An Introduction to Solar Power

Prepared for www.philazine.com by Philip Woodard – 2009 – all rights reserved ©

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World’s Largest Solar Plant

Olmedilla Photovoltaic Park, Spain

162,000 flat solar photovoltaic panels

60 megawatts of electricity

Completed in 15 months at a cost of about $530 million

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Depends on the way sunlight is captured, converted and distributed

Active solar techniques use photovoltaic panels, pumps, mirrors, troughs, and fans to convert sunlight into useful outputs

Passive solar techniques include selecting materials to store heat directly, designing spaces to naturally circulate air, and positioning buildings for most sunlight

Passive or Active

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Passive Solar -- Architecture• Passive systems use natural energy from the sun to

heat a building

• Heating and cooling account for 30% of the energy used in commercial buildings and 50% of the energy used in residential buildings

• Use mass (concrete slabs, tile, masonry and extra-thick drywall or plaster) to absorb and re-radiate solar heat in the occupied spaces

• Use circulating air to cool

• Cheaper than active systems because they are less susceptible to malfunction – reduces energy costs 50% to 90%

• They rely on nature, rather than using mechanical equipment to produce energy

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Passive Solar -- Architecture• Position building and windows for most Sunlight

• Choose compact proportion (a low surface area to volume ratio)

• Select shading and overhangs

• Use sunlight to light interiors and replace artificial lighting for lower temperatures and less air conditioning

• Tailor these to local climate and environment to produce well-lit spaces that stay in a comfortable temperature range

• Use active solar equipment such as pumps, fans and switchable windows to complement passive design and improve system performance

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Passive Solar -- City Planning• Cities can be urban heat islands with higher temperatures

than the the surrounding environment night-time temperatures raised more than daytime

temperatures

• The higher temperatures come from increased absorption of the Sunlight by urban materials such as asphalt and concrete city climates can influence on plant growing seasons up to 10

kilometers (6 miles) away from city edges

• Counteract the increase temperatures by paint-ing buildings and roads white and planting trees

• One Los Angeles program should reduce summer temperatures by about 3 °C at an estimated cost of US $1 billion, giving estimated total annual benefits of US $530 million from reduced air-conditioning costs and healthcare savings

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Active Solar -- Photovoltaics

A solar power technology that generates electricity (direct current) using semiconductors called solar cells

The photovoltaic effect comes when sunlight hits a PV panel; it releases electrons from special layers of silicon and pushes them across an electric field

The first solar cell was constructed by Charles Fritts in the 1880s

Researchers Gerald Pearson, Calvin Fuller, and Daryl Chapin created the silicon solar cell in 1954

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Earliest applications came from U.S. space program, PVs were used as a back-up power source to the Vanguard satellite in 1958 which allowed for continued transmitting a year after its chemical battery was exhausted

A number of solar cells form a solar "Module" or "Panel“ which can then be combined to make solar systems ranging from a few watts of electricity output to multi megawatt power stations

Yearly growth in the solar photovoltaics 2003 to 2008 has averaged more than 40%

Active -- Photovoltaics

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By the 1970s falling prices made PV generation competitive in remote areas without grid access

Early terrestrial uses included telecom-munication stations, off-shore oil rigs navigational buoys and railroad crossings

Off-grid applications accounted for over half of worldwide installed capacity until 2004

Prices fell from US $100.00 per watt in 1971 to US $7.00 watt in 1985

First Solar, the largest manufacturer of thin panels, claims its products will generate electricity in sunny countries as cheaply as large power stations by 2012 8.1

Falling Costs

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Lawrence Berkeley National Laboratory researchers surveyed the costs of 37,000 photovoltaic systems in the U.S.

Average price of installation fell from $10.50 per watt in 1998 to $7.60 per watt in 20079.1

Falling Costs – Part Two

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Solar vs Nuclear 11.1

Location Olmedilla de Alarcón, Spain

Uljin, South Korea

Type Silicon photo-voltaic (PV)

Pressurized light-water

Year 2008 2005

Capacity 528 GWh / yr 8793 GWh / yr

Net generation 88 GWh / year 8108 GWh / yr

Capacity Use 0.17 0.92

Total Cost $0.54 billion $1.76 billion

Cost – Watt of Capacity

$8.95 / Wp $1.76 / Wp

Cost – Actual Watt $53.77 $1.91

Construction time 16 months 55 months

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Photovoltaic Leaders

• Between 1992 and 1994 Japan increased R&D funding, established metering guidelines, and encouraged installations of residential PV systems with subsidies

• Japan’s PV installations climbed from 31.2 MW in 1994 to 318 MW in 1999

• Germany has become the leading PV market: Installed PV capacity has risen from 100 MW in 2000 to approximately 4,150 MW at the end of 2007

• Spain has become the third largest PV market after using Germany’s subsidy plans

• Spain Installed more than 3,000 megawatts of photovoltaic power in 2007, making it the world’s biggest market for that kind of solar power

• Spain increased solar capacity by a factor of 5.4 8.1

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U.S. Installations Rising• In American Southwest, there was a 78% jump in

applications to build solar projects on federal land in 2008

• Applications have risen to 223 from 125• 107 applications for the BLM land in California• 71 applications in Nevada• 35 in Arizona• New Mexico, Utah and Colorado make up the rest• Overall U.S. grid-connected PV capacity is about

800 MW• Top states for PV panels tied to the grid are California

with 530.1 MW, New Jersey with 70.2 MW, Colorado with 35.7 MW and Nevada with 33.2 MW

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Germany’s Gut Erlasee Solar Park

• A 12-megawatt facility located amid cropland near the Bavarian town of Arnstein

• Panels tilt and rotate to stay facing the sun throughout the day

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Thin Film PhotovoltaicsOne venture capitalist says most thin film

photovoltaics (PV) advances fail in the transition from the lab to manufacturing due to yield problems and other manufacturing problems 9.1

Have tended to succeed in the lab, but fail in the manufacturing process.

