Self-study
Geothermal power plants produce power using heat from underground reservoirs of hot water or steam heated by the surrounding rock. ██ ███ ███████ █████ ██ ███ █████ █████ ████ ███████████ ███ █████ ███ █████ ███ █████████ ██ ███████ ██ █████████ ██████████ █████ ██████ ███████ █████ ████ ████████████ ████ █████████████ ██████ ████ █████ ███████ ████████ █████████ ███████ ████ ██ ███ ████ ██████ ██████████ █████ ████ ██████████ █████ ██████ ████ ██ █████████ ██ ████ ██████
Summary
The advocates claim that in the near future, in most areas, it will be possible to get cost-effective power from geothermal power plants.
We don’t get any direct support for the advocates’ claim, but we are told that in areas of the world in which underground hot water and steam can be reached by drilling, geothermal power plants produce power more cost effectively than convention power plants do.
Notable Assumptions
Why should we believe that “in the near future” geothermal plants can provide economical power in “most areas”? It probably has something to do with the fact that in areas where underground hot water and steam can be reached by drilling, geothermal plants are more economical than conventional plants.
If, in the near future, most areas will allow for underground hot water and steam to be reached by drilling, then the advocates’ claim is strengthened.
7.
Which one of the following, ██ █████ ████ █████ ██ ███████ ███ ██████████ ███████████
a
Conventional power plants, ██████ ██████████ █████ ███████ ███████ █████ ███████ ██ ██████████ ████ ███ ████
(A) doesn’t help us make any claims about what will happen in the future. We still have no reason to believe the advocates’ prediction about the future.
b
A typical geothermal █████ █████ ████████ ██ █████ ██ ████ ██████ ██ █ ███████ ████████████ █████ ██████
(B) doesn’t help us make any claims about the future. We still have no reason to believe the advocates’ prediction about the future.
c
The high start-up █████ ██ ██████████ █████ ██████ ███████████ █████ ████████████ ████ ██ █████████ █████ ████ ███ ████ ██████████ ████ ████████████ █████ ██████ ██ ███ ████ ████
(C) provides a reason to think that geothermal power plants won’t be built. This doesn’t support a prediction that power from geothermal power plants will be available in most areas.
d
Advanced drilling technology ██ █████ █████████ ████ ████ ████ ████ ██ ████ ████████ ███ ██████████ ██ █████ █████ ████ █████ ██████ ████ ██ ██ █████████ ████████ ██ ██████
(D) provides a reason to think that in the future, power from geothermal power plants will be more available. If future drills allow deeper and more economical drilling, then we have reason to think geothermal power plants will be viable in a larger range of areas, because they’ll be able to access underground hot water and steam in places that they currently can’t.
e
Recent research has ███ ██ ███████████ ████ █████ █████████████ █████ ██████████ █████ ███ ██████ ███ █████ ██ █████ ███████
(E) gives us reason to think that productions costs for almost all power plants will go down in the future. But that doesn’t help us support a prediction that geothermal power plants will be available in most areas in the near future. The current constraint on these power plants isn’t necessarily their production costs, but rather the ability to reach underground hot water and steam through drilling.