Accelerating The Development Of Marine Energy Engineering Essay Example
Accelerating The Development Of Marine Energy Engineering Essay Example

Accelerating The Development Of Marine Energy Engineering Essay Example

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  • Pages: 14 (3705 words)
  • Published: August 13, 2017
  • Type: Analysis
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The previous divisions have demonstrated the potential for the feasibility of Ocean energy devices and a mindset that SKF will have to evaluate its bearing prices in the future. The clear indications that there are still major technological and economic work and challenges ahead to overcome before ocean energy devices are considered commercially deployable have been based on a lot of assumptions and uncertainties. These challenges can be seen as hindering the development of the marine energy sector. In the following section, exploring how the challenges can be addressed by all manufacturers can help accelerate the technology:

  • Design variety and consensus: Marine energy innovation activity is spread across a wide range of concepts and components. In the short term, the lack of design consensus in both wave and tidal current energy fields is likely to limit the pace of development and learnin

    g. At the same time, there may be significant longer-term benefits from maintaining design diversity.

  • Parallel support for incremental and radical innovation: closest-to-market large-scale wave and tidal current prototypes (of around 1 MW units) using more conventional designs and components receive the majority of financial resources and innovation efforts across the sector as a whole - particularly from the private sector.Although it is crucial to test these more mature paradigm designs to gain experience, there is also a need to explore more extreme options that could lead to significant improvements in performance or cost reduction in the long run. However, given the longer timeframes required for these extreme innovations, public support remains important.

    Due to the early stage of marine energy engineering development, there is currently limited experience in real operating conditions

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One way to accelerate development is by sharing feedback and data on paradigm performance and operational experience at earlier stages of the innovation chain. However, commercial competition may restrict the extent of knowledge transfer.

There are several generic technologies and components that can be applied across the marine energy sector, such as foundations, moorings, marine operations, and resource assessment. While these present opportunities for shared or collaborative learning, the support and transfer of generic knowledge and components are constrained by commercial competition.

  • Knowledge and engineering transportation from other industries, such as offshore technology and offshore air current, offer significant opportunities for knowledge and engineering transportation. In order to enable this transportation, it is important to understand the costs associated with adapting components and methods to the Marine context. Additionally, it is important to identify and take advantage of specific opportunities for collaboration with other industries or supply chain partners.

The progress of Marine energy technology is highly uncertain. The scenario of accelerated Marine development presented here is sensitive to assumptions regarding capital cost and technical performance, as discussed in the previous section.

The Marine scenario offers a potential path for development, assuming realistic levels of technological advancement. It is important to note that achieving the high and sustained levels of innovation and acquisition assumed relies on establishing an efficient Marine energy invention system, although the specific details of this system are not further explained. However, these guidelines could support SKF in future decision making and have an impact on its involvement and growth in the market. In practice, there are significant technical, economic, and institutional challenges involved in providing this. In the short term (until 2020), there

are substantial obstacles to deployment, such as planning and legislation issues, skills shortages, and availability of installation vessels. Another challenge may arise in relation to intellectual property protection.

Despite progress, grid support may still be a significant challenge in the future. In the next decade, cost reductions in the Marine industry will be based on niche-learning and consensus on design, as a small number of wave and tidal device designs become industry standards. This could lead to consolidation of developer companies through mergers and acquisitions, enabling the emergence of the best technologies and reducing costs. However, beyond 2035, the direction of marine energy innovation is uncertain. To achieve sustained progress as seen in the Marine scenario, second generation technologies with more efficient resource extraction and conversion will likely be needed. In the meantime, it is important to have supportive measures and policy strategies that allow for research, development, and testing of unconventional and disruptive technologies. Funding long-term research and development programs from public sources plays a crucial role in enabling innovation over time.

Prolonging the acquisition assumed in the Marine scenario over the long term will also require the development of a more global Marine energy industry, along with its associated innovation system, in the medium and longer terms. Institutional and infrastructure barriers, such as supply chain restraints, planning constraints, and grid support, may have already been addressed in the long term. However, there may be new technical or infrastructure challenges as resources in deeper waters or more difficult locations become exploitable by then. Additionally, competition from other sectors for materials and financial resources may impose longer-term limitations on the sector.

Benchmarking of Ocean Energy Devices


to the SKF model, the next step in our strategy was to identify all the technical aspects surrounding Ocean Energy technology. In fact, in this section, benchmarking the devices will allow SKF to identify leading device manufacturers in both Tidal and Wave energy technology.

