Biomedical Engineering Reference
In-Depth Information
planet and its surface, drives a continuous conduction of thermal energy in the form of heat
from the core to the surface.
From hot springs, geothermal energy has been used for bathing since Paleolithic times
and for space heating since ancient Roman times, but it is now better known for elec-
tricity generation. Worldwide, about 10,715 MWof geothermal power is online in 24 coun-
tries. An additional 28 GW of direct geothermal heating capacity is installed for district
heating,
space heating,
spas,
industrial processes, desalination, and agricultural
applications.
Geothermal energy is not protected. Taking geothermal power has very low cost.
Geothermal energy is reliable, and has very low gas emissions, but has historically been
limited to areas near tectonic plate boundaries. Unfortunately, recent technological advances
have dramatically expanded the range and size of viable resources, especially for applica-
tions such as home heating, opening a potential for widespread exploitation. Geothermal
wells release GHGs trapped deep within the earth, but these emissions are much lower
per energy unit than those of fossil fuels. As a result, geothermal power was viewed to be
of potential to help in a short-term scale mitigates global warming if widely deployed in
place of fossil fuels.
The Earth's geothermal resources are theoretically vast. There is no comparison between
geothermal and fossil energy in terms of storage. However, geothermal energy is still finite,
although the time scale to deplete geothermal resources is very long. Removing thermal
energy from earth core cannot be reversed. Once the earth's core was cooled, the very
ecosystem we enjoy today would not be there. Therefore, geothermal energy is not a sustain-
able energy for humanity to actively exploit. Depleting geothermal energy is even more
dangerous than utilizing fossil energy.
15.8. SUMMARY
Sustainability is the capacity to endure in ecological terms. In more general scientific term,
sustainability is the ability to continue without termination. Therefore, a sustainable system
is one that has a “stable” “end” state. Monotonously increasing or decreasing of a given phys-
ical parameter is an indication of the system is not sustainable. In bioprocesses, sustainability
is compatible with steady state.
The Sun's energy powers the entire ecosystem on earth: water cycle and biomass cycle.
Energy stored by plants (primary producers) during photosynthesis, passes through the
food chain to other organisms to ultimately power all living processes. Since the industrial
revolution, the concentrated energy of the Sun stored in fossilized plants as fossil fuels has
been a major driver of technology which, in turn, has been the source of both economic
and political power. A discussion on sustainability must involve the chain of energy from
the Sun to the two major cycles on the planet.
The water cycle provides opportunity for hydroelectric power development. Hydroelec-
tricity eliminates the flue gas emissions from fossil fuel combustion, including pollutants
such as sulfur dioxide, nitric oxide, carbon monoxide, dust, and mercury in the coal. Hydro-
electricity also avoids the hazards of coal mining and the indirect health effects of coal emis-
sions. Compared to nuclear power, hydroelectricity generates no nuclear waste, has none of
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