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HANOVER, 28-Feb-2017 — /EuropaWire/ — Electricity from wind and solar requires systems that store electricity that will be needed at a later stage. In November the Fraunhofer Institute for Wind Energy and Energy System Technology (IWES) in Kassel tested the prototype of a storage system in Lake Constance, Europe’s largest drinking water reservoir. A hollow sphere storage system positioned 100 meters deep is designed to demonstrate feasibility in a simulated service test. ContiTech supplied the pressure equalization line for the testing of this novel underwater pump reservoir. ContiTech participated in the Fraunhofer Institute for Wind Energy and Energy System Technology’s project by developing a specialized hose. The high external pressure of 10 bar at a water depth of 100 meters is no problem for the robust hose, which is also suitable for drinking water. The principle of the hollow sphere storage system is the same as that of conventional pump storage power plants – except that it doesn’t use two basins. The novel pump storage uses the sea itself as its upper storage reservoir. The lower storage basin is formed by the hollow sphere on the seabed. When electricity is needed on shore, a valve at the opening of the sphere opens. The water flowing into the sphere powers a pump turbine that generates electricity via a generator. The current is then transmitted to shore via connecting cables. Excess electricity, such as any generated overnight, is used to pump the concrete sphere dry again. The hoses used as pressure equalization lines in the test model of the novel hollow-sphere storage power station were developed and manufactured by ContiTech in Korbach. Air can flow into the sphere through the hose when water is pumped out. That prevents insufficient pressure. The Fraunhofer Institute IWES in Kassel started the first test phase for the innovative pumped-storage power plant on the floor of Lake Constance at the beginning of November 2016. This involved sinking the 20-metric-ton hollow sphere into Lake Constance. High External Pressure The biggest challenge in developing the hose was handling the water depth of 100 meters, which corresponds to an external pressure of around 10 bar. To ensure that the hose can be used in these difficult conditions it was designed with safety factor 3 for an external pressure of 30 bar. An additional steel helix in the hose wall gives it the necessary mechanical stability. Lake Constance supplies around 4.5 million people with drinking water. Therefore the layers of the hose fulfill the requirements of the German Drinking Water Ordinance and the directives of the U.S. Food and Drug Administration (FDA). This ensures that it will not cause any changes to the taste or smell of the water. Practical Test of the Hollow Sphere Reservoir The Fraunhofer IWES in Kassel started the first test phase on November 9, 2016. This involved lowering the 20-metric-ton hollow sphere to the bottom of “the Swabian sea”, as Lake Constance is sometimes referred to in German, near Überlingen. During the four-week test researchers were able to successfully prove and test the function of the underwater pumped storage power station. As its next step, the Fraunhofer Institute plans another experiment with a large plant at a water depth of approx.700 meters. The difficulty is finding a suitable location that is close to land. This is necessary for technical reasons. Proximity to an offshore wind farm is less important. The only requirement is that a shared electricity network is used.