The following section will shed light on criteria for benchmarking wave and tidal devices, in relation to the assumptions discussed in previous sections. Figure 31 demonstrates the main challenges that device manufacturers must confront in order to achieve long-term success in the industry. These challenges are not exhaustive or strict guidelines, but overcoming them will greatly enhance the durability of the devices.

The primary wave-body interface serves as an effective wave-maker.

It is crucial to establish a strong correlation between the fluid motion in the immediate vicinity of the device and the far-field fluid motion associated with wave activity in commonly occurring seas. This leads to an efficient extraction of wave power, as there is a symbiotic relationship between wave generation and absorption. However, as the magnitude of the body's motion increases, its ability to generate waves should progressively diminish.

This means that as the size of the waves increases, the moving structure becomes less affected by the wave-induced unstable atom motion. This limits the amount of power that needs to be converted.

The device can prevent excessive loading in storms.

In addition to reducing the coupling as the sea state increases, the device must have the ability to enter a 'fail safe' mode where it completely avoids the extreme wave loads during storms. This is a last resort measure, as ideally the device should continue producing power during storms due to significant decoupling from the waves.

It is not economically feasible to construct a system that can withstand extreme loads, as it is only required for a very small percentage of time and remains mostly unused.

The device needs to have a broad frequency response

The device must be able to effectively control and amplify the power of incident waves across a wide range of frequencies. In a physical system, stored reactive energy can be converted into kinetic and potential energy, while active power is related to power control and radiated power. At the system's natural frequency, there is no fluctuation in reactive energy because the incident wave force and the working surface speed are in phase. Therefore, to achieve a broad frequency response, the device's dynamics must ensure that this is mostly achieved across a range of frequencies, and there are various ways to achieve this. For example, by having two or more natural frequencies within the frequency range of the waves, their responses can combine to provide a broad bandwidth. This can be accomplished by using "harbors" in front of floating water columns (Count; Evans 1984).

Alternatively, the concept of 'slow tuning' can be utilized to adjust the stored kinetic or potential energy based on the sea-state. This ensures that even with a narrow bandwidth, the natural frequency of response is centered on the incident wave frequency to maximize performance. Another approach is known as 'phase control' or 'complex-conjugate control', where the kinetic or potential energy is adjusted wave-by-wave to optimize performance (Budal; Falnes 1980; Salter et al. 2002).

Furthermore, the device is not limited to specific sites and can be produced on a large scale. These factors help minimize both production and

design costs. Based on our experience with two wave energy converters in Islay, the cost to design and manufacture customized components is significantly high, making site-specific versions undesirable. By implementing mass production techniques, there is potential for significant cost reductions, especially in the power take-off components.

This means that other device elements should be adjusted to fit the dimensions of a mass-produced faculty. Dependability of the components will also improve with mass-production due to increased design efforts and experience gained from their usage.

The device features shorter and more direct burden paths.

Using short and direct burden paths is a well-established design principle, particularly important in the design of wave energy converters, as they need to transmit large forces. This factor affects the size and cost of structural elements in the device.

The burden scenario for moving ridge energy convertors is complicated due to the oscillatory and distributed nature of the incident moving wave force. Both the entire device and serviceable components can be easily removed. Working at sea is more costly and risky compared to working on land. Additionally, the sea-state can greatly limit the periods when the device can be serviced, reducing its availability.

The ideal scenario for sea bed mounted devices is that all the parts requiring maintenance can be easily removed and serviced at a central location. This means that a portion of the device that can't be serviced stays at the site. This also makes installation easier. Floating devices should be simple to disconnect from moorages and power take-off connections and be towed into a dock.

The challenges stated above serve as a guideline for future developments of new ocean energy devices and as a partial

evaluation of the ability of makers of these devices to ensure their long-term survival. However, judging based on these standards is complicated due to limited publications from makers, which is a result of both precautionary measures and competitive factors in this field of engineering. The investigation conducted by the Renewable Section at SKF has identified over 240 device developers for tidal and wave energy devices. Furthermore, it has revealed that research workers and developers have varying designs and are at different stages of testing and development. To enable a comparison of these devices using a simplified benchmarking technique, a set of common criteria for evaluation was established based on the economic and developmental aspects. The Renewable Section at SKF identified "success factors" to gain an initial understanding of device makers and the type of devices they are developing, as described in the previous chapter.

