Aerodynamic blockage and tip-loss effects in a multi-rotor vertical axis wind turbine system

A novel multi-rotor system (MRS) has been proposed by Peter Jamieson. The design features a column of four 500kW Darrieus H-type vertical axis turbines atop each other, of high aspect ratio (5:1) and 45 degrees out of phase. 24 of these columns will be placed alongside each other, counter-rotating and in groups of four, with structural support between groups and around the whole system.

The system may have many benefits. The out-of-phase VAWTs will smooth the torque experienced. For 96 turbines, only 24 generators will be required. Choosing symmetrical blades will allow VAWT units to rotate either direction simply by fitting upside-down. The counter-rotation will have energy production benefits from wake effects, and reduce the net torque on the overall system. The modular nature will ease production, and allow much of the turbine to continue operating should one turbine fail. Neither local nor global yawing will be present, and the system is expected to be floating on a tri-floater.

The work of this PhD will be on blockage and tip loss effects. A power increase is expected from aerodynamic blockage effects, perhaps enhanced by the rotors of a VAWT passing the wind twice. It should also be enhanced by the support structure causing further flow concentration, as it is in-line with the rotors, rather than behind them like a HAWT MRS. A guideline on how best to optimise power enhancement will be produced.

The high aspect ratio is likely to reduce tip loss significance, however there are additional complexities from the interaction of tip loss vortices from above/beneath and on one/two sides. Time permitting, wake effects may be briefly analysed.

This outward-facing doctoral training centre will create impact through knowledge enhancement and leadership development which will have significant benefit for society, people and the economy.

Societal Impacts:
A very large increase in renewable energy generation, mainly wind, wave and tidal, is expected in the coming years and decades to meet the UK Government and international obligations to reducing greenhouse gas emissions by at least 80 per cent by 2050 when compared to 1990 levels. In particular, the Offshore Wind Industry Council is proposing, under a Sector Deal, to deliver 30GW of offshore wind by 2030 and 50GW by 2050, whilst reducing the average price of electricity by 18%. The longer term societal and economic impacts arise from the difference that the CDT programme and its graduates make to the UK realising this medium-term and longer-term target. The societal impact of meeting these targets, over failing to meet them, can be calculated in avoided CO2, increased sustainability, security and resilience of the energy system in a safe, affordable and environmentally sensitive manner.

People Pipeline and Skills:
There is a widely recognised skills gap in renewable energy both in UK and Europe. Hence, the proposed CDT is timely contributing significantly to meeting the sector's skills demand by the provision of highly trained engineering leaders, expert in a broad range of wind and marine energy technologies and engineering. Most of the CDT graduates will be expected to take up posts in the growing commercial wind and marine energy sectors, and quickly rise to positions of leadership and influence. Some graduates will remain in the higher-education sector and develop academic careers providing much needed increased capacity and capability resulting in a positive impact through an expanded research-base and capability to deal with the inevitable research challenges of the sector as it develops further commercially.

Students will be mentored and encouraged to take a proactive role in creating impact with their research whilst observing Responsible Research and Innovation (RRI). All the Universities participating in this CDT proposal have explicit policies and resources in place to support knowledge exchange and impact and also public engagement. These support the students throughout their studies to engage in broader dialogue and deliberation and to be aware of the potential impacts and implications of their research.

Our CDT students will also engage in outreach activities and impact the wider community through the well-established Professional Engineering Training Scheme (PETS): this scheme is managed and directed by the students and provides opportunities to engage in outreach activities and to work with peers. e.g. PETS runs a schools and colleges programme wherein the students organise visits to schools and colleges to provide information about renewable energy and a basic introduction to the technology involved.

Economic Impact:
The low-carbon and renewable energy sector is estimated to increase five-fold by 2030, potentially bringing two million jobs to the UK. In particular, an ambitious Sector Deal for industry proposed by Government as part of its Clean Growth Strategy could see a total installed capacity of 30 GW of offshore wind by 2030 with the potential to create at least 50,000 jobs across the UK. If achieved, this would be a six fold increase from the current installed capacity and would make offshore wind the largest source of domestic electricity. To ensure resilience, it is also important to retain and develop the leading UK Wave and Tidal position. With the direct and indirect value added to the UK supply and installation chain in terms of job creation, intellectual property exploitation, and sales of wind, wave and tidal technology and services, the proposed CDT will make an important contribution through knowledge enhancement and leadership development.