Survey of Energy Resources 2007
Geothermal Country Notes
Nicaragua is the Central American country with the greatest geothermal potential, in the order of several thousand megawatts. Reserves that can be estimated with a higher degree of confidence total about 1 100 MWe. Medium- and high-temperature resources are associated with volcanoes of the Nicaraguan Depression, which parallels the Pacific Coast.
Geothermal exploration began at the end of the 1960s, focussing on the Momotombo and San Jacinto-Tizate geothermal fields. Studies increased after 1973, at a time when the oil crisis had a large impact on Nicaragua's economy. Geothermal electricity production started at Momotombo in 1983.
Exploitation of geothermal power in the Momotombo area, located at the foot of the volcano of the same name, began when the first 35 MWe single-flash unit was commissioned in 1983. A second 35 MWe unit was added in 1989. Gross output of electricity reached a peak of 468 GWh in 1992 but subsequently fell away to a low of 102 GWh in 1999 owing to over-exploitation of the field and lack of re-injection.
In 1999, ORMAT secured a 15-year contract to improve electricity output at Momotombo. Since then, the company has drilled four deep wells (OM-51 to OM-54), and of these, only OM-53 was a good producer (9-11 MW). A number of wells have been cleaned of scale and chemical inhibition systems installed. About 80% of waste geothermal fluids are being injected back to the reservoir and a new reservoir management plan has been implemented. Since May 2002, these efforts have increased and stabilised the electrical output of the flash plant at about 29 MWe. In November 2002, a 7.5 MWe binary energy converter came online, raising total generation capacity at Momotombo to 77.5 MWe. The field now has 12 production wells, and four injection wells.
The San Jacinto-Tizate field was granted an exploitation licence in 2003. The project proposed consists of a plant of 20 MWe combined-cycle technology (Phase I) followed by a 46 MWe expansion using condensing turbine generation (Phase II). At the start of 2007, 2 x 5 MWe back-pressure units were operational (Stage 1 of Phase I). An additional 10 MWe will represent Stage 2 of Phase I and subsequently Phase II will add 46 MWe, bringing the total installed capacity to 66 MWe.
Nicaragua's total geothermal electricity output has been on a rising trend since 1999 and in 2006 totalled 310.8 GWh.