ROSEO: Novel Savonious-type BIWT Design based on the Concentration

of Horizontal and Vertical Circulation of Wind on the Edge of Buildings

Oscar Garcia

, Mario del Rio

, Alain Ulazia

, Juan Luis Osa

and Gabriel Ibarra-Berastegi

ROSEO start-up, University of Basque Country (UPV/EHU), Otaola 29, 20600 Eibar, Basque Country, Spain

NI and Fluid Mechanics Department, University of the Basque Country (UPV/EHU), Basque Country, Spain

Mechanical Engineering Department, University of the Basque Country (UPV/EHU), Basque Country, Spain

Keywords:

Building Integrated Wind Turbine, Savonious, ERA-Interim, ERA5, Anemometer, Calibration.

Abstract:

In this paper a new Building Integrated Wind Turbine (BIWT) called ROSEO-BIWT is presented. The

ROSEO-BIWT is installed on the edge of the buildings and it consists of a Savonius wind turbine and two

concentration panels that have the purpose of accelerating the usual horizontal wind together with the vertical

upward air stream on the wall of the building, improving the performance of the wind turbine and also getting

a good architectural integration. We have studied its hypothetical performance and design conﬁguration in a

tall building of Bilbao using wind data from the reanalysis ERA-Interim (European Centre for Medium-Range

Weather Forecasts’ reanalysis), from an anemometer to calibrate the data, and its real small-scale behavior in

a wind tunnel. Promising preliminary results have been obtained, which could suppose an energy production

increment of 20%.

1 INTRODUCTION

In general terms,the market of the small wind tur-

bines is currently growing although the sector of small

wind turbines to be installed in buildings is increas-

ing at a lower speed. According to the World Wind

Energy Association (WWEA) (WWEA, 2016), the

installation of small-wind turbines will increase by

around 12 % annually in the 2015-2020 period. The

good economic proﬁtability of small-wind turbines

and the constant technological advances are the de-

terminant factors that justify the rising of the small-

wind turbines market. On the other hand, in the last

years, more and more research is being focused on

the development of different technologies that help

minimize the buildings energy consumption. This

philosophy is known as nZEB (nearly Zero Energy

Building) (Chastas et al., 2017) and it is included in

the EU 2010/31/CE directive related to energy efﬁ-

ciency in buildings. After 2018 every public building

constructed should consider this regulation and, after

2020, every new building.

The goal is to maximize as much as possible the

energy efﬁciency and reduce the primary energy from

fossil resources so that the required energy demand

may be covered by renewable sources. In this sense,

the mini wind technology, which consist in generat-

ing energy with wind turbines of 100 kW or less to

cover an area smaller than 200 m

, can play a very

interesting role. For this purpose, some technological

challenges are yet to be fully solved such as the vibra-

tions, the generated noise levels and the device’s aes-

thetical and architectonic integration. Many are the

advantages of these devices.

Many are the advantages of these devices:

1. They can work as stand-alone devices thus pro-

viding energy in isolated locations, not connected

to the electric grid;

2. They work in distributed micro-generation mode,

thus minimizing energy losses due to transport

and distribution. These devices generate energy

close to the ﬁnal user thus dramatically reducing

the need of electric infrastructures;

3. Furthermore, it can be combined with photo-

voltaic energy in hybrid installations allowing an

optimal use and management of shared electric

accumulators.

1.1 State of the Art

The recent developments on wind energy in urban

environments have inspired different types of BIWT

projects. For example, in London Strata SE1 is a tall

172

Garcia, O., Rio, M., Ulazia, A., Osa, J. and Ibarra-Berastegi, G.

ROSEO: Novel Savonious-type BIWT Design based on the Concentration of Horizontal and Vertical Circulation of Wind on the Edge of Buildings.

DOI: 10.5220/0007758201720178

In Proceedings of the 8th International Conference on Smart Cities and Green ICT Systems (SMARTGREENS 2019), pages 172-178

ISBN: 978-989-758-373-5

building of 43 ﬂoors that will include 3 wind turbines

with a diameter of 9 meters in the roof of the struc-

ture. These wind turbines would cover the lighting

demand of the building (Bogle, 2011).

