Solar Energy l l l Solar Energy or

“Solar Energy” l l l ‘Solar Energy’ or ‘Renewable Energy’ ‘Sustainability’ Solar or Renewable Energy – Solar ‘Radiant’ Energy – Wind Energy – Biomass Energy – Hydro and Wave Energy – Geothermal Energy **

Some ‘Solar’ Energy History § Solar Energy Use is Not New § In Use well before Our Discovery of Oil § Is the Source of our Coal and Oil

Augustin Mouchot’s largest ‘Sun Machine’, on display at the Universal Exposition in Paris, 1878

An Eneas ‘Sun Motor’ - 4 H. P. Solar Thermal Powered Steam Engine - on farm in Arizona, 1904

A Maryland Gentleman of the 1890’s enjoys a Hot Bath provided by a Climax Solar Water Heater l Climax Solar Water Heaters were sold extensively between 1890 and about 1920. l Later, the Day and Night Co. was a major supplier of solar hot water systems.

Solar Water Heating in Los Angeles, circa 1900 • Olive Street in LA in 1900. • Three buildings using ‘Climax Solar’ water heaters ($25) …. • A major solar collector boom from 1891 to 1930. (Note the ‘clear’ skies)

“Bell System Solar Battery Converts Sun’s Rays into Electricity”, Advertisement from Look Magazine, 1956.

Photovoltaics (PV)

How PV cells work

How ‘Silicon’ cells are made

Other Types of Solar Cells l Poly-crystal l Ribbon type ------> l Thin Film

Commercial Solar Cells l Single crystal silicon l Poly-Crystal Silicon l Thin Films

Emerging Technolgies Nano-solar techniques • Nano. Solar – Electrically Conductive Plastics • Konarka – Polymer and dye-sensitized solar cell have flexible cells about 5 % efficient

Cells, Modules and Arrays

Energy Tid-bit l The solar cells in the early 1950 s were about 0. 5 % efficient. Today a module is about 15 % efficient. l A 1 k. W system: § In 1950 = 2, 400 square feet § In 2005 = 80 Square feet

Typical PV Systems

1. 5 k. W PV Array - Vliet Residence, Austin TX, 2000

Building Integrated Photovoltaics (BIPV) Roof Shingles (many other examples)

PV System Installation on Roof of Commercial Building

BJ’s Wholesale Club & Sun Power Electric

Solar - Electric Car

PV Market

California Solar Business Development (480 Companies Installed 26 MW in 2003)

PV Module Manufacturing Cost

The Major PV Cell/Module Manufacturers

PV Energy Tid-bit • • Energy required to manufacturer singlecrystal silicon PV modules will be produced by the module in 1. 5 to 2. 5 years. Thereafter the energy produced is a net gain. PV modules are expected to last beyond 20 years. Energy costs for some of the emerging technologies are expected to be lower.

Solar Thermal Swimming Pool Heating l Solar Cooking l Space Heating l Solar Hot Water l Solar Cooling l Ocean Thermal (Electric) l Solar Thermal (Electric) l

Swimming Pool Solar Heater, Austin, TX, late 1970’s

Collector for Solar Water Heating - Vliet Residence, Austin, TX, 1977

Simple Paybacks for Solar Water Heating against Electricity

Passively Heated Asphalt Storage Tank - Midland, TX, mid - 1980’s

Tracking-Concentrating Collectors for UT Solar Cooling project, late 1970’s

Solar Furnace in French Pyrennes - Tracking Heliostats and Parabolic Reflector

Power Tower or Central Receiver type Solar Thermal Electric Power Generation

10 MWe Solar Power Plant - Barstow, CA, circa mid - 1980’s

Luz Parabolic Trough Collector Field for Thermal Electric Power Generation, about 600 MWe, Kramer Junction, CA, late 1980’s

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Thermal Energy Storage • • • Thermal energy storage (TES) systems heat or cool a storage medium and then use that hot or cold medium for heat transfer at a later point in time. Using thermal storage can reduce the size and initial cost of heating/cooling systems, lower energy costs, and reduce maintenance costs. If electricity costs more during the day than at night, thermal storage systems can reduce utility bills further. Two forms of TES systems are currently used. The first system used a material that changes phase, most commonly steam, water or ice. The second type just changes the temperature of a material, most commonly water. 38

TES Economics Are Attractive for l l l High utility demand costs Utility time-of-use rates (some utilities charge more for energy use during peak periods of day and less during off-peak periods) High daily load variations Short duration loads Infrequent or cyclical loads 39

