Wind energy comes from the sun. Counterintuitive but nonetheless true. The transfer of energy from the sun to the earth is fundamental physics, giving rise to weather in the short term and climate when averaged over decades. The sun’s energy in the form of radiant solar heating increases the temperature of the land surface of the earth by transferring electromagnetic energy to individual molecules, causing them to vibrate. Temperature is the empirical measure of the movement caused by the kinetic energy vibration of molecules. More vibration, higher temperature. Sun radiation similarly warms the ocean but mixing water current mitigates the surface heating effect. The heated land surface warms the air immediately above it. Warmer air is less dense since the mostly nitrogen and oxygen molecules move farther apart due to the movement of vibration. The less dense, warmer air rises to create an area of lower pressure in the heated area relative to surrounding air masses. Similarly, cold air falls to create areas of higher pressure. The energy of the sun generates low and high pressure areas.
Temperature differences give rise to pressure differences. Wind occurs when air from an area of high pressure moves to an area of low pressure. On a global scale, the equatorial tropic regions are heated by the sun’s rays causing the air to rise and move toward the colder north and south poles. The tilt of the earth on its axis of rotation concentrates heating in the area between the Tropic of Cancer marking midsummer noon in northern latitudes and the Tropic of Capricorn where it is then midwinter. The rotation of the earth causes the global wind movement from equator to pole to shift in the direction of rotation. This gives rise to counterclockwise rotation in the northern hemisphere and clockwise rotation down under which is called the Coriolis effect. [1] The relatively simple flow of wind curling away from the tropics is complicated regionally by ocean thermal effects and land height differentials. The resultant winds can range from the doldrums of the Horse Latitudes to the fury of a cyclone. Capturing the sun’s wind energy can be a daunting proposition.
The use of wind by humans extends to the dawn of the historical record. Rock carvings of boats with sails have been found in the Nile Vallery at a site named Wadi Hammamat dating from about 3300 BCE, the pre-dynastic period before the union of Upper (southern) and Lower (northern) Egypt. Corroborating evidence in the form of Egyptian vases depicts reed-hulled ships with a single mast holding a square sail probably made from either papyrus or cotton which were likely limited to excursions along and across the Nile. The Phoenicians, the sea-faring people of antiquity, ranged throughout the Mediterranean region and possibly passed through the Strait of Gibraltar to reach the British Isles. A rough hewn terra cotta ship model from about 1500 BCE found near Byblos on the Lebanese coast provides archaeological evidence. Supplemented with oar-wielding human crews, the sail-powered galleys of the Greeks vanquished the Persian fleet at Salamis in 480 BCE and the long boats of the Vikings began their centuries long raids along the coastlines of Europe at Lindisfarne in Northumbria in 793 CE. [2] The sailing ship bereft of oars became the agent of change during the Age of Discovery that began with Columbus and literally established a New World order.
