Digital twins are virtual replicas of physical assets, processes, or systems. They leverage real-time data and simulations to model the behaviour, performance, and condition of their real-world counterparts. In the context of hydropower plants, a digital twin of the entire facility can be created, capturing intricate details of turbines, generators, reservoirs, dam structures, and the surrounding environment. This virtual representation enables operators and engineers to gain insights into the plant’s operational status and behaviour without being physically present at the site. Moreover, digital twins allow for testing different operational scenarios and evaluating their potential impact before implementing changes in the physical plant.

Benefits of digital twins in hydropower

• Optimizing Performance: Digital twins enable hydropower operators to monitor the entire system in real time. They provide insights into turbine efficiency, water flow, and energy generation, empowering operators to identify inefficiencies and fine-tune operations for maximum output.

• Predictive Maintenance: By continuously analyzing data from sensors and historical performance, digital twins can predict potential equipment failures. This proactive approach to maintenance minimizes downtime and reduces repair costs, leading to substantial savings for hydropower plants.

• Safety Enhancement: Digital twins can simulate extreme scenarios and emergency situations, enabling operators to devise and practice safety protocols without endangering personnel or the environment. This enhances overall plant safety and mitigates potential risks.

• Environmental Impact Mitigation: Real-time monitoring of water levels and flow patterns facilitates better environmental management. By understanding the impact on local ecosystems, hydropower operators can make informed decisions to minimize ecological disruption.

• Improved Decision-making: Digital twins provide a data-driven foundation for decision-making. Operators can simulate the consequences of different strategies, leading to well-informed choices regarding plant configurations and energy generation.

Enhancing flexibility and efficiency in the value chain

Digital twins call for powerful software systems that seamlessly implement them along the entire value chain of hydropower plants. From planning and designing products, machines, and plants to operating products and production systems, this integration empowers users to act more flexibly and efficiently, customizing their manufacturing processes.

• Digital Twin of Product: The digital twin of a hydropower product is created as early as the definition and design stage. Engineers can simulate and validate product properties based on specific requirements, such as stability, intuitive use, aerodynamics, and reliability. Whether it involves mechanics, electronics, software, or system performance, the digital twin allows for thorough testing and optimization, resulting in better-performing products.

• Digital Twin of Production: The digital twin of production encompasses every aspect, from machines and plant controllers to entire production lines in a virtual environment. This simulation process optimizes production in advance, leveraging PLC code generation and virtual commissioning. By identifying and preventing sources of error or failure before actual operation begins, this approach saves time and lays the groundwork for efficient mass production, even for complex production routes.

• Digital Twin of Performance: The digital twin of performance is continuously fed with operational data from products or the production plant. This enables constant monitoring of status data from machines and energy consumption data from manufacturing systems. As a result, predictive maintenance can be performed to prevent downtime and optimize energy consumption. Companies can also leverage data-driven services to develop new business models, enhancing overall efficiency in their operations.

Siemens Digital Enterprise Suite

To facilitate the adoption of digital twins in the hydropower industry, the Siemens Digital Enterprise Suite offers a comprehensive and integrated set of software and automation solutions. A central data platform enables the digitalization of the entire value-added process, while intelligent industrial communication networks facilitate seamless data exchanges within different production modules, collecting operational data in real time.

To address growing industrial security requirements, the Defense in Depth strategy from Siemens ensures effective protection for industrial plants against internal and external threats. Additionally, MindSphere serves as a platform for developing new digital business models, providing state-of-the-art security functions for data acquisition and storage in the cloud.

Customers who have embraced the Siemens Digital Enterprise Suite are already witnessing impressive achievements. Special-purpose machine manufacturer Bausch + Ströbel has experienced increased efficiency of at least 30 percent by 2020, thanks to the time saved during engineering. Schunk, the world market leader in clamping technology and gripping systems, has streamlined its engineering process, leading to shorter project timelines, faster commissioning, and increased efficiency in building similar plants.

A Vuong Hydropower has embraced digitalization to optimize operating costs and improve efficiency. Leveraging Siemens Xcelerator portfolio elements, including XHQ Operations Intelligence and COMOS, the company’s leaders can make faster and more accurate decisions.

The first phase of their digital transformation, spanning from 2021 to 2025, focuses on creating a digital twin of their hydropower facility. By digitizing the system, A Vuong Hydropower gains access to real-time transparent data and reports, enabling faster decision-making and efficient monitoring of production.

Essential tools like XHQ Operations Intelligence provide real-time management and remote accessibility of production operations via a web browser. This system equips operators with reports, alerts, and online data analysis to enhance decision-making capabilities. COMOS, on the other hand, facilitates more efficient asset maintenance, reducing downtime and increasing overall productivity. The combination of these software products creates a powerful digital twin of the hydropower plant.

Challenges and future prospects

While digital twins offer immense benefits to the hydropower industry, their implementation is not without challenges. Integrating data from legacy systems, ensuring data security, and addressing computational complexities are some of the hurdles that need to be overcome. Additionally, developing accurate digital twins requires continuous calibration and validation with real-world data, demanding a robust data management strategy.

Nevertheless, the future prospects for digital twins in the hydropower sector are promising. Advancements in sensor technology, artificial intelligence, and cloud computing will bolster the capabilities of digital twins, making them more accurate, efficient, and accessible. The integration of Internet of Things (IoT) devices will enable a broader range of data collection and enhance the real-time monitoring capabilities of digital twins.

This article first appeared in International Water Power magazine.

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In the most energy-intensive industrial sectors, such as petrochemicals, but also cement, glass and steel, the use of alternative technologies, such as the recovery of waste heat otherwise exhausted to the atmosphere, can produce both economic savings and a reduction in carbon footprint. This is why, especially in highly industrialised countries, there’s growing interest in exploiting not only the noblest heat sources, thermodynamically speaking, ie, those characterised by high energy content and high temperature, but also those flows with lower temperature and lower enthalpy content, which inherently would have a lower conversion efficiency. These latter flows need technologies that can be economically sustainable with a low upfront investment.

