3.3 Supply Side: Renewables and Clean Fossil Fuel Technologies
Energy supply options that increase efficiency (the energy
efficiency of making energy carriers from primary energy sources), reduce
pollutant emissions and reduce emissions of greenhouse gases can contribute to
sustainable development objectives. The following are some of the opportunities:
a growing role for natural gas, promising advanced fossil and renewable energy
technologies for electric power generation, alternative electric-drive
technologies for motor vehicles, alternative fuels for transportation, and
expanding roles for fossil fuels in a greenhouse-gas-constrained world via fuel
decarbonisation and storage of the separated CO2.
Natural Gas: The contribution of natural gas to the
global energy economy has increased and the share of oil and coal has declined.
This trend is projected to continue as: 1) ultimately recoverable conventional
natural gas resources are expected to be at least as large as ultimately
recoverable conventional oil resources and natural gas reserves are increasing
faster through exploration than the reserves of oil; and 2) natural gas is
currently consumed at approximately 58% of the rate for oil. The shift to
natural gas is driven by its low cost in many parts of the world, its
convenience for shipping as liquefied natural gas (LNG) and the environmental
attractions of natural gas and LNG as a fuel. Natural gas has the lowest
specific CO2 emission rate of all fossil fuels and can, in general,
be used more efficiently than coal. Hence, as the role of natural gas expands at
the expense of coal and oil, greenhouse gas emissions will be reduced. However,
increasing natural gas consumption in many industrialised countries is currently
the main source of their rising CO2 emissions.
as the role of natural gas expands at the expense
of coal and oil, greenhouse gas emissions will be reduced
Advanced Technologies for Electric Power Generation: In
fuel-based electric power generation there are good prospects for routinely
achieving efficiencies of over 60-70% or more in the longer term, compared to
the present 30% world average. Large efficiency gains can also be achieved by
replacing the separate production of heat and power with combined heat and power
(CHP) technologies. Moreover, rapid progress is being made in the use of
renewable energy in power generation.
it is possible to raise the standard of living
without significantly increasing energy use
Thermal Power Generation: The natural gas-fired gas
turbine/steam turbine combined cycle has become the thermal power technology of
choice in regions having ready access to natural gas and LNG. This is because of
the low unit capital cost of the power plants, high thermodynamic efficiency
(now in the range 50-52%, but expected to reach 56% by 2000), low air pollutant
emissions (including nitrogen oxides) without the use of stack-gas controls and
low CO emissions (almost two-thirds less than for modern coal steam-electric
Since the feasibility of firing combined cycle power plants with
coal via the use of closely coupled coal gasifiers was successfully demonstrated
in the late 1980s, there has been much progress in commercialising the
coal-integrated gasifier/combined cycle (CIG/CC). This technology makes it
possible to adapt the continuing advances in gas turbine technology to coal with
pollutant emissions as low as for natural gas combined cycles. Efficiencies of
around 45% should be reached by 2000, at which time the technology is expected
to be fully cost-competitive with conventional coal steam-electric power with
flue gas desulphurisation.
Fuel Cells: Fuel cells, devices that convert fuel
directly into electricity without first burning it to produce heat, are now
beginning to enter CHP markets. Offering high thermodynamic efficiency, quiet
operation, zero or near-zero pollutant emissions and low maintenance
requirements, they will often be economically viable even in small-scale (100
kWe or less) CHP installations sited unobtrusively close to end-users, e.g., in
residential and commercial buildings. The technology will also facilitate
decentralised rural electrification.
Wind Power: A wind power industry was launched in the
early 1980s, largely as a result of government incentives to stimulate its
development. Costs have fallen dramatically. In the US, the cost of electricity
from wind in areas with good wind resources is about the same as for electricity
generated from coal. Globally, installed capacity continues to rise rapidly -
from 3,100 MWe in 1993 to 4,800 MWe in 1995. While deployed initially in
industrialised countries wind power is now growing rapidly in some developing
countries (e.g., wind capacity in India reached 650 MWe in early 1996). While
there are sometimes institutional barriers to its deployment in some areas (and
some concerns about visual intrusion), wind power is technologically ready to be
deployed as a major option for providing electricity.
wind power is technologically ready to be
deployed as a major option for providing electricity
Biomass: Biomass is used as fuel for steam turbine-based
CHP generation in the forest-product and agricultural industries of several
countries. The biomass used as fuel consists mainly of the residues of the
primary products of these industries. There is also a growing trend to co-firing
coal-fired power plants with supplemental biomass inputs. In developing
countries, there is large scope for efficiency improvements in the use of
biomass for energy in industry and growing interest in introducing modern
steam-turbine CHP technology (e.g., in the cane sugar industry).
