Process Heat: the Solar Thermal Challenge of the Future

So far solar thermal technology is mostly used for domestic hot water, pool heating and room heating. It´s often forgotten that there is a huge demand for heat below 250 °C in industry, which can easily be reached with solar thermal collectors.

An international team of researchers working on behalf of the International Energy Agency estimated the realisable potential of solar process heat in the European Union at 100 GWth, which corresponds to 140 million m2 of collector area. T

Today, however, a solar thermal capacity of only 13.5 GWth is in operation across Europe. Task 33 of the International Energy Agency reported 85 solar process heat plants worldwide with a capacity of 27 MWth. However, this market segment seems to be waking up. Just recently, news about huge solar process heat installations did the rounds. There is the 13,000 m2 plant in Hangzhou, China, on the roof of the textile dyeing factory Daly Ltd., which is most probably the biggest installation for solar process heat in the world. The total investment adds up to RMB 12 million (€ 1.11 million) including the tanks and mounting system. According to the project developer, the Chinese company Shenzhen Quir Solar Technology Co., Ltd, the solar collectors will save RMB 3.38 million (€ 0.31 million) per year, so that the investment will pay off within 3 years. The hot water is provided at a low temperature of 55 °C. Secondly, this summer the German brewery Hofmühl GmbH in Eichstätt will start operating a pilot plant with 1,389 m2 of vacuum tube collectors, which will supply process heat between 90 and 140 °C to the brewing and cleaning processes. The owner of the system estimates a reduction of 20 % in the annual energy demand of the factory. The company is convinced that the investment will pay off and has plans for subsequent upsizing to 3,000 m2. The project is being subsidised by the German Federal Ministry for the Environment, Nature Conservation and Nuclear Safety.

What are the main topics for the future to open this new market sector?

1. In most cases solar thermal technology has to be fully integrated into the energy supply system of an existing production unit. Thus, planners have to analyse the process parameters even before starting the designing of the solar thermal device. Planning tools for certain industries and applications should be developed.

2. Payback times of 3 to 5 years are a must in the industry, so the specific investment costs have to drop drastically to reach such fast amortisations. “We have to reach specific solar system costs including the tank and mounting system of 300 to 400 €/m2”, says Werner Weiss, CEO of the Austrian Research institution AEE Intec and head of IEA task 33.

3. For most process heat applications high performance solar collectors and system components are needed. Thus, medium temperature collectors have to be developed, improved and optimised. So far, there are a handful of market-ready products of different types (see the following list) available and some development is taking place. There are four different types of medium temperature collectors. In the following, the companies with market-ready products are listed:

1. double glazed flat-plate collector with anti-reflective glass

ESE S.A., Belgium,

Schüco International KG, Germany,

2. concentrating flat-plate collector

Solarfocus (Kalkgruber Solar- und Umwelttechnik GmbH), Austria,

AOSol, Portugal,

3. parabolic trough collector

Solitem GmbH, Germany,

Button Energy Energiesysteme, Austria,

Industrial Solar Technology Corp., USA,

4. fresnel collector

PSE GmbH, Germany,


Further information:

Chinese planner of process heat installations: (only in Chinese)

IEA task 33 “Solar heat for industrial processes”:


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