Basic Hydro Power - Part 4

Understanding the principle of head and flow and the importance to get correct data of them, then it is time to know more about components of a scheme. The basic components of a micro hydro scheme is illustrated below (source: MHP Scout Guide, GTZ Ethiopia).

It's start from the flow diversion structure that diverts water to the intake structure. Then water is channeled via headrace channel and eventually reaches forebay tank before entering the penstock. Different setup might happen especially for reaction turbines (e.g propeller) which usually need draft tube instead of penstock. Exiting penstock, water enters the turbine and move the runner that will drive generator to generate electricity. Turbine, generator and control equipments are stationed in a power house.

So basically those are the components of an MHP scheme. The rest e.g. trash rack, spill way, gates, valves are considered as important accessories. Some components such as intake structure and forebay tank also have other function such as flow regulation and suspended solid sedimentation. Flow regulation can be done using gates and also spillways. Sedimentation can be achieved by specific design of the tank. Since water quality is also important aspect (solid content and also chemical characteristic (acidic for example) of water), then examination of water sample is also important. This will define the material quality to be used and make approximation of equipment lifetime. 

Anyway, understanding the core components of simple, conventional MHP scheme is very important because usually those components (civil components) take up most of the construction cost. The more difficult terrain one has, the more money you need to provide. But it is also depending on the level of service wanted. Simple small service does not need massive and complete components. There are very small systems (below 1 kW) that can run (maybe not reliable enough) smoothly with simple and cheap scheme components (e.g. PVC pipes, no concrete diversion structure etc.). This kind of system might only serves one family or two. Conventional electrified water wheels use this kind of approach (non pressurized system). 

Sizing the scheme is another discussion. For now, knowing the components and roughly knowing where to put the component is more important. A kind of sharp 6th sense can be developed for siting MHP components. One only needs to practice a lot and fail a lot and cope with the available budget. For more reading one can check this Good & Bad of Mini Hydro Power.