Development of an open access tool for design, simulated dispatch, and economic assessment of distributed generation technologies

Abstract

a b s t r a c tThe design and deployment of DG systems requires an integrated assessment of the building and generator dynamics including the time-variant energy costs and emission factors. Static design optimizations are unable to consider the physical generator operating constraints, seasonal variability and non-coincidence in electric, heating, and cooling demands. This paper introduces the Distributed Generation Build-out Economic Assessment Tool (DG-BEAT) which combines building, utilities, and emissions databases with a library of simplified generator and building models in a user-friendly interface. Five control strategies are presented for the dynamic dispatch of distributed generation technologies at commercial buildings. The control approaches stem from the physical limitations of different generator types. Methods are also outlined for the dispatch of complementary technologies (e.g. energy storage) and accommodation of onsite renewables (e.g. solar PV) which could further improve the economic or environmental benefits of distributed generation. This paper details the methodology of sizing and dispatching distributed generation components, outlines eight databases that are employed to capture regional variations in pricing and building dynamics, and discusses the myriad of customizations available to provide a tailored analysis for a single building or national impact studies.

Stall/surge dynamics of a multi-stage air compressor in response to a load transient of a hybrid solid oxide fuel cell-gas turbine system

“…The overall mechanism of stall/surge in a compressor due to the increase in turbine inlet temperature (TIT) has been previously studied by McLarty et al [35]. Other researchers have addressed stall/surge in hybrid SOFC-GT systems and developed control methods to address stall/surge issues in the compressor.…”

“…The model consists of a compressor, a turbine, a blower, an SOFC, a combustor, three mixers and several bypass valves (one for fuel cell bypass and the others for heater bypass). This model has been previously studied for different applications of SOFC-GT hybrid systems (see, for example [26,27,35,37]). Fig.…”

“…These equations have been previously used by McLarty et al [35]. Input parameters of the compressor were the ambient temperature, the species concentrations, the shaft speed and the inlet/exit pressures.…”

“…The large volume between the compressor and the turbine causes mass accumulation and produces pressure dynamics during dynamic operation of the hybrid system. The approach is patterned after that which was previously developed at NFCRC [26,27,35,37]. Various control algorithms are applied to the dynamic system model to prevent deep surge in the compressor.…”

“…The diffuser between the two impeller stages resembles the plenum volume for the front impeller. The plenum volume for the rear impeller is replaced by the simulated pressure variation over time from the system dynamic model that includes dynamic simulation of the large volume of the fuel cell between the simplified (compressor map and turbine map) dynamic model of the turbomachinery (see [35]). …”