News Article | October 27, 2016
Site: www.rechargenews.com

While there are clearly potential pitfalls in entering any developing market, the emerging offshore nations — the US, China, Japan, Taiwan and South Korea — present a completely different challenge: the risk that wind farms could be obliterated by natural disasters. The US east coast and East Asia are both exposed to powerful hurricanes (known as typhoons in Asia), while the latter is also prone to earthquakes and tsunamis. The dangers were all too clear in September, when wind speeds of up to 185km/h (51.4 metres per second [m/s]) — ripped off blades, buckled towers and damaged nacelles at two onshore wind farms in southwest Japan. Developing turbines that can ride out these destructive forces is far from simple, says Evangelos Katsanos, a civil engineer researcher at the Danish Technical University (DTU), a specialist in extreme wind power. “[Solution design is] complicated by the sheer complexity of a turbine’s physical response — to multiple loading forces acting on blades, nacelles, towers and foundations — when subjected to the highly dynamic loads of an earthquake or hurricane.” Bernhard Stoevesandt, head of the aerodynamics department at Germany’s Fraunhofer Institute for Wind Energy and Energy System Technology, adds: “The core risk of extreme events, either earthquakes or hurricanes, is that they present circumstances, forces and loading conditions that go well beyond what conventional wind turbines are designed for.In other words, if you didn’t take these extraordinary conditions into account, a wind turbine will be at severe risk of failure.” Owing to the origins of the wind industry, conventional turbine design standards — requirements covering load, fatigue, wind conditions and turbine operations — are based around the relatively tame climatic conditions of Northern Europe. The go-to international standard for turbines is the IEC 61400-1, which specifies a maximum ten-minute average wind speed (known as a reference wind speed) of up to 50m/s (180km/h) for Class 1 certification — considerably lower than hurricanes rated Category 3 and above; and it doesn’t account for extreme seismic risks. Hurricane Matthew, which struck Haiti, Cuba and the US Southeast last month, reached speeds of up to 72.2m/s. “Because extraordinary situations occurring in hurricanes and earthquakes aren’t included in basic IEC [International Electrotechnical Commission] standards, if developers are moving into markets which present these risks, special considerations have to be applied to ensure safety,” says Stoevesandt. “Ultimately, the key to solutions is properly understanding load conditions that the wind turbine will be exposed to in its particular environment. Knowing this, you can design to withstand even extraordinary circumstances.” Kim Branner, a specialist at DTU Wind Energy, adds: “Naturally, we’re constantly working to take the risks and conditions of new markets into account. This has resulted in the latest revision of IEC 61400-1, which describes how to deal with hurricanes.”Those revisions introduced the S Class (or ‘Special’) standard, which “allows the wind turbine designer to specify particular wind speed values they wish to design for”, says Branner. For instance, Adwen secured S Class certification from DNV GL this year for its 5MW AD 5-132 offshore turbine, a machine customised for subtropical monsoon climates and designed to withstand typhoons. “The turbine features a control system called Multismart, developed by [Adwen owner] Gamesa, which enables individual pitch adjustments to be made with very fast reaction times; these adjustments mean we can adjust, and reduce, the loading transferred by the rotor to the drivetrain that may otherwise be damaging,” says Adwen chief commercial officer David Guiu. The turbine’s lightweight CompacTrain drivetrain also reduces the loads transferred to the foundations — a beneficial measure in hurricane conditions. The 5MW model has not yet been commissioned at any commercial projects, and to date Adwen has just one prototype installed at a site in the Canary Islands. However, Guiu says, “We’re looking towards the Chinese market becoming one of the main markets of the coming years. With this machine, we intend to be ready with a turbine offering reliable performance and an optimised levelised cost of energy.” Global offshore market leaders Siemens and MHI Vestas both told Recharge that their machines meet the appropriate IEC standards, but declined to go into detail about their turbines’ extreme-weather protection systems. Tokyo-based Hitachi is one of the few Asian OEMs hoping to make a big splash in the region’s offshore wind market, and has already installed a 5MW turbine at the high-profile Fukushima Forward floating wind pilot project off Japan. Unlike its Western rivals, Hitachi is building turbines with a downwind, free-yaw design that is said to improve resilience to high winds. It “reduces the wind load by orienting the rotor downwind of the tower where it is not subject to crosswinds, even when generation is halted due to high winds”, says Takahashi Matsunobu, chief project manager of Hitachi’s renewable-energy solutions business division. Most turbines use an internal yaw drive to make sure the rotors face directly into the wind, rather than away from it. “A downwind rotor relaxes blade stiffness requirements, because aerodynamic loads flex the blades away from the tower, which makes it possible to use more flexible and therefore lighter blades,” explains Scott Schreck, principal engineer at America’s National Renewable Energy Laboratory (NREL). The NREL and fellow US-government-funded Sandia National Laboratories are both working on designs for future hurricane-proof turbines and both believe that downwind rotors are the best option (see panel left). Matsunobu points out that the demonstration model of its HTW5.2-127 turbine survived three typhoons this summer. The company has already won orders to supply 5MW turbines to a 220MW offshore wind farm off the coast of Murakami city in northwest Japan, with construction scheduled to start in 2020. “From a design perspective, offshore projects in [East Asian and US] markets require exceptional considerations... naturally, the foundations are critical,” says Søren Juel Petersen, global marketing director at consultant engineer Ramboll Energy, which is working on several offshore projects in East Asia. He explains that foundations play a crucial role in structural support through damping — the structure’s ability to dissipate energy. “So we’re seeing evolution in the types of foundation concept being applied.” One of Ramboll’s projects is the 400MW Binhai North project in China’s Yellow Sea. “Owing to the risks of earthquakes and soft soil conditions, we’re using monopiles driven to depths of around 60 metres.” At such depths, foundations will be less affected by earthquakes, tremors, and notably, soil liquefaction — a phenomenon that sees soils lose their strength and stiffness as the seabed shakes, undermining structural integrity. Liquefaction is something Petersen notes is “especially a risk along the coastline of China due to wash-out of sediments from large rivers”. “Moving from China, to Taiwan, Japan and Korea, seismic loading increases — so we’re considering alternative foundation systems [there]. For instance, despite shallow waters, we’re looking at gravity-base and jacket foundations, even though, had the projects been in Europe or the US east coast, the circumstances and water depth would never have suggested jacket foundations.” Petersen adds that foundation design is additionally important as it contributes significantly to protecting electrical components.“We consider the equipment in the nacelle of the wind turbine, and transformers on offshore transformer platforms, by designing the structures so that the motions and the accelerations caused by the wind and wave action and, in particular, due to earthquakes do not exceed certain [vibration and tilt] limits as established by the equipment vendors.” Others believe that monopiles are not the best answer to the dynamic loads seen in hurricanes or earthquakes.US-based Keystone Engineering says its “twisted jacket” foundation offers a far more stable solution. “The design has a greater inherent robustness compared to a four-pile jacket, or monopile,” says Hiram Mechling, project manager for offshore renewables at Keystone. “Critically, the design — three piles radiating around a central caisson — has a major influence on how loads are transferred through the foundation and into the seabed. Instead of lateral transfer seen in monopolies or conventional jackets, there’s axial [downward] transfer of loading, allowing for more efficient use of soil strengths and ultimately rendering the whole foundation very strong and durable.” Mechling points out that two twisted jacket foundations installed on ExxonMobil’s oil field in the Gulf of Mexico survived Hurricane Katrina — which devastated New Orleans in 2005 — without incurring structural damage. “[This was] hugely significant in terms of demonstrating design robustness,” he says. Though still an emerging technology, floating wind turbines are seen by some as a better solution than fixed foundations in hurricane- and earthquake-prone regions. French outfit Ideol’s open-centred “damping pool” substructure design has already received certification for extreme conditions from Japan’s ClassNK.“Tsunamis from earthquakes don’t seem to present a significant risk to floaters as they just ride them out,” says Ideol chief sales and marketing officer Bruno Geschier. “The largest waves present far closer to shore than where we’re likely to be installing; and even exceptional rogue waves further out are ably overcome.”Some risks do extend to floating foundations, particularly related to electrical cables and mooring to the seabed, which could be affected by soil liquefaction and strong currents. But Geschier says that these components meet all requirements and have been subjected to “lengthy hydrodynamic simulations” that take site-specific data into account. There is also a concern that building in robustness to natural disasters incurs extra expense — and so exposes the new, risk-prone markets to sustained higher costs. But research by the NREL shows that resilience can be delivered cost-effectively, without compromising turbine efficiency (see panel). And as Mechling points out: “More robust design could add expense, but when that hurricane comes around, you want the assurance that you’ve built in adequate safety margins. A few more tons of steel or concrete are worth it when you consider the alternative, potentially catastrophic consequences for the wind farm.” Kimon Argyriadis, innovation manager at DNV GL tells Recharge: “I’m confident that the industry can cope with the challenges [of hurricanes and earthquakes] — just as they have with extreme cold climates. There are additional efforts required and considerations to be made. But it’s nothing that’s unsolvable.”


