The protection of birds is often cited as one of the main arguments against the expansion of wind energy. While the fact that birds can collide with wind turbines cannot be disputed, the actual number of such collisions is not well known.
O
n their way towarm-er climates or nesting sites, migrating birds are likely to encounter numerous wind turbines. In view of this, it is important to under-stand the correlation between mi-gration intensity and the number of collisions with wind turbines
in order to define corresponding countermeasures.. However, there are no studies at all that set out to calculate how many birds pass by a given location, and simultaneous-ly record the number of birds killed there as the result of collisions with wind turbines. A science-based study involving three wind
tur-bines located in the municipality of Peuchapatte in the canton of Jura aims to help close this knowl-edge gap. In parallel to the search for birds killed as the result of col-lisions, the study uses permanent radar surveys to determine the in-tensity of bird migration.
Transects in the snow in a radius of 100 metres around a wind turbine at the Peuchapatte plant, which were used for carrying out searches for collision victims
One of the problems associated with the search for victims on the ground (birds and bats) is that not all of them can in fact be found.
On one hand, the probability of finding a collision victim depends on the conditions of the terrain (e.g. height and density of veg-etation), the size of the cadaver, the intensity of the search and the skills of the searchers. On the oth-er hand, an unknown numboth-er of collision victims disappear natu-rally (scavengers, decomposition), which depends on a variety of fac-tors such as temperature and hu-midity. This means that studies aimed at determining the num-ber of collision victims always have to define the discovery probabili-ty and disappearance rates under a range of conditions, and take
these into account when making their analyses. Obtaining this addi-tional information requires system-atic experiments involving the con-trolled placement of cadavers. The lower the probability of finding a cadaver, the greater the inaccuracy of the calculation of the effective number of collision victims.
With the objective to achieve the highest possible probability rate for the discovery of collision victims, a high frequency of searches in a very confined area was specified for the Peuchapatte study. Search-es for collision victims were car-ried out in the vicinity of each of the three wind turbines on average every three days between March and November 2015. The searches were carried out in a radius of 50
to 100 metres along parallel lines 5 metres apart from one another.
At the same time, every two weeks a number of bird and field mouse (as a substitute for bats) cadavers were placed around the site in or-der to find out how long they re-mained there. In addition, in the course of the study, test cadavers and dummies of bats were placed on the ground, without the knowl-edge of the searchers, in order to determine the degree of efficien-cy of the searches. Some of the ca-davers were placed in the vicinity of camera traps in order to inves-tigate what happens to them on site. The recorded data are current-ly being anacurrent-lysed, and the results will shortly be published on the www.energy-research.ch website.
Janine Aschwanden
fox prowling in the immediate vicinity of a wind turbine during the night. The images were shot with the aid of a camera trap.
In BRIEf ...
Biogasplant of Biopower nordwestschweiz AG in pratteln (BL).
At the federal Institute of Technology, zurich, a new low-cost method for the solar thermal degasification of hydraulic circuits was developed and patented. Its feasibility was demonstrated on a test bench set up specifically for this purpose.
similar to the estimated level, and that an extrapolation factor of 0.9 can be proposed. Thus it appears reasonable to estimate the level of methane production of an industri-al biogas plant with the aid of lab-oratory tests using the individual substrates.
Sandra Hermle
Thermo-hydraulics of solar energy systems
T
hermo-hydraulic modelling and simulation is one of the essential methods to reduce the costs of solar thermal ener-gy. As part of a thesis prepared at the University of Zurich, a variety of thermo-hydraulic methods and tools were developed and subse-quently incorporated into a manu-al that addresses manu-all tasks associat-ed with the sizing of solar energy systems, except for energy-relat-ed sizing, where excellent tools al-ready exist. The new tools help to avoid costs resulting from damage and malfunctions, and thus reduce production costs.Andreas Eckmanns
the plant with an acceptable de-gree of accuracy. For this purpose, the estimated level of methane production (based on laboratory tests) was compared with the ac-tual quantity measured at selected biogas plants. The results indicate that the level of methane produc-tion in the full scale facility is very Laboratory tests for
estimating industrial methane production