One possible approach is the use of ORC (organic Rankine cycle) systems, which, although based on the traditional Rankine cycle, use a fluid or mixtures of organic fluids of various kinds within the cycle. Thanks to this peculiarity, the choice of fluid used allows the exploitation of thermal resources with a range of thermodynamic characteristics.

Exergy’s ‘Smart ORC’ R&D project

To meet the technical and economic requirements for ORC systems suitable for the recovery of thermal waste at low temperatures, Exergy, in collaboration with Regione Lombardia and the EU, successfully participated in the “Tech Fast Lombardia” call for proposals of the POR FESR (Programma Operativo Regionale del Fondo Europeo per lo Sviluppo Regionale 2014-2020) co-financed by the FESR.

Exergy’s project was called “Smart ORC” and involved the development of a family of “mini” (less than 1000 kW) and “micro” (less than 100 kW) modular ORC systems with very high efficiency, building on the company’s proprietary technologies.

Thanks to the involvement of the Politecnico di Milano and local manufacturing companies in the detailed design and construction of the most critical plant components, an ecosystem for the development of further high-efficiency ORC systems and turbomachinery, both turbines and compressors, has been created.

The production of electricity employing ORC technology can be regarded as a form of distributed generation, and with the ability to input waste heat to the cycle as well as to meet the production site’s own consumption, ORC systems have the flexibility of being able to feed into the grid, self-consume or store the energy produced (in electrical or thermal storage systems).

In current small ORC systems, volumetric turbines, eg, screw or vane, or small centripetal radial turbines are used. Both these turbine types are characterised by lower isentropic efficiencies than those recorded for larger ORC-based power plants equipped with radial outflow turbines.

If volumetric machines typically have lower peak efficiencies than turbomachinery, settling at values of around 60-75% (isentropic total to static), centripetal radial turbines are penalised by the difficulty of having to dispose of the entire enthalpy jump in a single stage and, consequently, suffer from limited efficiency.

The adoption of the Exergy radial outflow turbine (ROT), a technology covered by several patents, has many advantages:

• concurrent combination of fluid expansion and increased cross-sectional area;
• mechanical components designed to be easily removable, without the need to empty the system, reducing maintenance times;
• extended bearing life due to very low vibration;
• reduced rotor leakage and friction; and
• greater freedom of choice of both pressure levels and stage pressure gradient, limiting vortex formation and reducing fluid dynamic losses.

Overall, it is a more efficient and reliable turbine technology, with low vibration levels and less noise.

The range of sizes of standard ORC modules investigated and developed in the course of the Exergy Smart ORC project has been selected to suit a wide spectrum of possible heat sources available in the industrial world: 80 kWe; 160 kWe; 210 kWe; 450 kWe; 600 kWe; 850 kWe (gross electric power).

The refrigerant R1233zd(E) is employed as a working fluid.

For these capacities, modular, compact and standardised technology enables, on the one hand, faster installation, construction and reduction in overall system costs, and on the other hand, with the selection of a specific working fluid, promises high performance in compliance with the necessary requirements of safety, non-flammability and low environmental impact.

The resulting low mass and volumetric flow rates, which are considerably lower than those found in medium and large-size ORC plants, required some adjustments to the ROT turbine, the component with the highest level of what might be called technological content.

The new machine was therefore scaled down to a smaller size, with higher rotational speeds, than the reference ROT turbine, in order to maintain its high performance.

The high rotational speeds required (up to about 20,000 rpm) led to the development of specific methodologies for modelling and performing calculations for ‘fast’ rotors, as well as the design and manufacturing of vibration reduction systems known as SFDs (squeeze film dampers), typically used in the aviation industry on commercial and military engines, to stabilise rotors operating at high rotational speeds. The great usefulness of SFD systems lies in their dampening effect on the machine.

Also, the pressurised oil chamber employed in the new machine and its fixed anchorage to the bearings provide a considerable further reduction in vibrations, which are exacerbated by the destabilising action of the rotor’s sealing labyrinths, designed to contain the fluid during its expansion.

In addition to the rotational issues, it was necessary to adopt a speed reducer for the mechanical coupling to the electric generator. While the efficiency of the turbomachine is a function of blade rotational speed, typically the generator has a rotational speed determined by the number of poles it has and the frequency of the electricity grid to which it is connected. A ‘slow’ generator is preferable to a ‘fast’ one due to efficiency losses in the machine itself and in the frequency converter (inverter) needed at high frequencies. With the aim of limiting transmission losses between the turbine and generator, a straight-tooth, seven-satellite, low-service factor planetary-type gearbox was selected, manufactured, and fully integrated into the new machine.

Family of Smart ORC modules

Following the promising results obtained on the test bench, through the R&D project described above, Exergy has acquired the necessary know-how to propose a family of Smart ORC modules plus the associated development of small and standardised turbomachinery. This broadens the application of Exergy’s radial outflow turbine to very small (micro and mini) ORC systems for electricity production from such sources as diesel engine exhaust systems and waste heat available in several industrial processes.

Application of the R&D to date is expected to increase the efficiency of mini and micro ORC systems by about 5 to 15%.

This article first appeared in Modern Power Systems magazine.

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The H2Maasvlakte FEED study is being performed by Uniper, together with Technip Energies and Plug Power. The FEED study is supported by Topsector Energie (TSE) subsidies of the Dutch Ministry of Economic Affairs and Climate.

Support from the EU Innovation Fund makes a “significant contribution” to the realisation of the project, says Uniper. The fund received 239 applications, from which 41 were selected, including H2Maasvlakte. The latter was favoured because of “Uniper’s commitment to transforming existing fossil production sites into green energy sites.”

The Rotterdam harbour area, which includes the Maasvlakte, is the largest carbon-emitting industrial cluster in the Netherlands, Uniper notes. In 2021 the area emitted 23.4 Mton of carbon dioxide and “decarbonising this area alone would contribute significantly to the Dutch overall target to reach net zero by 2050.”

