Direct conversion of solarenergy in hydrogen
So far, in solar hydrogen generation PV modules are coupled via a dc
interface with a central electrolysis unit. The aim of the joint project
"HyCon" was therefore a radical simplification of the system by using
novel integrated approach. To this end, in a concentrator High Efficient
III- V multijunction solar cells are connected directly to an
electrolysis cell. In tis way, still unmatched conversion efficiencies
of sunlight into hydrogen more than 20 percent can be achieved.
|Project status||Project completed|
|Project duration||December 2013 until September 2016|
Using of renewable electricity, hydrogen can be produced by the electrolytic water splitting CO2 neutral. In conventional solar hydrogen generation system, PV modules are coupled via a dc interface with a central electrolysis unit. Disadvantages of this approach are a relatively complex system structure and high investment costs. Due to the high hydrogen production costs this technology has been unable to enforce. The objective of this joint project is therefore a radical simplification of the system by a new, integrated approach. Highly efficient III-V multijunction solar cells under concentration are connected directly to an electrolysis cell. In this way, still unmatched conversion efficiencies of sunlight into hydrogen > 20% can be achieved.
Research will include the following areas
- Development of an optimized system design by use of simulation tools for the analysis of a passive water supply and the gas transportation
- Optimal adaption of the two subsystems, photovoltaics and electrolysis, through the development of new III-V multijunction solar cells, whose characteristics are optimally adapted to the characteristics of the hydrogen generator
- Verification of the results on a tracked HyCon concentrator system under realistic conditions
- Development and adaptation of materials and components such as membrane electrode and flow field plates to the special requirements of solar hydrogen production, while reducing manufacturing costs and a required extrapolated lifetime of the components of> 40,000 h
- Analysis and identification of the critical degradation mechanisms in the electrolytic cell, from the viewpoint of the fluctuating sunlight
Conversation effiency over 20 percent
At Fraunhofer ISE efficient solar hydrogen production research is being conducted for more than 20 years. Due to the significant progress in the area of III-V solar cells for commercial terrestrial applications, solar cells, which are in principle suitable for this innovative technology approach are available. In previous work, the technical feasibility could be demonstrated by a first laboratory set-up. Record efficiencies of 18% have already been achieved for the conversion of sunlight into hydrogen. The conversion efficiency shall be increased in this project to over 20%.
The width of the scientific questions in this research tasks - from fundamental issues in materials research to complete system solutions - requires an interdisciplinary collaboration between university and non-university partners. The project consortium is in this case composed of the Fraunhofer ISE and ICT, IMTEK Freiburg and ICVT Stuttgart.
Based on already existing models for the analysis of the cost of PV systems and electrolyzers a combined cost model for a HyCon model is set up. It allows a so-called "cost breakdown" to calculate the material and manufacturing costs of components of the HyCon system and also allows the determination of the hydrogen production costs.
Project phases untill November 2015
The project is the first phase, in which an overall concept is developed and the first target costs are defined for the main components . The following milestones shall be achieved in the project:
- Project month 9 : System analysis is performed and first target costs for the major components of the system HyCon are defined.
- Project month 16: GaInP / GaInAs tandem concentrator solar cells for first prototype are produced in the laboratory and characterized. Beginning of the development of an optimized multi -junction solar cell structure for the final HyCon design
- Project month 16: Materials (membrane, electrode) are characterized for the first prototype and are available. First characterization of the material properties optimized for demonstrations have begun.
- Project month 19: Simulation of the HyCon single cell are completed.
- Project month 27: From degradation investigations improved durability are proven to optimized materials.
- Project month 33: Final HyCon system is completed and in testing and characterization ( field test).
- Project month 33: Detailed cost analysis for HyCon system is completed , including evaluation of the future potential of this technology.
Subproject Fraunhofer ISE/ICT: This subproject includes the preparation and characterization of membrane-electrode assemblies, electrolysis cells and III-V solar cells. The solar cells should be optimized with regard to the current yield. With respect to the electrolysis cell, cost and long-term stable catalyst materials should be synthesized, and in particular examined according to their activity and stability. In addition, a concept containing an ideal combination of the individual components should be developed and a demonstrator should be built. The demonstrator should be tested under real conditions in Freiburg.
Subproject IMTEK Freiburg: This subproject includes three-dimensional geometric reconstruction of single components. From the 3D samples geometry certain material parameters are to be extracted, which are incorporated into a system simulation of HyCon-cell and module.
Subproject ICVT Stuttgart: In this subproject, novel long-term stabile polymers and membranes are going to be developed. The manufacturing process is intended to be cost-effective and therefore reduces the total system cost. In order to verify the long-term stability of the materials, both ex-situ and in-situ characterization methods have to be applied.