Energy sources that do not directly increase carbon dioxide emissions during…

CONCEPT

Carbon emissions can be assessed at the point where electricity is generated: a source that produces electricity without burning a carbon-based fuel does not directly release carbon dioxide during operation.

This operational-emissions criterion is different from full life-cycle emissions associated with construction, mining, fuel processing, or manufacturing.

APPLICATION

1. Solar cells convert sunlight directly into electrical energy through the photovoltaic effect; no fuel is combusted while electricity is generated.

2. Windmills convert the kinetic energy of moving air into mechanical rotation and then electricity; no fuel is combusted at the generation stage.

3. Nuclear power plants obtain heat from nuclear fission to make steam and generate electricity; an operating reactor does not obtain this energy by burning a carbon-based fuel.

CROSS-CHECK AND CONTRAST

• Coal-, oil-, and gas-fired plants release carbon dioxide when their carbon-based fuels are oxidized during combustion.

• Solar cells, windmills, and nuclear power plants instead use sunlight, moving air, and nuclear fission, respectively, so all three avoid direct carbon dioxide emissions from fuel combustion during operation.

RESULT

Thus, more than one listed source—indeed solar cells, windmills, and nuclear power plants—meets the stated operational criterion.