Energy content, volumetric

Long-distance transport has a large impact on the total costs. Compared with other fuels, the volumetric energy content of hydrogen is comparatively low, which makes long-distance transportation less efficient. Therefore, if natural gas or hard coal are the considered feedstock for hydrogen production, it would be better to import the feedstock and produce hydrogen at (or near to) the place of use. 

Liquid Hydrocarbon Fuels Having High Volumetric Energy Content in J33 Single Combustor, Natl. Advisory Comm. Aeronaut. RM E50H28 (1950). 

The diesel engine is more attractive for conversion to producer gas as the reduction in power and efficiency is less compared to an Otto engine. This is due to the higher compression ratio of the diesel cycle and also the operation conditions with high excess air ratios which reduce the difference in the volumetric energy content of diesel/air mixtures and producer gas/air mixtures. 

The density of the liquid is very high at around 1.2 kg/litre conqtared to light fliel oil at around 0.85 kg/litre. This means that the liquid has about 42% of the energy content of fuel oil on a weight basis, but 61% on a volumetric basis. This has inplications on the design and specification of equipment such as pumps. 

The volumetric hydrogen production rate is first converted to 0°C and then multiplied by the culture volume. The obtained volume of H2 at 0°C (ml) per unit of time (h) is multiplied by the energy content (3.05 cal/ml) and thereafter divided by the irradiation area. The obtained energy produced is expressed by cal/(h.m2). On the other hand, the light energy consumed is easily converted from W/m2 to the same unit. 

Thus, by using mixtures of natural gas with hydrocarbon fuels, we can maintain the volumetric energy density of the mixture at values close to those of the hydrocarbon while adding significant amounts of natural gas to the hydrocarbon fuel pool, thereby incrementing the total energy content by 10% or more, depending on the pressure. 

Hans Joachim Papst von Ohain ran his first turbo engine in 1936, on hydrogen and thus he has shown that turbo engines can be operated on hydrogen. However he did not choose this fuel at this time for environmentally friendly reasons but because of its very high reactivity, which enabled him to start the combustion process with a lean mixture in the combustion chamber. Afterwards he applied the favorable hydrocarbon one. It could be handled much easier and the specific volumetric energy content was increased by about four-fold higher. These aspects then have been appreciated by the aircraft manufacturers and operators. 

The volumetric energy content, mostly understood as the energy density (ED), goes from 300 to 1300 Wh/L. Lithium batteries therefore require less space than conventional battery systems. Leclanche cells, for example, dehver 165 and alkaline cells 330 Wh/L. 

TABLE 12.7 Density and Volumetric Energy Content of Various Solid and Liquid Fuels... 

The useful energy content of a battery is designated in watt hours and is the product of ampere hour capacity and the average discharge voltage. To enable comparisons to be made between one battery and another this is often expressed as Wh/dm on a volumetric basis or Wh/kg on a weight basis. 

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