University of Leicester to create clean electricity from the sun

The photograph above shows the photo-voltaic (PV) array, recently installed on the roof of the former Concrete Laboratory, which is part of the Engineering Building complex on the Main Campus. This PV array is a demonstration and research system, installed as part of the UNIVERSOL project, part-funded by the EC and aimed at providing 26 PV demonstration systems on educational and cultural establishments in 4 EU countries (Spain, France, UK and the Netherlands) to disseminate knowledge on PV technology. The system, designed by Dr Hans Bleijs and Dr Anton Simmons of the Department of Engineering and installed by PV Facades (now Solar Technologies), provides a flexible research facility for the Electrical & Electronic Power Engineering Group for the development of novel power converters and controllers and the study of optimum array topologies under partial shading conditions. It is the first system in the U.K to feature the latest BP Solar Saturn Series 7 technology, which is one of the most efficient technologies for commercial mono-crystalline single-junction PV modules. The system was commissioned at the end of November 2004, and includes an extensive monitoring system to collect and record electrical and ambient data on the performance of the overall system and its sub-arrays. Educational displays with real-time and historic data are provided in the Concrete Laboratory and an interactive display is planned for the Foyer of the Engineering Tower.

Technical details of the system can be downloaded here.

PV technology will also be incorporated in the facade and atrium of the new Library Extension to produce clean, non-polluting electricity for lighting and environmental control in the Library:
http://www.le.ac.uk/li/newsinfo/building/jan04.html

Early experience with electricity generation from solar power was gained with a small PV battery system, installed in 2001 on a fortification off the coast of Alderney, one of the Channel Islands, to provide stand-alone power for research into propagation of radio waves in over-sea paths under adverse conditions:
http://www.le.ac.uk/engineering/emw/projects.html

Renewable Energy Conversion, Storage and Integration

Power generation from renewable energy sources has many environmental advantages, but some sources such as wind power and solar radiation pose technological challenges due to their intermittent character. Novel concepts in generators, power-electronic interfaces and system control are therefore required to meet the latest government targets for a large contribution to the electricity supply from renewable energy. The Electrical and Electronic Power Engineering group has an active research programme in this field with a main emphasis on the design, control and integration of renewable energy generators and energy storage devices.

Academic contact: Dr. J. A. M. (Hans) Bleijs

Examples of recent and current projects in this field are:

Photo-voltaic roof system for demonstration and research

The Department of Engineering has been a major participant in the UnivERsol project, part-funded by the CEC and aimed at the demonstration of PV systems integrated in buildings at universities and educational and cultural centres. Initially it was intended to integrate PV cells in the south-facing glazed roof panels in part of the famous Engineering Building on the university campus, located directly above the laboratories of the Electrical and Electronic Power Engineering Group. A detailed design of a 40 kWp system for this roof, consisting of mini-modules embedded in double-glazed units, was carried out to deal effectively with the partial shading caused by the unusual roof structure (see picture at the top of this page). Due to escalating costs for the manufacture and installation of double glazing on the entire roof this scheme had to be shelved; instead a medium-size PV system will be integrated in the planned extension of the Main Library building. Meanwhile a smaller roof-mounted PV system (11.5 kWp) has been installed on a laboratory of the Engineering complex, to provide a flexible demonstration and research facility for PV system components (panels, inverters, topology); see description at the top of this page. This system is equipped with extensive monitoring and display facilities.

Funding: CEC FP5 NNE

Power-electronic network interface for medium and large scale PV arrays

This project has investigated the optimum arrangement and control of a power-electronic interface for grid connection of medium-to-large scale PV arrays, consisting of sub-arrays with different orientations or levels of insolation. A novel topology was implemented, using modular d.c./d.c. converters with a common d.c. link to a single 3-phase network inverter. To improve reliability and performance each converter uses a current-fed architecture with galvanic isolation and contains a DSP-based maximum power point tracking algorithm with a fast and stable response. This project was followed by an industrial secondment phase for knowledge transfer.