Wind power was the driving force for merchant ships seeking global trade in spices and silks and for warships seeking global dominance with cannons for centuries. The language and units of wind are thus rooted in nautical applications. The knot or nautical mile per hour for wind speed is a good example. Ships navigate without landmarks in the open ocean, their horizons uniform in all directions. Starting from home port as a known datum, ships proceeded by dead reckoning, a means of determining current position by using only course and speed. The magnetic compass provided a reasonably reliable course but the speed was as variable as the wind. The mile predates the kilometer by centuries, having been introduced by the Romans as the distance travelled by its legions in 1,000 double steps (mille in Latin) or about 5,000 feet, which was standardized by Queen Elizabeth I to 5,280 feet, exactly eight furlongs. The nautical mile has a different provenance as one sixtieth of one degree of arc of earth’s circumference at the equator which works our to 6,080 feet. Since degrees of latitude and longitude along the surface of the earth define geographical position, the nautical mile providing increments of degree change is the best measure. An ingenious method was devised to determine ship speed in nautical miles per hour. A weighted sea anchor called a drogue attached to a rope was dropped over the gunwale (ship’s sides above the deck used for gun support). The rope had knots every 47 feet 3 inches which were counted as they played out for a period of 28 seconds (measured by sand glass) as the ship moved away from the stationary drogue. Every knot counted meant that 47.25 feet had been traveled in 28 seconds, which equates to nautical miles per hour. Since ship’s speed was knots, the wind that created it was given the same units. [3]
The age of sailing ships ended with the advent of steam boats powered mostly by coal, the first of fossil fuels. Before Thomas Newcomen invented the steam engine later improved by James Watt as a practical alternative power source, the only way to do work was with humans or animals, and, much later, flowing water or blowing wind. Manpower, now implausibly mangled as person-power, was paramount, and aggressive dynasties throughout the Old World cast about for humans as slaves to carry out the chores of manufacture. The word slave derives from the capture of Slavs from the southern steppes of Europe by the Tatars, who raided up and down the Dnieper and Don River basins to satisfy the demands of their Ottoman employers whose religion forbade the enslavement of Muslims. The Cossacks originated as a roving band of nomads that fought against the Tatarian slave trade. [4] The heavy stones of the pyramids of Egypt and Mesoamerica were cut, hauled, and hoisted by humans. The Africans kidnapped from their homeland and sold to colonists of the New World perpetuated forced slave labor into the nineteenth century. Animal power came later.
Dogs were first domesticated from wolves about 10,000 years ago primarily as human hunting companions. Sheep, goats, and pigs followed over the next two thousand years as ready sources of animal protein to augment and eventually replace unreliable hunting for elusive prey. But it was the domestication of the cow/ox from the aurochs 6,000 years ago and the horse two millennia later that transformed human endeavor by incorporating beasts of burden. It has been argued that the prevalence of large domesticable herbivorous mammals in Eurasia (13 out of a total of 14 with only the llama as an American outlier) led to the historical dominance of this area in world history. [5] Workhorse became an idiom for any durable and dependable device as testimony to the centrality of equine employment for everything from chariots to plows. Watt invented the term horsepower to provide understandable equality to his steam engines to convince skeptical buyers of their efficacy. Both units of power are now in use, one mostly for cars and the other for lightbulbs (1 horsepower = 745.7 watts) … and wind turbines.
The first wind machine was the windmill. Now a synonym for rotating, the term windmill originated as a compound word to describe the process of using wind to mill grain. As agriculture supplanted foraging in the Neolithic (New Stone) Age, populations grew as more food became available on a regular, seasonal basis. The need to supply more grain to meet burgeoning demand drove innovation. The small, hand operated grindstone that sufficed for the individual hearth grew in size and weight to the millstone of mass production. The role of grain mill operator, or millwright, evolved as innovators employed first human and eventually animal strength to operate centralized flour processing facilities. Windmills first appear in the historical record in 644 CE operating in the region now called Sistan or Sakastan in eastern Iran near the Afghanistan border noted for persistent strong winds and lack of flowing water. The Asbads (Persian for windmill) of Sistan, now a UNESCO World Heritage Site, consisted of a vertical axis directly connected to a pair of millstones at the bottom with wind-catching sails mounted horizontally in a stone structure configured with entrance and exit wind portals. [6] The use of vertical axis mills persisted into the 13th century and spread eastward to China and westward to the Crimean Peninsula that extends into the Black Sea.
