Power consumption of a heat pump

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ced75
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Power consumption of a heat pump




by ced75 » 09/11/17, 17:37

Hello,
My goal would be to maintain a breeding pond under glass at a temperature of 18-22 ° C (we are not at 2 ° near) during the spring when the nights and some days we still descend often under the 5 ° C ...
In the most economical solutions I chose the wood stove (and the pellet stove a little more expensive but less restrictive) and then looking on the Internet I discovered air-water heat pumps but I have not all-in...
That's what I understood:
If the comfort temperature is not reached, the pump will run, otherwise it will stop, depending on the settings and the external conditions it will work for example 5h per day and will consume for example 2kw during 5h, or on 2 months at 0.16 € / kwh we would have consumed 600kw and spent 96 € (which is more economical than pellets).
What I think I understood:
The temperature in the room that houses the heat pump does not influence the amount of energy supplied to the pool? and therefore does not influence the power consumption?
I thought that for example the water of my pond being 20 ° C, if the outside temperature drops from 20 ° C the day to 5 ° C at night, then if my local where is my heat pump is 20 ° C then we would consume x times less electricity than if it was 10 ° C in my local ... instead of consuming 2kwh during 5h I consume for example 500Wh for 5h ... and my bill would be 4 times less heavy .. But I understand that when the pump is running, it always consumes the same quantity of electricity, I am mistaken?
If no, are there other more efficient systems?
thank you to enlighten me
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Ahmed
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Re: power consumption of a heat pump




by Ahmed » 09/11/17, 19:01

If the heat exchanger of your heat pump is placed in a room that is warmer than the outside, the performance will be better ... the time it takes to pump the calories from the room (that is to say very little time). The consumption of the heat pump is a function of the temperature difference between the two "ends": the one where you take and the one where you add the calories ...
In your cost, you have to consider the investment and maintenance, these are far from negligible positions especially for such sophisticated equipment *.

* Sophisticated, means here that you will not be able to repair yourself in case of trouble.
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Re: power consumption of a heat pump




by sicetaitsimple » 09/11/17, 19:15

It's weird your thing! Can you be more specific?

- First of all, are you talking about spring? No autumn, no winter?
- Then you talk of pond in a greenhouse: the pond is how many m3 compared to the volume of the greenhouse?
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Ahmed
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Re: power consumption of a heat pump




by Ahmed » 09/11/17, 19:29

If it's just for a limited period, the investment cost becomes the limiting factor!
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Re: power consumption of a heat pump




by sicetaitsimple » 09/11/17, 19:42

Ahmed wrote:If it's just for a limited period, the investment cost becomes the limiting factor!


Yes, that's what I want to know with my questions!
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ced75
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Re: power consumption of a heat pump




by ced75 » 09/11/17, 21:13

I do not necessarily want to reveal the details of my project but let's say that for some species the temperature is more important for reproduction and "the young" is in spring than for the growth of adults which ends at the end of autumn. The heating will therefore be 3 months, 4 months max and in a sunny day in a greenhouse we will not often need additional heating but it is especially for certain days and at night ...
For now I am on a prototype walipini type buried greenhouse to limit heat losses and a pool of 30m3 but again I do not want to reveal much more, especially that it should not stop you from clarifying me on the operation of an air-water heat pump?

If the heat exchanger of your heat pump is placed in a warmer room than the outside, the yield will be better ... the time to pump the calories from the local (that is to say very little time).


So I make a proposal: we bury the room (we isolate it with straw bales on the sides and the top) and we put a pebble tunnel at 30cm (distance to be determined more precisely) underground under the local that we would heat with solar collectors on a sunny day. we should have 20 ° C most of the time in this room and even if we have several days without sun, given the lateral and top insulation of the premises we should not go down a lot in T ° C in the room and continue to recover calories from below no thermal phase shift.
What do you think of my idea? interesting not? :) What size of local in m3 would it take for a pool of 30m3?
And for those who can continue to explain in more detail the operation at the level of the power consumption of a PAC air-water depending on the temperature of the location where is the cap I am taker. If you have numbers or examples too, by how much would the performance be improved? how much would the decrease in power consumption be? etc ...
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Re: power consumption of a heat pump




by sicetaitsimple » 09/11/17, 21:47

ced75 wrote:. The heating will be 3 months, 4 months max and sunny day in the greenhouse we will not often need a heating supplement but it is especially for some days and nights ...


I respect your desire for confidentiality, but as we describe your project, just drop the idea of ​​PAC.
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ced75
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Re: power consumption of a heat pump




by ced75 » 10/11/17, 22:47

sicetaitsimple wrote:
ced75 wrote:. The heating will be 3 months, 4 months max and sunny day in the greenhouse we will not often need a heating supplement but it is especially for some days and nights ...


