III. GESTIOADO CO LA ALEATORIEDAD
1. La aleatoriedad, un enigma del orden en la práctica gerencial
The operation of a DC interconnected stand-alone power system has been proven by this research. The general design presented in this thesis has some advantages over other stand-alone systems, but a number of issues still require further research. The use of standard motor drives and DC busbar is a good solution for the rotating generators and loads. Accurate voltage and frequency control can be used to perform soft-starts and to operate at variable speed to reduce mechanical strain, which may reduce the maintenance requirements of the wind turbines.
The power converters required for the connection of rotating AC devices are standard and hence readily available and cost effective. They also have sophisticated in-built control and are generally quite adaptable.
The main conclusion of this project is that, although such a system is feasible, it is a complicated solution and the long-term reliability of such a system must be proven. The complexity stems mainly from the number of different devices from various
manufacturers. More research needs to be carried out before such a system could be reliably used within a remote community.
‘Off the shelf’ components have been used whenever possible, but many different components were required, including a number of bespoke units. The system was designed so that components can be easily and safely disconnected for
maintenance and adjustment. This led to the requirement for additional DC-rated switchgear, which added to the cost and complexity. The final cost of this project does not make it economically viable in the majority of situations, although it is hoped that, through standardisation and mass manufacture, the costs could be greatly reduced.
Electrolyser technology must be improved to better integrate with variable energy source, specifically concerning its response to variable input power and limited power range. This may reduce or remove the need for battery storage on the system.
Fuel cells designed specifically for connection to such a system would also be required. This could lead to a more electrically efficient storage system.
This work describes an interesting renewable energy system upon which more research can be based. Although feasible, the DC interconnection system requires more research and input from a number of industries before it could be implemented reliably and economically in a remote location.
13 Acknowledgements
This research has relied upon numerous people for a successful outcome. The author would like to thank the following:
Professor Tony Marmont: for supplying the encouragement and the financial means to carry out this research, and allowing his home to be used as a test-bed.
Professor David Infield: for his supervision and guidance.
Murray Thomson: for the initial idea for this project, along with endless help and guidance along the way.
Mick Plowright: for his excellent workmanship and expertise, for imparting so much knowledge and for always having the kettle ready when things were not running to plan.
The whole of the HaRI team: Rupert Gammon, whose vision helped push this project forward, Amitava Roy, who always kept a positive outlook, and John Barton, who was always there to talk through a problem.
Professor Jon Claire, Dr Mark Sumner and others at the Power Electronics,
Machines and Control Group at Nottingham University: for freely giving up their time and expertise to help with power electronic design.
Martin Green, Frank Pitt and all involved with this project at Control Techniques. Roger Bull and Mark Milward at Beta Research and Development.
Wendy, Brian, Des and Ben at Beacon Energy: for their help and good humour. Angela Marmont: for her tolerance of the disruption caused to her home by this research.
14 Glossary of terms and abbreviations
BOS Balance of system
CHP Combined heat and power
DC-DC Direct current to direct current
HaRI Hydrogen and renewable integration
Nm3 Normal meter cubed
OPC Object linking and embedding for process control PV Photovoltaic
PWM Pulse width modulation
RE Renewable energy
SAPS Stand-alone power system
15 Publications by the author
M. Little, M. Thomson and D. Infield “Electrical integration of renewable energy into stand-alone power supplies incorporating hydrogen storage” presented at the
Second European Hydrogen Energy Conference, Zaragoza, 2005. (To be published in a special EHEC edition of the International Journal of Hydrogen Energy).
M. Little, M. Thomson, and D. G. Infield, "Control of a DC-Interconnected
Renewable-Energy-Based Stand-Alone Power Supply," presented at Universities Power Engineering Conference, Cork, 2005.
M.Little, D.Infield, M.Thomson, “Electrical Integration of Renewable Energy into Stand-Alone Power Supplies with a Central DC Bus”, Loughborough University Division Conference, Sutton Bonnington, Nottinghamshire, 2005.
M. Little, M. Thomson, and D. G. Infield, "Power converters for use in stand-alone renewable energy systems incorporating hydrogen storage," presented at
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