This page is companion to Solar power in Australia. New section, 2014/06/17 South Australia's renewables success |
Sustainable energy in AustraliaAustralia is one of the highest per-capita greenhouse gas producing nations in the world, we have a moral obligation to reduce our CO2 production levels.We are suffering terrible climate change damage – consider the decline in run-off in the Murray Basin, rising temperatures, increasing frequency and violence in extreme weather events, increased ferocity of bushfires and length of the fire danger season, increasing acidity of the oceans and rise in sea levels, the decline in rainfall in the southern half of the country, the damage to the Great Barrier Reef, etc. – we should reduce our CO2 production levels for our own benefit. Energy conservation is a big part of the answer, but sustainable energy generation is too, hence this page.
This page was created 2008/11/12, last edited 2022/01/25 Contact: email daveclarkecb@yahoo.com ContentsOverviewSustainable energy generation methodsBiofuel | Biomass | Geothermal | Hydro | Tidal | Wave | Matching Generation with demandThe wind and solar forms of sustainable energy are covered elsewhere on this site. Matters relating to sustainable energyChanges needed in the electricity supply systemMajor tablesBagasse Biomass installations | Landfill Methane Biomass installations | Sewage Methane Biomass installations | Other Biomass installationsReference |
This page is companion to
Wind power in Australia.
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Other sustainable energy pagesWikipedia has a page on Sustainable energy, Renewable energy and Renewable energy in Australia.Other sustainable energy pages on this siteSolar power in Australia | Recent solar developments in Australia | Wind power in AustraliaWind power pages, states...Wind farms in New South Wales | Wind farms in Queensland | Wind power and wind farms in SA | Wind farms in Tasmania | Wind farms in Victoria | Wind farms in Western AustraliaOther wind pages...Wind power potential in Australia | Wind power glossary | Wind power problems |
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Dept. Environment, Water, Heritage and the Arts (DEWHA) data, 2009/02/20, indicated the following totals for installed capacity in the various sustainable energy classes:
Class | MW |
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Bagasse | 467.0 |
Landfill methane | 159.7 |
Other | 216.5 |
Sewage methane | 53.5 |
Solar | 12.3 |
Hydro | 7 956.7 |
Wave | 0.6 |
Wind | 1 760.3 |
Total | 10 626.5 |
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Note that the DEWHA figure above for wind power is 1 760MW while mine on the Wind Power page is 1 494MW. The DEWHA figure includes about 50 wind farms of less than 160kW, which are not included on my page (total of 1.48MW), and Bungendore, Clements Gap and Hallett 2 wind farms (total of 260MW), which as of the time of writing (2009/02/24) were not completed.
The figures above are 'installed capacity'; they do not show the amount of energy actually generated in each classification. Hydro-power infrastructure needs rain before it can generate electricity, the more rain the more electricity; on the other hand, it will not produce much in a drought.
BiofuelBiofuel has a lot in common with biomass. On this page I have used 'biofuel' to mean liquid fuel produced from biological processes and 'biomass' to mean biological solids such as agricultural waste and wood. I have also written a page on firewood as a fuel elsewhere on this site.See Wikipedia. Oil from algaeInteresting research has been carried out in Australia in developing algae, grown is large shallow ponds, as an energy source. Oilgae has an article on this; some extracts from that page..."Dr Jian Qin, of Flinders University, investigated the use of a well-studied green alga known as Botryococcus braunii, or Bb for short, as a supplier of biological hydrocarbons. Bb is a colonial alga of lakes and reservoirs, where it blooms into large, green, floating mats - and it's a remarkably oily little plant. Up to 75% of the dry weight of this particular species is a natural hydrocarbon that can be converted into petrol, diesel or turbine fuel or other liquid or gaseous hydrocarbons."(The salinity of seawater is around 3.5%.) The research was done by Murdock University, "Australian research network BEAM". I was unable to obtain any information from that site due to a broken link. Ethanol from cornThe use of corn as a raw material for the production of ethanol has been financially encouraged in the USA. This is a very dubious practice as the amount of energy input into growing the corn is similar or possibly greater than the amount in the ethanol produced, and of course the corn is diverted from human consumption which is a much more valuable use for it.Ethanol from sugar caneThere may be more potential for growing cane sugar in Australia for the production of ethanol, but care would have to be taken to ensure that the harm done in the agricultural side effects would not be greater than the good achieved.Methanol from wood wasteForestry Insights, NZ discusses how methanol can be produced from wood waste. An excerpt from that page..."Methanol is recovered by a process known as gasification. Wood constituents are broken down to simple gases by heating wood to high temperatures in the absence of oxygen. The resulting carbon monoxide and hydrogen (together known as producer gas) are treated under pressure in the presence of certain copper-based catalysts, producing significant volumes of methanol. Methanol has potential as a liquid fuel, but is also used as feedstock for production of formaldehyde and other chemicals."Wikipedia has an article on Methanol fuel. Concluding remarkThe amount of available agricultural land is entirely insufficient for growing enough biofuels to replace our current use of petroleum, but there is scope for significant production of some biofuels. |
BiomassBiomass has a lot in common with biofuel. On this page I have used 'biofuel' to mean liquid fuel produced from biological processes and 'biomass' to mean biological solids such as agricultural waste and wood.See Wikipedia. Sugar cane waste (bagasse) is used as a fuel. I have dealt with the possible greater use of firewood elsewhere on this site. It is even possible to run a car on firewood. The amount of available agricultural land is entirely insufficient for growing enough biomass to replace our current use of fossil fuels, but there is scope for more efficient use of existing biomass.
