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Fuel
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Advantages
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Disadvantages
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Comments
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Coal
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Low cost
Plentiful: we will not run out of easily mined coal in the
next few decades. It has been believed that the world's coal reserves
would last a century or more, but some recent research has indicated that
this was optimistic.
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Not sustainable
Requires around 1.7 million litres of fresh water for each gigawatt-hour
of electricity generated.
Produces more greenhouse
carbon dioxide (CO2) per Watt-hour
of energy than any other generation method.
The methods of mining coal can be very destructive,
although responsible coal miners do a remarkably good job of
restoring the land after the coal has been mined out.
Very large quantities of ash have to be disposed of and
a lot of smoke is produced.
The air pollution from the
burning of coal causes millions of human deaths world-wide each year.
In modern, Western, power stations most of the particulates, including smoke,
are separated from the waste gas stream and disposed of with the ash.
Coal contains substances such as sulfur, arsenic, selenium, mercury and
the radioactive elements uranium, thorium, radium and radon (see
USGS).
When the coal is mined and burned these substances can be released into the
environment.
Burned sulfur is one of the main causes of acid rain, but most modern Western
coal-fired power stations remove most of the sulfur oxides from the released
gasses.
War time –
For maximum efficiency coal fired power stations must be big. They therefore
present a desirable target for enemy attack.
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Coal has an 'unfair' advantage over 'cleaner' forms of power generation in
that the power station operators do not have to pay for the damage that they
are doing to the atmosphere. See:
No level playing field.
A coal-fired power station generates a large amount of
energy in a relatively small area compared to most renewable methods.
However, when all the land
required for mining and disposal of ash is taken into account coal
does not have any space advantage over several sustainable methods.
The misleading term 'clean coal' is sometimes used to refer to coal-fired
power stations that efficiently extract substances like sulfur from the
coal, either before or after burning. It is impossible to burn coal without
producing carbon dioxide, so all coal-fired power stations are dirty in this
sense. However, it is possible to
dispose of (sequestrate) the carbon dioxide so that it is not released into
the atmosphere for a long time. As of the time of
writing (Feb. 2006) this has not been done for a commercial scale power
station.
It seems that some coal-fired power stations that are not economically
viable are being kept in operation because decommissioning and cleaning up
would be more expensive than keeping them going.
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Fuel
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Advantages
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Disadvantages
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Comments
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Natural gas
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Low cost
Generators are very compact
Produces less CO2 than oil and much less than coal
Requires much less water than coal fired power stations
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Not sustainable
Produces
carbon dioxide.
(CO2), which is an important
greenhouse gas.
The world's natural gas reserves are limited, but not so limited as oil
reserves.
Seismic surveys of the sea-bed cause death and injuries to marine species.
Leakage of methane to the atmosphere, very difficult to quantify, increases
the greenhouse effect.
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At the rate we are using natural gas our children will see the price rise so
much that it will no longer be economical as a fuel.
In a more far sighted world natural gas would be reserved for more valuable
uses than burning as fuel.
We are consuming our children's heritage.
Also see: No level playing field.
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Fuel
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Advantages
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Disadvantages
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Comments
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Oil
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Low cost
Generators are very compact.
Produces less CO2 than coal and requires much less water than
coal
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Not sustainable
Produces
carbon dioxide
(CO2), which is an important
greenhouse gas.
Requires a substantial amount of cooling water.
The world's oil reserves are limited.
Oil spills, especially at sea, cause severe pollution.
Some oils contain high levels of sulfur. See the note on
sulfur under coal, above.
The world's supply of oil is limited; see
Peak Oil.
Seismic surveys of the sea-bed cause death and injuries to marine species.
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At the rate we are using oil our children will see the price rise so
much that it will no longer be economical as a fuel.
In a more far sighted world oil would be reserved for more valuable
uses than burning as fuel.
We are consuming our children's heritage.
Also see: No level playing field.
Shale oil is oil that can be extracted from shale by mining a shale
that is saturated with oil, and roasting it at about 500 degrees
Celsius to extract the oil. For more detail see
Shale oil in 'Notes' on my page
Heating Efficiencies and Greenhouse.
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Technology
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Advantages
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Disadvantages
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Comments
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Biogas
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Uses a renewable fuel.
Consumes methane that might otherwise leak into the atmosphere and
increase the greenhouse effect, so the waste is converted into a less harmful
form at the same time and in the same operation; a win-win operation.