The first European windmills repurposed the Persian asbad with the use of the gearing that had been developed independently for the waterwheels of the Roman Empire. The result was the iconic post mill with two to four elongated sails made from canvas ship sailcloth stretched over a wooden frame and held vertically in the direct path of wind by a wooden post. The wind-rotated sails turned a horizonal axle which was connected to the grinding millstones with a 90-degree bevel gear. Post-type windmills first appeared in France in 1180 and were introduced to England a decade later, evolving over the next century to a tower windmill that included a movable roof that could be turned on a track to adjust to changes in wind direction. The windmill as water pump was developed in the Netherlands in the 15th century to drain low lying areas for plantation. With the mill stone replaced by a bucket wheel, water was elevated by over six feet and deposited in purpose built drainage ditches. The windmill gained symbolic distinction as the epitome of Holland, complementing the tulips that were planted in the now arable land and the wooden sabots worn by peasants to traverse boggy fields. By the 19th century, the windmill as generic power source contradicted its grain grinding etymology. In addition to water pumping, windmills were used to saw wood, polish stone, grind paint, press seed oil, make paper, and a variety of other mechanized processes including the traditional grain milling. The Zaan region just north of Amsterdam had more than 900 windmills in the 19th century. [7]
The first wind machine exclusively for power generation was constructed in Cleveland, Ohio by the electrical pioneer Charles F. Brush. After designing and patenting a dynamo for generating electricity for arc lights in 1876, he formed the Brush Electrical Company which sold arc lighting systems across the United States from San Francisco to New York, providing the first lights on Broadway. After selling his company to what was to become General Electric he retired to his mansion on Euclid Avenue in Cleveland, devoting himself to research and invention. In 1888, he designed and built a massive wind turbine with a 56 foot diameter rotor with 144 cedar blades to provide power to charge 12 direct current (DC) batteries to power 350 light bulbs in the mansion. An 1890 article noted that “The reader should not think that electric light from energy obtained in this way is cheap because the wind is free … However, there is great satisfaction in making use of one of nature’s most unruly forces of motion.” [8] Perhaps that was Brush’s motivation. At about the same time, the Danish inventor and physicist Poul la Coul took a different tack, using a small number of rapidly turning blades to generate electricity at the Askov Folk High School, where he taught classes on wind electricity and founded the Society of Wind Electricians. His rather surprising choice for energy storage was hydrogen produced by the electrolysis of water which was used directly for gas lights in the school. Explosions caused by oxygen contamination blew out the windows on several occasions. In 1957, Johannes Juul, one of la Coul’s students, pioneered the first wind turbines to generate alternating current (AC) electricity using the now standard three blade wind turbine. [9]
The latter half of the 20th century was dominated by cheap fossil fuels for conventional power plants and, for a time, the promise of nuclear energy. The Arab oil embargo imposed in reaction to the 1973 Yom Kippur War sent shock waves throughout the industrialized world, eliciting a reassessment of dependence on foreign oil. The resultant impetus for alternative power generation sources led to a renaissance in wind energy research and development. The wind-wise and wind-resourced Danes took matters into their own hands. In 1975, A group of teachers from three schools that shared a large campus on the former Tvind farm in Western Denmark near Ulfborg placed an ad in a major paper “seeking windmill builders.” The resultant Windmill Team, comprised of an eclectic group of 400 idealists with no prior experience and an average age of twenty-one, set out to build the world’s first megawatt (MW) wind turbine from scratch with funding provided by the teachers. Three years later, the Tvindkraft, with three pitched rotating blades made from fiberglass and a computer-controlled frequency converter to account for variable speed, rose above the Jutland plain. At a height of over 150 feet and a power capacity of 2 MW, the first modern wind turbine was the largest in the world for several decades. It is still in operation, providing electrical power to the three schools and the co-located Tvind Climate Center. Denmark subsequently became the world leader in wind energy, as copies of the design were built throughout the country. The Windmill Team sought no patents in order to promote the shift to wind power and away from fossil fuels, an act of notable altruism. [10]
In the United States, federal level wind turbine research and development sparked by the oil embargo followed the more traditional pathway of public funding to private companies. The Department of Energy (DOE) established the NASA Lewis Research Center in 1973 to oversee demonstration projects selected from proposals submitted. The NASA/DOE MOD-0 was a Lockheed design erected in 1975 in Ohio with two blades producing 100KW atop a 100-foot tower. Designs progressed over the years to MOD-5B, a Boeing installation on the Hawaiian island of Oahu in 1987 producing 3.2 MW on a 200-foot tower. None of these designs were ever commercialized and the prototypes were all eventually shut down and dismantled. [11] At the state level, rising oil prices coupled with nascent environmental concerns provoked the California Energy Commission to establish the Altamont Pass Wind Resource area in 1980. With favorable tax incentives, conditional use permits were awarded to commercial interests to build wind farms in Alameda and Contra Costa counties just east of San Francisco. This resulted in the world’s first modern large scale wind farm. With an average wind turbine power of only 94 KW, these relatively small turbines were combined in groups of up to 400 to generate city size megawatts of power.[12] Although interest waned when oil prices dropped in the mid 1980s, the Altamont Pass project was never abandoned and served as the nexus for increasing California wind energy capacity to address the rising temperatures of global warming.
