Performance and efficiency of a solar thermal system

Solar thermal energy in all its forms: solar heating, hot water, choosing a solar collector, solar concentration, ovens and solar cookers, solar energy storage by heat buffer, solar pool, air conditioning and solar cold ..
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bernardd
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by bernardd » 19/12/09, 14:51

Hello,

Kéké wrote:It is important I think to put the debate back in the low temperature context.


Indeed, in the context of low temperature, a flat sensor can be justified.

But how many existing central heating installations (under water) are in low temperature? And 65 ° C at least per peak is a legal requirement in hot water.

So for the majority of non-solar installations today, the vacuum-based heat pipe sensor is the best solution for an existing installation upgrade.

In addition to the highest temperature, the faster temperature rise makes it possible to enjoy the least sun in winter, and it is in winter that solar energy is the most important.

It is also in winter that the increased vacuum insulation keeps a high sensor temperature even if it is outside xNUMX.

In addition, the search for solar cogeneration + granulated solution passes through minimum temperatures of 200 ° C, and to my knowledge, only vacuum heat pipe solar collectors allow this.
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by I Citro » 19/12/09, 22:19

: Arrow: My understanding of solar thermal has come a long way since my CESI went live.

In fact the production can take place only in the range where the temperature of the sensor is higher than that of the balloon.

In winter, the production will start later if we have not drawn ... the production will also stop earlier because the sun is declining, the capture temperature will also fall quickly, ending the transfer to the storage tank.

This is why the sensors of a CESI can be afflicted with shading without loss of performance because the production will occur in a short time range located near the zenith.
It is quite different for photovoltaics as I pointed out in this subject or it would have been better to place the PV sensors in place of the CESI sensors and put the CESI sensors in place of the PVs at the bottom ... Because the shading of the construction on the thermal sensors at the beginning or end of the day n 'would have decreased their production, contrary to PV ...
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by Cuicui » 20/12/09, 10:31

citro wrote:In winter, production will start later if you have not drawn enough.

Not necessarily, if the temperature sensor is located at the bottom of the balloon. When water is drawn, cold water replaces hot water at the bottom of the balloon.
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by bernardd » 20/12/09, 13:14

Hello,

citro wrote:In fact the production can take place only in the range where the temperature of the sensor is higher than that of the balloon.


And yes, as for electricity or any other area, there is flow only if there is potential difference. In thermal, the potential is the temperature, and the heat goes to the low temperature ...

That is why for a water system, the ideal would be to have a starting tank to the solar collectors with cold water, and a tank of hot water for its storage.

As there is often a problem of space, the tank with stratification was used: the hot water rises naturally at the top, and we take the water towards the sensors at the bottom.

And if the yield is important, it is better to cool the water before returning it to the sensors, even if this residual heat is lost: it is the cooling towers of the plants, for example nuclear ...
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by keke » 20/12/09, 15:59

Hello,

bernardd
But how many existing central heating installations (under water) are in low temperature? And 65 ° C at least per peak is a legal requirement in hot water.

Put in place solar under entent for me have already made the necessary structural changes, heating circuit perpetually 60 ° C denotes an old installation, to modernize.
Concerning the ECS, the ANAH recommends, I quote:
The temperature of the domestic hot water must not exceed 50 ° C at the point of drawdown in the rooms intended for the toilet and 60 ° C in the other rooms (stop of the 30 November 2005). In storage tanks, if it is better for sanitary reasons not to go below 60 ° C, this value should not be exceeded to avoid scaling.

My installation, for example, runs continuously between 45 and 50 ° C, and rises to 60 ° C once a week (legionella protection).

So for the majority of non-solar installations today, the vacuum-based heat pipe sensor is the best solution for an existing installation upgrade.

So for the majority of aging installations, the investment that is required in the first place is an upgrade, not a switch to solar.
To fill a strainer with water, there are two solutions, plug the holes or ... use a fire hose. The first is a durable solution, the second an insane waste.

In addition to the highest temperature, the faster temperature rise makes it possible to enjoy the least sun in winter, and it is in winter that solar energy is the most important.

Rising temperature faster? would the heat capacity of the water be different for vacuum sensors? not of course, so it takes the same energy to increase 1 ° C 1 liter of water, so I see no evidence in all this.

That is why for a water system, the ideal would be to have a starting tank to the solar collectors with cold water, and a tank of hot water for its storage.

A stratified tank somehow ;-)

And if the yield is important, it is better to cool the water before returning it to the sensors, even if this residual heat is lost: these are the cooling towers of the plants, for example nuclear plants.

You can also put the hot water in the sewer, which makes it possible to remake and to be able to say I did a lot more hot water than I need it. Regarding the nuclear cooling towers (compare solar and nuclear ???), the problem is somewhat different, the nuclear produces steam to run turbines, so we are in the presence of a technology that is based on a phase change of the water (vapor - liquid - vapor), this is absolutely not applicable to the production of domestic heat.

cordially
Keke
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by bernardd » 20/12/09, 16:41

Kéké wrote:Put in place solar under entent for me have already made the necessary structural changes, heating circuit perpetually 60 ° C denotes an old installation, to modernize.