News Article | October 27, 2016
Site: www.rechargenews.com

While there are clearly potential pitfalls in entering any developing market, the emerging offshore nations — the US, China, Japan, Taiwan and South Korea — present a completely different challenge: the risk that wind farms could be obliterated by natural disasters. The US east coast and East Asia are both exposed to powerful hurricanes (known as typhoons in Asia), while the latter is also prone to earthquakes and tsunamis. The dangers were all too clear in September, when wind speeds of up to 185km/h (51.4 metres per second [m/s]) — ripped off blades, buckled towers and damaged nacelles at two onshore wind farms in southwest Japan. Developing turbines that can ride out these destructive forces is far from simple, says Evangelos Katsanos, a civil engineer researcher at the Danish Technical University (DTU), a specialist in extreme wind power. “[Solution design is] complicated by the sheer complexity of a turbine’s physical response — to multiple loading forces acting on blades, nacelles, towers and foundations — when subjected to the highly dynamic loads of an earthquake or hurricane.” Bernhard Stoevesandt, head of the aerodynamics department at Germany’s Fraunhofer Institute for Wind Energy and Energy System Technology, adds: “The core risk of extreme events, either earthquakes or hurricanes, is that they present circumstances, forces and loading conditions that go well beyond what conventional wind turbines are designed for.In other words, if you didn’t take these extraordinary conditions into account, a wind turbine will be at severe risk of failure.” Owing to the origins of the wind industry, conventional turbine design standards — requirements covering load, fatigue, wind conditions and turbine operations — are based around the relatively tame climatic conditions of Northern Europe. The go-to international standard for turbines is the IEC 61400-1, which specifies a maximum ten-minute average wind speed (known as a reference wind speed) of up to 50m/s (180km/h) for Class 1 certification — considerably lower than hurricanes rated Category 3 and above; and it doesn’t account for extreme seismic risks. Hurricane Matthew, which struck Haiti, Cuba and the US Southeast last month, reached speeds of up to 72.2m/s. “Because extraordinary situations occurring in hurricanes and earthquakes aren’t included in basic IEC [International Electrotechnical Commission] standards, if developers are moving into markets which present these risks, special considerations have to be applied to ensure safety,” says Stoevesandt. “Ultimately, the key to solutions is properly understanding load conditions that the wind turbine will be exposed to in its particular environment. Knowing this, you can design to withstand even extraordinary circumstances.” Kim Branner, a specialist at DTU Wind Energy, adds: “Naturally, we’re constantly working to take the risks and conditions of new markets into account. This has resulted in the latest revision of IEC 61400-1, which describes how to deal with hurricanes.”Those revisions introduced the S Class (or ‘Special’) standard, which “allows the wind turbine designer to specify particular wind speed values they wish to design for”, says Branner. For instance, Adwen secured S Class certification from DNV GL this year for its 5MW AD 5-132 offshore turbine, a machine customised for subtropical monsoon climates and designed to withstand typhoons. “The turbine features a control system called Multismart, developed by [Adwen owner] Gamesa, which enables individual pitch adjustments to be made with very fast reaction times; these adjustments mean we can adjust, and reduce, the loading transferred by the rotor to the drivetrain that may otherwise be damaging,” says Adwen chief commercial officer David Guiu. The turbine’s lightweight CompacTrain drivetrain also reduces the loads transferred to the foundations — a beneficial measure in hurricane conditions. The 5MW model has not yet been commissioned at any commercial projects, and to date Adwen has just one prototype installed at a site in the Canary Islands. However, Guiu says, “We’re looking towards the Chinese market becoming one of the main markets of the coming years. With this machine, we intend to be ready with a turbine offering reliable performance and an optimised levelised cost of energy.” Global offshore market leaders Siemens and MHI Vestas both told Recharge that their machines meet the appropriate IEC standards, but declined to go into detail about their turbines’ extreme-weather protection systems. Tokyo-based Hitachi is one of the few Asian OEMs hoping to make a big splash in the region’s offshore wind market, and has already installed a 5MW turbine at the high-profile Fukushima Forward floating wind pilot project off Japan. Unlike its Western rivals, Hitachi is building turbines with a downwind, free-yaw design that is said to improve resilience to high winds. It “reduces the wind load by orienting the rotor downwind of the tower where it is not subject to crosswinds, even when generation is halted due to high winds”, says Takahashi Matsunobu, chief project manager of Hitachi’s renewable-energy solutions business division. Most turbines use an internal yaw drive to make sure the rotors face directly into the wind, rather than away from it. “A downwind rotor relaxes blade stiffness requirements, because aerodynamic loads flex the blades away from the tower, which makes it possible to use more flexible and therefore lighter blades,” explains