The United Nations established the Intergovernmental Panel on Climate Change (IPCC) in 1988 to provide “an assessment of the understanding of all aspects of climate change, including how human activities can cause such changes and can be impacted by them.” The panel consists of an international team of recognized experts in the interrelated scientific fields that play a role in climatology. The First Assessment Report was issued in 1990 after having reviewed the preceding decades of research with two broad findings: (1) The greenhouse effect is a natural feature of the planet and its fundamental physics is well understood; and (2) The atmospheric abundances of greenhouse gases were increasing largely due to human activities. [13] After almost three centuries, the cost of the fossil-fueled Industrial Revolution had become clear. The environmental free lunch was over. By the turn of the century, wind energy was back on the table and resources poured into the design and construction of ever larger and more efficient turbines to be placed in dense clusters wherever the winds blew best. And because of wind variability, its use as a controllable force for reliable and consistent electricity posed an engineering challenge.
That wind force can pack a punch is evident in coastal communities hammered by hurricanes and in trailer parks torn apart by tornadoes. Wind derives power from the force it exerts on any surface that is in the path of its movement to equalize pressure. The basic wind power (P) equation is fairly simple:
P = ½ρAv3
where ρ is air density, A is turbine area, and v is wind speed. Since the density of air is relatively uniform at 1.25 kg/m3, the only way to increase the power of a wind turbine is to make it bigger or to locate it in a windy area. Wind speed is the most important factor due to the cubic function, which means that if you double the wind speed, power goes up by a factor of eight (2x2x2=8). Area is the circle swept by the rotating blades that define its radius r, the familiar A = πr2. It is convenient to use metric units to produce power in watts. For example, a wind turbine with 10 meter blades (an area of 320 square meters) rotating in wind at 10 meters per second (1000 when cubed) would result in a theoretical maximum power (0.5)(1.25)(320)(1000) = 200,000 watts or 200 kilowatts (KW). Note that 1 meter per second is about 2 knots, the nautical wind speed unit. A kilowatt is approximately the amount of power required for a mid-sized single-family home. The megawatt (MW) is more useful for the energy needs of a city. Terawatt is global.
In the real world, there are both physical and practical limits on the calculated power of a wind turbine that together reduce the usable power by about half. The physical limitation is based on the fact that if all of the wind passing through a turbine generated power, then the wind would have no more energy. In other words, the wind would stop blowing. Since the wind does not stop, it stands to reason that only a portion of its energy can be extracted. The limit imposed by the physics of fluid flow is known as the Betz Limit for the German physicist Albert Betz who first proposed it. The Betz Limit is 59 percent. Therefore, the maximum power that could be generated from the 200 KW wind turbine would be 120 KW. This maximum would only be achieved when the wind maintained an average speed of 20 knots or 10 miles per second and if the blades were effective over the entire area A. That this is not the case is reflected in the use of Cp, the power coefficient or the performance coefficient. Cp varies according to the pitch angle of the blades, which are adjustable on all modern wind turbines, and on the rotational speed at the tip of the blades relative to the upstream wind speed, which varies according to blade length. A maximum Cp of 45 percent is the result of a tip speed that is 7 times faster than wind speed with a 0 degree pitch angle. [14]. Finally, it is necessary to account for wind variability over time in a given geographic area. The term capacity factor (CF) is used to adjust the wind energy that can be extracted relative to the nameplate or nominal KW or MW capability of the wind turbine. An economically viable wind turbine requires a CF of about 30 with a maximum in near perfect conditions approaching 45. [15] The bottom line is that it takes a lot of wind turbines to capture enough wind energy to power a city. Hence the wind farm.
