The use of diesel fuel for ignition requires a second injection system, adding cost and complexity.

Conventional spark ignition won't do, but one has to wonder about the capabilities of corona ignition as a substitute.  If it can provide the same performance, it would certainly do it at a large improvement in cost and ease of repair.

Losses for DME are a lot higher than that.  Oxidizing methane to MeOH drops the heating value from 889 kJ/mol to 726, and conversion of MeOH to DME is exothermic too.

DME as the ignition fuel with NG as the main fuel avoids most of the energy penalty.

@E-P,
Actually, only a single injector is used that combines both LNG and diesel fuel. Quite clever, ain't it?

@A D,
Too costly? What is more costly is the continuous use of diesel fuel. NG is much cheaper.
New NG infrastructure can be built to be H2-compatible for future delivery of H2, so that NO new H2 infrastructure will be necessary upon the conversion to the eventual H2 economy. Even more clever, ain't it?

@E-P,
So, in constructing an H2-compatible pipeline, you make the pipe bigger than would be required of NG, to accomodate the larger volume of H2 in the future. Most of the cost of pipeline is from labor, planning, right-of-way, while material cost is only a small proportion. Making the pipe bigger would incur only a modest increase in cost. H2 utilization at end-user level is more efficient, for example, home or building CHP FC, and FCV, so it would offset the energy cost in comparison to NG.

Overall cost from future renewable-energy H2 will get lower than NG at a certain point in time given the trend that renewable energy will cost less and less since it is an inexhaustible source, while fossil-fuel will cost more and more being, a finite resource that will be harder and harder to extract.

Engineer-Poet,

Is it correct comparison units kJ/mol? On my knowledge the amount of mol depends on chemical reaction formula. Besides DME easy could be produced from coal, methanol or biomass and even blended at some extent with LPG. On other hand I do not have any feeling what LNG losses are related to cryogenic cooling and keeping contained in the fuel tanks. Ofcourse CH4 could be produced from biomass as well but that is very complicated process.
DME issue is very intriguing and it bothers me - why it is so little attention on this site when H2 madness is in circulation every day? Are Sweeden and China seriously considering shifting their heavy duty vehicles to DME? DME vs CNG and DME vs LNG comparison would be of great benefit.

@Darius,

"...H2 madness...?"

With global temperature escalating within the latest decade that coincide with escalation in CO2 release from developing economies, GHG's will have to be phased out in the near future, and that include CO2 and methane (NG and biomethane). Significant leakage from NG pipeline system will have serious consequence by causing further global warming.
That means that H2 from renewable energy will be left standing. With all the knowledge about H2 handling and technologies for production of H2 from renewable energy, we will be in good shape.

BTW, compressed H2 can be substituted for LNG in this HPDI technology. Gaseous H2 injector can incorporate about 5% of diesel fuel and released all in one jet at TDC to accomplish diesel-initiated compression ignition of H2 gaseous fuel. Instead of 18:1 compression ratio, the CR can be reduced down to 12-14 because of the introduction of significant volume of H2 (15%-30% of air volume, depending on equivalence ratio) at TDC. This reduces work of compression while allowing the high pressure of compressed H2 to do work on the piston, partially recuperating the work required to compress the H2. With good turbocharging and turbo-compounding system we may see break efficiencies as high as 50-60% tank-to-shaft for heavy-duty application.

With all the talk of global warming, what are we going to do about it, except kept bad-mouthing H2?

Again, E-P, H2 will come from renewable energy (moments of surplus of solar, wind or even nuclear energy). Use CNG for now, then, when NG will be phased out, use H2 instead. H2-compatible CNG injectors and H2-compatible NG equipments can be used with H2 later. A wisely-planned NG infrastructure that is designed to be H2-compatible will not need to be changed to handle H2 in the future.
However, switching from CNG to H2 will require lowering of engine compression ratio due to the larger volume of H2 injection needed. Therefore, CIDI engine that is designed to be run on both NG or H2 without modification will need a variable compression mechanism. A variable-duration intake valve mechanism can be used to adjust CR, or a more complex VCR mechanism can be used to avoid power loss in the former method.
Truckers driving over remote areas without frequent H2 filling stations may opt to fill up with CNG and pay a price premium (tax), while those who are more price concious can fill up with H2 at lower cost.

It may sound ludicrous now to say that H2 will eventually be less expensive than NG, but one can recall the very high prices of CFC for recharging A/C system after CFC was being phased out due to environmental concern.

@E-P,
There have been articles here in GCC that showed how surplus wind and solar electricity used to make H2 to be stored in the existing NG pipeline system. You can look in topics section and look for H2.

Now, if the entire NG pipeline and underground cavern system is upgraded to make it 100% H2 compatible, then we will just simply replace the NG with H2 gradually. Commercial-grade electrolyzers now exist to produce H2 from grid electricity. The H2 can be produced already compressed to several thousand psi without using mechanical compressor. H2 production requires water, but so do all living things. Where there will be living things, there will be sources of water.

The technical issues involving H2 storage and pipeline have been solved by the petroleum refining industry that requires a lot of H2 in the hydro-cracking of petroleum sludge and petroleum tar (from tar sand) to produce liquid fuels, and in the production of ultra-low sulfur gasoline and diesel fuel that is required for modern transportation.

The next logical step is to bypass all these complexities of petroleum refining and just use the ultra-pure, FC-grade raw H2 straight from the electrolyzers. The electrolyzers can be placed anywhere as long as there are electricity. Modern human cannot function without electricity.

The H2 can be stored in existing NG well once the NG pipeline will be made 100% H2 compatible.

At what cost for H2 produced from renewable energy? At $.04 per kWh of electricity, H2 will cost around $2 per GGe, including the depreciation cost of the electrolyzer, which does not require precious metal and hence can be made cheaply. To calculate the cost of H2 from fossil fuels, one must add the external costs of environmental and climatic destruction, economic disruption due to energy shortages from geopolitical disruption, and preservation of the world-wide unemployment crises.

Hydrogen from renewable energy is the future of humanity, for at least 3 purposes: Energy security, Job creation, and Environmental preservation.

It would take a heck of a lot more storage than we use now, both because hydrogen stores about 1/3 as much energy as NG per unit volume and you're implying a large increase in consumption as well as substantial seasonal variations in production.

There's also the issue that the geology suitable for such storage is a regional phenomenon, while the use of H2 as the universal vehicle fuel requires that it be distributed everywhere.  This means a lot of pumping losses to and from the storage area, overhead that's exacerbated by the greater pumping work required to move hydrogen compared to NG (as a fraction of its energy).

When you add all of those things up, you've got a really good case for just reforming NG.  That's why I think H2 is the gas industry's trojan horse.

If you really want to get rid of fossil fuels, nuclear power is the way.  There's no economic case for steam-reforming natural gas to electricity.

Using larger pipes means you have to spend the money for larger pipes.  You can't win that one; Nature has the last word.

As for the relative merits of H2 versus molecules containing carbon, I'd like to continue the discussion here.