From many years experience researching the applications of alternative fuels, it is clear that the alternative fuels depend on the design requirements of the prime mover matching the characteristic properties of the fuel used and the characteristic properties of possible alternative fuels. When the designed fuel requirement of the prime mover is matched with the characteristic properties of an alternative fuel, the prime mover will operate as designed. But when the properties of an alternative fuel do not match, the prime mover will operate outside (off design) its designed operating conditions and naturally the output (performance: power, fuel consumption, efficiency, etc., emission: exhaust gas emission, noise, etc., life time) will also be affected.

There are two ways to solve this problem. Firstly the prime mover design requirement for fuel characteristics may be converted (adapted) to match the characteristic properties of the alternative fuel. Alternatively the characteristic properties of the alternative fuel may be converted (adapted) to match the designed fuel requirements of the prime mover. This concept is illustrated in Fig. 23.25. The most important requirement for the interface is that the standard must be met to satisfy requirements of both sides. Which choice to use and how far to convert each will depend on many factors, including location, technical, and economic, social and political aspects. For example in the case of biofuel for a high technology engine which has a design requirement for a high quality fuel, fuel conversion (adaptation) to a vegetable based oil may require transesterification to produce FAME to fulfil the high quality standard of fuel needed. But, for a stationary diesel engine where the operating condition is relatively constant, the required level of fuel quality may be relatively low, so a PPO with a lower production cost may be suitable. However, adapting the engine to use the PPO fuel may require the addition of a fuel heating system, a second fuel tank and a switching system to enable starting of the engine on diesel to warm up the engine and heat the PPO

23.25

The concept of using alternative fuel (AE) on prime mover (PM).

fuel and switch back to diesel before stopping the engine to flush the fuel system with diesel.

Clearly, when an engine designed for a certain fuel is converted to run on an alternative fuel, it is very important to see that the design need of the engine for the characteristic properties of the fuel is matched by the characteristic properties of the alternative fuel. Consequently it is very important to establish effective standards for alternative fuels.

23.3 Conclusions

As the majority of ASEAN countries are located in humid tropical regions, many different plant oils and animal fats are available as sources of biofuel feedstock. Consequently the properties and quality of differing biofuels vary considerably. The use of alternative fuels depends on matching the characteristic properties of the fuel for which the engine was originally designed with the characteristic properties of possible alternative fuels. When the design fuel requirement of the engine closely matches the characteristic properties of the alternative fuel, the engine will operate as designed, whereas if the properties of the alternative fuel do not match, the engine will operate outside (off design) the design operating conditions and performance will be affected.

To solve this problem the engine design requirement for fuel characteristics may be altered or adapted to match the characteristic properties of the alternative fuel or the characteristic properties of the alternative fuel may be adjusted or adapted to match the design fuel requirements of the engine. The requirements of both sides must be satisfied. What choices are made and how far adjustments are made in either respect, depends on many factors, including location, technical, and economic, social and political aspects.