1. Chapter 9
Solar And Wind Power
&
Battery Storage

2. Solar Energy
Fusion takes place in the core and takes a million years for a photon of light to reach the surface

3. Produces electricity during daylight hours when most needed
Solar Energy
Produces electricity during daylight hours when most needed
More reliable than wind because sun rises and sets on schedule
Cut significantly by clouds and by sun being near horizon
Seasonal (winter sun does not rise as high as summer sun)
Sun’s ultraviolet light

4. In the 5th Century, the Greeks incorporated passive solar design in their buildings by allowing the southern sun to penetrate interiors for warmth in the winter

5. In 212 BCE, Archimedes focused sunlight with polished bronze shields on a Roman fleet attacking Syracuse and succeeded in setting ships afire

6. Justinian Code ( ) included laws regarding “sun rights” to ensure that houses and buildings had continued access to sunlight after their construction

7. Energy from sun tapped by: Minimal cloud cover (deserts)
Solar thermal heaters
Solar thermal electricity
Solar photo voltaic electricity (PV)
Red areas best for extracting solar power
Minimal cloud cover (deserts)

8. Solar heaters take heat of sun and warms water that can be used as hot water for washing clothes, showers, or heating a home
Solar heating units being built and installed rooftops of developing
nations for home hot water such as India, Egypt, and others by
local entrepreneurs

9. Thermal solar energy totaled 269 GW in 2012 vs 40 GW solar photovoltaic in 2010

10. Installing roof top solar thermal hot water heaters a cottage industry in Egypt and elsewhere

11. Solar Thermal Capacity (Gigawatts)
Figure 9.1
Solar Thermal Capacity (Gigawatts)

12. First solar power plant to produce steam
“Eventually industry will no longer find in Europe the resources to satisfy its prodigious expansion... Coal will undoubtedly be used up. What will industry do then?”
Augustin Mouchot
( )
First solar power plant to produce steam

13. In 1912 Frank Shuman ( ) built parabolic solar collectors near Nile River to run steam-pumps to irrigate desert land
Wanted to build 20,000 square miles (!) of reflectors

14. Solar Thermal Power Plant Design

15. Historical Development Solar Thermal Electricity Capacity (Gigawatts)
Figure 9.2
Historical Development Solar Thermal Electricity Capacity (Gigawatts)

16. Solar Thermal Energy for Electricity Generation
Solar Power Tower
A circular field array of heliostats (large mirrors) individually tracks the sun
The heliostats focus sunlight on a central receiver which heats molten salt that via heat exchanger feeds steam to generator to produce electricity

17. Natural gas or bio fuel by night
Trestin Bio (Hybrid)
Solar by day
Natural gas or bio fuel by night

18. SolarReserve
Thermal tower 600’ in Nevada
Surrounded by 10,000 mirrors sized as large as billboards
110 MW output
Molten salt stores energy which can be converted to electricity on demand—more reliable than solar panels

19. Trough-shaped parabolic mirrors automatically follow the sun and focus the sun’s rays at 30 to 60 times their normal intensity on a receiver pipe filled with synthetic oil—heat exchanger to produce steam to generate electricity

21. Thermal solar electricity plants under construction/development
(19,777 MW Total)
Parabolic Trough Power Tower Dish
CSP – Concentrated Solar Power

22. Installed cost solar thermal plants: $5.80 per watt
Dark Day for Solar Thermal: Solar Trust Switches 500MW Power Plant to PV
In 2011, including above, 3 gigawatts of solar thermal electricity generating projects have been converted to PV projects
Installed cost solar thermal plants: $5.80 per watt
As consequence of falling manufacturing cost of solar panels
Installed cost of utility-scale PV installation: $3.40 per watt
Source: and

24. Heated fluid transfers its heat to a gas such as hydrogen or helium to power a Stirling engine similar in construction to an internal combustion engine, or to a Brayton engine similar to a gas turbine engine (referred to as a micro-turbine).
In neither case is there combustion; the engines run off the energy of the heated gas and drive an electricity generator—efficiency of 30% highest of all solar thermal power plants
No water needed as in power towers and parabolic mirror systems
Power output limited <5 MW and too
sophisticated compared to PV

