In cooperation with NKUA
Modern conventional grid-connected wind turbines are intentionally sited away from buildings due to the fact that in an urban area, as compared with an adjacent rural area, the wind speed will be generally lower, the turbulence and wind shear greater and there will be more specific local flow effects. Conditions seem thus unfavourable regarding both power output and turbine lifetime. However, the integration of wind turbines in built areas allows energy to be produced directly close by consumption places, sometimes fed into the client’s electrical circuitry and so avoids the overheads and losses associated with separate connection to the local electrical utility distribution network. The economic value of this energy is then equal to that otherwise charged by the client’s electrical supplier, which is considerably higher than that produced in a remote area.
Figure 55: The wind regime around a building. Left picture: low turbulence. Right picture: high turbulence [LEA08]
Points of attention
There are certain issues that need to be carefully addressed before the mounting or integration of a wind turbine in a building:
Wind regime in the built areas: high turbulence levels in regions of high building density that are generally considered to reduce performance and induce significant stress, leading to reduced life and high maintenance requirements. Computational (for example computational fluid dynamics - CFD) or wind tunnel tests can lead to the understanding of turbulence around a building and thus indicate the proper location of the wind turbines.
Noise: The noise created by a wind turbine may be sufficient to produce adverse reactions in surrounding buildings and in the building where the turbine is mounted. The noise produced by the wind turbine is due to mechanical sounds that originate from mechanical components and the dynamic response among them and aerodynamic sounds that originate from the flow of air around the blades [ROG06]. The latter is typically the largest component of wind turbine acoustic emissions. This can be appropriately handled with the careful selection of turbines with noise ratings appropriate to the noise climate, and careful placement of the turbines to minimise the noise generation [DUT05].
Vibration: steady operation of the wind turbines causes the turbine to vibrate, subsequently creating the potential for the vibration to transmit via the turbine’s supports into the building structure. Apart from the fact that vibration has the potential to cause disturbance to the building’s occupants, long term fatigue damage to the building structure can be produced. Procedures for handing the problem may include: selection of turbine types and sizes according to the type of construction, careful design of the mounting arrangement to minimise rigid connections, and careful positioning of the turbines to avoid wind conditions that intensify disturbing vibrations [DUT05].
In the case of wind turbines integration or mounting in historical buildings, the aesthetic value should be taken into consideration. Thus wind turbines should be visually integrated to the historical heritage of the building. This may prove to be a demanding task, while in some cases could be easily accomplished (i.e. windmills).
The following designs are examples of the technologies being developed for the integration of wind turbines in the in built-up areas.
Developed by University of Strathclyde [DAN99], from a 1979 patent by G.W. Webster, the ducted wind turbine module is designed to be integrated into a conventional high-rise building. This design consists of a 90 degree bent duct, with the inlet in line with the wall face of the building and the outlet on the roof. The turbine rotor is hidden from view, since it is mounted just inside the roof outlet and the drive shaft passes through the duct to a generator housed below.
Figure 56: Ducted wind turbine modules [DUT05]
Turbines are inserted between the roof and an aerofoil mounted above the apex, which, if it includes a PV panel, is called a SolAirfoil [TAY98] [TAY99]. This arrangement would suit nominally bi-direction wind sites since the augmentation depends on the building’s orientation to the wind.
Figure 57: Aeolian Roof wind energy system
This is a version of the Aeolian roof whereby the SolAirfoil™ is orientated horizontally down the side of a building and the turbines sandwiched are in between, as shown in Figure 58.
Figure 58: AeroSolar Tower
The Wind Dam System uses the inherent strength of the building to intercept and collect wind energy. The building has a number of pressure tapings on its surface, which are linked to an internally mounted turbine so there is no visible conventional turbine and thus no visible rotation. The system can be incorporated in a large number of building types and also has considerable retrofit potential [BLA02].
Figure 59: The wind dam prototype
The omnidirectional wind energy capture of Wind Amplified Rotor Platform (WARP™) Tower can be incorporated with buildings, as ‘apex crowning’, and on elevator systems or roof mounted HVAC systems (Figure 60).
Figure 60: The WARP Tower
Conventional turbine designs can be mounted directly onto buildings merely using the building as a form of tower. Whilst many of the turbines are stand-alone, it makes sense to use the building height to access better wind regimes. Examples of building mounted schemes are The Green Building, Temple Bar, Dublin [BLA02], the Plymouth College of Further Education Innovation Building, the Ecopiaza, Shin-Kawa in Tokio, the Royal Institute of British Architects (RIBA) Building [PAL02], The Green Building, Macintosh Mill, Manchester [PAL02].
Non-conventional turbine designs include the V - vertical axis wind turbine that have a one bladed sister turbine, the ‘Sycamore’ (Andrews, Sharpe and Taylor (1995)), the Turby in which the blades are at an angle because of the skewed flow on flat roofs [MER02], The combined augmented technology turbine, the Light Industrial Mill MGx (2002) in which the duct doubles the velocity seen by the turbine which can handle sustained free stream gusts of well over 100 miles per hour, the Yxen in which the design of the horizontal axis turbine is combined with a diffuser for enhanced wind speed resulting in higher energy production at low wind speed, the Neoga that is a Vertical Axis Wind Turbine, designed to be landmark for sustainable energy.
[BLA02] Blanch MJ, (2002), Wind Engineering, 26(3), 125-143
[DAN99] Dannecker R, et al. (1999) “Development of the Building Integrated Ducted Wind Turbine Module”, Proc 1999 21st British Wind Energy Association Annual Conference, Wind Energy, P. Hinson (ed), pp. 141-147, MEP Ltd, London.
[DUT05] Dutton AG, Halliday JA and Blanch MJ. (2005) The feasibility of building-mounted/integrated wind turbines: achieving their potential for carbon emission reductions. Energy Research Unit, CCLRC.
[MER02] Mertens, S. (2002) “Aerodynamic Ef ficiency Prediction of a Wind Turbine Integrated in a Building”, Proc World Wind Energy Conference, Berlin, Germany, 2-6 July 2002.
[PAL02] Palmer S.(2002) “Farrell wins green light for Macintosh Mill”, The A rchitect’s Journal, 24 January 2002.
[ROG06] Rogers A, Manwell JF, Wright S, “Wind turbine acoustic noise: a white paper” Renewable Energy Research Laboratory Department of Mechanical and Industrial Engineering, 2006.
[TAY98] Taylor D. (1998) “Using Buildings to Harness Wind Energy ”, Building Research and Information, 1998, Vol. 26, No. 3, pp. 199-202.
[TAY99] Taylor, D.(1999) “Al technica AeroSolar & Aeolian Roof Wind System, Aeolian SolAir foil”, Derek Taylor, April 1999