The background on the development of solar thermal energy and the role of solar heat for industrial processes was shortly summarised in the Work Plan of the Task 33/4: It is expressed that around 60 million square meters of solar thermal collectors were installed in total by the year 2000 in the OECD countries. Until now the widespread use of solar thermal plants has focused almost exclusively on swimming pools, domestic hot water applications and space heating in the residential sector. Between 1994 and 2000 average growth rates of 18% were attained each year for these applications in Europe.

But the use of solar energy in industrial process applications is currently insignificant compared to the applications mentioned before. Most solar applications for industrial processes have been on a relatively small scale and are mostly experimental in nature. Only a few large systems are in use world-wide.

On the other hand, if one compares the energy consumption of the industrial, transportation, household and service sectors, then one can see that the industrial sector has the biggest energy consumption in the OECD countries at approximately 30%, followed closely by the transportation and household sectors.

Caused by the fact that energy is available at low cost and without limitations, industry did not care too much about energy efficiency and substitution of (fossil) fuels. The main activities in this field started in 1973 and 1979/80 following the two oil (price) crises. Later on, oil prices — and related to that the prices for natural gas and electricity — fell again. Today — even in the critical political situation in the Middle East — energy prices are low.

On the other hand, it is obvious that fossil resources are finite and alternatives have to be found for all applications, including the use in industrial applications.

The major share of the energy which is needed in commercial and industrial companies for production processes and for heating production halls, is below 250°C. The low temperature level (< 80°C) complies with the temperature level which can easily be reached with solar thermal collectors already on the market. The principles of operation of components and systems apply directly to industrial process heat applications. The unique features of these applications lie

• on the scale on which they are used,

• on the special system configurations and controls needed to meet industrial requirements,

• and on the integration of the solar energy supply system with the auxiliary energy source with respect to the industrial process itself.

For applications where temperatures up to 250°C are needed the experiences are rather limited and therefore also suitable collectors, components and systems are missing. Therefore, for these applications the development of high performance solar collectors and system components is needed.