An advanced technology that could make it possible for
electricity derived from plantation biomass to compete with coal in power
generation is the biomass integrated gasifier/combined cycle (BIG/CC). In
addition to plantation biomass, less costly biomass residues can be used.
Although BIG/CC technology is not as advanced as coal integrated
gasifier/combined cycle (CIG/CC) technology, several demonstration projects are
under way. Catching up might not take long because: 1) much of what has been
learned in developing the CIG/CC is readily transferable to BIG/CC technology;
2) biomass is in some ways a more promising feedstock than coal for gasification
(e.g., it contains very little sulphur and is much more reactive than coal); and
3) BIG/CC would facilitate decentralised rural electrification and
industrialisation and thereby promote rural development (a potentially powerful
market driver). Moreover, the modest scale of BIG/CC power plants relative to
conventional fossil fuel and nuclear plants facilitate financing and
cost-cutting as a result of learning-by-doing.
advanced technology in bioenergy would facilitate
decentralised rural electrification and thereby promote rural
Large scale biomass development also poses challenges to
biodiversity, land availability, water resources and local pollution which need
to be carefully addressed.
Photovoltaic Power: Worldwide sales of photovoltaic (PV)
modules have increased from 35 peak megawatts/year (35 MWp/year) in 1988, to 83
MWp/year in 1995, with production expected to be 91-93 MWp/year in 1996. So far,
most applications have been for a variety of consumer electronic and other niche
markets, but both stand-alone and grid-connected electric-power applications are
becoming increasingly important applications of PV technology.
PV technology is now cost-effective in small,
stand alone and some grid-connected applications
PV technology is being successfully deployed in small-scale,
stand-alone power applications remote from utility grids. Decentralised
rural-electric applications, largely for domestic lighting, refrigeration and
educational purposes, make it possible to serve modest household lighting and
other rural electric needs while avoiding the economic inefficiencies of
bringing centralised power supplies to these customers in remote areas. However,
stand-alone PV systems have to compete in biomass-rich regions with
biomass-based community-scale electricity generation serving households.
PV technology is now also cost-effective in some high-value,
grid-connected applications where PV units are sited near users.
Central station PV power plants, which offer opportunities for
bringing costs down quickly, are currently being planned in Hawaii and India.
Solar Thermal Electric Power: High-temperature solar
thermal-electric technologies use mirrors or lenses to concentrate the
suns rays onto a receiver where the solar heat is transferred to a working
fluid that drives a conventional electric power-conversion system. This
technology is rapidly becoming cost-effective, first in hybrid power plants
integrating solar thermal and fossil-fuel fired power generation.
Some 354 MWe of solar thermal capacity based on the
use of parabolic trough collectors, supplemented by gas-fired auxiliary boilers,
was built in California from 1984-91, during which time the unit capital cost
was reduced by half. The company that built the plants went bankrupt in 1991,
when government commercialisation incentives were suddenly withdrawn. Plans are
now underway to revive the technology with hybrid solar thermal/gas
turbine-steam turbine combined cycle technologies as a transitional strategy for
advancing solar technology while fossil fuel prices are low.
Power Systems: Large-scale adoption of renewable electric
technologies will require that they be connected to electric utility grids.
Intermittent solar and wind power plants can be managed by a combination of new
load-management techniques (e.g., using a time-varying electricity price to
induce load shifting); backing up the intermittent renewables with an
appropriate mix of dispatchable generating capacity; using interconnecting grid
systems for transferring electricity over large distances to cope with some of
the daily variations of wind and solar energy; and energy storage (mechanical,
electrochemical, thermal or other).