25. First to study photovoltaic effect
Edmund Becquerel
( )
First to study photovoltaic effect

26. Charles Fritts
( )
First working model of a solar cell in 1883 who coated a semiconductor (selenium) with a thin layer of gold in 1883 to produce the first working first photovoltaic (PV) solar cell

27. Solar Photovoltaic (PV) Solar Power

28. Historical Development of Solar Power (Gigawatts)
Figure 9.3
Historical Development of Solar Power (Gigawatts)

29. Commercial solar panels require mechanical support and have an efficiency of around 18%
Energy output over lifetime of service vs energy input during manufacture and installation is a factor of 4 (for wind it is 80)

30. Solar Panel Park or Farm
Once built, energy free and virtually maintenance free for 25 years

31. Building a solar panel park

32. Installed costs falling rapidly

33. Cost of grid electricity rising, but cost of solar electricity declining

34. Table 9.1 Economic Analysis of Actual Solar Energy System
Aggregate Savings (Costs)
Over 25 Year Life of Project
Avoided Electricity Purchases
$2,415,000
Avoided Transformer Losses
$50,000
Estimated Sales of Electricity Back to Utility First Four Years Only
$315,000
Maintenance of Solar System and Roof
($110,000)
Aggregate Savings
$2,670,000
Cost of System Net of Rebate
$1,145,000
Internal Rate of Return over 25 Year Period
8.3%

35. Solar PV Power (Gigawatts)
Figure 9.4
Solar PV Power (Gigawatts)

36. Required $/kWh versus $/W Installed Cost
Figure 9.5
Required $/kWh versus $/W Installed Cost

37. Energy Source for New US Power Plants in 2013 (Gigawatts)
Figure 9.6
Energy Source for New US Power Plants in 2013 (Gigawatts)

38. Thin solar film can be applied directly without need for panel support
Efficiency around 12%, less than solar panels

39. Thin film solar panels being applied directly to the roof
Intent is to have thin film solar roofing material that can substitute for conventional roofing material

40. Solar and wind and biofuel projects helping to bring electricity to isolated parts of the world not connected to an electricity grid
Require batteries to store electricity when sun is not shining,
but provides power during peak (daylight) periods

41. Four Primary Applications for PV Power Systems
Off-grid domestic system: provide electricity to households and villages not connected to the utility electricity network
Off-grid nondomestic installations: first commercial application such as telecommunication, satellite, and navigation aids
Grid-connected distributed PV systems: provide power to a grid-connected customer.
Grid-connected centralized systems: perform the functions of centralized power stations

43. But desert locations have disadvantages:
Dust or sand accumulations must be removed from solar panels—generally using water
Wind with sand grains scour solar panel surfaces reducing their efficiency if not protected by glass
Some locations are maintenance-free without scouring

44. Solar Power Updraft Tower

45. Integrating solar and hydro power
Sun tracking solar panel installations floating on calm waters of hydro electric power reservoirs
Solar power utilizes under-utilized hydro electrical system (avg output hydro plant 40%)
Solar power peaks along with daily demand peak
augments hydropower output
saves reservoir water for when it is more needed
Prototype installation being built in India

46. Good news: solar output peaks during peak demand for electricity
Bad news: peak is short-lived and overcast skies significantly
reduce output

47. Suppose that sunlight can be modeled by the following probability distribution for the indicated time of day

48. The discrete probability associated with each hour of the day can be taken off the probability distribution
The conversion to MW-Hrs is the ratio that 15.4% is maximum output of 1 MW-Hr

49. Without cloud cover, the capacity of a 1 MW solar panel installation
compared to a 1 MW coal fired generator is 6.49/22.8 or 28%
Suppose there is a 60% chance of cloudless days and 40% of cloudy days
Total overcast sky: power output 30%

50. Output reflects 60% chance of no cloudiness
Mean output of 5.55 when compared to coal plant is 24%

52. Future Directions
Sun Catalytix
Silicon solar cell has different catalytic materials bonded onto its two sides—needs no external wires or control circuits to operate.
Paced in a container of water and exposed to sunlight, it quickly begins to generate streams of oxygen bubbles from one side and hydrogen bubbles from the other
Costly and inefficient (2.5%) at present

