In the spring of 2017, after a construction period of less than a year in the Finca Carmen Amalia area in south-western Guatemala the small-scale hydropower plant sharing the same name went online.
The typical diversion-type plant is owned by the Fernandez family who have been growing coffee crops in the Finca for several generations. The ideal topography of the landscape is now also being exploited to produce green electricity. The first plans for the construction of a small power plant were drafted in 2014. Building work commenced in March 2016. A maximum volume of 1200 l/s is diverted for electricity generation and passes down a 1.5 km underground high-pressure pipeline to a surge tank. From there it flows along an above-ground steel pipeline into the power house for use in the turbines. All the electro-mechanical and control-related infrastructure for the central station was provided by Ossberger, the southern German specialists for small-scale hydropower plants with immense international experience. At maximum water capacity the benefits of the crossflow turbine come to the fore in partial-load operation, as it is capable of guaranteeing a bottleneck capacity of 689 kW. All of the electricity generated is fed onto the public mains grid. In an average year the plant produces around 2.8 GWh of power.
The fertile volcanic earth in the Departamento Quetzaltenango region in the south-western part of Guatemala is ideal for the cultivation of a whole range of crops, such as corn, wheat, various types of fruit and vegetable, as well as coffee and sugar cane. The vast Finca Carmen Amalia area is approximately 50 km south of the regional capital Quetzaltenango, and coffee has been grown there for several generations. “In order to utilise the ideal topography and hydrology of the Finca area for energy production, Manuel Fernandez González – the head of the family – devised a plan to build a hydroelectric power plant there”, explains his son, Roberto Fernandez España, who developed and implemented the plant with the project manager Carlos de Leon. Financial backing for the building of the power plant was provided during the planning phase by the ARECA initiative (Accelerating Renewable Energy Investment). This body supports the implementation of renewable energy resource projects in Central America and Panama. Once numerous issues had been dealt with, such as local hydrology, environmental impact, geotechnics and a planning phase – which also encompassed the market situation, the actual main construction phase was initiated in March 2016 when excavation work commenced.
Building during the rainy season
Although the majority of the construction work was conducted during the rainy season between May and October, and despite the challenging geological conditions along the route of the pipeline, the project was implemented without any significant delays, states Roberto Fernandez. To prevent ground erosion, compensatory ecological measures included the planting of 12,000 trees and many deep-rooting plants alongside the diversion route. A concrete dam 12 m across was built for the main collection basin, from which the water flows into an open two-metre diversion channel. An open-air desanding basin with two separate chambers is also connected directly with the channel. Fitted with a sluice gate, the desander is located at the entry of the high-pressure pipeline. The initial 1.5 km underground section of the high-pressure tubes is made completely from plastic DN900 piping. The water is then fed through to a surge tank-type collection basin that serves to regulate the water level. From here the water flows along an above-ground DN800 steel pipeline on the final steep section to the power house turbines.
Made in Germany: In demand in Guatemala
While the above and below-ground construction work was carried out by local businesses, the operators favoured a ‘Made in Germany’ label for the centre’s technical infrastructure. The entire contract for electrical machinery was ordered via JC Niemann, an expert trading company specialised in European industrial-sector products and machines, and an established and trusted dealer working in Guatemala on behalf of the Ossberger turbine manufacturers. In November 2016 the turbines, generator and electrotechnical equipment embarked on the journey of several weeks from the port of Hamburg to Central America. On-site assembly and installation went very smoothly and were carried out by a local company contracted by JC Niemann. Ideally, when producing electricity, the crossflow turbine processes a maximum discharge of 1,200 l/s with a gross head of around 70 m, and offers a bottleneck output of 689 kW. Moreover, the robustly-built and hydraulically regulated machine is particularly good in part-capacity operation when there is a limited volume of water available. The drum-shaped runner was built especially for the two-cell turbine and is extremely effective and efficient, even when the flow of available water fluctuates significantly. In addition, the turbine masters driftwood and floating waste with ease. Such flotsam is forced underwater by the runner within half a revolution. A Marelli 12-pole synchronised generator converts the energy of the turbine. The air-cooled machine is directly coupled horizontally with the turbine shaft, rotating – as does the turbine – at 600 rpm.
Annual production of approx. 2.8 GWh
To ensure fully automated operation of the entire plant, Ossberger provided an automation solution they have already implemented successfully a hundred times, right around the globe. Their control infrastructure and software for turbine regulation are based on universally implemented industry standards to facilitate easy programming for the operation of the power station – without requiring additional computer hardware. In March 2017, subsequent to the completion of all installation tasks, the Carmen Amalia power plant generated electricity for the grid for the very first time – and has since been in uninterrupted service for two years. In an average year the plant operators expect to produce around 2.8 GWh of power. Guatemala remains a promising market for Ossberger. Since the Carmen Amalia power plant went online, the southern German company already completed a further two projects within the country. In fact, news of another successful bid for a project in Guatemala was received just as the editorial deadline was reached for this issue.