Over the past few decades, technological advancements, along with finance and business model innovations, have led to notable cost and performance improvements in some renewable energy segments, particularly wind and solar photovoltaic (PV). These have become competitive with conventional fuels. A look at the key technology trends that are shaping the renewable energy sector…
Wind turbine technologies
In the wind power industry, research and development efforts have been mainly focused on the design of towers. As a result, structural systems that support wind turbines have changed considerably, from 20-40 metre steel lattice towers and guyed or self-supporting poles to 40-60 metre thin-shell steel fabricated tubes. In fact, the current standard height for steel fabricated tubes in the industry is 80-100 metres.
Research has shown that evolution in wind tower design has occurred every 10 years or so. As the global wind power industry enters its fourth decade of development, new tower designs are emerging. The industry is now increasingly adopting very tall 100-160 metre towers, which include flexible steel fabricated tube towers, multi-petal steel towers, hybrid towers constructed of both steel and concrete, all-concrete towers of post-tensioned concrete construction and next-generation steel lattice towers.
These tower design innovations are aimed at developing more efficient wind towers that can help reduce the cost of wind power. Meanwhile, some companies are experimenting with bladeless wind turbines in order to reduce the weight of the turbine and address the challenges related to the transportation of bulky components. However, the industry is yet to see utility-scale deployment of such designs.
Changes in blade designs are mainly concentrated on its aerodynamic properties. To improve the transportation of large blades, new designs such as split and segmented blades are being adopted. Shifts in blade designs are especially notable in the offshore market. Innovation in design and materials science has led to the development of high-tech blades with a length of over 80 metres. The resulting wind turbine upscaling has led to multi-megawatt offshore wind turbines flooding the market, which are capable of generating significantly higher amounts of energy.
The drivetrain, which accounts for a large part of the rotor nacelle assembly cost, is also fast becoming a key focus area for design innovations. Efforts are being made to develop drivetrains that can help reduce cost, enhance energy conversion efficiency and increase the overall reliability of the system. Turbine manufacturers are now exploring ways of using a single-stage gearbox design with the help of hydrodynamic bearings. With fewer but more efficient parts, there are less chances of component failure or jamming in single-stage gearboxes as compared to the traditional three-stage structures. Another drivetrain technology available in the market is direct drive technology. This does not require a gearbox and has fewer moving parts than geared drivetrains.
Solar PV technologies
There are two technologies prevalent in the solar PV domain, crystalline-silicon (c-Si) and thin-film PV. The solar revolution began with thin-film technology and, over the years, c-Si (monocrystalline and polycrystalline technologies) has captured the market to become the most preferred solar PV technology. Further, monocrystalline has gained a considerable share over polycrystalline and thin-film technologies as it is 2 per cent more efficient and has a higher average power output of 4-8 per cent. Polycrystalline cells can be combined with multilayered solar cells and are suitable for distributed solar PV systems.
While c-Si may be the popular solar PV technology choice, thin-film technology has multiple advantages. Although the earlier cost advantage of thin-films owing to expensive c-Si technology has now been offset, the emerging thin-film technologies are expected to further reduce costs due to their low consumption of raw material.
Meanwhile, technologies such as copper zinc tin sulphide are gaining traction (though they are still at the research stage) as they use non-toxic materials that are abundant in nature and therefore cheaper. In addition, the new flexible thin-film technology has achieved efficiencies of over 16 per cent. The light weight of thin-film modules is ideal for huge installations, especially in the rooftop solar segment. On the other hand, heavy c-Si panels require bulky mounting structures. In addition, with the advancement of technology, it is now possible to paste thin-film modules on structures, which has increased their application, particularly in building-integrated PV.
In India, the adoption of thin-film technology has been higher as compared to the global average given that the country has only recently achieved large-scale adoption. Since the module manufacturing capacity for thin-film technology was not as high as that for c-Si, it was exempt from the domestic content requirement clause under the Jawaharlal Nehru National Solar Mission Phase I Batch I. Moreover, attractive financing options from international lending institutions made the technology inexpensive for Indian solar project developers, leading to its increased adoption.
After the initial success of thin-film modules, cheaper c-Si alternatives from China and Taiwan captured the market and the share of thin-film modules in the country reduced. Since the returns are declining as solar tariffs continue to decrease, cheaper c-Si modules have become the preferred technology choice of developers for new projects. India is yet to scale up its manufacturing capacity of thin-film modules as most domestic players manufacture the more popular c-Si-based solar modules.
Energy storage systems
With solar PV and wind technologies expected to grow rapidly in the next few years, there has been increased focus on energy storage systems (ESS) to integrate these variable generation sources. Broadly, ESS can address variability, regulate electricity despatch, maintain flow control in the transmission system and improve the reliability of the power system without adding any generation capacity.
The deployment of battery energy storage systems (BESS) is gaining popularity amongst large solar power plants. The country took its first step in the segment with the announcement of a utility-scale energy storage project tender for two solar parks in Andhra Pradesh and Karnataka. Bids were invited by the Solar Energy Corporation of India (SECI) for the 100 MW Kadapa Solar Park to be built in Andhra Pradesh and the 200 MW Pavagada Solar Park to be built in Karnataka along with battery storage system. In Andhra Pradesh, bids were invited for two 50 MW solar projects with a BESS of 5 MW or 2.5 MWh. In Karnataka, bids were invited for four 50 MW solar projects, with the same storage specifications.
The size of the proposed storage systems is small (equivalent to just three minutes of power production of a 50 MW project at full capacity), and the cost implication will not be very high. As per Ministry of New and Renewable Energy estimates, assuming a price of Rs 15,000 per kWh for lithium-ion batteries, a 2.5 MWh storage unit would cost around Rs 38 million. The final impact of this, according to the ministry, would be less than 2 per cent on the total cost of the project, which would increase from Rs 50 billion to about Rs 51 billion.
Meanwhile, in 2016, SECI invited expressions of interest for the development of a 2 MW grid-connected solar project and a 0.5 MW wind hybrid project with 1 MWh of energy storage at Rangreek in Himachal Pradesh. Power Grid Corporation of India Limited is also testing various grid-scale BESS technologies through pilots in order to provide frequency regulation and energy time-shifting services in Puducherry. These include advanced lead acid (500 kW, 250 kWh), lithium-ion (500 kW, 250 kWh) and alkaline and flow battery systems (250 kW, 1,000 kWh). Private players too have been deploying storage technologies to support their renewable energy projects. For instance, molten salt thermal energy storage technology has been deployed in three concentrating solar power (CSP) plants – the 100 MW Diwikar CSP plant and the 100 MW KVK Energy solar project in Rajasthan, and the 25 MW Solar One project in Gujarat.
In April 2016, Panasonic India and AES India announced their plans to build a 10 MW/10 MWh energy storage facility in Jhajjar, Haryana. Electricity from the project, based on the AES Advancion platform and Panasonic’s lithium-ion batteries, will provide backup for a Panasonic India manufacturing site.
The way forward
In addition to these technologies, a key emerging area has been solar-wind hybrids. Industry experts believe that together with battery storage, solar-wind hybrids can prove to be an ideal solution especially in remote regions where grid power has not reached. Several domestic and overseas players have launched their wind-solar hybrid systems while many more are planning to enter this space with innovative and efficient products and solutions.
Net, net, the development of new technologies in the renewable industry have led to many innovations in products, solutions and business models. Going forward, these innovations in technologies will further improve the economics of grid-scale renewables.