Why apply economic reasoning only to the sensor? The replacement of the pipes of the heating does not bring much whereas the cost is enormous and will NEVER make profitable: as much put solar collectors.

Kéké wrote:So for the majority of aging installations, the investment that is required in the first place is an upgrade, not a switch to solar.
To fill a strainer with water, there are two solutions, plug the holes or ... use a fire hose. The first is a durable solution, the second an insane waste.


How does the higher temperature of the circuit increase waste? It is certainly necessary to isolate behind the radiators ... By cons, we can store more heat.

This was exactly the talk of the heating engineers, who wanted to be paid for the replacement of everything. It was a bit true when only low temperature flat collectors existed ....

Rising temperature faster? would the heat capacity of the water be different for vacuum sensors? not of course, so it takes the same energy to increase 1 ° C 1 liter of water, so I see no evidence in all this.


I was talking about vacuum heat pipe sensors: there is no water in it. Obviously, the transport water circuit is drained in the absence of sun, so the water remains at internal temperature of the house and does not freeze: when it goes back, it does not have to take 20 or 30 ° for nothing.

In addition, with concentrators, we could put a single tube for 2m2 ...

A stratified tank somehow ;-)


Yes, except that currently a stratified balloon costs a fortune, while 2 balloons well insulated standards cost nothing, especially recovered at the dump of the corner ... And increase the storage of hot water.

You can also put the hot water in the sewer, which makes it possible to remake and to be able to say I did a lot more hot water than I need it.


But that's what we do every day while taking a shower. And nobody talks about it, amazing no? I do not know of any double flow that recovers the heat of the hot water discharged to the sewers ...

Regarding the nuclear cooling towers (compare solar and nuclear ???),


No difference, the nuclear is just used to heat a boiler, it is more complicated because of the dangers of the fuel.

the problem is a little different, the nuclear produces steam, to turn turbines, so we are in the presence of a technology that is based on a phase change of water (vapor - liquid - vapor), this is not is absolutely not applicable to domestic heat production.


I was at the theory level: the principle of the cycle is always the same, it needs a hot source and a cold source, even if we do not go up to vaporization.

And as common sense would like to be able to make electric cogeneration with solar at home, the rise to steam becomes an attractive option.
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by keke » 20/12/09, 20:55

Hi,

Why apply economic reasoning only to the sensor? The replacement of the pipes of the heating does not bring much whereas the cost is enormous and will NEVER make profitable: as much put solar collectors.

I did not apply economic reasoning, I did not talk about return on investment, amortization period, I reasoned energy efficiency, for the same price, it is possible to install a larger energy capture area with flat sensor, so to produce more renewable energy, so save more non-renewable resource.
I also did not talk about the total replacement of the heating system, I argue that a former heating system is often not regulated in terms of energy consumption, the replacement of old regulations is not so expensive and allows you to make substantial savings.

How does the higher temperature of the circuit increase waste? It is certainly necessary to isolate behind the radiators ... By cons, we can store more heat.

The higher the temperature, the more losses there are.
Isolate behind the radiators? and the roof, and the double glazing, and ... all the rest?
The speech of the heating engineers? just change the regulation, the opposite of the heating engineers who set the installations to 60 ° C or more "to be sure" ...
My speech (illustrated by the strainer): isolate, isolate, isolate and then see for the rest.

I was talking about vacuum heat pipe sensors: there is no water in it. Obviously, the transport water circuit is drained in the absence of sun, so the water remains at internal temperature of the house and does not freeze: when it goes back, it does not have to take 20 or 30 ° for nothing.

My plan sensor empties exactly the same way, still hot water is stored inside the house, no need for expensive and fragile vacuum sensors to do that.

In addition, with concentrators, we could put a single tube for 2m2 ...

This only collects the direct radiation, it turns out that diffuse radiation represents nearly 50% of the annual energy available in our regions.

Yes, except that currently a stratified balloon costs a fortune, while 2 balloons well insulated standards cost nothing, especially recovered at the dump of the corner ... And increase the storage of hot water.

A standard, cheap, properly used balloon laminates very well, beware of the marketing arguments.

But that's what we do every day while taking a shower

This is an image in response to
it is better to cool the water before returning it to the sensors

I did not find any arguments, so the argument is surprising.

No difference, the nuclear is just used to heat a boiler, it is more complicated because of the dangers of the fuel.

Totally different, it is not a boiler in the nuclear, but a steam generator, the operation is absolutely not the same.

I was at the theory level: the principle of the cycle is always the same, it needs a hot source and a cold source, even if we do not go up to vaporization.

Absolutely not, in the case of the nuclear, it is the second principle of the thermodynamics, principle of Carnot (see on google for more details), which applies (transformation of heat in work), in the case of solar thermal conventional, we are dealing with simple heat exchange, it is totally different (yield of 30% max for Carnot, 100% for thermal exchanges, not counting the losses dependent on the insulation of the elements, go, 95% with the losses).

And as common sense would like to be able to make electric cogeneration with solar at home, the rise to steam becomes an attractive option.

