Diesel Engine  Efficiency = 20%
Engine  Efficiency = 40%

What does it mean?
                       that at the same applied caloric energy the Stirling engine gives the double of  mechanic energy.
But there is much more!

Check one versus the other:

                        Diesel                                             Stirling
Type                 internal combustion                                     external  combustion
Combustion      incomplete                                                 complete
Fuel                  diesel  and a few others not of easy use        any  type: liquid  gaseous  and solid
Combustion  emissions
2 CO  H2O  diesel unburnt oil,                CO2 H2O from pure  hydrocarbon
                        heavy hydrocarbon 
Efficiency         20%                                                           40%
Acceleration    mean/high                                                    low
Stability           low                                                             high
 complex                                                      simple
Greasing          forced                                                         unnecessary
Maintenance    frequent                                                      rare

Note :
Though in theory other fuel types are possible, the Diesel engine, for  maintenance and time resistance reasons,  is used exclusively with heavy oils, mineral  (from petrol) or, just from a short time, partially biologic (colza as addictive).
The Stirling engine, as the cylinder is heated externally,  can use any type of stuff that can give heat, in particular:
mineral oils (gasoline or diesel),   biologic liquids (alcohol, various oils), solids (coal, paper, wood,  disposal, excrements) e gaseous ( methane butane/propane gases, hydrogen) and at the end  direct energy (sun).

As the combustion is slow relating to Diesel one (that is compelled to burn the fuel in less an half a turn  of the engine) this is a complete mode, that means it uses completely the energetic properties  of the fuel.  In the Diesel engine a part  of the energetic properties is dissipated to create heavy and  complex compounds and another part is not used because the combustione is partial. In particular, the  combustion of a pure hydrocarbon  (H
yCx,) where x and y  are an appropriated number of carbon and  hydrogenum athoms)  + O2 (air oxygenum) if it is complete gives  CO2 (carbon dioxide) e H2O (water) , on the contrary in incomplete mode  it gives H2O  CO2e CO (carbon monoxide, highly poisonous). The CO is dispersed in the air, and it is impossible to burn it further to give the remaining missing part of  CO2 , consequently it is wasted also the energy that would be available in this further step.

BTW: The
 CO2 (carbob oxide), if from one side is the main cause of  the greenhouse effect, on the other it is very easy to recycle, it is sufficient to plant more trees!

If the energetic efficiency  (output energy/ given energy)  is about the double for the Stirling engine vs. the diesel one, more high is the ratio: output energy /given resources (as weight).

More,  you are not obliged to use just only type of fuel with Stirling engines.Let's see some and their advantages:

Alcohols: methanol, etanol, butilic ecc.
Low cost  Combustion products: H2O and CO2
Natural Gas (metane) e LPG (propane, buthane)   Low cost.  Combustion products: H2O and CO2
 Hydrogen   Cost from nothing to low, (depending on the generating method)  Combustion products only and esclusively water (H2O)
Waste (for instance burnt in an incinerator) Nil  The combustion products are that generated in any case by the incinerator.
Paper, wood and derivatives    Low or nil Recyclable cinders for agricolture.
Solar energy  Nil No combustion, no product.

As you can see, the Stirling engine is  absolutely ecological. With an impact on the environment from low to nil, it should replace Diesel engine in all the fields, excluded perhaps automobilistic one where is requested an high capacity of acceleration.
In particular:
Electric power generation in the electro-thermic vaults and power back-up systems of little as of high power. Earth moving machines and alike. Not electrified  railways. Irrigating pumps and devices for a continuous use at less or more constant speed. Etc.etc..

The informations are not few and nowadays the industry offers engines for every use. It is sufficient surfing internet to have an idea.Try on Google the key (double quote included)  "Stirling motors" You will get more then 14000 sites in english  and many in all the languages.
To substitute the Diesel engines in the electro-thermic vaults actually in function would keep us safe from energetic crises and could make the bill for electricity a little lighter, giving a little better chances to industries and families.

Why not to do?

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