Table of Contents

1		Is it for me?
2		Introduction
3		How much does it cost?
4		What are the benefits?
5		Step by step guide
6		Legal considerations and financial tools
7		Case studies
8		References

Introduction

Hydropower, or hydroelectricity, is the generation of electricity from water driven turbines. It is an application of a much older technologies that has been used for centuries to convert the energy in flowing water, or hydro-energy, into more useful forms of energy, for example using a water mill for milling grain. Hydropower relies on a river that has a regular and adequate flow rate, and a sufficient downward gradient (ie height difference, or head).

Hydropower is certainly the largest and most mature application of renewable energy. 22% of the world's electricity production comes from hydropower installations, many of which are small hydropower (SHP) plants of less than 10 MW, and there are more than 17,400 SHP plants installed in Europe.

Hydropower is a mature technology that has evolved for more than 100 years. The technology has been adapted to all sizes of applications, and is generally referred to according to the scale of a power plant, as follows:

Pico-HydroPower plants: up to 5kW

Micro- and Mini-HydroPower plants:5kW to 100kW

Small HydroPower (SHP) plants:100kW to 10MW

The definition of SHP varies from country to country (from 1.5 to 25 MW), but 10 MW is becoming the generally accepted limit for SHP and has been adopted by ESHA, the European Small Hydropower Association.

Large Hydro Power plants greater than 10MW. These are the more familiar dams that are major civil engineering infrastructure projects.

 More about the key properties of hydropower

 More about hydro potential

Scheme components

The Figure shows the main components of a run-of-the-river micro-hydro scheme. This type of scheme requires no water storage. Instead some of the water is diverted from the river and channelled along the side of a valley before being dropped into the turbine via a penstock. The turbine drives a generator that generates electricity for a workshop. The transmission line can be extended to a local village to supply domestic power for lighting and other uses.

There are other configurations which can be used depending on the topographical and hydrological conditions, but all adopt the same general principle.

To determine the power potential of the water flowing in a river or stream it is necessary to determine both the flow rate of the water and the head through which the water can be made to fall.

The flow rate is the quantity of water flowing past a point in a given time. Typical flow rate units are litres per second or cubic meters per second.

The head is the vertical height, in meters, from the turbine (the point at which energy is extracted from the water) up to the point where the water enters the intake pipe or penstock.

Energy is always lost when it is converted from one form to another. Small water turbines rarely have efficiencies better than 80%; the remaining 20% comprises the kinetic energy remaining in the water downstream of the turbine and the energy that is converted into heat energy and noise. Power will also be lost in the pipe carrying the water to the turbine, due to friction.

By careful design, this loss can be reduced to only a small percentage. A rough guide used for small systems of a few kW rating is to take the overall efficiency as approximately 50%. Thus, the theoretical power must be multiplied by 0.50 for a more realistic figure.

Turbine Technology

Among the various elements of the plant, the turbine is the basis of energy production. Because it is a major part of the capital cost of the plant, and defines the financial return of the project, the turbine must be as efficient as possible within the budget.

Two distinct types of turbine are typical, but there are many refinements and different designs within these categories.

High head turbines are ideal for water that is fast flowing, possibly down a high and steep slope, but possibly at a low flow rate.

Low head turbines are ideal for high flow rates in water that is flowing slowly, possibly along a nearly horizontal path.

Small hydro Turbine technology is now quite mature, as a result of exhaustive and systematic research to optimise the equipment specific to small power plants. Analysis of real situations shows that small-turbines are neither scaled down large turbines or scaled up pico-turbines.

The design of small turbines must comply with the 3 fundamental requirements: simplicity (limited cost), high efficiency, and maximum reliability (minimum and easy maintenance).

 More about design considerations

Examples of SHP

It is also a versatile power source. As well as DC electricity, AC can be produced enabling standard electrical appliances to be used and the electricity can be distributed to a whole small community or village.

Common examples of devices which can be powered by pico hydro are light bulbs, radio and TV sets, refrigerators and food processors. Some pico-hydro turbines also allow mechanical power to be taken off directly, to power machinery such as workshop tools, grain mills and other agro-processing equipment.

A pico hydro system makes use of the power in falling water - it is an example of a high-head system. The figure on the right side shows the layout of a pico hydro system.

The main components