Renewable Sources
1. The water
The water has great importance in life, due to their multiples uses, hydration, cooking, hygiene, agriculture, cattle, leisure time, navigation and generation of electricity. Therefore, it is addressed to the man use it in a conscious way avoiding that the next generations face the shortage of this resource.
The water occupies around three quarters of the surface of the Earth: of the 510 million km2 of the surface of the globe, 365 million of km2 they are destinated to the water, while the continents occupy only 145 million of km2.
From all existent water in the planet 97,3% is salt water, in other words, inappropriate for the consumption, 2,15% are at the glaciers and only 0,6% are fresh water. Of all fresh water 98,5% is underground water and 1,5% is at the rivers and lakes, as displays the illustration 1.
The distribution of the water in the planet is unequal, because there are areas with abundance of water and others with great shortage. Consequently, the first human groups tried to inhabit areas with rain enough or close to rivers guaranteeing, thus, their survival.
With the fast growth of the population and with the demands of larger comfort, the water was being used in an unconscious manner, in other words, presenting great wastes. Therefore, it is important to know the best way of to preserve it, mainly in the river bed, besides the cares concerning its reception, transport and distribution.
2. Hydraulic energy
The use of the hydro power energy was one of the first ways of substitution of the animal work for the mechanic, particularly for water pumping and grinding of grains. It was favored due to the following characteristics: readiness of resources, easiness of use and, mainly its renewable character.
The hydraulic energy results from the solar irradiation and from the gravitational potential energy, that provokes the evaporation, condensation and precipitation of the water on the terrestrial surface, it is the existent energy in the water and that in certain flow conditions and height and head, can be used to move machines. Moreover, the hydraulic energy is converted in mechanical energy. Unlike the other renewable sources, it represents a significant portion of the world energetic matrix and uses technologies properly consolidated. Now, it is the main generating source of electric power for several countries and answers for about 17% of all the electricity generated in the world.
In Brazil, water and energy have a historical interdependence. The contribution of the hydraulic energy to the economical development of the Country has been expressive, not only in the service of the several demands of the economy - industrial, agricultural, commercial activities and services – but also the society, either being in the improvement of the comfort of the houses or in the increase of people’s life. It also plays important role in the integration and in the development of distant regions of the big urban and industrial centers.
The contribution of the hydraulic energy in the national energy matrix is around 79% of the whole electric power generated at the country. In spite of the increase tendency of other sources, due to socioeconomic and environmental restrictions of hydroelectric projects and to the technological progresses in the use of non conventional sources, all indicates that the hydro power will continue being, for many years, the main generating source of electric power of Brazil. Although the largest remaining potentials are located in areas with strong environmental and distancy restrictions of the main consuming centers, it is considered that, next years, at least 50% of the need of expansion of the generation capacity has hydro power origin.
The policy incentive to the decentralized electric power generation promotes a growing participation of alternative sources in the national energy matrix, and in that context, the small ones will certainly have an important role carry out.
3. Flow
It is the relationship of the volume of water measured in liters or cubic meters by the time in seconds, minutes or hours, necessary to fill a reservoir such as: tank, drum, etc.
The flow is presented by the letter Q and it can be made calculations by the formula:
Q = v/t
Where :
Q = Flow in cubic meters a second
v = Volume of the reservoir
t = Time
This flow definition is applied in any flow of water. To measure the flow there is just nedded to use a hose connected to a funnel, a reservoir of a liter and a clock or chronometer. Afterwards, the time that the water takes to fill out the reservoir is recorded. To find the flow it is necessary to divide the volume for the time spent to fill out the reservoir.
In any study for implementation of a plant the measurement of the flow is fundamental for the determination of the potential of the plant.
4. Local Height of Water head
When using the hydraulic energy of the river, in the start up of machines for pumping or generation of electricity, it is important to verify if there is a difference among the height of the point of reception of the water and the place where the hydraulic equipment will be installed. That height is defined as head height [H].