Bagasse Biomass installations
Landfill Methane Biomass installations
Sewage Methane Biomass installations
Other Biomass installations
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Geothermal powerThere are two types of geothermal power;
While there is certainly a huge amount of energy potentially available from the hot rocks at depths of greater than four kilometres in parts of Australia (see the Renewable Energy Atlas of Australia), the practicality of tapping this energy efficiently is far from proven. The practical problems of drilling through rocks at high temperatures and at great depths seem to have been overcome. The biggest remaining question seems to be whether the circulating water will quickly remove the heat from a small volume of rock surrounding the larger fractures or whether it will flow through many smaller fractures and efficiently remove the heat from a large volume of rock over a much longer period. |
Hydro-powerThere seems to be nowhere on the Internet that hydro-power generation figures are available for the whole of Australia. (I have made inquiries, Feb. 2009, but do not yet have an answer.) Wikipedia has a page listing hydro power plants in Australia.
Hydro Tasmania runs all hydro power stations in Tasmania and states its long-term average power output as 1180MW (=10 300GWh/yr). As a comparison, South Australia, the top wind power state in Australia, was producing around 210GWh per month (=2500GWh/yr) as of May 2008 (from the Electricity Supply Industry Planning Council of SA, Annual Planning Report, 2008, p64.) The remainder of Australia was producing almost as much wind energy as SA. AGL owns ten hydroelectric generating schemes comprising 16 power stations in Victoria and NSW. New hydro powerAGL is constructing a new $230 million, 140MW underground hydro-power station near Bogong village and beside Lake Guy. The project does not involve building a dam, but does include a new 6.5km tunnel. Some information is on one of the Bogong village pages. |
Matching generation with demandScientific American published an article called Gather the Wind in their March 2012 issue. It discussed a number of methods that could be used to store electricity generated by sustainable methods when it is plentiful so that it could be fed back into the grid when demand outstripped generation.The Scientific American article started with pumped-hydro, which I have written about elsewhere on this page. SciAm went on to discuss compressed air, advanced batteries, thermal storage and, a more speculative, home hydrogen. Air can be compressed when electricity is abundant and stored underground; either in caverns or porous and permeable formations. When demand increases or supply decreases the compressed air can be used to drive turbines and generate electricity. The major problem discussed was the unwanted heating of air on compression and chilling of air on decompression; ways of getting around this were mentioned. The thermal storage was within molten salt, as has been used in several pilot solar-thermal power stations. Under home hydrogen it was suggested that water could be broken up into water hydrogen and oxygen in a home-scale plant when power was cheap and plentiful and these could then be recombined in a fuel-cell with regeneration of electricity as required. Scientific American considered pumped hydro, thermal storage and compressed air the most practicable of the options. |
Pumped-hydro power: matching generation with demand
Characteristics of various generation technologies
Pumped hydro power: General
It follows that there must be some source of electricity available on demand to balance the grid. Pumped-hydro is one such; it can be quickly started and stopped as needed. At present gas-fired generators are most commonly used, at least in Australia, to balance supply with demand, but gas-fired power is unsustainable and we must eventually move to sustainable power. It doesn't matter what causes any inbalance between supply and demand. An excess of power in the grid could be due to many wind farms generating strongly at the same time or to low demand for power in the early morning. A deficiency of power in the grid could be caused by the wind not blowing or to a jump in demand due to many air-conditioners being used on an unusually hot day. What matters is that pumped-hydro can help to provide the needed balance. Denmark obtains about 20% of its power from wind (World Wind Energy Report, 2008) and buys hydro-power from nearby Norway as required to fill in any short-fall in power supply when the wind is insufficient. Not only can hydro-power be fed into the electricity grid when there is a shortage of supply and the wholesale price is high, but energy can be stored as potential hydro-power when there is an excess of electricity and the wholesale price is low. Instead of generating power from falling