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CONCENTRATING SOLAR COLLECTORS

CONCENTRATING SOLAR COLLECTORS. Portland State University Solar Engineering Spring 2008 Carolyn Roos, Ph.D. Washington State University Extension Energy Program. OUTLINE. A review of six concentrating solar technologies and current projects. Basics of ray tracing.

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CONCENTRATING SOLAR COLLECTORS

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  1. CONCENTRATING SOLAR COLLECTORS Portland State University Solar Engineering Spring 2008 Carolyn Roos, Ph.D. Washington State University Extension Energy Program

  2. OUTLINE A review of six concentrating solar technologies and current projects. Basics of ray tracing. Sketch of a thermal analysis example

  3. Solar Concentrating Systems Concentrate solar energy through use of mirrors or lenses. Concentration factor (“number of suns”) may be greater than 10,000. Systems may be small: e.g. solar cooker .... or large: - Utility scale electricity generation (up to 900 MWe planned) - Furnace temperatures up to 3800oC (6800oF)

  4. Concentrating Solar Power:A Revived Industry Utility Action on ~3,000 MW in 2005-06 CSP for Commercial & Industrial Facilities Industrial Solar Tech’s Roof Specs More planned since 2006

  5. States Creating a Market for CSP AZ: 15% RE by 2025, 30% Distributed Generation CA: 20% by 2010 & 33% by 2020 planned CO: 10% by 2015 NV: 20% by 2015, 5% Solar NM: 10% by 2011 TX: 4.2% by 2015

  6. In a Carbon Limited Future… Carbon limits will close the cost gap. CSP can scale up fast without critical bottleneck materials. (e.g. silicon) Costs will come down with increase in capacity expected to fall below natural gas in the next few years. In the very near future, the CSP market in the SW US can grow to 1 to 2 GW per year. From: http://www.nrel.gov/csp/troughnet/pdfs/2007/morse_look_us_csp_market.pdf

  7. Examples of CSP Applications • Power Generation: • Utility Scale: 64 MW Nevada Solar One (2007) • Buildings: 200 kW “Power Roof” • Thermal Needs: • Hot Water and Steam (Industrial & Commercial Uses) • Air Conditioning – Absorption Chillers • Desalination of seawater by evaporation • Waste incineration • “Solar Chemistry” • Manufacture of metals and semiconductors • Hydrogen production (e.g. water splitting) • Materials Testing Under Extreme Conditions • e.g. Design of materials for shuttle reentry

  8. Primary Types of Solar Collectors Parabolic Trough Compact Linear Fresnel Reflector new Solar Furnace Parabolic Dish & Engine Solar Central Receiver (Solar Power Tower) Lens Concentrators Can be used in conjunction with PV: Use lenses or mirrors in conjunction with PV panels to increase their efficiency. (http://seattle.bizjournals.com/seattle/stories/2006/04/24/focus2.html)

  9. PARABOLIC DISH & ENGINE FRESNEL REFLECTOR LENS CONCENTRATORS PARABOLIC TROUGH PARABOLIC DISH SOLAR FURNACE SOLAR FURNACE CENTRAL RECEIVER

  10. Major Components of Solar Collector Systems Concentrating mirror(s) May use primary & secondary concentrators. Absorber within a Receiver Receiver contains the absorber. It is the apparatus that “receives” the solar energy; e.g. evacuated tube. Absorber absorbs energy from concentrator and transfers to process being driven (engine, chemical reactor, etc.); e.g. the pipe within an evacuated tube. Heliostats Flat or slightly curved mirrors that track the sun and focus on receiver or concentrator. Used with solar furnaces and power towers.

  11. Parabolic Troughs Most proven solar concentrating technology The nine Southern California Edison plants (354 MW total) constructed in the 1980’s are still in operation

  12. Parabolic Troughs - Operation • Parabolic mirror reflects solar energy onto a receiver (e.g. a evacuated tube). • Heat transfer fluid such as oil or water is circulated through pipe loop. (250oF to 550oF) • Collectors track sun from east to west during day. • Thermal energy transferred from pipe loop to process.

  13. Parabolic Trough System - Can be hybrid solar / natural gas - New systems include thermal storage.

  14. Thermal Storage Uses high heat capacity fluids as heat transfer storage mediums 12 to 17 hours of storage will allow plants to have up to 60% to 70% capacity factors. From: http://www1.eere.energy.gov/solar/pdfs/csp_prospectus_112807.pdf

  15. Thermal Output of Hybrid Plant with Thermal Storage

  16. What Have Been the Technical Challenges? Development of Materials Heat transfer tubes that are less prone to sagging & breaking. Improved surface material of heat transfer tubes.  High absorptivity, low emissivity and long-term stability in air. Low cost mirrors that have reflectivity and washability of glass. Improved Components Flex hoses used to join sections of pipe loop were prone to failure  Replaced with ball joint design. Ability to track on tilted axis Improved Processes e.g. Generate steam directly instead of running heat transfer fluid through heat exchanger - Improves efficiency but more difficult to control.

