eeng622 - chapter 1a.pdf

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Dr. Ali Assi EENG 622 Photovoltaic Energy Systems

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Page 1: EENG622 - CHAPTER 1a.pdf

Dr. Ali Assi

EENG 622 Photovoltaic Energy Systems

Page 2: EENG622 - CHAPTER 1a.pdf

CHAPTER 1

INTRODUCTION

Page 3: EENG622 - CHAPTER 1a.pdf

Photovoltaics – What is it all about?

Photovoltaics is a technology involving the direct conversion of solar radiation (also called insolation) into electricity using solar cells.

2/20/2014 3 Photovoltaic Energy Systems – Introduction

http://www.youtube.com/watch?v=x2zjdtxrisc

http://www.youtube.com/watch?v=4lIfPRjjbug

Page 4: EENG622 - CHAPTER 1a.pdf

Photovoltaics Solar Module

As individual solar cells generate very low voltage, a number of such cells are connected in series and combined into a so-called solar module.

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Photovoltaics Solar Generator

Higher output can be obtained by wiring a number of modules together to create solar generators, which can be of any size.

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Page 6: EENG622 - CHAPTER 1a.pdf

Photovoltaics – Spaceship

The first usable solar cell was developed in 1954, and solar cells were used for technical purposes in connection with space flight – Solar batteries.

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Photovoltaics – Why?

Following the 1973 oil crisis, interest in renewable energy, particularly in terms of solar power.

Interest in Photovoltaics has grown even further since the Chernobyl accident in 1986, which spurred the development of simpler and cheaper solar cells for terrestrial applications

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Photovoltaics and Today’s Energy

The insolation used by solar cells constitute an inexhaustible energy resource, unlike oil, uranium, and coal, which are the most widely used energy resources today.

Oil, uranium, and coal are finite resources

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Today’s Energy

The Future

Page 9: EENG622 - CHAPTER 1a.pdf

Photovoltaics and Batteries

A basic problem with terrestrial PVs is the fluctuations of insolation by virtue of the sunrise and sunset cycle, cloudy and rainy weather and seasonal changes in insolation.

PVs must use batteries to store energy (Stand-alone PV systems) or must be connected to an existing power grid (Grid-connected PV systems).

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Raw Materials of Photovoltaics

PV energy is extremely clean and environmentally friendly, and engenders no noise pollution, waste-gas emissions or toxic waste.

Silicon, the main raw material used for solar cells, is one of the most abundant substances on earth (Sand)

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Manufacturing

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Raw Materials of Photovoltaics (Cont.)

Thus electricity from solar cells can in a sense be thought of as “power from sand and Sun”

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Photovoltaics – Maintenance

Solar cells are maintenance free and extremely reliable.

If they are protected from environmental influences by fault-free packing, mono and ploy crystalline solar cells have a life expectancy of 25 to 30 years.

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Page 13: EENG622 - CHAPTER 1a.pdf

Photovoltaics vs. Thermal Solar Energy

In contrast to thermal solar systems which can only use direct beam radiation, PVs can also convert into electricity the diffuse portion of insolation; Diffuse radiation accounts for more than 50% of the total insolation in some regions.

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Photovoltaics – Restrictions and Drawbacks

Another important difference between thermal solar systems and PV systems is that the latter are not subject to minimum size restrictions; PVs are not subject to an upper size limit either – modularity of PVs

Cost is the major drawback of PVs

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Photovoltaics – Largest Plants

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http://www.pvresources.com/pvpowerplants/top50.aspx

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Photovoltaics – Installations

PV Solar Installations By Country (GW)

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Country 2010 2011 2012

Germany 7.5 7.5 5.5

Italy 4.3 6.3 4.5

United States 0.9 1.9 3.8

Japan 0.9 1.3 2.5

France 0.6 1.8 1.5

China 0.6 2.8 4.5

Australia 0.4 0.8 1.0

India 0.1 0.6 1.5

ROTW 4.3 4.3 5.1

Total Market 19.6 27.3 29.9

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Photovoltaics – Growth Worldwide

PV Solar Growth Worldwide

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80% 30%

270%

40%

10%

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Photovoltaics – Growth in the US

US Solar PV Growth

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Photovoltaics – Efficiency

The PV efficiency of today’s commercially available solar cells for terrestrial applications ranges up to 23%. Although this figure is likely to rise in the coming years, the efficiency of PV installations is limited by the laws of physics.

