Applicability of (new) technological approaches / case studies on mini hydro

TJARINTO S. TJAROKO

ASEAN Centre for Energy
Jl. H. R. Rasuna Said, Blok X-2, kav. 07-08, Kuningan, Jakarta 12950 Indonesia
Tel. + 62 21 527 9332, fax. + 62 21 527 9350, e-mail:

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1. INTRODUCTION

Currently, one of the major and most widely utilized sources of renewable energy is hydro power. As a renewable energy, it is extremely site specific, economically feasible, technically matured, and the technology being used was proven from large to small scale. In Europe, more than 90 % of the existing potential for hydropower is already being harnessed. However, worldwide only about 10 % and in the ASEAN (Association of South-East Asian Nations) regions is only less than 5% of the potential for hydropower is being utilized at this stage.

In the developing countries, it is widely recognized that SHP (Small Hydro Power) may play a significant role in the power sector development with applying of specific technology which technically and economically feasible and socially acceptable. The technology applied is not merely for electric power generation but also for direct mechanical power utilization particularly for agriculture product processing and water pumping.

The central supplying of electricity through the grid extension is still very expensive and not economically feasible for the remote or rural villages of most developing countries. Mini and Micro Hydro Power (MHP) can offers realistically solutions presenting many advantages over commonly used small and independent diesel generators, due to the fact that MHP will provide advantages as follows:

• MHP plants have proven operated for many years ago without difficulties, as compared to the diesel generator which is time-consuming for operators, and very costly for operation and maintenance;
• No fuels requirement for MHP, meanwhile problems always arise with delivery of  fuel for the diesel generator in term of cost and transportation;
• No CO2 emission for MHP, while diesel generators is always produce pollutants;
• No contamination of drinking water supplies in the MHP scheme; and
• Other environment impact from MHP plant is neglect able compared to the diesel generator.

The introduction of MHP technology in many developing countries is still in the beginning stages. However, if there is an existing hydro potential, the utilization of hydropower scheme to generate electricity is the most appropriate alternative in the long- term consideration. The transfer of technology and know-how on the MHP development and operation from EU to the most of ASEAN member countries have been conducted over 20 years ago. Dissemination strategies and advisory assistance in the implementation based on the bilateral and expansion to a regional cooperation of the MHP programmes was provided with quality assurance for systems design, manufacturing, construction, operation and maintenance through the basic and advanced training for local personnel for some ASEAN member countries. EU experiences and know-how provides the necessary foundation for long-term investment and programme design decision.

The tremendous reserves of hydropower in many developing countries have paved the way for attracting the local investors for construction of numerous MHP plants, the electric power produced either consume by local inhabitants or selling to the utility grids have been developed few years ago with success stories. This is because of the tremendous push for the expansion of large hydro power projects which has been underway for the past 25 years, but it�s just recently beginning to stagnant due to the fact that relatively high cost of investment, ecological long term effects, and social problems such as the population resettlement affected by the project.

2. MHP SCHEME TECHNOLOGY

The utilization of MHP which is usually as tailored made systems with a capacity of less than 5 MW has proven to be easily put into action.
The typical areas of application are:

• Supplying power to the national grid connection system with certain pricing arrangement;
• For remote and isolated rural electrification. However, the well design isolated systems can be connected to the emerging regional power supply grid systems in future;
• Supplying individual consumers for productive end uses which are require electrical or mechanical power (i.e. saw mills, pumps, and rural industry activities).

The following guides lines are needed to develop MHP schemes:

• MHP plant needs special and unique designed, individual measures with consideration to a multi-disciplines of experiences;
• Basic experiences and successfully proven planning methods in many locations determine the degree to which an objective can be realized quickly;
• MHP development is labor intensive construction with very low of foreign currency involvement, these will impact to the total cost of investment and in addition creates local employment;
• The utilization of locally existing building materials should be prioritized which will minimize construction cost;
• The application of robust and technologically proven turbines and generators will avoid the problematic and smooth operation of hydropower plants for long time;
• Basic and advanced training measures offered to the concerned personnel at site in the respective country will secure a very reliable operation of local MHP plants;
• The impact on nature degradation can be minimized by employing certain flexibility during the planning and construction stages. In this manner, ecological and economic interests will be kept on a common denominator;
• The construction of MHP plants without the use of much heavy equipments will eliminate the need for the construction access passage ways, and therefore reducing the construction cost and benefits for the environment;
• Full participation of the local population is raising social and economic awareness within the surroundings of the power plants;

Mini hydro power plant technologies have been matured and proven, therefore individually custom-designed for a specific location is needed. Depending on the rural conditions, topographical location, the existing water potential, and various determinants such as socially acceptability, land owners, water rights etc., will be put into consideration. All of them shall produce the following design characteristics:

• High efficiency of turbine, generator and other supporting equipments;
• Long life expectancy of the plant;
• Simple and robust technology applied;
• Minor requirements in term of maintenance and operation;
• Low cost of operation;
• Multi-purpose utilization of the plant such as for irrigation, flood prevention, drinking water supply, fish farming and tourist destination;
• Minimizing the ecological impacts.

