Efficiency improvement of a fuel cell cogeneration plant linked with district heating: Construction of a water condensation latent heat recovery system and analysis of real operational data

Author(s):  
Li Yuan-Hu ◽  
Jinyoung Kim ◽  
Sangrae Lee ◽  
Gunhwi Kim ◽  
Haksoo Han
Author(s):  
Robert G. Ryan ◽  
Tom Brown

A 1 MW Direct Fuel Cell® (DFC) power plant began operation at California State University, Northridge (CSUN) in January, 2007. This plant is currently the largest fuel cell plant in the world operating on a university campus. The plant consists of four 250 kW DFC300MA™ fuel cell units purchased from FuelCell Energy, Inc., and a waste heat recovery system which produces dual heating hot water loops for campus building ventilation heating, and domestic water and swimming pool heating water for the University Student Union (USU). The waste heat recovery system was designed by CSUN’s Physical Plant Management and engineering student staff personnel to accommodate the operating conditions required by the four individual fuel cell units as well as the thermal energy needs of the campus. A Barometric Thermal Trap (BaTT) was designed to mix the four fuel cell exhaust streams prior to flowing through a two stage heat exchanger unit. The BaTT is required to maintain an appropriate exhaust back pressure at the individual fuel cell units under a variety of operating conditions and without reliance on mechanical systems for control. The two stage heat exchanger uses separate coils for recovering sensible and latent heat in the exhaust stream. The sensible heat is used for heating water for the campus’ hot water system. The latent heat represents a significant amount of energy because of the high steam content in the fuel cell exhaust, although it is available at a lower temperature. CSUN’s design is able to make effective use of the latent heat because of the need for swimming pool heating and hot water for showers in an adjacent recreational facility at the USU. Design calculations indicate that a Combined Heat and Power efficiency of 74% is possible. This paper discusses the integration of the fuel cell plant into the campus’ energy systems, and presents preliminary operational data for the performance of the heat recovery system.


Author(s):  
Robert Ryan

A 1 MW fuel cell power plant began operation at California State University, Northridge (CSUN) in January, 2007. The power plant was installed on campus to complement a Satellite Chiller Plant which is being constructed in response to increased cooling demands related to campus growth. The power plant consists of four 250 kW fuel cell units, and a waste heat recovery system which produces hot water for the campus. The waste heat recovery system was designed by CSUN’s Physical Plant Management personnel, in consultation with engineering faculty and students, to accommodate the operating conditions required by the fuel cell units as well as the thermal needs of the campus. A unique plenum system, known as a Barometric Thermal Trap, was created to mix the four fuel cell exhaust streams prior to flowing through a two stage heat exchanger unit. The two stage heat exchanger uses separate coils for recovering sensible and latent heat in the exhaust stream. The sensible heat is being used to partially supply the campus’ building hot water and space heating requirements. The latent heat is intended for use by an adjacent recreational facility at the University Student Union. This paper discusses plant performance data which was collected and analyzed over a several month period during 2008. Electrical efficiencies and Combined Heat and Power (CHP) efficiencies are presented. The data shows that CHP efficiencies have been consistently over 60%, with the potential to exceed 70% when planned improvements to the plant are completed.


1999 ◽  
Author(s):  
Erika Söderlund ◽  
Andrew R. Martin ◽  
Per Alvfors ◽  
Jonas Forsman ◽  
Laszlo Sarközi

Abstract This study presents some of the experiences gained during a two year operational period of a decentralized fuel cell cogeneration plant installed in southern Sweden. Various modifications to the system are described, most notably a plume eliminator for the reduction of an undesirable vapor cloud emitted by the original system. Aside from vapor cloud elimination, the plume eliminator allows for more efficient plant operation, as a larger fraction of the system cooling requirements can be shifted to the district heating system. In-field measurements show a 17 to 26% increase in district heat production with use of the plume eliminator, depending upon the season of operation (winter or summer). The study also presents two options for added heat recovery, which are employed in conjunction with the plume eliminator: an air preheater module; and an air preheater/humidifier module. Calculations show that air preheating has a small but measurable impact on heat recovery (an additional 8% gain), while combined air preheating and humidification allows for nearly a 50% increase in district heat production.


2018 ◽  
Vol 22 (6 Part A) ◽  
pp. 2667-2677 ◽  
Author(s):  
Vytautas Dagilis ◽  
Liutauras Vaitkus ◽  
Algimantas Balcius ◽  
Juozas Gudzinskas ◽  
Valdas Lukosevicius

The paper analyses low grade heat recovery problem for modern woodfuel cogeneration plant. The woodfuel flue gas, behind the condensing economizer, still contains a considerable amount of heat, main part of which is the latent one. To recover this low grade heat, the heat pump technology can be used, which is related with additional consumption of energy (electric, mechanical or heat). Another technique that could be applied is a heat regeneration when flue gas heat, mostly latent, is transmitted to air blown towards burning chamber. Therefore, the analysed heat recovery system operates mainly like mass regenerator which contains only blowers that use some electric energy. The regenerator consists of two cyclically operating columns with packing material. Energetic analysis demonstrates that 13% of additional heat can be produced utilizing this low grade heat. The economic valuation shows that investment in a heat recovery system is quite effective; the payback time is about four years.


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