TPV

Thermophotovoltaics (TPV) is complimentary to Solar Photovoltaics but it operates at night and in cold climates
TPV is ideal for small and large scale Combined Heat & Power and it uses natural gas
TPV is lightweight and can be used as a battery replacement or in UAVs
TPV can be used in steel mills to convert waste heat into electricity 24 hrs per day 7 days a week and this is a huge market
JX Crystals IR cells in quantity are key to a large number of new applications

GaSb Cells and IR Power Beaming

Lewis M. Fraas & Han Xiang Huang
JX Crystals Inc, Issaquah, WA

TPV-8, Palm Desert, CA
November 2008

IR Power Beaming is an application where the system development is straight forward.  Eye-safe IR lasers are already available.  GaSb PV cells are ideal for low cost IR power conversion at power densities as high as 10 W/cm2 and at costs as low as 50 cents per W.  However, cost is controlled by production volume with high volume required (>5000 wafers per year).  Material costs are not important until production volumes approach 10 MW per year.

A novel TPV configuration will be presented that can fit into a standard home furnace cabinet. This system incorporates an externally faceted glass cylinder with a dichroic filter deposited on its outer surface and a GaSb IR cell array bonded to the outer surface on top of the filter. This cylindrical array is then surrounded with an envelope containing a low boiling point liquid for evaporative cooling. The liquid is in direct contact with the backside of the cell array. An air-cooled condenser is then mounted above the photovoltaic converter array. Evaporative cooling potentially allows a heat removal rate of 20 W/cm2. Additional novel features of this design are described. The goal is to design a cost-effective retrofit forced-air warm air furnace that can work either as a self-powered furnace or as a Combined Heat and Power appliance. In order to achieve low cost, the design point for the GaSb cell electric power density is 2.5 W/cm2.

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.

— Both solar cells and batteries generate quiet DC electric power. Infrared (IR) sensitive GaSb photovoltaic cells can convert energy from a combustion heated glowing ceramic IR emitter into electricity. The result is a lightweight thermophotovoltaic (TPV) battery replacement that operates day and night. We present here the design and operation of a first stand alone TPV generator. Test results on this unit have allowed us to design a scale-up hand-held 10% efficient 50 W TPV generator weighing 1.5 kg. The 50 W scale-up TPV power supply along with 1.5 kg of fuel has a projected weight specific energy density of 645 Wh/kg. This is 4 times larger than for a Li ion battery.

Light Weight Fuel-Fired TPV Battery Replacement

L Fraas1, J Avery1, L Minkin1, H She1, L Ferguson2
1 JX Crystals Inc, Issaquah, WA, USA
2 C12 Advanced Technologies LLC, Everett, WA,  USA

PVSEC-26 Singapore Oct 2016

Both solar cells and batteries generate quiet DC electric power and solar cells are light weight but conventional solar cells only operate when the sun is shining.  However, JX Crystals Inc (JXC) has invented and fabricates infrared (IR) sensitive solar cells that can convert energy from a combustion heated glowing ceramic IR emitter into electricity.  The result is a lightweight thermophotovoltaic (TPV) battery replacement that operates day and night. 
We present here the design and operation of a first stand alone TPV generator complete with a photovoltaic converter array and a burner / emitter recuperator assembly and support components. The package dimensions are: L = 300 mm (12”), H = 131 mm (5.2”), W = 96 mm (3.8”).  Its target performance is 25 W with a fuel burn rate of 500 W for an efficiency of 5%.  This unit is designed to operate with 465g propane or propane/butane fuel cylinders.

— 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.