5. Machines moved by the water
The originating energy from the water streams, can be used to work several types of machines that have different functions, such as:
Monjolo - machine used in the grinding of the similar grains to the crusher;
Hydraulic sheep/ram - machine that works as a bomb;
Water wheel - machine used to pump water and, also, to generate electric power in small scales;
Hydraulic turbine - machine used in hydroelectric palnts and coupled to a generator that transforms the mechanical energy in electric.
In order to operate them it is necessary to accomplish technical studies for the creation of reservoirs or small channels with the purpose of accumulating and diverting part of the water of the rivers.
6. Monjolo
The monjolo is simple of building; therefore it can be done with wood trunk.
It should be put in a place where height of the fall exists to install a gutter, whose function is to capture and to divert part of the flow of water inside of a bucket that works as a reservoir.
In the measure that this reservoir is filled out, the weight of the water wins the weight of the trunk making it lift the other extremity. At this time, the water is pulled out and as the weight of the remaining water in the reservoir is smaller than the weight of the trunk, this returns to the initial position with enough force for grinding grains that will be inside of a crusher.
7. Hydraulic sheep/ram
The hydraulic ram is a low cost machine, used to pump small amount of water. It presents use easiness and has little maintenance.
To work it there is no need of electric power or any fuel, because it uses as energy the own head of water. The only pieces that can suffer damages throughout time area: the pulse and repression valve that should be changed.
It is capable to take advantage from the effect that elapses from the fast interruption of the water movement in a given direction. With this interruption, a pressure increase happens inside of the machine being enough to open the repression valve, which leaves the water that it is transported by a hose until a local reservoir above the hydraulic sheep.
8 . Water Wheel
The use of the water wheels is very old. It is dated that in 2.000 a.C, in Egypt, it was already used for pumping. At first it had the structure done by rustic wood and pails arrested to that structure forming the buckets. With the progress of the technology this structure was improved until arriving in the current models.
The operation occurs from a deviation of the flow of local water that is taken until the wheel. In roder to make that deviation can be used, a tube of PVC, steel galvanized plates, wood gutter or masonry with height from 10 to 20cm of the top of the wheel so that the water when falling on the shovels makes possible to move.
The rotation speed is very low, which is, from 1 to 40 turns per minute, but despite that it can be used to move mills, sawmills; to generate electricity (100 to 3000 Watts) and to pump water to a reservoir.
It should be installed on a wood base, brick or concrete and very evened in order to obtain a good operation.
9. Hydraulic turbines
In the hydroelectric plants the group generators are constituted by the turbine group (rotor more spiral box), speed governor or of load and generator. The turbines are characterized by different types of rotors.
The turbines are specified in function of the electric potency to be generated, could have horizontal axis for low potencies or vertical axis for high potencies.
In micro hydro power plants, the used turbines are usually built with horizontal axis. Depending on the local conditions of flow and head height, a turbine can be more efficient than the other. Like this, it becomes necessary to evaluate technically and economically the best option. (* to include linkTurbinas)
10. Brazilian Hydroelectric potential
The value of the Brazilian hydroelectric potential is composed by: the sum of the steemed portion (remainder + individualized) with the inventoried. The steemed potential is resulting from the sum of the studies:
• The ones of remaining potential - estimate result accomplished in the office, from existent data - without any complemental rising - being considered a passage of a stream of water, placed in the river bed, without determining the place of implantation of the potential;
• Individualized - result from the estimation accomplished at office to a certain place, starting from existent data or expedite risings, without any detailed rising. The inventoried portion includes plants in different levels of studies - inventory, viability and basic projects - besides potentials under construction and operation (ELETROBRÁS, 2004).
