Photovoltaics for Powering Rural Telecom Installations

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Photovoltaics for Powering Rural Telecom
Installations

• John Anasis
• ECE 510, Wireless Communications
• Winter Term, 2008

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Background

• Rural areas in developing countries typically
  lack both telecom and power infrastructure.
• Power is required before telecom can be viable.
• Power costs must be affordable.

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Role of Photovoltaics

• Photovoltaics require little maintenance.
• No need for highly skilled operators to keep the
  systems running.
• No fuel cost or emissions.
• Can be installed on a stand alone basis.

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Basic Theory of a Solar Cell

• Photons from sunlight knock electrons out of
  valence band and into conduction band.
• Result is an electric current.
• The device is basically a p-n junction diode.

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Solar Cell Equivalent Electrical Circuit Model
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Solar Cell Efficiency

• Efficiency of solar cells is given by
• ? ____Pm_____, where
• E x Ac
• Pm solar cell power
• E solar irradiance (W/m2)
• Ac area of solar cell (m2)

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Solar Cell Efficiency (Cont.)

• Efficiencies are determined under standard test
  conditions (25o C, E 1000 W/m2, and an air mass
  1.5 spectrum).
• Efficiencies are now up to 20-25.
• Use of concentrators pushing efficiencies up
  towards 30.

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Photovoltaic Costs

• Life cycle costs of a PV installation very
  dependent on the solar insolation at the site.
• PV systems cost 8000-12,000 per kWp installed.

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Photovoltaic System Components

• Batteries needed to store energy when sun is not
  shining.
• Charge controller allows batteries to be safely
  charged from the PV array.
• Inverter converts the DC current from the PV
  array and batteries to AC current.

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Backups to the PV Array

• Batteries are primary backup to the PV array.
  Standard lead-acid batteries are typically
  employed.
• Small hydro and small wind installations can also
  augment the energy supplied by the PV array.
• Small wind capacities range from 900W to 10kW
  with cost 12,000-55,000.

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Figure from http//www.green-trust.org/hydro.htm
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From http//en.wikipedia.org.wiki/wind_turbine