IMPORTANT LEGAL NOTICE - The information on this site is subject to a disclaimer and a copyright notice.

European FlagEuropa
The European Commission

Innovation in Europe banner

The new alliance between conventional and renewable energies

Operational wind generators connected to the network in Crete.

How are we to make the best use of renewable energies given the costs, safety aspects and quality of this service? The CARE project aims to take up this challenge. This issue is all the more urgent because new management of electricity distribution networks capable of taking account of the uncertain nature of some energy sources, such as the wind or the sun, is proving to be of particular value for isolated regions or islands.

You would have to be clairvoyant to predict the level of sunshine in some isolated places or the strength of the wind blowing over the Shetland

Islands, Crete or Corsica from one hour to the next or from one day to the next. Forecasting the real electricity demand from one moment to the next which is likely to originate from a precise place is just as complicated. But this is precisely what electricity companies, one of whose responsibilities is to continuously adjust supply to demand must do; they also have to prevent inadvertent variations of voltage or breaks in the current. It is the task of these companies to plan the way in which these different resources are to be used, including renewable energy sources.

Greece has been won over by wind

With its countless islands, Greece is a good, illustrative example. In Crete, for example, electricity is traditionally produced by 18 plants of different types, assisted by eight fully operational wind farms which are connected to the network. It is clear that the use of wind for energy is not new here, as can be seen from the famous plain of windmills. In May 1999, the first CARE prototype - an integrated management system for different sources of energy - was installed in Crete.

The power of wind generators depends on the great variability of the wind. In such conditions, how can the quality criteria which users require, namely a voltage of 230 V and a frequency of 50 Hz, be respected? "The CARE project is following on from another programme with a comparable aim but which was destined for smaller islands and hence for lower installed capacities" is the comment made by Komninos Diamantaras, scientific officer in the Research DG. The predecessor of CARE (1994?97) led to the creation of a prototype of an integrated management system for the Island of Lemnos. It made it possible to develop tools for predicting the force and direction of the wind.

Management in real time

It was planned that the new system would include this kind of tool, together with one module for forecasting load, another for the dynamic evaluation of security of supply and a third making it possible to optimise the use of resources in real time. Finally, a management unit was to propose strategies to the operator responsible for running the network. For their design, all these components required the use of techniques based on analytical methods or artificial intelligence.

"Designing each component of the system was a real challenge" stresses Sikos Hatziargyriou, Project Coordinator, Professor at the National Polytechnical University of Athens. "We also had to integrate all these components into a common environment and make sure that the final system was ergonomic so that it could be easily used by operators". One of the keys to its success in fact was due to the involvement of the staff called upon to use CARE at every stage of its development. Operators are able to understand this system, which is particularly user-friendly, after a one?day presentation. The essential information is permanently displayed on screen, such as the state of the network (electricity demand, quota of wind energy, etc.) at the present moment and in the previous few hours, together with forecasts for the hours to come. On the basis of these data, CARE puts forward strategies and the operator decides what to do.

A multi-energy system

What is more, the system is sufficiently open to integrate other energy sources, such as solar thermal, photovoltaic and micro-hydraulic energy, and CARE's successor, called MORECARE, is already up and running. The wind prediction module will be improved before being tested in Ireland. The new prototype will be installed in Madeira and Crete.

Initial evaluations referring to a period of six weeks are more than promising. Less than 5% of errors were recorded for electricity demand forecasts. The security module functioned well. What is more, the system made it possible to economise approximately 3% of the daily fuel used in Crete. The next stage is to conduct an awareness campaign regarding this new approach with the electricity companies.

Advanced control advice for power systems with large scale integration of renewable energy sources. CARE



Nikos Hatziargyriou
Institute of Communication and Computer Systems
National Technical University of Athens
9, Heroon Polytechniou
15773 Zografou
Athènes - Greece
Fax : +30 1 772 36 59
E-mail :

-Institute of Communication and Computer Systems, National Technical University of Athens, Greece (coordinator)
- Transmission sector of Crete-Rhodes, Heraklion, Greece
- Direction of Alternative Energy Forms, Athens, Greece
- Institut des systèmes d'énergie et informatique (INESC), Porto, Portugal
- ARMINES, Ecole des Mines de Paris, Sophia-Antipolis, France
- Rutherford Appleton Laboratory (DRAL), Didcot, United Kingdom

With the CARE energy management system, an operator can constantly check the current state of the network, the situation in previous hours and the forecasts for the next few hours.