53. Joule Unlimited
Specially genetically modified organisms can directly convert waste water, CO2, and sunlight to diesel and ethanol with no intervening steps

54. Xtreme Concentrated Photovoltaics, XCPV
(SUNRGI Corp)
Tracks sun and uses magnifying glass to focus light on PV cells
needs cooling—37% efficiency over 17% nominal efficiency

55. Applying nanotechnology to solar panels
Tiny nanospheres silica covered with silicon—silica removed with hydrofluoric acid
Light trapped within spheres markedly increases efficiency of thin
film solar

56. Technological Goals
Increase efficiency from 20% to 50% or more
Sharply reduce manufacturing costs/solar output
If successful, will bring solar power into mainstream of power generation

57. Wind
Wind results from differences in air temperature, density, and pressure
from uneven solar heating of the earth’s surface
Like ocean currents, wind currents act as
giant heat exchangers: Cooling the tropics
Warming the poles
Consistent winds:
Through passages between mountains (California)
Alongside mountain chains (east side of Rockies)
Coastlines where sea breezes and land breezes alternate between day and night (NJ and DE)
Offshore waters (Europe)

58. Wind Energy: Long Exploited
5000 BC in Egypt
Egyptians dug canals to haul food and stone from inland sources to Nile River not unlike our interstate highway system

59. Age of Exploration
Triangular sail invented in Arabian waters key to tacking into wind
Model of Columbus’ Sailing Vessel

60. Clipper Ships: End of an Era
America’s response to British steamships
Lasted only a few decades
Doomed by:
Reliability of coal propulsion
Suez Canal shortening
voyage for steam ships
Europe to Asia
Lesson:
Cannot stop technological progress!

61. Horizontal Windmill (Primary rotating axis is horizontal)
Gearing necessary to translate to vertical axis to turn grindstones to convert wheat to flour
Historically speaking, many societies incapable of technically changing direction of power axis
Holland created by building dikes to keep back the sea and thousands of windmills to pump out the water

62. Modern Vertical Wind Turbines (Vertical Axes)

63. Long history of windmills in development of the West
Little surface water
Windmills pumped water for
humans and animals
Water for steam locomotives
Later generated electricity for isolated farm homes

64. Wind turbine development mainly financed by government programs
Wind turbine farms depend on various tax credits and grants
Favorable wind locations normally in isolated areas and require building long distance transmission lines to population centers
Government inducements include requiring utilities to have a set percentage of power supplies being renewable and allowing higher rates to be charged to customers

66. Total US potential wind capacity
Hub distance
80 meters: 10,500 GW
100 meters: 12,125 GW
Current capacity: GW
Capacity factor: %
Sufficient to power the US
Plains states
Average wind speed of 9 m/s
9*3.3 ft/m * 3600 sec/hour/5280 ft/mile
20.2 mph average!

67. Offshore wind farms can take advantage of
greater average wind speeds for greater output, but at a higher capital cost

68. Europe: Annual Additions to Installed Offshore Wind Capacity (gW)
Figure 9.7
Europe: Annual Additions to Installed Offshore Wind Capacity (gW)

69. 2012 Offshore Installed Wind Turbines (gW)
Figure 9.8
2012 Offshore Installed Wind Turbines (gW)

70. Wind farms are more price competitive than solar electricity and comparable to fossil fuel plants

71. Global Installed Wind Power (gW)
Figure 9.9
Global Installed Wind Power (gW)

72. 2014 Wind Power Capacity by Nation (gW)
Figure 9.10
2014 Wind Power Capacity by Nation (gW)