On a smaller scale there are a lot of projects that

includes Horizontal Axis Wind Turbines (HAWT) in-

tegrated in the building and also Vertical Axis Wind

Turbines (VAWT). These projects are focused on in-

tegrate wind turbines in existing buildings. So, these

buildings are no previously designed to accelerate

air streams like the World Trade Center of Baharein

(Smith and Killa, 2007) or the mentioned Strata S1

building. According to this post-integration tendency,

building integrated wind turbines are being imple-

mented in strategic locations to capture the acceler-

ation of air streams that is produced because of dif-

ferent shapes. In this sense, the most interesting loca-

tions are the upper and lateral edges of the building,

mainly the ﬁrst one because it is at reasonable dis-

tance from the homes.

Nowadays there are several ongoing projects to

develop an optimal system to harness wind energy

in urban environments. Most of them conclude that

wind turbines that are used in obstacle-free environ-

ments are not adequate for urban environments due

to the turbulent urban ﬂow. For that reason, HAWT

devices, which usually exhibits a good performance

with laminar ﬂows, shows a low performance in ur-

ban environments and also originate high noises of

up to 200 dB within a radius of 500 m (Oerlemans

et al., 2007). Conversely, VAWT plays an important

role, since its performance is not affected by turbulent

ﬂows and tend to be noiseless. Additionally, VAWT

has a lower cut-in speed than HAWT and a larger cut-

off speed, ensuring longer operating time (Manwell

et al., 2010; Dilimulati et al., 2018). Although the

power coefﬁcient is lower, the design is simpler and

the manufacturing process is easier to carry out.

Along these lines, the existing wind energy urban

potential has encouraged the researchers to develop

a propper methodology of wind energy estimation in

urban environments (Arteaga-L

opez et al., 2019). The

use of anemometers at speciﬁc locations can be com-

bined with other advanced computational simulations

between buildings and considering the complex urban

terrain using CFD (Computational Fluid Dynamics).

In this way, the use of reanalysis and meteorological

mesoscale models for wind energy potential estima-

tion, which is well-known offshore and onshore an

developed also by the author (Ulazia et al., 2017b;

Ulazia et al., 2016), can be complemented with dif-

ferent posterior tools.

In this work, we present the design of a Savonious

drag driven turbine integrated in buildings called

ROSEO-BIWT, which has been especially designed

to work in urban environments where the wind is

characterized by its turbulence and it is important

as well to take advantage of low speed air streams.

The germinal project of ROSEO won the ﬁrst award

in the EDP-RENEWABLE UNIVERSITY CHAL-

LENGE 2017 (EDP, 2017), and now the members of

the project have created an university start-up called

ROSEO. Although it is usually used as an vertical axis

turbine, ROSEO-BIWT is formed by a Savonius tur-

bine in a horizontal position and concentration vanes

that accelerates the air streams thanks to the Ven-

turi effect (see Section 2.2). These type of vanes are

usually called PAGV (Power Augmentation Guiding

Vanes) (Chong et al., 2013; Chong et al., 2011; Tong

et al., 2010). It has been also designed to be archi-

tectonically easily integrated. This is the case of the

design proposed by Park et al. (Park et al., 2015), in

which several Suetonius turbines are implemented in

the facade of the building at different heights to take

advance of the vertical currents created by the wind

on the walls of the building (Figure 1):

Figure 1: Savonious turbines with PAGVs proposed by Park

et al. (Park et al., 2015).

The Savonius wind turbine is a drag-based de-

vice, unlike the majority of turbines, that are lift-

based. This particular aspect allows producing low

noise levels and few vibrations, which is very impor-

tant in building installations (Zemamou et al., 2017;

Kim and Cheong, 2015). The PAGV increases the

wind speed as the catching area is bigger, giving as a

result a system that is able to start with wind speeds

of, about, 1 m/s, which ensures a great number of en-

ergy producing hours. Furthermore, energy continues

being generated no matter how high the wind speed

is.

This paper proceeds as follows: a possible lo-

cation for the installation has been studied by us-

ing ERA-Interim and ERA5 data, a powerful tool for

global atmospheric analysis that is updated in real

time (see Section on Data and Methodology (Section

2.1). The authors have installed also an anemome-

ter in the roof of their university to calibrate wind

data with a period of six months against ERA-Interim

ROSEO: Novel Savonious-type BIWT Design based on the Concentration of Horizontal and Vertical Circulation of Wind on the Edge of

Buildings

173

or ERA5 (Section 2.1.2 ). In this way, an empirical

method for the estimation of wind energy potential

on buildings will be developed, with low computa-

tional cost 3.2. Finally, a preliminary small-scale ex-

periment has been developed in a wind tunnel with

a small Savonious and different disposition of the

PAGV (Section 2.2 and 2.3 ). The authors ﬁnish this

work with some relevant conclusions and the possible

research lines within a future outlook. The qualitative

methodology used here can be considered within the

scope of analogical reasoning and model construction

(Ulazia, 2016).