water, power can be used to lift water from a low-level storage to a high-level storage (see Pumped-storage hydroelectricity in Wikipedia). Reduced run-off into hydro-power catchments in recent years is a major problem for the operators of hydro-power stations, but it could to some extent be overcome by developing pumped recycling of the limited water in the system. Tumut 3 Power Station in the Snowy Mountain Scheme of NSW, for example, is set up for pumped-storage. In generating mode water can flow from the upstream storage, behind Talbingo Dam, through anything up to six turbines into the downstream storage, behind Jounama Dam. At times when electricity is plentiful and cheap, two (or three?) of the Tumut 3 turbines can be used as pumps to lift water from the Jounama pondage up into the Talbingo reservoir. In effect, electricity is stored in the form of the potential energy of the water in the high storage. This system can be, I believe, about 80% efficient.
I know of no new development of pumped-storage hydro in Australia aimed
specifically at balancing the grid since wind power has become a major
component of our power supply; apparently using gas-fired power stations
to fill in the gaps when the wind isn't blowing are
a cheaper option in the short-term.
Pumped-hydro in SA?
SA has few mountain ranges of any significance and generally low rainfalls, so pumped-hydro opportunities are not easily found. What is needed for an efficient pumped-hydro system suitable for short-notice balancing power supply and demand?
How big a storage?A few hundred megalitres at altitudes differing by about 100m is sufficient for smoothing the power from one wind farm over a period of a day, and this seems to be the most economical size. (The energy from 100ML falling 100m is 27MWh – this is roughly equal to the energy from six modern (2016), utility scale, wind turbines running at full power for an hour.)At least hundreds of gigalitres with an altitude difference of 100m would be needed to smooth the output from all the wind farms in SA over a period of weeks. Sites suitable for such large storages are probably not available in South Australia, but may be in the Great Dividing Range in the eastern states. Where are suitable sites available in SA?Basing a small pumped-hydro systems on existing water reservoirs such as Little Para and Mount Bold may be viable, but the altitude difference would only be around 40m. A smaller reservoir could be built close on the downstream side of the existing storages and water shuttled between the new lower storage and existing higher storage.The most obvious source of large volumes of water is the sea. If sea water is to be used then where are there elevated areas suitable for storages of considerable size close to the coast and close to the power grid? There are few such places; the north coast of Kangaroo Island (both the main part of the Island and the Dudley Peninsula) is one, the southern Fleurieu Peninsula is another. There are some moderately elevated areas along the western coast of Eyre Peninsula, but they are not suited for building large water storages. Kangaroo Island and Fleurieu Peninsula pumped-hydro
10GL at 170m elevation has a potential energy of around 5GWh, which would be sufficient for smoothing the output from several hundred turbines for periods of a day or so, or around a hundred turbines for a much longer period. (Peter Lang, referred to above, wrote that Australia's pumped-hydro energy storage capacity was "roughly 5GWh can be stored per day and 20GWh total".) If the pumps and generators were 250MW they could run for 20 hours. Based on a cost of $2000/kW this gives a total capital cost of $500m. My calculations on Cathedral Rocks Wind Farm (see below and in the box on the right) suggest that it would be desirable if the pumps have twice the capacity of the hydro-generators; so perhaps 250MW in pumps and 125MW in generators (maximum operating time 40 hours) would be preferable. So a capital cost of $375m might be more appropriate. I will assume that power from the facility can be sold for about three times the buying price. (Peter Lang used $150/MWh buying and $600/MWh selling; I will use $150/MWh buying for pumping and $450/MWh selling from generation.) Supposing four hours of pumping at 250MW and eight hours generating at 125MW each day, an effeciency in each operation of 85% (combined efficiency about 72%, which I believe is conservative), we can calculate annual pumping costs of about $64m, generation income about $140m, a gross profit of $75m and a pay-back time of 5 years. 100GL-plus storages, if they could be found at similar altitudes, could smooth the output of a large part of SA's wind power generation for periods up to a few weeks. If the costs are dependent mainly on the capacity of the pumps and generators then the greatest possible storage is a high priority.