Only one or two thin-film projects have brought product to market in 30 years, and it's a US $100M-$200M dollar up-front investment "just to play the game and see if your product really works."

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Active Solar – Power TowerSolar “power towers” use a large field of sun-

tracking mirrors called heliostats that face a central tower

They focus the sunlight onto a receiver on its top

The intense energy concentrated onto the tower produces temperatures up to 1,500 degrees Celsius (2,732 degrees Fahrenheit

That energy then heats up water, producing steam that drives a turbine to produce electricity

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Sandia National Laboratories systems look like giant, highly polished satellite dishes

Each dish is a mosaic of 82 mirrors that fit together to form a 38-ft-wide parabola

The mirrors’ precise curvature focuses light onto a seven inch areaThe Heat rises to 1450 F15.1

That heat runs a Stirling engine to make mechanical energy

Hydrogen gas in a Stirling engine’s four 95 cc cylinders expands and contracts as it is heated and cooled, driving pistons to turn a small electric generator. a

CSP Systems– How They Work

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Nine CS9 plants with a combined capacity of 354 megawatts have been operating in the Mojave Desert since their construction between 1984 and 1991 An average coal plant produces about 670 Mw

The nine Provide power to 500,000 homesSpain is pioneering a way to store solar power

A hot liquid can be stored more efficiently than electricity A $5.00 thermos can hold as much energy as heat as a

$150.00 laptop battery does as electrochemical Spain has designed two 50-Mw plants that store heat in a

giant thermos filled with molten salt

CSP Systems– Heat Storage

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New Mexico Plant is U.S. Largest

• 2009 plans for a 92-megawatt solar thermal plant could produce enough electricity to power 74,000 homes

• Built and Run by New Jersey-based NRG Energy for El Paso Power

• Suntower will be built on 450 acres of private land near the Santa Teresa

• It will look like a giant field of mirrors interspersed with 180-foot towers topped by boilers. • Motors on the mirrors will keep them aligned with the

sun.

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Active Solar – CSP Systems

Concentrating Solar Power (CSP) systems use lenses or mirrors and tracking systems to focus a large area of sunlight into a small beam

Auguste Mouchout used a parabolic trough for a solar steam engine in 1866,

The concentrated light is then used as a heat source for a conventional power plant

A wide range of concentrating technologies exists: solar trough, parabolic dish and solar power tower

These methods vary in the way they track the Sun and focus light

In all these systems a working fluid is heated by the concentrated sunlight and is then used for power generation or energy storage

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Active Solar – Solar TroughsPlants like California SEGS use “parabolic

troughs,” curved mirrors that focus the energy onto pipes containing circulating oil

The fluid absorbs the energy and uses it to heat steam to power a standard generator

That drives a turbine to produce electricity

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Active Solar – Two CSP Systems

• Solar trough -- linear parabolic reflector concentrates along the reflector's focal line• follows sun during the daylight hours by tracking along

a single axis• best land-use factor of any solar technology• The SEGS plants in California Segs Nevada’s Solar One

• Stand-alone reflectors concentrate light onto a receiver positioned at the reflector's focal point• Track Sun along two axes• Highest efficiency among CSP technologies• Canberra, Australia’s Big Dish

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Active – Two More CSP Systems

• Stirling solar dish combines a parabolic concentrating dish with a Stirling Heat Engine (normally used to drive electric generators)• higher efficiency of converting sunlight into

electricity and longer lifetime

• solar power tower uses an array of tracking reflectors (heliostats) to concentrate light on a central receiver atop a tower• less advanced than trough systems but offer

higher in efficiency and energy storage • California’s Solar Two and Spain’s Sanlucar La

Mayor

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CSP Systems Problems

• Use four times as much water as a natural gas plant and twice as much as a coal or nuclear plants • Since they heat a fluid that boils water to turn a

turbine, they produces excess heat• They need cooling towers to release heat by

evaporation and use much water

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U.S. -- Best Solar Locations

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ProblemsMost of the cost and operational problems

associated with alternative energy sources arise from the fact that once the energy is converted to heat or electricity, it has to be used right away or stored at enormous cost and trouble

Solar and Wind SynergyIn areas where demand for electricity is higher in winter than in summer, wind and solar are complementaryHigh pressure areas tend to bring clear skies and low surface windsLow pressure areas tend to be windier and cloudierSolar energy typically peaks in summer, but often wind energy is lower in summer and higher in winterThe intermittencies of wind and solar power can somewhat offset each other

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Endnotes 8.1 Chris Goodall, “The 10 big energy myths,” The Guardian, April 7, 2008

BACK

9.1 David Baker, “Cost of Solar has Fallen in Decade,” San Francisco

Chronicle, February 20, 2009 BACK

11.1 “http://uvdiv.blogspot .com/2009/07/test.html,” July, 2009 BACK

15.1 Alex Hutchinson, “Solar Thermal Power May Make Sun-Powered Grid a

Reality,” Popular Mechanics, February, 2009 BACK