2 DATA AND METHODOLOGY

2.1 Data and Location

2.1.1 ERA-Interim

A tall building in Bilbao has been selected (longitude:

2.946

◦

W ; latitude: 43.258

◦

N) for the representa-

tion of the integration of the design and to present a

method for the preliminary estimation of the energy

production. Figure 2 shows the top view of the build-

ing and the space of 12 m in the roof where our pro-

totype can be installed.

Figure 2: Selected building in Bilbao.

For the approximate estimation of the wind

statistics data from ERA-Interim have been used.

ERA-Interim is a reanalysis from the global atmo-

spheric data sets provided by the European Cen-

ter for Medium-Range Weather Forecasts (ECMWF)

(Berrisford et al., 2009). It is continuously updated

once per month, and contains data from 1979. The

spatial resolution is approximately 75 km and time

output is achieved every 6 hours. Zonal and merid-

ional components of the wind (U and V) can be down-

loaded at 10 m height.

2.1.2 Anemometer and Calibration

A cup anemometer has been installed in one of the

buildings of the University of Basque Country in

Eibar (see Figure 3) to develop a preliminary calibra-

tion methodology based on quantile-matching tech-

niques used previously by the authors in wind energy

and wave energy(Ulazia et al., 2017a; Penalba et al.,

2018; Ulazia et al., 2018). For this paper the authors

will obtain 8 months of 10-minute data series, which

should be ﬁltered every 6 hourly to match the ERA-

Interim data series or the new ERA5 reanalysis (1-

hourly time resolution in this case) (Olauson, 2018).

Having the average wind speed U after calibration on

the corresponding facade and considering the typical

form parameter in the Rayleigh distribution (k=2), the

corresponding scale parameter can be obtained:

c = U/Γ(1 + 1/k). (1)

In this way, the cumulative distribution function

and the fraction of time between two wind speeds is

determined:

F(U) = 1 − exp(−(U/c)

) (2)

and the augment factor of the PAVG can be imple-

mented in the c parameter (Manwell et al., 2010).

Figure 3: Anemometer on the roof of the building.

2.2 ROSEO-BIWT Design

2.2.1 The Location on the Upper Edge of the

Building

The effect of the wind against buildings have been

largely studied by the sector of architecture with the

purpose of study the dynamic loads generated by air

streams. Because of that, there is a large knowl-

edge about the behavior of wind in urban environ-

ments. Through scale experiments and also CFD sim-

ulations, similar to the Figure 4 generated using CFD

by (Mertens, 2006).

Most of the studies that have analyzed the behav-

ior of the air streams around the buildings agree in

the great potential of the upper edge of the windward

face of the building. It happens because the wind

have to surround an object. The effect is even more

intense when the building is taller and also when the

SMARTGREENS 2019 - 8th International Conference on Smart Cities and Green ICT Systems

174

Figure 4: CFD image where the acceleration in the wind-

ward upper edge can be appreciated (Mertens, 2006).

wind direction is perpendicular to the building facade.

For example, in a 5-stor building the wind velocity

increases 1.2 times in the windward edge (Mertens,

2006).

2.2.2 Savonious Turbine

That is why our ROSEO-BIWT’s Savonious axis is

positioned horizontally along the superior edge on the

building. There are several recent studies about the

performance of the Savonius turbine. Mohamed et

al. (Mohamed et al., 2010) have improved the perfor-

mance using plates to eliminate the negative torque in

the returning blade. They have carried out tests for a

two bladed and for a three bladed wind turbine and

in both cases they have improved the C

of the wind

turbine until a 27 %, being the 15% the typical value.

Apart from these intrinsic improvements, some

engineers have developed the mentioned PAGV sys-

tems to accelerate the air streams. Shikha et al.

