CAPITALIZATION METHODS OF THE HYDRO – ENERGETIC MICROPOTENTIAL OF ROMANIA SĂRĂCUȚ -ARDELEAN ANDREI -FLORIN1 1 PhD-Student, University of Oradea,… [616608]

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
Nowadays the development of renewable energies has become a necessity. The increase in electricity
demands combined with international agreements to reduce greenhouse gas emissions to limit fossil energy use
and ensure security of supply by reducing the de pendence on the importation of fossil fuels are strong arguments
for the development of renewable energies. Hydropower is the foremost electricity -producing renewable energy
technology in terms of installed capacity and energy yield, both in Europe and the world. Developing a small
hydropower (SHP) site is not a simple task since small hydropower is not simply a reduced version of large
hydro plant. Thus it is essential to develop and produce equipments specific to small power plants so as to assure
the fun damental exigencies of simplicity, high energy efficiency, maximum reliability and easy maintenance.
Currently, most efforts concerning civil engineering aim at standardizing design and technology, in
order to reach an optimal development of SHP plants (S HPP) and integration with the local environment while
minimizing costs. Besides the works of civil engineering, the industry of the small hydropower associates
mechanical and electrical high technologies combined with highly developed monitoring and survei llance
processes.
The paper describes the criterion of micro hydropower development typification, the classification of
micro hydropower plants depending of available head, as well as the possibilities of capitalization and
consumption of the produced en ergy.

Keywords: micro hydropower, micropotential, hydro scheme, small HPP, powerhouse, turbines.

Introduction
Nowadays the development of renewable energies has become a necessity since the climate change due
to CO 2 emissions has been defined as the major environmental challenge to be faced by the International
Community. The community targets are clearly stated at The Rio conference in 1992, The Kyoto protocol in
1997, and into the European White Paper “Energy for t he future: renewable sources of energy” and finally the
“Directive/77/EC of the European Parliament and of the European Council of 27 September 2001 on the
promotion of electricity produced from renewable energy sources in the internal electricity market”, which gives
a clear signal that greater use of renewable energy is necessary to reduce environmental impacts, ensure security
of supply and create a sustainable energy system.
Small hydropower (SHP) has a key role to play in the development of Europe’s renewable energy
resources, particularly in view of the new enlarged European Union and its increasing electricity demand, and
also, interest is increasing in developing SHP because large hydro sites are generally already being exploited in
many European c ountries. Small hydropower is a much more concentrated energy resource than other
renewable, it is predictable, non -varying and has a higher capacity factor and long life. The main advantages of
SHP are: it is a clean and renewable energy source, contribut es towards sustainable development, and respects
the environment (no green house gases emissions); it ensure a minimum flow downstream (the reserved flow)
that guarantees downstream life of aquatic organisms; SHP mobilizes financial resources and contribut es to the
economic development of small scattered populations, ensuring autonomous and reliable energy for the long
term; SHP plants create local jobs for the monitoring of the running phase of the plant; by being located close to
the consumers, transmissi on losses can be reduced and the electricity supply lines are eased; assist in maintaining
river basins by allowing the recovery of wastes that flow in the river stream; SHP plants, if well -equipped, with
fish ladders are not an obstacle for migratory fish .
SHP should be distinguished from the usual hydropower because a small power plant can not be
realized just by a simple geometric reduction of a big one. Such a process would lead to an excessive damage of
the performances in case of a non -controlled si mplification of the turbine geometry or to an expensive, complex
and of a delicate exploitation construction. Until now, SHP has not developed itself as much as the other RES.
SHP development is slowed down by numerous institutional barriers and by the wro ng idea that it is a mature
technology and that SHP plants injure water streams regarding ecology and leisure interests. The purpose of this
paper is to presents the possibilities of typification of SHP plants (SHPP).

SHP plants typification
The objective of a hydro power scheme is to convert the potential energy of water, flowing in a stream
with a certain fall (head), into electric energy. The power of the scheme is proportional to the flow (m3 /s) and to
the head (m).

Criterions of SHPP schem es typification
The criteria of SHP plants schemes typification can be made on various points of views: considering the
location of the micropotential to be used: upstream of the existing developments, where hydroenergetic potential
unused still exists ; on the downstream area of the rivers, after the existing developments; by using the
unexploited flow and heads within the existing hydroenergetic developments; into the existing hydrotechnic
works (water supply, irrigation, flood prevention, fisheries or tourism); considering the head: high head
schemes; medium head schemes; low head schemes; regarding the types of turbine employed: schemes which
use Pelton turbines; schemes which use Francis turbines; schemes which use Kaplan turbines; schemes which
use bulb turbines; schemes which use Banki turbines; schemes which use EOS turbines; considering the manner
in which the produced electric energy is consumed: the energy can be consumed in the production place, or it
can be supplied in the local distributio n network.

Types of development schemes

The gross head of a river sector is given by:

(1)

with z1, z2 represents the absolute elevation of the sector ends, and v1, v2 the average velocities in the
given sections.
The hydropower developments gather the flow and heads on short river sectors, assuring and increasing
in the main time the energy produ ction. The increased head of a small hydropower plant can be created in quite
number of ways, being the most known the following ones: the local rise of water level: it is succeeded by
building a dam across a stream which increase the water level and creat es a larger flow section upstream; it is
usually used in river valleys areas; the kinetic terms are very important diverting part of the stream, by a channel
with a smaller slope and with a minimum of headlosses; the combined solution, which imply the loca l rise of
water level by a dam, and then the water diversion; the power house can be aerian or underground; they are
typically for the upper river courses; the kinetic terms can be ignored. The hydromechanics and electrical
equipments are very important in electing the type of scheme to be realized. The hydraulic turbines, the electric
generators, the vanes, the annexes, are plant specific, while the electrical connection stations, the command
chambers, the electric transformers are not. The typical schemes are particularized according to the relief
characteristics, river slope, geological features, land use in the area, the turbine type used and so on. A typical
development for a SHP plant scheme, which involves a dam, is presented in figure 1.

