
Concentrating Solar Industrial Process Heat
Focusing solar mirrors, as parabolic troughs or heliostats, concentrate sunlight to 30-2000 kW/m², convert it to heat and transfer it to a fluid in specific receivers at a temperature of 100 to 1000°C or more – well beyond hot water and low-grade steam. The levelized cost of heat depends on climate, system size and technology, 0.01..0.05 €/kWh (10.50€/MWh). Affordable thermal storage extends solar energy availability buffered to 24/7. The technology has been developed for concentrating solar power, implemented and proven in Gigawatts around the world.
Application areas are in district heating, food processing, ore treatment, wide range of industrial processes, due to storage capacity also in batch processes. Examples range from juice, dairy, beer, and laundry over refinery to roasting an synfuel. Last but not least, further products are electricity generation, combined heat and power, and absorption cooling.
Classic concentrating solar technology works with water, steam, organic fluid or air as heat transfer medium. Advanced receivers work with molten salt or ceramic particles feed. DLR has developed and demonstrated this technology in Europe and prepared commercial-scale systems with industry partners. For extended cloudy periods, high-temperature electrical heaters are implemented.

Solar Tower
In this context, DLR and European partners had prepared the HiFlex Technology (EU-project grant #857768) for a food processing plant with following features.
- innovative solar tower particle-based technology (DLR patent)
- inert ceramic solid particles (bauxite) as absorber, heat transfer and storage medium
- up to 1000°C, no freezing enables the techno-economic optimization of lower and upper fluid temperature
- 300°C to 1000°C results in very high storage density up to 2.5x the storage density of molten salt in solar tower plants, or 7x the storage density of molten salt in parabolic trough plants
- more efficient power cycles accounting for higher process temperature and improved efficiency in downstream process
The technology has been demonstrated at Jülich solar tower at demo scale (500 kW), and scaled up (2000 kW).
Solar energy for high-temperature processes is known, but still a novelty, and has giant potential to reduce emissions in industrial application at medium and high temperature. It will be implemented with appropriate thermal storage capacity. To fulfill clients’ needs, the business model will be for energy contracting, or heat-as-a-service, with the capital investment, construction, ownership and all operation and maintenance by specialized companies or consortia, leveraging financial, technical and performance risks.