Biogas can also be used on a small scale, eg. a pig farm.
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Very limited in the quantity of electricity it can produce on
the global scale.
There is little or no control on the rate of gas production,
although the gas can, to some extent, be stored and used as required.
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The biogas that I am considering here is that produced from buried
organic waste, as in a land-fill rubbish dump, or from sewerage.
It is also possible to produce flamable gas from materials such as
wood.
It is non-polluting in that it does not produce any net increase
in atmospheric carbon dioxide so long
as the biological material being used is replaced sustainably.
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Technology
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Advantages
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Disadvantages
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Comments
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Biomass (including firewood)
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Uses a renewable fuel.
No net addition of carbon to the atmosphere (the CO2 released into the
atmosphere by burning one crop is taken out by growing the next).
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A large area of land is required for the production of the
fuel (eg. wood lot or cane field) per MW of power generated.
Because of the above point, this method can never generate
enough power to satisfy a major part of current demands.
Burns organic matter that might be better returned to the
land for soil improvement.
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Biomass includes firewood; see environmental aspects of burning
firewood on this site.
The sustainability of the production and replacement of the biomass is of
critical importance to the ethics of using biomass as a source of energy.
My page,
Energy Calculator calculates the relative costs of firewood
and several other fuels in terms of energy per dollar.
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Technology
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Advantages
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Disadvantages
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Comments
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Geothermal
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Sustainable
Relatively low cost for renewable energy, US$0.06 to $0.08/kWh.
Non-polluting;
little environmental impact since the steam would be released
to the atmosphere with or without the power generation.
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It can only be developed in selected volcanic areas, so it can
never be a major contributor to the world energy supply
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I have used 'geothermal' in relation to the capture and use of
more-or-less natural steam in volcanic areas; distinct from 'hot dry
rock', which is discussed elsewhere.
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Technology
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Advantages
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Disadvantages
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Comments
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Hot dry rock
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Compact; a large amount of electrical power can be produced by
a moderately sized station.
There are huge volumes of very hot rocks at depths of 5km or so.
The resource could not be significantly depleted in decades. In
human terms it is close to sustainable.
It could provide a large part of the worlds base-level electricity
supply.
Non-polluting
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While there have been some trial operations, the technology remains
unproven. The costs and technical problems with drilling to great
depths in very hot rocks are considerable.
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Also see geothermal above
A hot dry rock company in Australia:
Geodynamics.
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Technology
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Advantages
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Disadvantages
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Comments
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Hydro
(falling water)
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Compact; a large amount of electrical power can be produced by
a moderately sized station.
Sustainable
Once established it is fairly environmentally benign
Run-of-river hydro stations do not require large dams and are less disruptive
of riverine ecosystems that hydro using large dams
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The building of dams is usually environmentally destructive –
river valleys are important ecosystems;
it often requires great changes in many peoples' life styles; river valleys
are often fertile and densely populated.
Fermenting vegetation in hydro dams releases the greenhouse gas methane to
the atmosphere.
The water released from a hydro-power station often comes from
the bottom of a dam. If so, it is cold and may not suit species
native to the region.
Water is often released from a hydro-power dam at times that
depend on power consumption (or possibly to suit down-stream
irrigators). The natural occasional high-flows or floods that
the river's ecosystem has adapted to is disrupted.
Run-of-river hydro stations are inflexible in when they produce power.
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There is a trend toward modifying dams to produce hydro-power where
they were not originally designed for that purpose. This is
sometimes called mini-hydro power.
There is of course a continuous
range of hydro-power stations from multi-megawatt down to a few
hundred Watts or even less, see:
micro hydro.
Run-of-river hydro stations produce power when a river provides sufficient
water and only then.
Their power is not
dispatchable.
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Pumped hydro power will become more important as a
way of storing energy as renewables such as solar and wind make up an
increasing proportion of the electricity generation mix.
Most of the advantages and disadvantages of hydro apply also to pumped hydro;
one difference is that the same water can be reused many times in pumped
hydro.
You can read more on pumped hydro at
Energy Storage.
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Technology
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Advantages
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Disadvantages
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Comments
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Conventional nuclear
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Compact; a large amount of electrical power can be produced by
a moderately sized station.
Low fuel costs.
Small number of accidents.
Normally does not produce any significant atmospheric pollutants.
Quantity of waste produced is small.
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Requires substantial amounts of cooling water.