3. GENERAL TREND IN MHP DESIGN

The basic consideration in developing MHP plant is the environmental and safety issues than followed by the electricity demand and availability of energy sources in term of head and flow rate of water falls. Other non-technical parameters are also considered at early stages such as social acceptance, water right, ownership, management, operation and maintenance issues. The head (height of water falls) means the vertical distance between upper and lower level of water that will be flown to the turbine through the penstock pipe.

MHP plants usually are located closed to the load centre and the existing dams or weir, therefore dams and weir should be designed properly to meet modern safety requirement. Remote control and monitoring of the structure and water flows be possible to carry out automatically. However, such facilities design may require relatively high investments.

In the building of structure design, availability of local materials and methods for construction should be considered, concrete is still unbeatable as the main materials for the most common SHP structures. Some building parts may be made by pre-fabrication in order to minimize the cost and construction time. However, as the MHP plant is always unique implying that the design and usage of building materials have to be specifically adapted to the location.

Many types of turbines have been implemented in the MHP schemes such as Kaplan, Francis, Propeller, Pelton, Cross flow, etc. The application of each turbines has own characteristic depending on the input of head and water flow rate. In the initial stage, a number of low head propeller type turbines were manufactured and implemented mainly for direct power drives. Further an assessment of the performance of these machines after some years, led to the conclusion that a more versatile turbine was needed in term of output capacity and applicability of the head range, and the electro-mechanical parts must be compact and robust due to the fact that many location of MHP schemes are located in very remote areas with minimum access of infrastructure. Consequently, a cross flow turbine was fast developed due to the flexibility, easy to manufacture and low cost investment with considerable adaptability to different situation and condition of the sites. This turbine met a growing interest to many workshops in manufacturing this type of turbine, and simultaneously many developing countries began to concentrate on the cross flow turbine for their MHP schemes development. This is because the applicability of the cross flow turbine is fulfilled the following criteria:

• The turbine design is very simple, avoiding foundry technology and only using welding construction;
• The runner blades do not requires any three dimensional shaping but can be produced from a slice of pipe section;
• The turbine set is very light, detachable into many components and easy to re-assemble again, this is allowing to transport by manpower to remote areas;
• Adaptable to various location with different head and flow rate by varying the length of runner;
• Easy to incorporate a flow regulating devices to adjust the output to the consumer load;
• Possible to produce and repair locally.

Gear boxes are not commonly used by MHP designer because of noisy and short life time. However, for many MHP projects with relatively low head, an increase of the turbine speed is often necessary in order to use available standard generators. The standard generators/motors are used in other industrial activities therefore it�s manufactured in large series meaning lower prices in the common markets. Gear boxes are also manufactured for other specific purposes and can be obtained at reasonable prices. Introduction of a gear box will result in an efficiency loss in the order of 1 to 1.5 percent. However, many MHP plants less than 500 kW capacity are using pulleys and belt transmission to transfer the power from turbine to the generator.

According to the topographical conditions, sometimes the headrace waterway will be designed as a penstock. Penstock is manufactured from various materials such as steel, wood, concrete and plastic materials (i.e. Poly Vinyl Chloride / PVC). The most penstock used usually made from rolled steel sheet welded longitudinally shape as a pipe. But glass fiber reinforced plastic penstocks is also available which is very strong like steel materials, very light and inexpensive. As a common practice the penstock is usually embedded in the soil whenever possible due to the environmental considerations.

Gates structures for dams, intakes, etc. have not undertaken any major technical changes in recent years. Conventional rock filled dam is still popular in MHP design. However, the various types of rubber gates have been introduced but very little impact on the market. Intake trash racks usually made form steel but composite materials have also been introduced. 

Asynchronous generators are normally being used in the MHP scheme up to 2 MW installed capacity which is supplying energy to the isolated and independent power grid system. The induction motor can be used also as generator (IMAG) for the isolated grids in the MHP scheme. The synchronous generators are used widely in the larger capacity of MHP. This generator is robust, simple to control and almost maintenance free in a brushless (rotating rectifier) version. It generates electrical power with a frequency proportional to the speed of the rotor, so the electrical frequency and mechanical speed are synchronous.