“As a port authority we support, stimulate and help companies in Rotterdam to reach the Paris climate treaty goals in multiple ways, including getting infrastructure like a hydrogen pipeline network in place in time”, said Allard Castelein, CEO of Port of Rotterdam.

“The H2Maasvlakte project marks a significant milestone for Europe’s transition to more sustainable, localised energy in response to geopolitical risk and climate change,” said Andy Marsh, CEO of Plug.

The Port of Rotterdam (PoR) presents significant opportunities for green hydrogen projects, notes Uniper, with the presence of multiple potential off-takers across the planned open access regional hydrogen backbone representing a huge demand for green hydrogen.

The Maasvlakte Energy Hub is “versatile and strategically located”, says Uniper and “all the necessities for a successful energy transition come together here”, with power from offshore wind farms, a port suitable for the import of green fuels,
and “pivotal infrastructure” such as the high-voltage grid and the future hydrogen pipeline network (being built by Hynetwork Services, a subsidiary of GasUnie, working with PoR).

The MPP3 power plant, one of the key production units of Uniper’s Maasvlakte Energy Hub, has an installed capacity of 1070 MW and runs on coal, biomass and residual (waste byproduct) flows from surrounding industry. As well as electricity, it supplies steam to local industrial consumers.

The Maasvlakte Energy Hub also includes various gas-fired production facilities and a large hybrid battery. In the coming years, Uniper plans to develop applications for green hydrogen and bio-fuels at the hub, among other things.

Green hydrogen “will facilitate the energy transition for the petrochemical, mobility, power and heating industries”, Uniper believes and notes that in the Netherlands, the momentum behind hydrogen is growing.

Uniper says its Maasvlakte site “is one of the most convenient locations to realise a large scale green H2 project” and offers “multiple synergies” including:

• Sufficient land available for large-scale green hydrogen production.
• Ability to make use of existing infrastructure: grid connections; demineralised water; natural gas network (could initially be used to blend H2); and cooling water systems of existing power generation assets.
• Opportunities to recycle waste heat from H2 production.
• Availability of power from offshore wind, with 3.5 – 5.5 GW landing at neighbouring TenneT substation within this decade.
• Proximity to Rotterdam hydrogen network (Port of Rotterdam & Gasunie), less than 3 km away as from 2023. This will be integrated, in the longer term, with the national hydrogen backbone towards neighbouring Germany.
• Nearby hydrogen consumers (chemical industry) currently using grey hydrogen that will need to decarbonise to achieve EU targets.
• Ability to benefit from the major role the Port of Rotterdam is likely to play from around 2030 onwards in the import of hydrogen, for Rotterdam and the surrounding area as well as neighbouring countries.

This article first appeared in Modern Power Systems magazine.

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According to the terms of the definitive merger agreement, Prysmian Group will pay $290 per share in cash to shareholders of the Nasdaq-listed Encore Wire.

The consideration represents about 20% premium to the 30-day volume weighted average share price (VWAP) of the US-based Encore Wire as of 12 April 2024.

Encore Wire chairman, president, and CEO Daniel Jones said: “This transaction maximises value for Encore Wire shareholders and provides an attractive premium for their shares. Encore Wire and Prysmian are two highly complementary organisations, and we anticipate a bright future for Encore Wire as part of Prysmian.

“Furthermore, as part of a larger, global operation, we expect this transaction will bring additional future opportunities for our employees, whose dedication and hard work made this transaction possible.”

Through the acquisition, Prysmian Group aims to boost its exposure to secular growth drivers as well as improve the company’s presence in North America.

Besides, the cabling solutions provider intends to utilise Encore Wire’s operational efficiency and best in class service across the former’s portfolio.

The deal will also allow the combined company to better address customers’ requirements in North America by expanding Prysmian Group’s product offering.

Prysmian Group is expected to generate approximately €140m in run-rate EBITDA synergies expected within four years from the closing of the transaction.

Prysmian Group designated CEO Massimo Battaini said: “The acquisition of Encore Wire represents a landmark moment for Prysmian and a strategic and unique opportunity to create value for our shareholders and customers.

“Through this acquisition, Prysmian will grow its North American presence, enhancing its portfolio and geographic mix, while significantly increasing the exposure to secular growth drivers.”

Subject to Encore Wire’s shareholders’ approval, regulatory approvals, and other customary conditions, the transaction is anticipated to be completed in the latter half of this year.

The deal has been unanimously approved by each company’s board of directors.

Goldman Sachs Bank Europe SE, Succursale Italia is sole financial adviser to Prysmian Group while Wachtell, Lipton, Rosen & Katz is the company’s legal adviser.

For Encore Wire, J.P. Morgan Securities is serving as financial adviser while O’Melveny & Myers is the legal adviser.

In February this year, Prysmian Group secured a contract worth €1.9bn for the 2GW Eastern Green Link 2 (EGL2) subsea electricity superhighway project between Scotland and England.

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The current AP1000 activities at Khmelnytskyi are part of a Memorandum of Understanding (MoU) signed in 2022, for the deployment of nine AP1000 reactors in Ukraine.

The AP1000 is the only available operating Generation 3+ reactor that offers fully passive safety systems, modular construction design and the smallest footprint per MWe.

Currently, the AP1000 reactor is commercially operational in the US, China, and Bulgaria.

The technology is considered to be deployed at multiple other sites in Central and Eastern Europe, the UK, India and North America.

Energoatom head Petro Kotin said: “The Westinghouse company is our reliable strategic partner: both in the development and loading of alternative fuel into the VVER reactors, and in the creation of a fuel production line in Ukraine.

“During the war, we have not stopped, but on the contrary deepened and accelerated our cooperation.”

Ukraine’s Energy Minister Herman Halushchenko said: “The facilities that we plan to build at the Khmelnytskyi NPP will enable Ukraine to make the largest recovery since the Second World War. I am very grateful to Westinghouse.

