Page 9 - 2014_A_preliminary_energy
P. 9
50 L. de Santoli et al. / Sustainable Energy Technologies and Assessments 8 (2014) 42–56
Fig. 13. Hybrid system configuration. et al. [47], evaluating different types of small wind turbine,
affirmed that vertical axis wind turbines produce lower noise
Noise assessment emissions than horizontal axis ones. In particular, H-rotor, used
in the proposed prototype, is the turbine that generates the lowest
One of the most relevant environmental concerns on wind noise emissions (see Table 8).
energy regards noise emissions [41]. For an exhaustive review on
wind turbine noise see Doolan [42]. The noise level is correlated Clohessy [48], carrying out noise measurement on a vertical
to typologies and sizes of rotor and blade. Obviously, the micro micro turbine with rated electric power 1 kW, obtained similar
wind turbines noise impacts are considerably less than the one results. The results show a noise level measurement lower than
produced by a wind farms. In particular, there are not many 54 dB performed on a distance of 10 meter far to the turbine. The
researches in literature regarding the assessment of micro turbines corresponding wind speed for the assessment was equal to 8 m/s.
noise. The main noise emission assessments were carried out for This noise value is included in the range 50 dB(A) and 60 dB(A),
installations in urban areas or sites close to living and working representing the noise produced by a standard air condition
areas [43–45]. machine (Split) and a washing machine respectively.
Zhu [46] identified two potential types of noise produced by Taylor et al. [45] analyze the noise distribution of a micro tur-
wind turbines: aerodynamic and mechanical noise. The former is bine with a rated electric power 5 kW. The results show that noise
caused by the blade passing through air, whereas the latter is a levels decrease considerable with the distance from the turbine in
consequence of the metal components movements. Eriksson the whole frequency spectrum. In particular, these results show a
maximum equivalent continuous A-weighted sound pressure level
(LAeq) of 45 dB(A) in correspondence with 7 m/s wind speed at a
distance of 15 m from the turbine (Table 9).
In Italy, the limit values of sound sources are disciplined by the
DPCM 14 November 1997 [49]. In Table 10, the limit values estab-
lished for the class ‘protected areas’ expressed by equivalent con-
tinuous A-weighted sound pressure level (Eq. (2)) were reported.
"1 ZT psðtÞ2 #
T ps2o
LAeq ¼ 10 log 0 dt ½dBðAÞ ð2Þ
where:
ps is the acquired sound pressure [Pa];
ps0 is the reference sound pressure [20 lPa];
t is the time [s];
T is the exposure period considered, coinciding with the
daytime or nighttime period [s].
Fig. 14. AM300 prototype foundation.
