- asynchronous generators for insular networks, i.e. an electronic control system on the
generator stabilizes a constant power network.
Converting one type of generator to the other is very intricate and involves a complicated electronic
In selecting a particular type of motor generator, one must give due consideration to the various
operating conditions and network requirements (including the legal aspects of power feed-in).
Checklist for choosing a suitable engine
1. Define the energy requirement and speed of the machine to be powered;
2. Compare the biogas demand with the given storage capacity; if a shortage is possible, opt for
the dual-fuel approach;
3. Select an engine with performance characteristics that are sure to provide the required power
output in sustained operation in the optimal duty range:
- diesel engines Pengine = Pmachine/0.8
- gasoline engines Pengine = Pmachine/0.G
This accounts for the fact that the continuous-duty power output is less than the nominal output. On
the other hand, choosing an overly powerful engine would make the specific consumption
unnecessarily high. Careful planning is very important in any project involving the use of biogas in
engines; experienced technicians are needed to make the engine connections; and access to
maintenance and repair services is advisable. Both the biogas plant itself and the engine require
protection in the form of a low-pressure cutout that shuts down the latter if the gasholder is empty.
Chapter 10.5 lists some recommended types of biogas engines and supplier addresses.
5.6 Measuring methods and devices for biogas plants
The purpose of conducting measurements on a biogas plant is to enable timely detection of
developing problems, adjustment to optimum operating conditions, and gathering of practical 'data
for comparison with those of other plants. The following variables can be measured quickly and
- gas production via dry gas meter or by measuring the fill level of the gasholder
- weight of inputs via a hand-held spring scale
- temperature via an ordinary stem thermometer or electronic temperature sensor
- total-solids content by drying a sample at 104 °C and weighing the residue on a precision
- H2S content of the gases via a gas test tube
- pH via litmus paper.
The contents of the substrate/slurry can only be determined by a special laboratory.
Various levels of precision are recommended, depending on the set objective and corresponding
time, effort and equipment expenditure.
Observation by the user