Scott Schreck, principal engineer at America’s National Renewable Energy Laboratory (NREL). The NREL and fellow US-government-funded Sandia National Laboratories are both working on designs for future hurricane-proof turbines and both believe that downwind rotors are the best option (see panel left). Matsunobu points out that the demonstration model of its HTW5.2-127 turbine survived three typhoons this summer. The company has already won orders to supply 5MW turbines to a 220MW offshore wind farm off the coast of Murakami city in northwest Japan, with construction scheduled to start in 2020. “From a design perspective, offshore projects in [East Asian and US] markets require exceptional considerations... naturally, the foundations are critical,” says Søren Juel Petersen, global marketing director at consultant engineer Ramboll Energy, which is working on several offshore projects in East Asia. He explains that foundations play a crucial role in structural support through damping — the structure’s ability to dissipate energy. “So we’re seeing evolution in the types of foundation concept being applied.” One of Ramboll’s projects is the 400MW Binhai North project in China’s Yellow Sea. “Owing to the risks of earthquakes and soft soil conditions, we’re using monopiles driven to depths of around 60 metres.” At such depths, foundations will be less affected by earthquakes, tremors, and notably, soil liquefaction — a phenomenon that sees soils lose their strength and stiffness as the seabed shakes, undermining structural integrity. Liquefaction is something Petersen notes is “especially a risk along the coastline of China due to wash-out of sediments from large rivers”. “Moving from China, to Taiwan, Japan and Korea, seismic loading increases — so we’re considering alternative foundation systems [there]. For instance, despite shallow waters, we’re looking at gravity-base and jacket foundations, even though, had the projects been in Europe or the US east coast, the circumstances and water depth would never have suggested jacket foundations.” Petersen adds that foundation design is additionally important as it contributes significantly to protecting electrical components.“We consider the equipment in the nacelle of the wind turbine, and transformers on offshore transformer platforms, by designing the structures so that the motions and the accelerations caused by the wind and wave action and, in particular, due to earthquakes do not exceed certain [vibration and tilt] limits as established by the equipment vendors.” Others believe that monopiles are not the best answer to the dynamic loads seen in hurricanes or earthquakes.US-based Keystone Engineering says its “twisted jacket” foundation offers a far more stable solution. “The design has a greater inherent robustness compared to a four-pile jacket, or monopile,” says Hiram Mechling, project manager for offshore renewables at Keystone. “Critically, the design — three piles radiating around a central caisson — has a major influence on how loads are transferred through the foundation and into the seabed. Instead of lateral transfer seen in monopolies or conventional jackets, there’s axial [downward] transfer of loading, allowing for more efficient use of soil strengths and ultimately rendering the whole foundation very strong and durable.” Mechling points out that two twisted jacket foundations installed on ExxonMobil’s oil field in the Gulf of Mexico survived Hurricane Katrina — which devastated New Orleans in 2005 — without incurring structural damage. “[This was] hugely significant in terms of demonstrating design robustness,” he says. Though still an emerging technology, floating wind turbines are seen by some as a better solution than fixed foundations in hurricane- and earthquake-prone regions. French outfit Ideol’s open-centred “damping pool” substructure design has already received certification for extreme conditions from Japan’s ClassNK.“Tsunamis from earthquakes don’t seem to present a significant risk to floaters as they just ride them out,” says Ideol chief sales and marketing officer Bruno Geschier. “The largest waves present far closer to shore than where we’re likely to be installing; and even exceptional rogue waves further out are ably overcome.”Some risks do extend to floating foundations, particularly related to electrical cables and mooring to the seabed, which could be affected by soil liquefaction and strong currents. But Geschier says that these components meet all requirements and have been subjected to “lengthy hydrodynamic simulations” that take site-specific data into account. There is also a concern that building in robustness to natural disasters incurs extra expense — and so exposes the new, risk-prone markets to sustained higher costs. But research by the NREL shows that resilience can be delivered cost-effectively, without compromising turbine efficiency (see panel). And as Mechling points out: “More robust design could add expense, but when that hurricane comes around, you want the assurance that you’ve built in adequate safety margins. A few more tons of steel or concrete are worth it when you consider the alternative, potentially catastrophic consequences for the wind farm.” Kimon Argyriadis, innovation manager at DNV GL tells Recharge: “I’m confident that the industry can cope with the challenges [of hurricanes and earthquakes] — just as they have with extreme cold climates. There are additional efforts required and considerations to be made. But it’s nothing that’s unsolvable.”


