Product versus prototype development:

One challenge of the project is to effectively meet the four desired outcomes outlined by management.  In dealing with the unique nature of a solar design utilizing Stirling engine technology, an equally unique approach to the problem was developed and maintained.  The following attempts to clarify the group rationale for decisions made concerning what to model and how to model it for both the design and the prototype.

The first objective is to “develop a concept for a product that has demonstrated market/societal value.”  Taken straight-forwardly, the group conceived a small-scale solar harnessing reflector and heat engine (Stirling) with electrical generation, management and storage.

The second objective states “develop a virtual model and prototype to effectively demonstrate key technical features” of the concept.  The interpretation and implementation by the group contained two components.  The first component required the development of a design via engineering calculations and decision making which would be effectively presented using CAD modeling.  The second phase would then be development of a prototype to demonstrate features deemed critical to proving feasibility.  Prior to the break at week eight (4 March), it was determined that construction of a Stirling engine would be impractical given the time constraints on the project.  To prove the feasibility of the Stirling cycle, a qualitative measure of the performance would be provided by a model engine. 

The third and final objective dealing with development requires “[developing] a product that contains some form of embedded intelligence”.  While considering the appropriate use of embedded intelligence, the group tried to reduce the number of electrical components such that the majority of electricity generated would be used to power the device and charge the battery.  The group also chose not to model some electrical components since the Stirling engine would not be driving a generator.  With the preceding comments in mind, the following possibilities were considered and either eliminated or not modeled.  The justification for each component is included as well.

• Circuit to track the sun – This device would have included sensors to monitor the collector’s position relative to the sun and then adjusted the collector with an actuator accordingly.  It was deemed unnecessary, and therefore parasitic, with the use of a parabola trough which could be set once a day to passive track the sun.
• Circuit to condition electrical output – This circuit would include the necessary components to direct the necessary power to the device to be powered and all extraneous power to the battery to charge it.  With the decision to not construct our own Stirling engine, a generator would then not be used in the prototype and therefore the circuit was not constructed.
• Circuit to monitor the Stirling engine – This device would monitor the temperatures of the hot and cold couples of the Stirling engine.  Once the desired temperature difference is reached, the circuit checks for operation of the Stirling engine.  If the engine is not running, the circuit engages a starter which propels the Stirling engine into operation.  This device is currently in the development stages.