Done By: Stanley Yuan Dae Koon Lim Joel Koh James Wong

AgendaHow Photo-voltaic (PV) cells workHow Solar PV cells are madeSolar PV

ApplicationsEfficienciesEconomicsFacts & TrendsAdvantages vs. Disadvantages

What are Solar CellsThin wafers of silicon

Similar to computer chipsMuch biggerMuch cheaper

Silicon is in abundanceMade from sandNon-toxic, safe

Light carries energy into cellCells convert sunlight energy into electric

current, however they do not store energySunlight is its source of “fuel”

DefinitionsCells- basic photovoltaic device that is the

building block for PV modulesModule- a group of PV cells connected in

series and encapsulated in an environmentally protective laminate

Panel- a group of modules that is the basic building block of a PV array

Array- a group of panels that comprises the complete PV generating unit

Some interesting facts on SolarThe sunlight that reaches the earth is about 200,000

times the total electrical energy generated by humans everyday

The first working solar cell was invented by Charles Fritts in 1883 and operated at 1% efficiency

The word photovoltaic, the term for a solar cell, comes from the Greek word for light, which is combined with the name Volta, the last name of the scientist after whom the measurement unit volt is named after. All together the word photovoltaic means electricity from light

Every minute, enough solar energy reaches the Earth to meet global energy demands for a year!

How it worksSolar energy is harnessed and used through a

process using photovoltaic cells. These cells or panels are usually made up of two types of silicon

Sunlight is made up of negative and positive layers, which creates an electrical field

When the protons hit the surface of the solar cell, the electrons from the light rays are freed, pass to the bottom of the cell and flows through to power appliances

The flow of electrons is also known as electricity

How it works• To complete the PV

module, several layers are added.

A - Cover GlassB - Antireflective

CoatingC - Contact GridD - N-type SiliconE - P-type SiliconF - Back Contact• Here is an example of

how a home can be wired to run on Solar PV power

Cross section of a PV cell

How Solar Cells are madeMaterials

Crystalline SiliconGallium Arsenide (which are more expensive)

StepsGrown into large single-crystal ingotsSawed into thin wafers2 wafers are bonded together (p-n junction)Wafers grouped into panels or arrays

Creating Silicon wafers

Creating a PV Cell

Solar PV systemCells

Building block of PV systemTypically generates 1.5-3 watts of power

Modules36 cells connected together have enough voltage to

charge 12 volt batteries and run pumps and motorsAka PanelsMade up of multiple cells

ArraysMade up of multiple modulesCosts about $5-$6/watt

However, a typical system costs about $8/watt

Types of mounted arraysStandoff-Mounted ArraysRack-and Pole-Mounted ArraysCalifornia Patio Cover

Solar PV ApplicationsSpacecraft

Solar PV ApplicationsResidential

Solar PV ApplicationsCommercial

Large Scale Solar Power • PV-generated electricity still costs more than electricity generated by conventional plants in most places, and regulatory agencies require most utilities to supply the lowest-cost electricity.

•Output dependent on weather

•Mostly used in Southwest

Solar furnace project in California

Dish collector focuses heat to drive generator

150 MW solar power facility in California – the world’s largest

Solar Cell EfficienciesTypical module efficiencies ~12%

Screen printed multi-crystalline solar cellsEfficiency range ~6-30%

6% for amorphous silicon-based PV cells20% for best commercial cells30% for multi junction research cells

Typical power of 120W/m2

Solar Panel Efficiency~1 kW/m2 (sunny day)~20% efficiency – 200W/m2 electricityDaylight and weather in northern latitudes

100 W/m2 in winter; 250 W/m2 in summerOr 20 to 50 W/m2 from solar cells

Value of electricity generated at $0.08/hWh$0.10/m2/day or $83,000 km2/day

World’s Largest PV Solar Plants

World Solar Power Production

Current energy demand in the world

Around 0.1% of primary energy demand Solar electric installations totalled 200MW in

1999, 280MW in 2000 and 340MW by 2001 and 427MW in 2002. 

The growth rate is among the fastest in energy sources. Most of the growth is driven by the growth in Germany, Japan, and USA.

From IEA

AdvantagesNon polluting: no noise, harmful or unpleasant

emmisions or smellsReliable: most solar panels have a 25 year

warranty and even longer life expectancySolar modules over their lifetime produce more

power per gram of material than nuclear power but without the problem of large volumes of environmentally hazardous material

Solar panels produce more power within 5 years than the power consumed in their production

Solar power is a renewable energy source. It cannot be used up thus is effective in reducing the usage of fossil fuels

Save more money in the long run

DisadvantagesWe are unable to utilize the power of the sun

at night or cloudy daysSolar panels are expensive to buy and hard to

set up

Production and Disposal ConcernsProduction - Worker Health and Safety･ Amorphous silicon -Silane, an explosive gas, is used in making amorphous silicon. Toxic gases such as phosphine and diborane are used to electronically "dope" the material. ･ Copper indium diselenide -Toxic hydrogen selenide is sometimes used to make copper indium diselenide, a thin-film PV material. ･ Cadmium telluride -Cadmium and its compounds, which are used in making cadmium telluride PV cells, can be toxic at high levels of lung exposure.

Disposal･Module lifespan typically around 30 years

･ Some material classified as hazardous waste･ Recycling process not yet perfected

Why not? Expensive for Consumers and Producers Two years output needed to just equal the

amount of energy used in production Large land areas needed to produce energy on

a power plant scale Limited by intermittence. Stable grids require

traditional generating facilities or costly backup to ensure uninterrupted supply.

Due to PV efficiency and low market demand, technological progression is slow.

Environmental concerns in production and disposal

Lack of subsidies and tax credits (In the U.S.)

Cost AnalysisUS retail module price = ~$5/W (2005)Installation cost = ~$3.50/W (2005)Cost for a 4 kW system= ~$17,000 (2006)

Without subsidiesTypical payback period is ~24 years (warranty)

CostPrecise calculation of solar electricity

costs depend on the location and the cost of finance available to the owner of the solar installation

With the best PV electricity prices (in the sunniest locations) approaching 30 cents/kWh and the highest tariffs now exceeding 20 cents/kWh

Funding programs that bridge this gap are causing rapid growth in sales of solar PV, especially in Japan and Germany. 

House of the Future?This zero-energyhouse in theNetherlands has30m2 of PV panelsfor powergeneration and12m2 of solarcollectors for waterand space heating

Solar PV DependenciesLocation, Location, Location!Latitude

Lower latitudes are better than higher latitudesWeather

Clear sunny skies are better than cloudy skiesHowever the temperature is not important

Direction solar arrays faceSouth is preferred, east and west are acceptableHowever, solar panels are more effective if they are

arranged like treesAbsence of shade

Trees, flatirons, etc

Emerging PV TechnologiesCells made from gallium arsenide

Molecular beam epitaxy35% more efficiency has been observed

Non-silicon panels using carbon nanotubesQuantum dots embedded in special plasticsMay achieve 30% efficiencies in time

Polymer (organic plastics) solar cellsSuffer rapid degration to date

Thin film Solar CellsUse less than 1% of silicon required to make

wafersSilicon vapour deposited on a glass substrateAmorphous crystalline structure

Many small crystals vs. one large crystal

New roof integrated PV productsFlexible PV Cells

Thank YOU!!