All of the reasons mentioned are considered obstacles to producing cars that run on hydrogen fuel cells.

All of the reasons mentioned are considered obstacles to producing cars that run on hydrogen fuel cells.

All of the reasons mentioned are considered obstacles to producing cars that run on hydrogen fuel cells.

As of 2014, the very best experimental units could convert more than 40% of light energy to electricity; ordinary commercial units are in the range of 5% to 20%. 

As of 2014, the very best experimental units could convert more than 40% of light energy to electricity; ordinary commercial units are in the range of 5% to 20%. 

As of 2014, the very best experimental units could convert more than 40% of light energy to electricity; ordinary commercial units are in the range of 5% to 20%. 

A typical incandescent lamp (traditional light bulb) that consumes 60 watts of power produces around 800 lumens. A compact fluorescent lamp emits the same amount of light while using only 13 watts. And an LED lamp consumes only 10 watts to give off the same 800 lumens.

A typical incandescent lamp (traditional light bulb) that consumes 60 watts of power produces around 800 lumens. A compact fluorescent lamp emits the same amount of light while using only 13 watts. And an LED lamp consumes only 10 watts to give off the same 800 lumens.

A typical incandescent lamp (traditional light bulb) that consumes 60 watts of power produces around 800 lumens. A compact fluorescent lamp emits the same amount of light while using only 13 watts. And an LED lamp consumes only 10 watts to give off the same 800 lumens.

Electricity is a secondary energy source because it can only be produced from the use of primary energy sources such as coal, natural gas, or nuclear reactions.

Electricity is a secondary energy source because it can only be produced from the use of primary energy sources such as coal, natural gas, or nuclear reactions.

Electricity is a secondary energy source because it can only be produced from the use of primary energy sources such as coal, natural gas, or nuclear reactions.

Electricity is a secondary energy source because it can only be produced from the use of primary energy sources such as coal, natural gas, or nuclear reactions.

As of 2014, total world consumption was approximately 92 million barrels per day, about 19 million or 21% of which were used by the United States.

As of 2014, total world consumption was approximately 92 million barrels per day, about 19 million or 21% of which were used by the United States.

As of 2014, total world consumption was approximately 92 million barrels per day, about 19 million or 21% of which were used by the United States.

Load-following and peaker plants, demand-response and energy storage are all ways that grid operators can adjust generation to meet demand.

Load-following and peaker plants, demand-response and energy storage are all ways that grid operators can adjust generation to meet demand.

Load-following and peaker plants, demand-response and energy storage are all ways that grid operators can adjust generation to meet demand.

Load-following and peaker plants, demand-response and energy storage are all ways that grid operators can adjust generation to meet demand.

The ampere, or amp, is the most commonly used measurement for electric current.

The ampere, or amp, is the most commonly used measurement for electric current.

The ampere, or amp, is the most commonly used measurement for electric current.

Most direct uses of primary energy are limited to generating heat and motion. Electricity, by contrast, is extremely versatile, with a wide range of complex applications. 

Most direct uses of primary energy are limited to generating heat and motion. Electricity, by contrast, is extremely versatile, with a wide range of complex applications. 

Biofuels contain carbon and although they may burn “cleaner” than oil-derived fuels, they do not avoid generating carbon dioxide emissions.