CoE cannot be easily determined and is expected to be much higher than other renewable energy devices. The importance of factors relative to each other has been established through weighting, based on extensive analysis within SKF and relevant literature to make informed decisions on device developers with the highest potential.

Benchmarking Wave Energy Devices

The scores and weightings for each device can be found in the Appendix. The benchmarking of wave energy devices has been conducted by evaluating the performance of top-performing devices. This benchmarking is crucial to determine the type of devices that SKF needs to focus on in order to directly enter the market.

The benchmarking should be utilized as a primary factor for assessing the potential supply of SKF plain bearings and their position as a five-platform provider. Pelamis and Aquamarine are

the main developers who are currently in the commercial stage and are constantly innovating to remain at the forefront of the wave energy market. Additionally, it is worth noting that out of the top six leading devices, four belong to the larger family of point absorbers. Evaluating the potential of point absorbers requires considering the definition of each device. Attenuators primarily rely on the length of the incident wave (period T) to generate energy, while eradicators are more influenced by the amplitude of the wave. However, point absorbers are affected by both the period and amplitude of the wave in terms of energy generation.

This evaluation is based on the definition of each category. Additionally, the effectiveness of point absorbers can be seen in their CoE, as their design and size are much smaller compared to eradicators and point absorbers. This results in a lower CapEx, which significantly decreases the cost of electricity. The goal is not to demonstrate the advantages of one category over the other, but as a provider to this industry, it is important to know where the focus should be on short-term development for immediate impact and to set a trend for the long-term.

Benchmarking of Tidal Energy Devices

The same weightings have been applied to evaluate tidal energy devices, and the scores can be found in the Appendix. The leading developers in the tidal energy field.

In the case of tidal energy devices, there is no distinct household, except that all devices are horizontal axis turbines. These turbines are more efficient and can operate on a larger scale and withstand harsh ocean conditions compared to perpendicular turbines. This development is similar to the early

stages of wind energy turbines, where various types of perpendicular axis turbines were initially used before the commonly used horizontal three blade turbines of today.

Energy Devices Viewed by SKF

This section is part of SKF's management strategy and aims to explore and identify the technical section established. The purpose of this section is to analyze and understand the possible implications for SKF, specifically in relation to plain bearings used in such applications. Each device operates differently and possesses unique technologies. However, as an initial assessment, evaluating the categories can help determine the requirements for each device.

Bearing Applications in Ocean Energy

In this subsection, we provide an overview of each category of ocean energy devices and discuss the specific bearing applications required for each category. This analysis is not exhaustive and may not apply to all devices in each category. However, by examining leading devices in each category, we can identify trends in demand for SKF bearings and device makers' requirements.

Wave Energy Converters

Exterminators: Aquamarine Power Oyster

Aquamarine Power is currently developing their third-generation wave energy converter device called the Oyster 800. As the name suggests, this converter is expected to generate approximately 800kW of power by harnessing the energy from incoming waves. The Aquamarine Power Oyster device captures the energy from nearshore waves using a pump controlled by the wave's motion, which compresses water. The high-pressure water is then directed towards an onshore hydroelectric turbine, where it is converted into electricity.

The Oyster is a large construction that is connected to the ocean floor. It consists of a floaty structure with a hinged flap attached to

an anchored construction at a depth of approximately 15 meters. The flap is mostly submerged under water and moves back and forth in response to the waves. The central focus is the connection between the flap and the main structure, which can only be achieved through a bearing that allows for the motion of the flap. The bearing's location at the baseline of the flaps is shown in Figure 33. Its importance lies in ensuring the proper functioning of the construction, as it must withstand high impacts from the waves. The bearing will primarily bear radial loads, as well as some sway loads.

The smooth running of the one-degree of motion device relies on the proper distribution of loads on the flap. To address the issue of non-uniformly distributed loads, a bearing is needed. Eradicator devices, starting with the original design of the Pendulor in Japan, have similar working principles. The size and operating conditions of the bearing are crucial, often requiring suppliers to make exceptions outside their standard catalog. One proposed solution is to use a spherical field bearing capable of tilting and correcting alignment to resist heavy loads while maintaining smooth operation. In applications like this, bushings are often used due to the concentrated burdens on flexible joints caused by the construction's weight and impact loads on the flaps. However, it is important to assess the burdens on the bushing's appendages as they cannot withstand the same conditions as their central counterparts. The use of washers can help reduce fatigue on the appendages of the bushings, but it is also necessary to consider the distortion moments caused by the flap on the flexible joint

and whether the bushing can tolerate certain bending for smooth operation.