Sorry to have yet to contradict, in the context of cogeneration, for the production of electricity, it is precisely about heat transfer in work (to turn a generator, principle of Carnot), the theoretical maximum expected return being 30 %, the solar collectors, even under vacuum having, at about 200 ° C a miserable yield, the total yield is very probably lower than the yield of simple photovoltaic panels, it is also out of reach of a particular (complex and delicate to implement, fragile [moving parts]).
The total efficiency is good, since the 70% losses are taken up in thermal, with a total yield of 100% (I neglect purely thermal losses, and the efficiency of the alternator), the problem is the energy starting, thermal sensors even under vacuum, at 200 ° C, 5%, 10% yield?
either for 1 m2 = (1000W * 10%) = 100W = (30W electic + 70W thermal).
This is my opinion, which obviously only involves me.


The cheapest energy is the one you do not consume.


cordially
Keke
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bernardd
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by bernardd » 20/12/09, 23:08

Hi,

I did not apply economic reasoning, I did not talk about return on investment, amortization period, I reasoned energy efficiency, for the same price, it is possible to install a larger energy capture area with flat sensor, so to produce more renewable energy, so save more non-renewable resource.


If the price comes into account, it is for me an economic reasoning. If the price of vacuum sensors drops faster, the result of this reasoning will be reversed. To be able to accept this result, you would have to know what prices you are talking about.

In addition, for use in cogeneration, I personally prefer to have the same heat energy at 200 ° C than at 50 ° C.

I also did not talk about the total replacement of the heating system, I argue that a former heating system is often not regulated in terms of energy consumption, the replacement of old regulations is not so expensive and allows you to make substantial savings.


It's certain. But you had only talked about switching to low temperatures, and to my knowledge, that means changing all the radiators, to increase their surface, and most often change the pipes too ...

How does the higher temperature of the circuit increase waste? It is certainly necessary to isolate behind the radiators ... By cons, we can store more heat.

The higher the temperature, the more losses there are.


As long as the temperature of the house does not increase and the losses of the heating system are in the house, I do not see any problem. Possibly problems perceived comfort, with higher temperature contrasts ...


My plan sensor empties exactly the same way, still hot water is stored inside the house, no need for expensive and fragile vacuum sensors to do that.


You talked about drainable planes sensors then? This is not the majority of flat sensor installations, it is worth clarifying this point.

This only collects the direct radiation, it turns out that diffuse radiation represents nearly 50% of the annual energy available in our regions.


If you have measurement figures, I'm interested. But the diffuse radiation will not go up to 200 ° C anyway, we will leave it to the photovoltaic ;-)

But that's what we do every day while taking a shower

This is an image in response to


However, we all throw our hot water in the sewers and this is not at all an image: http://fr.wikipedia.org/wiki/Eau_potable_en_France 2 people consume 30m3 per year ... Between 10 ° and 50 ° C, 1m3 stores 46KWh unless error, and 30m3 store 1380KWh: not negligible so ...

it is better to cool the water before returning it to the sensors

I did not find any arguments, so the argument is surprising.


What is the radiator of a car then? Or the exchangers overheating on solar installations too?

No difference, the nuclear is just used to heat a boiler, it is more complicated because of the dangers of the fuel.

Totally different, it is not a boiler in the nuclear, but a steam generator, the operation is absolutely not the same.


This is true, in one case the water is heated below 100 ° C and in the other case above 100 ° C.

I was at the theory level: the principle of the cycle is always the same, it needs a hot source and a cold source, even if we do not go up to vaporization.

Absolutely not, in the case of the nuclear, it is the second principle of the thermodynamics, principle of Carnot (see on google for more details), which applies (transformation of heat in work), in the case of solar thermal conventional, we are dealing with simple heat exchange, it is totally different (yield of 30% max for Carnot, 100% for thermal exchanges, not counting the losses dependent on the insulation of the elements, go, 95% with the losses).


I was talking about a heat transfer circuit, not the turbine. Having a transfer circuit without cold side is not having a potential difference, so no flow ...

And as common sense would like to be able to make electric cogeneration with solar at home, the rise to steam becomes an attractive option.

Sorry to have yet to contradict, in the context of cogeneration, for the production of electricity, it is precisely about heat transfer in work (to turn a generator, principle of Carnot), the theoretical maximum expected return being 30 %, the solar collectors, even under vacuum having, at about 200 ° C a miserable yield, the total yield is very probably lower than the yield of simple photovoltaic panels, it is also out of reach of a particular (complex and delicate to implement, fragile [moving parts]).


I have already experienced worse prediction :-)



In any case, congratulations for this link, and for the site and the installation represented.
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by keke » 20/12/09, 23:50

Hi,

I have already experienced worse prediction :-)

Either, then good luck.

For the rest, I throw in the towel.

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by MAMO » 20/12/09, 23:59

[quote = "kéké"] Good evening,

[quote] I have already experienced worse prediction :-) [/ quote]
Either, then good luck.

For the rest, I throw in the towel.

cordially
[Kéké / quote]

Hello!

The follow-up in real time of your instal: shock:

It's pure happiness!

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