WorleyParsons has a vision: to be the driving force behind an industry which could provide 40 per cent of Australia’s renewable energy needs by 2020. To deliver on this goal, the company is looking to Australia’s natural and powerful resource, the sun.
Embarking on a development that has the potential to see 30 solar thermal power stations, incorporating 8,500 megawatts (MW) of solar capacity built in Australia by 2020, WorleyParsons Managing Director – EcoNomics™ Peter Meurs has said that solar thermal power is the next step to delivering renewable energy to Australia.
However, Mr Meurs has warned that to achieve this stated goal, action must be taken today. “We require implementation of technologies that are proven and ready to use, as well as effective leadership in regulation, manufacturing and support for new technologies.”
The AST idea
The initial idea for the Advanced Solar Thermal (AST) study was born when Western Australian Water Corporation CEO Jim Gill and WorleyParsons’ then Managing Director Peter Meurs were considering how to provide renewable energy for desalination in Perth.
Their idea grew when Verve Energy, Western Power and Woodside joined the Water Corporation and WorleyParsons as foundation sponsors of the AST initiative. In a partnership that now includes Rio Tinto, Fortescue Metals Group, Delta Electricity, BHP Billiton and Wesfarmers – who have joined as supporting sponsors – the AST study aims to meet the challenges facing Australia as the nation moves towards a 20 per cent Mandatory Renewable Energy Target (MRET) by 2020 and a 60 per cent reduction in greenhouse gas emissions by 2050.
Using proven technologies and engineering solutions, WorleyParsons believes that AST could provide almost half of the additional forecast renewable energy demand – an estimated 450,000 gigawatt hours – by 2020. The venture aims to have the first AST power station commissioned in 2011 with the potentialfor 33 additional 250 MW AST power stations to be built between 2012 and 2020.
Mr Meurs says that while solar is not the only technology to meet this increase in renewable energy demand, it has the capability to be a major contributor.
“WorleyParsons expects many renewable energy technologies will contribute to meeting this target, but believes that AST could meet around half of this based on initial findings, its sheer scale, experience in other parts of the world and when considering the relative technical, social and financial merits of the renewable energy options that Australia has,” he says.
However, he reaffirms the investment needed for the initiative to be successful. “While we believe that AST could fulfil around 40 per cent of the new MRET requirement,” he says, “this will need an investment of around $35 billion and huge engineering resources to accomplish. WorleyParsons believes it has the capacity to bring together the resources required to achieve this huge task.”
Solar thermal power – proven technology
According to the Renewable Institute for Sustainable Research, it was a French mathematician, August Mouchet, and his assistant, Abel Pifre, who constructed the first solar powered engines in the 1860s, which they used for a variety of applications. These became the predecessors of modern parabolic dish collectors that are used in solar thermal technology today.
Mr Meurs explains that there are four key solar thermal technology types. Parabolic troughs are long curved mirrors – like water troughs – that focus sunlight onto a long thermal energy receiver installed above the mirrors. Linear Fresnel reflectors are similar to parabolic troughs but use multiple flat mirrors. Stirling dish engines are similar to linear Fresnel but are smaller individual units shaped like dishes concentrating onto a single point. Finally there are central receivers, where many individual mirrors are focused onto a single point that is usually located on a tall tower. Each technology differs in the way that it concentrates the solar energy, but they all track the sun to maximise energy capture and produce heat, which is then converted to electricity.
“These technologies are at different stages of development and each has its own advantages and disadvantages,” says Mr Meurs. “It is fair to say that parabolic troughs are the most mature, having first been installed at utility scale in the 1980s; although the other types may ultimately prove cheaper due to their inherent design advantages.”
While all of the different technologies are being assessed in the present AST study, Mr Meurs says that the first plant will probably use parabolic troughs – a technology that has been in use in California, United States for over 20 years.
While the choice of technology that is used for a given site will come down to issues of life-cycle costs, maturity, practicality and risk, says Mr Meurs, as these can change with time, alternative solar thermal technologies are not out of the question.
Concentrating and capturing solar power
An AST plant generates power in a three stage process. Solar energy is first collected at a solar island, stored if need be and then converted to electricity at a power island.
At first generation AST solar islands, parabolic troughs will be used to concentrate sunlight onto collector tubes. The mirrors will track the sun from east to west during the day, while oil is heated in collector tubes that are located along the mirror’s focal point.
At the power island, heated oil from the solar island will heat water in a boiler to produce steam, which will drive a steam turbine to generate power.
Mr Meurs says that energy storage opportunities are just one advantage of an AST plant compared to some other renewable technologies. “Many of the technologies being assessed in the AST study have significant heat capacity in the form of hot fluids, which are used to transfer the energy from the solar array to the electricity generation module. This relatively short term energy storage can take out fluctuations in output due to clouds.
