Efficiency auxiliary power unit

A conceptual design and selection of an ATR biodiesel processor for a vehicle fuel cell auxiliary power unit were reported by Specchia et al. [81]. Three processor options were compared for H2 production with respect to efficiency, complexity, compactness, safety, controllability and emissions. The ATR with both high-temperature shift (HTS) and low-temperature shift (LTS) reactors showed the most promising results. 

A compact design for a gasoline fuel processor for auxiliary power unit (APU) applications, including an autothermal reformer followed by WGS and selective oxidation stages, was reported by Severin et al. [83]. The overall fuel processor efficiency was about 77% with a start-up time of 30 min. 

At 1-10 W (watts), fuel cells could be used as battery replacements at 100 W to 1 kW, fuel cells could find military applications which require lightweight portable power sources for communications and weapon power at 1 - 10 kW, fuel cells could supply power to residential buildings and serve as auxiliary power units in vehicles and trucks. At higher power levels, the solid oxide fuel cell (SOFC) could be an effective approach for the distributed power generation and the cogeneration (i.e., combined heat and power). Above 1 MW, the SOFC could be integrated with a turbine power plant to improve the overall efficiency of power generation and reduce emissions. ... 

Supercapacitors [75,76] and fuel cells [77,78] have also been proposed for road vehicles, but are not expected to be widely used in the present decade. As an auxiliary power unit (APU), a fuel cell could replace the alternator for the generation of electrical energy. The motivation for this change would be higher overall efficiency. 

Identified diesel-based 5-kWe fuel cell auxiliary power unit (APU) system with >50% electrical conversion efficiency... 

SOFC can be operated as auxiliary power unit to utilize the heat generated, and further increase the overall efficiency. 

Table 5.14 Comparison of product mass flow rates, reformer efficiency T f., fuel processor efficiency T fp and auxiliary power unit efficiency T)apu of autothermal reforming dry hydrogen molar fraction of the reformate yjj values are determined for various fuels, feed inlet...

Table 5.15 Comparison of product mass flow rates, reformer efficiency T r, fuel processor efRciency T fp and auxiliary power unit efRciency T apu of steam reforming values are determined for various, feed inlet temperatures Tjn and S/C (SCR) and O/C ratios (expressed as O2/C ratio OCR) as calculated by Specchia etal. [371]. is the fraction of the fuel which is fed to the steam reformer 1- Pr is fed to the burner yp is the dry hydrogen molar fraction of the reformate Wq shows the water balance of the systems, which is positive when the Wq exceeds unity. 

SOFC technology, on the other hand, offers interesting options to improve the effectiveness of CHP units. The reasons are many the prospects for high efficiency, low emissions, low noise, scalability, reliabihty, and, finally, potentially low cost. However, the main attractiveness in CHP is the high system efficiency even for small units and at part load operation [14]. Among the most interesting applications are stationary distributed power generation (incl. CHP), small residential combined heat and power units (micro CHP), various transport apphcations (auxiliary power units, APU), and medium-sized portable systems up to 5 kWei-... 

Thus, SOFC/turbine hybrid systems are better than conventional combustion systems in terms of electrical efficiency, part-load efficiency, and emissions. Reliability and maintenance cost of mature SOFC systems will probably be comparable with gas turbine systems and certainly better than gas engines. Attributes of SOFC systems in the field of control speed, control range, investment cost and lifetime have yet to be fully established. The longer start-up time of SOFC systems is a clear disadvantage for certain market applications, for instance, the uninterruptible power supply market and the auxiliary power units for the transportation market. 

The strategies can be used to reduce emissions for both a specific facility (e.g., minimizing the use of auxiliary power units) and for a specific project (e.g., installing energy efficient equipment as part of a building renovation). 

Capstone Microturbine (Reference 9- 7) - Open cycle turbine, compressor, alternator (30-200 kWe) with gas foil bearings for high efficiency distributed power generation. Auxiliary Power Units (APU) (Reference 9- 2) - Open cycle turbine, compressor, alternator (up to 40kWe)... 

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