Pumped storage at Cathedral Rocks – an exercise
Not only would a system like this allow power to be fed into the grid at times of low generation, but it could profitably divert wind-generated electricity from the grid at those times when there was excess generation. (At such times a penalty is payable by the wind farmers.) I did some calculations based on this idea. The dark blue line on the graph shows the power actually generated by Cathedral Rocks wind farm on 2011/02/25 (AEMO data); there was strong generation early in the day and very little from midday to about 2200hrs. When wind generation was plentiful, early in the day, I modelled diverting power from the turbines to a pump that lifted water from the sea to a cliff-top storage; this power is shown by the pink line. When the wind dropped (hour 7 and then hours 9 to 21) I ran water from the cliff-top storage through a hydro-power station; this power is shown by the yellow line. The aqua coloured line shows the final, smoother, output from the combined wind and hydro station into the grid. In effect, some of the power from the early morning generation was stored and then fed into the grid later in the day when the wind stopped blowing. My model was a very simple one. In reality one would have to give serious consideration to the need for variable pumping rates and variable rates of hydro-generation. For the sake of efficiency it may be necessary to have several pumps of different sizes and several hydro-generators of various sizes; I have just used one in my model. The cliff-tops at Cathedral Rocks are rather more than 100m above sea level; I used 100m as the altitude for the hypothetical storage. As mentioned elsewhere in these pages 2.7MWh is required to raise 1GL by 1m. The calculations assumed an efficiency of 85% for the pump and the same for the hydro-power generator. The pump had a capacity of 30MW; 15MW would be sufficient for the hydro-generator (the installed capacity of the wind farm is 66MW). The cliff-top storage needed a capacity of 500ML, which could be handled by a reservoir about 330m long, 250m wide and 6m deep. This would be sufficient for smoothing one day's output, a larger storage would be needed if smoothing was required over a longer period. The pipe for pumping would need to be about 2.5m in diameter, a slightly smaller one would suffice for the hydro generator. |
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Tidal powerTidal power is a form of Hydro-power. So far as I know there is no significant tidal power generated in Australia in early 2009.From ABC Online news... Tuckey pushes Kimberley tidal powerThis article seems very speculative and should not be taken too seriously. |
Wave powerScientific American (March 2009) printed that 40 to 70kW per metre of wave power could theoretically be generated on the Pacific Northwest coast of the USA (US Dept. of Energy figures). Many parts of the Australian coast would have similar potential.ABC Science on-line published an article by Rebecca Martin 2009/02/23. "A recent report by RPS MetOcean, commissioned by Carnegie Corporation, one of the Australian companies looking to launch wave power technology, suggested that Australia had a near-shore wave energy resource of 170,000 megawatts, or around four times the national installed power generation capacity.Martin quoted Andy Baldock who is a UK wave energy analyst from engineering firm Black & Veatch: "There's a phenomenal number of [wave technology] devices out there, with several thousand patents. Over 100 ideas have been actively pursued, of which around 50 have had a reasonable amount of work done on them and around 20 are still being pursued quite seriously. At least ten are planning to do near full scale prototypes."The resource is there, the technology is well under way, the question is, is there the will in the Australian people and the Australian government to change away from fossil fuels? The Australian Greenhouse Office lists three wave power projects:
From ABC On-Line News Wave power plan mooted for Eyre Peninsula.Many projects are proposed, few come into being. |
News2009/06/22
The Federal Government has for several years provided a 50% subsidy for
installation of solar and wind energy systems in
those households that are not connected to the electricity grid.
It was scrapped today without any warning.
