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Course Title
100 Home
101 Introduction
102 FAQ Page
103 Course Catalog
104 Green World
105 Demand & Supply
106 Conservation Careers
107 Solar Careers
108 Wind Turbine Careers
109 Entrepreneurs
110 Employee or Employer?
200 Demand Management
201 Summary
202 Residential Energy Profile
203 Ten Conservation Rules
204 HVAC System
205 Kitchen Appliances
206 Water Heater
207 Lighting
208 Laundry Appliances
209 Calculating Savings
300 Renewable Technology
301 Solar Energy
302 Solar Collectors
303 Solar Water Heating
304 Stirling Engines
305 Basic AC-DC Electronics
306 Silicon Solar Panels
307 Thin Film Solar Panels
308 Wind Turbines
309 Inverters
310 Grid Tied and Off Grid
311 Solar Site Survey
312 Solar Site Diagram
313 Sun Path Chart
314 Site Survey Worksheet
315 Wind Turbine Site Survey
316 Wind Turbine Worksheet
400 Solar Thermal Design
401 Solar Heat Overview
402 System Configuration
403 Site Survey
404 SRCC Compliance
405 System Specification
406 Bill of Materials
407 System Installation
408 Solar Heat Incentives
409 Document Package
410 Future Products
500 Solar PV Design
501 Solar PV Overview
502 System Configuration
503 Site Survey
504 Grid Tied & Off Grid
505 System Specification
506 Bill of Materials
507 System Installation
508 Solar PV Incentives
509 Document Package
510 Future Products
600 Wind Turbine Design
601 Wind Turbine Overview
602 System Configuration
603 Site Survey
604 Grid Tied and Off Grid
605 System Specification
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Green Collar Careers - Stirling Engines

The Stirling engine was invented and patented by a Scottish clergyman, Reverend Dr Robert Stirling in 1816.  In contrast to internal combustion engines, Stirling engines have the potential to use renewable heat sources more easily, to be quieter, and to be more reliable with lower maintenance.   Stirling engines can run directly on any available heat source, not just one produced by combustion, so they can run on heat from solar, geothermal, biological, nuclear sources or waste heat from industrial processes.   Since the invention of the Stirling, steam engines took dominance and later internal combustion engines due to the power to weight advantages.  Over the last decade Stirling engines have gained significant interest for solar power applications.

There are two principal types of Stirling Engine, kinematic and free-piston. All Stirling engines have two pistons (functionally speaking), one of which shuttles the working gas between the hot and cold zones and is known as a displacer, whilst the other is subject to the resulting pressure changes and does work to drive the engine. In the kinematic engine, these two pistons are physically connected by a crank mechanism, whereas in the free-piston engine, there is no physical linkage and the displacer oscillates resonantly.

On a perfect New Mexico winter day with the sky almost 10 percent brighter than usual Sandia National Laboratories and Stirling Energy Systems (SES) set a new solar-to-grid system conversion efficiency record by achieving a 31.25 percent net efficiency rate.  Compare that to the 12% efficiency of a Solar PV system.

Solar powered Stirling engines have recently been developed to operate in space based on free-piston designs.

Cogeneration
As a mechanical system the Stirling engine also can directly power other mechanical devices such as refrigeration pumps which is spawning a new technology known as cogeneration.  Commercially available cogeneration systems were first available in New Zealand and they are beginning to be distributed in Europe.  Although the technology is relatively new the total economics of the systems are impressive.  Turnkey cogeneration systems that are capable of generating and storing 50 kWh per day (1500kWh/month) are running about $30,000.

 

Solar PV vrs Concentrated Stirling Cogeneration
Feature Stirling Cogeneration Solar PV
30 Sunny Day Output 1500 kWh 1500 kWh
50% Cloud/Obscured Output 50% 20%
Watts/Square Foot Output 18 12
Includes HVAC Heat Pump Yes No
Includes Solar Water Heater Yes No
24 Hours Energy Storage Yes No
Installed Cost $20,000 $20,000
Life Expectancy 15 years 25 years

Although these systems aren't yet available in the United States there are at least three major US HVAC manufacturers that have development programs with plans for product release by 2012.