Report

Teaser, summary, work performed and final results

Periodic Reporting for period 3 - ThforPV (New Thermodynamic for Frequency Conversion and Photovoltaics)

Teaser

In the past period, we described and demonstrated the new thermodynamic concept for solar energy harvesting called Thermally Enhanced Photoluminescence (TEPL) in few major publications (The Nature Communication 2016 paper was chosen by the Optical Society of America as the...

Summary

In the past period, we described and demonstrated the new thermodynamic concept for solar energy harvesting called Thermally Enhanced Photoluminescence (TEPL) in few major publications (The Nature Communication 2016 paper was chosen by the Optical Society of America as the most important publication in solar energy for the year 2016). However, all these demonstrations were done with poor material quality. The quantum efficiency at high temperatures was very low, eliminating the practicality of the concept.
In this past year, we worked to improve the material quality, and in a recent paper, we demonstrated 20% of the incoming energy to be coupled to GaAs.
Recently, we solved the material issue by demonstrating 90% quantum efficiency while the crystal is operating at 600C. This is still unpublished.

Recently we found a more practical configuration for TEPL:

The challenge in solar energy today is not the cost of photovoltaics (PVs) electricity generation, already competing with fossil fuel prices, but rather utility-scale energy storage costs. Alternatively, low cost thermal energy storage (TES) exists, but relies on expensive concentrated solar power (CSP). A technology able to unified PV conversion with TES may usher in the era of efficient base-load renewable power plants.

Conceptually, if PVs efficiency would tolerate high temperatures, for example, 600C, it would be beneficiary to concentrate solar radiation onto PVs, harvesting the available free energy, while in parallel harvesting the high-quality thermal energy through CSP. Doubling the conversion efficiency this way cannot be done with PVs as their efficiency decreases sharply with temperature, but can be done optically.

Recently, we presented and demonstrated a new concept named luminescence solar power (LSP), where solar radiation is focused onto a photoluminescence (PL) absorber that absorbs the light, take the heat and emit “cold” radiation towered a PV. The emission has a narrow line shape that matches the band-edge absorption of a dual-junction PVs, which offers concentrated-PV above 35% efficiency with minimal heating of the PV. The heat remains at the PL-absorber at 600C, collected by heat transfer fluid (HTF) and converted to electricity at 40% turbine efficiency. Such an idea of using PL to separate free-energy (electricity) and high temperature heat has never been explored before, even though each component of the system, namely the CSP, PVs and the PL-absorber relay on mature technologies. A detailed analysis based on experimental validation of the concept in the lab shows that practical LSP efficiency may reach 32%, far exceeding conventional side-by-side PV/CSP efficiency, and leading to a potential reduction of solar energy storage levelized cost of electricity (LCOE) to below ¢3/kWh. According to SunShot estimations, baseload solution at 3 ¢/kWh will allow solar energy portion to reach 50% of the entire EU production.

Based on this new concept, we are moving to commercialization. We submitted an ERC-POC grant as well as additional funding (Answers will be given in the next few weeks). We aim to demonstrate CSP receiver with 50% enhanced efficiency operating in real environment within 18 months. A team including Dr. Assaf Manor (Former PhPh.D.tudent and the 1st author in the relevant ERC papers) together with Mechanical and system engineers started working on the device. It is expected that once the device is demonstrated, and based on external investments, this team will be the backbone of a startup company, aiming to full commercialization.

Work performed

In the past period we described and demonstrated the new thermodynamic concept for solar energy harvesting called Thermally Enhanced Photoluminescence (TEPL) in few major publications (The Nature Communication 2016 paper was chosen by the Optical Society of America as the most important publication in solar energy for the year 2016). However, all these demonstrations were done with poor material quality.
The quantum efficiency at high temperatures was very low, eliminating the practicality of the concept.

In this past year, we worked to improve the material quality, and in recent paper, we demonstrated 20% of the incoming energy to be coupled to GaAs in the paper:
N. Kruger, A. Manor, T. Sabaphati and C. Rotschild, Thermally enhanced photoluminescence: from fundamentals to engineering optimization, Emerging leaders, Journal of optics, (2017), http://iopscience.iop.org/article/10.1088/2040-8986/aab87c/meta.
This paper is part of “ A focus edition in Journal of Optics mirroring the Journal of Physics Series\' 50th anniversary celebratory initiative. Emerging Leaders special issues are aimed at recognizing the next generation of leaders within a research community. “
Additional academic activities related to the project in this period includes:
Awards:
Krill prize-granted by the Wolf Foundation for Excellence in Scientific Research.

Invited Talks:
C. Rotschild, Thermally Enhanced Photo-Luminescence: Device, QUANTSOL, Austria, 2017
N. Kruger, A. Manor, T. Sabaphati and C. Rotschild, Thermally Enhanced Photo-Luminescence solar conversion prototype design. Accepted to SPIE 2018.
C. Rotschild, Photoluminescence: An optical heat pump for solar energy, MIT energy club, 2017.
Conference talks
T. Sabapathy, C Rotschild, Thermally enhanced photoluminescence in low band gap materials for conversion of industrial waste heat to electricity, accepted to SPIE 2018.
Conference activities:
2018- Member of the organizing committee QUANTSOL, Austria, 2018.
Grants:
ERC-PoC ThforPV - REP-SCI-638133-1 submitted.
Patent: on the technology developed as part of the ERC project, submitted  


Recently, we solved the material issue by demonstrating 90% quantum efficiency while the crystal is operating at 600C. Figure 1 shows our unpublished material optimization.

Cr:Ce:Nd, and Cr:Nd:Yb in YAG matrix (Fig. 1a) emit optimal PL spectrum at high temperatures. Figure 1c analyses the PL against Si and GaAs (blue and green lines), compared to direct illumination of GaAs and Si (dotted red line), which drastically falls with temperature rise. These unpublished results change dramatically the potential of our concept and its target for commercialization. Instead of using a single high bandgap-PV, we propose a combination of low and high bandgap-PVs. Due to practical considerations, such method has a great potential. First, the sub-bandgap emission compared to GaAs is harvested by Si or GaInNAs (1eV bandgap) solar cell. As depicted (blue & green lines in Fig. 1c), the expected efficiency based on our preliminary results reaches 40% at temperatures of 600C. Second, as far as we know, TEPL is the only method for CPV where a cooling system is not required or minimally required, which is a major cost reduction. Third and most important, at 600C heat engine efficiency reaches 35%. These observation suggest that our concept can have real impact in
Combined CPV-CSP on a single thermally enhanced luminescent crystal for delivering storable energy at record low costs
The biggest challenge in solar energy today is not the electricity generation price, which is already under fossil fuel price for photovoltaics (<0.04 $/kWh), but rather the ability to store utility-scale electricity in competitive prices. To date, the only practical method is Thermal Energy Storage (TES) which is combined with Concentrated Solar Power (CSP). Despite its past decline, demands for CSP are increasing wherever dispatchable generation is required, even though current CSP pri

Final results

Based on our new unpublished results, we are moving to commercialization. We submitted an ERC-POC grant as well as additional funding (Answers will be given in the next few weeks). We aim to demonstrate 300mmX300mm 50KW CSP receiver with 50% enhanced efficiency operating in a real environment within 18 months. A team including Dr. Assaf Manor (Former PhD student and the 1st author in the relevant ERC papers) together with Mechanical and system engineers started working on the device. It is expected that once the device is demonstrated, and based on external investments, this team will be the backbone of a startup company (name LUMINESCENTPV), aiming to full commercialization.

Website & more info

More info: https://excitonics.net.technion.ac.il/.