Introduction
In a remarkably prescient paper presented over 80 years ago, J.B.S. Haldane (1923) predicted that the world would cope with the exhaustion of fossil fuels by turning to large-scale use of wind and solar energy to produce electricity. He proposed that the intermittent nature of these energy sources could be dealt with by using surplus power produced under high wind/sunlight conditions to electrolyse water. According to Haldane the hydrogen and oxygen produced by electrolysis could be stored in liquefied form and expended for industry, transportation, heating and lighting as required, using fuel cells (called oxidation cells by Haldane) to generate electricity from the gases. Haldane thus anticipated the development of a Hydrogen Economy where fossil fuels would be replaced by hydrogen as an energy carrier and the hydrogen would be produced from renewable solar and wind energy sources.

Moves towards the Hydrogen Economy have gathered pace in recent years, driven by a greater awareness of fossil fuel resource limits and the deleterious effects on the environment of their expanding use. Global warming has been clearly linked to increasing greenhouse gas (GHG) emissions (CO2, CH4, N2O) from burning of fossil fuels. Australian GHG emissions for 2000 were 535.3 million tonnes CO2 equivalents (Coles, 2003), of which 68% came from the energy sector. Per capita Australian emissions are amongst the highest in the world and are more than twice the corresponding values for the European Union. They reflect the major contribution of fossil fuel-based electricity generation to Australian CO2 emissions. Power generation consumed 45% of available primary (predominantly fossil fuel) energy in 2000-01.

The greatest scope for reducing GHG emissions in Australia lies in reducing its dependency on fossil fuels, particularly coal, for electricity production. To this end the Australian government has established the Mandatory Renewable Energy Target, to ensure that at least 9.5 million megawatt hours (MWh) of extra electricity are generated from renewable energy sources by 2010, relative to renewable source output in 1997 (www.orer.gov.au). The scheme, which started in 2001, establishes a set of yearly targets between then and 2020.

In the first two years of implementation, extra hydro-electricity generation was the main contributor to the scheme, along with solar hot water (representing an electricity saving). However, traditional renewable energy sources such as hydro and biomass (mainly sugar cane and wood wastes) are not expected to expand much above current levels.  Long-term future expansions are going to come from the inexhaustable energies provided by the sun and wind. Solar and wind energy represent the most abundant natural energy sources that can be tapped without polluting the atmosphere or creating hazardous wastes. Australia is particularly well situated in relation to availability of both of these renewable energy forms. In this article, developments in the applications of wind and solar energy for electricity production in Australia are reviewed.

Wind Energy
Wind power is the world’s fastest growing renewable energy resource, with installed global wind capacity increasing by more than 30% per year, to 30,000 MW in 2003 (For comparison, Australia’s total electricity capacity is ~ 45,000 MW). Europe dominates wind energy developments; Germany alone has 12,000 MW of installed wind capacity, fulfilling Haldane’s prophecy of a “country…covered with rows of metallic windmills working electric motors” (Haldane, 1923). The windmills of today’s Spain would present a most “unequal combat” to Don Quixote (Cervantes), Spain being below only Germany in wind power capacity (~5,000 MW).

Southern Australia is particularly well situated to benefit from a constant, high velocity prevailing westerly wind system. These winds, that brought the early sailing fleets to Australia, are due to a system of anticyclones that drift constantly around the planet, from west to east, between 30 and 60° of latitude. A recent ABARE report (Short and Dickson, 2003) on the Mandatory Renewable Energy Target estimated that wind-generated electricity would account for almost a third of the 2010 target, 2.66 million MWh, equivalent to installed wind capacity* of 950 MW. All the indications from wind energy companies and state governments are that this will be far exceeded. The Victorian government alone has committed to a target of 1000 MW of wind energy by 2010. The Australian Wind Energy Association (AusWEA) reported in 2003 that proposed wind farms in Australia at the planning stage or beyond have a total capacity of 2700 MW (www.auswea.com.au). Most of these planned projects would be expected to be operational within the next few years.

The output from the planned capacity could supply the electricity needs of 1.5 million Australian homes (each using ~5,000 kWh per year) and reduce GHG emissions by 8.3 million tonnes CO2 equivalents per year (based on 1.1 kg CO2 equivalents per kWh of electricity). Although this is a massive quantity of potential GHG emissions savings, it still only represents a little over 2% of Australia’s energy-related GHG emissions in 2000-01, indicating the enormous scale of effort needed to seriously combat climate change.

