Wind Energy Patents

Dr. Rajendra Prasad
25 April 2012

Introduction

Wind energy technology is going through a remarkable phase of development now for past few years. It has been predicted that it would become in more common use than ever before and compete with other sources of conventional energy. Consequently, there is much wind blowing through the patent scenario as well; no other field of renewable energy other than solar (thermal and photovoltaic) is receiving as much attention as the 'wind energy'.

Past some years have not only witnessed rising patent registration in the field of 'wind energy' across various jurisdictions but have also witnessed increased patent infringement law suits that are being hotly debated in patent law circles. Last month, a Texas Jury, rejecting several of Mitsubishi invalidity grounds, found that it did infringe the GE's US Patent No. 7, 629, 705 ('705 Patent) and reversed the earlier decision of the Texas federal court. It also awarded GE about $170 million in damages.

Right here in India, not too far ago, as many as dozen patents of Enercon out of about 2 dozen challenged patents, many of which are in the name of its founder Dr Aloys Wobben have been revoked when opposed by its partner in the Indian joint venture. It is worth noting that Dr Wobben launched an aggressive world-wide patent drive since 2001; in US alone he is stated to have a total of 157 patents, 114 in the EPO and 118 in India. The patent law suits of Enercon/Dr Wobben have been chronicled in a series of posts in the 'SpicyIP' blog.

Nonetheless, with growing awareness of the possible consequences of greenhouse gas emissions, there has been a significant surge in research and development and thus also of patenting in the related fields, especially since the Kyoto Protocol was signed in 1997. Wind energy technology forms an important component of research and development directed to mitigation of greenhouse gas emissions' consequences. This article is aimed at explaining technical aspects of this technology and the mechanisms to searching related patents for reference and study.

Wind and wind turbine

A blowing air usually parallel to the earth's surface is known as 'wind'. This is, in fact, a different form of solar energy; uneven heating up of the earth's surface coupled with uneven terrain cause variety of wind patterns manifesting into breeze, cyclone, whirlwind etc. Any wind that moves has kinetic energy embedded in it that can be captured and harnessed by 'wind turbine' and converted to other forms of energy such as electricity or mechanical power.

A wind turbine is essentially a device to convert the kinetic energy of the wind into mechanical energy that can be used to drive machinery for grinding materials or food grain or for pumping water (i.e., wind mill) or for producing electricity (i.e., wind generator). For millennium, wind mills have been used in large farms in many countries but the recent surge and focus on research and development in 'wind turbines' is largely for producing electricity, preferably that can be fed into an existing grid carrying electricity often produced from other sources of energy, such as fossil fuel. This is in a bid to optimise 'green power' generation and cut down on conventional sources of energy. This unprecedented thrust on green power from wind is also due to favourable policy instruments and promotional measures that the Governments in various countries have promulgated where a large potential of wind energy has been estimated.

Wind energy scenario: national and international

According to World Wind Energy Report 2012:

All wind turbines installed by the end of 2010 worldwide can generate 430 Terawatthours per annum, more than the total electricity demand of the United Kingdom, the sixth largest economy of the world, and equalling 2,5 % of the global electricity consumption.

The wind sector in 2010 had a turnover of 40 billion Euro and employed 670'000 persons worldwide.

China became number one in total installed capacity and the center of the international wind industry, and added 18 928 Megawatt within one year, accounting for more than 50 % of the world market for new wind turbines.

According to World Wind Energy Report 2010, the top ten wind power countries in order of installed wind power capacity by the end of 2011 are as follows:

Country	Installed Wind Power Capacity (MW) as on Dec. 2011
China	62,733
United States	46,919
Germany	29,060
Spain	21674
India	16084
France	6800
Italy	6747
United Kingdom	6540
Canada	5265
Portugal	4083
Rest of world	32444
Total	238351

China and Spain in the above list are stated to have achieved remarkable progress in enhancing their installed capacities during last couple of years.

According to the Ministry of New and Renewable Energy (MNRE) in India, the share of renewable based capacity is 10.9% (excluding large hydro) of the total installed capacity of 170 GW in the country, up from 2% at the start of the 10th plan period (2002-2007). This includes 13,065.78 MW of wind, 2,939 MW of small hydro power, 1,562 MW of (bagasse based) cogeneration, 997 MW of biomass, 73.46 MW of 'waste to power' and 17.80 MW of solar PV for grid connected renewable at the end of 2010. Wind energy is stated to get further boost in coming years.

Wind turbine basics & types

A number of factors come into play in deciding the most appropriate wind turbine design for a specific location which are determined by aerodynamic modeling taking into account the wind speeds, variability and directions. Such analyses help to determine the optimum tower height, control systems, number of blades and blade shape.

