Calculating your actual DJU (heat balance)

[Christophe]

I'm trying to see if it's possible to easily calculate your actual DJU (Degrès day unified) through USB weather station with recording and memory of that type: https://www.econologie.com/shop/station- ... p-347.html



It allows to export the raw data under .txt or .xls, there are 4800 measurement points with an adjustable recording frequency, which allows to record 100 days in a row with the default setting (30 minutes ):




Here is where I am:

a) To start we recover the 2 official methods of calculation by Météo France:
https://www.econologie.info/share/partag ... Bt6P39.pdf

b) It is therefore necessary to recover the minimum and the maximum of each 24h to be able to calculate the "official" method.

But one could not, more realistically, average the inside and outside temperatures of the day and subtract them?

c) The official method does not take into account wind chill. A weather station with anemometer usually calculates it (Windchill in english), so is it wise or not to take into account this value rather than the outside temperature value?

So I will test for a few days (we just received the station so I have not enough records) the following 4 methods and see if it sticks or not:

a) official weather DJU
b) Official DJU pro energy (not on it is different from a) currently see definition)
c) Real DJU according to average method = average internal temperature - average outdoor temperature.
d) Actual corrected DJU = Average internal temperature - Mean windchill corrected average temperature

In my opinion, the most realistic method = d) but if the pro weather does not take into account the wind chill is that there must be a (good?) Reason right? Maloche must have his opinion!

Well it's not too time to calculate DJU but good (I will consider that they can be negative) ... but the method will be there for the winter!

ps: for those who have never heard the term DJU: http://fr.wikipedia.org/wiki/Degr%C3%A9 ... nifi%C3%A9

[Did67]

Two remarks:

1) DJU: the big advantage is that it is "standardized" ... So an "unofficial" DJU why not, but what interest ...

2) Another thing would be to calculate a "climatic demand" (I would look for a better name another time); that is to say a "number" which quantifies the loss of calories of a house due to the climate ...

And there, it would perhaps be necessary to "integrate" the differences of interior temperatures / exterior temperatures with a finer grid than the day (hour by hour?), Taking into account the wind (but I am not sure that the "temperature felt "is valid for buildings! The nature of the surface, evaporation, etc ... play a determining role; of course, the wind and turbulence increase the losses, but must be sure that the" felt temp "does not is not configured for living beings taking into account the perspiration through the skin?) and taking into account radiations ... (for the same external temperature, the "need" will not be at all the same depending on whether there is sun or not - knowing that this will depend mainly on the design of the house!)

With this "demand", taking the fuel consumption of each house for the season in question, we would then have a realistic estimate of the intrinsic "insulation factor" of each house (otherwise more accurate than the calculations of DPE all the same. very pifometric).

It would be to take the problem of the insulation of the house from the other end: knowing that in my colander I lost so many liters, knowing that the "difference in average level" was so much and so much, I know how big are the holes in my colander.

And above all, it would clarify or objectivize a little debate on the relevance of a particular mode of heating (where the forumPeople keep comparing things that are not comparable - "I consumed 3 steres", "and" I only 5 tons of pellets ", while neither the" climatic demand ", nor the characteristics of the houses. are similar)

[Christophe]

Two remarks:

1) DJU: the big advantage is that it is "standardized" ... So an "unofficial" DJU why not, but what interest ...

Completely agree but it is for a purely "intellectual" purpose that I propose the 2 other methods.

I have already made some calculations and the differences between the 2 approaches are important, for the same day (11 June 2010) we would have had at home, in the same order as above but in absolute value (otherwise it is either 0 is currently negative: logic does not need heating):

a) DJU 20 ° weather (20 ° C inside) = 3
b) DJU 20 ° pro = 3.1
c) Real DJU = 15,98
d) Real DJU Wind = 15,98 (not enough wind to influence)

The gap is already so large that I already doubt "my" method ...

2) Another thing would be to calculate a "climatic demand" (I would look for a better name another time); that is to say a "number" which quantifies the loss of calories of a house due to the climate ...

This is exactly what I have been "campaigning" for for a few months: to set standards not in kWh / m².year but in kWh / m².DJU!

And there, it would perhaps be necessary to "integrate" the differences of interior temperatures / exterior temperatures with a finer grid than the day (hour by hour?), Taking into account the wind (but I am not sure that the "temperature felt "is valid for buildings! The nature of the surface, evaporation, etc ... play a determining role; of course, the wind and turbulence increase the losses, but must be sure that the" felt temp "does not is not configured for living beings taking into account the perspiration through the skin?) and taking into account radiations ... (for the same external temperature, the "need" will not be at all the same depending on whether there is sun or not - knowing that this will depend mainly on the design of the house!)

Great!!! Do you take care of finding the formula that goes well?

For the wind I still have a doubt but I think that a house, after all, is a "big blanket" that we put over our heads and therefore that it behaves like a "skin" and that exchanges are necessarily increased when there is wind ... and therefore should be taken into account ...

And above all, it would clarify or objectivize a little debate on the relevance of a particular mode of heating (where the forumPeople keep comparing things that are not comparable - "I consumed 3 steres", "and" I only 5 tons of pellets ", while neither the" climatic demand ", nor the characteristics of the houses. are similar)

Passing in kWh / m².DJU would be a way to limit this ... Although the DJU will be calculated, obviously, with the same instruction, since the DJU is not necessarily 18 ° C.

ps: I could be wrong but it seems to me that you were against this method of calculation some time ago ...

[Did67]

ps: I could be wrong but it seems to me that you were against this method of calculation some time ago ...:?:

Oh no ...

1) I do not remember! Honestly (which proves by the way that I write too much - and especially too much bullshit!)

2) if yes, either I had misunderstood something, or I had not understood anything at all, or I had misunderstood something ...

[I do not think I did it just to contradict you!]


3) In any case, I agree with you that this is the only way to objectively compare two methods of heating the same house, in a short time ...

Method A: 25 years with such method then 25 years with the following and we compare the averages (assuming that global warming is only an illusion)

Method B: such heating such year / "climatic demand" of the year compared to such other heating the following year / "climatic demand" of the following year ...

If not, what to compare my 5 t pellets this winter 2 000 2007 fuel oil or more exactly to deduce what? That winter has been colder? that the pellet boiler is less efficient? or both ?

It remains to find the right formula!

[Capt_Maloche]

Nice

you say that there is an interest to calculate his DJU

my real DJUs in my area are much lower than the regulatory DJU, it's at home he made -20 ° C this winter

Nice weather station Toff!

[Christophe]

It remains to find the right formula!

We'll do it with Maloche who should be of good advice on this one, is not it Pascal?

[Christophe]

Here is a screen shot of yesterday's wind, 14 July 2010, we can clearly see the peak corresponding to thunderstorms (with us it blew well but it was not much compared to elsewhere):



And the outside temperature for the month of July (from 7 to 15):



And as promised, here are 2 examples of raw data logging exported in .txt and .xls from 900 and 800 raised about: https://www.econologie.com/shop/file/Sta ... _reels.zip

File available on the product sheet also: https://www.econologie.com/shop/station- ... p-347.html