Nextbigfuture covered the large wind turbine designs in 2011.
Europe Upwind project has redesigned the turbines and the blades and structure for wind turbines for an economical and feasible design for 20 megawatt wind turbines by 2020. (108 pages
A new turbine design has been developed from work by the pan-European Upwind research project funded by the European Union. The aim of the research was to examine the technical feasibility of building larger turbines that offer increased capacity and so boost renewable energy production. The proposed turbines would have revolving blades with a 800ft diameter and a capacity of 20 megawatts (Mw) compared to the 3Mw of most wind turbines. Currently, the world’s largest wind turbine is manufactured by Enercon and produces 7.5Mw.
UpWind demonstrated that advanced blade designs could alleviate loads by 10%, by using more flexible materials and fore-bending the blades (WP2).
The application of distributed aerodynamic blade control, requiring advanced blade concepts with integrated control features and aerodynamic devices. Fatigue loads could be reduced 20-40% (WP2)
The UpWind project demonstrated that individual pitching of the blades could lower fatigue loads by 20-30%.
Nimrod Energy's Plans Radical Wind Turbines
There is a more radical design which could enable even larger and more efficient wind turbines.
Prof Garvey turbine is dramatically different: a horizontal-axis machine with eight blades — four long and four short. A floating framework replaces the tower, and it converts wind power internally within the blades. Think of a bicycle wheel rotating slowly, and a loose bead on each spoke. The beads represent pistons travelling back and forth inside tubes in the blades, compressing air as they do so.
The baby of the family is a 200 meter-diameter machine producing 18MW in a decent wind and costing less than 40% of the 40 million pounds you’d spend on a corresponding set of direct-generating machines. Her big sisters might easily reach 400 meter in diameter and could be 50% more cost-effective.
Renewable Energy journal - The dynamics of integrated compressed air renewable energy systems
An integrated compressed air renewable energy system is defined here as one which harvests renewable energy directly in the form of compressed air and later converts that to the form of electrical power for transmission. There are two main motivations for considering such systems: firstly the lifetime cost per kW h exported has the potential to be substantially lower than the lifetime cost per kW h of a system generating electricity directly. Secondly these systems offer the intrinsic capability to store large amounts of energy in a very cost effective way. The only marginal costs associated with energy storage are those connected with providing some means for storing the compressed air and some means for managing heat. This paper describes an approach to simulating the performance of such systems including a controller to determine how much power to generate at a given time and it explains an appropriate rationale for the design of that controller. The simulations conducted indicate three remarkable performance measures. Specifically: (a) the marginal loss of energy associated with passing some energy through storage may be below 15% even with energy residency times in the order of months, (b) the marginal increase in total output electrical energy arising from integrating some solar heat capture can be as high as 60% of the captured solar heat for solar heat inputs up to 5% of total mechanical power and (c) the average value of the total power output may easily be raised by over 30% if power values continue to fluctuate at rates exhibited today and if the capacity for expansion-generation matches the peak input power of the primary (mechanical) energy harvesters.
► Offshore renewable energy systems which compress air directly are economically viable.