Environmental Engineering Reference
In-Depth Information
sources in the current marketplace without state subsidies. There are three main reasons for
this: energy return on investment (EROI), capacity and infrastructure.
The EROI of a given energy source is a good indicator of its economic viability (see
Section 6.15 ) . Modern economies require energy sources with an EROI of five or above
(i.e., each unit of energy invested will yield five or more units). As things currently stand,
the EROIs of all renewable sources except hydropower and solar thermal lag behind those
of fossil fuels. However, the EROI of fossil fuels is likely to rise as easily accessible oil and
gas fields dwindle, and utilities are forced to pay the costs of reducing pollution (Inman
2013a , 2013b ) .
Most renewable technologies have a low capacity factor. This is because the energy
sources they rely on are intermittent. Nuclear power plants are the most efficient with
capacity factors above 90 per cent. By stark contrast, a PV plant installed in central Spain,
the sunniest place in Europe, barely reaches 20 per cent capacity factor. A well-located
inshore wind turbine may achieve capacity of 25 per cent to 30 per cent, or 40 per cent
offshore (see Section 4.1 , Table 4.1 ).
The issue of low capacity is also linked to the need for new power infrastructure. To
guarantee a steady supply of electricity, renewable plants need to be widely dispersed
on a continental scale. This would require a significant extension of the power grid,
an expensive and environmentally challenging undertaking that would encounter many
NIMBY objections. The current grids are mostly unsuited to large-scale use of renewables.
They were designed to carry power from a centralized power station to millions of diffuse
consumers. The scenario proposed by Jacobson and Delucchi would turn this model
around: instead, power would be supplied by many decentralised small plants. This would
entail a complete rethinking of the grid technology and many additional high-voltage
transmission lines to link production and consumption sites.
Germany has an average insolation of roughly 1,000 kilowatt-hours per square metre
per year, lower than southern European countries such as Spain, Italy, and Greece
(1,400-1,900 kilowatt-hour per square metre per year) and much lower than Arizona,
Egypt, or central Australia (2,000-2,300 kilowatt-hour per square metre per year). So why
has Germany taken the lead in solar PV over the last two decades? According to Smil, the
answer is simple: “It happened for the best reason there is in politics: money. Welcome to
the world of new renewable energies, where the subsidies rule and consumers pay” ( 2012 ) .
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