Are vertical turbines the future of offshore wind energy?
What makes renewable energy so exciting is the immense economic potential of revolutionary technological advancements.
A recent discovery by engineers at the School of Engineering, Computing, and Mathematics at the University of Oxford Brookes could change the design of offshore wind farms forever. The study, led by Professor Iakovos Tzanakis, demonstrates that deepwater and coastal wind turbines could achieve a 15% increase in power output if traditional horizontal axis wind turbines (HAWT) were replaced with a wind turbine design. vertical axis (VAWT). While conventional HAWT windmills produce power with a standard three-bladed “pinwheel” design, VAWT uses a more cylindrical shape with blades rotating around a central shaft.
The main problem with conventional HAWT wind farms – which can have 60 to 70 turbines on 1,500 acres – is that efficiency degrades quickly in the back rows due to turbulence in the first rows of the formation. Vertical axis turbines solve this problem by generating less turbulence and in some cases even improving the efficiency of nearby turbines.
The basis of their research is computational flow analysis using 11,500 hours of computer simulations to optimize placement. They also analyzed the effects of turbulence generated downstream which reduced the rear row efficiency of traditional HAWTs to 25-30%.
This discovery requires further study of condensing wind farms since current turbine designs are intended to be used in a singular application. When installed close to each other, performance characteristics change, reducing the efficiency of surrounding turbines due to the turbulence created downwind. GE’s typical offshore turbine is massive, measuring 220m in diameter and 248m high, and averaging 12-14 MW of electricity, enough to power up to 12,600 homes.
Current US wind turbine capacity is 118 GW or 8.4% of utility-scale power generation. Offshore wind capacity is a meager 42 MW led by the first offshore wind farm in Block Island, RI which is 30 MW – 1 GW is 1000 MW. In addition to the recently announced Vineyard wind project providing 800 MW, the Danish company Orsted has developed two Ocean Wind projects to supply a total of 2.3 GW to the state of New Jersey.
The initial applications of wind turbine technology began in the 1970s with an emphasis on small-scale remote applications, such as research stations disconnected from the power grid. The biggest obstacle in advancing VAWT designs is the lack of proper airfoil shape and issues with brake systems, which result in higher costs. Traditional aerospace applications have provided years of research and a technical basis for the creation of the commonly known “windmill” design. The onshore wind turbine market is dominated by a standard three-rotor HAWT design, but there is no standard design for VAWTs. Recent investments in offshore wind farms, like the Vineyard Wind Project, use a typical three-rotor HAWT design offered by market leader GE in a bedrock-based application that is unsuitable for deep water.
Given the violent and unpredictable conditions of the deep ocean waters, not to mention the weight and center of gravity of a wind turbine, it’s understandable that the technology required to mount a floating turbine was only recently created. A proposed solution was designed by Sandia’s national laboratory, in partnership with the Department of Energy and universities nationwide. After conducting Phase 1 research under a $ 4.1 million grant over 5 years, this solution provided insights that included a reduction in level cost of energy (LCOE) through the application of a VAWT design.
Much of Sandia Labs’ initial work was to create simulations of offshore wind projects. Other developments have included improving the design of airfoils and mechanical generators, as well as refining methods to secure a turbine for safe operation in deep water conditions. Research for the project ended in 2014 and was followed by a publication from the Department of Energy in 2017 setting out official design recommendations.
The current solutions in the VAWT market are all geared towards micro-grids and extreme weather applications. They have an inherent advantage in that they are able to perform well in stressful weather environments; the turbines are able to operate even in a typhoon, which can be a lifeline for deep-water infrastructure such as oil wells.
Countries like the UK and Germany are already at the forefront of generating capacity and investments in offshore wind. The British Isles are home to the first 12 MW (megawatt) offshore unit manufactured by GE, the same design being used in the Vineyard Wind project.
British interests lie in coastal sea applications, where conditions are easily managed by the HAWT design proposed by GE. The US project is the Block Island Wind Farm three miles off the coast of Rhode Island, which produces 30 MW from a series of units supplied by GE, enough to power 27,000 homes. Few countries currently use wind power on the high seas, as it can cost twice as much as the coastal alternative on an LCOE basis.
Offshore wind has found a niche application to provide offshore energy. One of the most demanding offshore energy customers is the oil industry, which currently powers the platforms with diesel-electric generators. The typical offshore oil well consumes 20 to 30 cubic meters (5,200 to 8,000 gallons) per day. This specific application allows a high LCOE – such as offshore wind – to be considered competitive.
The recent investments of the Norwegian energy supplier Equinor in the North Sea focus on supplying their oil platforms with offshore wind. The proposed Hywind Tampen project comprises 11 floating HAWTs producing 88 MW, meeting more than 35% of the energy demand for a series of five offshore platforms. The Hywind project is expected to reduce 200,000 tonnes of CO2 emissions per year. Further investment in offshore wind technology could completely eliminate the need for diesel fuel.
In the United States, there have been small-scale projects to test the designs of floating HAWTs. In 2013, a model was installed off the coast of Maine by the DeepCwind Consortium, in partnership with the University of Maine. Seattle-based Principle Power has installed its patented Windfloat design off the west coast of the United States in an offshore application. Principle Power currently has five units in operation and has proven its ability to withstand waves. up to 17 m (55 ft 9 in) and winds of 41 m / s (92 mph).
If the United States chooses to invest more in the development of VAWT floating turbine technology, it could become the world leader in offshore wind power. Once it has overcome the technical barriers created by the materials and mechanical systems, the production capacity of an offshore wind farm is infinitely scalable when the right technology is used. Models such as those created by the Oxford Brookes University team lend credence to the idea of replacing floating oil rigs with wind turbines. The ultimate irony would be for the oil giants to apply their technologies to the high seas to develop the first range of scalable floating turbines for deep sea applications.
With the help of Sean Moroney