At the end of 2003, seven different companies had existing wind farms of greater than 1 MW capacity in Australia, providing a total capacity of nearly 200 MW. AustWEA lists another eleven companies that have major wind projects at the planning-through-to-construction stages. The two largest wind developers currently are Pacific Hydro and Hydro Tasmania, both of which have diversified from a hydroelectricity base. Pacific Hydro has 71 MW of existing capacity at the Codrington and Challicum Hills sites in Victoria, and has another 530 MW planned mainly in Victoria and South Australia. Hydro Tasmania has 644 MW of wind farm projects planned or being developed in Tasmania and South Australia. Tasmania is situated in the “Roaring Forties” latitudes and this is reflected in its higher wind capacity factor of 0.4, compared with a factor of 0.32 for Victoria and 0.25 for NSW.

Siting is crucial for wind turbines because the power produced is proportional to the cube of the wind velocity. Wind turbines have a cut-in wind speed of about 10 kph at which electricity starts being generated. Above the cut-in the amount of electricity produced increases until the rotors reach their rated capacity, at typically 40 to 60 kph. The output then remains relatively constant until a cut-out wind speed of about 90 kph is reached at which point the rotors are shut down and turned out of the wind to avoid damage. Dramatic improvements in durability, efficiency and energy output have been made in the last two decades. Variable-speed turbines, direct drive (no gearbox) and rotor pitch control are all new developments that improve performance, especially at high wind velocities. Wind turbines incorporating these features have been installed at Australia’s Antarctic Division Mawson base, where extreme wind conditions can prevail (www.aad.gov.au). They will also be important in the next large-scale wind energy development which is offshore wind farms. In Northern Europe some 20,000 MW of offshore wind farms are currently planned.

Figure 1:  Schematic of Solar Tower (diagram supplied by EnviroMission).

An imaginative new Australian wind power initiative has recently been proposed by the renewable energy company EnviroMission (O’Neill, 2003). The company plans to develop the Solar Tower principle that was conceived by a German engineer, Jorg Schlaich in the 1970s. The project will involve building the world’s tallest structure, shown in Fig. 1, a 1000 metre high tower, fitted with a 3.5 km radius greenhouse “skirt’ around its base, below which trapped air is warmed to ~15° above ambient. A further natural temperature differential of 10° exists between the bottom and top of the tower. The column of hot air rising up the tower will achieve a velocity of 45 kph. The wind thus created turns 32 turbines distributed around the base of the 120 metre diameter tower. Each turbine can produce over 6 MW of power, giving a total output of 200 MW.

A 200 metre high version of the Solar Tower was successfully tested over a 5-year period in Spain in the 1980s. Australia’s first Solar Tower will be built in south-western NSW, just over the Murray River from Mildura. The project has been accorded Major Project Facilitation status by the federal government, while the NSW government has given it State Significant Development ranking in order to streamline the planning approval process. EnviroMission plans to build five such towers by 2010.

The intermittent nature of wind power means that it can’t be used directly to produce base-load power or peak load power on demand. In grid-connected systems the grid itself acts as an effective buffer provided the wind-generated electricity doesn’t exceed 10% or so of the grid capacity. Denmark, which has the highest percentage of wind-produced electricity (~20%), is able to handle the high wind component by having interconnections to grids in adjacent countries. The long-term outlook for the Hydrogen Economy is to use hydrogen as a load-levelling energy storage medium for intermittent sources like wind and solar. Surplus wind-generated electricity would be used to produce hydrogen by water electrolysis. The stored hydrogen could then be used to regenerate electricity when needed in gas turbines or in fuel cells, as well as to supply energy for heating.

Figure 2:  Integrated Wind/hydrogen system (Figure supplied by J Titchen, Hydro Tasmania)

A schematic of an integrated wind/hydrogen system, particularly suited to remote area power sources, is shown in Fig. 2. Hydro Tasmania is collaborating with the University of Tasmania Engineering School to develop such an integrated system. Australia has a solid R&D base in the different components required. CSIRO has leading expertise in fuel cell technology and has constructed and operated systems in the kW range, now being produced commercially by the spin-off company Ceramic Fuel Cells Ltd. CSIRO also has an R&D program to produce compact solid state modular electrolysis systems and has a prototype 3-5 kW electrolyser under development. CSIRO’s Energy Transformed Flagship program has a strong focus on integration of renewables and hydrogen (Wright, 2003).

Solar Energy
As discussed, wind power is a well-established, fast-growing renewable energy source for electricity production, but what about the role of solar energy in Australia? The solar resource is vast. The amount of solar radiation reaching the earth’s surface annually is 4 x 1024 joules, which is of the order of one million times Australia’s annual energy consumption. The total global energy consumption of ~ 4 x 1020 joules could in principle be met by solar collectors with a 10% conversion efficiency covering 0.1% of the earth’s surface. Australia has one of the world’s highest combined levels of solar insolation and free area available for collection. There is also no lack of expertise in Australia for the development of systems to capture and convert the solar energy. Australia is a world leader in photovoltaic solar cell developments. In the 1970s and 1980s, Telecom Australia helped pioneer the application of photovoltaic systems for telecommunications and remote area power supplies (Watt, 2003).