Fig. 1. T ypical SHP plant scheme

SHPP classification according to the head

As mentioned before, the SHP plants can be classified as follow: _ high head schemes, with ³100m Hbr,
usually used in mountain area (upper courses of rivers); _ medium head schemes, 30m £ £100m Hbr , usually
used in mountain and hills areas (medium river courses); _ low head schemes, 2m £ £ 30m Hbr, typically used in
river valleys (lower river courses).

Turbines used in SHPP

A large spectrum of turbines can be employed, according to the available flow and heads: Pelton,
Francis, Kaplan, Bulb, Banki, EOS, Turgo. The choice of the right turbine for a particular application must relay
on the specific speed of the turbine, ns, given by:
(2)

and the gross head, Hbr (see table 1).

Table 1 Range of specific speed and heads

Energy consumption

The energy produces can be used directly to the production place, instead of using the electricity from
the local grid. Another option is to supply the electricity into the local grid. Economically, the most feasible
solution is to consume as much at possible the production location, and to supply only the surplus into the local
electric grid.
Hydroelectric power, as it has in the past, will continue to be a significant player in the electric power
industry. However, there remain many challenges ahead as environmental and legal issues are played out.

Specific features of SHPP

The hydropower schemes of SHPP have a specific construction, different from the traditional
hydropower developments. SHPP have to be simple, robust and in the same time to assure the energy production
specified.
The hydropower schemes of a SHPP usually contain: the retention sill; the lateral water intake; the
desilting basin and the forebay; the conveyance structure which carries the design flow from the water intake to
the power house; the power house which houses the turbine, generator and controller units; the tailrace which
allows the water to flow back to the stream after it has passed through the turbine.
The water intake must be able to divert the required amount of water to the power house, with the
minimum possible headlosses. The intake serves as a transition between a s tream that can vary from a trickle to a
raging torrent, and a controlled flow of water both in quality and quantity. Its design, based on geological,
hydraulic, structural and economic considerations, requires special care to avoid unnecessary maintenance and
operational problems that cannot be easily remedied and would have to be tolerated for the life of the project. A
very important step is to properly choose the intake type for the proposed scheme. The location of the intake
depends on a number of facto rs, such as submergence, geotechnical conditions, environmental considerations
where necessary. The orientation of the intake entrance to the flow is a crucial factor in minimizing debris
accumulation on the trashrack, a source of future maintenance proble ms and plant stoppages. The intake should
not be located in an area of still water, far from the spillway, because the eddy currents common in such waters

will entrain and accumulate trash at the entrance. The water intake should be equipped with a trashra ck to
minimise the amount of debris and sediment carried by the incoming water, a settling basin where the flow
velocity is reduced, a sluicing system to flush the deposited silt, sand, gravel and pebbles with a minimum of
water loss, and a spillway to divert the excess water.
The penstock pipe transports water under pressure from the forebay tank to the turbine, where the
potential energy of the water is converted into kinetic energy in order to rotate the turbine. This task may not
appear as difficult , considering the familiarity of water pipes; however, deciding the most economical
arrangement for a penstock is not so simple. Penstocks can be installed over or under the ground, depending on
factors such as the nature of the ground itself, the penstock material, the ambient temperatures and the
environmental requirements.
The characteristics of a penstock are materials (selected according to the ground conditions,
accessibility, weight, jointing system and cost), diameter (selected to reduce frictional losses within the penstock
to an acceptable level), wall thickness (selected to resist the maximum internal hydraulic pressure, including
transient surge pressure that will occur) and type of joint (if necessary).
In a small hydropower scheme the role of the powerhouse is to protect from the weather hardships the
electromechanical equipment that convert the potential energy of water into electricity. The number, type and
power of the turbo -generators, their configuration, the scheme head and the geomorpho logy of the site control
the shape and size of the building.
The compensation basin assures the uninterrupted function of the plant during the low flow periods,
when the river flow is less then the needed one to the turbines. They also control the flow af ter passing through
the turbine, according to the local necessities. Usually, their capacity is rather small, and the water level varies to
few meters at most, depending on the ground conditions.
After passing through the turbine the water returns to the river trough a short canal called a tailrace.
Impulse turbines can have relatively high exit velocities, so the tailrace should be designed to ensure that the
powerhouse would not be undermined. Protection with rock riprap or concrete aprons should be provided
between the powerhouse and the stream. The design should also ensure that during relatively high flows the
water in the tailrace does not rise so far that it interferes with the turbine runner. With a reaction turbine the level
of the water in the tailrace influences the operation of the turbine and more specifically the onset of cavitation.
This level also determines the available net head and in low head systems may have a decisive influence
on the economic results.

R E F E RENCE S
[1]. V. Nistr eanu, Viorica Nistreanu , Amenajarea resurselor de apa si impactul asupra mediului, Editura BREN,
1999.
[2]. *** Layman's Handbook on how to develop a small hydro site, Second Edition, 1998.
[3]. *** Evaluarea micropotentialului hidroenergetic românesc, sursa regenerabila de energie, în vederea
identificarii de amplasamente pentru dezvoltarea investitiilor în acest sector, Contract MEC 2006 -2007.