 Hydro-based mini-grid systems most often use mini-hydro or micro-hydro power plants. There are no universally accepted definitions of small, and mini, micro or pico hydropower. However, the commonly accepted thresholds are shown in the table below. Mini- and micro-hydro plants are often the run-of-river type and generally do not involve a dam with impoundment of water. Therefore, they often avoid the kinds of detrimental environmental and social impacts that can be problems for larger hydropower systems.
Commonly Accepted Thresholds For Hydropower Systems | Pico-hydropower | < 5 kW | Micro-hydropower | 5 kW - 100 kW | Mini-hydropower | 100 kW – 1 MW | Small hydropower | 1 MW - 10 MW (- 30 MW) | Medium and large hydropower | > 10 MW (> 30 MW) |
 Technical Summary
Resource Assessment Cost, Performance and Project Risks Technical Specifications
Technical Summary A mini-grid village hydro system is an isolated water-driven power supply intended to provide a village with energy for various applications such as: - Electricity for lighting and appliances (radio, TV, computer, etc), in homes and public buildings such as schools and clinics,
- Electrical or mechanical power for local service and cottage industries,
- Electrical or mechanical power for agricultural value-adding industries and labor saving activities, and
- Electricity for lighting and general uses in public spaces and for collective events.
Village hydro systems are comprised of three elements: - Civil works: these consist of diversion works, channels and piping to convey river, stream or spring water to the power generation equipment, the power house building and water exit channel
- Power generation equipment: this consists of a turbine, a drive system linking the turbine to a generator and/or mechanical devices, a generator, a generator controller and switchgear
- Power distribution system: this involves distribution of electrical power by one or more main distribution lines to central points, then by sub-distribution lines and consumer service connections to consumption points. Very small village systems may contain a battery charging system to provide energy storage, voltage stability and services to remote customers.
Resource Assessment Information on mini-hydro resources must generally be obtained through locally sources, such as forest and water resource agencies. Several years worth of hydrological data are needed to ensure that long-term financial calculations are based on the average hydrological year. Very often, mini-hydro resources are seasonal and highly dependent on rainfall in the local watershed, and the system performance can vary significantly from one year to the next. Therefore, the accuracy of the financial assessment will depend on the quality of the hydrological data available. An international database of small hydropower resources is developed and maintained by the Small Hydropower Annex of the IEA’s Implementing Agreement for Hydropower Technologies and Programs. The objective of the database is to facilitate the development of new small hydro projects of more than 50 kW and less than 10MW installed capacity. The web site provides data for potential and developed sites, GIS searching capabilities, country profiles, international contacts for small hydro, and a world resource atlas.
Cost, Performance and Project Risks The costs of mini-hydro power systems vary considerably as the result of many site-specific design and performance related factors. One survey found the average capital cost (in constant US$1998) of the sample investigated is $965 per kW for plants used for mechanical power and $3,085 per kW for plants generating electricity, including the costs of transmission, which clearly vary. Mini- and micro-hydro systems are most likely to be financially sustainable if they have a high load factor, a financially sustainable end-use, and costs are contained by good design and management. The greatest project risks are not technical, but business-related. Management of the installation, including the setting and collection of tariffs that keep pace with inflation is critical for project sustainability.
Feasibility Study Tools Guidelines and design aids for the assessment of micro-hydro projects have been developed by the Alternative Energy Promotion Center of Nepal under the Energy Sector Assistance Programme supported by DANIDA. The guidelines and aids provide a basis and tools for performing detailed feasibility studies, including technical design, for micro-hydro projects between 3 kW and 100 kW.
Technical Specifications A set of Village Hydro Project Specifications were developed under the Bank’s Sri Lanka Energy Services Delivery (ESD) Project. The specifications consist of the following seven sections: (Each item below is a link to a document in the document library.) 1. Introduction 2. General Requirements 3. Civil Works 4. Mechanical Components 5. Electrical Components 6. Battery Distribution 7. Line Distribution The specifications were intended to provide a fast and practical system for checking and promoting the viability of schemes being considered for credit assistance. They are not intended to provide comprehensive guidance to design calculations, or to operation, maintenance, management, and fault finding procedures. The specifications should therefore be used in conjunction with other documents.
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