  17. “First Solar Thermal Parabolic Trough Power Plant Built in The U.S. In Nearly Two Decades to Be Dedicated On Earth Day” (2005) • Saguaro Solar Generating Station (north of Tucson) • 1MW - Compared to 395MW in natural gas fired generating capacity at same site • Broke ground March 24, 2004 and started generating power December 2005 • Built by Solargenix, subsidiary of ACCIONA Energy of Spain • Arizona has goal of 15% renewable energy by 2025. • $6 Million Project

  18. Saguaro Solar Generating Station 1MW - 2005

  19. Nevada Solar One64 MW - 2007 Now producing 64 MW on 140 hectares Located in Eldorado Valley (south of Las Vegas) One of the world's largest CSP plants. Cost: $262 million Developed by Solargenix Energy. SHOTT North America provided receivers.  Groundbreaking in February 2006 On line in June 2007.

  20. Nevada Solar One64 MW - 2007

  21. Around the World Granada, Spain. Two 50 MW plants Developed by Solar Millenium AG Negev desert of Israel 150 MW facility to be expanded to 500 MW Developed by Solel (successor company to Luz)  Cost $1 billion

  22. Parabolic Troughs on a Smaller Scale:SolarGenix “Power Roof” (2002) Parker Lincoln Building (demonstration) Design point of 176 kW Provides 50 tons of absorption cooling

  23. Parabolic TroughsLinks for More Info http://www.iea-ship.org/index.html http://www.solarpaces.org/solar_trough.pdf http://www.nrel.gov/docs/fy04osti/34440.pdf Heat Transfer Analysis: http://www.nrel.gov/docs/fy04osti/34169.pdf Ball Joint Design: http://www.eere.energy.gov/troughnet/pdfs/moreno_sf_interconnections_with_salt_htf.pdf

  24. Linksto Parabolic TroughProjects and Technology Examples http://www.solargenix.com/power_plant_tech.cfm http://www.solargenix.com/building_products.cfm http://www.us.schott.com/solarthermal/english/index.html http://www.us.schott.com/solarthermal/english/products/receiver/details.html http://www.inderscience.com/search/index.php?mainAction=search&action=record&rec_id=6745 http://www.sete.gr/files/Ebook/2006/Hospitality_Day_Lokurlu.pdf http://www.eere.energy.gov/troughnet/pdfs/lewandowski_vshot.pdf http://www.capitalsungroup.com/files/rmt.pdf http://www.industrialsolartech.com/

  25. Preview… Sketch of thermal analysis and design for parabolic trough system at the end of this presentation.

  26. Compact Linear Fresnel ReflectorsAusra, Inc.http://www.ausra.com/ Makes moot some of the design challenges and weaknesses of parabolic troughs.

  27. Compact Linear Fresnel Reflectors A series of long, shallow-curvature mirrors Focus light on to linear receivers located above the mirrors.

  28. Compact Linear Fresnel Reflectors Lower costs compared to parabolic troughs Several mirrors share the same receiver Reduced tracking mechanism complexity Stationary absorber No fluid couplings required Mirrors do not support the receiver Denser packing of mirrors possible Half the land area

  29. 6.5-megawatt demonstration power plant under construction in Portugal (as of September 2007) Ausra and PG&E announce purchasing agreement for 117 MW facility located in central California (November 2007) Compact Linear Fresnel ReflectorsProjects

  30. Parabolic Dishes - Plataforma Solar de Almeria – DISTAL I and II - Dish with receiver for Stirling Engine

  31. Parabolic Dish/Engine - Operation Solar energy drives a Stirling engine or Brayton cycle engine (gas turbine.) Receiver absorbs solar energy and transfers it to the engine’s working fluid. Systems are easily hybridized since Stirling engines can run on any external heat source.

  32. State of Dish Technology • Mature and Cost Effective Technology: Large utility projects using parabolic dishes are now under development. • Technical Challenges Have Been: • Development of solar materials and components • Commercial availability of a solar-izable engine. • Advantage: High Efficiency • Demonstrated highest solar-to-electric conversion efficiency (still true with advances in CPV? No.) • Potential to become one of least expensive sources of renewable energy. (still true with development of Fresnel reflectors?) • Advantage: Flexibility • Modular - May be deployed individually for remote applications or grouped together for small-grid (village power) systems.

