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India: Process Heat System Monitoring Shows Fair Performance but Room for Improvement

Submitted by Baerbel Epp on August 12, 2016
Himachal Pradesh Dairy Case StudyThe SoPro India project has scientifically monitored two solar water heating systems for a year with the aim of presenting reliable data on system performance (see the attached PDFs). The measured 20 % solar efficiency would put the ROI between 2 and 3 years, depending on the development of fossil fuel costs. The researchers from German institute Fraunhofer ISE see new systems offering “good opportunities for further technical improvement.” SoPro was implemented by the German Agency for International Cooperation (GIZ) in cooperation with the Indian Ministry of New and Renewable Energy (MNRE).

India was the fourth-largest country for solar collector additions in 2015, although the market share of industrial applications remained below 5 % of the newly installed collector area. The project partners see “very high potential for greatly increasing the market size of the industrial sector, considering the relatively large heat demand in the low- and medium-temperature range throughout the year.” “Monitoring system performance is key to understanding the huge potential offered by the solar process heat market,” Gerhard Stryi-Hipp, Head of Energy Policy at Fraunhofer ISE, explained during a workshop on the project in March 2016. “In addition, it is needed to convince interested customers of the cost-effectiveness of this promising technology.”
Of the 27 visited solar process heat installations (see news piece), 15 were chosen for case studies based on the industrial owner´s willingness to support the project and deliver information. The case studies, which have been available on the project website, cover the following industry sectors: food and food processing (six installations), chemical (three), automotive (two), textile (two), and glass and refrigeration equipment manufacture (one each). The two systems that Fraunhofer ISE selected for extensive monitoring pre-heat the feed water of steam boilers and are located at pharmaceutical producer Synthokem Labs, Hyderabad, southern India, and Himachal Dairy Products, Rampur, northern India (see the table below).


Synthokem Labs

Himachal Dairy Products

Collector type

Evacuated tube collectors

Flat plate collectors

Collector field size

Two fields of 62.6 m² each

120 m²

System type

Non-pressurised, open system

Non-pressurised, open system

Water storage size

Two 5,000-litre storage tanks

6,000 litres

Solar irradiance on collector area

1,789 kWh/m²*a

1,404 kWh/m²a

Specific collector yield

408 kWh/m²a

417 kWh/m²a

Solar collector efficiency

25 %

30 %

Solar system efficiency

20 %

20 %

Solar share in total fuel demand

1.5 %

1.4 %

Total investment (in Indian Rupee [INR])



Fuel cost saving

345,000 INR/a
(INR 50 per litre of fuel)

217,000 INR/a
(INR 52 per litre of fuel)

Simple payback period without subsidies

2.5 years

7.7 years (4 years including Central Financial Assistance of INR 792,000)

Selected monitoring data from the two case studies; boiler efficiency was assumed to be 70 %.
Source: or attached PDFs
Both systems achieve a 20 % solar system efficiency, which is a lower-end figure considering that one could expect efficiencies of between 20 and 40 %. However, the payback period of 2.5 years for the Synthokem Labs system and 4 years, including subsidies, for the dairy producer installation show that the systems perform to the satisfaction of the investors. The researchers do not see an urgent need to change the system design, but recommend some alterations for new solar process heat installations:
Synthokem Labs: As the energy demand for hot-water heating is much greater than the energy delivered by the entire solar system, it would be ideal to connect the existing but separate collector fields to one of the water storage tanks. This would also avoid losses originating from the second tank. At present, the return line of the collector circuit is located on the top of the storage tank, aiming to provide stratification. But since the feed water is removed from the bottom, it would be more efficient to mix it continuously. This could be achieved by simply connecting the return line of the collector circuit to the bottom of the storage tank. In general, temperature stratification is not desired in open systems.
Himachal Dairy: The measured return temperature transmitted from the heat exchanger to the storage was quite high, resulting in an inefficient transfer of heat from the solar circuit to the industrial process. The temperature could be reduced, e.g., by optimising the flow on both sides of the heat exchanger. The other important point is to ensure a continuous flow of heat transfer fluid throughout the entire collector field. This could be jeopardised by air trapped in the circuit because of missing air vents or in case the flow parameters are not the same across all collector circuits set up in parallel. The researchers recommended to further evaluate these two aspects.
Improve economics and increase attractiveness to industry customers
Based on the experience gathered during the SoPro India project, its implementers suggested additional intervention to ensure better system performance and continue increasing the system’s economic attractiveness. For example, they recommended to prepare system design guidance based on standard applications, develop the corresponding monitoring strategies to quantify gains, assess operational issues, and adapt open-source planning software in order to create optimal design specifications as well as inform customers on expected energy yields.
“The SoPro India project findings are important as on one hand potential customers can see the cost-benefit of installing such systems while on the other hand, we know that by taking certain measures, we will be able to enhance the economics further thus increasing attractiveness for industry consumers,” said Shri Sohail Akhtar, Adviser (Solar Thermal Division) at the MNRE. In particular, the ministry and the Solar Thermal Federation of India (STFI) agreed to jointly develop design and installation guidelines as well as planning software, in order to assist the sector in realising efficient solar process heat installations. 
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