thermodymic panel for water heating

1echidna

I think the point about the high evaporator load case 2.35 kW is that it might be very much a peak design case within an operating envelope.

I wish I could find someone knowledgeable on the supplier side to explain in more detail the basis of the figures and the technology (particularly compressor).

grahamc2003

zeupater wrote: »

I read, reread and understood what was written ... please note that these conditions would be in a vacuum and if the blackbody temperature was low ... possibly close to 0K as stated in the reply ... please check.

I intentionally used the 'black oven' to demonstrate the point ... the oven is black, there is no light and it isn't switched on, but, importantly it isn't a freezer because it has a thermal mass and a temperature significantly above absolute zero.

Please also have a look through the points raised in post #74 and explain where a pretty well known law of Physics is wrong or where the logic I have applied this law to the flat panel is substantially wrong ... I specifically structured the post so that the point at which consensus is lost can easily be identified and discussed ... a typical problem solving approach - take a complex problem and split it into smaller problems which can be solved ....

HTH
Z

Point 1 I'm afraid.

I agree with the values of the radiation from the sun. But if we treat it as a point source of radiation, then we have to take into account an infinite number of other point sources of radiation due to the panels being cooled below most other things - something you don't have to consider with other types of solar panels (where the radiation balance with the general environment excluding the sun will be pretty close to zero).

Regarding the man in a sphere - I too am trying a bit of stepwise refinement and trying to explain my understanding at the most elementary level - but you won't let me! I'm not considering anything other than the radiation flow from the man to the sphere, not the balance of radiation between the man and the sphere. The man will emit due to his (absolute) temperature, and the sphere will emit due to the sphere's temperature, but the two are independent. Would you agree with my statement now?

zeupater

grahamc2003 wrote: »

Point 1 I'm afraid.

I agree with the values of the radiation from the sun. But if we treat it as a point source of radiation, then we have to take into account an infinite number of other point sources of radiation due to the panels being cooled below most other things - something you don't have to consider with other types of solar panels (where the radiation balance with the general environment excluding the sun will be pretty close to zero).

Hi

And considering that solar irradiation is completely ignored in the rest of the post because it assumes radiation in nighttime conditions ... if you are an engineer, and I assume you are, then please address the issue .... I'm not trying to trap you, it's basic physics on which engineering is based .....

Forget about point sourcing as it's not necessary, the calculations effectively assume that the panels are in a vacuum between two walls at 7C at night ... transfer is therefore sqm for sqm ... the ony time that this is placed into a point source context would be at the point where the consideration of the effect of placing the panels on the roof is raised ...

HTH
Z

1echidna

zeupater wrote: »

Hi

And considering that solar irradiation is completely ignored in the rest of the post because it assumes radiation in nighttime conditions ... if you are an engineer, and I assume you are, then please address the issue .... I'm not trying to trap you, it's basic physics on which engineering is based .....

Forget about point sourcing as it's not necessary, the calculations effectively assume that the panels are in a vacuum between two walls at 7C at night ... transfer is therefore sqm for sqm ... the ony time that this is placed into a point source context would be at the point where the consideration of the effect of placing the panels on the roof is raised ...

HTH
Z

Just one point Z, the absorption of radiation in the air is small, the surrounding air is cooled by convection. Thus as far as radiation is concerned no need for a vacuum for it to occur.



http://www.radartutorial.eu/07.waves/wa13.en.html

zeupater

grahamc2003 wrote: »

... Regarding the man in a sphere - I too am trying a bit of stepwise refinement and trying to explain my understanding at the most elementary level - but you won't let me! I'm not considering anything other than the radiation flow from the man to the sphere, not the balance of radiation between the man and the sphere. The man will emit due to his (absolute) temperature, and the sphere will emit due to the sphere's temperature, but the two are independent. Would you agree with my statement now?

In reply to the added content ....

Thank you, you are now in agreement with my post, apart from considering the relative mass of the man vs the sphere ...

The man will be emitting around 523W/sqm at body temperature ... the sphere will be emitting depending on it's own temperature and the man will be absorbing the energy ... the rate of warming or cooling will depend on the balance of the energy budget ...

Having an understanding of this will obviously allow the principle to be applied to the remainder of post #74 without further diversion ...

HTH
Z

zeupater

1echidna wrote: »

Just one point Z, the absorption of radiation in the air is small, the surrounding air is cooled by convection. Thus as far as radiation is concerned no need for a vacuum for it to occur.



http://www.radartutorial.eu/07.waves/wa13.en.html

Hi

I know, and appreciate the point, but I am attempting to leave the effect of conduction of heat from the solid surface to the air and the associated convective current which the change in air density causes aside ... to simplify the issue it's best to treat the radiation as being in a vacuum then there can be no misinterpretation ...

HTH
Z

1echidna

As far as I can see there are attempts to sell this kit by any number of suppliers. The originator seems to be Energia Solar of Portugal manufacturer of Bomba compressors. Quite a number have been installed in Europe. I am still to be convinced that their quoted COP for a one panel system of 4.3 means anything for practical application.

1echidna

I see that the 550W compressor, 2900W heating at 7C ambient is a two panel evaporator case.

I can't see any mention of an inverter and variable speed, compression ratio compressor which would make the COP claims a possibility. You would think that if they had got it they would flaunt it?? An application for refrigerators is discussed at http://www.panasonic.com/industrial/includes/pdf/invertercompressors-improvingefficiency.pdf

zeupater

1echidna wrote: »

As far as I can see there are attempts to sell this kit by any number of suppliers. The originator seems to be Energia Solar of Portugal manufacturer of Bamba compressors. Quite a number have been installed in Europe. I am still to be convinced that their quoted COP for a one panel system of 4.3 means anything for practical application.

Hi

I'm pretty convinced that the non-direct-solar radiation element is negligable and that the high quoted COPs you have include southern-europe high solar gains, once more, the higher COPs we have been discussing are likely based on provision of 18kWh of daily water heating into a cold cylinder specifically to lower the average water temperature to 32.5C(((55-10)/2)+10) whereas an average temperature of around 42.5C(((55-30)/2)+30) would be more typical/realistic .... using 18kWh as a daily heating demand also improves the payback calculation ....

HTH
Z

1echidna

zeupater wrote: »

Hi

I'm pretty convinced that the non-direct-solar radiation element is negligable and that the high quoted COPs you have include southern-europe high solar gains, once more, the higher COPs we have been discussing are likely based on provision of 18kWh of daily water heating into a cold cylinder specifically to lower the average water temperature to 32.5C(((55-10)/2)+10) whereas an average temperature of around 42.5C(((55-30)/2)+30) would be more typical/realistic .... using 18kWh as a daily heating demand also improves the payback calculation ....

HTH
Z

I can't see how they get to 18kWh, heat gain or no heat gain, a compressor of 390W just won't pump the amount of refrigerant required. I agree on the water temperatures. I'd love to think we had a bit of the latest technology in terms of compressor efficiency, variable speed and process control but some claims stretch credulity beyond even that. If you had one of these things installed it would need to be extensively instrumented and complex calculations carried out to actually establish true working COPs and whether the design claims are met. I guess they rely on nobody being able to carry this out.