Optimizing Operation of Stationary Fuel Cell Systems (FCS) Within District Cooling and Heating Networks

We evaluate innovative design, installation, and control strategies for generating combined cooling, heating, and electric power (CCHP) with fuel cell systems (FCS). The addition of an absorptive cooling cycle allows unrecovered FCS heat to be converted into cooling power, such as for air-conditioning. For example, unrecovered low temperature (80–160°C) heat can be used to drive absorption chillers to create a chilled water stream to cool building spaces. Compared with separate devices that individually generate electricity, heat, and cooling power, such CCHP FCS can reduce feedstock fuel consumption and the resulting greenhouse gas emissions (GHG) by at least 30%. We develop economic and environmental models that optimize the installed capacity of CCHP FCS to minimize either global carbon dioxide (CO₂) emissions or global energy costs. Our models evaluate innovative engineering design, installation, and control strategies not commonly pursued by industry, and identify strategies most beneficial for reducing CO₂ emissions or costs. Our models minimize costs for building owners consuming cooling power, electricity, and heat by changing the installed capacity of the FCS and by changing FCS operating strategies. Our models optimize for a particular location, climatic region, building load curve set, FCS type, and competitive environment. Our models evaluate the benefits and drawbacks of pursuing more innovative FCS operating strategies; these include 1) connecting FCS to distribution networks for cooling power, heat, and electricity; 2) implementing a variable heat-to-power ratio, to intentionally produce additional heat to meet higher heat demands; 3) designing in the ability to tune the quantity of cooling power from the absorption chiller compared with the amount of recoverable heat from the FCS; and 4) employing the ability to load-follow demand for cooling, heat, or electricity. We base our datum design conditions on measured data describing generator performance in-use, and on measured data describing real-time electricity, heating, and cooling demand over time. A unique feature of our data sets is that the space cooling demand is directly measured and distinguishable from electricity demand (unlike as with standard air conditioning systems). We report results for optimal installed capacities and optimal FCS operating strategies. We generalize these results so that they are applicable to a wide-range of environments throughout the world.