There are two main types of wind turbines: i) horizontal axis wind turbines (HAWT) which are more conventional and are used in large wind farms, ii) vertical axis wind turbine (VAWT). VAWT is relatively less energy efficient as compared to HAWT but also costs less in installation, operation and maintenance. It is lot quieter and affords the generator, gearbox and other components to be placed on the ground, so the tower doesn't need to support it, and it is more accessible for maintenance.

Wind turbine of any type can be divided into three components in its assembly:

Rotor including the blades which cover approximately 20% of the total cost of wind turbine.
Generator including control electronics and a gearbox covering a cost of approximately 35% of the cost of the wind turbine.
Structural support including tower and rotor yaw mechanism costing approximately 15% of the total cost of wind turbine.

It has been shown that the wind power is proportional to the third power of the speed of the wind, i.e., P ∝ v³, where P is 'wind power' and v is 'wind speed'. In other words, at double the speed of wind, the potential wind power is nearly eight times. It is imperative, therefore, that the wind turbines should really be efficient at higher wind speeds, especially where the units are aimed at connecting to the electricity grid. It has also been shown that power available increases by a factor of 4 when the diameter of the blades doubles. Thus it obviously is advantageous to have wind turbines with larger rotor blades and placed in areas with high wind speeds. There is, however, an upper limit that all the available wind power can be extracted even with best of engineering designs. Way back in 1919, a scientist known as Betz had shown through empirical calculations that no more than 59.26% of all wind power can be extracted; this is now known as 'Betz limit' beyond which no wind power can be practically obtained even with most efficient wind turbines.

Turbine size and output

Wind turbines for commercial electricity generation usually range from 100 kilowatts to 5 megawatts. A typical wind turbine of 1.5 MW seen on some commercial wind farms has a tower 80 m high with a base of 15 m diameter which can weigh as much as 25t or more. The rotor assembly with blades and hub can weigh more than 20 t whereas the nacelle, which contains the generator component, could weigh more than 50 t. Some of the larger wind turbines tend to have rotor diameter exceeding 120 m. Some of the wind turbines now available for home use have rotors between 8 and 25 feet in diameter and generate between a few hundred watts and 6 kilowatts of electricity.

Wind energy and climate change(CPC)

Wind power is generally regarded as green power since it has the potential to mitigate the greenhouse gas emissions. It is of interest to know this relationship. For every kilowatt hour of electricity generated by wind energy, approximately 1.5 pounds of carbon is prevented from going into the atmosphere if that electricity had been sourced from coal fired power plants. Carbon dioxide is a major contributor to global warming induced climate change.

It has been estimated that the current wind technology already has a very favourable carbon foot print according to which the carbon dioxide emissions released to the atmosphere during the manufacture of wind turbines, their installation and servicing over the average 20 year lifecycle are generally 'paid back' after the first three to nine months of operation; beyond this, wind power produces no carbon dioxide emissions.

Searching wind energy patents(CPC)

Since climate change mitigation technologies including wind energy technologies like other newly emerging technologies develop very quickly and can be found in many areas of technology in the classification of patent literature, all important patent offices are seized with the problems associated with their coding and de-coding. European Patent Office in association with UNEP and ICTSD, an international NGO has evolved a new tagging scheme whereby all 'climate change' related technologies are assigned easily identifiable classes that provide easy access to the general public to climate change mitigation technologies through their espacenet database.

The new classification scheme bearing the code 'Y02E' distinguishes all known 'renewable energy' sources as follows:

Code Y02E	Description
10/10	Geothermal energy
10/20	Hydro energy
10/30	Energy from sea (tidal stream Y02E10/28
10/40	Solar thermal energy
10/50	Solar photovoltaic (PV) energy
10/60	Thermal PV hybrids
10/70	Wind energy

Moving on to a next level of classification in Y02E 10/70, further sub-areas are identifiable as follows:

Y02E 10/72	Wind turbines with rotation axis in wind direction
Y02E 10/72B	Blades or rotors
Y02E 10/72D	Components or gearbox
Y02E 10/72F	Control of turbines
Y02E 10/72H	Generator or configuration
Y02E 10/72J	Nacelles
Y02E 10/72L	Offshore towers
Y02E 10/72N	Onshore towers
Y02E 10/74	turbines with rotation axis perpendicular to the wind direction
Y02E 10/76	Power conversion electric or electronic aspects
Y02E 10/76B	For grid-connected applications
Y02E 10/76D	Concerning power management inside the plant, (e.g. battery charging/discharging, economical operation, hybridization with other energy sources)

Please note that all the above wind energy codes for specific group of patents are provided here with active hyperlink. Thus, clicking on these one can reach directly those bunch of patents at European patent database 'espacenet'.

Conclusion

Wind energy technology is developing at a breathtaking speed with landscape in many countries changing dramatically with mushrooming wind farms. It is of interest to keep an eye on the newer developments on various aspects of wind energy technology. The new classification scheme of European Patent Office with 'Y02E' tags provide an invaluable handle to peep into this new exciting world of wind energy patents.