It is expensive, especially in capital costs, maintenance costs,
and due to the long lead time in planning and construction (around
15 years); see
footnote.
The equipment needed to produce the fuel for power reactors is the same
as is used to produce fisile material for bombs.
Large amounts of fossil fuels are used in mining and processing the uranium
fuel; with consequent release of greenhouse gasses.
There is a danger of radiation release, either from the reactors or from
the waste.
This can be enormously expensive, the Fukushima nuclear disaster has been
estimated to cost US$257 billion.
While there are few accidents the consequences of some accidents may be
very serious.
Decommissioning a nuclear power station at the end of
its useful life is very difficult and expensive.
Safe long-term disposal of nuclear waste is difficult.
(It must be kept away from the biosphere for
several tens of thousands of years).
A tempting target for terrorist attack.
War time –
Nuclear power stations would produce a huge amount of radioactive contamination
if bombed.
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There is a great deal of uninformed emotional fear of nuclear power and
nuclear radiation, some is justified, some not.
Low levels of radiation are ubiquitous and the preponderance of the
scientific literature seems to indicate that they are benificial rather
than harmful.
There is insufficient U235 (0.7% of natural uranium) to
provide a major part of the current world electrical consumption
for a long period.
About 99.3% of natural uranium is in the form of U238 which
cannot be used as a fuel in a simple nuclear power station.
To use 0.7% of the uranium and dump the remainder, as is currently done,
is terribly wasteful and, I believe, unethical in regard to future
generations; the U235 can be thought of as the match that can be used to
set fire to the U238 firewood, we are burning the match and denying the use
of the firewood to future generations.
(Fast neutron reactors can use the U238, see
below.).
Is Nuclear Power Globally Scalable?,
(by Derek Abbott, School of Electrical and Electronics Engineering, University
of Adelaide) provides a convincing argument that nuclear power cannot
replace fossil fuels as mankind's main source of energy.
It seems likely that some nuclear power stations that are not economically
viable are being kept in operation because decommissioning and cleaning up
would be more expensive than keeping them going.
(More on nuclear power)
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Technology
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Advantages
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Disadvantages
|
Comments
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'Fast' neutron
nuclear (combined with pyrometallurgical recycling of fuel)
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Compact; a large amount of electrical power can be produced by
a moderately sized station.
Abundant fuel is available from existing stored 'waste' nuclear fuel.
Conventional reactors only use about 1% of the potential power in uranium,
the Fast reactor system could utilise most of the other 99%.
Should not produce any significant atmospheric pollutants.
Quantity of waste produced should be much smaller than for conventional
nuclear.
Nuclear waste from a fast reactor system will need to be isolated from
the biosphere for several hundred years, compared to the tens of thousands for
conventional nuclear.
Thorium, which is about three times as abundant as uranium, can be used
as fuel in a fast neutron reactor.
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The system is not proven on a commercial scale.
Just as expensive as conventional nuclear? See
footnote.
Requires substantial amounts of cooling water.
There is a danger of radiation release.
While the system seems to be sound, the consequences of accidents may be
catastrophic.
Decommissioning a nuclear power station at the end of
its useful life is very difficult and expensive.
The lead time in building a nuclear power station is around ten years,
since this system is 'new' its lead time will be more like fifteen years.
A tempting target for terrorist attack.
War time –
Nuclear power stations would produce a huge amount of radioactive contamination
if bombed.
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Since this system could make use of most of the energy available from
uranium, unlike conventional nuclear, in theory a major part of the current
world electrical consumption could be generated for a long period.
It is claimed that the transuranic elements recovered in the pyroprocessing
are "unsuited for weapons" because they include several isotopes of plutonium,
not just the plutonium 239 favoured for bomb making,
some uranium 238, and fission products.
Bad news for uranium miners. If Fast nuclear takes over from conventional
then no uranium need be mined for several hundred years; the waste of the old
power stations becomes the fuel for the new.
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It is very difficult to obtain reliable figures on the true monitory cost of
nuclear power because of government subsidies.
From New Matilda...
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"Goldberg and Oosterhuis suggest direct public subsidies (for the nuclear
power industry) amount to $115
billion and indirect subsidies to $145 billion in the US alone, while annual
subsidies in the UK equal US$543 million, and in Germany some US$845
million."
