Mini-Hydro Electric Plants (Tony Jalloul – Faculty of Engineering – University of Balamand- 2002-03)
Abstract
Hydro technology, which is the utilization of energy generated from running water, is in use by man since his evolution. The hydro energy is used to irrigate, to transport and to generate electric power. Ancient Lebanese watermills are mainly used for irrigation and grinding. The inspiration of this proposal stem from the fact that if running water is used to turn very heavy millstones for crushing and grinding olives and grains, then a question will pose itself: why don't we use this "old" technology to turn a turbine to generate electricity?
The idea of generating using watermills is not new. However, it is recently put into effects by having world organization such as the UN and the EU sponsored projects in the third world countries.
The proposed work will have three main objectives: technical, economical and environmental aspects of watermills related to generating electricity from an old concept of using running water. The work will also have topographical map of existing ancient active and inactive watermills in North Lebanon and detailed analysis of selected sample sites.
Preambule
The utilization of watermills to generate electricity has been used effectively in Nepal since 1980. Nepal is one of the first countries where significant process has been done to upgrade watermills. Initially, local development was held by assembling a vertical-axis impulse turbine made with steel buckets and penstock pipe. This technique became known as the Multi-Purpose Power Unit (MPPU), however this technology being promoted through foreign aid programs because of its simplicity, similarity in principal to the traditional watermill and low cost [1].
Today, the hydroelectricity is a well-established technology. It is used by all countries and it is the principal source of electric power in 30 countries. In Lebanon, the produced hydroelectric power is no more than 4% of the total generated power [2]. Clearly, this minute percentage of generated hydroelectric power can be and should be increased especially in Lebanon where its climate, geographical, topographical and hydrological characteristics are strong incentives to better utilize our national wealth of WATER.
The nature and size of the rivers in Lebanon hinder large-scale hydroelectric generation. Thus, the emphasis must be on medium- and small-scale generation. The existing and future hydroelectric plants are classified as medium-scale. This proposal taps into small-scale generation; the "Mini-Hydro Electric Plant".
Ancient watermills have been widely used in Lebanon for mainly oilive crushing and grain grinding. The concept of these watermills can be effectively used to produce electricity. The development and installation of such watermills could play a significant social and economical role. These environmentally friendly watermills will have a direct impact on remote scattered villages that may lead not only to tourism but also to enable them to generate their own need of electric energy and in some cases excess generated electricity can be sold off.
Watermills
The earliest watermills are estimated to have appeared in the Middle East during the second century B.C., with a vertical axis design that used to grind grain. Later on, variety of design has appeared in many European countries especially during the Roman Empire. The most widely used design at that period was water wheel design. There were three different types of water wheel, undershot wheel design, which can be used in almost any stream or river, but such types become inefficient if the water down stream backup because of flooding, impending the motion of wheel.
Second design is the overshot wheel. The wheel run under the falling water on the blades from above avoiding the flooding problem, but the head of the water (entering water) must be as high as at least the diameter of the wheel; this limits the usage of such system on streams and rivers with gentle gradients. Also this design tends to be more massive than the weight of the water falling from above.
The breastshot is an advanced design, the head of the water is not necessarily high, it is enough to be at the wheel axis level even a little less. This design eliminates the flooding effects, in which the water is channeled between parallel breast walls and strikes the propellers to turn the wheel.
The Lebanese Watermills
The Lebanese watermills have a unique design. The watermills consist of three main parts, the lime stones, the turbine and the vertical tunnel. However, there are many other parts such as the control gears that control the water flow and others. The millstone consist of two lime stones, one fixed lays on the ground and the other runs over it to grind the grain. The second important part is the turbine, which is made mainly from wood. It is a vertical axis turbine that uses the waterfall to run. The vertical tunnel, in which the water falls to hit the propeller of the turbine, is built as high as can be in order to deliver a kinetic energy.
Objectives
The multifaceted project will have many objectives. The main objectives are technical, economical and environmental.
I-Technical objectives.
The technical objectives will focus on hydrology, location, sizing, design aspects, and feasibility of the watermills.
The technical concept of the watermill is composed of the following: running water is diverted though an open channel and the transported water falls into a vertical tunnel. Effect of gravity and the decreasing diameter of the tunnel provide high pressured water that turns a turbine which turns the limestone.
The density of a typical limestone ranges between 2.1 T/m3 and 2.4 T/m3. Typical diameter and height of the limestone is about 2 m and 0.4 m, respectively. Thus the estimated weight of the limestone will be approximately 2.64 Tones. Therefore, the energy generated from the watermill is large enough to turn approximately a 3-Tone limestone. Notice that the existing large friction is added to the overall weight of the limestone.
The ideal location of the watermills is on the river with a high gradient. In dry seasons, many streams and even small rivers dry out. Thus watermills were usually built on the perennial rivers, streams and springs. The Mini-Hydro Plants can use those watermills to generate electrcity all year-round. Even those which are built on seasonal streams, the Mini-Hydro Plant can operate for more than six months. If the electrical output of one Mini-Hydro Plant does not meet the electrical demand of a neighboring village, then cascaded watermills can be used. The size of a proposed Mini-Hydro Plant depends on many factors. The most important factors are: gradient of the river, quantity of water flow, and the shore area.
Tasks to be done are:
1-create a topographical map of the existing watermills by :
a-establishing the locations of watermills scattered in North Lebanon.
b-defining the physical characteristics of each watermill.
c-determining the usage and the recent activity of each watermill.
d-locating the nearby villages to each watermill.
2-Select a sample site with an exisisting watermill to:
a-study and analyse the physical characteristics.
b-design a balanced local power system where supply and demand are matched for the nearby village.
The technical study will include a plant design of the proposed watermill, herein many important factors will be taken into account as to the appropriate turbine, generator and other mechanical and electrical equipment to achieve highest efficiency.
II-Economical Objectives
The hydroelectricity plays a significant economical role in many countries as it delivers a free non-polluting energy. Due to many problems, Lebanon does not make use ot its hydro energy as it should be. The 8600 Mm3/year of precipitation does not serve the hydroelectric sector in more than 4% of the electricity production [2] [4].
Table 1 and Table 2 summarize the state of the Lebanese eclectric sector.
Table 1 – Thermal Electric in Lebanon in 1999 [2]
| Station |
Turbine Type |
Fuel Type |
Capacity (MW) |
Generated (GWh) |
| Zouk |
Steam |
Heavy Fuel Oil |
3 x 145
|
2926
|
| Zouk |
Gas |
Diesel Oil |
175
|
29
|
| Jyeh |
Gas |
Heavy Fuel Oil |
2 x 62 + 18
|
1686
|
| Hreyche |
Steam |
Diesel Oil |
3 x 69 + 65
|
335
|
| Baalbeck |
Steam |
Diesel Oil |
2 x 35
|
383
|
| Sour |
Gas |
Diesel Oil |
2 x 35
|
461
|
| Zahrani |
|