The Cost of Renewable Power: A Survey of Recent Estimates - Green Energy and Efficiency: An Economic Perspective - page 253

cannot be too large. Consequently, economies of scale can only be obtained at low
or very low levels. No signi cant improvements are expected in future costs for

technologies that have already achieved maturity, such as biomass. There are,
however, a large number of designs that are being researched at the pre-commercial
level and in R&D laboratories that might in future reach the market and become
competitive.
Given its dispatchability, the prospects for future deployment of the technology
as a power generating source are good, especially as a support technology in the
deployment and high penetration rates of other intermittent renewable power
sources. The technology may also become an excellent support for the generated-
distribution mode of production and consumption of electricity at

local level,

particularly when its heating capabilities are taken into account.
Summarising, there is a great diversity of biomass power techniques and feed-
stocks, but only three have reached maturity and commercial competitiveness:
stoker-boiler combustion, CHP generation and co-

rst of these is by far
the most common. The feedstock may be agricultural, forestry or municipal solid
waste, or dedicated crops. In this last case the costs increase appreciably. In less
developed countries costs can be very low, but this may mask less stringent controls
on gas emissions. Biomass power generation is a dispatchable technology, which
may make it especially attractive as a back-up and support at high penetration rates
for other intermittent renewable power sources. Combined with heat generation,
this enhances its potential for playing an important role in a context of increasingly
high renewable penetration rates and a new mode of distributed generation and
consumption of electricity at local level. All these factors make the future prospects
for its deployment good.

ring. The

3.6 Geothermal Power

The term “ geothermal ” is usually used to describe the energy stored close beneath

the Earth s surface (at depths of as far as 3,000 or 4,000 m) in the form of steam, hot

rocks and superheated water (typically above 180

'

° ). There are two basic technol-

ogies for generating power: (a) , based on steam or high temperature water

converted into steam by dropping the pressure; and (b)

' ashing '

, where the tem-
perature is lower and some additional treatment is required to generate steam from a
liquid at a low boiling point for subsequent use in a turbine. The latter is more
expensive [ 18 ].
Finding a place with good resources is generally a costly, time consuming
process. Once a site is found the costs of drilling equipment, the actual drilling of
the production wells and other capital expenses related to the installation of the
system are usually high. These initial costs are not expected to come down since
this is a mature technology. Indeed, in the last decade they have risen around 60 %
due to increased drilling activity searching for other fossil energy sources. Geo-
thermal energy can still be quite competitive on good sites, although it is not

“ binary ”