Microhydro Equipment & System Design: Page 2 of 3


Inside this Article

A hydro-electric system uses the flow of water down a slope to create electrical energy.
1. Intake; 2. Screen
3. Vent Pipe
4. Penstock
5. Manifold
6. Pressure Gauge
7. Turbine
8. Alternator
8. Alternator
9 Transmission & Power Electronics

5 Manifold

You’ll need to figure out how to connect the penstock to the turbine using valves, tees, and elbows to construct a manifold (used for multiple nozzles on a turbine). It’s important to avoid or limit tight bends with small-diameter pipe or there will be additional friction loss.

6 Pressure Gauge

A pressure gauge is key for troubleshooting any hydro system—include one in the manifold. Position it upstream of the nozzle control valves so that the static (gross) head as well as the operating (net) head can be measured. If there is not enough water entering the intake, the pipe will begin to draw in air. Head will drop and demand must be reduced. Don’t partially close a valve to restrict flow, because it will reduce the pressure at the nozzle. Close valves fully (but slowly) if you do not want a nozzle in operation.

7 Turbine

The turbine must suit the site conditions, matched to the alternator in a package that works for your specific site’s head, flow, and operating voltage. A Pelton turbine works well at high heads, or for low flow. For high flow on very low-head sites, a propeller (aka low-head—LH) turbine that sits at the top of a vertical draft tube (see photos on pages 38 and 43). Turgo and crossflow turbines are options for intermediate site conditions. The ranges of all these turbines overlap and are well-documented by manufacturers.

Reliability, efficiency, and cost are important criteria for choosing a turbine. In cases where the rest of the system is very expensive, efficiency is more important than cost. It makes no sense to spend thousands on large pipes and cables, and then sacrifice performance to save a few hundred dollars on the turbine. Look for good technical support, and learn how to do the maintenance.

8 Alternator

Almost all domestic-scale microhydro turbines are supplied with permanent-magnet alternators (PMAs). The turbine’s output is converted to DC and fed to battery/inverter systems or to grid-tied inverters. Some manufacturers custom-build their alternators, but others find mass-produced brushless PM motors a cost-effective solution because they are low-cost, efficient, and reliable.

On larger systems, induction motors are sometimes used instead of PMAs for the same reasons. Induction motors can produce off-grid AC. Larger turbines that produce AC for direct use are more often supplied with brushless alternators with wound-field coils and automatic voltage regulators.

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