Micro-Hydro Power Systems

Since I'll be spending the next 6 months blogging about my experiences in Malaysia, I might as well start by discussing why I'm actually going out there! It'll certainly be an amazing adventure, but I will be spending my time focusing on the engineering projects I've agreed to deliver.  

The Partner Organisation; Tonibung, develps micro-hydro turbine systems which provide electricity to remote, indigenous communities. The electricity generated can be used by the community to improve education, health care and welfare. So....what are micro-hydro turbines? How do they work

Micro-Hydro turbines are renewable power systems that convert the natural flow of water due to gravity into mechanical shaft power. This mechanical shaft power can subsequently be used to drive machinery such as generators to produce electricity.

Micro-Hydro Scheme - [Source]

Water is diverted and guided from a river to a settling basin where it is slowed allowing debris to settle. A canal then guides the water to a forebay tank, which ensures a constant head of water (the head or height of water level from the micro-hydro turbine is essential for defining the hydraulic energy) is maintained before entering the penstock. The penstock, which is essentially a pipe, leads the water from the forebay tank to the turbine of the micro-hydro. The turbine then converts the hydraulic energy in the flowing pressurised water into mechanical energy in the form of a rotating shaft. The shaft transfers the rotating energy from the turbine to a generator which converts the rotating mechanical energy to electrical energy.

In simple terms, the Micro-Hydro Turbine converts hydraulic energy to mechanical energy and finally (with the addition of a generator) to electrical energy.

Components of Micro-Hydro Turbine [Source]

The role of the control system for a micro-hydro is to maintain a constant turbine speed and electrical frequency output from the generator despite variations in electrical load due user demand (i,e. turning lights On/Off). The frequency of the electrical output from the generator (assuming a synchronous generator) is directly related to the speed of the turbine. To control the speed of the micro-hydro turbine and the frequency of the generator output, the control system can be either mechanical or electrical based. Mechanical based control operates by controlling a valve to restrict the flow of water into the turbine. Electrical based control operates by controlling the electrical load on the generator, by increasing or decreasing the resistive load on the generator, the output frequency/turbine speed can be controlled.

Components of Micro-Hydro Turbine With Control Systems [Source]

Mechanical based control is typically avoided due to cost, maintainability of moving parts and slow reaction time to changes in community demand. For electrical control, an Electronic Load Controller (ELC) is typically used. ELCs are cheap, reliable and are fast at reacting to changes in community demand.

ELCs maintain a constant generator output frequency/turbine speed by controlling the resistive load on the generator output. The ELC achieves this by diverting excess electrical power to a resistive dump load. By diverting electrical power between the user load and dump load, the ELC can regulate generator frequency/turbine speed.

So to put all this technical banter into context! If a user of the micro-hydro scheme was to turn on a kettle, the resistive load on the generator would increase. Due to an effect known as 'electrical braking', the generator would slow the turbine and reduce the frequency output from the generator. The ELC detects this drop in frequency and diverts excess power from the dump load to the user load in order to meet the power demand. The ELC diverts enough power to the user load to return the generator output frequency to the desired configuration.

My focus while out in Malaysia will be to design the ELC for a micro-hydro turbine. In what direction the design will take I'm unsure....it could be designed as a micro-controller based system using an Arduino, a Raspberry Pi, a PIC or maybe an FPGA with PLCs (Programmable Logic Controllers). The existing controllers in place will be need to be assessed before making a decision. The existing controller implementation used by Tonibung is purely analogue based.

I'm sure the project aims and objectives will become clearer once I meet the Tonibung, the partner organisation.