ASTEP Life in the AtacamaCarnegie Mellon Limits of Life in the Atacama: Investigation of Life in the Atacama Desert of Chile Solar Panel Configuration Adam Slifko The Robotics Institute Carnegie Mellon University

ASTEP Life in the AtacamaCarnegie Mellon Solar Panel Configuration Options Fixed panel (no active sun tracking) Single tilt axis [sun tracking f(season)] Single tilt axis [sun tracking f(latitude)] Single tilt axis [sun tracking f(time)] Single azimuth axis [sun tracking f(heading)] Dual axis [sun tracking f(time, heading)]

ASTEP Life in the AtacamaCarnegie Mellon Which Configuration for Atacama Mission What are the technical impacts (complexity, mass, energy, reliability, navigation software, tip-over)? What are the economic costs (hardware, design, debug, test)? What are the schedule impacts? How much energy could we gain by tracking the sun? Is it worth it?

ASTEP Life in the AtacamaCarnegie Mellon National Solar Radiation Data Base (NSRDB) Provides radiation data for fixed and tracking collectors for 239 stations in the US and its territories Radiation data (7% measured, 93% modeled) Modeled from hourly values of direct beam and diffuse horizontal solar radiation from When analyzed can tell how much solar resource is available and how it varies year to year or month to month

ASTEP Life in the AtacamaCarnegie Mellon NSRDB – Data for Flat Plate Collectors Flat plate with fixed (N-S) tilt 0° (solar pond) Latitude –15° Latitude Latitude +15° 90° (vertical panel) Yearly solar radiation is maximized with a tilt angle equal to site’s latitude Winter radiation is maximized by +15° tilt Summer radiation is maximized –15° tilt

ASTEP Life in the AtacamaCarnegie Mellon NSRDB – Data for Flat Plate Collectors-2 One axis tracking - flat plate with fixed (N-S) tilt 0° (solar pond) Latitude –15° Latitude Latitude +15° Yearly and seasonal solar radiation is maximized by choosing the appropriate N-S tilt angle

ASTEP Life in the AtacamaCarnegie Mellon NSRDB – Data for Flat Plate Collectors-3 Two axis tracking - flat plate Represents the maximum solar radiation at a site available to a collector Tracks sun is azimuth and elevation to keep sun’s rays normal to the array’s surface

ASTEP Life in the AtacamaCarnegie Mellon NSRDB – Data Analysis Site Phoenix, Arizona Latitude: (N) Longitude: (W) Elevation: 339 m Pressure: 974 mbar Station Type: Primary As a primary site, Phoenix collects actual data Location where panels will be manufactured and tested Data taken from 10 of 30 years available

ASTEP Life in the AtacamaCarnegie Mellon Average Daily Solar Energy Table – 1 Year

ASTEP Life in the AtacamaCarnegie Mellon Average Daily Solar Energy Graph – 1 Year

ASTEP Life in the AtacamaCarnegie Mellon Comparing Positioning Methods – 1 Year

ASTEP Life in the AtacamaCarnegie Mellon Average Daily Solar Energy Table – December

ASTEP Life in the AtacamaCarnegie Mellon Average Daily Solar Energy Table - July

ASTEP Life in the AtacamaCarnegie Mellon Monthly % Solar Energy Gain – Table

ASTEP Life in the AtacamaCarnegie Mellon Monthly % Solar Energy Gain – Graph

ASTEP Life in the AtacamaCarnegie Mellon Summary of Yearly Tables and Graphs A single axis E-W sun tracking system produces 40% energy gains (over a solar pond) when considered for an entire year A single axis E-W sun tracking system with latitude adjustment produces 50% energy gains (over a solar pond) when considered for an entire year A dual axis positioning system produces 57% energy gains (over a solar pond) when considered for an entire year

ASTEP Life in the AtacamaCarnegie Mellon Summary of December Tables and Graphs A single axis E-W sun tracking system produces 47% energy gains (over a solar pond) when considered for December only A single axis E-W sun tracking system with latitude adjustment produces significant energy gains (over a solar pond) when considered for December only A dual axis positioning system produces 112% energy gains (over a solar pond) when considered for December only

ASTEP Life in the AtacamaCarnegie Mellon Summary of July Tables and Graphs A single axis E-W sun tracking system produces 32% energy gains (over a solar pond) when considered for July only A single axis E-W sun tracking system with latitude adjustment produces no energy gains (over a solar pond) when considered for July only A dual axis positioning system produces 34% energy gains (over a solar pond) when considered for July only

ASTEP Life in the AtacamaCarnegie Mellon About The Atacama Mission Equatorial mission is around 20°S latitude Mission time frame is March- May 03, 04, 05 Mission duration is seasonal (1-3 months) Spring mission in NH = fall mission in SH Assume fall in Atacama is like July in Phoenix

ASTEP Life in the AtacamaCarnegie Mellon Thoughts About Solar Panel Configurations Single tilt axis [sun tracking f(season)] – since missions only span 1-3 months, the sun’s angle in the sky will not change drastically and active tracking is not necessary Single tilt axis [sun tracking f(latitude)] – since mission range will not significantly change our latitude, active tracking is not necessary Single axis [sun tracking f(time)] – could provide 32% more power given mission latitude and duration. Same benefit can be achieved by adding 32% more solar cells at a lower overall cost

ASTEP Life in the AtacamaCarnegie Mellon Thoughts About Solar Panel Configurations-2 Single axis [sun tracking f(heading)] – high sun angle at mission latitude affords heading flexibility with small penalty in winter and no penalty in summer. Only necessary for missions outside tropic zone with low sun angles and where navigation flexibility is a must. Dual axis [sun tracking f(time, heading)] – provides only a 2% increase over the single axis system when sun is high in the sky. Only necessary for missions outside the tropic zone and when mission spans several seasons.

ASTEP Life in the AtacamaCarnegie Mellon Conclusion – Fixed Panel Configuration Fixed Panel (Horizontal Solar Pond) – most advantageous option given mission latitude and durations Increase panel area by 32% to achieve same benefits as an active positioner Other benefits are simplicity, low weight, low cost, high reliability, and low wind drag Less schedule risk to alter Hyperion vehicle for this panel configuration