Stand-alone Power Systems For The Future

Stand-Alone Power Systems for the Future: Optimal Design, Operation & Control of Solar-Hydrogen Energy Systems Ø. Ulleberg ABSTRACT A stand alone power system (SAPS) is defined as a decentralized electricity producing system. The first part of the thesis, which begins with an introduction on the global needs and requirements of SAPS, is slightly philosophical. The initial focus is on several fundamentally important energy issues related to SAPS. A systematic approach demonstrates in a factual way why solar–hydrogen systems are one of the most viable options for the future. In this context, the most realistic technological options are reviewed and a few general recommendations about generically optimal SAPS for the future is given. The second part, and main bulk, of the thesis deals with the modeling of SAPS, with focus on PV–H2 systems. Simulation models for TRNSYS have been developed for PV–H2 components, including models for a PV-generator, a water electrolyzer, a fuel cell, and a secondary battery. These models are based on both physical and chemical principles, as well as empirical parameters. The PV–H2 demonstration plant PHOEBUS, located at the research center in Jülich, Germany, was studied in detail and served as a reference case. This plant has been in operation since 1993, but most of the comparisons between simulated and measured data were made for 1996—a year with very consistent operation and regular minutely measurements. The developed TRNSYS models were also tested and verified up against data from separate experiments of PV–H2 system components. One example of this is the model for a PEM fuel cell. The third part of the thesis includes detailed simulation studies of integrated SAPS, with focus on systems based on solar–hydrogen energy technology similar to that used in the PHOEBUS plant. The simulations gave answers to several important issues related to the design and operation of PV–H2 systems. The influence of various control strategies on the overall system performance was investigated. These overall control strategies are interrelated to the design of the overall system in a way which is best understood by running one-year simulations. Since, the final design of SAPS based on hydrogen depends heavily on the size and profile of the users’ power demand and the location of the system, a general conclusions about the optimal design of such systems is not easily found. However, one feasible approach—and the one applied in this thesis—is to find the optimal control actions for various system configurations for a given load and location. These systems may include alternative components such as wind energy conversion units. The TRNSYS models developed for this study are general, flexible, and include parameters that readily can be obtained by following the procedures outlined in this thesis. Thus, the developed simulation tools can be used to simulate hydrogen–SAPS with different loads and locations.

Ulleberg Ø. (1998) Stand-Alone Power Systems for the Future: Optimal Design, Operation & Control of SolarHydrogen Energy Systems. PhD thesis, Norwegian University of Science and Technology, Trondheim.