I respect your desire for confidentiality, but as we describe your project, just drop the idea of ​​PAC.


Hmm ... I may not have given enough details: if you want to heat the air in the greenhouse it is 600m3 ... the water is several basins for a total of 60m2 evaporation surface with the air ... the most important for the critters is the temperature of the water around 20 ° C ... would not it be better to heat the water or under the basins?

Small comparison for the economic aspect:
- the wood stove: to heat 600m3 not insulated (greenhouse buried but loss by the roof ...) we should provide say 60kw so several stoves, an investment of 1000 € and a consumption (0.035 € / kw) of say 300h / year is 630 € of wood per year. Add to this the constraints of wood supply, storage, human availability to supply the fire otherwise the temperature of the water will be a sinusoid and we will move too far from the setpoint! So of course you will tell me for these constraints there are automatic pellet pellet ... yes except that it is 6 times more expensive to invest: 6000 € to provide 60kw and the cons is 0.08 € / kw be 1440 € / year ...
- the air-water heat pump to heat 60m3 basin 20 ° C is 2000 € investment (and a little logging the thing I think I can install it myself). The temperature of the water does not oscillate (compared to the wood stove) if inverter / regulator and good settings and no supply constraints, it turns alone! At the worst cover the basins for cold nights with tarpaulins ... well the cons: say 6h / j is 12kw / d, on 90jours: 1080kw 0.16 € / kwh is 172 €!
I let you do the calculation of the depreciation: after 2 years only the CAP can become more profitable than the wood stove and the 3 start times more economical than pellet stoves ...
The heat pump uses electrical energy, which is more expensive than wood, however, thanks to its energy performance, it produces on average 3 kWh of heating with 1 kWh of electricity. On the other hand, the wood heating modes benefit from an inexpensive primary energy, but 1 kWh of wood produces a maximum of 0,8 kWh of heat.
So, sicetaitsimplewhy should I forget the cap?

Otherwise, for those who wish to explore new trails with me know that I have studied the pebble tunnels:
Solar-thermal / thermal-storage buffer-in-the-floor-by-rollers t9567.html
heating-isolation / storage-de-la-heat-t9878.html
I also noticed that many econologists had trouble in the beginning to understand how it works.
I add a link that I found on the internet that I think is well done:
https://boiscorde.weebly.com/tunnel-agrave-galets.html
The problem for my case with pebble tunnels is to heat March / April / May ... the phase shift is 3 months, little solar energy to recover in December / January / February ... and if we want increase the phase shift this becomes complicated for several reasons:
- the trenches at 4-5 m depth it starts to get complicated at the level of work (especially for what I want to do :-)
- the lateral losses in the solid ground which become too important at this depth
- the calculation of the exact distance which becomes complicated: the law of the square makes that if one multiplies the thickness by 10 one multiplies the time of penetration by 100 ...

If not another track to explore: I will have a flexible rainwater tank 50m3, if I bury it a little, I isolate it cheap with straw boots, etc ... how many months could I keep the heat to recover it from March? what heat loss? Will I have enough to heat my pond 60m3 until May?

PS: I like your site and its stakeholders who are also looking for solutions that are sustainable and ecological :-)
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Ahmed
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Re: Power consumption of a heat pump




by Ahmed » 11/11/17, 08:36

If temperature regularity * and automatic operation are decisive criteria for you, plunging resistances would be more judicious than the heat pump; especially since nothing prevents you from insulating the bins a little ... You can also hope to reduce electricity consumption with an old (=> cheap) wood stove that would be in operation when you are available and admiring your fish ... :D

* I think that the inertia of the basins would hope for a relative stability of the temperature, whatever the mode of heating.
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Re: Power consumption of a heat pump




by Lolounette » 11/11/17, 09:46

for me to heat the water is indeed the most logical, the greenhouse only serving as insulation above the basins (if you put 2 plastic layers on each other separated by a few cm is even better level insulation level) ...

In addition to the tunnel pebble another idea comes to me following other discussions that we had elsewhere on the forum: why not a manure-based heating system being composted as has been practiced for hundreds of years in market gardening to obtain hot diapers?

I can imagine a basic heat exchanger made of pipes winding in a pile of decomposing manure (isolated from straw boots?) and then in the basins, with a simple recirculation pump whose flow would be controlled by thermostat ...

Fresh horse manure is the most effective for this purpose and readily available from equestrian centers.
and the resulting compost is also easily valued ...
to calculate the size of the manure pits necessary to maintain the temperature of the basins must be feasible, but in all cases a good insulation of the air above seems to me essential ...

you can even consider recovering the bio gas released by your manure pit and use it to heat your water also with a small boiler : Wink:
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