Overview 

• Small Hydro Systems play major role in meeting power requirements of remote, isolated  hilly   areas in a decentralized manner by tapping water streams, rivulets and canals of small  discharge. Small hydroelectric system captures the energy in flowing water and converts it   to   electricity.

• Of all the non-conventional renewable energy sources, small hydro stands first as it is more resourceful, reduces system losses, environment friendly, non-consumptive and sources are renewable.

• Small Hydro projects are, environmentally benign, have relatively short gestation periods and require small investments as compared to large hydro projects.

• Small Hydro provides a solution to rural electrification, poverty alleviation

• Small hydro has proven technology, low risk for investment.

• Small hydro does not involve setting up of large dams or problems of deforestation, 

• submergence or rehabilitation.

Selection of Hydro Schemes

 1. To have the optimum energy requirement, the hydro electric projects are to be selected  based on:

• HEAD or fall of water level as it flows
• Discharge or rate of flow

• Duration of flow or total quantity of flow 
  Formula to calculate Power output based on discharge and  head

2. The schemes are to be chosen based on the source of water flow. There are two types of schemes   available. They are:  

• Canal based schemes that utilize the drops on the existing / proposed irrigation canals. Click here to see a typical layout of canal based scheme.
• River / Stream based schemes – utilizing the drop in river bed

3. With in the river-based schemes, there are two sources for extracting hydro  energy. They are:  

• Run of the river – generates energy as the water flows
• Storage schemes- Stores water by forming a reservoir and utilizes water as and when  required.

4. Based on its relation with electrical supply grid, the hydro projects are classified    into two types. They are:  

• Stand alone off – grid schemes supplying power to its own demand through its own  grid.

• Grid connected – supplying power to an existing electrical grid along with other power stations.

Technology

The electro mechanical equipment that converts the potential energy of water into electrical energy is housed in powerhouse.  The main component is water turbine.  The type of water turbine to be used depends on the range of operating heads as well as  the energy requirement.

For low heads up to 15 to 25 m, special axial flow turbines of tubular type have been developed which are more economical.

More recently, bulb type turbines, in which generator is placed in a bulb shaped water tight steel housing located in the center of water passage, are developed for low head. 

The actual selection of the type of turbine is influenced by the considerations of size and  efficiency in the prevailing range.

While the power house building and the electro mechanical equipment housed in it  are   the central part of a hydro electric scheme, the other major components may  broadly be called as water conducting / controlling system.

The water conductor system comprices pondage arrangements including surplus arrangements, diversion arrangements to divert the water from its normal course into the power house, a fore bay reservoir to cater to variations in load, an intake structure for controlling the flow of water, surge tanks, steel penstocks / penstock tunnels, draft tube structure, tail race pool & channel to lead the water back into the normal course and various gates, hoists with controls.  The water conductor system should be such that it conveys water with minimum loss of head and in a reliable and safe manner under all conditions while being economical for execution.