P12472 Solar Stirling Engine Generator: Final Presentation

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

Presentation Outline

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

Suggestions Objective Project Evaluation

Project Description

We wish to demonstrate a small portable Stirling cycle electrical generator system that can be used to power small portable USB electronics.

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 Needs

* Design meets custom all needs

Customer Requirement Comment

Met?

USB Charger Output power through a USB port. Yes

Stirling EngineGenerator component must be powered by a heat engine utilizing the stirling cycle. Yes

Solar Powered Obtain heat energy from the sun. YesAutonomous Operation Stirling engine must self start. YesLow Maintenance Operate for one year, maintenance free. Yes

Cheap Project design must be inexpensive. YesLightweight Stirling generator must be relatively portable Yes

SafeStirling generator must not cause any damage to people or surroundings when operated Yes

Engineering Specifications

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

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

System Architecture

Aluminum Solar Collector

Chamber & Heat

Sink

Power & Displacer Piston

Crankshaft

Flywheel

Power Conditioni

ng

Belt and pulleys

PMDC Generat

or

Battery

Thermocouples

& MAX6675

ArduinoUSB

Output

PMOS FET

Project Status

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

Project Schedule

Project Schedule

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

Budget

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

Over-budget due to under-estimated shipping costs

Estimated ActualMechanical $308.20 $321.51Electrical $208.89 $216.01Total $517.09 $537.52

Electrical Testing Results 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), 5.05Vavg, 0.45Vp-p ripple within USB specification.

Successfully charged cell phones with power conditioning board

Mechanical Testing Results 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

0 10 20 30 40 50 600

200

400

600

Time vs Differential Temperature

Time (Minutes)Diff

ere

nti

al Tem

per-

atu

re (

F)

Major Issues, Future Work, and Suggestions

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.

Objective Project Evaluation

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.

Questions?