“In 2020, we signed an agreement to develop fuel for VVER-440 type reactors for five years. But after the full-scale invasion, we significantly accelerated that process and did the impossible – Westinghouse, together with Ukrainian specialists, developed that fuel twice as fast.”

The first batch of Westinghouse VVER-1000 nuclear fuel has been delivered for the two operating units at the Khmelnytskyi Nuclear Power Plant.

Westinghouse manufactured the VVER-1000 fuel at its fuel fabrication facility in Sweden

The company also delivered the first batch of VVER-440 nuclear fuel to Ukraine’s Rivne Nuclear Power Plant in September last year, in a development program.

In addition to the AP1000 reactor, Westinghouse signed an MoU with Ukraine in September last year, for the development and deployment of the AP300 Small Modular Reactor (SMR).

Westinghouse president and CEO Patrick Fragman said: “Westinghouse is honoured to be a trusted partner supporting Ukraine in its pursuit of clean, reliable and secure energy for generations to come.

“This milestone moves us one step closer to bringing another AP1000 reactor online in Europe and joining our global fleet of AP1000 units in China and the U.S., and we remain proud to continue our long-standing, nearly 20-year partnership with Ukraine on proven and reliable nuclear fuel supply.”

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As of now, High-Temperature Reactor (HTR) technology is being promoted by several countries and companies, especially due to its unique inherent safety features. These features are based on the reactor concept and the fuel design itself. Accordingly, many of the small modular reactor (SMR) designs that are emerging are also based on the HTR technology.

HT-SMRs

The dream of reducing the complexity of a nuclear power plant while increasing its safety is reflected in the concept of the Small Modular Reactor (SMR). The key focus lies on reducing the size of the reactor (compared with established designs). When this requirement is fulfilled, modularity, standardisation and increased design integration can be addressed. A more integrated design results in reduced complexity and number of components. Standardisation includes the ability to deploy the reactor more flexibly with less site and grid restrictions.

Nearly all known reactor concepts from the established ones to Generation IV designs can be designed as SMRs. The International Atomic Energy Agency (IAEA) defines them as reactors of up to 300 MWe per module. Similar considerations apply to microreactors, which cover the power requirements below the SMR range.

The Generation IV design, which is meant to be the successor of the high-temperature gas-cooled reactor (HTGR), is the Very-High-Temperature Reactor (VHTR). Both HTGR and VHTR designs use graphite as a moderator and reflector while helium acts as the primary coolant. The main application of the VTHR is synchronous hydrogen and electricity generation. This is enabled by the highest possible outlet temperature: the HTGR reaches temperatures up to 750 °C, while VHTRs are expected to reach about 1000 °C.

The comparably high temperature of HT-SMRs opens the door to a variety of chemical processes, which are not feasible at lower temperatures. One example is the production of hydrogen using high-temperature water electrolysis. This allows fossil fuels substitution for process heat and tackles a large source of current CO2 emissions.

However, the technical advantages of HTRs and SMRs are worthless if safety concerns are not addressed. In addition to the inherent safety features of the SMR concept itself, there are HTR-specific advantages. SMR-specific inherent safety features are, generally speaking, based on the scaled-down design with less fissile material and less complexity.

Inherent safety features of the HTR design also come into play. One is the retention of fission products which is already ensured by the strict requirements of the HTR fuel specifications. TRISO fuel has the key feature that all fissile material is encapsulated in layers of durable silicon carbide (SiC) as well as pyrolytic carbon. Most importantly, core meltdown is practically impossible as the generated heat will intrinsically be able to passively dissipate into the environment even without an active helium cooling circuit. This is supported by the small core power density (compared to a PWR) and the large heat capacity and temperature stability of the graphite-based core itself.

HTR concepts are thus suitable to be combined with the technical advantages of the SMR, modularity, the potential for standardisation, increased design integration and reduced size. The availability of high-quality TRISO fuel is key to all HTRs. The HTR-typical high outlet temperatures can also be utilized for chemical or other industrial processes that have used fossil fuel-generated heat so far.

HTR Fuel

The key component of each HTR is its tightly-specified fuel, which allows it to operate at full performance. Starting in the early 1960s, research and development of HTRs and their associated fuel was carried out in Europe and the USA. In Europe, work was concentrated in the UK and Germany. The German HTR programme was initiated in the early 1960s as part of a civil nuclear development programme.

Within this programme, NUKEM, for example, was focused on the design of fuel elements, fuel specifications, the development of the fuel manufacturing processes and the actual production of HTR fuel. During the 1970s and 1980s NUKEM’s 100% subsidiary HOBEG (Hochtemperaturreaktor-Brennelement GmbH) manufactured and supplied more than 250,000 spherical fuel elements for the AVR experimental nuclear power plant at Ju¨lich and more than 1,000,000 fuel elements for the Thorium High Temperature Reactor (THTR-300) at Hamm-Uentrop in Germany. Based on a highly systematic approach and the development of special quality control procedures for the production processes, fuel quality was continuously investigated and quality standards were established. Consequently, the highest level of HTR fuel quality with regard to minimum fission product release was achieved at this time – and still represents today’s quality standards.

The German experimental AVR (construction began in 1961) was the origin of succeeding pebble bed HTRs like the German THTR-300 (construction started in 1971), Chinese experimental reactor HTR-10 (construction began in 1995), its power producing predecessor HTR-PM (construction started in 2012, 250 MWt per unit) and the South African PBMR (never constructed for financial reasons, 400 MWt). PBMR and the HTR-PM are examples of HT-SMRs and both use spherical fuel elements which are based on the HOBEG/NUKEM pebble manufacturing process.

As opposed to the ‘German-origin’ pebble bed reactors there is another concept based on cylindrical fuel compacts originating from the United Kingdom experimental Dragon Reactor (construction began in 1960, 20 MWt). Fuel compacts are arranged in a prismatic fuel assembly – usually a hexagonal graphite block with rod-shaped openings that are filled with cylindrical fuel compacts.

