The Northern Territory (NT) is among the regions in Australia and the world with the highest solar radiation intensities. The NT has many mine sites which consume significant amount of fossil fuel with consequent greenhouse gas (GHG) emissions. The environmental concern related to the fossil fuel consumption and availability of immense solar energy resource in the NT open the possibilities for considering the provision of power to the mining sites using proven solar technologies. Concentrating solar power (CSP) systems are deemed as the potential alternatives to current fossil fuel based generating systems in mining industry in the NT. The finding is based on consideration of the major factors in determining the feasibility of CSP system installation, with particular reference to the NT mine sites. These are plant design requirements, climatic, environmental, and other requirements, and capital and operating costs. Based on these factors, four mine sites have been identified as having the potential for CSP plants installation. These are McArthur River Mine, Ranger Mine, Northern Territory Gold Mines, and Tanami Operations. Each site could be served by one CSP plant to cater for the needs of mining operation and the local communities.
Like many other nations, Australia is committed to reducing its carbon footprint by reducing its greenhouse gas (GHG) emissions by 20% by 2020 and an additional target of reducing them to half by 2050 . Australia’s annual GHG emissions for the year to December 2012 were estimated to be 551.9 Mt CO2-e . Australia generates only 1.5% of global GHG emissions; however, for the year to June 2012, the national inventory emissions per capita were about 24.4 tonnes CO2-e . On a per capita basis, Australia is one of the world’s highest GHG. Australia’s main sources of GHG pollution are electricity generation, transport, agriculture, industrial processes, land use, and waste . Among these sectors, electricity generation is the biggest GHG emitter with a 36% share .
Australia’s electricity generation in 2011-2012 is 253,851 GWh, a 0.5% increase from 2010-2011 , with coal (69.1%) and gas (19.3%) being the main fuels. The share of all renewable energy sources is 9.4% with hydro (5.5%) and wind power (2.4%) being the main contributors.
NT’s electrical generation can be classified into (1) regulated network and (2) unregulated network which consists of off-grid, pastoral properties, mines, and other. The regulated networks of Alice Springs, Darwin-Katherine, and Tennant Creek  generated 1814 GWh in 2010-2011  with a total generating power of 522 MW. The unregulated network generated 1600 GWh with total generating capacity of 555 MW, of which mining sector generated 430 MW and 1230 GWh. These figures show that NT mining sector represents the largest electricity consumer within the unregulated network; on a territory level it also represents significant portion of the overall electricity consumption. In addition mining operations are among NT’s biggest consumers of fossil fuels with significant GHG emissions (BREE, 2013). Almost 99% of the electrical generation in the NT is fuelled by gas .
The NT is among the regions with richest solar energy resources in the world. The NT has an immense amount of solar energy throughout the year which remains largely untapped. To date, less than 1% of the Territory’s electrical energy generation (and consumption) comes from renewable source [6, 8].
With the above background, this paper explores the potential of CSP technology in supplying energy to the mining industry in the NT. NT has abundant solar energy resource and there have been success stories of the CSP technology in a similar environment elsewhere in the world which can be useful in realising this potential in the NT. There has been a recent initiative by the Australian Renewable Energy Agency (ARENA) to provide funding to deployment of solar PV systems to provide power to mining sites (e.g., ). An earlier initiative from the same agency has seen the allocation of significant funding “to deliver the next wave of cost reductions, novel technologies, know-how, publications and patents, and concepts ready for development and commercialisation” of the CSP . It is in the anticipatory spirit of the outcome of that latter that this research was conducted.
2. CSP Technologies and Prospects
This section presents an overview of the CSP technologies and their prospects being a precursor to the discussion on the feasibility study of CSP in the NT (Section 3).
2.1. CSP Technologies: An Overview
CSP technologies can be classified into (1) parabolic trough systems, (2) central receiver (tower) systems, (3) linear Fresnel systems, and (4) parabolic dish systems. Table 1 presents a summary of main features of various CSP technologies. This summary is used in this research to aid in selecting the relevant CSP technology under the relevant atmospheric, environmental, and economic conditions in this study. Detailed information on these technologies can be found in [14, 15].