4. FINANCING OF MHP

For long term operation, MHP provides lower cost of production for electricity to a level at which there will be no more competition. However, the initial high investment cost during the development of a suitable MHP plant (usually within the order of US$ 1,000 � 3,000 / kW installed capacity) required a provision capital. Therefore, the financing arrangement requires an appropriate level of discretion between the developers and the creditors. This can be ensured through:

• State own development banks;
• Utility corporations;
• Cooperative banks;
• Regional development funds;
• Locally private banks;
• Private company funds; and
• Personal funds.

An interesting experience is given by the fact that utility companies or local electricity cooperatives is more interested in developing MHP plants compared to private investors. They tights on the financing scheme agreement with the funding source to certain conditions as follows:

• A binding commitment to tariffs on electricity for the period that both parties had reached a common consensus (i.e. 10 to 20 years);
• Guaranteed consumption from the customers either firm or non-firm capacity;
• The authorization for the transmission and distribution of energy from the regulatory body; and
• Other commercial aspects related to the supply and demand of electricity.

Activities which should be conducted from the planning to the implementation stage include:

• Market studies and analysis of target groups and their electricity demand for national and regional from the MHP plants;
• Economic feasibility analysis and field performance assessments for MHP systems;
• Prepare financing arrangements and perhaps need to looking assistance for the design of credit schemes;
• Provision of basic and advanced training to local management personnel and technicians;
• Looking for possibility in local manufacturing of turbines;
• Marketing consultancy services for MHP systems;
• Providing consultation and assistance for consumers;
• Providing support for the establishment of cooperation agreement (know-how and technology transfer); and
• Environmental impact (feasibility) analysis for the definite sites.

Some pilot projects and demonstration measures in the field of MHP are as follows:

• The utilization of MHP plants to feed into an existing grid owned by the public power supply system company;
• The utilization of MHP plants to supply remote areas that do not have any access to public power grid supply systems;
• The utilization of MHP plants for the individual supply of small trade shops, factory, workshops, and other small crafting businesses in specific areas;
• The rehabilitation and modernization of the existing MHP scheme;
• The utilization of MHP plants in connection with existing irrigation channels;
• The utilization of MHP in order to charge up batteries for consumers who are not connected to a public power supply system.

5. MHP PROJECT CONCEPT AND STRATEGY

The MHP sector in most ASEAN countries are currently at low stage of development because of a perceived predominance of hindering forces and risks. Through an intervention on various levels, these barriers can be overcome and the MHP sector can achieve a higher level of development.
The figure below shows the sequence of the required development assistance in three phases:

• Assessment Phase, the frame conditions are assessed and the barriers identified. Based on these, a strategy on how to initiate the take-off of the MHP sector is formulated.
• Pilot Phase, the validity of the selected strategy is verified on the basis of an implemented MHP projects. In most ASEAN member countries, the locally turbine manufactured up to the end of this stage even some types of turbine have been in the dissemination phase.
• Demonstration and Dissemination Phase, the approach is replicated in other regions. In ASEAN, the imported MHP systems mainly from the developed countries have been disseminated for commercial application since many years ago.

With the establishment of regulatory frameworks on the New and Renewable Energy in most ASEAN member countries, the MHP schemes particularly the locally made will be disseminated through market driven in near future.

Recommendation for the implementation of MHP schemes:

• For MHP pilot project should aim at finding technical solutions only. Giving top priority to economic viability at an early stage is too ambitious. It is already great achievement if the income of a plant is enable to cover operation and maintenance costs;
• Any activity not in relation with a motivated local partner will be useless and have no longer impact;
• "Learning by doing" has proven to be a useful approach;
• It is better to begin with simple projects such as mechanical applications for direct drive of agro-processing machineries, because these are not only less complex compared with electrification projects, but in general this also more economical for the user;
• Do not expect that a plant is completed the day it goes into operation. Monitoring of plant performance is essential;
• In most cases water flow data at a proposed site do not exist. Therefore to assess the flood risk and properly sizing of the plant are needed;
• Define the MHP development programme aims at long-term activities for a certain interesting country;
• In the market driven phase, the private entities are encouraged to develop MHP which generate electricity and selling to the utility grid if the regulatory framework for this purpose has been in place;
• Consider any government policy on Renewable Energy Implementation particularly for MHP schemes;
• Building up local skills in surveying, planning, manufacturing, installing, operating and maintaining of MHP scheme; and
• Create institutional set-ups either national or local level allowing the gradual reduction of foreign technical assistance input.