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Engineering information and sizing
3.3.2
Sizing of CHP module
A Bosch CHP module for waste heat use generally
consists of a gas engine, a three-phase generator and a
heat exchanger system.
The engine drives the generator for power generation.
Depending on the operating conditions, synchronous
generators are used for power generation. They
generate three-phase current with a frequency of 50 Hz
and a voltage of 400 V.
The three-phase current generated by the generator is
fed into the main low-voltage distribution board on-site
(LVDB = 0.4 kV level). The power is used according to
the current demand in the connected building, excess
power can be fed into the network of the electricity
operator.
Waste heat is generated during this energy conversion,
as it is in all combustion engines.
The heat from the lubricating oil and the engine coolant
is transferred via a heat exchanger system to a closed
DHW/heating system.
3.3.3
Steam amount/waste heat output and CHP/boiler combinations
As already described in chapter 3.3.1, page 23, this
results in general in a technically sensible factor of the
waste heat utilisation in the steam boiler of < 20 %.
A possible allocation of CHP/steam boiler is given in
table 14, üage 27 and table 15, page 28.
The steam amount that can be created from HT waste
heat in a 4-draught steam boiler with the selected
combination CHP/steam boiler is given in % and kg/h.
Reference value is the given total steam output of the
boiler.
24
The heated water can be used for:
• Building heating
• DHW heating
• LT process heat
• Make-up water treatment in steam process
The reduction of the low temperature must be ensured
for operation of the CHP module and is thus a restriction
for sizing the combination.
The hot motor flue gases are used in the fourth draught
of the downstream 4-draught steam boiler for creating
steam. The energy utilisation of the CHP module is,
including waste heat utilisation in the steam boiler, up to
approx. 94 %.
The energy is provided as high-quality electrical energy,
LT and HT energy for steam generation.
For a planned waste heat utilisation, the sizing of the
CHP module should be oriented towards the maximum
output of the fourth draught of the steam boiler.
For covering the LT heat required in the
system, an additional peak load boiler can
be necessary.
The hot flue gases produced by the CHP are directly
used for steam generation in the fourth draught of the
steam boiler. A decoupling in time by temporary storage
of the flue gases is not possible for technical reasons.
The runtime of a CHP therefore mainly depends on the
useful life of the boiler system. For correct
determination of the runtime of the CHP module during
planning, is makes sense to create a sorted annual load
duration curve for steam demand, in analogy to the LT
heat energy demand.
If the CHP shall be operated for a longer time or not in
parallel with the boiler, a bypass must be available in the
flue gas line for bypassing the boiler system
(
page 20).
Systemlösung – 6 720 885 509 (2018/03)
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