After around four years of construction, the Marañón hydroelectric power plant situated on the river of the same name in the Peruvian Andes region was connected to the grid in the summer of 2017.

This new construction project was commissioned by the Peruvian company Celepsa, which specialises in producing electricity from renewable sources. All of the electromechanical equipment for the power plant was supplied by the Austrian hydropower specialist GUGLER Water Turbines GmbH. When the plant started operating, this heralded the successful completion of another project in South America for the internationally renowned turbine manufacturers. GUGLER provided, as part of a complete package, three Francis spiral turbines including generators which were designed to be both highly efficient and easy to maintain, as well as all the electrical engineering and control technology. At full load, the machines combine to deliver a nominal output of almost 20 MW, in a standard year the plant can generate almost 420 GWh of green energy. Due to the remote location of the project at an altitude of around 3,500 metres above sea level, the project’s logistical requirements in particular proved to be extremely challenging.

With an average water flow of around 15,000 m³/s, the Río Marañón, which flows for a total of 1,905 km through Peru, is the larger of the Amazon’s two source rivers. Before the waterway flows into the Amazon Basin, it passes through both high-mountainous and semi-desert valleys as well as sections of tropical and subtropical rainforest. The energetic potential of the Marañón is used to operate a large number of hydropower plants with a considerable capacity. One of the most recent projects to be completed was delivered over a construction period of around four years in the Huánuco region in the Central Peruvian Andes. The project was financed and implemented by the Peruvian energy supplier Celepsa S.A., a subsidiary of the “Unión Andina de Cementos S.A.A” (UNACEM) group.

Austrian know-how in demand
Celepsa previously provided all the engineering for UNACEM’s Carpapata III power plant, which was also completed in Peru back in 2016. The hydropower specialist GUGLER Water Turbines GmbH was previously able to demonstrate its expertise by providing all the electromechanic equipment for this project in the Junín region. This excellent experience meant that the Austrians were once again asked to provide the technical equipment for the Marañón project. In this context, GUGLER project manager Roland Fleischmann emphasises the excellent working relationship with the clients again, which made it possible to conclude the project successfully and swiftly at the same time.

Construction site 3,500 m above sea level
To provide the legal framework, the operators established the company Hidroeléctrica Marañón S.R.L. Once the official administrative procedure had been completed, the project was finally able to enter the construction phase in the late summer of 2013. The remote location of the project region at an altitude of 3,500 m above sea level placed great logistical demands on the companies carrying out the work. The power plant‘s diversion principle required the construction of a weir, sand trap, penstock and power house. In addition, a 39 km overground high-voltage power line needed to be constructed for power transmission. To dam the Marañón, the operators relied on inflatable rubber dams with two weir sections. After discharge, the works water is only guided through a fine trash rack and on in a closed concrete channel to the sand trap. To allow the sediments to settle in the three de-sanding basins, the flow speed of the water is reduced by expanding the cross section upstream of the sand trap. This is followed by another concrete channel which ultimately opens into an upper basin. The basin acts as an intermediate reservoir for regulating the water level prior to the start of the penstock, which is around 500 m long and leads to the power house.

Heavy loads require bridge reinforcement
As with the Carpapata III project, the operators opted for Francis turbines with a horizontal shaft for generating power. However, the higher extraction water quantity means that three machine units are employed at the Marañón power plant. Both the turbines and the generators were transported by sea to the Peruvian capital of Lima in June 2017. Whereas the turbines left the European mainland from the port of Livorno, the generators made by the Spanish manufacturer Indar were shipped from Bilbao. Once they arrived in Peru and the customs formalities were dealt with, the power plant components continued their journey by road. The journey in trucks took around two weeks. To ensure that the extremely heavy equipment could be transported safely – one generator weighs around 45 t – several bridges on the route to the construction site had to be reinforced. The assembly team on the ground was organised by the GUGLER representative in Peru, Martin Modispacher, who provided the local experts on the ground through his own company “Hydro Power Andina”. The assembly work was undertaken over a period of around three months under expert guidance, with cooperation between two experienced GUGLER engineers and the local workers.

High level of efficiency guaranteed
According to Roland Fleischmann, at its peak the Marañón in the project region flows at a rate of around 500 m³/s, but in dry periods the amount of water is still sufficient to operate two turbines. Over the course of a year, the plant, which is optimised for full-load operation, achieves a plant factor (utilisation rate) of 80%. When there is a maximum supply of water, the Francis turbines with completely identical designs can each achieve a nominal output of 6561.3 kW. An extraction water quantity of 8.66 m³/s and a net drop of 84.5 m is available for each turbine. During peak loads, the turbines can thus achieve a maximum total output of almost 20 MW. The synchronous generators, which are coupled together directly in the horizontal direction, are designed for a rated apparent power of 8,000 kVA. The generators utilise a closed water circuit with heat exchangers installed underwater for cooling. Fleischmann emphasises that the technical design of the machines has been adapted precisely to reflect the hydraulic conditions at the location of the plant: “The turbines have been ideally matched to the flow conditions. This means that the plant enables efficient production of electricity both at full load and under partial-load operation and achieves a high level of efficiency all year round.” In addition, great importance was attached during the design to ensuring that the turbine is easy to maintain.

Plant produces almost 420 GWH per year
As was the case with the Carpapata III project, the electrical and control engineering equipment was also procured from the Lower Austrian company Schubert Elektroanlagen GmbH for the Marañón plant. The overall package comprised the electrical switchgear, control and protection systems, turbine regulators, the SCADA system and transformers. The power plant can be monitored and remotely controlled in its entirety through an online connection. Disruptions to the grid or elevated temperatures for individual components are registered automatically and in most cases can be rectified remotely. The intelligent control technology ensures fully automatic and highly efficient electricity production. The individual turbines are connected or disconnected depending on how much water is available. “Since the plant was completed last year, it has operated more or less constantly at full load, and the output has always been above 80%,” says Fleischmann. The commissioning of the plant was delayed by several months until the summer of 2017 because laying the power line proved to be very complicated. In total, around 85.6 million US dollars were spent on delivering the project. In a standard year, the plant can provide an average of 419.1 GWh of green electricity to the Peruvian energy grid.