In this study the waste heat from a 2.5 kW solid oxide fuel cell (SOFC) is captured and processed through a 1.5 kW absorption chiller (AC) to provide cooling for a single residence. The integration of an AC with an SOFC could create a highly dispatchable system that can meet the dynamics of measured residential power. A spatially resolved dynamic model was developed in Matlab/Simulink to simulate the dynamic operating characteristics of an SOFC system. A dynamic AC model was developed to study the dynamic characteristics and the performance of the combined co-generation system. Actual dynamic data from a single residential house was used as an input of the SOFC-AC model. For a single week, the SOFC was capable of following the highly dynamic load with an average efficiency of 56%. The AC generated 15.6 kWh of cooling with an average COP and cooling of 1.09 and 0.65 kW, respectively.

The dynamics of hydrogen energy storage (HES) integrated with large-scale renewable power (119.5 GW) using the capabilities of the existing California natural gas infrastructure were investigated. The dynamics associated with the grid demand, renewable power, pressure, and HES capacity for one week each of November and August were analyzed in detail while a higher level analysis of the entire state for the whole year was simulated in MATLAB/Simulink. It was found that the existing natural gas storage facilities may be converted to hydrogen storage facilities to store otherwise curtailed renewable energy through solid oxide electrolysis (SOE). Moreover, Solid Oxide Fuel Cell (SOFC) systems can also be used to dispatch the hydrogen back to the grid as power. The analysis in this paper shows that the dynamics of California natural gas underground storages associated with pressure and mass flow rate for achieving HES to support 100% renewable gas use are reasonable.

In this study, we experimentally evaluated electrolysis of water using a short stack of six solid oxide electrochemical cells (SOEC). A model of the SOEC stack was verified and used to evaluate thermal management of the stack operating above and below the thermoneutral voltage, which at these temperatures requires additional heat input into the stack to maintain the system operating temperature. High quality heat was supplied from a molten salt. Heat generated from concentrated solar power (CSP) can reach the required SOEC operation temperature through molten salts and can provide enough heat to sustain sub-thermoneutral voltage operation of an SOEC. The SOEC model is spatially and temporally resolved and was used to evaluate the dynamic performance of a system operating at sub-thermoneutral voltages with dynamic heat input. Dynamic results suggest high efficiency hydrogen generation can occur with external heat input under various conditions including variable power and salt flow.

A molten carbonate electrolysis cell (MCEC) is capable of separating carbon dioxide from methane reformate while simultaneously electrolyzing water. Methane reformate, for this study, primarily consists of carbon dioxide, hydrogen, methane, and a high percentage of water. Carbon dioxide is required for the operation of a MCEC since a carbonate ion is formed and travels from the reformate channel to the sweep gas channel. In this study, a spatially resolved physical model was developed to simulate an MCEC in a novel hybrid reformer electrolyzer purifier (REP) configuration for high purity hydrogen production from methane and water. REP effectively acts as an electrochemical CO2 purifier of hydrogen. In order to evaluate the performance of REP, a dynamic MCEC stack model was developed based upon previous high temperature molten carbonate fuel cell modeling studies carried out at the National Fuel Cell Research Center at the University of California, Irvine. The current model is capable of capturing both steady state performance and transient behavior of an MCEC stack using established physical models originating from first principals. The model was first verified with REP experimental data at steady state which included spatial temperature profiles. Preliminary results show good agreement with experimental data in terms of spatial distribution of temperature, current density, voltage, and power. The combined effect of steam methane reformation (SMR) and water electrolysis with electrochemical CO2 removal results in 96% dry-basis hydrogen at the cathode outlet of the MCEC. Experimental measurements reported 98% dry-basis hydrogen at the cathode outlet.

No abstract