Harnessing Wind Power through Kites
Image source:-Skysails Power
Despite the focus on developing solar energy, wind energy in India has seen steady development in the last decade. With 32,279.77 MW of installed wind generation capacity (compared to 12,288.83 MW of solar power), India is one of the leading generators of wind energy worldwide. Yet, due to certain constraints, and more recently the more competitive rates in solar energy, there are concerns that the share of wind energy may decline. No doubt, unlike non-storage solar energy, wind turbines are not affected by night and day. However, generation of electricity depends on both the season and geographical location. Besides, wind farms require massive areas of land. In India, wind turbines produce 70 to 80 per cent of their generation in a span of six months. Moreover, to calculate the annual kilowatt per hour (kWh) produced from a turbine, one has to calculate the estimated number of hours of wind at a certain height as well as its speed. On an average, in India, the plant load factor (PLF) is only around 20 to 30 per cent. Hence, with a 25 per cent PLF, a 1.5 MW turbine would produce around 3,285,000 kWh in a year. Below a wind speed of around 30 mph, however, the amount of energy generated would be quite small.1
The government has announced that its target for wind energy generation by 2022 is 60,000 MW. Harnessing this potential will require huge investments as well as the requisite land. However, this problem may be resolvable through the use of a new technology – scores of kites to generate wind energy. This technology is believed to not only cut the cost of generating wind energy but also enhance the efficiency quotient. Although several companies are working on different models, the basic idea is to locate the kites, which are essentially light and controllable aerodynamic flying devices, in a formation at heights of around 750 metres and more in order to harvest the strong and consistent winds available in that region of the atmosphere (wind velocity at those heights is twice that at the ground level) and thus generate low-cost energy.2
The system is operated in periodic pumping cycles, alternating between reel-out and reel-in of the lines attached to the kite and the drum on the ground. During the traction phase, the kite is flown in a figure-eight-like pattern and pulls on the tether lines, which are used to transmit power from the kite to the ground as the lines unroll from large drums coupled to electric drives used as generators. When the kite reaches the end of the line extension, the electric drives are driven in reverse to pull in the kite. Once the kite is brought down to the lowest height, a new traction phase commences. By depowering the kite during the passive phase, less energy is used to pull in the kite than is extracted from the wind during the traction phase, resulting in net power generation. During reel-out, the kite flies in figure-eight manoeuvers at high speeds of 70 to 90 km/h, creating a high traction force which is converted into electricity by the drum and the connected generator. Once the kite reaches the maximum height, it is de-powered by releasing the steering lines so that the whole wing rotates and aligns with the wind. Using the drum/generator module as a winch, the kite is then pulled back to the initial position to start the next pumping cycle. De-powering reduces the traction force during reel-in by 80 per cent, thereby allowing less energy to be consumed as against the energy generated during the reel-out cycle. A crucial element of the technology is the automatic control and synchronisation of the drum/generator module and the flight dynamics of the kite.3 Once the descent is complete, the kite is allowed to climb once more, where it generates electricity once again. This allows these kites to be more efficient than traditional wind turbines.4
According to some estimates, the cost of generation from these kites could be around 50 to 60 per cent less than from traditional wind farms, both on- and off-shore. Moreover, these kite power systems can be flexible. As modular, small-scale power production plants, they can be applied to single houses, for autonomous electricity production as well as for remote areas and villages not yet connected to the power grid. At the same time, they can also serve as huge power plants generating several megawatts and even gigawatts. For example, an Italian firm, KiteGen, has developed a prototype with a capacity for producing 27 MW of peak power.5
The concept has been in existence for a while, and several private companies are involved in developing this technology, particularly European firms such as Swiss Kite Power, Altaeroes Energies, Ampyx Power, KiteGen, SkySails and Minesto. The UK government has been the first to give the green light to launch the country’s first kite power plant by awarding a contract for that purpose to Kite Power Systems (KPS). Interestingly, the funding for KPS has been jointly provided by Shell and the Department of Energy and Climate Change.6 KPS has successfully tested a 40 KW version, while the testing of a 500 KW version will commence in July/August in Scotland. It is also working on a 3 MW version with the aim of eventually ramping it up to 6 MW.7 The UK hopes to supply power to more than 5000 homes by 2020 through these giant kites.8 If successful, these kite farms could replace offshore wind turbines.
Some of the advantages kite power systems have over conventional turbines include negligible noise emission and bird hits, near invisibility, and ability to withstand storms. Moreover, they do not need huge concrete foundations and tonnes of steel for the tower and the blades. As a result, they do not require scarce metals or rare earth elements like neodymium for the magnet in a wind power plant, thereby making them far more environment-friendly than their conventional counterparts.9 Wind kites also require less power to operate.
Nevertheless, some technical issues will have to be resolved before these kites can replace traditional turbines. A major challenge is lightning, which could damage the small computer placed inside the kite. Furthermore, given the height at which the kites would be flying, the location of these wind farms will have to be carefully planned so as not to interfere with or hamper the flight paths of aeroplanes.
Although India is no longer deemed power-deficient, it is by no means energy secure as millions of people do not have access to grid connections. As connectivity increases, the demand for power will surge. Moreover, initiatives like Make in India, Power for All Campaign for total rural electrification by the end of 2017, and the drive to ramp up the use of electric vehicles in place of fossil fuel-based vehicles, among others, will see a quantum jump in energy consumption. While evolving solar technology can fill some of the gap, the government should also look at other new energy technologies across the energy spectrum to meet its energy generation target. India’s record in wind energy development is good. But the existing technology is fast becoming outdated. Evolving technologies like kite wind should therefore be considered.