Talk:Energy density

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I removed the following text from a {{citation needed}} template and replace it with a new {{dubious}} template that points to this discussion. The reason parameter of the template is far too long and includes characters that break the template. Plus, the reason had grown into a discussion (edits: edit 79.182.119.9, edit 140.239.58.226, among others)

Seems high, please check. Using a density of anthracite coal of 1.4g/cc and a specific energy of 32.5MJ/kg, you get 45.5MJ/L instead. - re: yes, correct it please. See wiki Coal_assay#Relative_density. Ideally for most materials we list the highest possible number, the record, then porosity is a separate issue, giving any low value you wish. However as coal above 91% C is classed anthracite, or even 88% C, the rest of the impurities, whether H,S or heavy minerals, affect the sp. gr up or down. Anthracite burns without much flame, not much H or CO or CS2 to pyrolyze out of it. So it depends on your definition of anthracite, if 100%C mineral graphite being excluded from it, then you may still find mined anthracite out there that's well above 1.8 sp.gr., and even mineral graphite may have internal porosity to get listed at <2.1 sp. gr., when ideally it's 2.23-2.26, the difference being attributed to porosity. Listing the highest, the record value and saying everything less is due to porosity or contamination may not be ideal. You can fix it to a more representative, average value. Lignite and bituminous coal by definition are vague compounds containing H, 0, N, etc, and porosity, and listing the "record" lignite or bituminous compounds, and saying the rest is due to porosity would not make sense, so for anthracite we should list the most representative average value from global coals classed as anthracite, as long as graphite is included and listed separately from anthracite. I think using a sp.gr. of 1.5 would be better than 1.4, (and better than 1.8-1.9 which is very high grade but very rare anthracite of relatively low porosity) all these cited values being still very far from 2.2 originally used.

((New Comment : 1.4g/cc is low. even decent bitumunous coal such as Newcastle or Richards Bay standard contract coals get to 27.5Mj/kg at SG's of 1.6g/cc. These coals have excellent volatile contents and hence burn very easily, so their Mj/L ratings should comfortably reach 40 and higher. The energy rating for Bitumunous Coal in the main article is misleading. The quality of coal used there is a low quality power station coal, typically referred to as Run of Mine (RoM) coal, which has not been treated in a wash plant or is the deliberate product of a wash plant set to generate two streams of coal : one for export and one for a power station. Typical Run of Mine coals contain significant amounts of ash (de facto rock) which means that RoM coal seldom has an SG of less than 1.8. Hence RoM coal at 22Mj/kg and an SG of 1.8 results in a Mj/L of close to 40. So the SG used in the main article used for bituminous coal is also dubious.)) — Preceding unsigned comment added by Historiese huise (talk • contribs) 11:42, 4 July 2015

There are still numerous issues with these tables. Inconsistent units have confused at least one reader who got the impression that rubber bands are denser than gasoline. I am going to make some edits to make the tables more readable, consistent and meaningful. I noticed the nuclear table doesn't have density values at all for most substances. I will fill it in with values derived from binding energy and physical density for the liquid or solid state of the substance. I am aware these may not be the conditions that a nuclear reaction occurs in, but I think it is still a valid way of measuring energy density. We can include appropriate caveats and still have values in the table. I think we should adopt scientific notation so that values of different orders of magnitude can be more easily compared. Circuitboardsushi (talk) 13:59, 8 December 2023 (UTC)[reply]

The more I read this article the worse it is. Citation 1 is unnecessary. It is just a working definition that we need to have in order to give values. The reference is a generic guide for SI units which isn't really helpful for affirming the cited statement. We can assume SI units without invoking NIST.

I still don't understand what is meant by "inaccessible energy". It says, "such as rest mass", which should be obvious. There is no indication of any other forms of inaccessible energy, I would assume it might include things like thermodynamic losses depending on context, but it doesn't say.

Then we go on to over explain the rest mass thing, invoking "cosmological and general relativistic contexts." The article doesn't give any examples of these. For the actual examples, rest mass is only relevant to nuclear reactions. It might make sense to include it as part of an explanation of nuclear binding energy. In the introductory paragraphs it doesn't seem necessary to mention it. Circuitboardsushi (talk) 15:25, 8 December 2023 (UTC)[reply]

Note that fission power in non-breeder reactors produces a fair amount of power from generated Pu239. Gah4 (talk) 10:25, 28 August 2022 (UTC)[reply]

The oxidation energy table says there are three specific energies for iron. Iron is an element. There's only one kind.

There's some reason for this involving energy exchange between quantum fields that I don't understand, but to a stupid reader (me), it looks ridiculous. Verdana♥Bold 17:42, 26 May 2025 (UTC)[reply]