Thermophotovoltaic (TPV) Breakthrough
As a bit of history, the Company previously spent about $20M and three years effort together with a number of PV manufacturers, engineering firms, specialty materials firms, universities, NREL, inductively coupled heating firms, analytical services companies, coating companies, specialty fabricators, cooling technology firms, vendors, and consultants towards the two goals of (i) developing a 3000K blackbody radiator heated by the SunCell and (ii) converting the emission to electricity using concentrator photovoltaic (PV) cells in a dense receiver array. The platform for the 3000K emitter was a SunCell® comprising molten silver. The silver system was challenging in that it required operation of all components above 1000°C, and achieving 3000K proved challenging due to materials limitations. So, we focused on developing a competitive thermal solution that comprised a low-melting point molten metal. The gallium system that starts up at about room temperature served as a rapid test station for hundreds of designs, parameters, and conditions. We have advanced to achieve continuous working systems capable of generating between 100-300kW of power depending on the operating temperature by our new power source at a remarkable power density of 5-10 MW/liter. Cooling technology was developed to achieve continuous steam production at a scale of 250 kW with increases anticipated. The thermal systems were independently validated and shown to work flawlessly off-site on demand. Commercial boiler and air heat exchangers are being tested.
With success of the thermal technology, we are revisiting all electric conversion technologies searching for advancements and new opportunities to convert the power from the SunCell® to electricity. We have an OEM quote on a 900-kW combined heat and power microturbine system, and MHD technology is being pursued. We are also revisiting TPV. One intriguing development of our prior TPV program was the impact of recycling infrared light that was below the band gap of the PV converter. Specifically, expert analysis at a leading engineering university had indicated that 3000K incident light that was not converted to electricity by the PV cell could be reflected back to the blackbody radiator, absorbed, and re-emitted as part of the spectrum comprising PV active light resulting in a remarkable efficiency of 84%. This could be achieved even with silicon concentrator PV cells operating at high temperature which permitted simple cooling systems. Given the guidance from PV design experts that 3000K was required in order for TPV to be practical, the problem left was still how to get to 3000K when even 2000K was difficult. A subsequent publication in PNAS demonstrates that light recycling has a radical impact! Experimentally, the emission from a 1200°C blackbody emitter was successfully converted to electricity at 30% efficiency using a single junction PV cell. Moreover, with improvement in emitter and PV cell design, the authors project 50% conversion efficiency can be achieved. The conversion efficiency is known to increase with blackbody temperature and with light intensity or concentration. Running the SunCell® at 1200-2000°C is well within reach. Moreover, we are testing a new approach wherein 3000+ emission was achieved more simply. These recent developments have dramatically changed the prospects for near term, autonomous, pollution-free, inexpensive SunCell® electrical power for essentially all power applications.
[See Business Presentation and Overview Business Presentations].