Grenada and Geothermal EnergyNovember 9th, 2009
Grenada and Geothermal Energy?
By Matthew Simon
The term geothermal comes from the Greek “geo”, meaning earth, and “thermos”, meaning heat, thus geothermal energy is energy derived from the natural heat of the earth. The earth’s temperature varies widely, and geothermal energy is usable for a wide range of temperatures from room temperature to well over 300°F. For commercial use, a geothermal reservoir that is capable of providing hydrothermal (hot water and steam) resources can be quite convenient. Geothermal reservoirs are generally classified as being either low temperature (less than 150°C) or high temperature (greater than 150°C). Generally speaking, the high temperature reservoirs are the ones suitable for, and sought out for, commercial production of electricity. Geothermal reservoirs are found in “geothermal systems,” which are regionally localized geologic settings where the earth’s naturally occurring heat flow is near enough to the earth’s surface to bring steam or hot water, to the surface.
The uses of geothermal energy include a broad range of technology options, from Geothermal Heat Pumps, (in temperate countries) which require heat from only a few feet below the ground, to electrical generation obtained from heat miles below the surface. Geothermal fluids are also used for industrial purposes, such as food processing, recreational (spa use) and agro and aquaculture uses.
Geothermal energy is abundant in the Earth’s subsurface. Much of it may be attributed to the remaining heat from the Earth’s formation, while the rest is formed through the process of radioactive decay, which generates energy in the form of heat.
As the heat accumulates, it is slowly dissipated toward the surface through the processes of conduction and convection. The heat found closer to the surface has undergone significant degradation, creating a spectrum of resource “quality,” with higher temperatures generally deeper and lower temperatures more superficial. However, depending on geography, the subsurface temperatures may vary
Grenada, owes its 33km (21 miles) long and 19km (12miles) wide land mass to volcanic activity, proof of which is manifested in the still active, “Kick em Jenny” volcano which is also evidence of potential geothermal sources.
The idea of exploiting this possible sustainable energy source has been with us for quite some time and as early as 1981 and agreement was signed between the Government of Grenada and the Latina American Energy Organization (OLADE) to conduct a Reconnaissance Study of the Geothermal Resources of Grenada. The company Geotermica Italian was contracted to carry out this study, in May of 1981.The main objective of a geothermal Reconnaissance Study was to ascertain, through geo-volcanological and hydro-chemical investigations, the occurrence of shallow thermal anomalies suitable for economic production of high enthalpy geothermal fluids.
This Study consisted of three phases; Data Collection, Fieldwork and Laboratory Analysis and Interpretation and was carried out between the month of May and December, 1981. This methodology was recommended by OLADE and aimed to search for high enthalpy geothermal fields in volcanic regions, and seeks to discover the following elements. (John Auguste,2009)
- A source of heat relatively close to the surface with thermal capacity sufficient to heart a large volume of rocks in the superficial part of the earth’s crust.
- A reservoir, in which geothermal fluids circulate, which is close enough to the surface to be reached by medium deep drilling.
- An adequate supply of water I reservoir.
- An impermeable cover over the reservoir which is tick enough to prevent the dissipation , through convention of the heat and of the fluids towards the surface and to protect the reservoir from infiltration of cold meteoric waters.
The results of the study demonstrated that Grenada has at least one area with very promising geothermal possibilities. This area is that volcanic massif of Mt. St. Catherine, Located on the central part of the Island. There is significant evidence of the presence of geothermal fluids of medium-high enthalpy (130 degrees -170 degrees Celsius.
The results of the hydro-geochemical investigations also suggested the highly probable occurrence of a thermal anomaly in the area of Mt. St. Catherine and good evidence to suggest the presence of geothermal fluids of medium- high enthalpy (130-170 Degrees Celsius) was discovered. One such piece of evidence was the presence of a large area of hydrothermal alteration in the zone of the Red River, to the west of Mt. St. Catherine.
It was strongly recommended that a prefeasibility study be conducted in the Mt. St. Catherine area. The project would be divided into two phases. Phase one being a Complementary Geological and Hydro geochemical investigations and Phase two, Slim Hole Drilling. This study was carried out between August 1992 and March 1993 by Geothermal Management Company (GMC), Inc, and Don Michaels Associates’ after more than a year of discussions on the proposed work programme.The main elements of the study included; Literature Reviews; Arial Photo Evaluations Interviews (public & Private Sectors); and Data Interpretation and Documentation
GMC’s prefeasibility study revealed six specific sites as delineated by the hydro geochemical work in the area. These sites are: Castle Hill South , Chambord ,Hermitage, Peggy’s Whim ,Claboney, Mt. Hope, Adelphi, St Cyr , Plaisance , Hapsack
In light of the investment climate, the anticipated need for increased electrical power in the near future, and the encouraging geological and hydro chemical evidence manifested, three (3) of the best sites were selected for additional Phase II work: Castle Hill South, Clabony , Mt Hope, and Adelphi in St .Cyr.As a result of the GMC prefeasibility study the proposed geothermal model includes; one or more central heat sources (molten Magma) at depth near Mt. St. Catherine and beneath the Kick-’em -Jenny /Isle de Caille offshore area;
The proposed model also presumes the existence of Reservoir rocks comprised either if volcanic products of carbonate formations, already extensively fractured and capable of hosting circulating thermal fluids in commercially viable quantities. Also included in this model is, well developed fracture networks, with permeability that can be maintained by recurrent regional seismicity, which can be meteoric waters and fluids within reservoirs. Additionally this model includes a recharge mechanism based on the 4000mm (157 inches) of rain that falls on higher slopes of windward side of the mountains.
