Thursday, September 29, 2011

Worldwide Geothermal Energy Usage

Geothermal energy is thermal energy generated and stored in the Earth. Thermal energy is energy that determines the temperature of matter. Earth's geothermal energy originates from the original formation of the planet (20%) and from radioactive decay of minerals (80%). The geothermal gradient, which is the difference in temperature between the core of the planet and its surface, drives a continuous conduction of thermal energy in the form of heat from the core to the surface.

Geothermal Resource Type

Table 11.1 is based on data for 2008 reported by WEC Member Committees for the present Survey, supplemented by information submitted to the World Geothermal Congress 2010. Of the countries utilising their geothermal resource, almost all use it directly but only 24 use it for electricity generation. At end-2008, approximately 10 700 MWe of geothermal electricity generating capacity was installed, producing over 63 000 GWh/yr. Installed capacity for direct heat utilisation amounted to about 50 000 MWt, with an annual output of around 430 000 TJ (equivalent to about 120 000 GWh).

The annual growth in energy output over the past five years has been 3.8% for electricity production and around 10% for direct use (including geothermal heat pumps). Energy produced by ground-source heat pumps alone has increased by 20% per annum over the same period. The low growth rate for electric power generation is primarily due to the low price for natural gas, the main competitor.

The data show that with electric power generation, each major continent has approximately the same percentage share of the installed capacity and energy produced, with the Americas and Asia having over 75% of the total. Whereas, with the direct-use figures, the percentages drop significantly from installed capacity to energy use for the Americas (26.8 to 13.9%) due to the high percentage of geothermal heat pumps with low
capacity factor for these units in the U.S. On the other hand, the percentages increased for the remainder of the world due to a lesser reliance on geothermal heat pumps and the greater number of operating hours per year for these units.

Worldwide growth of installed geothermal direct use

Geothermal Electric Power

Electric power has been produced from geothermal energy in 27 countries; however, Greece, Taiwan and Argentina have shut down their plants due to environmental and economic reasons. The worldwide installed capacity has the following distribution: 27% dry steam, 41% single flash, 20% double flash, 11% binary/combined cycle/hybrid, and 1% backpressure (Bertani, 2010).

Worldwide geothermal energy direct use

Direct Utilisation (including geothermal heat pumps)

The world direct utilisation of geothermal energy is difficult to determine, as there are many diverse uses of the energy and these are sometimes small and located in remote areas. Finding someone or even a group of people in a country who are knowledgeable on all the direct uses is difficult. In addition, even if the use can be determined, the flow rates and temperatures are usually not known or reported, thus the capacity and energy use can only be estimated. This is especially true of geothermal waters used for swimming pools, bathing and balneology.

The total installed capacity, reported at the end of 2009, for the world’s geothermal direct utilisation is 50 583 MWt, almost a two-fold increase over the 2005 data, growing at a compound rate of 12.3% annually. The total annual energy use is 438 071TJ (121 696 GWh), a 60% increase over 2005, growing at a compound rate of 11.0% annually. Compared to ten years ago the capacity increased 12.8%/yr and the use 8.7%/yr. Thus, it appears that the growth rate has increased slightly in recent years, despite the low cost of fossil fuels, economic downturns and other factors. It should, however, be noted that part of the growth from 2000 to the
present is due, in part, to better reporting, and includes some geothermal countries that were missed in previous reports. The capacity factor is an indication of the amount of use during the year (i.e. a factor of 1.00 would indicate the system is used at a maximum the entire year, and 0.5 would indicate using the system for 4 380 equivalent fullload hours per year). The worldwide average for the capacity factor is 0.27, down from 0.31 five years ago and 0.40 ten years ago. This decrease is due to the increased use of geothermal heat pumps that have a worldwide capacity factor of 0.19 in the heating mode.

The growing awareness and popularity of geothermal (ground-source) heat pumps had themost significant impact on the data. The annual energy use for these grew at a compound rate of 19.7% per year compared to five years ago, and 24.9% compared to ten years ago. The installed capacity grew 18.0% and 20.9% respectively. This is due, in part, to the ability of geothermal heat pumps to utilise groundwater or ground-coupled temperatures anywhere in the world.

The countries with the largest installed capacity were the USA, China, Sweden, Norway and Germany, accounting for about 63% of the installed capacity and the five countries with the largest annual energy use were: China, USA, Sweden, Turkey and Japan, accounting for 55% of the world use. Sweden, a new member of the ‘top-five’ obtained its position due to the country’s increased use of geothermal heat pumps. However, if considered in terms of the country’s land area or population, then the smaller countries dominate.

The ‘top-five’ then become Netherlands, Switzerland, Iceland, Norway and Sweden (TJ/area), and Iceland, Norway, Sweden, Denmark and Switzerland (TJ/population). The largest increases in geothermal energy use (TJ/yr) over the past five years are in the United Kingdom, Netherlands, Korea (Republic), Norway and
Iceland; and the largest increases in installed capacity (MWt) are in the United Kingdom, Korea (Republic), Ireland, Spain and Netherlands, due mostly to the increased use of geothermal heat pumps.

Categories of geothermal energy direct usage

In 1985, there were only 11 countries reporting an installed capacity of over 100 MWt. By 1990, this number had increased to 14, by 1995 to 15, by 2000 to 23 and by 2005 to 33. At present there are 36 countries reporting 100 MWt or more. In addition, six new countries, compared to 2005, now report some geothermal direct utilisation. In Fig. 11.10 district heating is estimated at 78% of total space heating energy use and 82% of the installed capacity. Snow melting represents the majority of the cooling/snow melting figure.

Installed geothermal electricity capacity

1 comment:

  1. This is especially true of geothermal waters used for swimming pools, bathing and balneology.
    geothermal flow centers