Methods of Thermal Energy Storage • TES for Space Cooling: produce ice or chilled water at night for air conditioning during the day – Shifts cooling demands to off-peak times (less expensive in areas with real-time energy pricing) – May be used take advantage of “free” energy produced at night (like wind energy) • TES with Concentrated Solar Power: store energy in thermal fluid to use when sunlight is not available – Gives solar concentrating power plants more control over when electricity is produced • Seasonal TES – Long term energy storage – Store heat during the summer for use in the winter • Many other methods 40

TES for Space Cooling: Calmac’s Ice. Bank® Technology Charge Cycle: At night, a chiller is used to cool a water/glycol solution. This runs to the Ice Bank, where water inside the tank is frozen. Discharge Cycle: During the day, the glycol solution is cooled by the ice in the tank and then used to cool the air for the building’s AC needs. http: //www. calmac. com/products/icebank. asp 41

An Inside View of the Ice. Bank® l l l Coolant runs through tubes Water in the tank gets frozen by the coolant at night The ice is then used to cool the solution during the day for air conditioning http: //www. calmac. com/products/icebank. asp 42

Why Use TES for Space Cooling? l Shifts electricity demands to the night to take advantage of lower rates at night • Can also be a way to take advantage of wind power, which is more abundant at night http: //www. calmac. com/benefits/ 43

UT’s Thermal Storage System l l l Acts as chilling station, but with 1/3 of the cost 4 million gallon capacity 30, 000 ton-hours of cooling (~105 MWh) – Enough to run A/C for 1500 Austin homes (2500 sq ft) each day Kriti Kapoor 44

TES with Concentrated Solar Power (CSP) • CSP technologies concentrate sunlight to heat a fluid and run a generator • By coupling CSP with TES, we can better control when the electricity is produced 45

l TES with Concentrated Solar Power (CSP) Two-tank direct method – Two tanks, hot and cold – Heat transfer fluid flows from the cold tank and is heated by the solar collectors. – This hot fluid travels to the hot tank, where it is stored. – As needed, the hot fluid passes through a heat exchanger to make steam for electricity generation. l Other methods include twotank indirect (where the heat transfer fluid is different than the storage fluid) and singletank thermocline (storing heat in a solid material) The two-tank direct method http: //www 1. eere. energy. gov/solar/thermal_storage. html 46

Seasonal Thermal Energy Storage Drake Landing Solar Community (Okotoks, Alberta, Canada) http: //www. dlsc. ca/how. htm 47

Annual Energy Savings at Drake Landing http: //www. dlsc. ca/brochure. htm 48

Incentives l Newly passed 30% Federal Tax Credit (Recall federal tax credit of 40% back in early 1980’s. ) l State of Texas: - S. B. 20 - Extends Renewable Energy Portfolio Standard to 2015. [The Renewable Energy Credits (REC’s) are a means to insure that providers of electric power have the necessary amount of renewable energy in their portfolio. ] - S. B. 982 - Tightens Energy Conservation Requirements in State Buildings. [Deals with Renewables and Sustainability. ] l Wind Production Tax Credit: 1. 6 - 1. 9 cents/k. Wh, extended through 2007

City of Austin Rebate Program l Pays for up to 70 % of the cost of an installed PV system (started 2005) - Rebate expected to decrease with time - For residential and commercial buildings - Residential systems typically 1. 5 to 3 KW - Almost 1 MW installed to-date - A goal of 15 MW by 2007 l Projected increase in solar HW rebate - from $300 to max. of about $600 - systems cost $3000 to 4000

Solar Land Area Requirement • • Solar Insolation in West Texas (Pecos): Varies during year from about: 3. 5 to 7. 5 k. Wh/m 2 -day during year. Annual average of 6 k. Wh/m 2 -day Assume PV or Solar Thermal conversion efficiency of 7. 5% (half of current commercial PV) Land Area = 850 GWe/(6/24 k. W)(1609 x 1609)(0. 075) = 17510 sq/mi. or about 133 mi. x 133 mi. • See Map of US. for Solar Land Area.

Land Requirement for Solar to Produce Future US Electricity Demand

Comments on Comparisons l Nuclear: can operate at high capacity factor. - major water cooling requirement l Wind: Must operate at a much lower capacity factor …… maybe 30%, and maximum penetration into grid of about 20%. - Takes little land area out of ‘production’ - Requires no water cooling l Solar: Seasonal, intermittent and diurnal variations. Must also operate at much lower capacity factor. - covers ‘much’ of the land area, but land of low productivity. - area could be rooftops, distributed generation (good) - no water cooling required if PV What’s needed …… cheap storage !!! About $0. 10/k. Wh •