Numerous studies have considered the mix of energy sources that could be used to power Australia while sharply reducing our reliance on coal fired power plants. Some of the important criteria are as follows:
* The more practical plans are those that rely heavily on existing technologies already deployed on a large scale.
* The more practical plans avoid heavy reliance on the most expensive technologies.
* The proposed electricity supply scenario must provide reliable electricity, either by avoiding excessive reliance on intermittent sources (e.g. solar PV or wind) or by incorporating energy storage systems.
One of the most practical Australian studies was produced by academics for the Clean Energy Future Group (CEFG) (Saddler et al., 2004). It is practical in that it makes virtually no allowance for technical innovation, restricting itself to existing commercial technologies. The study is conservative in that it factors in official projections of economic growth and population growth.
The Clean Energy Future Group proposes an electricity supply scenario which would reduce greenhouse emissions from the electricity sector by 78% by 2040 compared to 2001. The clean energy scenario comprises energy efficiency and conservation measures and electricity supply based on:
* solar 5%
* hydro 7%
* coal (9%) and petroleum (1%) 10%
* wind 20%
* bioenergy 28% − largely from agricultural crop wastes so it is not competing with other land uses
* gas 30%
Cogeneration − the combined production of electricity and useful heat, using turbines and engines on the site where energy is used − plays an important part in the CEFG plan. The plan envisages cogeneration plants providing 15% of total electricity (13% gas, 2% bioenergy).
The CEFG study can be thought of as a baseline study, or a ‘worst case’ study, because it makes no allowance for developments in important areas like solar-with-storage or geothermal power. University of NSW academic Mark Diesendorf, who contributed to the CEFG study, has proposed a more ambitious scenario which replaces all coal and gas with renewables. Dr Diesendorf states: “By 2030 it will be technically possible to replace all conventional coal power with the following mixes: wind, bioelectricity and solar thermal each 20 to 30%; solar photovoltaic 10-20%; geothermal 10-20%; and marine (wave, ocean current) 10% … There is an embarrassment of riches in the non-nuclear alternatives to coal.” (Diesendorf, 2010b.)
This graph illustrates a clean energy plan for Australia in which coal power is phased out by 2030 by means of energy efficiency and conservation, natural gas, and renewable energy. (Source: Mark Diesendorf)
Dr Diesendorf (2010) writes: “With the temporary assistance of gas, energy efficiency and renewable energy are now sufficiently advanced technologically to substitute for all use of coal in Australia by 2030. Furthermore, the economic savings from demand reduction could pay for the major part of the additional costs of renewable energy. The barriers to this essential transition are vested interests in greenhouse gas emissions: coal, oil, electricity generation, aluminium, steel, cement, forestry based on logging native forests, and some types of agriculture. These vested interests are disseminating fallacies about greenhouse science and greenhouse mitigation. Common fallacies are that making the transition to renewable energy will cost jobs and that renewable electricity is not sufficiently reliable for providing a national electricity supply system.”
CSIRO scientist Dr John Wright (2009) has proposed a scenario in which renewables generate over three-quarters of Australia’s electricity by 2050:
* wind 19.4%
* geothermal 19.0%
* solar thermal 18.3%
* solar PV 12.8%
* bioenergy 5.1%
* ocean energy 0.7%
Dr Wright states: “Overall, increasing renewable energy technology will take out in the order of 200 million tons of CO2 by 2050 under this scenario. That is equal to about all of our major stationary energy CO2 emissions now. This is a major, major change.”
Australian engineer Peter Seligman (2010) has proposed an energy supply system for Australia based largely on geothermal, wind and solar power. Dr Seligman’s conclusions are as follows:
1. In theory, Australia could comfortably supply all of its power requirements renewably.
2. In practice, for some interim period, the use of some non-renewable sources may be necessary but the overall carbon footprint can be reduced to zero in time.
3. The major contributors would be geothermal, wind and solar power.
4. To match the varying load and supply, electricity could be stored using pumped hydro, as it is at present on a much smaller scale. In this case, seawater could be used, in large cliff-top ponds.
5. Energy efficiency would be a key aspect of the solution.
6. A comprehensive modelling approach could be used to minimise the cost rather than the current piecemeal, politically based, ad hoc system.
7. Private transport and other fuel based transport could be largely electrified and batteries could be used to assist with storage.
8. In a transition period, liquid fuel based transport could be accommodated by using biofuels produced using CO2 from any remaining fossil fuelled power sources and CO2 generating industries.
Dr Seligman proposes the construction of a large pumped hydro energy storage system. When electricity is in short supply (e.g. calm, cloudy days), water from a very large reservoir is run downhill through turbines to generate electricity. At other times, water is pumped up hill to replenish the reservoir.
Siemens Ltd. (2010), a company with extensive involvement in the energy sector, has mapped out an energy plan for Australia in which the contribution of fossil fuels to electricty generation falls from 93% to around 10% (all of the remaining fossil fuel plants have carbon capture), with the remainder generated by a mix of renewable technologies consisting mainly of wind (18%), solar (35%) and geothermal (17%). Large scale energy storage is provided by a mix of solar thermal and hydrogen.
Siemens chairperson Albert Goller said: “We have many enviable opportunities in Australia such as our abundance of natural resources, and Australia has the potential to be at the forefront of technology. Even the possibility of being a net exporter of clean electricity is realistic for Australia. Implementing technologies will not only help create a sustainable future, but also new skills and job opportunities in remote regions, whilst providing economic growth.”
In the Siemens plan, most large-scale transmission interconnectors are High Voltage Direct Current (HVDC), providing significant reduction in losses and thus allowing for efficient, long-distance transmission of renewable energy-generated electricity around the country. Siemens also proposes the development of HVDC links to South East Asia allow export of renewable electricity.
In the Siemens plan, virtually all land transport is electric or hydrogen based. As the majority of power generation is renewable, the road transport fleet becomes virtually greenhouse gas free. A high speed rail network provides efficient transport between major cities. By 2050, 20% of vehicles are hybrids, 55% are electric/hydrogen powered.
Greenpeace (2010) has produced an ambitious ‘Energy [R]evolution’ blueprint for a renewable energy future in which renewable energy’s share of Australia’s total generation increases to 75% by 2024 while coal’s share reduces to zero by 2020. This scenario would halve annual greenhouse emissions in Australia’s energy sector. Employment in the coal industry would drop by 11,000 and renewable energy job numbers increase by 54,000. The electricity supply mix includes contributions from wind (21%), solar thermal (15%), solar PV, geothermal (7%), bioenergy, hydroelectricity and ocean energy.
Another ambitious study is the Beyond Zero Emissions’ Stationary Energy Plan (2010). This plan envisages Australia’s electricity supply being converted to renewables by 2020. Solar thermal plants with molten salt storage provide 60% of electricity and wind 40%, with back-up from hydroelectricity and bioenergy (crop wastes).