Background Information•Harvesting energy from renewable sources offers a method of providing power at remote locations using local resources. •Overall system efficiency of Stirling engines can outperform silicon based photovoltaic systems in many cases. •Stirling cycle generators can use any heat source to produce electricity, such as solar radiation, geothermal or waste heat sources, or even simple combustion of waste biomass.

Background Information•Harvesting energy from renewable sources offers a method of providing power at remote locations using local resources. •Overall system efficiency of Stirling engines can outperform silicon based photovoltaic systems in many cases. •Stirling cycle generators can use any heat source to produce electricity, such as solar radiation, geothermal or waste heat sources, or even simple combustion of waste biomass.

Stirling Cycle•The Beta Type Stirling Engine consists of one cylinder containing a displacer piston and a power piston , coupled to a flywheel.•The working fluid on the far side of the cylinder is heated by an external heat source and the opposite side is cooled by a heat sink. •As the working fluid on the hot side expands, it pushes the power piston towards the cold end of the cylinder. •On the cold end the gas contracts , pulling the power piston back towards the hot side. •The displacer piston acts as a shuttle, moving hot gas towards the cold side and vice versa. The power piston and displacer piston rods are linked to the flywheel 90 degrees out of phase, producing output power.

Stirling Cycle•The Beta Type Stirling Engine consists of one cylinder containing a displacer piston and a power piston , coupled to a flywheel.•The working fluid on the far side of the cylinder is heated by an external heat source and the opposite side is cooled by a heat sink. •As the working fluid on the hot side expands, it pushes the power piston towards the cold end of the cylinder. •On the cold end the gas contracts , pulling the power piston back towards the hot side. •The displacer piston acts as a shuttle, moving hot gas towards the cold side and vice versa. The power piston and displacer piston rods are linked to the flywheel 90 degrees out of phase, producing output power.

System Implementation

AcknowledgmentsDr. Alan RaisanenMr. Robert KraynikMr. David Hathaway

Stirling Engine DesignAssumptions:•10% efficiency between the parabolic reflector and engine output (1300 W/m2 exerted by the sun)•50% efficiency between the generator input and USB output•Beale number of 0.15•Operating speed of 1000 rpmResulting design targets:•200 Watt solar power collected•20 Watt mechanical output•10 Watt electrical outputResulting Values:•Mirror collection area of 1.658 ft3 •Displaced fluid volume of 6.39 in3

Stirling Engine DesignAssumptions:•10% efficiency between the parabolic reflector and engine output (1300 W/m2 exerted by the sun)•50% efficiency between the generator input and USB output•Beale number of 0.15•Operating speed of 1000 rpmResulting design targets:•200 Watt solar power collected•20 Watt mechanical output•10 Watt electrical outputResulting Values:•Mirror collection area of 1.658 ft3 •Displaced fluid volume of 6.39 in3

Will Tierney • Bryan Abbott • Phil Glasser • Mike Scionti

Dr. Chris HoopleDr. Sergey Lyshevski

USB output begins when motor reaches ~1570 RPM.Buck-boost can begin operating when generator voltage reaches 4.6V, and can operate in a boost mode down to 3.6V once powered on, and up to 18V (above the maximum voltage for this motor).

Generator Test Results

Custom electronics input and USB output shown above at full load of 1.915A (9.745W), 5.05Vavg, 0.45Vp-p ripple within USB specification. Successfully charged cell phones with power conditioning board shown right.