CAPITALIZATION METHODS OF THE HYDRO – ENERGETIC MICROPOTENTIAL OF ROMANIA SĂRĂCUȚ -ARDELEAN ANDREI -FLORIN1 1 PhD-Student, University of Oradea,… [616614]

CAPITALIZATION METHODS OF THE HYDRO –
ENERGETIC MICROPOTENTIAL OF ROMANIA

SĂRĂCUȚ -ARDELEAN ANDREI -FLORIN1

1 PhD-Student: [anonimizat], Engineering Sciences Doctoral School
E-mails: [anonimizat]

Abstract
In this paper a preliminary analysis of hybrid renewable energy systems (HRES) able to generate at
least 100 kW electric power is carried out. Critical is sues related to energy storage variants were also considered
for periods of time when renewable sources are not sufficient to ensure the electricity consumption needs.
Restrictions on the installed power of small farms that are in isolated locations and cannot connect to NPS
generally diminish productive activities and, implicitly, profit. Depending on the renewable energy resources
(sun, wind, hydro) the characteristics of the isolated location of the work point, the optimal HRES system
required for an efficient operation of the agricultural farm even under isolated conditions can be determined by
the synthesis elaborated in this paper. Renewable energies that are characteristic to abiotic environment have
been approached, describing the current technological methods of transforming them into electricity. The
mathematical model of the process of generating electricity from renewable sources h as been elaborated in order
to perform the global energy calculation of the optimum hybrid system required for the isolated farm. These
elements lead to the determination of the technical -economic indicator ζ €/kW of the HRES system in the
management of th e agricultural farm from the perspective of a sustainable agriculture that produces more with
lower costs and in environmentally friendly conditions.

Introduction
Energy is conceptually defined as a state function of a physical or chemical process. It can be obtained
from exhaustible resources (non -renewable energy) or from the Sun and other inexhaustible resources
(renewable energy) through conversion technologies in various forms of energy transfer. Table 1 shows the
renewable energy sources (RES), the c urrent conversion technologies used and the energy transfer form of the
application, (ECA, 2018)

Table 1 Renewable energy sources, technologies and applications (ECA, 2018)

Global use of non -renewable energy (coal, oil, natural gas) also has unwanted effects such as
greenhouse gas emissions that have fu elled global warming, acid rain, ecological disasters or environmental
pollution. Through current clean energy conversion technologies, renewable energy resources are becoming
increasingly valued. In this context, renewable energy is a cross -cutting priori ty relevant to many EU policy
areas. The EU provides support for renewable energy under several funding programmers , like the European
Regional Development Fund (ERDF), the European Agricultural Fund for Rural Development (EAFRD) as well
as the Horizon 2020 and LIFE programmers . In Romania, in the agricultural sector, farmers become more and
more interested in renewable energy sources (Brunswick, 2019). Fortunately, there are several renewable or
alternative energy options available. However, it is often hard to identify which of the technologies are best
suited to a specific farm operation. Fig.1 illustrates the country's energy potential for the following renewable
resources: a) sun; b) wind and c) rivers. Currently, converting solar energy into electricity directly through
photovoltaic panels is the easiest method used globally to obtain electricity in the form of direct current from
solar radiation reaching the surface of the Earth. At the upper limit of the atmosphere, the radiated sunshine
energy is 1367 W/m2 and measured at ground level on a surface perpendicular to the direction of the rays, can

generally reach 1000 W/m2. Analyzing the map of solar radiation at ground level in Romania (Fig.1a), (SolarGis,
2019) agricultural farms located in the south pa rt of the country, such as Oltenia, Baragan and Dobrogea, are
benefiting the use of solar energy. For the exploitation of the wind resource at the location of the isolated farm, it
is of interest to know the variation of the wind speed up to a height of 50 …150 m in relation to the land surface
and statistically in time, throughout the entire calendar year. Because wind power is proportional to its cube
velocity (Ehrlich R., 2013), for designing and manufacturing wind power conversion systems, it is recommen ded
that farmers first consult their farm positioning on the map from a wind resource point of view. From the
analysis of the wind map of Romania presented in Fig. 1b), (AddEnergy, 2019) three wind potential areas are
distinguished for the following averag e wind speeds: ~ 8 m/s – mountain area; ~ 6 m/s – the second area with
wind potential that can be used cost -effectively (Black Sea coast, Danube Delta and northern Dobrogea, areas
where wind energy ex ploitation is favored by lower wind turbulence); 4…5 m/s – the third area with
considerable potential, which is the Barlad Plateau. Also, favorable wind speeds are reported in other more
restricted areas in the western part of the country.

Fig. 1 – The country's energy potential for the renewable resources (RO)

The map of Romania's hydrographic network is presented in Fig.1c). Except rivers in the Dobrogea
area, most of the running waters spring from the Carpathians and belong to the Danube river basin. Due to the
varied configuration of Romania's terrain, the flowing water network is radially disposed. The main flowing
waters have a longitudinal profile characterized by large slopes in the mountainou s region where the water
velocity is v > 1 m/s, while in the plain regions the water flow is more uniform, with lower velocities v < 1 m/s.
The most important RES in Romania is hydro energy (WWF, 2019). Agricultural farms located in the river
meadows in th e country's large river basins can benefit from the hydro -energetic micro -potential of fast rivers
through simple facilities made to exploit the kinetic energy of flowing waters. According to the RES maps in
Fig.1, wherever it is located within the country , an isolated farm (without the possibility of connecting to the
NPS) benefits from a dominant source of renewable energy.

Fig. 2 – Diagram bloc of a stand -alone hybrid energy system (Zohuri B., 2018)

The other renewable resources are complementary so that a properly sized HRES system can
continuously provide, through the integrated energy storage system, the power needed to operate in off -grid
mode. HRES is actually a combination of two or more renewable energy sources, or at least one renewable and
one conventional source. HRES can be connected or not to the grid. For the presented case, the HRES system
operates in stand -alone mode (off -grid mode). The hybrid energy system is defined as a combination of energy
sources with different characteristics and an energy storage environment. With regard to standalone applications,

choosing t he optimal hybrid energy system is a challenging process due to many reasons, such as: determining
the best combination of sources; reduce initial capital investment; reliability of power supply; system
components, etc. Fig. 2 (Zohuri B., 2018) shows the b lock diagram of an autonomous hybrid system for small
farms located in isolated locations. HRES hardware and software components are included in the Control System
block and they perform process control and HRES efficiency improvement.
The use in situ of HRES systems for isolated locations is a new step towards decentralized
electrification. The systems can be grouped into si ngle-phase or three -phase MNs, which feed local consumers
and/or small farms. The interconnection of these sources of electricity in parallel on a common network raises
many problems, caused mainly by their different functioning mode, by the different inst alled electric power, as
well as by other particular aspects of each system. Often, in a HRES type system, in addition to renewable
energy sources, conventional fossil fuel generators, generally Diesel engine generators, are used intermittently.
They are i ntroduced into the system when the demand for electricity of the consumers exceeds the capacity of
the renewable sources. Combinations of more than two renewable sources become complex hybrid systems
requiring higher -order investments. Reducing the techno -economic ζ [€/kW] indicator of such a hybrid energy
system involves complex studies and detailed analyses before manufacturing. Fig. 3 shows the main systems of a
hybrid HRES network: solar, wind, hydrokinetic, energy storage.

Fig. 3 – Micro -grid topology of hybrid renewable energy systems Source (MICROREN,
2015)