The basic idea of Crestwing was to develop a wave energy converter which:
Utilizes a high percentage of the incoming
energy from the waves
Is efficiently transforming the
absorbed energy into production of electricity
Is safe on the sea
Is able to board and easy to carry out maintenance on
From the beginning of the development of Crestwing the focus has been on gaining as much knowledge and information through onshore tests as possible, because tests offshore are expensive and risky. Crestwing has undergone ongoing development and testing since 2005 and has especially gained information on the internal forces in the mooring, device and PTO at DHI.
Great Belt 2005
The initial tests were conducted in The Great Belt, where Henning Pilgaard himself tested the seaworthiness of the device and, more importantly, whether his theory of the atmospheric pressure could be proven. After the idea was proved for him and those close to the project, the task was to convince outsiders.
The following development projects have been funded by energinet.dk:
Aalborg University (AAU) 2008
Aalborg University AAU is the most experienced university in Denmark regarding testing of maritime structures. AAU participated in 2008-09 with tests of Crestwing for one year and is for the moment involved in the ongoing work with the 1:5 model (The Fladstrand model).
At AAU tests with various weights on the device were carried out. This was to understand how the weight of the device would influence the system.
Test in wavetank at Aalborg university, scale: 1:30
The model was tested with weights in the interval of 17,5 to 40 kg.
The goal was to demonstrate that the system did not only work through Archimedes´ principle of displacement. If the efficiency rose when the pontoons were heavier, it would mean that the atmospheric pressure only had a minor influence on the system. These tests showed that the weight had little to none influence on the efficiency of the device.
The tests showed that Crestwing can achieve an annual efficiency of 40-50% with potential for advancement. For individual waves it was possible to utilize more than 80% of energy.
Compared to the original design, the concept has been developed during the test runs, but the principle of the atmospheric pressure remains central to the functionality of Crestwing.
Danish Hydraulic Institute (DHI) 2010
DHI has 50 years’ experience of working with testing and modeling of marine structures in more than 40 countries. DHI participated in 2010-11 with tests of Crestwing for more than one year.
Load cells and force transducers were mounted in order to measure forces in the hinge, structure, mooring and push rod, as a basis for development and construction of full-scale device. Throughout the test run, the movements of the plant in the six degrees of freedom were measured. The conditions underneath the pontoons were measured to document the vacuum below the device.
At DHI we measured the pressure conditions underneath the pontoons to test if the estimated negative pressure or vacuum below the hinge was present. This was the documentation of the atmospheric pressure ensuring the downward movement of the pontoons. The test was successful and confirmed the theory.
Test in bigger wavetank at DHI, scale 1:15
Throughout the trial, forces in the mooring system were measured. It became clear, that keeping forces low in the mooring system by the use of flexible anchor line is crucial to the efficiency.
These tests gave us the data for building a full scale device.
Frederikshavn is historically a maritime center; they have many shipyards and engine manufacturers, a well-equipped harbor and one of the largest ports in Denmark. Despite of all this Frederikshavn had not been involved in the development of the existing wave energy concepts in Denmark.
Crestwing and Energy City Frederikshavn have since 2009 had an intensive and successful cooperation, with established multidisciplinary collaboration and a number of maritime companies and institutions in North Jutland.
Fladstrandsanlægget in Kattegat scale 1:5, is now on a shipyard
In 2011, carpenter students (and their teacher) of the technical school EUC Nord built a wooden model in size 10x2.5m called the Fladstrand model. This model was in autumn 2011 tested in the ocean close to Frederikshavn for behavior and survival, the model was exposed to several storms and performed well through the two to three months the tests lasted.
During 2012-13 there was built a new PTO and three students from “MARTIC engineer school” have completed their bachelor through building a test bench and doing tests on the PTO. It turned out that the little model has an efficiency about 80%. Since there is bigger resistance in a small model, there was completed calculations of a full-scale PTO and it showed efficient about 90%.
A new anchoring system was in the same period developed and manufactured. The anchor system is currently about 100m south of the naval station, and here Fladstrand has been anchored up (without PTO) through June this year (2014) In September, the entire WEC with PTO will be laid out and there will be testing of the entire system. The tests will be similar to those done at DHI with load cell and measuring the forces and energy production with documentation and data logging to the Internet.
Crestwing Ltd’s current, concrete goal is to design a 1:2 prototype of 10x30 meters that will produce electricity build during 2015 and launched May 2016. The prototype will be placed in Kattegat by Hirsholmene Frederikshavn, and will be closely monitored and tested.
Crestwing has achieved funding from the EU for designing and engineering the prototype.
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