摘要:The vast availability of wind power has fueled substantial interest in this renewable energy
source as a potential near-zero greenhouse gas emission technology for meeting future world
energy needs while addressing the climate change issue. However, in order to provide even a
fraction of the estimated future energy needs, a large-scale deployment of wind turbines
(several million) is required. The consequent environmental impacts, and the inherent
reliability of such a large-scale usage of intermittent wind power would have to be carefully
assessed, in addition to the need to lower the high current unit wind power costs. Our
previous study (Wang and Prinn 2010 Atmos. Chem. Phys.10 2053) using a
three-dimensional climate model suggested that a large deployment of wind turbines over
land to meet about 10% of predicted world energy needs in 2100 could lead to a
significant temperature increase in the lower atmosphere over the installed regions. A
global-scale perturbation to the general circulation patterns as well as to the cloud
and precipitation distribution was also predicted. In the later study reported
here, we conducted a set of six additional model simulations using an improved
climate model to further address the potential environmental and intermittency
issues of large-scale deployment of offshore wind turbines for differing installation
areas and spatial densities. In contrast to the previous land installation results,
the offshore wind turbine installations are found to cause a surface cooling over
the installed offshore regions. This cooling is due principally to the enhanced
latent heat flux from the sea surface to lower atmosphere, driven by an increase in
turbulent mixing caused by the wind turbines which was not entirely offset by the
concurrent reduction of mean wind kinetic energy. We found that the perturbation
of the large-scale deployment of offshore wind turbines to the global climate is
relatively small compared to the case of land-based installations. However, the
intermittency caused by the significant seasonal wind variations over several major
offshore sites is substantial, and demands further options to ensure the reliability
of large-scale offshore wind power. The method that we used to simulate the
offshore wind turbine effect on the lower atmosphere involved simply increasing
the ocean surface drag coefficient. While this method is consistent with several
detailed fine-scale simulations of wind turbines, it still needs further study to ensure
its validity. New field observations of actual wind turbine arrays are definitely
required to provide ultimate validation of the model predictions presented here.