need to be high and possibly include sunshine to give sufficient heat transfer but much higher COPs would be achievable. Moisture would give a small increase in heat transfer in this situation.

1echidna

Thermodynamic installed at Maidstone UTD Football Club

These larger multipanel systems are not too comparable with one panel domestic hot water systems but interesting all the same. And I bet the salesmen will be trying to sell on the basis of some large scale installations being installed.

playingthegame

The thermodynamic system are proving very good and effective. They really do knock the thermal solar out of the park.

However, the prices are still horrendous from the direct sales companies.

If you look around you can buy the thermodynamic panel hot water system for around £3,500 to £4,500 spending £9,000 is ridiculous..

The RHI is also coming next year and if the companies can produce the relevant paperwork to back up their claims for the CoP then it looks like this will also qualify. If it does then this technology is a no brainer.

lynneinjapan

Reviving an old thread because we're looking at the possibility of installing solar thermal but the only company we've had a quote from so far were offering solar thermodynamic instead. We'd been reading up about the options and had decided against thermodynamic as (a) the products currently available are apparently better suited to the warmer climates of southern Europe and (b) it doesn't qualify for the Renewable Heat Incentive (I think because it uses refrigeration rather than water or glycol like solar thermal).

However, the guy who quoted seems to have won my husband over with his talk of efficiency, and also seems to have told him that it HAS now been MCS-approved and will soon be added to the RHI scheme, at similar rates to solar thermal if I remember correctly. Does anyone know whether this is true?

EricMears

lynneinjapan wrote: »

. . . . . . However, the guy who quoted seems to have won my husband over with his talk of efficiency, and also seems to have told him that it HAS now been MCS-approved and will soon be added to the RHI scheme, at similar rates to solar thermal if I remember correctly. Does anyone know whether this is true?

Not a clue (though very sceptical )

I'd suggest you tell him you're very, very interested in buying but knowing how these government schemes work, you won't risk placing an order until he gets back to you with confirmation of eligibility (then prepare for a very long wait !)