Hahn H.,Fraunhofer Institute for Wind Energy and Energy System Technology | Krautkremer B.,Fraunhofer Institute for Wind Energy and Energy System Technology | Hartmann K.,University of Applied Sciences Aschaffenburg | Wachendorf M.,University of Kassel
Renewable and Sustainable Energy Reviews | Year: 2014

The share of electricity produced from renewable energy is constantly increasing in Germany and worldwide. The transformation to an electricity system based on renewable sources is characterised by an increasing need for balancing power in order to compensate power supply from fluctuating sources, such as solar or wind. Biomass, more precisely energy from biogas, has the potential to generate electricity flexible on-demand. A demand-driven biogas production is vital for balancing power generation and can generally be achieved by biogas storing or flexible biogas production concepts. This study analyses and reviews both concepts regarding their ability to facilitate a biogas supply for short-term and long-term balancing power generation. Results show that a demand-driven biogas supply based on a biogas storing concept is, due to the fast availability of biogas (i.e. biomethane), suitable for the generation of positive secondary and tertiary balancing power. Whereas, long-term balancing power can be provided by flexible biogas production as well as by biomethane, which was injected and stored in the natural gas grid. Basically all reviewed biogas supply concepts that facilitate a shutdown of electricity generation by storing or stopping the biogas production can additionally provide negative balancing power. © 2013 Published by Elsevier Ltd.


Von Appen J.,Fraunhofer Institute for Wind Energy and Energy System Technology | Stetz T.,Fraunhofer Institute for Wind Energy and Energy System Technology | Braun M.,Fraunhofer Institute for Wind Energy and Energy System Technology | Schmiegel A.,Robert Bosch GmbH
IEEE Transactions on Smart Grid | Year: 2014

Local PV storage systems are emerging in Germany as PV feed-in tariffs have dropped below electricity prices for households. These PV storage systems provide the opportunity to increase the local consumption of locally generated PV energy. The so called self-consumption does not imply an explicit benefit for highly PV penetrated distribution grids suffering PV related voltage rises. Hence, this paper introduces several local voltage control strategies using PV storage systems. These strategies focus on adding a voltage control capability to self-consumption strategies through a combination of voltage dependent battery charging, automatic reactive power provision as well as PV power curtailment. Their potential to smooth the grid integration of PV while increasing self-consumption is assessed through grid simulations and an economic evaluation. In conclusion, PV storage systems which are capable of voltage control can improve PV grid integration and provide a benefit to storage system owners. © 2014 IEEE.


