Renewable energy

Renewable energy

According to the Australian Academy of Science:

"To have a better than even chance of preventing the global average temperature from eventually rising more than 2°C above pre-industrial temperatures, the world would need to be emitting less than half the amount of CO2 by 2050 than it did in 2000. To do this on a smooth pathway, global emissions (which are still rising) would need to peak within the next 10 years and then decline rapidly."

The Academy organised a public lecture series in 2009 which identified the following technologies as being available 'off the shelf ' and ready for exploitation:

Wind turbines
Though variable, wind turbines achieve a capacity factor (the ratio of average output power to the turbine's rated or maximum power) of up to 50% in Australian wind farms, and require less than 3 to 6 months to recoup the energy used in their manufacture. Currently, large wind turbines are cheaper than any other renewable energy source, and under the Mandatory Renewable Energy Target (MRET) they compete head-to-head with coal-fired electricity generation at current costs. As fossil fuels are anticipated to incorporate their environmental costs with the introduction of an emissions trading scheme, the competitive position of wind turbines should continue to strengthen. Subject to amenity and aesthetic considerations, there are significant opportunities for small- and medium-sized turbines to be installed in urban and semi-urban areas such as sporting fields, parks, shopping centre car parks and industrial areas.

Solar thermal
With appropriate energy storage, this technology offers potential load factors close to 100%, and is ideally suited for base-load power generation. It uses solar concentrators to focus sunlight for electricity generation. To put solar thermal generation systems into perspective, the Sun's energy falling on Australia in one day is equal to half the total annual energy required by the whole world. To power all of Australia's energy needs would require only 0.3% of the land surface to be devoted to solar power generation.

Solar photovoltaic
This technology provides a load factor of 15 to 20%. Solar photovoltaic cells are best for supplying peak demands in the middle of the day, but are less effective in managing the evening peak. Depending on feed-in tariffs, currently photovoltaics require between 4 and 10 years to recoup their investment and 2 to 3 years to recoup the energy used in their manufacture. Current costs are around $0.20 per kilowatt hour (kWh), but with the new technologies currently under development, generation costs are expected to reduce significantly. Solar photovoltaic systems are suited to domestic grid-connect power applications.

Biomass combustion
Potentially able to offer a high load factor, and a 2-year energy payback timescale, these provide a useful supplement to coal in centralised power stations. In semi-rural facilities, the process heat could be used for domestic applications.

Fuel cells
Fuel cells process gas to produce both electricity and heat. Both can be used in a domestic environment to give greater than 80% net efficiency, far exceeding conventional centralised power generation efficiencies, which in Australia are less than 30% for brown coal generators. In the near term, we can expect the following technologies to come on-line for exploitation.

This relies on producing superheated steam in radioactively heated 'hot rock' granite deposits to generate electricity. This process works best when the substrate rock (approximately 5 kilometres deep) has been heated to over 250 degrees Celsius (oC). Fortunately, Australia has several such deposits, notably in the Cooper and Galilee Basins located close to the boundary of New South Wales, Queensland and the Northern Territory. A cubic kilometer of hot granite at 250oC has the stored energy equivalent of 20 million barrels of oil. This technology is in development in Australia by several Australian companies at various levels of operation.

Wave energy
This technology has been well demonstrated overseas, and has shown to be viable in a number of different modes developed in Australia. Wave energy densities to the south of Australia are very high, with potential to offer very high load factors.

Tidal energy
The efficiency of tidal energy depends on the cube of the tidal current. In Australia, only a few locations provide suitable conditions, but this may be useful in niche areas such as supplying the energy needs of some remote settlements.

Solar -panels _LM