73. Table 9.2 World’s Largest Wind Turbine Manufacturers
Company
Percent Market
Share
Description
GE Energy (US)
15.5
16, mW installed plus 2.5 mW plus 4.1 mW built for offshore
Vestas (Denmark)
14.0
43,000 turbines in 66 nations including 1.8 and 2.1 mW for onshore, 3 mW for low wind conditions plus 3 mW for offshore via MHI Vestas joint venture
Siemens (Germany)
9.5
Market leader offshore turbines 2.3 mW, 3.6 mW and 6 mW with 150 meter diameter rotor
Enercon (Germany)
8.2
20,000 turbines worldwide including 2 mW, 2.5 mW (light winds), 3 mW and 7.5 mW
Suzlon Group (India)
7.4
21.5 gW of installed capacity including 2.1 mW for normal and light winds. German subsidiary is REpower mW
Gamesa (Spain)
6.1
18 gW of installed capacity including 2 mW, 4.5 mW and 5 mW (offshore)
Goldwind (China)
6.0
World’s leading manufacturer of permanent magnet direct drive turbines including 1.5 mW and 2.5 mW; other leading Chinese manufacturer is Sinovel

74. Annual Market Forecast by Region 2013-2018 (gW)
Figure 9.11
Annual Market Forecast by Region (gW)

75. Projected Growth of Wind Power (gW)
Figure 9.12
Projected Growth of Wind Power (gW)

76. US States With More Than 2 gW Installed Wind Power
Figure 9.13
US States With More Than 2 gW Installed Wind Power

77. California state requirements placed on utilities on renewable energy sources provided impetus for the first major wind farms

78. California initiated concepts:
Renewable Portfolio Standard (RPS): utilities must provide certain percentage of their electricity from renewable energy sources—utilities select source on basis of lowest cost or may be directed to use a particular source
Feed-in-Tariff (FIT): electricity charge by renewable energy sources must cover capital and operating costs—
private investment is now feasible
Often costs are subsidized either directly (investment subsidies) or indirectly (reduced taxation)
If FIT is higher than rates for conventional electricity, consumers end up paying the difference

79. China: Annual Installed and Cumulative Wind Power (gW)
Figure 9.14
China: Annual Installed and Cumulative Wind Power (gW)

80. China’s Provinces

81. Wind Power Capacity in Provinces of China (gW)
Figure 9.15
Wind Power Capacity in Provinces of China (gW)

82. Daliang Wind Station outside Anxi in Gansu Province
Six wind farms each GW—enough to keep China in first place

83. Nature of State Support Programs for Renewable Energy
Access laws to ensure access to transmission system
Issuance of state bonds to help finance projects
Construction and design criteria
Contractor licensing and equipment certification
State corporate, personal, property, and sales tax incentives
Grants and loans
Electricity production incentives
Rebates on costs
Required green power generation
Renewable portfolio standards
States have 1—18 individual green power policies

84. Annual Additions to US Wind Power Capacity (gW)
Figure 9.16
Annual Additions to US Wind Power Capacity (gW)
Highly addicted to wind subsidies

86. A proposal:
line the entire NJ and DE coastline with wind turbines will make both states electricity exporters to other states
Shore has consistent land and sea breezes that alternate between
night and day

87. Government permits necessary for constructing wind farms (as with just about everything else) —wind farms off Cape Cod and Long Island killed by environmental objections during permitting process

88. But one made it through the environmental hurdles: Deepwater Wind
First US offshore wind 30 mW, 5 turbine Block Island Wind Farm scheduled to be online in 2016
This should encourage building of other offshore wind farms

89. Electricity drives motor that powers a fan— wind powers a fan (blades) to generate electricity

90. Modern wind turbines – not always spinning like this –
actual output varies depending on location
Best locale – highest average daylight hour wind speed

91. Determining 1 MW wind turbine output given variation in wind speed

92. Need to know wind variation at a locality
Suppose that historical data suggests that average speed is 15 mph that can be described by above probability distribution

93. Assumed Wind Turbine Power Output

94. If this were a coal plant at 95% output – 95% X 1 MW X 24 hours = 22
If this were a coal plant at 95% output – 95% X 1 MW X 24 hours = 22.8 MWH
Hence wind turbine is operating 9.27/22.8 or 40% as same sized coal plant

95. (multiday periods of calm winds)
Why effective output can be as low as 25% of installed capacity
(multiday periods of calm winds)