Prefeasibility investigations on the island has confirmed that geothermal explorations and development are also feasible with regards to all non resource related topics including laws labor matters, land availability ,water use , duties ,fees, taxes, investment incentives, capital repatriation, site occupation , transportation and environmental affairs.
These results coupled with the geological and geochemical data which shows irrefutable evidence of molten magma at shallow depths near the northern tip of the island and the existence of geothermal travertine’s in Chambord, demonstrate that there is significant potential on Grenada, for the exploitation of commercial quantity geothermal resource.
Here is how geothermal energy works.
Dry Steam ower plants which directly use geothermal steam to turn turbines were among the first type of geothermal power generation plants built. They use steam from the geothermal reservoir as it comes from wells and route it directly through turbine/generator units to produce electricity.
Schematic of the dry steam power plant.
Flash steam plants are the most common type of geothermal power generation plants in operation today. They pull deep, high-pressure hot water into lower-pressure tanks and use the resulting flashed steam to drive turbines. The water is used at temperatures greater than 360°F (182°C) and is pumped under high pressure to the generation equipment at the surface. Upon reaching the generation equipment, the pressure is suddenly reduced, allowing some of the hot water to convert or “flash” into steam. This steam is then used to power the turbine/generator units to produce electricity. The remaining hot water not flashed into steam, and the water condensed from the steam, is generally pumped back into the reservoir.
Binary cycle geothermal power generation plants differ from dry steam and flash steam systems because the water or steam from the geothermal reservoir never comes in contact with the turbine/generator units. In the binary system, the water from the geothermal reservoir is used to heat another “working fluid,” which is vaporized and used to turn the turbine/generator units. The geothermal water and the “working fluid” are each confined in separate circulating systems or “closed loops” and never come in contact with each other. The advantage of the binary cycle plant is that they can operate with lower temperature waters (225°F to 360°F) by using working fluids that have an even lower boiling point than water. They also produce no air emissions.
Environmental concerns: Across the full life cycle of all geothermal technology options, the environmental footprint remains small in comparison to other, conventional power plants because the conversion equipment on the surface is relatively compact. While relatively minor compared to conventional power conversion technologies, geothermal energy does have associated environmental concerns. Successful geothermal production requires the use of a specific medium, typically water or steam, to bring the resource (heat) to the surface. In situations where naturally occurring water is not adequate for sufficient power production, water will be piped in from a secondary location, which may cause water right issues.
An additional environmental concern surrounding geothermal power production is the possibility of geothermal fluid circulated from deep subsurface reservoirs leaching into groundwater and causing contamination. There are also concerns about induced seismicity and subsidence as a result of fluid injection or withdrawal, respectively. At this juncture, however, research suggests that these issues can be managed to provide a sustainable resource. Geothermal energy offers the nation a clean, domestically abundant, renewable resource that can make significant contributions to base load power generation.
Benefits to Grenada
Employment generation: The growth of a viable geothermal industry in Grenada will create jobs through all phases of its development – from exploration to operation and the management of an expanded, modernized “smart grid.” The jobs created will be largely sustainable and, probably, higher-paying than others available for an equivalent level of education. This “green” job growth will also spur training requirements and other affiliated services, including the expansion of public- and private-sector research.
Reduction in the nation’s energy bill: Presently Grenada imports over $118,000,000 worth of petroleum products, a significant amount of which translates into electricity production, a viable geothermal industry will signify the reduction in Grenada’s energy bill, allowing for the increase in the country’s spending power.
Fulfillment of environmental Obligations.. Today, near-zero emissions from geothermal power plants are achievable with the use of binary plant technologies. Other plant technologies do have some emissions, but these are primarily limited to water vapor with little pollutant content. A viable geothermal industry will facilitate Grenada’s ability to significantly reduce the level of Greenhouse gas emissions and other environmental hazards that are usually associated with the use of fossil fuels, thus enhancing the nation’s ability to meet its commitment to the Kyoto Protocol and other similar international protocols or agreements.
Sustainable Development. Derived from naturally occurring processes, geothermal energy is renewable resource. Hence an investment in geothermal exploration today could mean available benefits not only for Grenadians today but for generations to come. A lot of lip service has been given to Sustainable development in recent years. A viable Geothermal Industry will provide Grenada with a tremendous opportunity to give credit to our words.
Auguste.J.,2009, Situation and Perspectives of Geothermal Development in Grenada.
Category/ies:Geothermal Energy, Grenada Articles.
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