| Increase use of Renewable Energy & Reduction of GHG
Emissions Renewable energy resources include
sunlight and energy derived from the conversion of sunlight in the
Earth’s ecosphere. These include wind energy, biomass (especially
residues from commercial activities), and the hydro potential of flowing
water. A broad evolving menu of renewable energy options is available
for application, both for large-scale grid-connected applications and
for off-grid use. Many are fully commercial and field-proven, and many
applications are cost-effective on an annualised basis, compared with
fossil fuel energy. In other cases, the energy services provided by
renewable energy options may be more expensive than fossil-fuel options,
but their higher reliability, longevity, and ease of maintenance may
make them the preferred option. Relevant technologies include wind
electric power, photovoltaics (solar electric power), solar heating,
small hydropower, and biomass energy conversion systems for production
of heat, electricity, or both.
The world has vast and virtually
inexhaustible renewable energy resources. The solar energy falling each
year on the Earth’s land surface amounts to 800,000 EJ, or nearly 2,000
times the 425 EJ of current annual global energy use.
Using just one percent of the world’s
land surface that is not farmed or under forests and woodlands could tap
5,000 EJ per year. The heat that could theoretically be tapped each year
from the top 5 km of the earth’s crust is a massive 140 million EJ, of
which a sizeable 5,000 EJ per year could become economic within the next
40-50 years.
Theoretical resources for other
renewables are more modest, yet in the same range as today’s total
global energy use. The world’s hydroelectricity potential is estimated
at 40,500 TWh per year, or nearly 490 EJ per year in terms of primary
energy. The equivalent figure for wind energy is 231 EJ. This assumes
that no more than 4 percent of the global land area having adequate wind
speeds is used for wind farms. The theoretical potential for biomass
energy is more controversial, as it depends both on land availability
and on achievable biomass yields on this land. Various studies have
suggested that by 2050 biomass might contribute an annual 100 to 280 EJ
to global energy supplies. Assuming a biomass yield of 10 dry tons per
hectare per year, as used in most of these studies, 500 million to 1,400
million hectare of land would have to be devoted to biomass energy
crops. Today, 1,500 million hectares are used globally for cropland and
3,400 million hectares for permanent pasture.
|
