Generic gray energy calculation method

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Generic gray energy calculation method




by Christophe » 27/02/08, 12:29

Looping has recently proposed a calculation method that I find very interesting to determine the gray energy necessary for the construction of any "thing" whether it is wind turbine, house or car (for example) ....

This method starts from the sale price and assumes that 100% of the sale price = gray energy.

By knowing the price of the energy used by the manufacturer in question (fairly easy), we therefore obtain a large increase in the gray energy for this product.

By applying different correction coefficient depending on the manufacturer and especially on the type of product, it would therefore be quite easy to develop a method, admittedly approximate but so fast, calculation of gray energy for all areas of activity!
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by Christophe » 03/03/08, 10:43

Small up for those who missed this message.

I propose to make some estimate with the following objects:

a) photovoltaic solar
b) car
c) solar thermal

Assuming, for example: 30, 50 and 100% of the purchase price = gray energy.

The reality is probably below 30%.

For a new car, for example, I once heard that it was equivalent to 30 to 000 km.

For solar PV, we recently read that it was about 2 years of energy return ...

With this method we could see if it was in these waters there and how much it represents% ...

ps: looping your opinion would be welcome, it's your method after all :)
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by loop » 03/03/08, 13:15

Hello

I think that for the first stage of my demonstration, I will use iron (or steel) as raw material

step 1: Transformation

Note that the kilogram of steel, in the form of a semi-finished product (sheet metal, tube, bar, etc.) is bought for 1 euro (excluding purchase price in industry)
I don't think I can say too much nonsense when I say that steel is produced from an iron ore and coke (coal)
The steel at the outlet of the blast furnace is at 1500 ° C
The specific heat of iron 440 J / (Kg.K)
The only energy expended to heat 1 kg of steel from 20 ° C to 1520 ° C is calculated as follows:

1500 x 440 = 660 J with 000 MJ = 3.6KWh
Total = 660000 / 3600000 = 0.183 KWh

The simple rise in temperature of 1 kg of metal alone requires 0.2 KWh. This figure is not very high but it should be understood that the ore and the coal were transported.
That the steel will be worked mechanically, before being transported again, stored, then sold, etc.
Imagine the distance that 1 kg of steel travels from the extraction to its final use, and the energy it takes.
If some want to estimate it

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by Christophe » 03/03/08, 13:34

Mmmm I do not quite understand your message because if we want to make the energy balance of each component of a car we are not out of the inn ... then as much to seek if the manufacturers have reports available publicly.

On the other hand, your calculation is interesting in the sense that it shows that gray energy represents around 20% of the price for raw steel!

And again you did not take into account the yields of the installations.

In the end for a finished steel product, I think we can double this value: transport, redesign or retransformation, final machining ... or 40% of energy cost! It's more than I would have thought ...

Good as soon as I have a moment I attack an excel file of estimate.
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by loop » 04/03/08, 21:07

Bonsoir

Sorry, but my demonstration with a raw material like steel .... is zero : Cry:
I had taken the example of steel because it is still a very widespread material in any type of construction (automobile, building ...)
I expected to reach a considerable energy to melt 1 Kg of steel, and in reality, only 0.2 kwH to raise its temperature by 1500 K
Reminder: the rule was 1 euro bought = 10 KWH spent
in my example, the theoretical fusion energy represents only 2% of the price
Indeed, we can qualify because the efficiency of a blast furnace must be catastrophic but even with a factor of 5, this only brings us to 1 KWh consumed
Now I sincerely think that transport and peripheral operations are much more demanding

In another subject we talked about 0.01 L of fuel spent per ton and per km transported
Our kg of steel would easily have traveled a few thousand km before ending up at the end user, and will have undergone multiple mechanical manipulations.

What is more difficult to assess is the expense of all the infrastructure, equipment, buildings, heating, etc.
Energy costs are often buried in corporate overheads, so difficult to pin down and reallocate in the price of the end product.

So I still have a job to find a concrete example!
: Cry:
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by Christophe » 22/06/08, 11:45

It is not zero your looping method and above all it gives an "absolute and increased" order of magnitude.

An anti-compact fluorescent troll has appeared on forums this morning and apparently he would have done better to read your method before opening it: https://www.econologie.com/forums/post84913.html#84913 : Cheesy:
Last edited by Christophe the 22 / 06 / 08, 12: 45, 1 edited once.
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by Flytox » 22/06/08, 12:38

Hello Looping
loop wrote:I had taken the example of steel because it is still a very widespread material in any type of construction (automobile, building ...)
I expected to reach a considerable energy to melt 1 Kg of steel, and in reality, only 0.2 kwH to raise its temperature by 1500 K
Reminder: the rule was 1 euro bought = 10 KWH spent
in my example, the theoretical fusion energy represents only 2% of the price
Indeed, we can qualify because the efficiency of a blast furnace must be catastrophic but even with a factor of 5, this only brings us to 1 KWh consumed


By calculating with the specific heat effectively this does not take into account the efficiency of the blast furnace and all the post-treatments in the steelworks, and as a semi-product in the various manufacturers. Everyone adds their layer of energy expenditure (heat treatments with heating resumed from room temperature, solution treatment, case hardening, quenching, tempering, etc.).

For all the somewhat elaborate (mechanical) products, I suppose that the energy expenditure generated by the transformation of the manufacturers is equivalent to that of production at the level of the steelworks. :frown:

In this link some elements of energy cost:

http://www.debat-energies.gouv.fr/enjeu ... acier.html

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by minguinhirigue » 22/06/08, 19:17

The method is interesting but I am not sure that it is right for products with high added value. When comparing a wooden profile window and a PVC profile window, PVC will have consumed an enormous amount of gray energy and will nevertheless have a lower fiduciary value.

The economy and the ecology will be linked by almost linear relationships on the condition that the product is not a high added value. For raw materials and their simple derivatives (profiles, molded parts, processed materials) this rule can be interesting to try to generalize, just to get orders of magnitude quickly.

I will try to stick to the problem to compare different transparent products in the building.
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by Christophe » 22/06/08, 19:23

Yes minguinhirigue, the more complex the product, therefore at high VA, the more approximate the method becomes.

But in any case it allows to give an absolute increase.

Thus, we can consider that 30% maximum of the price of a car is embodied energy (any form of gray energy = "from the mine to the customer") to have an order of magnitude.

Obviously only precise figures by branch of activity would allow this value to be refined, but since the sale price (and its evolution) is necessarily proportional to the manufacturing costs (and therefore, among other things, to gray energy) for me c is a very good method due to its simplicity ...
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by gilgamesh » 22/06/08, 23:12

I come from a subject where I affirmed that it was even very ecological to keep his cars until the end of life. According to the logic of Cristophe's 30% gray matter, a car of 30.000 euros would correspond to 9000 euros of gray energy costs or 90 KW / H - by calculating an average consumption of 000 liters of fuel per 6 km of a recent car and even giving a supplement for the gray matter included in the same fuel, saying 100% the energy costs of the vehicle would correspond to 50 km traveled. That means that we actually polish much less by rolling old rotten boxes. My Saab 100 has 000 km and it does not complain at all and with the vortex I arrive at 9000 liters on the highway at 400.000 km / h - maintain it costs me insurance included 8 cêntime per kilometer and the purchase (140 euro with 5 km and 4000 years) it's not even 150 miles long. even with fuel at 000 euro liter I arrive at a price of less than 13 cents per kilometer traveled. Often we are led to believe that it is a good deal to change a car because the news would be more economical, less polluting and more reliable - but precisely we find that this is not at all the case !!!
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