The calculated efficiency is 21% which is far below the optimum range 60-75%. The much lower efficiency depicts serious shortcomings in the installed plant.
Careful calculations and analysis portray limitations in the following areas.
5.1 HEAD RACE CANAL
Losses in headrace canal are due to two reasons:
The HRC is an open earth channel (natural watercourse) so flow is turbulent in the HRC which is due to level difference in the channel and zigzag path.
Excessive leakage from the Natural watercourse and reason is the same. The approximate flow loss in the headrace canal due to leakage is 0.0338m3/sec.
The flow loss is calculated by measuring flow parameters near the weir and FBT.
The turbulence and leakage in HRC could be avoided if
Efforts are made to align the natural water course straight with little bent-over.
Natural water course HRC is replaced with rectangular concrete channels with spill ways in between and near FBT.
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5.2 WEIR
Weir is not properly designed and built since stones, wood logs and sands are raw materials used. A medium level flow in rainy days could ruin the weir and it is routine for the locals to built it again and again when flow in the stream increases.
To ensure stable flow even in rainy days, the weir must be made with concrete, having steel fixers.
5.3 FOREBAY TANK
The purpose of FBT is to make flow laminar and to provide trash rack and screens so that small pebbles and rocks couldn‟t get into penstock. The recent design is illogical since the FBT is built almost 2.23m below the headrace canal without leveling the upper part of FBT with HRC. The FBT never fills fully with water. And hence almost 2.35m head loss occurs due to this.
The FBT would be purposeful if:
The upper level of the tank is aligned and leveled with HRC so that no head loss occurs.
The penstock pipe which leads from the FBT to the turbine, must little bit above the floor in order to get laminar flow. Another advantage of this position is that the unwanted materials, pebbles, rocks etc would settle down in the bottom, hence safe flow is ensured.
5.4 PENSTOCK
It is the part which counts for almost 30% of the overall cost of the turbine.
The sizing is awesome i.e. having 30 inches diameter but little bit leakage is there from penstock which requires minimal maintenance.
5.5 TURBINE
Old version of cross flow turbine is installed. Major shortcomings are;
Excessive leakage due to large clearance volume between casing and rotor blades.
Rough outer and interior periphery. Blades are not smoothly fabricated and also the absence of well design trash rack and screens added more to this misery.
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Excessive leakage from the nozzle Absence of Draft tube
Difficulty in maintenance and cleaning due to complex assembly.
The old version of CFT must be replaced with the latest design cross flow turbine having minimal clearance volume, sealing and fine blades. In the international market, comparatively low cost and easily available choice would be T15 turbine made by ENTEC. This firm has given license to manufacturers in Pakistan. Salient features of the turbine are:
Welded Housing ,made of quality steel, rigid enough to withstand high operational stress
Casing is designed in such a way to give flexibility regarding main bearings of the runner, to cope with requirement like flywheel, built drive etc.
A sealing system( contact free or conventional type) is integrated in the slide flanges. Guide vane unit could be easily taken out through slide flange for cleaning maintenance.
Figure 5.1 T15 CFT
High precision fabrication of runner cylinder, laser cut slide disks and exceptionally fine blading drawn from bright steel.
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Due to these salient features the organization claims efficiency of the turbine after testing as:
Figure 5.2 T15 Efficiency after testing The T15 turbine is available in Gujranwala, Lahore and Mardan.
5.6 ABSENCE OF AUTOMATIC CONTROL
Flow to the turbine is controlled via traditional manual valve i.e. If load exceeds then the operator increases the flow and vice versa. The operator increases or decreases flow via control valve observing voltmeter attached to the turbine but it is very difficult to examine the flow 24\7. And the most reoccurring cost which the local community is tired-of to pay, is the cost of blasted tube lights, which they almost change once in two months approximately. The locals feel that they face two problems:
Firstly when peak load exceeds then there is no mechanism to adjust that.
Secondly they are unable to control the instantaneous high voltage when there is low load condition. Sudden rise and fall in voltage beyond optimum value, cost heavily on poor people.
To cope with the problem, one should either install mechanical governor or ELC (Electronic load controller). Practical experience depicts that mechanical governor in MHPPPs often fails. So a viable alternative is ELC.
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An ELC is a solid-state electronic device designed to regulate output power of a micro-hydropower system. Maintaining a near-constant load on the turbine generates stable voltage and frequency. ELCs can also be used as a load-management system by assigning a predetermined prioritized secondary load, such as water heating, space heating or other loads. In this way, one can use the available power rather than dumping it into the ballast load. Without an ELC, the frequency will vary as the load changes and, under no-load conditions, will be much higher than rated frequency. ELCs react so fast to load changes that speed changes are not even noticeable unless a very large load is applied. The major benefit of ELCs is that they have no moving parts, are reliable and are virtually maintenance-free. The advent of ELCs has allowed the introduction of simple and efficient multi-jet turbines for micro-hydropower systems that are no longer burdened by expensive hydraulic governors.
Figure 5.3 Electronic Load Controller
There are various types of ELCs in the market that can regulate systems from as small as 1 kW to 100 kW. The choice of the controller depends on the type of generator you have. ELCs are suitable for synchronous generators. If there is an induction generator, it will need an induction generator controller (IGC). IGCs work on a principle that is similar to that used by ELCs, but an IGC monitors the generated voltage and diverts the surplus power to the ballast load.
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5.7 LINE LOSSES
The line losses are due to the use of substandard cables and non-availability of poles. Since the site is in mountainous territory, the cable is now and often passing through large bulky trees. It is routine in raining that locals shut downs the plant since the wooden pole or those wires which are passing through trees become short-circuited. Poles with insulators for holding live wires are needed besides quality cable for transmission
5.8 COST ESTIMATE
The power plant was installed in 2002 by the local community. The initial cost (in rupees) of Electro-mechanical components and civil structures are as under:
Table 5.1 Initial cost estimate
On the basis of recommendations, two cost-plans are forecasted which are:
a. Plan-1 for NGOS and Govt. Organizations b. Plan-2 for Local community
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