HTR fuel in the form of a cylindrical compact or a spherical pebble consists of many small uranium kernels of about 0.5 mm in diameter. Uranium can either be in the form of pure uranium dioxide or uranium oxycarbide (UCO), which is a mixture of uranium dioxide with a certain fraction of uranium carbide.

While the German Thorium-High-Temperature-Reactor (THTR-300) utilised highly enriched uranium (HEU of 93 %) with added thorium, nowadays only uranium with lower enrichment levels is used due to the risk of proliferation. High-assay low-enriched uranium (HALEU) is established as the term to describe uranium with enrichments ranging from 5% to 20%, which are usually used for modern advanced reactors, including HTRs.

Each uranium oxide or carbide kernel is coated with several layers of pyrolytic carbon (PyC) as well as a durable silicon carbide (SiC) layer. While the inner PyC layer is porous and capable of absorbing gaseous fission products, the dense outer PyC layers form a barrier against fission product release. The SiC layer improves the mechanical strength of this barrier and thus the retention capacity for certain fission products.

The proven German TRISO spherical fuel, based on the NUKEM design, has demonstrated the best fission product release rate, particularly at high temperatures. The enriched uranium TRISO particles were contained in a moulded graphite sphere. A NUKEM fuel sphere consists of approximately 9 g of uranium (about 15,000 TRISO-coated kernels) and has a diameter of 60 mm – the total mass of a fuel sphere is 210 g. In more recent projects NUKEM also developed cylindrical compact fuel based on the same TRISO fuel kernels. A cylindrical compact has a typical length of about 25 mm and 12 mm in diameter. It contains about 1.2 g of uranium per compact (about 3,000 TRISO-coated kernels).

HTR fuel production

The HTR fuel production process can be divided into four major fuel production process areas as well as two recycling areas for the recovery of uranium and other valuable materials from liquid process effluents, as well as out-of-specification solid fuel material.

In the Kernel Production Facility, fresh U3O8 powder is dissolved in nitric acid (HNO3) and mixed with special chemicals to a viscous ammonium di-uranate (ADU) solution. This solution is drip-cast (vibro-dropped) to form microspheres from many small droplets, which are then gelled, dried and calcined to form UO3. The UO3 is reduced to UO2 and sintered to a kernel. In the case of UCO kernels, a similar process is utilised to partly form uranium carbide.

Within the Coating Facility, the kernels receive four coatings using a chemical vapour deposition (CVD) process to produce the TRISO-coated particles.

In the Fuel Compact (or Sphere) Production Facility, the TRISO-coated particles are overcoated with a layer of matrix graphite powder (MGP). The MGP-overcoated particles are dosed into pressing moulds together with additional matrix graphite powder according to the desired packing fraction, which determines the volumetric fraction of TRISO-coated particles relative to the total fuel element volume. The resulting fuel element is then carbonised and annealed in two consecutive furnaces – and thereby significantly hardened. In the case of a fuel sphere, this is the final fuel element production step and it is now ready to be introduced into a fuel assembly. Fuel compacts are first inserted into rod-shaped openings within a prismatic graphite block to yield the final fuel assembly.

Two recycling areas ensure that on the one hand, almost no enriched uranium gets lost within the process and on the other hand the required chemicals are reused as often as possible. All traces of uranium from spent liquids are retrieved before they are discharged in the form of decontaminated wastewater.

The liquid effluents from the production processes are recycled and cleaned in the Effluent Treatment Facility. The main purpose is to recycle process liquids for reuse in the Kernel Production Facility. The scrap material from the different stages of the production process – including odd kernels, oddly coated kernels and off-specification fuel elements, as well as other uranium-containing materials – is recycled in the Uranium Recovery Facility to form U3O8, which is ready to be reused in the Kernel Production Facility.

The HTR fuel element production plant operates as a closed-loop system that is designed to approach a 100% overall uranium yield from the raw material U3O8 to the final fuel compact or sphere; therefore, approaching zero emission. The installed quality control procedures ensure that only in-specification intermediate products (uranium kernels and TRISO-coated particles) are used to manufacture the final fuel compact or sphere which has to pass a final quality control step.

Improvements in the HTR production plant

As it became evident in the early 2000s that there may be further interest in Pebble Bed Reactors, NUKEM reactivated the key personnel who were formerly responsible for the development and adjacent commercial operation of the HOBEG fuel production plant. This unique know-how had a significant role in the revival of the HTR fuel technology within NUKEM.

NUKEM developed its up-to-date TRISO fuel production process mainly during the design of the Pebble Bed Modular Reactor (PBMR) fuel Plant. The PBMR Fuel Plant (PFP), originally to be constructed near Johannesburg, was intended to fuel the first South African PBMR. The design of the reactor was based on the fuel specification and the equivalence of the fuel elements to the German fuel. This equivalence is important for the fuel qualification as the former NUKEM fuel has been long-term tested through irradiation tests in the German AVR reactor performed by the Research Centre Ju¨lich in the 1980s.

In the course of more recent fuel plant designs, including PMBR, the process was continuously upgraded in accordance with the most advanced international norms and standards. In general, the focus shifted from administrative criticality safety control to technical control, i.e., the application of safe geometry as far as possible. The implementation of geometrically safe equipment is superior compared to administrative measures to prevent the occurrence of a critical configuration of fissile material. Safe maximum equipment dimensions are determined for certain worst-case scenarios – these limits are kept throughout the geometrically safe areas of a nuclear fuel production plant.

A lot of equipment of the former NUKEM/HOBEG was redesigned with safe geometry considerations in place. The processes for the near-total recycling of uranium and chemicals, as well as for decontamination and purification of liquid and gaseous effluents were also developed in more recent fuel plant projects with respect to criticality safety and radiological protection.

The important revival of the existing TRISO fuel production know-how, the consideration of modern techniques and state-of-the-art safety requirements represents a challenging engineering task, which was accomplished by NUKEM at the end of the 2000s.

