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Small Hydropower Plant Perlen - Switzerland; A siphoned rebuild - high efficiency at low cost

small hydropower

LOW-COST POWER FROM A SMALL HYDROPOWER PLANT THANKS TO OPTIMAL SIPHON LAYOUT

In Switzerland, notable energy potential lies in low head hydropower plants currently out of service obsolete. A shown by the recently rebuilt Perlen ultra low head hydropower plant, innovative technology can make renovation cost effective for industrial self-consumption even in the context of low energy tariffs.Surprisingly enough, pre-feasibility studies revealed that rather than one or two horizontal turbines, the optimal solution here would be three vertical-shaft units - mainly because civil engineering and mechanical equipment would be much simpler.

Perlen is Switzerland's first small hydro power plant (SHPP) with fully integrated siphon turbines and no shut-off valve or gates. This rebuild concept with three vertical-shaft single regulated Kaplan units not only saved investment costs, but also reduces maintenance and operation outlay. By renovating the headwater canal and intake at the same time, overall energy costs have been sustainably optimized for decades to come.

 

Four key high-performance elements

Small Hydropower Plant Perlen
Spiral casing

1.Spiral casing

Thanks to high-precision shuttering, the hydraulic contour of the concrete spiral casing ensures optimal intake flow conditions. As a result, pressure head and kinetic energy are uniformly distributed around the turbine stay-vanes.

Turbine runner

2. Turbine runner

The adjustable blades of these classic Kaplan runners are automatically regulated for optimal exploitation of available flow.

Small Hydropower Generator

3. Generator

The three low speed 24-pole generators are directly driven without transmission, thus reducing noise and maintenance outlay. They are also more efficient than high-speed gear driven generators.

Draft tube Draft tube

4. Draft tube

Three high-efficiency draft tubes convert the residual kinetic energy into suction head, thus boosting turbine performance.

Air technology instead of costly shutoff valves

With the siphon concept, the highest point of the turbine inlet is located well above headwater level. As a result, no water can flow into the turbine except when needed.Instead of costly shutoff valves and regulated distributor, only stay vanes are required.

Deaeration for startupn

Deaeration for startupn
A small size standard vacuum pump is enough to suck in water ready for startup.

Normal shutdown
Turbine shutdown is normal: just close the runner vanes. Thanks to the air-tight spiral casing, the turbine stays filled with water for hours - ready for instant restarting.

Emergency shutdown by aeration

Emergency shutdown by aeration
Opening the air valves immediately empties the turbine to headwater level. Then it simply runs to standstill in air. The large air valves(on the left) ensure fast emptying and protect the generator from overspeeding. This concept is ideal for fairly constant flow conditions, as in Perlen.

Technical Data small hydro power plant Perlen

Gross head (~ equal to net head) 2,7 m average (range 2 to 3,4 m)
Rated flow 3 x 15 m^3/s
Maximum total flow 48 m^3/s
Rated power output 3 x 342 kW = 1026 kW
Generator data 3 x 440 kVA / 500 V / 125 rpm
Group efficiency at rated load 86% (cos phi = 1.0)
Single-regulated Kaplan turbine data 2'100 mm runner dia., 4 CuAI-bronze blades
Shaft and bearing concept Vertical shaft, direct-coupled generator
Siphon setting 50 cm above headwater level
Mean annual energy production 7'800'000 KWh p.a