109 research outputs found
Acoustics of weirs: Potential implications for micro-hydropower noise.
There is great potential for the expansion of the small or micro scale hydropower network. Of the 43
thousand weirs in the UK there are only 500 consented hydro schemes. Planning applications for such
schemes require a noise assessment. Noise evaluation of a proposed renewable scheme is often
complicated by the turbine sites having distinct noise characteristics in the first instance, which are often
caused by the weirs themselves. Three types of weir were studied: Broad Crest weirs were studied in
detail; this is complimented by further studies in Flat V and Crump weirs. Flow data was collected for ten
sites from the Environment Agency and the National Rivers Flow Archive to assess the collected Sound
Pressure Level (SPL) and calculated Sound poWer Level (SWL) in relation to various river flows. Weir
head height, width and meteorological data were also collected. It has been shown that the SPL data
collection method used was the right choice, as the greatest amplitudes at the water impact interface at
all weir types was recorded. SPL and SWL were found to be within a 36e82 dBz and 45e86 dBz range
respectively for all weir types. These values can be used in computer simulations of sound propagation.
The mean SPL and SWL difference between the weir types are 6.1 dBz and 6.3 dBz. Head height has the
greatest effect on SPLs. Attenuation with distance was found to be similar to that of a free field line source
in general
Strength and ductility demands on wind turbine towers due to earthquake and wind load
In earthquake prone areas, wind and earthquake loads are assumed to be statistically uncorrelated, therefore their interaction is ignored by existing design guidelines. However, the fact that strong earthquake events are commonly followed by aftershocks and that wind is constantly flowing at high speeds around wind farms increase the probability of their joint occurrence, thus making current design assumptions questionable. This investigation shows that multi-hazard scenarios magnify strength demands of wind turbine towers designed against isolated load conditions, hence modifying their performance level. It is also shown that, under certain conditions, the probabilities associated to the joint occurrence of earthquake and low to strong wind events match or exceed those related to the original design, thus rendering wind energy infrastructure susceptible to unforeseen damage
The influence of substrate and vegetation configuration on green roof hydrological performance
A four-year record of rainfall and runoff data from nine different extensive (80 mm substrate) green roof
test beds has been analysed to establish the extent to which the substrate composition and vegetation
treatment affect hydrological performance. The test beds incorporated three different substrate components
with different porosity and moisture retention characteristics, and three different vegetation
treatments (Sedum, Meadow Flower and unvegetated).
Consistent differences were observed, with the vegetated beds showing higher levels of rainfall retention
and better detention compared with unvegetated beds. The seasonal Meadow Flower beds had
similar hydrological performance to Sedum-vegetated beds. There was a 27% performance reduction in
annual volumetric retention attributable to differences in substrate and vegetation. The beds with the
most porous/permeable substrates showed the lowest levels of both retention and detention.
As with previous studies, retention efficiency in all nine beds showed a strong dependency on rainfall
depth (P), with retention typically >80% for events where P < 10 mm, but significantly lower when
P > 10 mm. The effects of vegetation and substrate were most evident for rainfall events where P > 10 mm,
with the mean per-event retention varying between beds from 26.8% to 61.8%. On average, the test beds
were able to retain the first 5 mm of rainfall in 65% of events where P > 5 mm, although this ranged from
29.4% to 70.6% of events depending on configuration. In terms of detention, all but one of the test beds
could achieve runoff control to a green field runoff equivalent of 2 l/s/ha for more than 75% of events.
Detention was also characterised via the calibration of a reservoir-routing modelthatlinked net rainfall
to the measured runoff response. The parameter values identified here – when combined with a suitable
evapotranspiration/retention model – provide a generic mechanism for predicting the runoff response
to a time-series or design rainfall for any unmonitored system with comparable components, permitting
comparison against local regulatory requirements
NERC Ancient Biomolecules Initiative
The Ancient Biomolecules Initiative is a Natural Environment Research Council programme exploring the biomolecular record of past life which is entombed in archaeological and geological deposits. The findings have applications in archaeology, anthropology, forensic science, research into the past climates and oil exploration. This resource consists of a series of leaflets in PDF format which describe the key findings of the Ancient Biomolecules Initiative
NERC strategy for Antarctic research
Available from British Library Document Supply Centre- DSC:GPC/00766 / BLDSC - British Library Document Supply CentreSIGLEGBUnited Kingdo
Our future world Global environmental research
Report to the Advisory Council on Science and Technology by the NERCSIGLEAvailable from British Library Document Supply Centre- DSC:GPC-00196 / BLDSC - British Library Document Supply CentreGBUnited Kingdo
Report of the Institute of Hydrology for 1988/89
6.00SIGLEAvailable from British Library Document Supply Centre- DSC:7520.346(1988/89) / BLDSC - British Library Document Supply CentreGBUnited Kingdo
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