In around 500 words, describe the role, either for good or for bad, of the following in achieving energy sustainability:

wind, solar, hydro, and wave-powered electricity,

cars that run on hydrogen fuel,

electric cars,

improvements in residential energy efficiency, and

government policies that mandate new technologies to improve motor fuel efficiency

Renewable Energy and Electricity (Updated May 2019)

There is widespread popular support for using renewable energy, particularly solar and wind energy, which provide electricity without giving rise to any carbon dioxide emissions.

Harnessing these for electricity depends on the cost and efficiency of the technology, which is constantly improving, thus reducing costs per peak kilowatt, and per kWh at the source.

Utilising electricity from solar and wind in a grid becomes problematical at high levels for complex but now well-demonstrated reasons. Supply does not correspond with demand.

Back-up generating capacity is required due to the intermittent nature of solar and wind. System costs escalate with increasing proportion of variable renewables.

Renewable Energy and Electricity (Updated May 2019)

There is widespread popular support for using renewable energy, particularly solar and wind energy, which provide electricity without giving rise to any carbon dioxide emissions.

Harnessing these for electricity depends on the cost and efficiency of the technology, which is constantly improving, thus reducing costs per peak kilowatt, and per kWh at the source.

Utilising electricity from solar and wind in a grid becomes problematical at high levels for complex but now well-demonstrated reasons. Supply does not correspond with demand.

Back-up generating capacity is required due to the intermittent nature of solar and wind. System costs escalate with increasing proportion of variable renewables.