Environment & Energy

powerplants, including nuclear plants (for the most part, although exceptions exist), operate on the Rankine steam cycle, which is thermodynamically limited, typically on the order of 33% efficiency.

Batteries intrinsically also are involved in thermodynamic degradation, although the extent to which they do so is very much a function of their design and chemistry. How much energy they lose - they obviously do degrade exergy since they get hot - involves a fair amount of analytical complexity. I covered some of the issues in this space here:

Pesky Thermodynamics: The Mathematics of Wasting Energy by Storage in Li Batteries.

In an Rankine nuclear plant there are multiple energy transitions, each of which, subject to the 2nd law, destroys exergy, nuclear to thermal, thermal to mechanical, mechanical to electrical, transmission losses, electrical to chemical, chemical back to electrical, electrical to mechanical. (6 conversions and one transmission loss)

A chemical fuel skips multiple cases of these steps and consists of nuclear to thermal, thermal to chemical, chemical to thermal, thermal to mechanical. (4 conversions)

On inspection, a synthetic fuel should be superior. I note that the hydrogenation of carbon dioxide to fuels, either FT or methanol or DME, is an exothermic reaction. In theory, if not in practice, this property would conceivably allow for some exergy recovery.

Over the years, I've written extensively on DME in this space. Its cetane number is relatively high, which is why it first gained attention as a substitute for diesel fuels. A problem concerns its chemical compatibility with seals used in existing engines, thus conversion work would be required. Mack/Volvo has actively considered this issue, and have run diesels in pilot settings on the fuel.

The heating value is somewhat volumetrically and density lower than other fuels, but this is offset by its high critical temperature, well above the boiling point of water, and thus ease of liquefaction, its chemical inertness with metals (although not all polymers, as mentioned), its very low half-life in the atmosphere, roughly 5 days, leading to a lack of climate forcing, and the ability to drop into existing infrastructure, albeit with some minor modifications. It has also excellent properties as a refrigerant, albeit a flammable one.

The main industrial use at present is, believe it or not, as a replacement for CFCs in spray cans.

A few, hardly comprehensive, examples of my own writings on DME are here:

A Survey of the Number of Papers Published and Patents Filed on "Sustainable" CO2 Conversion Processes.

An interesting reactor H2O free approach for the direct synthesis of the wonder fuel DME.

Zeolite Catalysts for the Low Temperature Production of the Wonder Fuel DME.

I'm sure there are many more cases of my arguments involving the case accessible by use of DU search functions. I've been advocating for this fuel for a very long time.

Regrettably, it is often the case that superior technologies do not replace inferior technologies, some of this a function of marketing (for example the fossil fuel industry's marketing of hydrogen in their thermodynamically nightmarish bait and switch) or, in an obvious case, the marketing of any electricity generating scheme that is not nuclear, since nuclear is obviously - on very little reflection - superior to everything else in terms of sustainability, low environmental impact, safety, material and land use, longevity and reliability.

I know the scientific literature features abundant reference to DME, my favorite of all of the many thousands or tens of thousands of references, the one to which I often refer, my favorite, being this:

In 2011, the late great Nobel Laureate George Olah proposed a closed carbon cycle to address the on going and accelerating tragedy of climate change: Anthropogenic Chemical Carbon Cycle for a Sustainable Future George A. Olah, G. K. Surya Prakash, and Alain Goeppert Journal of the American Chemical Society 2011 133 (33), 12881-12898

This paper refers to methanol as well as DME. DME is superior to methanol since it is easy to remove from water and is relatively nontoxic, the main physiological issue being mild anesthesia in high concentrations, similar to nitrous oxide and ethyl ether. Most industrial routes to DME proceed through methanol, although the direct conversion of carbon dioxide or monoxide to DME via hydrogenation is known.

I hope you find this useful.

Thanks again for your question.