“This can be taken a step further if serious energy storage is added either through simply adding more fluid in the normal system, or adding significant thermal energy storage in the form of molten salts.”
Of these two options, Mr Meurs says that storing excess solar heat in molten salts, which will extend the plant’s operating hours, is more economically efficient. While salt storage is still in its infancy, several concentrating solar plant projects currently being built in Spain will use the technology and Mr Meurs is confident of the opportunity to store solar thermal electricity.
“Such large scale storage can increase the amount of energy captured and can defer plant output to increase the ability to match load, which increases further the value and dispatchability of the plant.”
Commercialising an Australian AST opportunity
For the AST initiative, the potential to capitalise on solar thermal power is clear. The country has large areas of high solar intensity and little rain, where large concentrations of renewable energy power stations could be developed.
“These renewable energy centres can be linked to the national energy networks and allow Australia to take advantage of one of the largest solar resources around the globe,” a WorleyParsons spokesperson said.
The AST initiative will provide the initial engineering and business analyses for companies to develop AST plants. And as Mr Meurs explains, it is likely that many of those parties interested in AST plants will undertake further site specific project research through full feasibility studies.
So far, the AST study has shown that there are significant differences between potential sites. These include factors such as a site’s solar resource, the availability and suitability of land, the type of grid connection, the logistics involved for construction and operation and the type of load or energy market that the project would service. These variables, says Mr Meurs, may significantly affect the technical design of the AST solution and the most efficient economics for a particular site.
“The AST study will not solve this for each potential site, but we have tried to distil this down through complex GIS mapping to identify the most likely areas in Australia for AST plants.”
He adds that the study has gone further by comparing individual sites, revealing the ways in which AST plants can vary depending on specific site issues. The AST study’s research will also guide potential AST owners in identifying prospective sites and in understanding how the plant may change depending on the particular issues at that site.
“In many ways, the AST study provides the intelligence to make informed decisions about going the next step with this technology option,” he concludes. WorleyParsons has identified a
range of factors that have created an opportunity for economic utility-scale (a generation unit capable of connecting to a major power network) energy sources in Australia, including the MRET, the nation’s international emissions reduction obligations, the energy requirements for Australia’s seawater desalination efforts to achieve water security and the growing awareness and demand for renewable energy.
WorleyParsons has said that establishing AST centres could allow Australia to exceed the 20 per cent renewable energy target by:
• Facilitating the commercialisation of developing renewable energy technologies
• Triggering the development of domestic solar thermal component manufacturing
• Enabling Australia to become a world leader in these technologies
• Allowing the construction of larger scale solar thermal power stations over time.
A world AST leader
The AST initiative is confident of bringing utility-scale renewable power to Australia. Mr Meurs has said that Australia is uniquely positioned to take a world leadership role in the design, manufacture, implementation and operation, and grid integration of utility scale solar thermal power systems. Moreover, he believes Australia has the capability and the right kind of support from industry and government to take action.
As the AST initiative works to develop AST technology into viable power plants, WorleyParsons has called for leadership from government, major power purchasers and power station developers.
Mr Meurs states it plainly. The long term success of renewable energy requires an even playing field between all generation sources.
The benefits of AST dispatchability:
Solar thermal has the advantage of producing energy at times of high demand in Australian grids, when the energy is worth more.
• AST power stations can provide utility-scale renewable power, as they are economic in the range from 50 to 300 MW
• AST technology has peak load coincidence, matching energy output to energy demand as people rise, use energy and rest along with the cycles of the sun. In matching output to demand, AST technology has the potential to reduce the need for fossil fuel peaking capacity on the grid.
• Following the sun’s known pattern from day to day and season to season, AST power stations are more predictable. Moreover, AST technology is less variable: whereas sunlight is decreased by cloud, AST output can be maintained by thermal capacity or storage.
CHAPS systems at ANU
The images used throughout this piece are of the Combined Heat and Power Solar (CHAPS) systems at the Centre for Sustainable Energy Systems at the Australian National University (ANU).
CHAPS systems concentrate the sun 30 times to a linear focus on the underside of a receiver suspended above a parabolic trough concentrating system. The solar cells used in the receiver will produce around 30 times the current of conventional solar cells while maintaining the same voltage. Solar thermal research and development began at the ANU in 1971. The university has the largest dish solar concentrator in the world – a 400 metre square dish concentrator prototype that will soon be replaced by a 500 metre square dish.
In partnership with Wizard Power, the 500 metre square generation II big dish has been completely re-designed for optimisation for manufacture and features 380 identical mass produceable mirror panels and should be able to concentrate the sun at least 2,000 times.
Image caption: Solar-thermal parabolic trough mirrors at Kramer Junction, in Mojave Desert, California
Appeared in issue: EcoGeneration — November/December 2008
Categories: Solar, Technology
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