Wind installations are divided into two broad categories according to placement: onshore and offshore. Onshore wind turbines are cheaper to build and maintain, but are limited by the lower average wind speeds over land and by human nuisance factors like noise and landscape aesthetics. Offshore wind turbines take advantage of the more consistent winds over water but can only be sited in countries with suitable littoral areas with adequate capital to finance the higher construction costs. Because many of the industrialized nations of the world abut the oceans and have limited land area available, offshore wind is sometimes the better option. Growth statistics since 2005 have been impressive. According to the Global Wind Energy Council, offshore wind grew by 21 percent annually over the last ten years, bringing the total installed offshore wind power to 64.3 GW. While the United States has only 42 MW of offshore wind installed, the Inflation Reduction Act incentivized offshore wind installations with about 50 GW of added capacity now in early planning phases. However, onshore wind is still by far the most prevalent, comprising over 90 percent of global installed wind power. [16]
Onshore wind towers followed the historical pattern of windmills of past centuries that were installed locally where needed and feasible. The benefits that accrued to populations in areas hosting them offset most pushback complaints about land use and landscape clutter. In Holland they are and were the hallmark of Dutch industry. The only technical constraint for onshore wind is adequate wind. In general, this restricts installations to rows along mountain ridges and in phalanxes on windswept plains arranged to prevent wake interference. Financial constraints depend on the cost of electricity offsetting capital intensive construction. Political constraints are largely dependent on the local perception of climate change and on financial incentives for community services and local landowners. Onshore wind partnered with solar photovoltaics comprise the lion’s share of renewable energy that has burgeoned over the last decade. 440 GW of renewable energy, enough electricity for Germany and Spain, was added in 2023, 107 GW more than that added in any previous year. The total amount of renewable power globally by the end of 2024 is expected to reach 4,500 GW (4.5 TW), the amount of electricity consumed annually by the United States and China. [17] These rosy projections are certainly good news as testimony to the oft-stated goal of carbon neutrality by mid-century. However, it is not likely that continued growth at this pace will be sustainable.
World population has increased exponentially for centuries. Exponential means that it follows the progression 1-2-4-8-16 ad infinitum, doubling every generation if the exponent is two. The supporting world market economy has expanded in proportion to the number of people it serves as substantiated by annual percentage increases in GNP. However, all growth is limited by inherent constraints. Globally, the earth and its resources are finite and there will eventually be a population maximum (estimated at 10 billion in 2050). Technologies like wind energy are also constrained by both physical and geographic limits. Wind turbine power went from a few kilowatts in the 19th century to 100 KW one hundred years later. The climate change impetus to improve wind turbine performance resulted in taller towers, longer blades, better generators, and lighter materials produced a tenfold increase to the megawatt range by the end of the 20th century. The largest wind turbines now being built are in the 5MW range. There will be no gigawatt wind turbines. The reason is that there are constraints on the maximum power that wind turbines can produce due to height, weight, and the physics of both wind and electricity. The resultant S-shaped curve accounts for these systematic shortfalls over time. It is a calculated or logistic result unlike the mathematical exponential It called logistic growth. [18]
Growth can be exponential only in the beginning when “low hanging fruit” is harvested. This hackneyed engineering axiom refers to things that are easy to change since they are within arms reach (low off the ground) and are fully developed (ripe fruit). An example would be changing from steel to aluminum to reduce weight to build a taller tower. Improvements become harder over time until the carrying capacity is reached. This phenomenon is called “decreasing returns to scale,” characterized by an inflection or turning point where exponential growth transforms to an asymptotic approach the maximum sustainable size (or power). Though the terms are not synonymous, the logistic S shape is the result of logistics. Logistics is defined as managing the details of an undertaking. The aphorism “an army marches on its stomach” refers to the need to have food supplied to it by a logistics chain that is frequently called the supply line. An unfed army cannot continue to march. This phrase is attributed to Napoleon, who ironically lost most of his Grande Armée on the plains of Russia due to not following his own logistical dictum. The design, manufacture and deployment of complex technologies like wind turbines requires a steady logistical stream of materials to build them and industrial engineers to install them. From the megawatt powering standpoint, it may be concluded that wind turbines are at or near their logistical megawatt limit due to logistics factors.
