In the past few years, in order to sustainably improve electricity supply grid stability in Honduras, energy providers have increasingly focused on expanding previously unexploited hydroelectric power potential.
In the summer of 2018, in the department of Santa Bárbara in the north-western part of the country – the 18 MW Pencaligue power plant went online to provide a small town nearby with electricity. The operators, Hidroeléctricas de Occidente S. de R.L., implemented the project successfully with a significant contribution having been made by Austrian industry expertise. Working as a subcontractor, Schubert Elektroanlagen GmbH of Lower Austria delivered and installed the entire portfolio of electric and control technology for the power plant. The overall contract for electromechanical infrastructure, including two Pelton turbines with a maximum capacity of 7 MW and one 3 MW Pelton turbine, was awarded to GUGLER Water Turbines GmbH of Upper Austria.
Alongside Haiti, Honduras is one of the poorest countries in Central America and over 70 percent of the country’s almost nine million inhabitants live below the poverty line. Outdated and lacking infrastructure and power plants mean that power failures are a common occurrence in many regions of the country. In order to improve the response to these bottlenecks, emphasis has been shifted to the expansion of regenerative energy sources – particularly toward hydroelectrics. The unreliability of the power supply in the town of Atima in the department of Santa Bárbara in north-western Honduras was the starting point for the Pencaligue hydropower project. The construction of the power plant was based around the idea of redirecting a local body of water which would first flow through the mountain via a grade tunnel before being guided by a penstock to the turbines. Named after the region itself, the project had already been authorised in 2010, and some earth engineering had already taken place. However, work was halted and the project postponed for several years due to a lack of financial backing. In 2016 the project was taken over by the energy providers at Hidroeléctricas de Occidente S. de R.L. and construction work on the implementation of the plan recommenced the following year.
OPERATORS RELY ON AUSTRIAN EXPERTISE
Hidroeléctricas de Occidente awarded the Austrian hydropower allrounders at GUGLER Water Turbines GmbH the contract to provide all the electro-mechanical equipment for the project in December 2016. The Upper Austrian business had already installed two Pelton turbines for the same customer in 2015 for the 10 MW Mezapa power plant in Honduras, thus recommending itself for further projects in the country. GUGLER chose Schubert Elektroanlagen GmbH from Ober-Grafendorf in Lower Austria company to serve as their subcontractor and supplier of electrotechnical and control infrastructure. In 2016 their highly and internationally experienced specialists had already cooperated to complete the 12.9 MW Carpapata III project in Peru. In 2017 they worked together again on another Peruvian project – Marañón – to achieve 19.7 MW of bottleneck capacity. Nevertheless, the Pencaligue contract was the first joint project in Central America. Due to the high levels of crime in the country a special camp was built at the plant headquarters to accommodate the construction staff and engineers, and was protected by armed guards around the clock.
PENSTOCK FOLLOWS GRADE TUNNEL
The water collection basin at the power plant was fitted with a head dam gate, with a side arm flow release of up to 2.9 m³/s for the generation of electricity. After release, the flowing water is fed into a voluminous desanding basin to allow the fine sedimentary particles to settle out from the water. A hydraulically operated flush gate ensures the sand and sediment are returned to the natural flow of the water. The cleaned water is then directed down a three-kilometre grade tunnel blasted into the mountain. Having completed its underground passage, the water enters a level-regulation pool, after which it is channelled down a penstock approximately 3.8 km in length. An unavoidable topological rise in the pipeline between the steel DN1700 and DN1500 sections necessitated the building of a surge chamber to release pressure at the highest point. To reach the purpose-built powerhouse the works water climbs to a gross head of 413 m.
TURBINES SERVE BROAD RANGE OF PURPOSES
GUGLER’s Project Manager Roland Fleischmann explained that when designing the machine, the main focus of the designers was on maximising efficiency for a system working at partial capacity. The volume of water made available during the rainy season between October and May can fluctuate immensely, so three Pelton turbines were installed – two larger and one smaller machine – to optimise efficiency. On a technical level, the turbines were designed and manufactured as very easily-regulated 2-jet versions with horizontal shafts. The original project developers had already planned for the integration of a fourth turbine in the power house, but at the time the over-optimistic forecasts regarding available water volumes meant it was never installed. While the larger turbines produce a bottleneck output of 7,334 kW for an additional flow of 2 m³/s per turbine, the third unit can ensure a bottleneck output of 3,299 kW at a maximum flow volume of 900 l/s. Synchronised generators coupled directly with the turbine shafts serve as energy converters. On taking over the project the current operators also took ownership of the generators purchased by the original project developers – which had remained in storage for several years. Hence, the larger turbines had to be adapted for a perfect fit. The smaller unit was provided in its entirety by the Upper Austrian specialists, and also included a Marelli-manufactured generator.
GRID OPERATOR TAKES CONTROL
Lukas Rudolf, Schubert’s commissioning inspection technician, explained that – in terms of electrotechnics – it became essential for the Honduran grid operators to ensure they could control the plant remotely. “Fairly late in the day the grid operators added the condition that they had to be able to set the active and reactive power of the system at any time. Ultimately, it was only possible to clarify and deliver on these demands shortly before the plant officially went online, when the responsible parties were finally able to deliver the specifics.” Basically, the grid operator is provided with all the key readings for the power plant. These form the basis for increasing and decreasing output in order to improve the facility’s capacity to counteract power supply fluctuation in the region.
ELECTRICS AND CONTROL TECHNOLOGY
Schubert’s consignment included a SCADA system programmed to WinCC and the full portfolio of electrotechnical equipment – and also entailed provision of a 36-kV gas-insulated medium-voltage switch system for grid feed and power metering purposes. Three turbine power transformers (2 x 8.75 MVA and 1 x 3.75 MVA) guarantee that the voltage of the energy produced is adapted correctly before it is fed onto the public grid. A separate 200 kVA auxiliary power transformer was also provided. The components regulating the control of the three turbine units were installed in purpose-built control cabinets. Alongside the PLC turbine controls the cabinet also contains the excitation power components and the plant’s electrical protection parts. The 480 V to 24 V low-voltage components were also installed in specially planned control cabinets. An emergency power diesel generator was provided as an additional operational safety measure in case of complete power outages.
PLANT ONLINE FOR NEARLY A WHOLE YEAR
Once final installation work had been completed and the entire system approved by the grid operator, the power plant went into operation in the summer of 2018. Subsequently, trials were carried out for a range of operating conditions and requirements, and fine-tuning was done to maximise power generation efficiency. Independently of each another, following the transition from trial status to normal operation, the project managers at both GUGLER and Schubert gave a positive summary of the project and their first joint operation in Honduras. In only a few months the plant will be celebrating its first full year online. The operating company has estimated average annual power output of 100 GWh.