Power Gnome... never generate kilowatts of power alone.

Fri. May 04, 2007: Final

State University of NY

at Buffalo

EE: 494

Capstone Design

Spinelli, Yore

Mandate for design

UB Green under Walter Simpson are developing a solar powered exhibition trailer.

Specification: April 30th 2007Construction: Fall 2007

Photovoltaic power production to reach 2.8 kilowatts / hourConsumption will vary

But how do we keep track of it all…..?

…. The POWER GNOME!

A autonomous datacenter that monitors:

PV array voltage

the main power bus voltage

PV array current output

Charge controller output current

Main power bus output current

PV Trailer Power Layout

Characteristics

• Real-time oscillo-graph display

• Automatic time/date stamped logging– Open format/Excel

readable

• Practical Validation of PV power production

Education

• ‘How Efficient Am I?’ template– Visitor estimation of home power use and potential

savings• PV Sizer

– Allow visitor psudo-design of PV system• PSPICE

– Visitor demo of EE design software

Entertainment

Spool Multimedia playlist to PV trailer PA system

Queue conservation and environment action

videos

Able to display a 640x480 video and maintain normal

operations

State of Charge Monitor

• Sample half-rail voltage

– 60% depth of discharge, audible alarm

– 80% depth of discharge, cut off all power

• Obviously, also disables power to the Gnome, but reserve monitor continues to function

Final product has built in Hysteresis (relay pull-in vs. drop-out)

Power returns at 40% depth of discharge

Bringing the Gnome to Life

• PV environment dictates extreme low power• VIA C3 Eden embedded microprocessor @ 11 watts

– Carbon Neutral item @ Pentium III / Gen 1 P4 performance

• Complete item nominal @ 34 watts

Design Highlights

Current flow measurements @ the mV level

Utilize operational amplifiers to ramp into a 0 to 5 volt

working range .

Inverting Differential design implemented for PV

panel output current & charge controller output

current.

Design: Sensory Drivers

Design: State of Charge Monitor

Programming Highlights

MS-Dos Batch configuration of bootup, system

maintenance, etc.

Modified initialization files for ‘Tracer DAQ’.

Autolaunch with predefined trace configuration and

logging parameters.

How-To guide for ‘quick-n-easy’ startup.

Known Issues:

[1] - Tracer DAQ suffers buffer overflow

- Solutions:

a- MCC SDK

b- further analysis of initialization routine to rectify

issue.

** Gnome will be ready for practical use after this is

addressed.

Demonstration

Startup

Real-time display

Log system

How Efficient am I?

PV Sizer (region 695 = WNY)

State of Charge Monitor