Organic Rankine Cycle (ORC) and renewable energy

[chatelot16]

the water boils at 100 ° C at atmospheric pressure but only a lower pressure is required to make it boil at 50 ° C

at the top of Mont Blanc hot water does not boil at 100 ° C!

the first steam engine was running at full pressure: a copper boiler with no pressure resistance, which sent vapor at atmospheric pressure into the cylinder, and a vacuum on the other side of the cylinder thanks to the depression in the cylinder

you just have to choose the right pressure to make a real rankine cycle between 100 and 50 ° C

this operation entirely to depression could be done using an ordinary boiler to steam: it does not subject it to any dangerous pressure

[Did67]

1) Anyone know why it is called "organic", this cycle ???

2) If you operate in "depression", doesn't that negatively impact the efficiency of the turbine? Turbine less dense gas doesn't have to be great, right ???

[Christophe]

Yes I read that it was because the refrigerated fluids are "carbonaceous" ... (not all but some) therefore of the carbon cycle, therefore organic ... there may be another explanation.

chatelot16 stops quibbling: trace cycles of examples on Mollier of the water and a refrigerant fluid to convince you that low T ° better is a low boiling point fluid (which will also be lowered with the pressure)... and we are in a closed cycle there!

For those who want to get to the bottom of things, here is a comparative Stirling Ranking: https://www.econologie.info/share/partag ... dbrFG1.pdf

[Ahmed]

From what I understand, "organic" occurs when an organic fluid (carbon base) is used to lower the phase change temperature below that of conventional water vapor.

[chatelot16]

the normal rankine cycle is the steam engine

if we replace the water with chloroform or petroleum ether it is the organic rankine

I quote these products because they were tried at a time when freon did not exist

there was also a trial with amoniac

all these products are part of organic chemistry ... not to be confused with organic!

the low pressure of the steam at 50 ° does not affect the efficiency ... it is necessary that the piston or the turbine is adapted, and that the pipes is big enough

do big and low pressure is not more expensive than doing small and high pressure

in any case at the beginning of the steam engine he preferred to make large copper sheet cylinder operating in depression ... it is only with the progress of mechanics that it has risen in pressure

when we reached the pressure of 3 or 4 bar we abandoned the condenser and passed to the atmosphere escape ... which forgets the heat below 100 °

it was not until late on boats that could not withstand more than 3bar's sea water that we started putting condensers back in to recycle steam without really taking advantage of the depression.

and then we made double or triple motor expension to take advantage of all the relaxation until the depression of the condenser

and then we kept the piston for the high pressure and a turbine to finish the relaxation until the condenser

[chatelot16]

here is an interresting document
https://www.econologie.info/share/partag ... jXjItL.pdf

alas the internet link does not work anymore ... so I get it out of my computer

I discovered by chance a course of aerodynamics of this teacher that I found far superior to all others ... and I took the opportunity to download all he had put on the same site

we see page 14 a thermal power plant turbine where the pressure goes down to 0,055 bar ... so 0,945 bar depression ... almost empty

we also see that the simple rankine cycle does not have the maximum yield of carnot ... to do better it takes a little more complicated cycle, with overheating: which is easy when you make steam in the boiler, but what is impossible when you only have this freon machine behind a water exchanger

before drawing a cycle on the diagram of mollier I must find a more readable

the diagram TS is not easy to understand ... the diagram pv and more interresting to show some thing ... I have in my project to make an exel spreadsheet that automatically displays all the diagram used in thermodynamics

[bidouille23]

Good evening,

Christophe I never said that we saw anything on the video;), it's just what I found point ..

On the other hand the cycle of rankin I discover too and suddenly it's cool, it will have at least served something;) ... thank you for the links.

Personally I have a lot of head in log stoves (I know the yields are not great in front of the pellet), as much lower the yield on a pellet combustion leaving the fumes 110 ° c instead of 70 ° it seems to me too bad, as much on a wood stove at the exit of the stove have turned rather around 170 200 ° c, which seems more playable with such a system?

But I'm not completely neophyte ...

I'm going to look into the subject and try to understand something, it's not won;), but it's not lost (whatever ... ) ...

At the sight of chatelot nose you seem credible or not as hypothesis? (for a wood stove I hear of course knowing that I am aware that the operating time of a wood stove is rather of the order of 6 to 8 h)

in the idea I would imagine loading old battery and make a system of power for the light, based on led, in the decoupled house of the network, thus having the lighting of the independent house ...

[chatelot16]

and even I who am in the subject for a long time I can get lost ... I could not trace what I wanted in the diagramm mollier ...

bin yes I was thinking of the diagram TS ... but the mollier you put is in diagram HS

the true mollier TS is more convenient to trace the cycle, quite to convert then in HS for some reason
https://staff.ti.bfh.ch/sub1/docu_th/di ... ts_300.gif

I really have to do this spreadsheet that does all the graphs simultaneously: pv ts hs ...

[Christophe]

Yes the hs is not the most instinctive I agree! the ts is also my "favorite" ...

But I put it because the above on the Rankine yield is calculated on the hs and enthalpy differences ...

If on the ts you have the h, no worries ...

I really have to do this spreadsheet that does all the graphs simultaneously: pv ts hs ...

Waaw motivated! But we must find that on the net, no?

[chatelot16]

Personally I have a lot of head in log stoves (I know the yields are not great in front of the pellet), as much lower the yield on a pellet combustion leaving the fumes 110 ° c instead of 70 ° it seems to me too bad, as much on a wood stove at the exit of the stove have turned rather around 170 200 ° c, which seems more playable with such a system?

But I'm not completely neophyte ...

I'm going to look into the subject and try to understand something, it's not won;), but it's not lost (whatever ... ) ...

At the sight of chatelot nose you seem credible or not as hypothesis? (for a wood stove I hear of course knowing that I am aware that the operating time of a wood stove is rather of the order of 6 to 8 h)

in the idea I would imagine loading old battery and make a system of power for the light, based on led, in the decoupled house of the network, thus having the lighting of the independent house ...

if the smoke comes out at 200 ° C it does not prove that there is a lot of energy to take

if the outside temperature is 0 ° we have taken all the energy of the smoke when it is cooled to 0 ° C

if you try to heat a steam boiler to 200 ° C it will not produce anything

if you lower the pressure to boil it at 180 ° C it will only recover 10% of your power of smoked

if you boil at 100 ° C you get 50% of the smoke so you get more heat power, but with a lower efficiency because lower temperature

conclusion the rankine cycle is not effective to recover the power of a stream of smoke whose temperature decreases as it takes its heat

it is possible to adapt a stirling to this operation: the hot gas comes into contact with the hottest point, then passes at different places along the cylinder capable of capturing energy at lower temperatures

but why run a heat engine with this lost heat difficult to use?

you have to run the engine with the temperature of the lights: a small boiler steam well placed in the stove can take all the power you want to 200 ° C ... and the engine will easily perform well

a striling can go up to 500 ° C or the good performance expected ... but it is more fragile: rapid overheating in case of failure

if we want to recover the power of the smoke it is simply necessary to heat it, so to pass the smoke in a heat exchanger ... well on this complete cooling breaks the draw ... it is necessary to replace the thermal draft by a fan *

another remark when the novotek boiler makes water at 110 ° C, it is with the flow of water that it is necessary to give all the power of the boiler: it is better than the smoke whose temperature will go down as soon as we take him energy