Hydropower plants allow prompt regulation and can back up
intermittent energy generators, as can some types of thermal power plants. The
ideal thermal complements to intermittent renewable energy plants on grid
systems are plants characterised by low unit capital cost (so they can be
operated cost-effectively at low capacity factor) and fast response times (so
they can adjust to rapid changes in intermittent supply output). Natural
gas-fired gas turbines and combined cycles satisfy these criteria, but fossil
and nuclear steam-electric plants do not. Thus, natural gas and renewable
electric systems are complementary supply strategies, while nuclear and
intermittent renewables are competitors where there is high grid-penetration
Electric-Drive Vehicles for Transportation:
Electric-drive vehicles offer both the potential for dramatic reductions in air
pollutant emissions and marked improvements in fuel economy. The common
characteristic of these technologies is that they employ electric motors to
drive the wheels and extract energy from the cars motion via
regenerative braking when the vehicle slows down.
alternative clean transport fuels are likely to
be especially important in developing countries
Batery-powered electric vehicles are attractive options for
short-range (e.g., commuter) applications. An option offering wider market
potential is a hybrid electric drive vehicle that couples a small internal
combustion engine and electric generator to provide baseload electric
power with a small battery, ultracapacitor or flywheel, as a peaking
power device. In automotive application, at least a two-fold gain in
energy efficiency is feasible via the use of such hybrids.
Fuel cells are also attractive options for electric-drive
vehicles. Current interest is focused on the proton exchange membrane fuel cells
(PEMFCs). In mass production, vehicles powered by PEMFCs would have much lower
costs and much longer ranges between refuelling than battery-powered electric
vehicles. Potentially, the PEMFC can compete with the petroleum-fuelled internal
combustion engine in automotive applications, while providing transport services
at a two- to three-fold higher energy efficiency and emitting zero or near-zero
local air pollution.
Before fuel cells are used in automobiles they will most likely
be deployed in buses, trains and small utility vehicles such as
3-wheeler taxis, common in many developing countries. In economies
where new power stations would need to be built to provide extra capacity for
high cost railway electrification, fuel-cell locomotives provide an attractive
Clean Fuels for Transportation: There is growing interest
in alternative transportation fuels because of difficulties of meeting air
quality goals with petroleum-derived fuels and the longer term need for
alternatives to oil in transportation (perhaps before the end of the first
quarter of the next century). Alternative clean transport fuels are likely to be
especially important in developing countries. This assessment is based on the
difficulties of meeting air quality goals with tailpipe emission control
technologies installed on petroleum-fired internal combustion engine vehicles in
the densely populated megacities of the developing world.
Some of the alternatives that merit consideration are
reformulated gasoline, compressed natural gas, alcohols (methanol and ethanol),
synthetic middle distillates, dimethyl ether and hydrogen.
Efforts to produce biofuels for transport have focused on
ethanol from maize, wheat, sugar cane and vegetable oils such as rape-seed oil.
All these traditional biomass-derived transport fuels are uneconomic at present.
However, there are good prospects for making sugar-cane-derived ethanol
competitive at the present low world oil price if electricity is cogenerated
from cane residues using BIG/CC technology along with ethanol from cane juice.
In contrast, prospects are poor for making ethanol economically from grain.
Advanced biofuels derived from low-cost woody biomass could
offer higher energy yields at lower cost and with lower environmental impacts
than most traditional biofuels. The advanced biofuel that has received the most
attention is ethanol derived from wood via enzymatic hydrolysis. Other options
include methanol and hydrogen derived via thermochemical gasification of
biomass. The potential for displacing gasoline used in internal combustion
engine cars with biomass-derived fuels used in fuel cell cars is much higher
than using wood-derived ethanol in internal combustion engine cars, as fuel cell
cars are more energy-efficient.
advanced biofuels could offer higher energy
yields at lower cost and with lower environmental impacts than most traditional
Hydrogen offers good prospects for simultaneously dealing with
the multiple challenges facing the energy system in the 21st century. Hydrogen
is a clean, versatile and easy-to-use energy carrier. It can be used safely if
systems are designed to respect its unique physical and chemical properties, as
is necessary in the use of any fuel. It can be derived from a variety of primary
energy sources. Even if derived from fossil fuels, hydrogen used in fuel cell
vehicles would emit significantly lower lifecycle CO2 than gasoline
internal combustion vehicles, because fuel cell vehicles are much more
Decarbonisation of Fuels and CO2
Storage: It is feasible to remove CO2 from fossil fuel
power plant stack gases. This brute force approach reduces the conversion
efficiency and increases the cost of electricity substantially. The less costly
approach involves introducing technologies that give a high value to hydrogen
(e.g., low-temperature fuel cells used for transport and distributed CHP
applications). The reason is that hydrogen production from coal, oil and gas
involves generating a stream of relatively pure CO2 as a
free byproduct (i.e., the cost of separating the CO2 from
the hydrogen is part of the production cost, and not an added expense). The
potential for storing this CO underground at low cost in depleted oil and gas
fields and deep acquifers is