Indoor Radiant (Light) Energy Measurements

Contributors: Michael Zapas, Maria Gorlatova, Enlin Xu, Matthias Bahlke.

05/14/2011 The measurements have been added to the CRAWDAD wireless data repository. [ CRAWDAD dataset link ] [ bib item ]

To characterize indoor energy availability, since 2009 we have been conducting a light energy measurement study in office buildings in New York City. In this study we take long term measurements of irradiance (in units W/cm^2) in several indoor locations, and also study a set of shorter-term indoor/outdoor mobile device measurements.

The description of the irradiance measurements and some analysis appear in:

• M. Gorlatova, A. Wallwater, and G. Zussman, Networking Ultra Low Power Energy Harvesting Devices: Measurements and Algorithms, in Proc. IEEE Computer Communications Conference (IEEE INFOCOM'11), Apr. 2011 [ bib item ].

We would appreciate it if you cite this paper when publishing results that use the provided measurements.

Some additional analysis of the measurements is also provided in the technical report Networking Low-Power Energy Harvesting Devices: Measurements and Algorithms.

Setup Description and Data Format

For the measurements we use TAOS TSL230rd photometric sensors installed on LabJack U3 DAQ devices. These photometric sensors have a high dynamic range, allowing capturing of widely varying irradiance conditions. We verified the accuracy of the sensors with a NIST-traceable Newport 818-UV photodetector.

The format for the trace files is as follows:

• The first column is the number of seconds since the beginning of the experiment.

• The second column is the measured irradiance. The measurements are in units of microwatts per cm^2 (µW/cm^2).

• The subsequent columns are the timestampof the measurement, separated into: year, month, day, hour, minute, second.

  Mobile Measurements

• Experiments done by Michael Zapas and Enlin Xu.

• Indoor + Outdoor Mobile Measurements: pedestrian walking around university campus (indoor and outdoor environments) carrying a sensor. Measurements date: April 05, 2010. Trace: .mat / .txt. Plotted irradiance.

• New York City Nighttime Measurements: pedestrian walking in New York City (Theater District and Times Square) at nighttime, with a sensor attached to a backpack. Measurements date: July 22, 2010. Trace: .mat / .txt . Plotted irradiance.

• Car-based roadtrip (sensor attached to the dashboard). Trace: .mat / .txt .

• Commuting on public transit, sensor attached to a backpack, measurements outdoors, indoors (office, subway, train). Trace: .mat / .txt .

Stationary Measurements

Stationary measurements are collected by installing a device in a particular indoor location and having it in one location measuring the light conditions for a long time. The measurement setups description is provided in Table II of the technical report. The schematic diagram of the measurements' locations is shown schematically in the diagram below (click to enlarge). The interruptions in the data are due to technical issues (power interruptions, device malfunctions). In the combined .mat files, the missing days are represented by NaNs. Individual (not combined) data sets are also provided. For an easy data `feel', we provide simple graphs of irradiance (as recorded by the devices), and of daily irradiation H, which is calculated by adding up the irradiance measurements corresponding to each particular day.

• Setup A (student office): ongoing, started August 14, 2009. Traces (here) provided up to September 13, 2010. 
  
  • Combined file: .txt file (zipped) / .mat file
  • Graphical depictions of the combined trace: Irradiance plot +  plot of daily irradiation (J/cm^2/day).
• Setup B(bookshelf in an office, getting little sunshine): ongoing, started November 13, 2009. Traces (here) provided up to November 23, 2010.
  • Combined file: .txt file (zipped) / .mat file.
  • Graphical depictions of the combined trace: Irradiance plot, full and partial, +  plot of daily irradiation (J/cm^2/day).
• Setup C (Departmental conference room): ongoing, started November 6, 2009 . Traces (here) provided up to September 13, 2010.
  • Combined file: .txt file (zipped) / .mat file.
• Setup D (student office): ongoing, started November 05, 2009. Traces provided up to September 29, 2010.
  
  • Combined .txt file (zipped) / .mat file
• Setup E (student office): Pilot measurement set, completed in 2009. Date range: June 25, 2009 - October 11, 2009. 
  • .txt file (zipped)/ .mat file
• Setup F: (student office): ongoing, started February 16, 2010. Traces provided up to April 15, 2010. 
  • .txt file (zipped)/ .mat file

Individual (not combined) tracefiles for the setups are provided here.

The measurements also appear in the CRAWDAD wireless data repository. [ bib item ]

Related Work

To the best of our knowledge the above-provided traces are the first traces of indoor irradiance measurements. Related datasets are the measurements of outdoor irradiance and the measurements of of indoor illuminance measurements.

• National Renewable Energy Laboratory (NREL) of the US Department of Energy provides extensive outdoor irradiance measurements.

• Indoor illuminance measurement traces (in Lux) have been obtained in the Intel Berkeley Research Lab experiments -- link.

• Illuminance traces have been collected in the UMass CRFID project, and are available here.

Questions? Please contact Maria Gorlatova, maria.gorlatova at caa dot columbia dot edu.