Assertion: fuel cell | /r/HasProperty | useful
Facets:
value: on airliners
type: LOCATION
value: in certain military applications
type: LOCATION
value: very
type: DEGREE
Source sentences:
text: Fuel cells are very useful as power sources in remote locations, such as spacecraft, remote weather stations, large parks, communications centers, rural locations including research stations, and in certain military applications.
text: Before fuel cells will be useful on airliners, however, engineers must find a way to increase their power density.