As shown in Table 1, each technology listed has its own ranges of capacity, operating temperature, the type of power cycles and heat transfer fluids it can work on, water and land requirements, and so forth. The table also lists the advantages and disadvantages of each technology. All these factors must be taken into account when selecting the most appropriate technology for a particular site with its own environmental factors.
CSP systems, also known as solar thermal power plants (STPPs), are flexible to be hybridized with other renewable and conventional systems such as biodiesel fired boilers, wind, and photovoltaic systems. CSP technology is also capable of providing process heat for industrial applications such as water desalination at coastal freshwater-scarce utilities.
STPPs are capable of providing base load power to areas that have high direct solar insolation at costs similar to fossil fuel power generation but with significant reduction in greenhouse gas (GHG) emissions. In addition, power can be transported from insolation rich regions to insolation poor regions. For example, transportation of power to 3000 km is possible with only 11.5% losses using 800 kV direct current transmission technologies .
CSP systems are versatile and can be integrated with existing or new fossil fuel based power plants to curb the GHG emissions and to extend plant life to a low-emission energy future . Various CSP systems emit much lower GHG compared to conventional fuels (oil, gas, and coal) and roughly the same as the tidal, wave, and PV systems .
In order to ensure uninterrupted power supply necessary for mining operations, the CSP systems have to be supplemented with thermal storage. In addition, such systems are generally installed with fuel power backup capacity offering reliable power production to utilities and grid operators.
2.2. CSP Prospects
2.2.1. CSP Deployment Worldwide
The first solar thermal power plant became operative in Egypt in 1912 . CSP is considered a proven technology with CSP plants operating in California from 1984 to 1991 . Due to the steep decline in the prices of fossil fuels the support for CSP (including tax incentives and mandatory power purchase) was withdrawn by the government. CSP market reemerged in 2006 in response to the new government incentives such as feed in tariff in Spain and policies requiring utilities to include renewable power. This led to the construction of new CSP plants, raising the global stocks of CSP plants to nearly 1 GW in 2010 . Since then many other countries have invested in CSP with a projected increase in total capacity of up to 15 GW after the completion of the plants that are currently under construction .
According to NREL online database , to date 18 countries have constructed (or are constructing) CSP systems. The total installed capacity of all the 77 operational CSP plants is 3478.16 MW as of October 2013 (more than twice the capacity in 2012). Of these, 90% are parabolic trough systems, 8% linear Fresnel reflector systems, around 2% central tower systems, and less than 1% parabolic dish systems. Leading in terms of installed capacity are Spain (60%) and US (23%) while the remaining 17% is in other countries. Additional 17 GW CSP plants are under construction (20%) or under feasibility and planning stages with approximately half of these in the USA and another half in Spain and China .
2.2.2. CSP Deployment in Australia and the NT
Australia enjoys the position as the world leader in terms of solar resources and is contributing relatively well from a research and development point of view. A 100 kW CSP system called Step 100 was built in Meekatharra in WA in 1981-1982 . The system employed an Organic Rankine Cycle (ORC) system and operated for only a short time; hence performance data is limited. A 25 kW steam engine generator powered by a 14-dish system in White Cliffs in the New South Wales was designed by the Australian National University (ANU) and installation completed in 1981 . In 1998, this system was taken over by Solar Systems Pty Ltd. and converted to CPV receivers. However, later in 2008, despite the dishes remaining in fair condition, company decided to decommission the plant .
Another Australia’s research success was a solar dish with 500 m² aperture area designed and built by ANU in association with a commercial company, Wizard Power. The “Big Dish” was completed in 2009. The National Solar Energy Centre (NSEC) at Newcastle has recently commissioned a central tower plant in collaboration of joint funding by CSIRO. This plant has a 30 m central tower with 450 heliostats over 4000 m2 collector field for a 500 kW system . The aim of this research facility is to test solar reforming of natural gas and solar steam generating systems and to investigate solar Brayton cycle systems.
In Australia there are only 5 currently operating CSP systems with a total capacity of 5 MW. Few other research-based CSP projects are also underway .