Stetz T.,Fraunhofer Institute for Wind Energy and Energy System Technology | Marten F.,University of Stuttgart | Braun M.,Fraunhofer Institute for Wind Energy and Energy System Technology
IEEE Transactions on Sustainable Energy | Year: 2013

This work discusses the technical and economical benefits of different active and reactive power control strategies for grid-connected photovoltaic systems in Germany. The aim of these control strategies is to limit the voltage rise, caused by a high local photovoltaic power feed-in and hence allow additional photovoltaic capacity to be connected to the mains. Autonomous inverter control strategies, which do not require any kind of data communication between the inverter and its environment, as well as an on-load tap changer for distribution transformers, is investigated. The technical and economical assessment of these strategies is derived from 12-month root mean square (rms) simulations, which are based on a real low voltage grid and measured dc power generation values. The results show that the provision of reactive power is an especially effective way to increase the hosting capacity of a low voltage grid for photovoltaic systems. © 2010-2012 IEEE.


News Article | December 4, 2015
Site: cleantechnica.com

Offshore wind developers will now be able to gather greater data from potential wind sites thanks to a new offshore wind measurement buoy. Researchers from the Fraunhofer Institute for Wind Energy and Energy System Technology (IWES) in Germany have developed a new wind measurement buoy packed “with sophisticated, precise measurement technology” which is able to provide offshore wind developers with the necessary data they need to determine the profitability of a potential offshore wind project. “Constant high wind speeds at sea can offset the huge investment costs for building the farms and connecting them to the grid,” said Claudia Rudolph, scientist at the Fraunhofer Institute for Wind Energy and Energy System Technology in Bremerhaven. “The profitability of wind farms comes from the difference between feed-in compensation and the costs for construction and maintenance.” The new measurement buoy uses a LiDAR (Light Detection and Ranging) measuring device built into the buoy that measures wind speeds at heights between 40 and 200 meters — perfect for determining the suitability of a location for an offshore wind farm. “LiDAR systems send pulsed laser beams into the atmosphere, which reflect off of aerosol particles in the air,” explains Rudolph. “From the frequency shift of the backscattered signal, the wind speed and direction are calculated at the corresponding measurement heights.” With more precise and comprehensive data, wind energy developers can get a better picture of a locale’s suitability to provide continual wind energy. And though LiDAR technology was originally thought to be too imprecise for offshore applications, researchers from IWES built a corrective algorithm that erases the buoy’s own movement from the data it provides. The new measurement buoy has provided data with a 99.7% correlation with traditional met mast data. “Out in deep water, the LiDAR buoy is a genuine alternative to wind met masts, which measure wind speeds only at a height of 100 meters,” says Rudolph.    Get CleanTechnica’s 1st (completely free) electric car report → “Electric Cars: What Early Adopters & First Followers Want.”   Come attend CleanTechnica’s 1st “Cleantech Revolution Tour” event → in Berlin, Germany, April 9–10.   Keep up to date with all the hottest cleantech news by subscribing to our (free) cleantech newsletter, or keep an eye on sector-specific news by getting our (also free) solar energy newsletter, electric vehicle newsletter, or wind energy newsletter.  


