Micro Hydro Power (MHP) Plants

From energypedia

Basic Energy Services in a Nutshell: Context | Basics | Energy Systems


Classification of hydro power can be summarized as follows[1][2]:

Large Hydro
All installations with an installed capacity of more than 1000 kW (according to some definitions more than 10,000 kW)
Medium Hydro
Installations of 15 - 100 MW (usually feeding the grid)
Small Hydro
Installations of 1-15 MW (usually feeding into the grid)
Mini Hydro
Capacity between 100 - 500 kW (either as stand-alone schemes or more often feeding into the grid)
Micro Hydro
Installations with power output of 5 - 100 kW (usually provided power for small community or rural industry in remote areas away from the grid)
Pico Hydro
From a few hundred watts up to 5 kW

A micro hydro power (MHP)'plant' is a type of hydro electric power scheme that produces up to 100 KW of electricity using a flowing steam or a water flow. The electricity from such systems is used to power up isolated homes or communities and is sometimes connected to the public grid.[3]

Micro hydro systems are generally used in developing countries to provide electricity to isolated communities or rural villages where electricity grid is not available. Feeding back into the national grid when electricity production is in surplus is also evident in some cases. The micro hydro scheme design can be approached as per household basis or at the village level often involving local materials and labor.[4]

In 1995, the micro-hydro capacity in the world was estimated at 28 GW, supplying about 115 TWh of electricity. About 60% of this capacity was in the developed world, with 40% in developing areas.[5]

Micro hydro plants that are found in the developing world are mostly in mountainous regions for instance in the some places in the Himalayas as well as in Nepal where there are around 2,000 schemes, including both mechanical and electrical power generation. In South America, there are micro-hydro programs in the countries along the Andes, such as Peru and Bolivia. Smaller programs have also been set up in the hilly areas of Sri Lanka, Philippines and some parts of China.[6]

Benefits and Shortcomings of Micro Hydro Power Plants

Small scale hydro power stations like micro hydro schemes combine the advantages of hydropower with those of decentralized power generation, without the disadvantages of large scale installations.

Some of the advantages can be identified as:[7]

  • Efficient energy source: It takes only a small amount of flow to make it work (as small as two gallons of water or a drop of as low as two feet) to generate electricity with the micro hydro, the produced electricity can be used as far as a mile away from the production site.
  • Reliable electricity source: There is a constant and continuous electrical energy supply from a hydro power plant compared to other small scale renewable energy technologies. There are however peak energy seasons (mainly during winter) when large quantities of electricity is required.
  • No reservoir required: Micro hydro are considered to run as a 'run-of-river' system , this means that when the water passes through the turbines it is diverted back to the river/ stream with relatively low impact on the surrounding ecology.
  • Cost effective energy solution: A small hydro- power system can cost in the range of $1,000-$20,000 depending on the site electricity requirements and location. The operation and maintenance costs are relatively low as well compared to other technologies.
  • Power for developing countries: Having low-cost versatility and long life span, micro hydro can be used by developing countries in supplying electricity to small villages and communities.
  • Integrate with the local power grid: If there is a surplus production of electricity, some companies can buy the electricity from you and integrate it to the grid. There could also be a possibility of supplementing your level of micro power with intake from the grid.
  • Environmental impact: The impact on the environment is minimized as compared to the traditional power stations that use fossil fuels.

Disadvantages / Shortcomings:[7]

  • Suitable site characteristics required:
  • Energy expansion not possible:
  • Low-power in the summer months: Since streams will reduce their flow rates depending on the season, summer months are likely to have less flow leading to less power output. However advanced planning and research can ensure adequate energy requirements are met.
  • Environmental impact: There is a low ecological impact from small-scale hydro systems, however the low-level environmental effects must be taken into consideration before construction begins. Stream water will be diverted away from a portion of the stream, and proper caution must be exercised to ensure there will be no damaging impact on the local ecology or civil infrastructure.

Application: Use of Micro Hydro Power Plants

Power produced from a small hydro station can be used for various purposes, some of the uses have been classified as follows:

  1. Productive Use: This is where the electricity generated is used to perform activities where money is exchanged for a service. Most of this scenarios take place in small businesses.
  2. Consumptive Use: All the other used that the electricity can be used for are called consumptive use. they include using the electricity at the household or close to the household.