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Comparative costs of power generation
The data that were in this section became outdated and were deleted. Up to date costs of solar, wind and other electricity generation methods are on another page on this site. |
Balance in sustainable energy rebatesI have discussed various state and federal sustainable energy rebates elsewhere on these pages. The danger of using rebates to encourage the take-up of sustainable energy is that, if they are not well thought out, they may be unfair and cause unintended harm to some sectors of the industry.At the time of writing (2009/02/28) there are rebates for installing photovoltaic power on private homes and schools, but no rebates for installing small wind turbines, except in isolated areas not connected to the electricity supply grid. This is very unfair to the manufacturers and suppliers of small wind turbines and it discourages development of this, potentially important, sector of the sustainable energy industry. |
TransportHydrogen powered cars have been discussed as an option for renewably powering future transport, unfortunately they do not seem to be near practicality yet (as of Nov. 2008).Electric cars do seem to be near practicality, and they can be 'green' if their batteries are recharged using green power (not fossil-fuel or nuclear generated power). Their biggest drawback is their relatively short range; around 100 to 150km. Electric CarThe Green Car Website, Oct. 26th 2008, carried a story about a proposal by alternative-energy car company Better Place to set up an electric car network in Australia.The idea is that people would buy the cars and then pay by the mile to use them. The range on one charge would be around 100km, the cars would be aimed at the commuting market, and the company would provide numerous recharging stations. The quote below is from the Better Place page on the subject... "We selected Australia, the world's sixth largest country, to show that our model works in any country, regardless of size. If Australia can do it, so can others. We will build an electric vehicle network capable of supporting the switch of Australia's 15 million gas cars to zero emission vehicles. We have two strong partners: AGL Energy, with Australia's largest portfolio of privately-owned renewable generation; and Macquarie, well known for making smart infrastructure investments around the globe. AGL will provide all of the renewable energy - from wind and other sources - needed to power the electric vehicles and work with Better Place to optimize the network. Macquarie will provide financial advice to help raise AUD $1 billion for the initial network build. Moving Australia off oil will benefit the economy and the environment." Of course the suggestion that the cars will have zero emissions is marketing bullshit; emissions do not only come from the vehicle fuel. However, they should be far better than the present petroleum based cars. I have written at greater length on sustainable transport, in the global context, elsewhere. |
LinksCEDEX (Carbon Emissions inDEX) report, by Pitt and Sherry, 2014. Shows how much carbon emissions decreased from 2006 to 2014.Yes to Renewable Energy, a campagn in support of the development of renewable energy projects in Victoria by Friends of the Earth. (A response to the anti-renewables stance of the new, 2010, Victorian Liberal Government.) The Energy Report by WWF (Feb. 2010; 8MB). Peter Seligman's "Australian Sustainable Energy – by the numbers". Inspired by "Sustainable Energy – without the hot air" by David J.C. MacKay, FRS. "http://energy.unimelb.edu.au/uploads/Australian_Sustainable_Energy-by _the_numbers3.pdf" (there should be no spaces in this URL; 2MB). Melbourne Energy Institute, University of Melbourne, July 2, 2010. A very good read. Australian Sustainable Energy: Zero Carbon Australia Stationary Energy Plan, "http://www.energy.unimelb.edu.au/uploads/ ZCA2020_Stationary_Energy_Report_v1.pdf" (there should be no spaces in this URL; 9MB). From The University of Melbourne, Energy Research Institute. |
Balancing generation and loadFor any form of sustainable energy to be developed efficiently and effectively, techniques must be employed to help balance the variable generation inherent in sustainable energy, such as wind and solar, with the demand for electricity (the load).Price-responsive-load, in which the electricity market can respond to retail electricity price changes, must be adopted as soon as possible. For this to work several changes must be made to the way electricity is sold, especially at the retail level:
I asked Terry Teoh of Pacific Hydro whether PH was looking into pumped-storage hydro as a means of levelling supply and demand relating to wind energy development. A part of his answer... "In the short term the intermittency of wind can more easily be dealt with (from both technological and cost perspective) by using gas generators to handle the increased dynamic variability. Gas generators already perform the bulk of the balancing function for SA as our overnight demand is roughly 50% of daytime demand. Adding more wind into the system causes gas generators to be a bit 'busier' and for now this is cheaper than storage. The existing market design should allow this to occur quite readily."Balancing generation and load is dealt with in greater depth in Sustainable electricity elsewhere on this site. |
Storing electricity
Storing electricity as a way of balancing the grid is closely linked to the principle of Price-responsive-load. Over several years up to mid 2014 (as I write this) there has been a lot of discussion about batteries, but by far the greatest energy storage capacity in the world is pumped storage hydro. From Wikipedia: "Pumped storage is the largest-capacity form of grid energy storage available, and, as of March 2012, the Electric Power Research Institute (EPRI) reports that PSH accounts for more than 99% of bulk storage capacity worldwide, representing around 127,000 MW. PSH reported energy efficiency varies in practice between 70% and 80%, with some claiming up to 87%."