The main target of the current century is to continuously replace fossil fuel-generated, CO2-heavy process heat. This can be achieved by building up a fleet of HTRs. Especially, the HT-SMR, which combines the advantages of the HTR with those of the SMR. SMRs can be deployed very flexibly in industrial cluster areas with high demand for process heat and NUKEM is ready to fuel the emerging HT-SMR fleet.

This article first appeared in Nuclear Engineering International magazine.

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Manulife Investment Management spearheaded the financing round for the community solar developer and owner, joined by current investors Diamond Generating and Generate Capital. Nexamp enlisted BofA Securities as its sole placement agent for the fundraise.

Manulife Investment Management managing director Pradeep Killamsetty said: “We believe in community solar and Nexamp has built an exceptional platform to meet the moment.

“We are proud to support the Nexamp team in their efforts to further expand their community reach and execute on their growth plans for a cleaner future.”

The influx of capital will enable Nexamp to speed up the implementation of its project pipeline across the US. It will also help the firm enhance its presence and collaborations in both established and emerging markets and support the ongoing development of its range of generation and consumer-focused solutions.

In January, Nexamp revealed its decision to establish a second national headquarters in Chicago and announced plans to invest over $2bn in local renewable energy infrastructure in Illinois.

Furthermore, in 2023, Nexamp initiated a collaboration with North American solar manufacturer Heliene, securing access to 1.5GW of domestically produced modules.

The modules will be deployed across numerous community solar projects spanning the nation. Presently, Nexamp serves nearly 80,000 customers and manages a portfolio exceeding 1.5GW of generating capacity, inclusive of projects under construction, with the potential to power over 300,000 households.

The company is actively developing several additional gigawatts of project capacity across more than 20 markets, with the combined potential to provide power to over one million customers in the years to come.

Nexamp CEO Zaid Ashai said: “This landmark financing comes at a pivotal moment in the evolution of America’s energy economy, and underscores the indispensable role of community solar in democratising access to clean, affordable energy solutions for every American.

“This unprecedented investment reflects swelling confidence in the ability of independent renewable energy providers to reimagine outmoded infrastructure and reshape our grid. Nexamp is committed to deep collaboration with communities across the nation in building a more sustainable future for us all.”

In May 2023, the clean energy company secured over $400m in tax equity and debt commitments. US Bancorp Impact Finance led the tax equity portion and Mitsubishi UFJ Finance Group (MUFG) while spearheaded the debt portion.

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Located on the Dniper river in the Russian-controlled southern part of Ukraine, Nova Kakhovka dam was originally constructed in 1956 and its operator Ukrhydroenergo, Ukraine’s largest hydropower generator, said the structure was now beyond repair. The breach is believed to have been a deliberate act, with Ukraine claiming that Russia destroyed it and Russia suggesting it is Ukraine who is responsible for the damage.

At the time of the dam failure, Nova Kakhovka’s reservoir was at a record high level and a catastrophic release of water ensued. Reports suggest that the central section of dam was destroyed which progressed to the failure of the eastern side of the spillway and then loss of the hydropower plant. Ukraine’s President Volodymyr Zelenskiy holds Russia responsible for the damage and called it a deliberate crime of ecocide by the Russian occupiers, saying it was “an environmental bomb of mass destruction”.

“As a result of the detonation of the engine room from the inside, the Kakhovka hydropower plant was completely destroyed. The station cannot be restored,” Ukrhydroenergo said in a statement on 6 June, predicting that the reservoir would be drained within four days. Ihor Syrota, Ukrhydroenergo’s CEO, described the incident as a ‘barbaric act of destruction’ and said that there will be environmental consequences in addition to the immediate destruction of the station.

ICOLD condemned such action “in the strongest possible terms”, adding that the consequential cost in human, environmental and economic terms cannot be justified in respect of any military objective. UN Secretary-General António Guterres described it as another devastating consequence of the Russian invasion of Ukraine and that attacks against civilians and critical civilian infrastructure must stop. While UN Under Secretary-General for Humanitarian Affairs and Emergency Relief Coordinator, Martin Griffiths, said it was possibly the most significant incident of damage to civilian infrastructure since the start of the Russian invasion of Ukraine in February 2022. International humanitarian law is very clear, he commented, and structures such as dams must receive special protection as their destruction can cause severe loss for the civilian population. Constant care must be taken to spare civilians and infrastructure throughout all types of military operations, Griffiths added.

Expressing its dismay concerning the damage caused to the Nova Kakhovka dam, the International Hydropower Association (IHA) said that although much is still unknown about the circumstances of the incident, it is clear that communities will be dislocated, large amounts of clean energy and water lost, and livelihoods severely affected.

Eddie Rich, IHA Chief Executive, said that the worldwide hydropower community will want to join with IHA in offering sympathies to those affected by the tragedy. IHA called for infrastructure workers in Ukraine to be allowed to fulfil their duties and encouraged the association’s network to support the redevelopment and reconstruction process as and when the time comes.

Catastrophic

Previously spanning an area of more than 2000km2 and Ukraine’s largest in terms of water volume, the Nova Kakhovka reservoir was described as being “catastrophically shallow” on 26 June after flooding caused by the suspected explosion. The Dnipro River has now returned to its old channel and in some places is just a stream, while shallower parts are being exposed for the first time since dam construction almost 70 years ago.

Following the incident, Ukraine lost about 14.4km3 of water and 35% of the annual flow rate of the Dnipro River, while the water level in the Dnipro riverbed near the station is currently less than 2m.

Ukrhydroenergo confirmed that the aftermath of the explosion resulted in significant operational and environmental consequences. Despite the magnitude of the incident, the explosion did not disrupt the operating modes of several other hydroelectric power plants, and the Kyiv, Kanivskaya, Kremenchuk, and Serednyodniprovskaya hydropower plants were reported as being unaffected and functioning normally.

