Small Hydro - Project Design

Project Design

Many companies offer standardized turbine generator packages in the approximate size range of 200 kW to 10 MW. These "water to wire" packages simplify the planning and development of the site since one vendor looks after most of the equipment supply. Since non-recurring engineering costs are minimized and development cost is spread over multiple units, the cost of such systems is improved. While synchronous generators capable of isolated plant operation are often used, small hydro plants connected to an electrical grid system can use economical induction generators to further reduce installation cost and simplify control and operation.

Micro-hydro plants may use purpose-designed turbines or use industrial centrifugal pumps, connected in reverse to act as turbines. While these machines rarely have optimum hydraulic characteristics when operated as turbines, their low purchase cost makes them attractive for micro-hydro class installations.

Regulation of small hydro generating units may require diversion of water around the turbine, since the project may have no reservoir to store unused water. For micro-hydro schemes feeding only a few loads, a resistor bank may be used to dissipate electrical energy as heat during periods of low demand. In a sense this energy is wasted but the incremental fuel cost is negligible so there is little economic loss.

Other small hydro schemes may use tidal energy or propeller-type turbines immersed in flowing water to extract energy. Tidal schemes may require water storage or electrical energy storage to level out the intermittent (although exactly predictable) flow of power.

Since small hydro projects usually have minimal environmental and licensing procedures, and since the equipment is usually in serial production, standardized and simplified, and since the civil works construction is also small, small hydro projects may be developed very rapidly. The physically small size of equipment makes it easier to transport to remote areas without good road or rail access.

Micro-hydro installations can also provide multiple uses. For instance, micro-hydro projects in rural Asia have incorporated agro-processing facilities such as rice mills - alongside standard electrification - into the project design.