Download micro TPV - National University of Singapore

Faculty of Engineering
Mechanical Engineering
Development of Micro Thermophotovoltaic
Power Generators
To increase the efficiency of the micro TPV power generator, we use a
simple nine layer dielectric filter made of Si and SiO2, which is able to
recycle photons with wavelengths between 1.7 to 3.5 micron.
Today, even with the miniaturization of functional elements of electronic and mechanical
systems, power sources and batteries remain the largest and heaviest component of
most systems. Recent development of wireless micro systems has also reached a
bottleneck; constrained by the need for a tiny and powerful energy source. This scenario
is driving the emergence of a new class of micro power sources or power MEMS. The
micro thermophotovoltaic (TPV) power generator is one type of power MEMS attracting
increased attention because it has no moving parts, is highly robust and reliable, and is
suitable for use in commercial electronics and personal micro devices.
Operation and development
of the TPV system
Quantum efficiency of GaSb PV cells
A prototype micro TPV power generator
The micro TPV power generator employs
an array of PV cells to convert energy
radiation from the combustion of fossil or
hydrocarbon fuel into electricity. Fuel is
burned in a micro combustor, which acts
as an energy emitter. Radiation is
captured by the PV cell, which converts
the energy into electrical energy.
A prototype micro TPV power generator has been assembled and tested
for the first time. An electrical power output of 2.5 W has been achieved
from the system, when flow rate of H2 is 4.5 g/hr, and the H2/O2 ratio is 0.8,
The open-circuit voltage and short circuit current are 2.3V and 1.43A,
respectively. However, the development of the micro TPV system is still at
an early stage. A suitable selective emitter and lower band gap PV cells
will need to be developed to further improve its efficiency.
2.5
1.8
1.4
1.2
1.5
1
0.8
1
0.6
0.5
open circuit voltage
0.4
short circuit current
maximum output power
0.2
0
0
0
0.2
0.4
0.6
0.8
1
H2/O2 ratio
Glow of combustor
Temperature distribution
on the axial plane
PV cell is another important components of the micro TPV system. Owing to the relatively
lower temperature of radiation source, to maximize the output power density, low band gap
PV cells are employed, In this micro TPV system, a GaSb PV cell with an band gap of 0.7
eV, which responds up to 1.7 micron, is employed.
A prototype micro-TPV power
generator
The performance of micro-TPV
Contact: S.K. Chou E-mail: [email protected]
1.2
Current (A)/Power (W)
1.6
2
Voltage (V)
The micro combustor is the heart of the micro
TPV system. Its role is to reach a high and
uniform temperature distribution along the
wall of the micro combustor. 3-D numerical
simulation indicates that a micro cylindrical
combustor with a backward facing step is a
simple and efficient combustor for micro-TPV
application. Experimental testing indicates
that an average temperature of 1540 K can
be achieved along the wall of a micro SiC
combustor 3 mm in diameter.
Reflectance of a simple nine layer filter