100 kw micro-hydro power plant operate in island mode and grid connected mode

1. Abstract

Small hydropower less than 100 kW that can be built on small rivers, which flows through or near their villages.

They have different characteristics, being influenced from the location on the water, construction material, drops of water turbines that convert hydraulic energy into mechanical energy and then into electricity via generator and generating schemes used in the scheme of operation.

The purpose of this project is to design, modeling and performance analysis of a 100kW micro-hydro power plant, able to operate both in island mode and low-voltage grid-connected mode.

To achieve this, we designed a Banki-Michell turbine that is relatively easy to build, which has a rather high efficiency (80%) and can provide enough energy taken from the flow of water and turned into mechanical power, and latter being used to drive an synchronous generator.

The simulation model of project is obtained using MATLAB/SIMULINK environment for effectiveness of the study.

Simulation results are also provided.

2. Introduction

Hydraulic engineering is based on the principles of fluid mechanics. However until now there does not exist, and probably never will, a general methodology for the mathematical analysis of the movement of the fluids.

Based on the large amount of accumulated experience there exists many empirical relationships to achieve practical engineering solutions with the movement of the water, the fluid that concerns hydroelectricity.

All hydroelectric generation depends on falling water. The first step to develop a site must address the availability of an adequate water supply.

Turbines transform the potential energy of water to mechanical rotational energy, which in turn is transformed into electrical energy in the generators.

From the beginning of electricity production hydropower has been, and still is today, the first renewable source used to generate electricity. It is also considered a cheap, environmentally friendly source of energy.

The large majority of micro hydro plants are «run-of-river» schemes. These schemes do not

change the natural flow much and also does not have the environmental problems

such as resettlement and land inundation associated with large dams.

But the turbine generates when the water is available and provided by the river. When the river dries up and the flow falls below some predetermined amount, the generation ceases. This means, of course, that small independent schemes may not always be able to supply energy, unless they are so sized that there is always enough water.

This problem can be overcome in two ways. The first is by using any existing lakes or reservoir storage upstream. The second is by interconnecting the plant with the electricity supplier’s grid. A grid is an interconnected network of power generating plants and transmission lines that supply power to a number of distributed consumers. Central grids cover a vast geographical area with a large number of generating plants and millions of

consumers. Isolated grids cover a smaller area which are not connected to a central grid and supply electricity to small towns and villages which are normally remote and far from larger load centres.

3. General principle of micro hydro

Power generation from water depends upon a combination of head and flow. Both must be available to produce electricity. Water is diverted from a stream into a pipeline, where it is directed downhill and through the turbine (flow). The vertical drop (head) creates pressure at the bottom end of the pipeline. The pressurized water emerging from the end of the pipe creates the force that drives the turbine. The turbine in turn drives the generator where electrical power is produced. More flow or more head produces more electricity.

Electrical power output will always be slightly less than water power input due to turbine and system inefficiencies.

Water pressure or Head is created by the difference in elevation between the water intake and the turbine. Head can be expressed as vertical distance (feet or meters), or as pressure.

Net head is the pressure available at the turbine when water is flowing, which will always be less than the pressure when the water flow is turned off (static head), due to the friction between the water and the pipe. Pipeline diameter also has an effect on net head.

Flow is quantity of water available, and is expressed as ‘volume per unit of time’, such as cubic metres per second (m3/s), or liters per minute (lpm). Design flow is the maximum flow for which the hydro system is designed. It will likely be less than the maximum flow of the stream (especially during the rainy season), more than the minimum flow, and a compromise between potential electrical output and system cost.

4. Site configurations

The objective of a hydro power scheme is to convert the potential energy of a mass of water, flowing in a stream with a certain fall (termed the head.), into electric energy at the lower end of the scheme, where the powerhouse is located. The power of the scheme is proportional to the flow and to the head.

According to the head, schemes can be classified in three categories:

- High head: 100-m and above

- Medium head: 30 - 100 m

- Low head: 2 - 30 m

These ranges are are not rigid but are merely means of categorising sites.

Schemes can also be defined as

- Run-of-river schemes

- Schemes with the powerhouse located at the base of a dam

- Schemes integrated on an canal or in a water supply pipe