Energy Conversion Group - Research

Introduction

Due to increased focus on, and international agreements about environmental issues, development of environmental friendly components and systems for production, storage and conversion of energy. Electromagnetic and electromechanical energy-converters will be very important in most of such new energy-systems and especially for optimal operation the primary energy-source. Some examples of such new energy-systems are systems for electrical propulsion, autonomous power systems for ships and platforms as well as solutions for integration of new renewable sources of energy to an electrical grid (wind power, Co-generation, etc.).

Usually the energy from a primary source of energy is converted to electrical energy and then connected to the electrical infrastructure already existing, or where the energy is converted to mechanical energy by help of electrical motor drives. If the actual required energy- or power in the load do not match the energy-efficient and environmental optimal point of operation of the primary energy source at each time instant, an energy storage device may be required. A typical system for energy conversion is presented in figure 1.

Typical examples of such elements are:

  • Primary Energy Source: Stirling motor, wind mills, fuel cells, gas turbines and diesel machines.
  • Energy storage devices: Batteries, high-energy capacitors, inductive storage and high-speed flywheel.
  • Electromechanical and electromagnetic energy converters: Power electronic converters, rotating electrical machines and transformers.

 

Strategy of ENO

 

The Energy Conversion Group (ENO) has worked out a strategy for their activities. For the research three fields of research have been prioritized, in cooperation with a wide network of industrial companies: Renewable sources of Energy: Develop cost-optimal power electronics and electrical machines which enable best utilization of the energy sources with respect to energy-efficiency and environmental issues; in a system either connected to existing electrical infrastructure or by conversion to mechanical energy.

 

Maritime systems and components: Propulsion of ships by help of standard diesel engines give usually a non-optimal utilization of the energy. Today an increased use of diesel electrical propulsion of ships can be seen. New power electronics and electrical machines will be developed for propulsion and thrusters. Knowledge has to be built up about how such large motor drives will influence the autonomous power systems on-board. Even development of new integrated electrical systems for replacement of hydraulic systems (top-side as well as subsea) are important areas of research.

 

Key technologies

Technologies of vital importance are: Design and control of power electronic converters

  • Design and control of electrical machines
  • Design and control of electrical machines

 

Market trends

A clear trend is increased pressure on price and the need of reduced cost and reduced losses. Cost-reduction will be very important for new energy resources where cost pr. kWh is high. Some trends are:

  • Yearly price erosion of 5-10 % for power electronic converters.
  • Price reduction is compensated by that reduced prices gives increased application of power electronics; number of units sold is doubled the last 4 years and the same increase is predicted in future (ca. 15% pr. year at world market).
  • Increased efficiency has impact on life cycle cost, but so far purchase price seem to be most important.
  • Increased focus on energy-efficient electrical motors and generators.
  • Large gear-less motor drives are required to increase the reliability; i.e. direct-driven machines needed. Examples of applications are generators for wind mills in power range 2-3 MW and thrusters for electrical propulsion of ships in the same range of power.
  • Integration of power electronics and machines to obtain cost-effective solutions.
  • The market wants to buy functionality (a complete system) and not components.

 

Technology trends

Developments of the technologies are usually based on market needs. However, in some cases new technologies, or evolution of already existing technologies, enabling new product developments. Trends within power electronics and electrical machines are:

  • Increased current densities in power electronic devices, but with the same losses pr. footprint area of the device. This means reduced volume for the power rating. An yearly price erosion of 5-10 % is the driver. Trench-technology from the DRAM-industry is introduced.
  • IGBTs (Insulated Gate Bipolar Transistors) for increased current and voltage ratings are available. Devices for 4.5 kV is available and 6 kV devices are in development phase.
  • New materials and devices for power electronics are introduced; Silicon Carbide (SiC) is a new material being used in research for new power semiconductor devices. It can be operated at much higher temperatures than Si.
  • Technology development within power electronics makes it possible for small companies with high technological competence, within some markets, to compete successfully with large converter manufacturers.

New materials and magnetic concepts are developed.

  • By using permanent magnet materials new types of machines with high efficiency and reduced volume can be developed. Direct driven machines with substantial reduced volume and weight are possible to achieve.

 

Basis for research

Our basis for the research is the need of building up and improve the knowledge needed to meet the challenges in the field :

  • New energy-efficient systems for production, storage and conversion of energy.

The need of system as well as component knowledge is common for all such new systems using the electrical form of energy in the energy conversion process. Based on market- and technology trends the important areas are:

System

  • Knowledge about cost- and energy-optimal design of the total energy system, including life cycle cost for the system.
  • Optimal operation and control of the system. Knowledge of the primary energy source as well as components for energy storage is required.

Components

  • How to use new IGBT-devices in design of voltage fed converters for reduced cost. New devices require more intelligent drivers, and put increased demands on the mechanical design of converters. Designs for more high voltage devices will put high requirements on drivers and mechanical design.
  • Knowledge about how to utilize new materials as SiC and requirements set to converter design.
  • Use of new material in design of electrical machines.
  • Use of new electrical and magnetic solutions in machine design.
  • Development of new power electronic converters for new type of motors, as well as developing new control principles.
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