96. Wind turbines not considered reliable Requires a backup energy source in case wind stops blowing or blows too hard
Reliability can be enhanced by having wind farms in diverse locations where probability of adverse wind conditions at all sites is low
2009 wind energy output: 340 TWh
Power (divide by 24 hours/day and 365 days per year): 38.8 GW
2009 installed wind power capacity: GW
Hence effective utilization: 25% vs 95% for coal and nuclear power

97. The largest land turbine is Vestas 8 mW with blades 80 meters long (rotor diameter of 160 meters)

98. Basic Dimensions of Boeing 747 Wing Span – 195 ft 8 in (59
Basic Dimensions of Boeing 747 Wing Span – 195 ft 8 in (59.6 m) Overall Length – 231 ft 10.2 in (70.6 m)
Can fit comfortably within area swept by 80’ blade

99. And so can Airbus 380!
Max capacity 840 passengers Tip-to-tip wingspan 79.8 meters Length 73 meters

102. Average onshore turbine: $1.8 mm/MW
Wind turbine: 76%
Grid connection: %
Foundation, construction: 7%
Control systems, land, others: 8%

103. Areva 5 MW wind turbine – blade 116 meters
Cut-in wind speed: 4 m/s ( 9 mph)
Rated wind speed: 12 m/s (27 mph)
Cut out wind speed: 25 m/s (56 mph)

104. Hub distance estimated 150 meters or 500’ above ground
Either need helicopter for repairman to land on top
Or climb ladder inside tubular support equivalent to a story building
Maintenance can’t be cheap!

105. New design proposed by Japanese
See Web site: /Japanese-Breakthrough-in-Wind-Turbine-Design

106. Environmental Objections to Wind Farms
Ruins scenic coastlines and mountain areas by both wind turbines and transmission lines
Swishing noise of blades
Kills migratory birds (actually lowest cause of bird deaths)
Bird kills from hitting automobiles and buildings and being caught by cats far, far higher
Building large wind turbines with slow speed blades
reduces swishing noise and birds have better chance to dodge blades

107. Avoid building wind farms on bird migratory routes and use radar to stop turbines when birds are passing through wind farm

108. Winds at night often better than at day, but do not need electricity
Pumped water storage facilities or other form of electrical storage both to enhance reliability of solar and wind and store night time wind generated electricity for day time use

111. Lithium Ion Battery Bank

112. 8 mW of power capacity that can operate for 4 hours to produce 32 mWh stored in 600,000 lithium-ion battery cells

113. Sodium Sulfide Batteries
Positive electrode (molten sulfur) separated from negative electrode (molten sodium) by a solid ceramic electrolyte through which only positive sodium ions can flow
During discharge sodium and sulphur ions combine to form sodium polysulfides
During the charge cycle sodium polysulfides
converted back into sulphur ions and sodium ions
Sodium ions flow back through the membrane and recharge the battery

114. Various Types of Flow Batteries
The vanadium redox battery (VRB) exploits vanadium ability to exist in solution in four different oxidation states
VRB has just one electroactive element instead of two

115. Flywheel Energy Storage (FEES)
Works by accelerating a rotor (flywheel) to a very high speed and storing energy as rotational energy
Energy added to system by increasing and energy extracted by decreasing flywheel's rotational speed

116. Compressed Air Electricity Storage
Off peak electricity is used to compress air for storage in underground mines or caverns which can then be fed along with natural gas into a gas-turbine power plant
Two to three times as much electricity can be produced for the same
amount of natural gas from energy contained in compressed air

118. Table 9.3 Performance of Storage Technologies
Type
Power
in mW
Discharge
Time
Efficiency
Percent
Lifetime
Years
Storage Cost
$/mW-hour
Pumped storage
250-1,000
10 hrs
70-80
<30
$50-150
CAES
3-10 hrs
45-60 30
About $150
Flywheels
<10
<15 min
>85 20 NA
Supercapacitors 10
<30 sec
About 90
50 k cycles
Vanadium RB
2-8 hrs 75
5-15 $
Lithium ion 5
<4 hrs
8-15 $
Lead battery
3-20
4-8
Sodium sulfur
30-35
4 hrs 80 15

119. End of Chapter 9