  33. Stirling Energy Systems, Inc.

  34. Stirling Engines Stirling engines are simple, have high efficiency (25% for industrial heat), operate quietly, have low O&M costs (~$0.006/kWh) Waste heat can easily be recovered by the engine, as well as from the engine According to one manufacturer: $1000-2000/kW installed But They have higher costs for materials and assembly, are larger for same torque, have longer start up time (needs to warm up)

  35. Relatively small units are available.e.g. Stirling Danmarkhttp://www.stirling.dk/default.asp?ID=121 … though these are designed for biopower

  36. Infinia Corphttp://www.infiniacorp.com/applications/Prod_Spec.pdf

  37. Stirling Engine Manufacturers Stirling Denmark:  http://www.stirling.dk/ STM Power: http://www.energysolutionscenter.org/distgen/AppGuide/Manf/STMPower.htm QRMC Infinia: http://www.infiniacorp.com Stirling Cycles has been acquired by Infinia. ReGen Power Systems: http://www.rgpsystems.com/ Stirling Energy Systems: http://www.stirlingenergy.com/.  Currently manufacturers large utility-scale Stirling engines for use with solar concentrating systems.  Has plans to produce engines for use with combustible fuels in the future. Stirling Biopower: http://www.stirlingbiopower.com/.  In the start up phase (as of July 2007)

  38. Receiver Tubes for Stirling Engine Located at focus of dish to absorb heat.

  39. From: www1.eere.energy.gov/solar/pdfs/csp_prospectus_112807.pdf

  40. SDG&E (2005) 300 MW From 12,000 Stirling Solar Dishesin Imperial Valley, Southern CA San Diego Gas & Electric entered 20-year contract with SES Solar Two, an affiliate of Stirling Energy Systems in 2005. 12,000 Stirling solar dishes providing 300 MW on three square miles Two future phases possible that could add 600 MW At 900 MW would be one of the largest solar facilities in the world.

  41. SCE (2005) 500 MW from 20,000-Dish Arrayin Mojave Desert Southern California Edison will construct 500 MW solar generating station on 4500 acres: Approved by CPUC in Dec 2005 Using SES dishes First phase: 20,000-dish array to be constructed over four years Option to expand to 850 MW.

  42. A news story on these two projects… SAN DIEGO, California, US, September 14, 2005 (Refocus Weekly) An electric utility in California will buy 300 MW of solar power from a new facility that uses Stirling solar dishes. San Diego Gas & Electric will buy the green power under a 20-year contract with SES Solar Two, an affiliate of Stirling Energy Systems of Arizona. The 300 MW solar facility will consists of 12,000 Stirling solar dishes on three square miles of land in the Imperial Valley of southern California.SDG&E has options on two future phases that could add another 600 MW of renewables capacity and, if the plant grows to 900 MW within ten years, it would be one of the largest solar facilities in the world. The utility also announced the purchase of 4 MW of energy from a local biogas landfill project.SES says the contract is the second record-breaking solar project it has signed in the past month, following a contract with Southern California Edison for construction of a 4,500 acre solar generating station in southern California. That 20-year power purchase agreement, which also must be approved by the CPUC, calls for development of 500 MW of solar capacity in the Mojave Desert, northeast of Los Angeles.The first phase will consist of a 20,000-dish array to be constructed over four years, with an option to expand the project to 850 MW.

  43. Salt River Landfill Demonstration ProjectFour 22 kW SunDishes Each 'SunDish' is 50' high. Stretched-membrane faceted dishes deflected to convex form by vacuum. Reflective surface is made of sheets of 1.0 mm low-iron glass. Stirling engines and generators manufactured by STM Corporation. Electricity is used by the landfill facilities. Efficiency is “20% higher than other solar systems of a similar size.” Hybrid system: Stirling engines can run on solar energy, landfill gas or other liquid or gaseous fuels.

  44. STM’s Sun Dish System From: http://www.energysolutionscenter.org/distgen/AppGuide/DataFiles/STMBrochure.pdf

  45. Small Scale & Low Tech Parabolic Dish with Solar Cookers Using parabolic dish concentrators on a smaller scale...

  46. Solar Furnaces Centre National de Recherche Scientifique - Odeillo, France Largest solar furnace in the world (1 MWt)

  47. Solar Furnaces - Operation • Solar furnaces are used for: • - High temperature processes  “Solar Chemistry” • - Materials testing • A field of heliostats tracks the sun and focuses • energy on to a stationary parabolic concentrator • which refocuses energy to the receiver. • Receivers vary in design depending on process: • Batch or continuous process • Controlled temperature and pressure • Collection of product (gas, solid, etc.)

  48. Why Run Processes in a Solar Furnace? • Higher Temperatures (up to 3800oC) • Higher temperatures are possible in solar furnace than in conventional combustion furnace or electric arc furnace. • Cleaner Processes • e.g. Electric arc furnaces use carbon electrodes which often contaminate product. Energy Sustainability • Use of renewable energy for industrial processes.

  49. Electricity through Solar Chemistry Example: Water splitting: 2H2O → 2H2 + O2

  50. Solar FurnacesTechnical Challenges • From test bench to commercial scale processes • Development of continuous processes from batch experiments • Material Development • Materials suitable for very high temperatures. • Process Control • e.g. Accurate measurement of high temperatures

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