Nova Kakhovka dam is described as being a lifeline to the region and estimates suggest that essential water supplies to more than 700,000 people have been affected. In addition, loss of water from canal networks for irrigation purposes could prove to be critical for food production in the region. Estimates suggest the affected reservoir supplied water to more than 12,000km of canals irrigating over 500,000 hectares of cropland. A recent analysis of satellite imagery by NASA Harvest, NASA’s Global Food Security and Agriculture Consortium, shows four major canal inlets (vital for farm irrigation) have already been or are close to being disconnected. As Ukraine is a major exporter of sunflower, maize, wheat and barley, the dam destruction could have huge impacts on global food security as the region is seen as ‘a breadbasket’ for not only Ukraine but the rest of the world.

Flooding from the dam breach, which peaked at a depth of 5.6m in Kherson on 8 June, destroyed houses, roads and other crucial infrastructure, displaced more than 20,000 people and created an ongoing humanitarian and ecological crisis. Recent estimates suggest that 32 settlements on the right bank of the Dnipro River and 14 settlements on the temporarily occupied territory remain flooded. Efforts to evacuate people from these inundated areas are ongoing, and authorities are actively working to provide the affected population with drinking water and other essential resources. There have also been impacts on sanitation and sewage systems in addition to health services, with Cholera remaining the largest threat to health within the area. In addition, the receding flood water has scattered landmines far and wide in one of the most “mine contaminated” parts of the world. Although they do generally float on the water surface, there is concern they can become entangled in debris and embedded in sediment. And as the dam played an important role in regulating river flow there will now be a greater risk of flooding and drought, with warnings that unless flood defences are put in place or the dam repaired, some areas may remain unsuitable for residents to return as they are so close to the river.

Looking at environmental impacts, many believe that we have just seen the tip of the iceberg. There are fears that future agricultural activity will be reduced for many years to come as the flood water washed away the topsoil on vast areas of the farm and arable land, while fertilizers may disrupt aquatic ecosystems as they’ve been washed into the river.

The sudden surge of water downstream has had immediate and far-reaching impacts on biodiverse ecosystems, and nearly 160,000 animals and 20,000 birds are thought to be under threat, including the vulnerable Nordmann’s birch mouse and the endangered sand mole rat.  In addition, the rapid draining means that vast numbers of fish will be either stranded in shallow, dried-up zones, or swept away to sea, where they will perish in the salt water.

Described as perhaps being of greater concern, is the potential dispersal of toxic compounds. More than 150 tonnes of machine oil from the Kakhovka hydro station have spilled into the Dnieper River, The flood water also carried rubbish, together with construction waste and sewage, into the Dnieper watershed, and could potentially contaminate supplies of drinking water.

“The scale of this event is enormous,” United Nations Development Programme’s Resident Representative in Ukraine, Jaco Cilliers, said. “It is crucial that we understand the full extent of its impact,” he added.

Assistance

On 22 June, the European Bank for Reconstruction and Development (EBRD) announced it was to assist in the restoration and modernisation of Ukrhydroenergo’s hydroelectric power plants in the Ukraine, including the Kakhovka plant. The primary objective of this agreement is to address the operational challenges faced by Ukrhydroenergo’s hydropower plants due to the impact of the Russian invasion and will focus on replacing critical equipment, enhancing operational reliability, and improving efficiency across the hydroelectric power plants. Potential investment opportunities will also be identified, with a particular emphasis on the reconstruction of the Kakhovka hydropower plant and its associated infrastructure following the devastating explosion in early June.

“I am grateful to the Government of Ukraine and international partners, particularly the EBRD, for their comprehensive support in implementing Ukrhydroenergo’s key task – restoring hydropower facilities. I am convinced that by working together, we will restore the lost capacity and increase the security of our energy infrastructure,” Ihor Syrota, CEO of Ukrhydroenergo, said

Ukrhydroenergo says it is continuing to implement critical measures to restore the Kakhovka hydropower complex. In particular, ongoing negotiations with the World Bank, the EBRD, and the European Investment Bank are looking at plans to construct temporary water retention dams in the upper and lower sections of the reservoir. These will enable the accumulation of water levels up to 12.7m and restore supply in the region.

Paramount priority

Dam safety must always be given paramount priority, ICOLD says, acknowledging the difficulties Ukraine is probably experiencing in assuring dam safety across the country, due to the shortage of operational and maintenance expertise caused by the displacement of people. At its annual meeting in Sweden which was held only days after the dam breach in June, ICOLD said that the incident and its consequences were a major concern to the 1200 assembled delegates from 77 countries around the world, and offered to support and assist Ukraine in any related area that may be of benefit.

This article first appeared in International Water Power magazine.

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“This success creates further momentum working towards a sustainable future in our core market Australia”, said Katja Wu¨nschel, CEO RWE Renewables Europe & Australia, noting that “In a renewables world, battery storage is key for a reliable, secure and sustainable electricity supply.”

RWE’s energy blog, en:former, noted recently that Australia’s energy transition is picking up steam, with renewables’ share of power generation in Australia reaching 35.9% last year, more than double the level of 2017.

In particular, RWE notes, the country has embraced rooftop solar, with around one in three Australian households now having home solar systems, according to the Clean Energy Council. Rooftop solar contributed 25.8% of renewable energy generation last year, the first time it has accounted for more than a quarter of the country’s green power production, the RWE blog observes.

However, to transform truly a power system still heavily dependent on fossil fuels, particularly coal, more utility-scale solar and wind are required, says RWE. Deployment rates for utility-scale projects were down in 2022 year on year, but the recently published Clean Energy Australia Report charts clear evidence of growing momentum across the renewable energy sector:

• There were 72 large-scale renewable energy projects under construction or with firm financial commitments at end-2022, up from 66 at end-2021. These comprised 48 solar projects, 21 wind and three bioenergy. Utility-scale solar saw its largest-ever monthly generation in December, at 1505 GWh.
• The deployment of batteries increased last year to 1380 MW/2004 MWh, compared with 921 MW/1169 MWh in 2021.
• Over 5 GW of wind and solar projects started construction last year, the highest level on record.

