Spectral control development for thermophotovoltaics
Gallium Antimonide (GaSb) infrared photovoltaic cells are light weight whereas batteries are heavy. The specific energy in a hydrocarbon fuel is high at 12,900 W-hr per kg but a lithium ion rechargeable battery has a specific energy of only 145 W-hr per kg. A 10% efficient portable lightweight thermophotovoltaic (TPV) cylindrical generator when compared with a battery can have 6.5 times higher specific energy, operates 7 times longer, and be quickly refueled. The key is the 10% efficiency goal. This efficiency goal depends on matching the spectrum from a combustion heated ceramic IR emitter to the response band of the IR PV cell. Herein, spectral measurements are presented for a propane burner and ceramic IR emitter assembly surrounded by a fused silica glass envelope. The cylindrical IR ceramic emitter consists of an array of NiO doped MgO rods or slats. The Ni ion emission line is centered at 1.6 microns and it matches the GaSb IR response band extending out to 1.8 microns. The ceramic IR emitter is combustion heated to approximately 1200 C. The fuel and air combustion efficiency and hot gas coupling efficiency to the IR emitter are also important parameters.
Burner, emitter, and recuperator development for lightweight thermophotovoltaic power supply
Like batteries, thermophotovoltaic generators produce DC electricity quietly. TPV uses infrared photovoltaic cells to convert infrared radiation from a combustion heated ceramic IR emitter. However, because the specific energy in a hydrocarbon fuel like propane or butane is 12,900 Wh/kg, much larger than the specific energy of 145 Wh/kg for a Li-ion battery, TPV is very promising as a lightweight DC power supply. A portable cylindrical thermophotovoltaic (TPV) battery replacement concept has been previously described. It consists of a cylindrical TPV receiver assembly using simple diffused junction GaSb IR cells along with a novel omega recuperator and a novel doped ceramic matched IR emitter. For high energy conversion efficiency, it is very important to match the IR spectrum emitted with the IR PV receiver cells. While the GaSb IR cells have been previously demonstrated, development and demonstrations of the omega recuperator and the IR matched emitter are described for the first time here. The matched IR emitter consists of NiO doped MgO ceramic rods arrayed in a 26 mm diameter picket fence configuration. A burner, emitter, and recuperator test station is described consisting of this picket fence emitter heated at up to 1300 C by propane combustion along with an omega recuperator to preheat the combustion air. The emitted IR intensity is measured with a single GaSb test cell. Given a TPV conversion efficiency of 10%, this lightweight TPV cylinder along with 1.8 kg of fuel promises a very high specific energy of approximately 700 Wh/kg. This specific energy is 5 times higher than the specific energy for a Li-ion battery with a similar power rating making this TPV unit very lightweight. The key is the goal of 10% system efficiency. Progress towards achieving this goal is described here.
A Preference for Forgetting: Some Reflections on Publishing Looking For Blackfellas' Point: An Australian History of Place
Blackfellas' Point lies on the Towamba River in south-eastern New South Wales. As the river descends rapidly from its source on the Monaro plains, it winds its way through state forest, national park and farming land. Around twenty-five kilometres before it reaches the sea, just south of Eden, it passes through Towamba, the small village in which Mark McKenna now owns eight acres of land. Mark's land looks across the river to 'Blackfellas' Point', once an Aboriginal camping ground and meeting place. Looking for Blackfellas' Point is a history that begins by looking across the river to the arc of bush that is 'Blackfellas' Point. From there, Mark McKenna's gaze pans out - from the history of one place he knows intimately, to the history of one region and, ultimately, to the history of Australia's quest for reconciliation between Indigenous and non-Indigenous Australians. Looking For Blackfellas' Point is a history for every Australian who is interested in the story of settler-Australia's relations with Indigenous people - what happened between us, how we learnt to forget and, finally, how we came to confront the truth about our past and build a movement for reconciliation.