Besides the productive and consumptive use, a distinction can also be made between the use of power in a mechanical way or in the form of electricity:[8]

productive use
  • agro processing
  • timber sawing
  • textile fabrication
  • cooling
  • drying
  • mechanical uses with electricity as intermediate
  • heating
  • lighting
  • fertiliser production
consumptive use

  • domestic lighting
  • cooking
  • cooling
  • radio and television

As the above illustration shows power that is generated by MPH is a convenient source of electricity to fuel anything from workshop machines to domestic lighting as the power can also be supplied to villages via portable rechargeable batteries and thus there are no expensive connection costs. Batteries can as well be charged and used to provide the local community with power. For industrial use however, the turbine shaft can be used directly as mechanical power as opposed to converting it into electricity via generator or batteries. This is suitable for agro-processing activities such as milling, oil extraction and carpentry.[9]


Scheme Components

Most micro-hydro systems are ‘run-of-river’ which means that they don’t need large dams to store water. However, they do need some water-management systems.[5]

Components Micro Hydro Power Plant

► More information and picture in the Micro hydro power scout guide.

The illustration above shows just how a micro-hydro system can be setup. For water diversion the river water level has to be raised by a barrier, the weir [1]. The water is diverted at the intake [2] and conveyed by the channel [3] along the landscape´s contour lines. The spillways [4] protect against damage from excessive water flow. Water is slowed down and collected in the fore bay [5], from where it enters into the penstock [7]; the pressure pipe conveys the water to the power house [6] where the power conversion turbine, mill or generating equipment is installed. The turbine is the core of a MHP, which is rotated by the moving water. Different types of turbines are used depending on the head and the flow of the site, the turbines are used to rotate a shaft which is then used to drive the generator.[5] The water is then discharged via the draft tube [8] or a tail race channel in case of cross flow or Pelton turbines.[10]

Due to the nature of the micro-hydro schemed to be remote; a local grid is constructed to distribute the electricity to the different users. The demand output must match the capacity of the generator otherwise the voltage and frequency can vary suddenly, which can result in the damage of certain electrical equipment. The power demand in an off-grid is often variable since people switch lights and machines on and off, so the supply from the micro-hydro system must be varied to keep close control. This can be done by varying the water flow, or by using an electronic load controller.[5]

► find more information here: Hydro Power Basics - Micro Hydro Power Schemes

Turbine Types

► find more information here: Micro Hydro Power (MHP) Plant - Turbine Types

Suitable Conditions for Micro Hydro Power Plants

The ideal geographical areas for exploiting small scale hydro schemes is where there are steep rivers flowing all year round. Islands with moist marine climates are also suitable. Low-head turbines have been developed for small-scale exploitation of rivers or irrigation canals where there is a small head but sufficient flow to provide adequate power.

To understand more about a suitable potential site, the hydrology of the site needs to be known and a site survey carried out so as to determine the actual flow and head data. Hydrological information is easily accessible from the metrological or irrigation department of the particular national government. Site surveys usually give a more detailed information of the site conditions to allow power calculation to be done and design work to begin. Flow data should however be collected over a period of one year where possible, this is to ascertain on the fluctuation in the river flow over the various seasons.[2]


The cost of investing in a MHP varies depending on the location and thus it is impossible to give accurate figures without knowing the specifics of the site.

  • An estimation from GIZ indicates that in 2010 the installation cost ranged from from USD 1,000 to more than USD 10,000 per kW.[11]
  • On the other hand Practical action cites from their experience, that the cost varies from approximately £1,200 to £4,000 (USD 1831.32 - USD 6104.40[12]) per installed kW, when using appropriate technologies, which are much cheaper than using conventional approaches and technologies.[13]

Costs depend on the site conditions, availability and quality of equipment and construction and the mode of operation (off-grid or grid-connected). Local contributions can reduce these costs significantly.