News Article | December 1, 2015
Site: phys.org

Planners of offshore wind farms need to know which way the wind is blowing, as their profitability depends on wind speeds. "Constant high wind speeds at sea can offset the huge investment costs for building the farms and connecting them to the grid. The profitability of wind farms comes from the difference between feed-in compensation and the costs for construction and maintenance," says Claudia Rudolph, scientist at the Fraunhofer Institute for Wind Energy and Energy System Technology IWES in Bremerhaven. Using a special wind measurement buoy, the meteorologist and her team want to calculate the wind potential and therefore the energy yields that can be expected, thus providing valuable support to wind farm planners. For this endeavor, the researchers rely on LiDAR (Light Detection and Ranging) technology. The design of the Fraunhofer IWES LiDAR buoy is based on the light buoys that have been used in the North Sea for over thirty years, which the scientists have adapted to measure wind potential. It is over eight meters in length, has a diameter of 2.55 meters and weights 4.9 tons. The buoy carries a LiDAR measuring device that measures wind speeds at heights of between 40 and 200 meters. "LiDAR systems send pulsed laser beams into the atmosphere, which reflect off of aerosol particles in the air. From the frequency shift of the backscattered signal, the wind speed and direction are calculated at the corresponding measurement heights," explains Rudolph. Although the technology is already used on land, it was previously considered unsuitable for measurements on buoys and floating platforms because it was too imprecise. The buoy's own movement, which distorts the measured values, prevented the reliable use of a LiDAR device. To allow these measurements to be carried out on moving structures, the IWES researchers developed a correction algorithm that subtracts the buoy's own movement from the measurement values. The new floating LiDAR system guarantees high measuring accuracy, comparable to the results obtained by fixed offshore wind met masts. This was the conclusion of validation measurements carried out in the North Sea, where the buoy was installed at a location with a water depth of 30 meters at the Alpha Ventus offshore farm 45 kilometers off the coast of the island of Borkum, near the FINO 1 wind met mast. There was a 99.7 percent correlation between the values from the met mast and those from the buoy. "Out in deep water, the LiDAR buoy is a genuine alternative to wind met masts, which measure wind speeds only at a height of 100 meters," says Rudolph. Another advantage of the system is that the flexible buoy can be used anywhere at sea and is quick to install, making the costs five to ten times lower. The buoys are also much easier and cheaper to maintain than wind met masts. Depending on individual requirements, the system can also measure additional parameters such as waves, currents and temperatures at the same time. Another of the buoy's noteworthy features is the aluminum housing that encapsulates the LiDAR measuring device and protects it against salt water and the extreme environmental conditions at sea. The housing contains special glass through which the laser beam passes unhindered and unbroken into the atmosphere. An autonomous power supply system completes the package: three small 400-watt wind generators and three 70-watt solar panels generate the electricity, while three gel batteries store it. This ensures that reserve energy is available for a week without wind and sun. Inside the floating platform there is a computer for data communication. Status and measurement data are transmitted to the recipient via WLAN or satellite. A LiDAR buoy is currently being used in a research project off the coast of Denmark, while a further buoy will be used for demonstration measurements in the North Sea. Through this project, the scientists aim to present their development to the Offshore Wind Accelerator (OWA) consortium brought together by the Carbon Trust, a nonprofit organization whose mission is to promote the transition to a climate-friendly economy. "If you fulfill the OWA's criteria, you are awarded pre-commercial status, which sends an important signal to our potential customers. It shows that our system is fully operational, and enables us to approach wind farm planners and operators with various offers such as long-term measurements for yield forecasting and online wind measurements during installation," says Rudolph.


News Article | November 11, 2016
Site: phys.org

How can the enormous amounts of electricity generated through offshore wind power be temporarily stored on site? Until now there was no answer to this question. After several years' research work, the StEnSea project (Stored Energy in the Sea) funded by the Federal Ministry for Economic Affairs and Energy is now entering the test phase. In the framework of this project, IWES, the Fraunhofer institute in Kassel specialized in energy system technology, is now developing to application level the "marine egg" invented by two physics professors at Goethe University Frankfurt and Saarland University in Saarbrücken. A model on the scale of 1:10 with a diameter of about three meters was brought to the ferry terminal in Constance on 8.11.2016 and lowered on 9.11.2016 to a depth of 100 meters about 200 meters from the shore in Überlingen. It will now be tested for four weeks: "Pumped storage power plants installed on the seabed can use the high water pressure in very deep water to store electrical energy with the aid of hollow spheres", explains Horst Schmidt-Böcking, emeritus professor at Goethe University Frankfurt. To store energy water is pumped out of the sphere using an electric pump and to generate power water flows through a turbine into the empty sphere and produces electrical energy via a generator. Together with his colleague Dr. Gerhard Luther from Saarland University, Professor Schmidt-Böcking filed a patent for their principle for offshore energy storage in 2011, just a few days before the Fukushima disaster. The two inventors remember: "The rapid practical realization of our idea is actually thanks to a newspaper article in the FAZ. Georg Küffner, the technology editor, presented our idea for energy storage to the general public - as chance would have it on the 1st of April 2011. Lots of readers doubtlessly thought at first that it was an April Fool hoax, but experts at Hochtief Solutions AG in Frankfurt immediately recognized the idea's hidden possibilities. Within a couple of weeks we were able to set up a consortium for an initial feasibility study with Hochtief's specialists for concrete structures and the experts in marine power and energy storage at IWES in Kassel, the Fraunhofer Institute for Wind Energy and Energy System Technology", recall Schmidt-Böcking and Luther. Once the concept's feasibility had been proven, the Federal Ministry for Economic Affairs and Energy subsequently funded the StEnSea project so that the innovative pumped storage system could be further developed and tested on a model scale. It is now entering the test phase. Project Manager Matthias Puchta from Fraunhofer IWES summarizes the project's successes to date: "On the basis of our preliminary study, we carried out a detailed systems analysis with a design, construction and logistics concept for the pressure tank, developed a turbine-pump unit, examined how to connect the sphere to the electricity grid, calculated profitability and drew up a roadmap for the system's technical implementation." He continues: "The four-week model trials on the scale of 1:10 are starting now in Lake Constance. We will run various tests to check all the details concerning design, installation, configuration of the drivetrain and the electrical system, operation and control, condition monitoring as well as dynamic modeling and simulation of the system as a whole." IWES Head of Division Jochen Bard, who has been involved in marine power research for many years at both national and international level, explains: "With the results from the model trials, we want first of all to look more closely at suitable sites for a demonstration project in Europe. We are aiming at a sphere diameter of 30 meters for the demonstration-scale system. At the moment that's the most practical size in terms of engineering. What's already certain is that the system can only be used economically in the sea at depths of about 600-800 meters upwards. Storage capacity with the same volume increases linearly with the depth of the water and at 700 meters is about 20 megawatt hours (MWh) for a 30 m sphere." He continues: "There is great potential for the use of marine pumped storage systems in coastal areas, in particular near the coast in highly populated regions too, for example in Norway (Norwegian Trench). But Spain, the USA and Japan also have great potential. With a storage capacity of 20 MWh per sphere and standard technology available today, we can envisage a total electricity storage capacity of 893.000 MWh worldwide. This would make an important and inexpensive contribution to compensating fluctuations in electricity generation from wind and solar power."


