Case study in CSP plant performance

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Using routine sampling and chemical analysis of heat transfer fluid, early in a plant build, can help to extend the lifetime of CSP plants. Christopher Ian Wright BSc PhD MBA, explains.

Concentrating solar power (CSP) is a proven technology for electricity generation [AIS]. CSP plants generate electricity by transforming heat into mechanical energy using a steam turbine [1]. Since 2005 this sector has grown [2]. In 2008 CSP plants accounted for roughly 430 MW of the electricity generated globally [2]. The Australian Institute estimated that this was growing at a rate of roughly 40% per year and is projected to reach 20 GW of electricity being generated globally by 2020 [3]. In terms of the percentage of energy from CSP, it has also been estimated that it will contribute around 7% of the global power supply by 2030 and 25% by 2050 [2]. The factors driving these projections are varied and involve many PESTLE factors such as the price of oil, sustainable and secure energy supplies, rising pollution, greenhouse gases targets and the emergence of clean energy technologies [3].

With these forecasts it is no surprise there is a growing number of CSP installations with plants in Spain, South-West USA and India [1], and the possibility of CSP plants being built in the Middle-East and North Africa, Australia and South America [2, 3].

Fernandez et al. [4] investigated the corrosion properties of a ternary nitrate/nitrite molten salt in concentrated solar technology, and emphasised the importance of choosing the right heat transfer fluid (HTF). For The Jawaharlal Nehru National Solar Mission, the parabolic trough power plant was filled with a synthetic HTF with a eutectic mixture of diphenyl oxide and biphenyl [1]. This HTF provides an operating range between 12 and 400 degrees Celsius [1, 5].

Other factors to consider are the costs associated with operating and maintaining a CSP plant. Fernandez et al. [4] mentioned three areas where improvements are needed to increase the profitability of CSP plants. These were: i) to reduce investment in CSP plants, as well as to reduce operational and maintenance costs; ii) to increase the temperatures in the thermal cycle as well as increasing the lifetime of the power plants; and, iii) to extend operation time and thereby extend the period over which energy can be supplied.

Past research has suggests that the condition of a HTF is influenced by the frequency that it is sampled and chemically analysed (SACA) [6]. This research demonstrated the importance of routine SACA and the need for an ongoing maintenance plan. This could be of benefit to CSP plants looking to reduce operational downtime, to spread the cost of maintenance plans and to extend the lifetime of the CSP plant.

This report presents the data from a case study where a plant was filled with a synthetic HTF with a eutectic mixture of diphenyl oxide and biphenyl [5], as is commonly used in a number of CSP plants. This case demonstrates the importance of SACA during the building of plants as well as on an ongoing basis.

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