EuroSun2008-2

Solar potential for industrial processes

The integration of solar heat has a large potential in industrial applications, as the industrial sector covers about 28% of the total primary energy consumption for final uses in EU25. The recent study “ECOHEATCOOL” reports that about 30% of the total industrial heat demand is required at temperatures below 100 °C and 57% at temperatures below 400 °C [1]. As a matter of fact, in several industrial sectors, such as food, wine and beverage, transport equipment, machinery, textile, pulp and paper, the share of heat demand at low and medium temperature (below 250 °C) is about (or even above) 60% of the total figure [2].

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In the framework of the IEA Task 33 SHIP a solar potential study was carried out that surveyed all data available for solar thermal potential studies for industrial applications. This study showed that the figures on temperature levels applied in different sectors that are obtained from industry statistics are fully confirmed by the outcomes of the estimates done in the reported potential studies for solar process heat [3]. The result of this study shows the potential of solar heat (based on potential studies of selected countries) for EU25. Solar process heat could cover 3,8% of the industrial heat demand, corresponding to 100 - 125 GWth.

For Styria, a detailed potential study for the industrial sector was carried out in 2006 in the framework of the Styrian Promise project. Based on a questionnaire and via telephone calls over 470 companies were contacted to gather energy demand data and required temperature levels for processes. Based on the information acquired a statistical analysis was done to calculate the total energy demand of all Styrian companies in the respective sectors. To calculate the solar potential the following criteria were taken into account:

Process technical potential (improvement of technologies for low temperature applications)

Solar technical potential (efficiency of solar technology, available roof area)

Ecological potential (CO2/SO2 emission limits)

Social potential (awareness of companies)

Economical potential (investment costs, funding, conventional fuel and biogenic fuel prices)

Quantitatively it was only possible to account for the process technical and the solar technical potential, as the other factors are underlying regulatory agreements that rely on the current political framework.

For the process technical potential the following figures were assumed: (a) 100% for the food sector (all processes are low temperature processes), (b) 20% for the metal sector (conservative assumption, and strong reduction as low temperature process steps (phosphating, pickling etc.) may only account to a part of the overall energy demand of metal companies) and (c) 31% for the paper industry (reduction due to short residence times and partly necessary steam applications).

The solar potential was fixed with 20% for the whole industrial sector [4].

The results show that the total potential in the industry sector amounts to approximately 0,618 PJ/a. This equals an installed collector-area of 480.000 m2. It has to be considered that the potential in the textile and chemical industry was not included due to missing data. The largest potential in industrial companies was found in the sectors of food (0,2 PJ/a) and paper (0,28 PJ/a).

For trade companies a similar approach was used, however the process technical potential was always set to 100% as only low temperature is used in the relevant trade companies. Among commercial enterprises sports facilities (0,31 PJ/a), garden markets (0,13 PJ/a) and hospitals (0,12 PJ/a) have the highest potentials. The total potential in the commercial sector amounts to 0,587 PJ/a, which equals an installed collector-area of approximately 460.000 m2.

In total, the potential study for Styria shows that by installing a collector-area of approximately 1 Mio. m2, 68.000 t of CO2 per year could be saved.