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'Fast' neutron nuclear power
The information on the proposed Fast neutron nuclear power combined with
pyrometallurgical recycling of fuel was obtained from
Scientific American, Dec. 2005.
'Fast' nuclear reactors would use reactions involving fast neutrons rather
than moderated neutrons, and probably a low pressure liquid sodium primary
coolant rather than the high pressure water that is used in almost all
conventional reactors.
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Technology
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Advantages
|
Disadvantages
|
Comments
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Solar photovoltaic
(Solar electrical panels)
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Sustainable
It is a well proven technology.
Well suited to providing power in home or single building applications.
By 2019 very viable for utility-scale power generation.
Large roofs can support installations up to 1 MW or so, bigger installations (up to several hundred megawatts) can be built on frames on the ground.
Peak generation matches peak consumption fairly well.
The cost of solar PV has been expensive, but
is decreasing more quickly than any other technology.
In 2019 it is comparable with wind and cheaper than new coal or gas powered generation.
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While the panels are environmentally benign once they are built, the manufacturing process requires large amounts of energy.
One less common, expensive, but highly efficient type of solar panel,
gallium arsenide, contains toxins that need to be disposed of carefully at
the end of the life of the panel.
Solar energy is spread relatively thinly.
If a photovoltaic generator is to produce much electricity (ie. several
megawatts) it has to cover a large area.
Produces little power when the sun isn't shining, no power at night.
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A solar photovoltaic panel must operate for a considerable time before it
produces more power than was required in its manufacture.
Around 2004 the US National Renewable Energy Laboratory stated on its
energy payback
page that "Paybacks for multi-crystalline modules are 4 years for systems
using recent technology and 2 years for anticipated technology. For
thin-film modules, paybacks are 3 years using recent technology, and just
1 year for anticipated thin-film technology".
Can be combined with wind-generated electricity or with mains power. Alternatively, batteries can be charged when more electricity is being generated than is being consumed.
In the past photovoltaic panels have predominantly been based on silicon; other technologies may be used in the future.
One wonders if much consideration is given to pollution implications in their eventual disposal.
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Technology
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Advantages
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Disadvantages
|
Comments
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Solar thermal
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Sustainable, non-polluting
Heat can be stored and used to generate electricity when the sun is not
shining.
This gives solar thermal an advantage over wind which can only generate
electricity when the wind is blowing.
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Solar energy is spread relatively thinly.
If a solar thermal generator is to produce much electricity it has to cover
a large area.
Some forms of solar power require substantial amounts of cooling water.
The sun's position in the sky is continually changing so most
solar thermal generators have to include expensive machinery to
keep them pointed in the right direction.
Solar thermal electricity is more expensive than wind and solar PV;
Wikipedia gave US$0.12 to $0.18/kWh in 2009 when accessed in July 2016.
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Solar thermal energy has been most highly developed in the United States
South West where clear skies are common.
While the technology has great promise it has not yet been proven to be
cost-competitive on a large industrial scale.
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Technology
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Advantages
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Disadvantages
|
Comments
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Solar chimney
(A type of solar thermal)
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Sustainable, non-polluting
Requires little water
Unlike some other forms of solar energy this can produce
electricity at night and for limited periods under clouds
due to the heat stored in the 'greenhouse'.
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Must cover a very large area
While a small (50KW) trial station has run in Spain for some years, the
technology has never been proven on a commercial scale.
War time –
To maximise efficiency solar chimneys must be very tall. They would present
conspicuous and desirable targets for enemy attack.
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The solar chimney concept uses a large 'greenhouse' to convert
solar radiation into warm air. The air is then allowed to rise
up a very tall (around 1km to be highly effective) chimney, turning turbines
and generating power as it rises.
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Technology
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Advantages
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Disadvantages
|
Comments
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Wave
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Sustainable, non-polluting
War time –
Spread over a large area, and some types completely under water, so they
would be difficult to destroy
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Not proven on a commercial scale
Much more expensive than wind and solar PV
Installation would damage the sea-bed locally
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One type (CETO) has been claimed by its designers to be capable of
producing electricity at around Aus$80/MWh (US$70/MWh), similar to the
cost of wind-power (but it seems not to have been proven).
This type can either produce electricity or desalinated water (at a
claimed cost of around Aus$1.50-$2 per kilolitre (US$1.35-$1.80/kL).
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Technology
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Advantages
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Disadvantages
|
Comments
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Wind, large turbines
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Sustainable, non-polluting
A well proven technology and
low-priced for a sustainable energy:
US$60 to US$80/MWh at the wind farm.