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Photovoltaics – BIPV

The price of a PV installation can be reduced somewhat by integrating the system into a newly constructed building – Building Integrated Photovoltaic (BIPV) systems.

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Photovoltaics – Production

Worldwide solar cell production has been rising at a rate of 30% to 85% annually since 1997, and reached 27 GW in 2010, up from around 10 GW a year earlier, a 120% growth in the PV sector.

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While it didn’t grow as fast as the previous year, global PV cell production still grew and reached a considerable 37 GW in 2011, 36% more than the 27 GW produced in 2010.

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A Brief Glossary of Key PV Terms

Solar radiation:

Radiation originating from Sun, in the 0.3 to 3 µm wavelength spectrum

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Relevant Terminology Relating to Meteorology, Astronomy and Geometry

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A Brief Glossary of Key PV Terms

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Solar spectrum:

Distribution of solar radiation intensity as a function of wavelength or frequency

Relevant Terminology Relating to Meteorology, Astronomy and Geometry

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A Brief Glossary of Key PV Terms

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Direct solar radiation:

Solar radiation arriving at a plane directly from the disc

Relevant Terminology Relating to Meteorology, Astronomy and Geometry

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A Brief Glossary of Key PV Terms

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Diffuse solar radiation:

Solar radiation arriving at a plane after scattering by atmospheric particles (e.g. water droplets, clouds, etc …)

Relevant Terminology Relating to Meteorology, Astronomy and Geometry

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A Brief Glossary of Key PV Terms

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Global solar radiation (Global irradiance G ):

The sum of direct and diffuse solar radiation arriving at a level surface

Relevant Terminology Relating to Meteorology, Astronomy and Geometry

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A Brief Glossary of Key PV Terms

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Power density: (power/area)

Power density of the global

radiation arriving at a plane (W/m2)

Relevant Terminology Relating to Meteorology, Astronomy and Geometry

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A Brief Glossary of Key PV Terms

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Energy density: (energy/area)

Energy density of the global radiation arriving at a plane within a certain time interval calculated by the integration of irradiance G over this time interval (kWh/m2 or MJ/m2)

1 kWh = 3.6 MJ and 1MJ = 0.278 kWh

Relevant Terminology Relating to Meteorology, Astronomy and Geometry

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A Brief Glossary of Key PV Terms

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Pyranometer:

Instrument for measuring the global solar radiation (global irradiance G) on a level surface over the whole wavelength range between approx. 0.3 and 3 µm. (output in µV/W/m2)

Relevant Terminology Relating to Meteorology, Astronomy and Geometry

Page 31: EENG622 - CHAPTER 1a.pdf

A Brief Glossary of Key PV Terms

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Reference cell:

A calibrated solar cell for measuring global solar radiation G. A reference cell replaces the expensive pyranometer.

Relevant Terminology Relating to Meteorology, Astronomy and Geometry

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A Brief Glossary of Key PV Terms

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Solar altitude hs:

Angle between the direction of Sun (center of the solar disc) and the horizontal plane.

Relevant Terminology Relating to Meteorology, Astronomy and Geometry

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A Brief Glossary of Key PV Terms

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Solar azimuth ϒs:

The solar azimuth angle is the angular distance between the zero azimuth (either due South or due North, depending on what you select on the input screen) and the projection of the line of sight to the sun on the ground

Relevant Terminology Relating to Meteorology, Astronomy and Geometry

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A Brief Glossary of Key PV Terms

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Solar generator tilt angle β:

Angle between the solar cell plane and horizontal

Relevant Terminology Relating to Meteorology, Astronomy and Geometry

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A Brief Glossary of Key PV Terms

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Relative air mass number (AM):

where p = local air pressure and p0 = air pressure at sea level

AM1: hs = 90o AM2: hs = 30o

AM1.1: hs = 65.4o AM3: hs = 19.5o

AM1.2: hs = 56.4o AM4: hs = 14.5o

AM1.5: hs = 41.8o

0

.)sin(

1

p

p

hAMmassAir

s

Relevant Terminology Relating to Meteorology, Astronomy and Geometry

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A Brief Glossary of Key PV Terms

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http://pveducation.org/pvcdrom/