integration of solid oxide fuel cells and ... - Ea Energianalyse

2.2 Auxiliary Power Unit (APU)
2.2.1 Truck APU
2.2. Auxiliary Power Unit (APU)
Large trucks normally idle their main engine when they are parked in
order to generate air conditioning for cooling the cabin and electricity
for equipment such as microwave ovens, TV, DVD player etc. Idling
the engine for this is, however, quite inefficient, since a diesel engine
efficiency is quite small at low loads. One solution for this problem could
be to mount a SOFC on the truck to generate electricity when parked, and
then use the waste heat to drive an absorption air condition. But there
are two problems:
1. The air conditioning need is in the order of 3kW reference [22], and
the electricity need (excluding electric air condition) seems to be
no higher than 2kW. So if a SOFC should generate the electricity, it
would probably suffice with a unit of 2kWe combined with some
batteries to take care of peak load. And the approximately 2kW
of waste heat would not be nearly enough to generate sufficient
cooling, since the COP of the smallest (4kW cooling) absorption
unit is only 0,4.
2. Even the smallest (4kW cooling) heat driven AC sorption units
weighs 216kg excl HEXes, and takes up a lot of space. This is
disadvantageous on a truck since it is desired to have as much space
as possible cleared for the cargo. Furthermore the extra weight
slightly reduces the maximum cargo load.
Hence the SOFC/ABS AC is not a good match for a truck.
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