(Bhatti et al., 2003) increased 3.7 times the wind

speed in a experimental way using a speciﬁc well-

studied nozzle. Additionally, Altan et al. (Altan and

Atılgan, 2012) have studied the inﬂuence of the in-

clination angle of the plates and its length. In these

experiments they found out that when the longitude

of the PAGV increases the power also increases. So

the important consideration here is the relationship

between the diameter of the rotor and the length of

the PAGV. They even obtained a C

of 38.5 %. Other

types of PAGVs called omni-directional reached a C

of 48%, implying an increase of 240% in relation to a

Savonius rotor without a PAGV system.

In terms of longitude and diameter, (Roy and

Saha, 2013) shows that the best performance of a

Savonius rotor is reached with a Length/Diameter ra-

tio of 6:1. In the same way, Park et al. (Park et al.,

2015) tested different kind of Savonius rotors and they

discovered that the best design was a 6 bladed rotor.

Therefore, for our purpose, a similar rotor with these

proportions is chosen.

2.2.3 The Final Design

Park et al. (Park et al., 2015) developed the idea of us-

ing a bigger surface of the facade to generate energy

installing a lot of Savonius rotors at different heights,

and also using PAGV to improve the performance of

the wind turbines. The system that they propose is

similar to a ventilated facade and it is important to

emphasize that they want to capture the vertical air

streams that are generated on the windward side of the

building, as in our case. However, they use parallel

vanes in the facade, with a small concentration angle,

and our case the upper edge is used augmenting the

concentration angle and capturing also the horizon-

tal component of the wind, and not only the vertical

stream on the facade. Furthermore, the background

of the Savonious rotor is free in the edge of the build-

ing, an important aspect that is not met by turbines

installed in the facade. Although the inﬂuence of this

aspect is out of the scope of this study, it is an obvious

aerodynamic advantage.

Another innovation that we include is that it can be

installed in existing buildings: it is not a design only

for new buildings. To sum up, ROSEO-BIWT shows

a good architectural integration in existing buildings,

with high economical viability due to the simplicity

of the design.

Figure 5 shows this design of the ROSEO-BIWT

viewed from above and from below. This is a

schematic perspective which does not take into ac-

count the inﬂuence of the angle between the two

PAGVs.

Figure 5: ROSEO-BIWT design.

Figure 6 shows the schematic proﬁle of the instal-

lation with the appropriate measures for the building

of Bilbao. The areal ratio of the PAGV between the

entrance and the exit of the air is 4:1, expecting an

analog augment of wind speed due to the Venturi ef-

fect. In any case, the upper vane is adjustable, and its

angle can be changed up to a horizontal position, to

ROSEO: Novel Savonious-type BIWT Design based on the Concentration of Horizontal and Vertical Circulation of Wind on the Edge of

Buildings

175

capture the free wind speed.

Figure 6: Schematic proﬁle of the design.

2.3 Experiments in the Wind Tunnel

Although there are results provided by previous stud-

ies, in the following sections the authors describe the

general experimental methodology that will be devel-

oped in the future. The model construction is pro-

posed in analogy to previous ﬁndings and design pro-

cedures (Ulazia, 2016). These are the main steps:

1. First, the augment factor of the wind speed on the

edge of the building should be empirically stud-

ied: this occurs due to the union of the horizontal

usual component and the vertical component.

2. Then, the previous augment factor should be mul-

tiplied by the new augment factor provided by the

PAGVs. These factors will be measured for dif-

ferent wind speeds in the wind tunnel of the uni-

versity using a scale model of a building.

3. The power curve of a longitudinal section of the

Savonious prototype will be also measured in the

tunnel.

4. Finally, the Weibull distribution at the location

obtained by the previously described calibration

methodology will be implemented on the mea-

sured power curve considering also the augment

factors.

Figure 7 shows the wind tunnel and the installa-

tion of PAVGs and a Savonious rotor. The measure-

ment of the wind speed at speciﬁc points via a Pitot

tube shows an augment between 3-4 in the conver-

gence center of the structure, corroborating the aug-

ment factors obtained in previous studies (Wong et al.,

2017), or even more due to the corner effect of our

design. However, until now, these preliminary mea-

surements have been only performed with few values

of steady wind speed without considering important

effects such as the blockage ratio of the tunnel.

Figure 7: The Savonious turbine inside the wind tunnel with

the PAVGs around.

3 RESULTS

3.1 Wind Rose Around the Building

The ERA-Interim grid around Bilbao city is shown

in the Figure 8 with the points in yellow color. The

nearest ones are marked by the numbers in consecu-

tive rows, and the location of the selected building is

marked in red color. The nearest gridpoint, number

15 at 6 km distance, has been chosen to download the

data (period 2001-2005, that is, 7304 cases 6-hourly).

