How Green is Visible Light Communications?

To address VLC’s green credentials I first consider what makes it green.  Here are my top 3 reasons:

  1. VLC helps stimulate the demand for LED lighting and LED bulbs and fixtures are now highly efficient.  If we were all to switch over to LED illumination the energy savings would be colossal.
  2. The power consumed by VLC in transmitting data is small compared to RF communications equipment.
  3. VLC eliminates the need for some items of communications equipment, this too reduces the energy required to produce the communications equipment.

So having considered why VLC is green from a qualitative point we are left with the trickier task of determining how green it could be based on a quantitative analysis.  To do this we must make a few assumptions and then calculate the savings in green house gasses (based on CO2 emissions) resulting from a switch to VLC solutions.

We will make the assumption that LED VLC technology will be used in place of incandescent lamps and Wi-Fi, we will also assume that the savings in energy will savings will be obtained generating less electricity from fossil fuels.  From the qualitative analysis we can identify three areas where energy can be saved.

  1. Operational energy savings by using LED compared with incandescent.
  2. Operational energy savings by using VLC instead of Wi-Fi
  3. Embodied energy savings by manufacturing LED VLC lamps instead of incandescent light bulbs and Wi-Fi access points.

I have calculated the operational energy of a typical LED lamp as 18kWhr  per year based on a duty cycle of 4 hours per day.  The energy used in a Wi-Fi per year is 53kWhr as compared to 3kWhr of additional energy required for VLC over and above the energy required for illumination.

The embodied energy per year in a Wi-Fi (based on an average lifetime of 3 years) is 16kWhr.  While the embodied energy in a VLC light bulb and transceiver circuit has been estimated at 1.0kWhr (based on a lifetime of 10 years).  The embodied energy in an incandescent bulb is 0.4kWhr based on 0.8 year lifetime.

Given that there are 14 billion incandescent light bulbs and 300 million Wi-Fis, replacing all of these by VLC lamps would save about 897 billion kWhr of energy.  This is laid out in the table below:

Annual Energy Embodied Energy Volume Total Energy
Incandescent bulb 89.3 kWhr 0.4 kWhr 14 billion 1226 b kWhr
Wi-Fi 53 kWhr 16 kWhr 300 million 21 b kWhr
VLC 21 kWhr 1.0 kWhr 14 billion 308 b kWhr

Total Savings

897 b kWhr

Could we eliminate the need for 100 nuclear power plants?

This is equivalent to a reduction of 870 million tonnes of CO2 per year if less fossil fuel is used to generate the electricity.  Alternatively we can consider the savings in terms of nuclear power stations.  A modern nuclear power plant generates about 8-10 TWhr  of electricity per year.  So the saving is equivalent to eliminating the need for 100 nuclear power stations!

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