Partners: ULDE and CEGELEC Industrial Controls

Funding: EPSRC with industrial contributions

Hybrid exciter and control system for battery charging wind turbine generators

This project aims to develop an electronic control system for battery charging wind turbines to give optimum energy capture but requiring only low-level power electronics. The controller is based on a novel control concept, aimed at minimising loop gain and improving stability, and is used in conjunction with a brushless generator with hybrid permanent magnet and wound field excitation.

Partners: ULDE and Marlec Engineering

Power converters for flywheel energy storage systems

The objective of this project was to develop fast response power converters for a reliable energy store using flywheel kinetic energy. Two concepts for the flywheel interface, i.e. a power-electronic drive with an induction motor/generator and a continuously variable transmission with synchronous motor/generator, were implemented and tested in conjunction with a wind turbine connected to a weak mains grid and an autonomous diesel generator. Stable operation in all modes was achieved for both concepts. In addition to smoothing the short-term wind power variations the converters also compensated the reactive power demand of the wind turbine's induction generator.

Project partners: ULDE, CEGELEC Industrial Controls (France/UK), Rutherford Appleton Laboratory and P.I.V. Antrieb (Germany)

Funding: CEC JOULE III programme with industrial contributions

Hydrogen generation from stand-alone wind-powered electrolysis systems

The aim of this project was to assess the impact of the variability of wind-generated electricity on the performance of (alkaline) hydrogen electrolysers and to develop a working stand-alone wind-hydrogen production system. The emphasis of the research has been on controlling the wind turbine to produce a smoothed power output, with or without the use of a flywheel or battery for short-term energy storage. Variable speed operation of the wind turbine has been shown to be effective for power smoothing on a time scale of several seconds, while the addition of a (synchronously linked) flywheel generator extended this into the minutes range.

Partners: ULDE, Rutherford Appleton Laboratory (UK), DLR (Germany) and ENEA (Italy)

Funding: CEC JOULE II programme

Research facilities in the Electrical Machines & Power Laboratory

In addition to the installed PV systems the research group has available a wide range of facilities and equipment for academic and industrial research, e.g.

Wind turbine emulator (software-driven hardware-in-the-loop system)
Small-scale solar simulator and PV array simulators
Energy storage flywheel
Motor/generator sets of various power ratings
DC and AC variable speed drives and inverters
Test cell for batteries, including a multiple battery charger/discharger unit
Torque transducers and power analysers

Other relevant facilities can be found on the Departmental web site:
http://www.le.ac.uk/eg/research/resource.html

EPSRC PhD Studentships

EPSRC funded PhD studentships are available for suitably qualified candidates to undertake research in any of the following areas:

Power converters with intelligent control for renewable energy sources and energy storage devices

To obtain maximum efficiency in the conversion of renewable energy into mains (AC) electricity it is paramount that the electrical converter closely matches the power characteristics of the renewable energy converter (REC, such as wind turbine, PV cells, etc.). Moreover, the electrical converter must operate at a high efficiency, especially at part load, to capitalise on the high investment cost for RECs. At the same time the converter must ensure that the quality of the supply is maintained, without undue interference with local consumers and/or other RECs. Also, there is an increasing demand for RECs to ride through short-term disturbances in the distribution system; future RECs may be expected to assist in local voltage regulation through active control of reactive power. In addition to the development of new power electronic circuits and topologies these demands may dictate an increased use of artificial intelligence (AI) in the control of RECs; this applies in particular to converters and controllers for energy storage.

Induction generators for variable speed wind turbines

Variable speed operation of wind turbines has a number of advantages, such as improved efficiency, reduced drive train loads and a reduction in audible noise at lower wind speeds. In additional to standard cage rotor induction generators wound-rotor doubly-fed induction generators are increasingly used in MW size wind turbines. Novel designs of induction generators that can work with power electronic converters of lower power rating or simpler design will be investigated.

Operation and control of distribution networks with embedded generators

Many of the present and future renewable energy generators will be connected to the low and medium voltage distribution networks (so-called embedded generators). This development requires a different approach to the design and operation of these networks to ensure stable and efficient operation of the embedded generators while maintaining the power quality. Increased use will be made of fast communication between generators as well as consumers, in combination with generation and load forecasting and possibly the use of local or centralised energy storage.

For further information on eligibility and application procedure visit the Graduate Office webpage.

Department of Engineering

Electrical Power and Power Electronics