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

Sustainable Energy Systems Sustainable Energy Systems EngineeringEngineering

Peter GevorkianPeter Gevorkian

Ch 1: Solar Power TechnologyCh 1: Solar Power Technology

Brevard Community CollegeBrevard Community College

EST1830EST1830

Bruce HesherBruce Hesher

Solar CellsSolar Cells Solar cells are diodes also called PN junctions. They Solar cells are diodes also called PN junctions. They directly convert solar radiation into electricity with no directly convert solar radiation into electricity with no moving parts, no water, no pollution, and no ! moving parts, no water, no pollution, and no !

They do not work at night and their output They do not work at night and their output decreases when cloudy. They do not store any decreases when cloudy. They do not store any energy.energy. There are various There are various ways to make them ways to make them and a lot of and a lot of research being research being done.done.

Intersil, Sematech, UCF

History of PhotovoltaicsHistory of Photovoltaics

The photovoltaic effect was first recognized in The photovoltaic effect was first recognized in 18391839 by French physicist by French physicist A. E. BecquerelA. E. Becquerel. In . In 18831883 the first solar cell was built, by the first solar cell was built, by Charles FrittsCharles Fritts, who , who coated the semiconductor selenium with an coated the semiconductor selenium with an extremely thin layer of gold to form a PN junction, it extremely thin layer of gold to form a PN junction, it was only 1% efficient. was only 1% efficient. Albert EinsteinAlbert Einstein explained the explained the photoelectric effect in photoelectric effect in 19051905 and received the Nobel and received the Nobel prize in Physics in prize in Physics in 19211921. . Russell OhlRussell Ohl patented the patented the modern junction modern junction

semiconductor solar cell in semiconductor solar cell in 19461946, ,

Modern highly efficient solar cells were Modern highly efficient solar cells were

first developed by first developed by ChapinChapin, , FullerFuller, and , and

PearsonPearson in in 19541954 using a diffused silicon using a diffused silicon

PN junction. PN junction.

Solar Cell PhysicsSolar Cell Physics

Carbon, silicon, and germanium are Carbon, silicon, and germanium are semiconductor elements. semiconductor elements.

This means they have This means they have 4 valence electrons and 4 valence electrons and form covalently bonded form covalently bonded crystal masses. Silicon crystal masses. Silicon can easily be doped to can easily be doped to make P and N type make P and N type silicon.silicon.

P-N JunctionP-N Junction

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

How a Solar Cell How a Solar Cell WorksWorks

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

How a Solar Cells How a Solar Cells WorksWorks

The electrons flow through the The electrons flow through the circuit and the holes stay in the P-circuit and the holes stay in the P-type material waiting for electrons.type material waiting for electrons.

The voltage only increases a The voltage only increases a little with increasing insolation little with increasing insolation while the current increases a lot! while the current increases a lot! Predictable stable voltage is Predictable stable voltage is good; it allows us to match the good; it allows us to match the voltage ranges of different pieces voltage ranges of different pieces of equipment so we can connect of equipment so we can connect them.them.

Types of Solar Types of Solar CellsCells

Mono-crystalline siliconMono-crystalline silicon: The most efficient, and : The most efficient, and most expensive, solar cells are made of single most expensive, solar cells are made of single crystal integrated circuit grade silicon wafers.crystal integrated circuit grade silicon wafers.

Poly-crystalline siliconPoly-crystalline silicon: Slightly less : Slightly less efficient and less expensive. efficient and less expensive.

Thin filmThin film: The least expensive and : The least expensive and gaining ground in efficiency. Flexible gaining ground in efficiency. Flexible and can be applied to curved and and can be applied to curved and bending surfaces like backpacks or bending surfaces like backpacks or clothing.clothing.

Solar Cell Solar Cell EfficienciesEfficiencies

Solar ModulesSolar Modules

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

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

PV System PV System OverviewOverview

The array is connected to a The array is connected to a PCUPCU (Power Conditioning Unit) which is in turn connected to the (Power Conditioning Unit) which is in turn connected to the buildings electrical distribution panel. The PCU performs many functions including:buildings electrical distribution panel. The PCU performs many functions including:

MPPTMPPT

DC to AC inversionDC to AC inversion

Charge control of batters (if present)Charge control of batters (if present)

US Insolation MapUS Insolation Map

Central Florida Central Florida gets about 5.2 Sun gets about 5.2 Sun hours per day. hours per day.

“ “Sun hours” is Sun hours” is synonymous with synonymous with KWHKWH//mm22//Day.Day.

GermanyGermany is is leading the world in leading the world in deployed PV and deployed PV and they get the same they get the same insolation as insolation as Alaska!Alaska!

http://www.nrel.gov/gis/solar.html

Solar PV Solar PV ApplicationsApplications

• Utility Scale Power plantsUtility Scale Power plants: FPL’s Next Generation : FPL’s Next Generation PV plant on KSC M.I.PV plant on KSC M.I.

• MobileMobile: RV’s, Boats, Cars: RV’s, Boats, Cars

• CommercialCommercial: Electric car recharging stations (like : Electric car recharging stations (like Wal-Mart), road signs, school zones, etc.Wal-Mart), road signs, school zones, etc.

• ResidentialResidential: Utility Interactive (“grid tied”): Utility Interactive (“grid tied”)

Off-grid (stand-alone)Off-grid (stand-alone)

Further StudyFurther Study

EETC2550 Photovoltaic SystemsEETC2550 Photovoltaic Systems:: TechnologyTechnology DesignDesign Mechanical integrationMechanical integration Electrical integrationElectrical integration Permitting and LicensurePermitting and Licensure NABCEP certificationNABCEP certification