Environmental Engineering Reference
In-Depth Information
Chapter 6
Geothermal Energy
Toshiyuki Hashida
Abstract
This chapter focuses on a source of renewable energy which could be
very significant in Japan and similar geologically active zones. Geothermal energy
has the advantage of heat and electricity with minimal environmental impact.
Potentially the available energy exceeds human needs but there remain technical
barriers to its economic exploitation on a larger scale away from the most intense
sources near tectonic plate boundaries. The role of drilling and fracturing to create
Enhanced (engineered) Geothermal Systems (EGS) is described together with the
relevant factors for the design of geothermal energy extraction systems. The role of
modelling to simulate the effects of fracturing to create flow pathways for heated
water is also described.
Keywords
Geothermal energy
·
Hot dry rock
·
EGS
·
Hydraulic stimulation
6.1
Geothermal Energy: Current and Future
Geothermal energy exploits the heat from the Earth's crust to generate electricity
or provide heat directly e.g. for district heating, hot water, horticulture etc. Ground
source heat pumps can also be classified as geothermal energy although not the sub-
ject of this chapter. According to the International Energy Agency (IEA
2010a
), in-
stalled capacity of geothermal energy at the end of 2009 was 10.7 gigawatts (GWe)
for electricity generation and 50.6 GWth for direct use as heat. Most recent esti-
mates suggest modest growth in supply, with 11,224 GW of electricity generated in
24 countries in 2012 (GEA
2012
).
Currently, geothermal energy is exploited most in the countries shown in
Table
6.1
. A significant proportion of electricity is generated from geothermal in
Iceland (25 %), El Salvador (22 %), Kenya and the Philippines (17 % each), and
Costa Rica (13 %). In absolute figures, the United States produces the most geo-
thermal electricity: 16,603 GWh from an installed capacity of 3093 MWe. Japan's
geothermal usage is in 8th position globally for electricity and 5th for heat.
