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The road to pure plant oil in diesel engines?

Alternative applications

An application that has recently appeared, primarily in a few places in Germany, concerns fuel in decentralised cogeneration plants. These are engine-driven cogeneration plants that are used as heating installations for a building. Applications can be found in a hospital, a parson’s house, an alpine hut and in various apartment buildings26 . Suppliers include the following companies:

• KWS Energie und Umwelt GmbH;
• B + V Industrietechnik;
• Waertsilae NSD Deutschland GmbH;
• Antriebs- und Maschinentechnik;
• Anlagen- und Antriebstechnik Nordhausen GmbH.

All these suppliers deliver engines designed to run on rapeseed oil. Standard diesel engines can also be converted.
The electrical capacity generated by these ‘dedicated’ engines ranges from a few kWe up to over 8 mWe. The electrical efficiency varies from 25% for the smallest engines, to 42-43% for the largest. The thermal efficiency varies from 55% for the smallest engines, to 40% for the largest.

In theory, all engines can be fitted with a complete flue gas cleaning system, consisting of a soot filter, SCR and oxycatalyst, thereby (in theory) always meeting the BEES criteria for suction engines. As a comparison of the feasible residual concentrations and BEES, the following figures are listed here

• Emissions from engines with a soot filter amount to 2 – 5 mg/Nm3 (5 vol% O2);
• Emissions from engines with an oxycatalyst amount to 2 – 15 mg/Nm3 (5 vol% O2);
• For NOx, engines with an SCR give guarantee values of 250 mg/Nm3 (5 vol% O2).

The cost price is less than € 1,000/kWe for the largest machines (including SCR), up to€ 1,000 - € 1,500 per kWe for machines producing several hundred kWe.
Details of the economic return can be found on the website:
http://www.bhkw-infozentrum.de/req/poe_wirtschaftlichkeit.html. In summary, it is clear that using PPO in stationary cogeneration engines in Germany is economically viable.
Corporate experience of stationary engines running on rapeseed oil are comparable to experience of engines in mobile applications. Problems exist due to insufficiently pure fuel, deposits of phosphor compounds and reduced quality of the lubrication oil.

Additional information

This section summarises the analysis of the PPO chain as described in the individual chapters, and primarily gives an overview of the environmental impact. The results are compared with those of other studies, particularly studies into biodiesel.

Using PPO in vehicles
The available and developed technologies for using PPO in vehicles are, up to now, limited to a restricted set of conversion packs for a limited number of vehicle types. The technique is still being developed. This means that the possibilities for using PPO in vehicles is still limited at this point in time.
The standardisation criteria for PPO production are also still being developed. Production currently only takes place on a small scale. Standards for storage, production, cleaning and analysis of the oil are currently lacking. [Hassel, 2004] provides recommendations for developing these types of standards. Recommendations are also made for handling largescale distribution and mixing batches of PPO at central locations, thus achieving and guaranteeing a more constant fuel quality.
The production technologies used thus far (cold pressing with refining), seem to produce a fuel that is often of insufficient quality. It would be better to refine the fuel.
There is also still no standard available for the fuel, to which the car and engine manufacturers agree. It will probably be some years yet before such a standard is defined (if ever), considering the lack of interest by manufacturers.
In other words, using PPO as a vehicle fuel is indeed technically possible, but PPO is not yet ready for large-scale sale to end-users, due to the lack of suitable structure and standardisation.

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