Sustainable Energy Systems Engineering Peter Gevorkian Ch 1: Solar Power Technology Brevard Community College EST1830 Bruce Hesher

Solar Cells Solar cells are diodes also called PN junctions. They directly convert solar radiation into electricity with no moving parts, no water, no pollution, and no ! Solar cells are diodes also called PN junctions. They directly convert solar radiation into electricity with no moving parts, no water, no pollution, and no ! They do not work at night and their output decreases when cloudy. They do not store any energy. They do not work at night and their output decreases when cloudy. They do not store any energy. There are various ways to make them and a lot of research being done. There are various ways to make them and a lot of research being done. Intersil, Sematech, UCF

History of Photovoltaics The photovoltaic effect was first recognized in 1839 by French physicist A. E. Becquerel. In 1883 the first solar cell was built, by Charles Fritts, who coated the semiconductor selenium with an extremely thin layer of gold to form a PN junction, it was only 1% efficient. Albert Einstein explained the photoelectric effect in 1905 and received the Nobel prize in Physics in Russell Ohl patented the modern junction The photovoltaic effect was first recognized in 1839 by French physicist A. E. Becquerel. In 1883 the first solar cell was built, by Charles Fritts, who coated the semiconductor selenium with an extremely thin layer of gold to form a PN junction, it was only 1% efficient. Albert Einstein explained the photoelectric effect in 1905 and received the Nobel prize in Physics in Russell Ohl patented the modern junction semiconductor solar cell in 1946, Modern highly efficient solar cells were Modern highly efficient solar cells were first developed by Chapin, Fuller, and Pearson in 1954 using a diffused silicon PN junction.

Solar Cell Physics Carbon, silicon, and germanium are semiconductor elements. Carbon, silicon, and germanium are semiconductor elements. This means they have 4 valence electrons and form covalently bonded crystal masses. Silicon can easily be doped to make P and N type silicon. This means they have 4 valence electrons and form covalently bonded crystal masses. Silicon can easily be doped to make P and N type silicon.

P-N Junction Solar cells are P-N junctions, also known as diodes. Free electrons can only from the N-type to the P-type. A PN junction is a one way current valve similar to a check valve in a water pipe. Solar cells are P-N junctions, also known as diodes. Free electrons can only from the N-type to the P-type. A PN junction is a one way current valve similar to a check valve in a water pipe.

How a Solar Cell Works A solar cell converts light energy to electrical energy and is a current source. When a photon at a frequency with energy that equals to the bandgap of the impurity used to dope the silicon enters the PN junction, it frees both an electron and a hole. These opposite electric charges attract and want to get back together but the electron can’t go back through the PN junction. So, it goes the long way around through wiring attached to the cell (circuit) thereby doing useful work. A solar cell converts light energy to electrical energy and is a current source. When a photon at a frequency with energy that equals to the bandgap of the impurity used to dope the silicon enters the PN junction, it frees both an electron and a hole. These opposite electric charges attract and want to get back together but the electron can’t go back through the PN junction. So, it goes the long way around through wiring attached to the cell (circuit) thereby doing useful work.

How a Solar Cells Works The electrons flow through the circuit and the holes stay in the P-type material waiting for electrons. The electrons flow through the circuit and the holes stay in the P-type material waiting for electrons. The voltage only increases a little with increasing insolation while the current increases a lot! Predictable stable voltage is good; it allows us to match the voltage ranges of different pieces of equipment so we can connect them. The voltage only increases a little with increasing insolation while the current increases a lot! Predictable stable voltage is good; it allows us to match the voltage ranges of different pieces of equipment so we can connect them.

Types of Solar Cells Mono-crystalline silicon: The most efficient, and most expensive, solar cells are made of single crystal integrated circuit grade silicon wafers. Mono-crystalline silicon: The most efficient, and most expensive, solar cells are made of single crystal integrated circuit grade silicon wafers. Poly-crystalline silicon: Slightly less efficient and less expensive. Thin film: The least expensive and gaining ground in efficiency. Flexible and can be applied to curved and bending surfaces like backpacks or clothing.

Solar Cell Efficiencies

Solar Modules Cells are wired in series in modules and modules are connected in series in strings. Cells are wired in series in modules and modules are connected in series in strings.

Cells -> modules -> Strings - > Array Cells are connected in series to make modules; modules are connected in series to make stings. String are connected in parallel to make an array. Cells are connected in series to make modules; modules are connected in series to make stings. String are connected in parallel to make an array.

PV System Overview The array is connected to a PCU (Power Conditioning Unit) which is in turn connected to the buildings electrical distribution panel. The PCU performs many functions including: The array is connected to a PCU (Power Conditioning Unit) which is in turn connected to the buildings electrical distribution panel. The PCU performs many functions including: MPPT MPPT DC to AC inversion DC to AC inversion Charge control of batters (if present) Charge control of batters (if present)

US Insolation Map Central Florida gets about 5.2 Sun hours per day. Central Florida gets about 5.2 Sun hours per day. “Sun hours” is synonymous with KWH/m 2 /Day. “Sun hours” is synonymous with KWH/m 2 /Day. Germany is leading the world in deployed PV and they get the same insolation as Alaska! Germany is leading the world in deployed PV and they get the same insolation as Alaska!

Solar PV Applications Utility Scale Power plants: FPL’s Next Generation PV plant on KSC M.I. Utility Scale Power plants: FPL’s Next Generation PV plant on KSC M.I. Mobile: RV’s, Boats, Cars Mobile: RV’s, Boats, Cars Commercial: Electric car recharging stations (like Wal- Mart), road signs, school zones, etc. Commercial: Electric car recharging stations (like Wal- Mart), road signs, school zones, etc. Residential: Utility Interactive (“grid tied”) Residential: Utility Interactive (“grid tied”) Off-grid (stand-alone) Off-grid (stand-alone)

Further Study EETC2550 Photovoltaic Systems:  Technology  Design  Mechanical integration  Electrical integration  Permitting and Licensure  NABCEP certification