The University of NSW Photovoltaics Special Research Centre (www.pv.unsw.edu.au) set a world efficiency record for a silicon solar cell of 18% in 1983. The Centre subsequently improved the efficiency to 24% in 1994, and has made important advances in reducing silicon cell costs by developing a new technology for coating thin films of crystalline silicon on glass (CSG). The Centre has been active in commercialisation of its products, in collaboration with BP Solar (the Saturn laser-grooved buried-contact solar cell) and Pacific Solar (thin film CSG technology). BP Solar made use of the technologies developed by the Centre in the solar panels it installed on the homes in the Sydney 2000 Olympic Village.

A recent new Australian photovoltaic technology is the Sliver ® Solar Cell, developed at the Australian National University’s Centre for Sustainable Energy Systems, (http://solar.anu.edu.au). The ultrathin cells use 90% less silicon than conventional photovoltaic modules yet maintain efficiencies close to 20%. Origin Energy has selected the technology for commercialisation and began construction in late 2003 on a manufacturing plant in Adelaide to make up to 5 MW of Sliver-based PV panels per year.  The Centre has also been active in the development of parabolic reflective trough concentration systems for focusing solar energy on photovoltaic cells, thereby reducing the amount and cost of the expensive photovoltaic component. The concentration factor is about 20, allowing 17 kWp of power to be obtained from a demonstration system involving 80 mirrors with a total reflector area of 150 m2 (kWp refers to peak power obtained with direct sunlight insolation of 1kW/m2). The Centre has applied the parabolic trough concentration approach to a combined heat and power system (CHAPS) that is being developed for commercial applications with Solarhart (now owned by Rheem). A CHAPS demonstration system is being tested at one of the ANU halls of residence.

A different type of focusing photovoltaic system, based on a parabolic dish, has been developed by Solar Systems Ltd. The company has been commissioned by the Pitjantjatjara Council in South Australia to build a solar power station employing ten parabolic dish concentration systems, each with a concentration factor of about 500. The dishes can track the sun on dual axes. The total output will be 220 kW, which will feed into a mini-grid serving a number of communities and thus reduce diesel consumption by more than 160,000 litres each year. The development is supported by a $1 million grant under the federal government’s Renewable Energy Commercialisation Program (www.greenhouse.gov.au/renewable/recp/). The ANU has been active in the development of solar dishes as solar thermal power units, whereby the concentrated heat is used to super-heat steam and turn a steam turbine. Solar dishes developed at ANU were successfully installed at White Cliffs, NSW in the 1980s, where they produced 25 kW of solar thermal electricity before being converted to solar photovoltaic power generation in 1996.

Australia has also led the commercial development of dye solar cells (DSC), through the company Sustainable Technologies International (STI) based at Queanbeyan. These cells use dye-coated nano-particles of titanium dioxide to convert the sunlight to electricity. The efficiencies of the titania cells are lower (5-10%) than for silicon-based photovoltaic cells but they are cheaper to produce. STI supplied DSC solar panels for CSIRO Energy Technology’s new headquarters in Newcastle. The company is planning an expansion of their manufacturing plant from the current 500 kW of DSC systems annually to 2500 kW, representing some 40,000 m2 of cells.

Despite these impressive developments, the utilisation of solar energy remains low in Australia. The highest-volume application is for solar heating. The Sustainable Energy Authority in Victoria issues rebates for up to 300 solar hot water systems each month and currently about 5% of Australian households have such systems. ABARE reported that solar hot water systems contributed 26% (0.54 million MWh) of the renewable energy certificates over the first 2 years of the Mandatory Renewable Energy Target (MRET), and estimated that solar hot water would contribute 5% of the MRET target in 2010. In contrast, photovoltaic-generated electricity contributed less than 0.1% (1,200 MWh) over the first two years of MRET.

Based on the small contribution of photovoltaics to the 2002 MRET target and the high projected cost, ABARE did not include photovoltaics in the 2010 MRET estimates. However the ABARE analysis was based on grid-connected photovoltaic power only. In 2002, the cumulative installed photovoltaic power in Australia was made up of 34.9 MW of off-grid power, 3.4 MW of grid-connected distributed generation and only 0.85 MW of central grid power (www.iea-pvpsw.org). These figures, with only 11% of grid-connected power, reflect the historical development in Australia of photovoltaic applications in remote area power sources and telecommunications systems and they are in strong contrast to the OECD average of 70% of grid-connected photovoltaic power in 2001.

