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Table 4: Countries generating geothermal power in 2010Bog'liq 34. FS-Green-TechnologyTable 4: Countries generating geothermal power in 2010
Source: Alison Holm and others, Geothermal Energy: International Market Update (Geothermal Energy Association, 2010). Available from
www.geo-energy.org/pdf/reports/gea_international_market_report_final_may_2010.pdf (accessed 06 March 2012).
The locations of geothermal power plants are mainly limited to areas with a hydrothermal resource and highly
permeable rocks. Geothermal resources that are relatively dry, featuring rocks with low permeability and
thereby insufficient water content, are undevelopable with current commercial geothermal technologies. How-
ever, enhanced geothermal system (EGS) (also hot dry rock, hot wet rock or hot fractured rock technology) is a
technology being developed to use the resources that traditional geothermal technologies cannot exploit. EGS
technology is under demonstration trials in several countries in the European Union.
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“Geothermal direct use” refers to the use of heat that comes directly from the geothermal source. In cold
climates, water from a hydrothermal source is used for heating, such as in buildings, greenhouses and district
heating. In warmer climates, geothermal heat has agricultural and industrial applications.
A geothermal heat pump (GHP) (also referred to as GeoExchange, earth-coupled, water-source and ground
source heat pump) uses the moderate temperature of the ground to raise the efficiency of heating and cooling
of buildings. The GHP application of geothermal energy is widespread in colder climates. However, the technol-
ogy is fundamentally different from what is used for geothermal power generation and the market segment and
applications are also different.
Fuel cells
Fuel cells convert the chemical energy contained in hydrogen to electricity and heat using an electrochemical
process. Inside a fuel cell, hydrogen electrochemically merges with oxygen to create electricity, resulting in
water and potentially useful heat as by-products. There are many types of fuel cells, though in general, they all
share the same basic configuration, featuring two electrodes sandwiched around an electrolyte. The types of
fuel cells are categorized by the electrolyte substance.
Power produced by a fuel cell depends on the fuel cell type, size, operating temperature and the gas supplied.
Hydrogen is the most optimal fuel for use in fuel cells. However, other hydrogen-rich fuel sources, such as biogas
from waste treatment and natural gas, which are rich in methane, can also be used as fuel. Fuel cells can be
used for backup power, power for remote locations, distributed power generation and combined heat and
power applications. To sustain electricity generation, though, the fuel needs to be supplied continuously; thus a
reliable supply of gas or a bulk storage system is needed.
Because fuel cells do not use combustion, emissions are much lower, and conversion efficiency is higher than
with conventional thermal power generation. A typical conventional combustion-based power plant has
around 33–35 per cent efficiency, while fuel cell systems can generate electricity at efficiencies up to 60 per
cent.
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Unfortunately, fuel cell technology has not advanced to the point where it can compete with conventional
power generation. The two main barriers to the commercializing of fuel cells are cost and durability. Material and
manufacturing costs for fuel cells are high compared to traditional combustion systems, and fuel cells have not
demonstrated the needed system reliability and durability to compete with existing technologies.
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