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СКАЧАТЬ 2.3.2.2.4 Integrated Turbine and Foundation Installation

      Using this technique, wind turbines are assembled and pre‐commissioned in nearby place and after that a complete and integrated turbine which includes a rotor, tower and foundation is installed in a single offshore operation (IRENA 2016). Thus, using this technique most of the offshore installation operations can be put to an end. With the help of customized vessels or tugboats, the combined turbine foundation is taken to the wind farm site. Use of this technology in the floating foundation technique will further make the usage of the latter more promising. As far as fixed foundations are concerned, use of gravity‐based foundations that can be floated out and sunk at the site is more useful. Installation cost as well as the exposure to health and safety risks decreases by these innovative techniques. Projected commercialization of this technique is by 2025 with more advances in technology to fulfil the requirement of large turbines.

       2.3.2.2.5 HVDC Infrastructure

      This technique is based on the electrical interconnections. For the offshore wind farms which are located between 80 and 150 km, HVDC transmission is preferred over HVAC (high‐voltage alternating current). At present, this is an expensive technique; however, with the help of invention in the offshore installations and component techniques, its cost can be reduced in future. This technique comes with an advantage i.e. installation of a wind farm in a further offshore region which has rich wind resources. In future, this technique can lead to higher annual production of energy with less planning. Further this technology opens new doors for the regions where near‐shore developments are not possible (IRENA 2016). With the invention of direct current nodes in upcoming time, a multi‐nodal network can be built which is required for integration of this technique. With point‐to‐point grid connections used on few projects in European waters, commercialization of this technique is ongoing.

       2.3.2.2.6 DC Power Take‐off and Array Cables

Same as HVDC infrastructure, this technique is also based on the electrical interconnections. It is in its infancy; however, using this technique, the industry can get rid of the other half of the conventional turbine power conversion system which converts back to grid‐frequency alternating current (AC). This technique saves the capital cost and enhances reliability. By shifting towards DC collection, the array of cable cores decreases to two from three and the amount of material also reduces by 20–30% (IRENA 2016). Progression of this technique is happening at a slower rate due to non‐acceptance of higher‐voltage AC array cables by the industry.

       2.3.2.2.7 Site Layout Optimization

      For energy production from wind farms, different options of site layout are analysed with the help of software tools commonly described as wind farm design tools. One of the tools is WAsP model which calculates wind flow of the site (IRENA 2019a). With the help of these tools, various predictions are done by calculations, namely variation in wind speed with height, variation in wind speed over the site area and the wake interaction between wind turbines. In this technology, usage of software tools enables more informed and complete layout of wind farm which enhances the characterization of wind resources, aerodynamic wake effects, meteorology oceanic climate and seabed conditions (IRENA 2016). If installation process methods and foundation technique are further combined with layout, then energy production from the wind farm will be more effective.

       2.3.2.2.8 Other Techniques

      Along with major techniques as discussed above, there are some techniques which are attaining a commercial stage. One of the techniques is ‘Airborne Wind’ in which flying turbine devices which have 90% less mass than traditional wind turbines are used (IRENA 2016). At 300 m above altitudes, these turbines can generate power from the low‐speed winds. This technique covers a range of concepts such as rigid wings and airborne rotors. This technique can generate electricity at a lower cost due to less material usage, low capital expenditure and higher energy production compared with conventional turbines (IRENA 2016).

      Apart from innovations in technologies, developments are also taking place in operation, maintenance and services (IRENA 2016). Due to higher growth rate in offshore wind turbines, there is a need of advances in the technology systems to keep track of turbines and to avoid failures. One such operation and maintenance tool is ‘Condition Monitoring Systems’ which help operators to forecast any problem with the working of wind turbines or failure of any components so that replacement can be done in advance to avoid any accident (Froese 2017).

      2.3.3 Hydropower

Energy resulting from the running water is termed as hydropower. Harnessing energy from water is one of the ancient methods used by the Greeks to run wheels for grinding grain. It is an inexhaustible and clean source of energy without consumption, pollution, emission of waste gas and other wastes. Utilizing hydropower is one of the efficient ways to achieve low‐carbon emission and meet the Paris climate goals. Its contribution in power generation is maximum among all renewables, World's largest hydropower plant in China – ‘Three Gorges Dam’ with 22.5 GW capacity is a great example of this renewable source. First time in the history, contribution of hydropower reached just 50% in the year 2018 due to more growth in solar and wind energy sector. In recent times, its growth rate (2% in 2018) continued to slow, with only China adding a substantial amount of 8.5 GW in 2018, as per IRENA report (IRENA 2019f). Hydropower plants are classified into two types, namely with dams and reservoirs or without. Hydropower plants with dams and reservoirs produce electricity at a large scale while the other type produces at a smaller scale.

      Hydropower technology has reached a mature level as compared with other renewable sources, namely solar and wind. Thus, advances in identification and implementation of radical design which can change the operative method of hydropower have less potential. However, development of new methods in design, planning and operation of a hydropower station still has many opportunities (Kougias et al. 2019). Recent advances in the hydropower sector show increment in efficiency, flexibility of operations, durability and cost reduction of installation, operation and maintenance. Developments in technologies are needed for this sector to respond to changing climate conditions, expanding markets and variabilities of electrical power systems. Further, novel developments for upgradation and refurbishment of current facilities in hydropower are required in accordance with the environmental standards.

      2.3.3.1 Flow Control Technologies

      The flexibility in electricity generation from the wind and solar renewable source poses some challenges on power generation from hydro. To fulfil the demand of variable energy production along with limited capability for energy storage, hydraulic turbines need to operate at a wide range and changing conditions (Valero et al. 2017). Recently, some developments have taken place in control technology to reduce the flow instabilities which occur due to self‐induced instability in the operation of hydro turbines. Several techniques have emerged which decrease the flow instabilities in hydro turbine operation. These comes under passive and active control techniques (Kougias et al. 2019). Number of techniques are reported under these two types of control technologies. Some other techniques have also been reported by a recent research known as ‘Magneto‐rheological control techniques’ (Trivedi et al. 2015) which uses magneto‐rheological brake to mitigate flow instability along with the decreasing speed of the runner.

      2.3.3.2 Digitalization of Hydropower Plants

Hydropower plants were established and designed decades ago, so to meet today's requirement of variable energy demand and face the present environment conditions, they need digitalization of operative СКАЧАТЬ