Geothermal Power Plant in Cerro Pabellon

Cerro Pabellón Power plant is owned by Geotérmica del Norte (GDN), the joint venture between Enel Green Power Chile (83.65%) and Enap (16.35%).
This Power Station has a long and successful story that starts at the beginning of 2000, when Enel moved the range of action beyond national borders, leveraging its 100 years of experience in GEOTHERMAL sector.
The chosen area is the central America, in particular El Salvador and Chile, where the characteristics of the territory and the huge geothermal potential allow Enel to replicate the Italian experience.
Cerro Pabellón is a high-enthalpy binary cycle plant and thanks to the excellent and reliable experience that Enel got with Pentax pumps in the Larderello geothermal Italian district, Marly pumps were chosen in order to grant the best performance in a very heavy duty operation conditions.
In the 2020, GDN signed a contract to Pentax to supply N°14 “booster” pumps units to relaunch the geothermal steam into the binary plant system.

In the diagram is synthetically given the complete production process of the Cerro Pabellon Power plant.

1. In the sector 1 of the diagram, the Pentax multistage horizontal centrifugal pumps are located in order to boost the brine fluid of the ground well into the “Pre-Heater” exchanger.
2. In the sector 2 of the diagram, the Pentax Vertical Turbine centrifugal pumps are located in order to reinject the condensate fluid into ground well to return the liquid in the original reservoir.

The GDN power plant is located in the desert of Atacama in the Pampa Apacheta plateau, at about 100 km at NE of Calama town at 4500m altitude, close to the border of Bolivia.
Cerro Pabellon Power Station will have a capacity of about 81 MW, thanks to the 3 phase Power plant expansion under execution, which is equivalent to a total 600 GWh per year.
Pentax in this plant already provided the Vertical Turbine pumps for the condensate steam re-injection phase.
In the 2020 Pentax supplied n°14 units of Multistage Horizontal pumps as booster pump to relaunch the ground steam into the binary system Heat-exchanger to feed the production Turbine.
In this case the pump technical goals were very challenging since the main operation data was as follow:

  • Fluid temperature 165°C
  • Pump duty point : 300m3/h @ 40m
  • Required NPSH: 1,2 m
  • Fluid nature: pressurized Geothermal water
  • Water corrosion element: 12.300ppm of Chlorides
  • Water solids (Silica sand) > of 10 gr/m3
  • Site elevation: 4500m a.s.l.
  • Pump ambient temperature -35°C / + 35°C

The Challenge of Pentax pumps in this application is to boost the Brine at 165°C .
This Brine fluid may content relevant (> 10 mg/L) of suspended solids, coming both from the geothermal reservoir (silica sands) and precipitating from a supersaturated brine (SiO2 colloids, polymers, silts)”. The source of the fluid is from down ground reservoir by wells of about 1.800 m depth .
Marly pumps model HPMA150.6/4R-X-T53B-75KW-6P is boosting the fluid directly in the heat-exchanger of the binary system in order to heat up the turbine fluid for electric production.
In order to do that a special pump execution fully made of Stainless Steel AISI316 was made with a very high suction property at 950 rpm speed.

Pump performance characteristics, on which we can appreciate the hydraulic efficiency of 76,6% and the NPSH value of 1,1m
To make the pump resistant to the chemical and mechanical abrasions effects,
the following features were adopted:

  • Double Mechanical seal cartridge design according to Plan 53B
  • Peek ST530 material on impeller wear-rings and bushings
  • Peek ST530 material on Drum sleeve
  • Stellite 706/712 material is used for suction pump bush-bearing
  • Double mechanical seal – Plan 53B
  • All pump and mechanical seal O-rings made of FFKM
  • Special design of the 1st pump impeller for low NPSH value.
  • Special motor design for Inverter operation at 4500m elevation
  • Pump ball-bearing oil lubricated
  • PT100 temperature sensors on the pump and motor bearings

Pump under performance test at Pentax laboratory

Double mechanical seal system type Plan 53B.
Process side materials are: SIC/SIC/FFKM/AISI316
Cooling liquid is glycol 50% mixture suitable for -40°C

Pentax pump model HPM150/3-X-TB52-75-6 installed in the Cerro Pabellon Power plant