It is estimated that a 10 GW capacity would be able to reduce Australia’s emissions by approximately 30 Mt CO2 per year which constitutes 15% of current electricity sector emissions. In addition, every 100 MW system is expected to create roughly 500 temporary construction related jobs and 20 ongoing operation related jobs. Last but not least, CSP technology offers to preserve precious natural resources which are being exploited for power production. This creates further opportunities for international trade of fossil fuel resources to the parts of the world which are less suitable and/or ready for renewable energy infrastructure. This study predicted that, considering the demand for dispatchable clean energy, CSP market potential would likely strengthen. According to the same study, CSP could provide 30% of Australia’s average total current electricity which is 15 GW .
Through ARENA, CSIRO is partnering with 6 universities in Australia, 2 universities in US, and the NREL in the Australian Solar Thermal Research Initiative (ASTRI) with the goal “to lower the cost of solar thermal power to 12 cents a kilowatt hour; targeting 20 cents a kilowatt hour by 2016 and 12 cents by 2020, whilst providing a power source that can be adjusted to demand (dispatchable generation)” .
For the NT, the Green Energy Taskforce  concluded that “while the costs for solar thermal are still high and the commercial scale is currently too big for the Territory to accommodate, it is approaching a stage where it could be deployed in the NT. It is considered that the best prospects would be in combination with gas generation (to overcome the intermittency).”
Considering the availability of high insolation in NT (see Section 3.2), the potential of STPP is not limited to remote mining sites; surplus power can also be transported locally and internationally, such as to neighboring islands of Indonesia through an intercontinental grid interconnection .
3. Feasibility Parameters of a CSP Plant
Based on the information presented in Table 1, there are 3 major groups of parameters that need to be considered in assessing the feasibility of a CSP plant installation in a location: (1) plant design requirements including auxiliary services, (2) environmental parameters, and (3) capital and operating costs. This section provides a brief insight into the nature of these parameters and complications associated with them in the context of mining industry in the Northern Territory, and specific examples are discussed in the following section.
3.1. CSP Design Requirements
3.1.1. Optimum Size of CSP Plant and Its Operating Life
One of the main criteria for a CSP plant is the ability to gain sufficient environmental and economic credits over its lifespan. Recommended size of plants varies for different CSP technologies as summarised in Table 1. Most of the commercial central tower plants built so far are in the range of 10–20 MW whilst the commercial parabolic trough plants in operation are in the range of 30–250 MW. All the commercial CSP plants which are currently in operation have a life between 20 and 35 years. Precise estimation of economically viable size of a CSP plant may require extensive modelling using specific design values for a certain location . As will be discussed in the following section, majority of the operating mines in the Northern Territory would have sufficient power load and lifespan to sustain CSP plant.
3.1.2. Operating Temperatures
Each of the four CSP technologies discussed in Section 2 generates electricity at different operating temperature (Table 1). Higher operating temperature can be achieved with the central tower systems or parabolic dish systems. This temperature can further be used to cater for some of the process requirements, for example, in minerals processing. High temperatures are achieved through the use of heat transfer fluids (e.g., CO2) in integrated solar combined cycle power systems . Most of the on-site ore processing does not involve high temperatures; however in some cases such integrated systems would be required.
3.2. Atmospheric, Environmental, and Other Requirements
According to Masters , the most suitable areas for CSP plants include North Africa, the Middle East, Sothern Africa, Australia, and the western side of South America. Rigorous analysis of the conditions in each of these locations reveals that the most crucial factors for CSP plants are the suitable direct normal irradiance (DNI), water availability, land topography, and low risk of extreme weather. Availability of backup power has also to be considered where it is important to ensure uninterrupted operations such as in mines.
The average DNI and the number of days of low DNI (cloudy days) at a location are used in calculating the solar multiple which is required to calculate the mirror area required . In addition, the number of complete cloud cover days at a location is very important in deciding whether a CSP plant is suitable for dispatchable power or only for peak load power and hybridization with other power generating systems . The minimum economically viable value for DNI is between 1800 and 2000 kWh/m2 per year [31, 32].
Figure 1 shows the contour of the average annual solar energy in Australia . As shown, most of the NT regions receive more than 2000 kWh/m2 annually (averaged over 2007–2012 period) with the Central Australia receiving over 2300 kWh/m2. This intensity is considerably higher than that of Spain, one of the world’s leading countries in solar power technology.
Even during the peak “winter” season in the NT, the mean daily solar radiation ranges from 5.3 kWh/m2