The graph at the right shows some energy storage techniques and their capital costs in terms of energy and power. An important factor that it does not show is the efficiency of each process, that is, how much energy is lost in storing the energy and getting it back. Capacitors and flywheels can be highly efficient, batteries less so, and perhaps compressed air least of all? The length of time the power must be stored is an important variable. Capacitors and flywheels are well suited for storing power for short periods (capacitors leak and flywheels run down), hydro suits longer periods because the water stays where it is put until it is needed. Pumped-storage hydro-power is a part of the answer; heat storage in solar-thermal plants is another part, techniques like the reversible formation of ammonia from hydrogen and nitrogen (experimental and not shown on the graph) could be another part. The capital costs of most of these techniques is quite high. An opportunity will arise when and if electric vehicles become common, the batteries will already exist for use in the cars; there will be no additional capital cost. It will be possible for the car batteries - which will be connected to the power grid for recharging - to be used to help balance electrical supply and demand. They will, at the same time, produce some extra income for their owners who will be selling electricity when it is expensive and buying at lower prices. It is possible to store huge amounts of compressed air in geological formations; this involves much less capital expense than storage in man-made tanks. All these methods depend on opening the electricity market to free trade, similarly to most other markets. Also see:
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The need for transmission lines:
What is stopping Australia developing its full sustainable energy potential?
One of the big problems is our power transmission system; lack of political
will is the ultimate problem.
To mid 2010 no long-distance power transmission line has been built
or upgraded anywhere in Australia specifically for the development of
renewable energy.
In contrast,
"Nine European countries, including Germany, Britain and France, have
announced plans to create a huge inter-country power grid in order to
utilise electricity from renewable energy production more efficiently."
This is expected to cost about $46b. (2010/01/07; Renewable Energy News)
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Epuron has proposed a 1GW wind farm for Silverton near Broken Hill. If it is to be run effectively a high capacity transmission line will have to be built from Broken Hill to connect with a larger power market (Average power consumption for the whole of SA is about 1.5GW; Broken Hill could not use 1GW). Epuron intends to build a 290km transmission line from Silverton to the NSW end of the Murraylink HVDC Interconnector at Redcliffs. An imaginative government committed to sustainable energy might rather build a 5GW transmission line from Mid North SA through Broken Hill to Sydney (1200km), with a branch to Brisbane to cater for expansion in the SA sustainable energy industry.
Importantly such a line could also feed power back into SA when needed. In the record heat-wave of January 2009 that affected Victoria and South Australia a number of large areas had to be blacked-out because of record power consumption and the failure of the Bass-Link line to Tasmania. Heat-waves often affect both Victoria and South Australia at the same time; a link between South Australia and NSW would be very valuable at those times.
Australian governments have always been willing to build transmission lines to serve new fossil-fuel power stations, why - if they are as much in favour of sustainable energy as they claim to be - are they unwilling to build them for sustainable energy development?
Should we follow the lead of Texas? From Terry Teoh (Pacific Hydro)...
"Texas is in process of implementing their CREZ (competitive renewable energy zones) policy which is a departure from contemporary electricity sector micro-economic thinking in the industrialized world. Under CREZ, government takes the up front risk of building the backbone transmission system to remote regions which have world class wind resources. The transmission capacity is then auctioned to the private sector. So government takes a 'build and hope' approach."In Australia we can only dream of this sort of pro-active action on the part of government. Also see Texas State Energy Conservation Office.
Western and northern SA have huge potential for geothermal and solar power. They could use the same interstate connectors: once they have been proven to be economically viable, an HVDC line from around Inaminka to Broken Hill (supposing that by that time Broken Hill is connected to both east and west by a high capacity transmission line) should be built.
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South Australia's renewables success storyI have written a separate page on this elsewhere on this site.
Indeed, in a windy period SA gets most of its electricity from the wind, as shown in the graph on the right. |