Team P12472 Phil Glasser – Lead Engineer, Electrical Engineer William Tierney – Mechanical Engineer Bryan Abbott – Mechanical Engineer Mike Scionti– Mechanical Engineer Dr. Alan Raisanen – Faculty Guide, Customer

         Concept Summary Customer Needs and Specs System Architecture Project Status Schedule Budget System Testing Results Major Issues, Future Work, and Suggestions Objective Project Evaluation

    We wish to demonstrate a small portable Stirling cycle electrical generator system USB electronics .

that can be used to power small portable Stirling generators can use any heat source to produce power including geothermal, waste heat and in our case solar energy .

Although mechanically more complex than photovoltaic systems, Stirling generator system efficiency can out perform photovoltaic system efficiency.

Our system will require the design of a solar collector component, a Stirling engine component, and an electrical generator , power conditioner and power storage component.

Customer Requirement

USB Charger

Comment

Output power through a USB port.

Stirling Engine Generator component must be powered by a heat engine utilizing the stirling cycle.

Solar Powered Autonomous Obtain heat energy from the sun.

Operation Stirling engine must self start.

Low Maintenance Operate for one year, maintenance free.

Cheap Lightweight Safe Project design must be inexpensive.

Stirling generator must be relatively portable Stirling generator must not cause any damage to people or surroundings when operated

Met ?

Yes Yes Yes Yes Yes Yes Yes Yes * Design meets custom all needs

      Power: Stirling generator must output at least 10 Watts of power when operating.

Voltage: Generator component must provide a nominal voltage of 5 Volts when operating.

Budget: Stirling generator assembly must be within the budget of $500. Approved for $517.

Weight: Stirling generator assembly must be within the weight requirement of 20 pounds.

Mean Time Between Failures: Stirling generator system must operate for one year before requiring maintenance.

Weatherproof: Stirling generator must be able to withstand all weather conditions.

   Selected concept was a single cylinder beta type Stirling engine with a 90 degree offset crankshaft to convert linear to rotational motion This couples through pulleys and a timing belt to a PMDC motor which we used to both soft start the engine, and generate power through two buck-boost converters Buck-boost circuits power USB devices, charge lead acid battery to power Arduino and soft start

Aluminum Solar Collector Chamber & Heat Sink Thermocouples & MAX6675 Power & Displacer Piston Crankshaft PMOS FET Arduino Flywheel Belt and pulleys PMDC Generator Power Conditioning USB Output Battery

   Electrical power generation, soft start, and battery charger all working and tested Seals, Heat sink, solar collector, and separated piston and crankshaft/flywheel subassemblies Possible Mechanical issues preventing engine from running  Crankshaft Misalignment  Friction in connecting rod bearings  Under-designed mounting brackets

  Machining took much longer than initially calculated  Rework on the crankshaft due to issues with construction  Redesign of mounting brackets  Base-plate redesign  Redesign of connecting rod – power piston, displacer piston connections  Fine-tuning of piston seals Time was managed, engine was still built by week 8 but is currently not working due to mechanical issues

 The project came in $20.43 over the approved budget of $517.09

 Over-budget due to under-estimated shipping costs

Mechanical Electrical

Total Estimated Actual

$308.20 $321.51

$208.89 $216.01

$517.09 $537.52

  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)  Custom electronics input and USB output shown at full load of 1.915A (9.745W), 5.05V

avg , 0.45V

p-p ripple within USB specification.  Successfully charged cell phones with power conditioning board

    Max differential 597 ºF at 1 hour, 450 ºF at 12 Minutes Logarithmic heating curve, as expected Temp Hot ~6X > Temp Cold Heating tape used 600 400 200 0 0 10

Time vs Differential Temperature

20 30

Time (Minutes)

40 50 60

  Issue - Stirling engine does not run, possibly due to:  Crankshaft Misalignment  Friction in connecting rod bearings  Under-designed mounting brackets Recommended Future Improvements:  Higher machining precision and sturdier design in mounting structure and crankshaft.

 Higher precision in crankshaft - connecting rod – piston assembly.

    Overall, the electric portion of the project met all of the specs and customer needs.

The mechanical section ran into a couple snags with respect to friction and mechanical binding. Built to our design, but unable to run. For future iterations, we recommend a sturdier mounting structure and crankshaft and an overall stringent precision with respect to the crankshaft assembly.