Background to Sustainable Cities - Theme Cities: Solutions for Urban Problems - page 183

Table 5﻽2 (continued)
d) The greatest advance in utilizing geo-thermal energy sources has been made in Iceland
where geo-thermal power is now used extensively, with over 80 % of dwellings in urban areas
heated from this singular geological area. Until recently it was assumed that only limited
areas on earth had the ability to use geothermal resources, places located where tectonic plates
collide, or in areas of thin crust, places that had the capability of exploiting the heat from the
earth's interior. However research by a group at M.I.T. led by J. W. Tester (Tester and Anderson
2007 ) has claimed that there are far more economically feasible geothermal sources available
in the United States This is due to the use of new drilling techniques and rock fracturing at
depths well below 5000 ft., so the source could supply even high demand time or base-load
electricity, at least in larger settlements. Despite this potential, the development of this resource
is still in infancy, except in a few areas.
the recognition that wind still only supplies 4.4 % of the electricity energy in the
United States as a whole, which is a long way below Denmark's level. So although
it is undeniable that there are major increases in the growth of renewables, they
have a long way to go in most countries before catching up with fossil fuel sources,
a problem made more difficult because of the predicted large expansion in energy
demands shown in Table 5.1 .
The prospect of increasing sustainability in energy sources at a world level
has also become more difficult given the rapid industrialization and hence energy
growth of such a huge country as China, which has already been shown to have ma-
jor pollution problems. So even though China and other countries may be installing
solar panels and wind turbines at an great rate, the fastest pace in the world, its huge
population and increasing energy demands means it will still be heavily dependent
on fossil fuels, especially coal, for the next 20 years. Moreover many of the wind
farms in the west of the country need long transmission lines to the main consum-
ers of electricity in cities. They are also limited because they have lower capacity
levels at 23 % due to longer periods without wind than in most countries (Cyranoski
2009 ). All these issues mean that the proportion of world energy from renewables
at a world scale is still predicted to be relatively small compared to other sources,
ranging from 14 to 26 % in 2035 dependent on the scenarios adopted, as shown
by the International Energy Authority estimates in Table 5.1 . This does not deny
that considerable progress is being achieved in some places, rather that the rate of
growth does not seem sufficient to even make a world with 50 % energy levels from
sustainable sources by mid-century.
The limited predicted contribution of renewables relative to fossil fuel sources
leads to the question of why such renewable sources are not likely to make larger
contribution. Eight general problems of renewable energy expansion need to be ad-
dressed before renewable sources can grow to outpace fossil fuel sources at a world
scale. The first is the higher costs of all renewable options, although some of these
are coming down as technology improves and with larger production runs to create
economies of scale. Indeed, power generated from solar cells and wind powerare
becoming close to parity in price with fossil sources in some countries because of
technological breakthroughs and high volume production in solar cells and wind
turbines. They would be equivalent if the costs of the negative externalities of the