RICERCA ITALIANA     

Renewable generation sustainable development in liberalised electric power systems: technical, economical and management aspects.

Università di Pisa

Abstract

The electric energy generation from renewable sources like wind and solar production represents the grater part of installations. This phenomenon has expanded in the last decades very slowly, especially as reply to local solutions for isolated loads. But in the last three years the renewable installed capacity, and in particular the wind power plants, grew a lot and remarkable expansions are foreseen for some other years.
Beyond the real disposability of renewable energy sources, their massive use in electric power systems in general, and in the Italian one in particular, substantially presents two types of problems. The first one concerns the effect of these sources, and in particular the not programmable, in the electrical system where they are installed. The problem is substantially related to the frequency and voltage regulations when the contribution of this kind of sources becomes important. Moreover the influence of DSM and the possible use of new storage technologies, like hydrogen, integrated with renewable generation have to be investigated.
The second problem is relevant to the economic impact of renewable sources development, especially in the Italian context taking into account that the green certificate instrument is actually working. Everybody knows that costs related to the growth of new renewable sources are not adequately remunerated with actual prices of electric energy and therefore these sources have to be economically supported. The new European Directive 2001/77/CE related to the promotion of renewable sources in the energy markets, recently acknowledged by the Italian Government, provides an increment of these types of sources. In this background, the growth of new generation could produce an over-production from renewable sources, with a drop in prices of green certificates that would induce investors to disinvest in this sector. On the other side, the increasing of this kind of production is necessary to define "green certificate" energy increases consistent with the real development of renewable sources. Lastly, the renewable generation management aspects have to be considered.
The proposed research project is organised into four items, each developed in preferential subjects. The main items are:
a) technical aspects relevant to the use of new renewable generation sources into an electric power system;
b) development and economical aspects of new renewable generation sources;
c) the management of non programmable renewable generation sources in a liberalized electric power system;
d) new renewable generation and storage technologies. <<<

Principal Investigator

Paolo PELACCHI Università di PISA

Research Objectives

Available scientific literature related to the topic highlights that the renewable sources use problems related to electric energy production has been faced, till now, more from the point of view of single components that from the point of view of the electric system.
In other words, it has been analysed thoroughly studies related to the development of new techniques for conversion of energy produced by these sources, convinced that it would represent a marginal amount and so their use didn't cause special problems to the system.
Recent development of this new sources and their massive use in electric power systems, require an analysis in development and management point of view of the whole electric system; in other words, it is necessary to verify problems and restrictions that their introduction could cause into an electric power system that has not been designed for such applications.
Therefore, preferential subjects of the proposed research project are:
a) analysis of technical problems relevant to the introduction in an electric system of new renewable energy, with special reference to non programmable sources, like problems related to the frequency and voltage control, to the reduction of harmonics and to the protection systems set up;
b) analysis of supportable development of the new renewable sources and their economic support with particular reference to the temporal growth of new plants and the corresponding financing possibility (like green certificates or other sort of certifications);
c) settlement of optimal management of new renewable sources, with special reference to non programmable ones, also verifying the possibility of their coordinated management with load and conventional and non conventional storage. <<<

First Results

The estimated partial results of the first phase are:
1) experimental data disposability;
2) new renewable generation plants annual development as a function of conventional generation and consequent evaluation of green certificates;
3) renewable generation plants development limits relevant to frequency and voltage regulation and frequency stability;
4) remarks on possible increase of energy production and reliability of renewable generators;
5) analysis of planning and management criteria oriented to the optimum units allocation into the transmission and distribution networks;
6) analysis of possible criteria for a renewable generation units management coordinated with load and conventional or non conventional energy storage;
7) analysis of possible reliability and power quality criteria in systems where renewable generation units are installed.The estimated partial results of the second phase are:
1) new renewable generation plants development and relevant economic support mechanisms (green certificates) in Italy;
2) definition criteria of renewable generation plants planning and management in a liberalised electric system which take into account also innovative storage systems and coordinated load management;
3) definition criteria of reliability and power quality in a liberalised electric system with a large amount of renewable generation plants which also consider generation sizes. <<<

Timescale

24 months

National and international background

In the last ten-years, all over the world we witness an increasing development of the use of new renewable sources for the generation of electric energy. This new phenomenon, promoted by the need to reduce as much as possible risks relevant to the increase of the emissions due to the use of fossil fuels, first of all the carbon dioxide, and also pressed by international agreements, as Kyoto's one, is growing very quickly. It is sufficient to think that, for example, wind generators power capacity installed in the world increased from 5000 MW in 1995 to almost 25000 Mw in 2001 and that , specially in Europe, in the same period it has increased from 2500 MW to about 18000 MW. In Italy too we are witnessing annual expansions of wind installed capacity by more than 50%. Such amount has to be raised by the contribution of other renewable sources (e.g. the "10000 photovoltaic roof" project).
Another relevant European element, and therefore important for Italy, is provided by the European Directive 2001/77/CE concerning the promotion of electric energy produced by renewable sources in the electric energy market, Directive that the Italian government has recently acknowledged. In particular, in such a Directive Italy undertook itself to raise production from new renewable sources.
The massive introduction of production units that use renewable sources, and in particular way non programmable sources like solar and wind, in electric systems where it is in progress a liberalization process proposes technical, economic and managerial problems that have to be analysed thoroughly into an overall vision of the system with the purpose of optimise the development and minimize the impact of this production on electric system. In particular, subjects related to the proposed topic are:
a) technical problems relevant to the introduction in an electric system of new renewable energy.
b) economics aspects of the development of renewable generation, taking into account new technologies;
c) management of the renewable non programmable energy in an electric liberalized system.
From the above considerations it is evident that the project tackles a large portion of topics related to renewable generation. That involves the need to define a large scientific basis of reference, that includes several topics.
The scientific basis that has to be taken as a reference must be considered in qualitative and not in quantitative terms, selecting particular bibliographic references oriented to the items of the study, as for the global project as for each single research unit.
Reported bibliographic references indicate the quantity and quality of available knowledge to develop the proposed study; It is easy to verify that knowledge concerns technical topics (e.g. [8], [10], [17], [20], [22], [32], [33] , [36]), economics topics (e.g. [1], [2], [3], [5]) and management themes (e.g. [4], [6], [7], [24], [25], [27], [28]). Coordination activity will be target to the accurate definition of the scientific starting basis that different research units have to assume as reference for targets that they themselves have detected. <<<