Attenuators: Pelamis

The Pelamis wave energy converter falls into the category of attenuators in terms of wave energy devices.

The word Pelamis is derived from the Latin term for snake, and the design of the machine resembles that of a drifting sea snake. Comprised of five tubing subdivisions connected by universal joints, the Pelamis machine can flex in two directions. This machine floats semi-submerged on the water's surface and naturally aligns itself with the direction of the waves.

When waves travel through the machine, they create motion in the water. This motion is converted into electricity using hydraulic power systems located in each part of the machine. The power is then transmitted to shore using standard underwater cables and equipment. The movement of the machine is controlled by bearings that need to withstand the back and forth motion of each part. This creates significant loads on the bearings compared to other devices. According to a Senior Engineer at Pelamis, their biggest challenge is managing the loads and motion in a constantly changing environment, while also maximizing power generation. The forces generated at each part of the machine can be several hundred metric tons, which poses significant challenges for the bearings as they have to handle the reactive forces from the motion.

The bearings play a crucial role in attenuators, as they are essential for the device's efficiency. A smooth-running bearing can maximize the output of the Pelamis or any other attenuator by reducing sticking and frictional losses. Due to the fluctuating loads and constant changes in direction, the bearing must withstand both high

radial and axial loads. This suggests that spherical field bearings may be suitable for these devices, as they can withstand the loads and vibrations to some extent.

Point Absorbers

It has been observed that point absorbers work differently from attenuators and eradicators. Point absorbers can be divided into subfamilies, including OPT, WaveBob, WaveStar, and OceanLinx. Although they have similarities, these devices use different technologies to harness energy from waves.

The Wavestar machine generates electricity by harnessing wave power through floats. These floats rise and fall with the movement of waves and are connected to a platform supported by legs secured to the sea floor. The motion of the floats is converted into rotary motion using fluid mechanics, which powers a generator. The bearing system in these devices is similar to that of oscillators, as the floating body moves back and forth due to changes in wave heights, causing the bearing to oscillate and carry the loads from the arm and floating setup.

The suggestion is to use a bushing for a specific application, where the main concern is the inactive burden of the hinged arm with the hydraulic random-access memory. However, this proposal can only be considered if the arms are not in the path of the incident wave. If the wave is perpendicular to the arms, shock loads will cause higher bending moments on the arm and relatively higher axial loads that a bushing cannot withstand. It is important to determine the direction of the waves to effectively use bushings. However, a spherical field bearing can withstand all these undesired conditions on bushings and eliminate the need to worry about unwanted radial loads

extracting wave energy. On the other hand, OPT and WaveBob have similar operating principles where they generate electricity from the vertical motion of the float in relation to the stationary spar. This motion drives a mechanical system connected to generators and produces AC electricity. The electricity is then rectified and inverted into grid-compliant AC, which complies with international interconnection standards.

The bearing criteria in these devices primarily rely on the power take-off system. Linear bearings are utilized in various applications, including conveyance within mills, milling machines, assembly lines, lifts, forklifts, precision measuring equipment, and actuators. Linear motion can be accommodated by employing sliding carriages on guide tracks. These carriages incorporate reciprocating ball bearings, roller bearings, or impact-resistant polymer surfaces to slide against the steel rail.

These various types of additive guides and profile tracks are commonly produced by companies like SKF, Rexroth Bosch Group, INA Schaeffler Group, Hepco, and IGUS. The choice of bearing mechanism depends on the torsion, load capacity, speed, and service life of the application. For the design of a WEC, this type of bearing would be suitable as the guides can keep the moving slides on a rigid, straight path. A sliding device would work best, particularly with the use of polymer materials that are resistant to wear and abrasion, such as those manufactured by Glacier Garlock Bearings and Deva-tex, Deva (2010); GGB.

Roller paths necessitate specific chambers, proper lubrication, a means of return, and low loads in order to have a prolonged lifespan. If there is a need for unlimited movement, such as in milling machines, linear ball guides, linear bushings, and linear roller guides are the most suitable as they exhibit easy

wear. For limited movement applications, such as microscopes or high-speed precision measuring devices, crossed roller bearings or stroke rotary bushings offer very precise motion due to their tight tolerances but with a shorter lifespan due to maintenance requirements.

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