Wind farms can be built by moderately sized local or regional businesses,
even by well organised community groups.
Requires little water, no cooling water.
Reduces the exposure of an economy to fuel price volatility.
Very resistant to damage from earthquakes and tsunamis.
War time –
The scattered layout of turbines in wind farms would make it difficult
for enemies to destroy more than a few at any one time.
(For more detail see
Advantages of wind power.)
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Does not produce power when the wind isn't blowing.
If a large proportion of a power system's electricity is wind power then
there will be a need for a correspondingly large backup power supply.
(See
Sustainable Electricity).
To generate large amounts of electricity wind turbines must be numerous and
spread over large areas.
This creates visual and noise annoyance and a significant public opposition
has developed, much of which is based on the NIMBY (not in my back yard)
principle.
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There are many misconceptions about wind farms.
I have notes on problems, alleged problems and objections at
Wind Problems.
An excellent wind power Internet site is that of the Danish Wind Industry
Association.
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Technology
|
Advantages
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Disadvantages
|
Comments
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Bio-voltaic
or bio-electricity
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Sustainable
Can combine sewerage disposal with power generation.
Non-polluting
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Unproven on anything other than a laboratory scale
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Some bacteria have the ability to produce an electrical potential.
These can be fed on something convenient, perhaps sewerage or sugar, and
produce electrical power.
A little more about bio-electricity can be read at
ZDNet, in the news section.
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Technology
|
Advantages
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Disadvantages
| Comments
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Micro hydro
|
Sustainable
Can be used in such a way as to minimise disruption of
aquatic life and stream ecosystems.
Does not necessarily require damming a stream.
Non-polluting
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Requires a flowing stream and a significant change in altitude from intake
to outlet.
A large flow can make up for a small fall, or vice-versa.
If poorly designed and/or operated, it can have similar
disadvantages to large hydro-power, but on a smaller scale.
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Technology
|
Advantages
|
Disadvantages
|
Comments
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Solar photovoltaic
(Solar electrical panels)
|
Sustainable
It is a well proven technology.
Well suited to providing power in home or single building
applications.
Roof-top installations are well suited to high-consumption urban areas
where it has the additional advantage of saving on the cost of building
new transmission lines.
Peak generation matches peak consumption fairly well.
The cost of solar PV has been expensive, but
is decreasing more quickly than any other technology.
In 2013 it is close to parity with wind and new coal or gas power generation.
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While the panels are environmentally benign once they are built,
the manufacturing process requires large amounts of energy.
One less common, expensive, but highly efficient type of solar panel,
gallium arsenide, contains toxins that need to be disposed of carefully at
the end of the life of the panel.
Solar energy is spread relatively thinly.
If a photovoltaic generator is to produce much electricity (ie. several
megawatts) it has to cover a large area.
Produces little or no power when the sun isn't shining.
|
A solar photovoltaic panel must operate for a considerable time before it
produces more power than was required in its manufacture.
The US National Renewable Energy Labaratory
states on its
energy payback
page that "Paybacks for multicrystalline modules are 4 years for systems
using recent technology and 2 years for anticipated technology. For
thin-film modules, paybacks are 3 years using recent technology, and just
1 year for anticipated thin-film technology".
Can be combined with small-scale wind-generated electricity or
with mains power. Alternatively, batteries can be charged when
more electricity is being generated than is being consumed.
Excess electricity can be sold to the grid in some cases.
In the past photovoltaic panels have predominantly been based on silicon.
It is possible that in future a larger proportion will use alternatives such
as gallium arsenide (GaAs) or copper indium
gallium selenide (CIGS). While these elements are much rarer than silicon,
they can be used as a thin film; this makes the cost competitive. One
wonders if there are pollution implications in their eventual disposal.
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Technology
|
Advantages
|
Disadvantages
|
Comments
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Wind, small turbines
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Sustainable, non-polluting
A well proven technology.
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Does not produce power when the wind isn't blowing so a back-up electrical
supply is also needed. If batteries provide the backup they have the
disadvantage of being expensive and needing to be replaced every few years
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Units are available to suit single houses or several houses.
Small scale wind turbines grade into large scale; turbines are
available in a great range of generating capacities.
Can usefully be combined with photovoltaic electricity, so that power
will be generated when either the wind is blowing or the sun is
shining.
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