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Research Papers

Independent Analysis of Real-Time, Measured Performance Data From Microcogenerative Fuel Cell Systems Installed in Buildings

[+] Author and Article Information
Heather E. Dillon

Pacific Northwest National Laboratory,
Richland, WA 99352

Whitney G. Colella

Pacific Northwest National Laboratory,
Richland, WA 99352
e-mail: wcolella@alumni.princeton.edu

1Corresponding author.

Contributed by the Advanced Energy Systems Division of ASME for publication in the Journal of Fuel Cell Science and Technology. Manuscript received April 27, 2012; final manuscript received May 24, 2012; published online March 16, 2015. Assoc. Editor: Nigel M. Sammes.

J. Fuel Cell Sci. Technol 12(3), 031007 (Jun 01, 2015) (8 pages) Paper No: FC-12-1031; doi: 10.1115/1.4007162 History: Received April 27, 2012; Revised May 24, 2012; Online March 16, 2015

Pacific Northwest National Laboratory (PNNL) is working with industry to independently monitor up to 15 distinct 5 kW-electric (kWe) combined heat and power (CHP) high temperature (HT) proton exchange membrane (PEM) fuel cell systems (FCSs) installed in light commercial buildings. This research paper discusses an evaluation of the first six months of measured performance data acquired at a 1 s sampling rate from real-time monitoring equipment attached to the FCSs at building sites. Engineering performance parameters are independently evaluated. Based on an analysis of the first few months of measured operating data, FCS performance is consistent with manufacturer-stated performance. Initial data indicate that the FCSs have relatively stable performance and a long-term average production of about 4.57 kWe of power. This value is consistent with, but slightly below, the manufacturer's stated rated electric power output of 5 kWe. The measured system net electric efficiency has averaged 33.7%, based on the higher heating value (HHV) of natural gas fuel. This value, also, is consistent with, but slightly below, the manufacturer's stated rated electric efficiency of 36%. The FCSs provide low-grade hot water to the building at a measured average temperature of about 48.4 °C, lower than the manufacturer's stated maximum hot water delivery temperature of 65 °C. The uptime of the systems is also evaluated. System availability can be defined as the quotient of total operating time compared to time since commissioning. The average values for system availability vary between 96.1 and 97.3%, depending on the FCS evaluated in the field. Performance at rated value for electrical efficiency (PRVeff) can be defined as the quotient of the system time operating at or above the rated electric efficiency and the time since commissioning. The PRVeff varies between 5.6% and 31.6%, depending on the FCS field unit evaluated. Performance at rated value for electrical power (PRVp) can be defined as the quotient of the system time operating at or above the rated electric power and the time since commissioning. PRVp varies between 6.5% and 16.2%. Performance at rated value for electrical efficiency and power (PRVt) can be defined as the quotient of the system time operating at or above both the rated electric efficiency and the electric power output compared to the time since commissioning. PRVt varies between 0.2% and 1.4%. Optimization to determine the manufacturer rating required to achieve PRVt greater than 80% has been performed based on the collected data. For example, for FCS Unit 130 to achieve a PRVt of 95%, it would have to be down-rated to an electrical power output of 3.2 kWe and an electrical efficiency of 29%. The use of PRV as an assessment metric for FCSs has been developed and reported for the first time in this paper. For FCS Unit 130, a maximum decline in electric power output of approximately 18% was observed over a 500 h period in Jan. 2012.

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Figures

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Fig. 1

Two FCSs tested for this study in Portland, OR

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Fig. 2

Net electric power output for FCS Unit 130. The manufacturer-rated power (5 kWe) is shown as a dashed line, and the mean value over the operating time (4.87 kWe) is shown as a solid black horizontal line.

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Fig. 3

Net electric power output for FCS Unit 130 startup event

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Fig. 4

Net electric power output for FCS Unit 130 downtime event. In this case, the system was returned to partial load prior to resuming operation at the full-power setpoint.

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Fig. 5

Electric power efficiency for FCS Unit 130. The manufacturer-reported efficiency of 36% is shown as the dashed line. The black horizontal line represents the system average of 32.8%.

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Fig. 6

Electric power efficiency for FCS Unit 129. The manufacturer reported efficiency of 36% is shown as the dashed line. The black horizontal line represents the system average of 32.7%.

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Fig. 7

Temperature of the cooling water sent to the site for FCS 130. The manufacturer-reported maximum temperature of 65 °C is shown as the dashed line. The black solid line represents the system average of 47 °C.

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Fig. 8

Decline in power output. A decline in electric power output of approximately 20% over 1500 h was observed.

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