StatusThe thesis was presented on the 15 March, 2022
Approved by NCAA on the 1 July, 2022
Abstract– 0.87 Mb / in romanian
– 0.85 Mb / in english
5.29 Mb /
Author – EFREMOV Cristina. Title – Contributions to increase the flexibility of the energy system in
order to integrate renewable energy sources. Doctoral thesis for PhD qualification in technical
sciences, 221.01. Energy systems and technologies specialty. 2021Chisinau.
Thesis structure: The paper comprises an introduction, four chapters, general conclusions and
recommendations, 291 references, 7 annexes, 151 pages, 52 figures, 19 tables. The results are
published in 14 scientific papers.
Keywords: flexibility, renewable energy sources, energy transition, energy storage, roadmap,
cogeneration, variability, thermal energy consumption in territorial profile. Field of study – technical
The purpose of the thesis is to identify and analyze a package of measures / actions to increase the
flexibility of the national electricity system and the thermal energy systems in the long-term
perspective in order to ensure the transition to 100% energy from renewable sources.
Objectives of the paper: Studying a series of innovative technologies with the contribution to increase
the system flexibility, with the evaluation of the potential for increasing RES capacities, the analysis
of storage possibilities applied in the both systems: electrical and thermal,
The novelty and scientific originality. Development of theoretical-methodological elements for
implementing measures to increase flexibility adapted to the level and specificity of the Republic of
The result obtained that brings a scientific-practical contribution in solving the problem of the
variability RES by increasing the flexibility of the energy system.
Theoretical value. The thesis brings scientific contributions in identifying the most efficient
distributed solutions to increase the flexibility of the main elements of the national energy system in
order to integrate the highest possible production capacities of the renewable energy sources.
The applicative value of the thesis. The paper developed a roadmap with 12 conceptual elements that
can form the basis of the national policies in the Republic of Moldova with long-term development in
the Energy Strategy, in the perspective of 2050; was addressed for the first time the issue of
determining the total territorial heat consumption in the country; was analyzed the specific situation
according to a wide penetration of photovoltaic power plants in the energy system of the Republic of
Moldova; building of pumped storage hydro power plants (CHEAP), as well as investigattion of the
solutions for the combined use of CHEAP and BESS.
Implementation of research results. The study on the potential of energy cogeneration and
electrification of the heating sector was developed within the Ministry of Infrastructure and Regional
Development. The important results of the paper will be used in the teaching process at the Faculty of
Energy and Electrical Engineering, as well as in the design-development actions in the field.