A just-released (January, 2004) review of the MRET scheme has suggested ways to enhance contributions of photovoltaic energy to MRET, such as increasing the deeming period to 15 years and increasing the threshold capacity from the present 10 kW to 100 kW (www.mretreview.gov.au). The federal government set up a photovoltaic rebate program in 2000 for householders and community use buildings that install grid-connected or stand-alone PV systems. The current rebate for new systems is $4 per peak watt, capped at $4000 per residential system.

Australia stands to benefit from having a major photovoltaic manufacturing plant in Australia, run by BP Solar. The plant produced 25 MWp of solar cells in 2002, equivalent to 5% of world production. About 75% of its products are exported. BP Solar provided the panels for Australia’s largest city-based solar power project at the Queen Victoria Market in Melbourne. An area of 1800 m2 of panels covering one third of the market’s roof provide about 250,000 kWh of electricity per year. A large digital panel display at the Market shows the instantaneous solar power being generated as well as the cumulative power and number of tonnes of GHG abatement achieved.

Like wind energy, solar energy is intermittent, with a low capacity factor, typically about 0.2. Solar-generated electricity, especially in off-grid applications, thus requires an energy storage medium for which hydrogen is the expected long-term main contender. An integrated solar/hydrogen system would look similar to that shown for wind/hydrogen in Fig. 2, except that DC rather than AC power is produced by the photovoltaics. Grant (2003) has presented an interesting analysis of the magnitude of effort needed for future large-scale use of solar/hydrogen. He considered the situation where the oil used to provide petrol for road transport in the US was replaced by the use of hydrogen fuel cells in the vehicles. To generate the hydrogen for the fuel cells by electrolysis, over 2 million tonnes per day of water would be consumed, and an extra 400,000 MW of electricity would be required, equal to the total existing US capacity. To produce this electricity from solar power would require 20,000 km2 of photovoltaic panels, one third the area of Tasmania!

Concluding Remarks
Returning to the vision of a Hydrogen Economy described by Haldane in 1923, recent years have seen this concept move from one person’s imagination to the board rooms of major international petroleum companies, car manufacturers and utilities. These corporations are spending billions of dollars on the development and commercialisation of hydrogen fuel cells, fuel cell vehicles and hydrogen infrastructure. For example, Japan plans to have 5 million fuel cell vehicles on the road and 10,000 MW of energy from stationary fuel cells by 2020. In the medium term, the hydrogen will continue to be generated from fossil fuels, predominantly natural gas. However in the long term, hydrogen will be sourced from renewables.

The current indications are that wind-generated electricity will provide the major new energy source for hydrogen production. However, solar energy is expected to become increasingly important as efficiency improvements and cost reductions continue to be made in photovoltaic systems. Advanced methods for hydrogen production from renewables such as solar thermo-chemical water splitting, photoelectrochemical electrolysis and biological methods are still in the R&D phase. Further development towards commercialisation presents great opportunities and challenges for Australian researchers in the years ahead.

References
G.V. Coles. Energy: sources, economics and the environment. Chemistry in Australia, 70, 16-18, 2003.
P.M. Grant. Hydrogen lifts off – with a heavy load. Nature, 424, 129-130, 2003.
J.B.S. Haldane. Daedalus or science of the future, Cambridge, 1923.
G. O’Neill. Siphoning the sun, Ecos, 116, 10-12, 2003.
C. Short and A. Dickson. Mandatory renewable energy target. ABARE report 03.12, June 2003.
M. Watt. The commercialisation of photovoltaics research in Australia. Report for DEST, September, 2003 (available from www.dest.gov.au).
J. Wright, CSIRO’s Energy transformed flagship program, ATSE Focus, 127, 2-7, 2003.

Ian Grey gained his PhD in Inorganic Chemistry at the University of Tasmania in 1969. After a 12 month postdoctoral study at the University of Texas he joined the CSIRO Division of Mineral Chemistry (now CSIRO Minerals) to work on an industry-sponsored ilmenite upgrading project. His main area of research has been the application of solid state chemistry methods to mineral sands processing and to the chemical weathering of minerals. He has had a number of extended  study leaves at the CNRS Laboratoire de Cristallographie, Grenoble, where he has pursued his other major research interest, the crystal chemistry of oxide materials. He is currently a Chief Research Scientist and Science Advisor at CSIRO Minerals. In 2002, Dr. Grey was elected a Fellow of the Academy of Technological Sciences and Engineering. He was awarded a DSc in Chemistry in 2003, University of Tasmania. Dr Grey’s most recent studies are in the field of hydrogen production from renewable energy sources. They are aimed at improving the properties of titania-based electrodes for use in solar-assisted electrolysis of water.  In March 2004 he received an ATSE Clunies Ross Award.

ATSE Focus is a non-refereed publication. The views expressed in the above article are those of the author(s) and do not necessarily represent the views of the Academy.