Figure 8: Nearest ERA-Interim gridpoints (yellow) around

the study point (red).

These data should be raised to the height of the

building (45 m) using the log law and the roughness

of urban environments (Manwell et al., 2010). Ac-

cording to usual considerations in wind energy sector,

the roughness (z

) of the urban terrain is around 1 m.

Roughness is used to apply the logarithmic law of ver-

tical wind shear,

U(z)

U(z

)

Ln(z/z

)

Ln(z

)

, (3)

obtaining wind speed at 45 m height, U (z = 45), in

terms of the speed of reference U (z

= 10).

After the application of the log law, a wind rose

can be plotted in our location using the time series

SMARTGREENS 2019 - 8th International Conference on Smart Cities and Green ICT Systems

176

of U and V. We have represented it around the build-

ing in the Figure 9, visualizing the predominant wind-

ward facade of the building towards the Northwest as

expected according to the climatology of the Gulf of

Biscay. This method offers a ﬁrst estimation of the

wind statistics on the edge of the building, because

the height of the building guarantees that street-level

ﬂows are negligible.

Figure 9: Wind rose according to ERA-Interim around the

building.

3.2 Estimation of the Energy

Production

We have used previously described concepts and val-

ues to estimate the energy production according to

these suppositions:

• According to (Mertens, 2006), the wind incre-

ments its velocity a 20% at the upper edge of a

typical building.

• The simplest PAGVs have increased the wind

speed 3.7 times, with corresponding increments

in C

that can reach a value of 0.37 (Wong et al.,

2017). Although higher values can be obtained

with wider entrances, we will use a low factor of

augment of 4 for our estimation, since we have

also the 20% due to the other architectonic accel-

eration in the upper edge.

• Taking into account the wind rose of Figure 9,

we have only considered the wind data of ERA-

Interim with this direction and also with our tur-

bine in the corresponding facade.

For the estimation of generated power a commer-

cial Savonious model (SeaHawk-PACWIND) is used.

Its rated power is of 1.1 kW, the rated wind speed of

17.9 m/s, the cut-in wind speed of 3.1 m/s, the cut-

off without a given limit being a drag device, and the

swept area is of 0.92 m

(SeaHawk, 2017). If the

pure ERA-Interim wind speed distribution is consid-

ered on the best facade and the average values given

by the calibration (around 5-6 m/s), the turbine would

be working 1600 hours per year in the interval of rated

wind speed: an AEP of around 1700 kWh. However,

using a typical Weibull distribution with k=2, an aug-

ment factor of 4 via PAGVs would produce an incre-

ment of 20% in AEP and working hours (Equations 1

and 2).

4 CONCLUSIONS AND FUTURE

OUTLOOK

In the future, the AEP increment of 20% via PAVGs

in the edge of the buildings must be shown using a

real prototype of ROSEO-BIWT. For that, the build-

ing in the city of Eibar will be used within the Bizia

Lab project of the University of Basque Country. The

anemometer has been installed on the same roof and

having the new data provided by ERA5 in the near-

est gridpoint, the identiﬁcation of the best facade and

the corresponding wind distribution will be obtained

following the methodology described in this paper.

These preliminary results and the methodological dis-

cussion developed until now encourages us for the fu-

ture reﬁnement of ROSEO-BIWT.

For that, the novel validation method for

anemometers developed by the authors in a recent

study for wind farms (Rabanal et al., 2018) will be

very beneﬁcial, since it allows to compare and com-

bine the data of more than one anemometer installed

on the roof of the building.

ACKNOWLEDGMENTS

The research leading to these results was carried out

in the framework of the Programme Campus Bizia

Lab EHU (Campus Living Lab) with a ﬁnancial

grant from the Ofﬁce of Sustainability of the Vice-

Chancellorship for Innovation, Social Outreach and

Cultural Activities of the University of the Basque

Country (UPV/EHU). This programme is supported

by the Basque Government. We acknowledge also

the availability given by the School of Engineering

of Gipuzkoa-Eibar in the University of Basque Coun-

try, the EDP-Renewable awards in which we obtained

the main award in September 2017, the Youth Enter-

prise Grant of UPV/EHU, and the project GIU17/02

of EHU/UPV. All the computations and representa-

tions of this work has been developed using the pro-

gramming language R (Venables et al., 2018).

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