RWE is currently developing a portfolio of on and offshore wind, solar and battery storage projects across Australia, with “political sentiment swinging behind green growth.”

Increased activity in the renewable energy sector reflects a sea change in the national mood over the past year, says the RWE blog, observing that the federal election of 2022 was dubbed the ‘greenslide’, bringing Labor back into power with a majority for the first time since 2007.

Although Labor’s majority is slim, the Green Party won 4 seats, up from 1, and a group of cross bench MPs, known as the ‘teal independents’, who ran on strong climate agendas, have 11 seats. Action has followed, notes RWE. In December, the government and the state of New South Wales announced a joint deal worth A$7.8 billion (US$5.2 billion) to support eight critical transmission grid and renewable energy zone projects. In total, the government plans a grid modernisation investment of A$20 billion under its Rewiring the Nation policy.

This huge new investment in grid infrastructure is designed to facilitate the accelerated build out of renewable energy projects in order to reach the government’s target of 82% renewable energy on the grid by 2030. The new government also legally adopted in September a target of reducing the country’s greenhouse gas emissions by 43%, relative to 2005, by the end of the decade.

This ups the country’s climate ambitions substantially from the 26-28% target advocated by the previous administration, comments RWE, and the renewable energy project pipeline has increased as a result. According to the Clean Energy Council, as of April, 16.4 GW of new renewable energy capacity had reached financial closure, representing A$23.5 billion in investment. In fact, the pipeline of all projects under consideration is much bigger – more than enough to supply Australia’s electricity needs, according to some estimates.

These include a growing number of offshore wind projects and giant solar farms. Currently more than 50 GW of offshore wind projects have been announced around the country.

Australia has gradually been putting in place the legislative framework for offshore wind, which would provide a huge boost to the construction of battery capacity, says en:former. The offshore Electricity Infrastructure Act was passed at the end of 2021. Then, in June last year, the licensing regime for the sector’s regulation came into being.

In December 2022, the government declared the Bass Strait off Gippsland (Victoria) as the country’s first offshore wind zone, an area which could host more than 10 GW of offshore wind, and July 2023 saw Hunter (off the NSW coast) declared as the second offshore wind zone, with a potential installed capacity of some 5 GW.

Nevertheless, Australia remains a large fossil fuel user and exporter, notably of coal and liquified natural gas, notes the RWE blog. It faces the twin challenge of domestic decarbonisation and transforming an export-orientated economy based on traditional fuels, but is already achieving success. In 2022, production of lithium, vanadium and cobalt – all key battery minerals – rose by 9%, 10% and 6% respectively, according to the Australia Identified Mineral Resources report. However, as en:former suggests, an even bigger opportunity may lie in clean electricity and green hydrogen exports to the energy-hungry economies of Asia, many of which also remain heavily dependent on coal.

Some of the largest renewable energy projects worldwide have been floated in Australia with the aim of securing a share of future trade in clean energy commodities.

This article first appeared in Modern Power Systems magazine.

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The T15 robot is 325mm long, 172mm wide and weighs about 0.75kg.

It is magnetically attached to the stator core inner surface, using a stator slot as a guide for travelling in a straight line.

The T35 robot is larger and described as “multi-functional”, and can be used to inspect generators with ventilation segregation baffles attached to the stators, typically found in larger machines. These baffles have proved to be problematic for robotic inspection.

The T35 employs three arms that protrude from the stator side of the robot, holding it in position between the stator and rotor, pushing it against the rotor, and enabling it to move over the rotor surface. The arms can be moved in and out to avoid the baffles.

The T35 robot is 33mm thick (with arms folded in), 700mm long, 315mm wide, and weighs about 4.7kg.

Toshiba Energy Systems and Solutions developed the inspection robots in 2018 and since then has been preparing for their commercialisation.

Early deployments of the ultra-thin robot included generator inspections in nuclear power plants and it is now available for the full range of applications. The multi-functional robots have been available for inspection services as of fiscal 2023.

In the past, turbine generator rotors were typically pulled from stators every four years for precision inspections, but the use of robotics, as well as NDT inspection technology that does not require a liquid contact medium, has reduced the need for rotor removal when looking for cracks and contributed to improved power plant load factors.

The T15 and T35 robots are equipped with top, bottom, front and rear high-resolution cameras for VT (visual testing) of the rotor and stator.

Examples of what visual examination of the stator core inner surface might show include: foreign material; scratches/damage; heating and arc indications. Rotor surface visual inspection can yield similar findings, as well as rotor wedge positions and plugging condition of rotor ventilation holes.

The robots enable cameras to be positioned on the centre lines of rotor ventilation holes, which is necessary for high-quality inspection and diagnosis of rotor ventilation plugging issues (including automated image diagnostics).

The T35 robot can perform ultrasonic testing (UT) with a detachable UT attachment, employing Toshiba-developed dry-coupling technology rather than a liquid contact UT medium, leaving no contamination post-inspection.

Both robots are equipped with hammers for checking stator wedge tightness, with automated diagnostics based on acoustic analysis of the hammering sound, and high-quality diagnostics are achieved, says Toshiba ESS.

Both robots can also be equipped with Chattock coils enabling them to perform ELCID (electromagnetic core imperfection detection).

Docking bay stations for the robots are installed on rotor retaining rings. The docking bay station inserts the robot into the air gap and moves it circumferentially. All robot movements, inspections and diagnostics are automated.

The quality of inspection that can be achieved by the new robots is said to be equivalent to that achieved by “inspection experts.”

The generator periodic major outage cycle (with rotor removal) can be extended, and preventive maintenance and planned repairs can be carried out based on an assessment of generator condition based on actual inspection data.

Toshiba ESS is using the new robots to help strengthen its service offering for fossil-fuelled and nuclear power plants worldwide.

This article first appeared in Modern Power Systems magazine.

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