– By the Electrical India content team
India presently has an installed wind energy capacity of approximately 37 GW. Also, it has a target of reaching 60 GW by the year 2022; and an ambitious goal of 450 GW by the year 2030. In terms of potential, it is 695 GW at a hub-height of 120 meters. To date, only on-shore wind potential is being tapped into, but industry representatives’ assert that the market is huge. Ajay Devaraj, Secretary-General, Indian Wind Power Association, while highlighting the stressors and inconsistencies in the regulatory framework, says: “The availability of infrastructure to evacuate the power generated and the tariffs must all be factored in.” India, he says, is looking at comprehensive amendments to the Electricity Act, 2003 – setting up green-corridors and making huge investments in the power sector. “The renewable market is certainly open to turbines and has always been so.
However, turbine manufacturers would also need to step in to understand the changed scenario, that machines are capable of operating at heights up to 120 meters, competitively priced and comprehensive O&M, availability of spares throughout the entire useful life of the machine, etc.”
Siddharth Singh, Data Analyst & Machine Learning Engineer, IBM, speaks about the market for wind energy in India while also pointing at the competition in the market. He says: “Many companies in Europe, Northern America and China have generated significant value in its intellectual property (IP) related to the Kite Generator System (KGS) in the form of patents, prototypes, design reports, simulations, technical results, market reports and more.” These IPs, he adds, were acquired from various research institutes initially, and have been enhanced to achieve its final form as a product. “To be honest, I believe, only the biggest private players in India can afford the cost of borrowing the technology. Further, there is an urgent requirement in the country to improve its infrastructure and education system. This will accelerate research and innovation as well as it will provide the Indian market with competent manpower,” he adds. Speaking of the emerging trends concerning the KGS system, Singh says: “The advancement in technology has led to the decrease in the cost and the size of communication devices. Today, the equipment can be mounted on power kites and they can be used as boosters, repeaters and antennas. Hence this will improve the accessibility to various communication networks in the remote areas.”
Get acquainted with the KGS system
In the May 2020 issue of the Electrical India magazine, Singh stated that KGS is the future of the renewable energy market. There is already a heavy demand as well as a tough competition in the international market for KGS technology. While further explaining the basic elements of the KGS system, he says: “On the top is the kite in the shape of a parachute. The natural path followed by this kite is upward with the wind in an eight-shaped orbit. The tether is a cheap rope made of fibre having good mechanical strength. The one end of the tether is connected to the kite and the other end is wounded on a drum. The drum rotates to unroll the tether and the kite goes upwards. An electromechanical energy conversion (EMEC) device is connected on the same shaft as the drum through a gearbox. Hence, the linear kinetic motion of the kite is converted in rotational motion of the drum and is used to generate electricity using an EMEC device.” Also, he says that the KGS is a Relaxation Cycle System; it is composed of a traction phase. In the traction phase, the kite goes up following an eight shaped orbit, hence drum unrolls and the EMEC device acts as Generator. “In the recovery phase, the electrical energy is consumed to bring the kite back down, the EMEC device acts as a motor to deliver the power to the shaft and the drum rolls back the tether,” he adds.
The need to operate the Kite in a specific range of height (generally 350 to 500m) is explained in fig. 3. The figure shows the different kite power region which is in the shape of a quarter sphere, considering the direction of wind going into the page. There is a lower limit under which the kite is having the risk of falling. Little above comes the maximum power region where we get a peak in power curve then comes the medium power region where power output is almost constant with increase in height. The efficiency above a certain height is low. Hence as soon as kite reaches minimum power region, a relaxation cycle is initiated to bring the kite back in the maximum power region of operation.
Can the KGS system be enhanced and modified via IoT?
Singh asserts that there is no doubt that IoT can be used to implement the control scheme. He says: “Various sensors will be required to identify the trajectory, orientation and curvature of the kite. Wireless communication is required to transmit the signals received from these sensors to the controller module.” He adds and says that the data collected at higher altitudes can be sent to data centres for research and analysis, to predict the weather and generation and to predict time-varying price of the wind power by various electricity aggregators. He says that companies such as Makani Power, Kitepower, Kitegen, Kitemill, Magenn, Swiss Kite power, Sky Wind Power, Skysails, Joby Energy etc. have already launched such out-performing models in form of market-ready finished products. “The National Renewable Energy Laboratory (NREL) of the U.S. Department of Energy publishes an annual report which could be found at www.nrel.gov/publications ” Singh adds. Singh says that presently the system is still being developed and we are looking at funding for the next stage. We are open to investment from India as the country is a primary market for the solution. Our solution, in particular, can be used as an ‘energize platform,’ serving multiple purposes. Hence, we are not limiting ourselves to energy production.
HAWE technology and the limitations to its adoption
Michael Perlberger, Founder, Brainwhere GmbH, speaks on High Altitude Wind Energy Systems (HAWE). He says: “With the growing population and energy need on the one hand and the availability of enormous amounts of high altitude wind energy, India is a country that will explore with new technology.” While highlighting the limitations to the KGS system, he says that the industry is doing enough to research, experiment and find solutions concerning performance. He says: “The winds across the Himalayas are pretty constant in speed and direction (from west to east). The KGS system operates above the clouds therefore snow or rainfall is not so much of an issue. Air traffic is handled using classical Traffic Avoiding Collision Systems. The power electronic circuitry to act as an intermediate between the grid and the generator is easily available.”
Singh is also in agreement with Perlberger. He says: “Even if the product gets market-ready, approval from Aviation Authorities and other concerned government bodies is another challenge. The proposal of UAV and drones has already been rejected in the past due to security concerns. Still, I believe approval will be granted since the kite will cover only a specific area.” Perlberger adds and highlights that another limitation is that it is difficult to design a power electronic circuitry which will act as an intermediate between the generator and the Tethered airfoil (kite) because of the variations in speed.
Sighting another limitation, Singh points to the power electronic circuitry that acts as an intermediate between the grid and the generator, this he says, is easily available. He adds: “It is difficult to design a power electronic circuitry which acts as an intermediate between the generator and the Tethered airfoil (Kite) because of the variations in wind speed and due to complex control algorithm required to optimize the power output of a relaxation cycle-based generation like KGS.” Further, it is difficult to design a control mechanism for the orientation, the curvature of the Kite and the gearbox. Finally, he says that the ultimate task is to control and optimize the trajectory of the kite since the control algorithm is integrated to achieve synchronization between the control mechanism and the power electronic circuit. Instead of viewing the situation as a reluctance to adopt the technology, Singh says that there are only a hand-full of engineers talking about the technology. Further, major businesses dealing with wind energy have manufactured turbines. This means that they would have to bear losses if the finished products are not sold in the market. “Apart from infrastructure, the companies have invested a lot in conventional wind turbine technology in terms of intellectual property, R&D, human resource development etc,” he said. So, it is justified that established business in wind power sector will not invest in KGS technology because that will mean a huge loss to them. However, start-ups may utilize this opportunity to bring a breakthrough and capture the market in India.
Improving control and optimising trajectory: The adoption of KGS system
Singh says that researchers around the world have already utilized Fuzzy and PID control to solve the problem in the past. A better control strategy was proposed by Mariam Ahmed, Ahmad Hably and Seddik Bacha in 2012. The control strategy proposed is divided into two parts. The first aims at generating an optimal reference orbit with an optimal tether radial velocity. In the second part, a nonlinear Model Predictive Control (MPC) strategy that allows an optimal tracking under constraints of the generated orbit is implemented.