Wind turbines are equally, and perhaps more dramatically, limited by geographic and social constraints. Sites with the highest average winds and most favorable demographics were filled with the initial round of wind towers now in operation and generating “current” electrical statistics. The original investors were rewarded with sustainable profit margins necessary for a market economy. Expansion to less desirable sites with less wind will change the equation. At some point, revenue from the sale of electricity is no longer sufficient to finance the capital investment needed to build the wind turbine in the first place. At the same time, higher wind turbine manufacture and installation costs accrue due to the increase in demand for critical materials with a limited supply. Supply/demand mismatch is a harbinger of inflation, the gradual rise of all costs. Financial strain is starting to occur in 2023. Orsted, the largest energy company in Denmark and world leader in wind energy, cancelled two major wind projects off the coast of New Jersey called Ocean Wind that would have produced 2.2 GW. According to one of the Orsted executives “macroeconomic factors have changed dramatically over a short period of time, with high inflation, rising interest rates, and supply chain bottlenecks impacting our long term capital investments.” This decision was further justified based on local opposition. Residents of New Jersy’s coastal Cape May filed a lawsuit to block a tax break for the wind farm claiming that “offshore wind development could threaten fisheries and marine mammals.” [19] With short sightedness approaching myopia, the shoreline loss that the rising sea levels of global warming will ultimately induce, no doubt to the benefit of both fish and whales and the detriment of future generations, was not mentioned.
Onshore wind projects have technical and social challenges that are in many cases even more trenchant than the nearly out of sight offshore projects. Land-based wind machines straddle ridgelines and dot wind swept plains in remote places―far from the industries and populations they serve. Transmission and connectivity is a serious problem in continent-sized countries like the United States and Australia. A good example is the plight of the Southwest Power Pool (SPP) that manages the electricity grid across the Great Plains from the Dakotas to the Rio Grande through over 60,000 miles of transmission lines. New wind and solar generation sites seeking to hook up to the grid must wait in what is called the “interconnection queue” until a computer simulation can be run to ensure that the grid remains stable and effective. A wind energy firm in Virginia named Apex drew up plans to install 135 wind turbines in New Mexico generating 300 MW of power in 2013 and applied for connection to SPP in 2017. By the time SPP got around to running the simulation in 2022, there were dozens of projects totaling over 10 GW. The model showed that a new 100 mile long high voltage power transmission line would be necessary to accommodate the disruption at a cost of over $1B that would need to be paid by the projects seeking grid admission. With a bill of over $250M, the Apex project was no longer financially viable and was cancelled. The Federal Energy Regulatory Commission (FERC) that requires the simulation testing is working to ameliorate the situation, but the inherent variability of wind and solar power on an otherwise continuous and necessarily stable power grid must be taken into account lest blackouts prevail. [20]
The 26th United Nations Conference of Parties or COP26 held in London in November of 2021 established a global benchmark of reducing net carbon emissions by 50 percent in 2030. The lion’s share of the emissions (69%-89% depending on the model) are from power generation and transportation. In order to meet the 2030 COP goals, the power sector will need to reduce carbon dioxide emissions by over 50%. Meeting this threshold will require the elimination of all coal power plants and the increase in solar and wind power by about five times the growth levels of the last decade―nothing less than exponential will do. Similarly, the transportation sector will require an increase in electrical vehicles (EVs) from 4% in 2021 to an average of 67% in 2030, placing even more strain on the grid. A continuation of current US public policy will produce only 6% to 28% of net carbon emission reduction by 2030. [21] It is not unreasonable to suggest that the goal cannot be reached using only wind and solar power which must be used when generated or stored in nonexistent long term energy storage repositories (like batteries). A stable source of electricity is needed to sustain the grid. Fusion will never be ready in time. “Politicians need to tell voters that their desires for an energy transition that eschews both fossil fuels and nuclear power is a dangerous illusion.” [22] The fate of Earth as human habitat is at stake.
