Hydrogen from solar thermal energy: high temperature solar chemical reactor for co-production of hydrogen and carbon black from natural gas cracking


Contract Number : 019770 (SES6)
Project Officer: Rolf Ostrom
Contact person: Gilles Flamant
Duration : 4 years, starting from 1 March 2006.

List of Partners

  • CNRS-PROMES, France
  • ETH-Zurich, Switzerland
  • PSI, Switzerland
  • WIS, Israel
  • DLR, Germany
  • TIMCAL BE, Belgium
  • SOLUCAR R&D, Spain
  • CREED, France
  • N-GHY, France


CNRS-PROMES -1 MW Solar Furnace
Odeillo Font Romeu, France
September 28, 2009.

Download the AGENDA of the SOLHYCARB Event
(PDF file).

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Download the SOLHYCARB Final Publishable Executive Summary


The SOLHYCARB project addresses the development of a nonconventional route for potentially cost-effective hydrogen production and carbon nanomaterial synthesis by concentrated solar energy. The novel process thermally decomposes natural gas (NG) in a high temperature solar chemical reactor. Two products are obtained: a H2-rich gas and a high-value nano-material, Carbon Black (CB).
Therefore H2 and marketable CB are produced by renewable energy. The project aims at designing, constructing, and testing innovative solar reactors at different scales (5 to 10 kWth and 50 kWth) for operating conditions at 1500-2300 K and 1 bar.
This experimental work is highly combined with advanced reactor modelling, study of separation unit operations, industrial uses of the produced gas, and determination of CB properties for applications to batteries and polymers.
The design of decentralized and centralized commercial solar chemical plants (and hybrid plants) -50/100 kWth and 10/30 MWth respectively- closes the project.


The main scientific and technical challenges are: design and operation of high temperature solar chemical reactors (10 kWth and 50 kWth) containing nano-size particulates, production of two valuable products (hydrogen and carbon black) in the same reactor, proposition of a methodology for solar reactor scaling-up based on modelling and experimental validation. The reactor will operate in the 1500K-2300K temperature range that causes severe material issues. The production of both hydrogen-rich gas and carbon black with desirable end-use properties is also a big challenge because the operating conditions satisfying both specifications are probably narrow.

Project Structure

The project includes five main tasks.

1 - Solar reactor design and modelling.
Solar heating of natural gas cannot be achieved directly because hydrocarbons poorly absorb radiation in the visible spectrum. Thus, solar reactor concepts must involve either (1) opaque heat transfer walls that absorb solar radiation and then heat up the gas by gas-solid convection (indirect heating), or (2) a transparent window that permits direct heating of particulate material by solar radiation (particulate material can be CB). The indirect heating concept avoids particle deposition on the window, but it requires high temperature material specifications. Both concepts will be studied, in particular with respect to thermal resistance of materials (up to 2300 K) and to particle deposition on the optical window. At month 24, the solar reactor design to be modelled must be selected.

2 - Solar reactor testing and qualification.
Solar reactor testing will be achieved using the partners' solar facilities. First, various designs of receiver/reactor will be tested at small-scale (∼10 kWth). two different prototype-scale (5 kWth and 10 kWth) reactors based on the direct and the indirect heating concepts will be developed. These reactors (in operation at month 10) will be tested, and the experimental results will be critically analysed in order to define at month 24 the solar reactor concept that leads to the highest performances with respect to reactor thermal efficiency and maximal conversion of CH4 to H2.
This analysis will be strongly connected with the heat transfer modelling and the fluid dynamic analysis related to the carbon deposition problem. Based on the solar reactor concept retained at month 24, the 2nd step of the project will consist in designing, constructing and testing a 50 kWth pilot reactor (SR50).

The 2 key milestones of the project are:

  • (1) month 24: choice of the concept for SR50
  • (2) month 30: SR50 ready for operation and RTD activities focusing on SR50

Performance evaluation will include:

  • heat and mass balance (resulting in reactor thermal efficiency) in the 1500-2300 K operating temperature range
  • determination of conversion (80% CH4 conversion is targeted)
  • measurement of produced gas composition (H2 and CxHy)
  • CB characteristics vs. operating temperature
  • comparison with model predictions

3 - Product separation and process safety.
The separation of both the carbon nano-particles from the gas-solid flow and of hydrogen from the hydrogen-rich gas is a major issue that determines the uses of the produced gas (fuel cells, low emission combustion or injection in the NG network) and the associated safety problems. Adapted filtering media will be defined and installed at the test facilities. Gas separation routes will be studied as an associated unit operation. The device for filtering the gas-CB mixture and for separating H2 will be proposed at month 18.

4 - Characteristics and properties of produced carbon black.
A key point of the cracking process economics is the added value of the produced CB. The selling price depends on the product nano-structure and may vary from 0,6 €/kg for standard CB (used in tires) to 2 €/kg and even up to 30 €/kg for high grade conductive CB. Thus, the determination of CB properties is a very important issue of the project. It will include standard tests (specific surface area, particle size, chemical analysis, etc.), and application tests in the fields of polymer composites (rubber, plastics) and primary and secondary batteries.

5 - Industrial solar plant design and prospect.
An industrial scale solar plant will be designed on the basis of the reactor prototypes and the results of product testing, reactor modelling, separation unit operation, in addition to the existing tools for the design of solar concentrating systems. Typical industrial solar plant sizes of 50 kWth (decentralized units) and 10/30 MWth are targeted. The solar process economics will be assessed as a function of the uses of both products: hydrogen-rich gas and CB.

Expected Results

The targeted results are: methane conversion over 80%, H2 yield in the off-gas over 75%, and CB properties equivalent to industrial products. Quantitatively, 3 sm3/h H2 and 1 kg/h CB are expected at the 50 kWth scale. Potential impacts on CO2 emission reduction and energy saving are respectively: 14 kg CO2 avoided and 277 MJ per kg H2 produced, with respect to conventional NG steam reforming and CB processing by standard processes. The expected cost of H2 for large scale solar plants depends on the price of CB; 14 €/GJ for the lowest CB grade sold at 0.66 €/kg and decreasing to 10 €/GJ for CB at 0.8 €/kg.