News Article | November 11, 2016
Site: www.eurekalert.org

After several years' research work, the StEnSea project (Stored Energy in the Sea) funded by the Federal Ministry for Economic Affairs and Energy is now entering the test phase. In the framework of this project, IWES, the Fraunhofer institute in Kassel specialized in energy system technology, is now developing to application level the "marine egg" invented by two physics professors at Goethe University Frankfurt and Saarland University in Saarbrücken. A model on the scale of 1:10 with a diameter of about three meters was brought to the ferry terminal in Constance on 8.11.2016 and lowered on 9.11.2016 to a depth of 100 meters about 200 meters from the shore in Überlingen. It will now be tested for four weeks: "Pumped storage power plants installed on the seabed can use the high water pressure in very deep water to store electrical energy with the aid of hollow spheres", explains Horst Schmidt-Böcking, emeritus professor at Goethe University Frankfurt. To store energy water is pumped out of the sphere using an electric pump and to generate power water flows through a turbine into the empty sphere and produces electrical energy via a generator. Together with his colleague Dr. Gerhard Luther from Saarland University, Professor Schmidt-Böcking filed a patent for their principle for offshore energy storage in 2011, just a few days before the Fukushima disaster. The two inventors remember: "The rapid practical realization of our idea is actually thanks to a newspaper article in the FAZ. Georg Küffner, the technology editor, presented our idea for energy storage to the general public - as chance would have it on the 1st of April 2011. Lots of readers doubtlessly thought at first that it was an April Fool hoax, but experts at Hochtief Solutions AG in Frankfurt immediately recognized the idea's hidden possibilities. Within a couple of weeks we were able to set up a consortium for an initial feasibility study with Hochtief's specialists for concrete structures and the experts in marine power and energy storage at IWES in Kassel, the Fraunhofer Institute for Wind Energy and Energy System Technology", recall Schmidt-Böcking and Luther. Once the concept's feasibility had been proven, the Federal Ministry for Economic Affairs and Energy subsequently funded the StEnSea project so that the innovative pumped storage system could be further developed and tested on a model scale. It is now entering the test phase. Project Manager Matthias Puchta from Fraunhofer IWES summarizes the project's successes to date: "On the basis of our preliminary study, we carried out a detailed systems analysis with a design, construction and logistics concept for the pressure tank, developed a turbine-pump unit, examined how to connect the sphere to the electricity grid, calculated profitability and drew up a roadmap for the system's technical implementation." He continues: "The four-week model trials on the scale of 1:10 are starting now in Lake Constance. We will run various tests to check all the details concerning design, installation, configuration of the drivetrain and the electrical system, operation and control, condition monitoring as well as dynamic modeling and simulation of the system as a whole." IWES Head of Division Jochen Bard, who has been involved in marine power research for many years at both national and international level, explains: "With the results from the model trials, we want first of all to look more closely at suitable sites for a demonstration project in Europe. We are aiming at a sphere diameter of 30 meters for the demonstration-scale system. At the moment that's the most practical size in terms of engineering. What's already certain is that the system can only be used economically in the sea at depths of about 600-800 meters upwards. Storage capacity with the same volume increases linearly with the depth of the water and at 700 meters is about 20 megawatt hours (MWh) for a 30 m sphere." He continues: "There is great potential for the use of marine pumped storage systems in coastal areas, in particular near the coast in highly populated regions too, for example in Norway (Norwegian Trench). But Spain, the USA and Japan also have great potential. With a storage capacity of 20 MWh per sphere and standard technology available today, we can envisage a total electricity storage capacity of 893.000 MWh worldwide. This would make an important and inexpensive contribution to compensating fluctuations in electricity generation from wind and solar power."

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