References:
1. Fovell, R. Professor of Atmospheric Science, UCLA, Meteorology: An Introduction to the Wonders of the Weather. The Teaching Company, 2010.
2. Capper, D. Commander, Royal Navy “Sails and Sailing Ships” Encyclopedia Brittanica Macropedia, William Benton, Chicago. 1972, Volume 16, pp 157-163
3. Whitelaw, I, A Measure of All Things, St. Martin’s Press, New York, 2007, pp 30, 101.
4. Plokhy, S. The Gates of Europe, A History of Ukraine, Revised Edition, Basic Books, New York, 2021, pp 74-76.
5. Diamond, J. Guns, Germs, and Steel, W. W. Norton and Company, New York, 1997, pp 157-175, 355.
6. https://whc.unesco.org/en/tentativelists/6192
7. Wailes, R, “Windmills” Encyclopedia Brittanica Macropedia, William Benton, Chicago. 1972, Volume 19, pp 861-862.
8. “Mr. Brush’s Windmill Dynamo”, Scientific American, New York Volume 63 Number 26, December 20, 1890.
9. The History of Modern Wind Power (Danish with English translation) http://xn--drmstrre-64ad.dk/wp-content/wind/miller/windpower%20web/da/pictures/index.htm
10. https://www.tvindkraft.dk/stories/wind-and-the-environmental-crisis-windmill-denmark/#
11. https://www.windsofchange.dk/WOC-usastat.php
14. Aliprantis, D. Fundamentals of Wind Energy Conversion for Electrical Engineers, Purdue University School of Electrical and Computer Engineering, 2014 https://engineering.purdue.edu/~dionysis/EE452/Lab9/Wind_Energy_Conversion.pdf
15. Kalmikov, A. Wind Power Fundamentals, Department of Earth, Planetary, and Atmospheric Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts, 2013. http://web.mit.edu/wepa/WindPowerFundamentals.A.Kalmikov.2017.pdf
16. Global Wind Energy Council, Global Offshore Wind Report 2023 https://gwec.net/global-wind-report-2022/
17. International Energy Agency (IEA) Renewable Energy Market Update Outlook for 2023 and 2014. https://www.iea.org/energy-system/renewables/wind
18. Smil, V. Growth, The MIT Press, Cambridge, Massachusetts, 2019, pp 20-21, 181-184.
19. Puko, T. “Demise of N.J. wind projects imperils Biden’s offshore agenda” The Washington Post, 2 November 2023.
20. Charles, D. “Off the Grid” Science, Volume 32, Issue 6662, 8 September 2023 pp 1042-1045
21. Bistline, J. et al “Actions for reducing US emissions at least 50% by 2030” Science, Volume 376, Issue 6596, 27 May 2022, pp 922
22. “Power Struggle” The Economist Jume 25-July 1, 2022. P 11.
Hiker's Notebook 