The inventoried potential is result of the sum of the potentials:
• Only inventoried - result of the study of the hydrograph basin, accomplished by the determination of its hydroelectric potentials, by the choice of the best alternative of head division, that constitutes the group of compatible potentials, and the developed projects, in order to obtain an evaluation of the available energy, of the environmental impacts and of the costs of implantation of the enterprises;
• With viability study - result of the global conception of the potential considerering its technical andd economical optimization, in order to allow the elaboration of the documents for auction. This study comprehends the determination of the main structures and of the local infrastructure works and tof he definition of the respective influence area, of the multiple use of the water and of the effects on the environment;
• With basic project - detailed use and in depth, with defined budget, that allows the elaboration of the documents of auction of civil works and supply of the electromechanical equipments;
• In construction – potential that had initiate constrction, without any generating unit in operation;
• In operation - the enterprises in operation constitute the installed capacity.
The uses are only considered for statistical purposes in the steps: "inventory", "viability" or "basic project", if the respective studies have been approved by the conceiving agent.
The Brazilian hydroelectric potential presents around 260 GW. However, only 68% of that potential were inventoried. Among the basins with potential, it stands out the Amazonas River and Paraná River ones. In the Amazon Basin stands out Rio Xingu's sub-basin, with 12,7% of the potential inventoried of the country. Other sub-basins of Amazon basin, whose estimated potentials are considerable, are the Rio Tapajós´s River one, the Madeira’s River and the Negro River. In the Basin of Tocantins, it stands out Itacaiunas's River sub-basin and others, with 6,1% of the inventoried Brazilian potential. In the Basin of San Francisco, the prominence is going to Moxotó's River sub-basin and others, that represents 9,9% of the inventoried potential. In the Basin of Paraná, several sub-basins exist with great potentials, among them to Paraná, Paranapanema and other, with 8,1% of the hydroelectric potential inventoried of the country.
11. Installed capacity
In absolute terms, the five larger producers of hydroelectric energy in the world are Canada, China, Brazil, United States and Russia, respectively. In 2001, those countries were responsible for almost 50% of all the world hydroelectric energy production (AIE, 2003).
Less than 60% of the hydroelectric installed capacity in Brazil is in Paraná's River Basin. Other important basins are the one of São Francisco River and the one of Tocantins River, with 16% and 12%, respectively, of the installed capacity of the country. The basins with smaller installed potency are: Ocean Atlântico, North/Northest and Amazon, that asum up only 1,5% of the installed capacity in Brazil.
In the Paraná Basin it they stand out Paranaíba's River sub-basins, Grande River, Paranapanema River and Iguaçu River, with indexes that vary from 10,1% to 13,2% of the installed capacity of the country. In the San Francisco Basin, stands out the sub-basin of the rivers San Francisco, Moxotó and others, where they are located in the hydroelectric power stations of Xingó and Paulo Afonso IV, that sums up 5.460 MW of installed potency. In the Basin of Tocantins, it stands out the sub-basin of Tocantins Itacaiúnas River and olthars, where it is located the Hydroelectric power station of Tucuruí, whose installed capacity can be duplicated in a close future.
12. Bibliographical reference
TIAGO FILHO, Geraldo Lúcio. Aproveitamento de Energia Hidráulica, Grupo Agroenergia EFEI
Catálogo Rochefer. Bombas hidráulicas – Manual de Seleção de Bombas e Rodas
Catálogo Rochefer. MS-6 Multiset, Manual Técnico
TIAGO FILHO, Geraldo Lúcio. Rodas d’água, Grupo Agroenergia – DME –IEM – EFEI
TIAGO FILHO, Geraldo Lúcio. Turbinas hidráulicas para microcentrais hidrelétricas, Grupo Agroenergia – EFEI
Catálogo Moller – Turbinas hidráulicas WIRZ Ltda
Fundição Corradi – Divisão de Máquinas Agrícolas, Roda Pelton Completa
TIAGO FILHO, Geraldo Lúcio & VIANA, Augusto Nelson Carvalho. Carneiro hidráulico, EFEI, 1988
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