Sarvesh Devraj
Concentrating solar power (CSP) technologies use different mirror configurations to concentrate the sun’s light energy onto a receiver and convert it into heat. The heat can then be used to create steam to drive a turbine to produce electrical power or used as industrial process heat. CSP, which is commonly termed as solar thermal electricity, has attained 110 MW global capacity addition in year 2016/17, bringing global capacity to more than 4.8 GW by year’s end (2017). Globally, the pace of CSP installations in 2016 was observed to be slow.
India has daily average 4–7 kWh/m2 solar insolation with daily average direct normal irradiance (DNI)1 of 4.3–4.54 kWh/m2 (Figure 1). With aggressive Government solar policies by the end of 2017, India is expected to achieve total installed capacity of 18 GW. It has been a great year so far, around 8.8 GW has been added in 2016/17. India is expected to become a major player in CSP by the year 2050 (Figure 2). The techno-commercial potential of CSP in India is believed to be more than 2,800 GW in India.
In the year 2010/11 capital cost for photovoltaic (PV) and CSP were 17 crore/MW and 13 crore/MW, respectively. Capital cost of PV for 2016/17 got reduced to 68% of its cost in 2010/11, but CSP capital cost reduced only 7% for the same period. High capital cost also increased the power generation cost leading to high CSP tariff in India (INR12/ kWh). Payback period for CSP projects is higher than the solar PV projects. There is need for competitive for smooth acceleration of CSP projects.
Apart from China, India was the only Asian country with CSP facilities under construction by the end of 2016. The major projects under construction in India include 25 MW Gujarat Solar 1 plant (with 9 hours of Thermal Energy Storage [TES]) and 14 MW National Thermal Power Corporation’s Dadri Integrated Solar Combined-Cycle (ISCC) plant, 23 (REN21). Only a few CSP projects in India were successful and barriers, such as DNI assessment, high capital cost, manufacturing infrastructure, policy push, etc., have been the key issues.
DNI Assessments
Accurate DNI estimation is very crucial for any CSP projects. The NREL solar DNI map (Figure 1) of Rajasthan and Gujarat have been calculated at value ~5.5–6 kWh/m2. Actual measured DNI on ground was different than the estimated value from satellites. For instance, Godawari Green Project in Rajasthan was India’s first commercial CSP project with 50 MW capacity. The company had reckoned yearly DNI of 1,825 kWh/m2 but the actual acknowledged DNI was 1,753 kWh/m2. This inaccurate estimation of DNI had created hurdles for engineers. To achieve 50 MW output, developers had to increase the field area of mirrors significantly, which increased total cost of project. Similarly, first demonstration solar tower project by ACME solar was installed in Bikaner, Rajasthan. Earlier 10 MW plant was proposed but due to overestimated DNI values, only 2.5 MW could be installed.
Issues such as DNI have risked the project and ACME had dropped all the expansions plans. Also, the problem of the desired output with existing solar fields became an issue.
