Environmental Engineering Reference
In-Depth Information
Old renewables
These are already big contributors to the global energy balance, but for
various reasons there is no widespread desire to increase them. One of
these old renewables is traditional biomass - the firewood, animal dung
and farm waste that has been gathered by rural households since time
immemorial for cooking and heating. This is thought to amount to some
seven percent of the total global energy mix. But smoke from this kind of
biomass can be a killer in unventilated kitchens. Firewood collection is
also fundamentally unsustainable when it leads to deforestation.
The other main old renewable is hydroelectric power, which is by far
the most significant renewable source of world electricity generation,
accounting for much as sixteen percent of it. But, with the exception of
Asia (see hydropower section), big hydroelectric dams have fallen out
of favour, because of the displacement of populations and disruption of
fish stocks they generally cause. Still in favour are smaller hydro projects,
especially run-of-the-river projects, which are capable of funnelling some
water into turbines without blocking or damming whole rivers.
New renewables
Energy sources that fall into this category include solar, wind, tidal and
wave power, and the environmentally controlled cultivation and use of
biomass for power and heat, and of biofuels for transport. The contribu-
tion of these new renewables is tiny - around 0.2 percent of global pri-
mary energy supply. In fact, in the case of windmills and a few tidal power
schemes, these renewables are not new and indeed go back centuries. But
what is new about them all is the new enthusiasm to develop them.
Renewable energy 2006
(inc. hydropower; exc. traditional biomass)
Contribution to total energy demand
7%
Contribution to total electricity demand
18%
Contribution to total heat demand
6%
Contribution to total transport demand
1%
Source: International Energy Agency,
World Energy Outlook 2008