MHP schemes require a high investment cost that are mostly acquired through public or donor funding. There is however a need to increase private sector involvement due to the high demand of public funds and the need to attain a long-term sustainability. Public and especially donor-based funding of entire MHP schemes should be complemented by creating conditions which make MHP projects attractive to private investors, including financial incentives and smart subsidies, and through this, the public funds can develop a leverage effect for private investment. However development of MHP depends on a certain degree of public support. With the current experience with off-grid MHP systems show that it is very difficult to develop schemes with less than at least 50% public funding.[14]

There can various options for funding that can be used to bring down the cost of MHS, they include[14]:

  • Public Funding which should be used in the support of primary investment in non local components of mini-grids and infrastructure, while costs for local material, labor and all operation and maintenance costs should be covered by a local business model.
  • Imposing a levy on on-grid electrification prices for large consumers can as well be a form of increasing the availability of government funds since extra funds that are collected can be used for rural electrification.
  • Bringing down costs is another option of making MHP projects more attractive for private investors. One good practice could be to set up the MHP model with an integrated ownership model, this means that a private investor is responsible for the upfront-capital, the set up and the technical Operation and Maintenance of the MHP plant; the community is, however, involved in collecting payments, dealing with payment delay, theft and in organizing community contributions. A community committee responsible for tariff setting can also help to ensure that a tariff system is set up which allows for enough income to cover costs, maintenance and repairs, to offer reliable revenues for the private investor and to ensure that tariffs are still within the local range of willingness and ability to pay. If MHP systems are grid-connected, a reliable and attractive feed-in-tariff is the best option to ensure the long-term financial viability of a MHP system.

Micro Hydro Power Plant Development - Barriers

There are various barriers that hinder the dissemination of MHP, some of them have been identified as[14]:

  • Policy and regulatory framework: In most cases there exists no sufficient policies and frameworks that govern MHP schemes, this is because the MHP is either not regulated at all or is combined with a broader framework made for rural electrification which may be unclear and in transparent. Such challenges causes the MHP project developers not to know which requirements apply and work in an unreliable grey area of regulation.
  • Financing: Lack of sufficient funding to be used in development is a common challenge as most MHP rely on donor funding which in most cases is only available in funding a small portion of the hydro power potential. One of the ways that such an case can be addressed is if there can be an option of exploring other sources of funding especially from private venture capitalists and local banks.
  • Capacity to plan, build and operate MHP plants: Lack of knowledge and awareness on MHP potential posses a great challenge for rural electrification, hydro power schemes still dominate as political decision makers still tend to go for them as a more "modern" approach. Combined with that there is minimal capacity to design, implement and revise the MHP supportive policies and regulations. And at the technical level, local capacity is often missing to plan, build and run MHP projects. The is also a problem in the lack of a ready supply of affordable turbine parts and the lack of domestic manufacturing capacity for hydro systems of all sizes also poses a barrier to a swift and cost-effective MHP project development.
  • Data on hydro resources: There is usually a lack of interest in MHP deployment from the politicians and power utilities companied by the lack appropriate capacities and budgets, as well as unavailability of pubic data on MHP sites. Such a lack of sound basic data (e.g. on mid-to long-term hydrological, geographic, geologic data and figures on the current and future demand for electricity and social infrastructure, but especially on effects of seasonal and long-term river flow variations), poses a major barrier for private investors in MHP. This causes a bottleneck for investment in hydropower systems as there is an increase in climate variability accompanied with the destruction of rainfall catchment areas.

Promoting Micro Hydro Plants

There can be various policy options for the promotion of MHP as shown below[14]:

Generation based (kWh)



Feed-in tarrifs

Fiscal measures

Bidding systems

Quota obligations

Green certificates

Fiscal measures





Fiscal measures

Quota obligations

Capacity based (kW)

Most incentives are given on the supply side, based on the installed capacity of the scheme. On the other side, beside direct subsidies for the installation on the plant, some countries have fiscal measures that can facilitate for the purchase and import of certain equipment. Guarantees are however applied where a donor funded project promotes the financing of MHP through local banks. With this the most prominent generation based instrument to promote the use of renewable energies are feed-in tariffs.

The demand side however, quota obligations force utilities and/or the demand side to deploy a certain percentage of renewable energy technologies.

Further Information