In the valley of Mallarauco, about 80km away from the Chilenian capital Santiago, farmers are cultivating avocados, lemons and oranges, with water from the river Mapocho used for irrigation of the plantations. The river water flows into the valley through a 20km long bored tunnel, which is then diverted into three smaller channels – the North, Central and South branches. The North and South channels follow the mountainside with a gradient of about 1°. The Central channel slopes steeply down into the valley.
The feasibility of producing power from this channel has been known for many years, but it was only an agreement between generating company Gestión de Proyectos Eléctricos S.A. (GPE) and the Association Channel Mallarauco (a group of more than 680 farmers in the Mallarauco valley) which allowed for the construction of a 3.5MW hydropower station. This station was developed to generate sufficient energy to supply seven thousand households and also help finance the maintenance and repair of the channel system.
The Mallarauco hydro station was put into operation in September 2011. Work on the project cost US$11M and will generate 24,000MWh per year. The capacity of the existing channels had to be modified to reach a total usable water quantity of 3.5m³/sec. The net head that could be used from the 50m long steel and polyethene tubes is 110m.
The complete electro-hydraulic equipment for the project has been manufactured, delivered and commissioned by Germany’s Wasserkraft Volk AG (WKV AG). The power plant is equipped with a WKV Francis turbine of 3.5MW and a WKV synchronous alternator of 3.900 kVA, generating power at 3,3kV, 50Hz, 750rpm. For power conduction, a 20km long 13.2kV line had to be constructed that was partially set-up using helicopters, due to mountainous terrain.
The local farmers use the water from the turbine (that would range between 1.8-3.5m3/sec) for irrigation of their plantations. This generates extra revenue that allows farmers to settle the high costs of channel improvement and irepair. The association will re-invest all the income into the improvement of the network of channels. It is anticipated that the power plant will help to finance close to 50% of this.
This type of power plant supports the ambitious goal of diversification of the national energy mix, generating clean and renewable energy. In fruit farming in the future, the CO2 discharge will be determinant for worldwide export. The more clean energy is used, the better prices for farmer’s products abroad.
This kind of project is one of a number of potential small power plants that might deliver another 800MW of energy to the country. These power plants are an important part of the solution to the energy problem.
At the EXPO APEMEC in Chile the project was heralded as an excellent example for utilization of small water channels in Chile. Furthermore, Wasserkraft Volk AG, based on several successful deliveries for various projects, was named as "Best Supplier for Small Hydro Power Systems".