WIND ENERGY EXPLORATION OVER THE ATACAMA DESERT A Numerical Model–Guided Observational Program RICARDO C. MUÑOZ, MARK J. FALVEY, MARIO ARANCIBIA, VALENTINA I. ASTUDILLO, JAVIER ELGUETA, MARCELO IBARRA, CHRISTIAN SANTANA, AND CAMILA VÁSQUEZ A Chilean program explores winds over the Atacama Desert region and is producing a public model and observational database in support of the development of wind energy projects. enewable energy, especially wind and solar, is an and execute measurement programs, and for the increasingly important field in applied meteorol- modeling of resource variability. Renewable energy Rogy and climate science. From the initial studies poses special challenges compared to more traditional that explore the availability of these energy resources meteorological applications (Emeis 2013). In the case in a given area, to the forecasting models required of wind power, for example, most phenomena of inter- to optimize the operation of wind or solar power est occur within the atmospheric boundary layer over plants, meteorological expertise is needed to design horizontal scales ranging from the microscale to the mesoscale. Moreover, the viability of many renew- able energy projects depends on the accuracy of the AFFILIATIONS: MUÑOZ AND ASTUDILLO—Department of Geophys- ics, University of Chile, Santiago, Chile; FALVEY AND IBARRA—De- meteorological variables measured and modeled, with partment of Geophysics, University of Chile, and Meteodata Ltd., even small errors having large financial implications. Santiago, Chile; ARANCIBIA AND ELGUETA—Department of Geophysics, On the other hand, the emergence of the renewable University of Chile, and Airtec Ltd., Santiago, Chile; SANTANA AND energy industry has led to a significant increase in the VÁSQUEZ—Ministerio de Energía, Santiago, Chile number of measuring sites being deployed worldwide, CORRESPONDING AUTHOR: Ricardo C. Muñoz, often in locations previously devoid of meteorologi- [email protected] cal data. The commercial market for meteorological The abstract for this article can be found in this issue, following the instrumentation has also responded, with the devel- table of contents. opment of sensors tailored to satisfy specific renew- DOI:10.1175/BAMS-D-17-0019.1 able energy requirements. While this enhanced data A supplement to this article is available online (10.1175/BAMS-D-17-0019.2) availability and new instrumentation certainly has In final form 12 April 2018 great scientific potential, it is true that because of the ©2018 American Meteorological Society commercial interests behind most renewable energy For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy. projects, the associated meteorological information is usually not fully available to the general scientific AMERICAN METEOROLOGICAL SOCIETY OCTOBER 2018 | 2079 Unauthenticated | Downloaded 10/10/21 07:22 PM UTC projects, but has also built up a public meteorologi- cal database over previ- ously data-void regions. The objective of this paper is to introduce this data- base to the meteorological community, describing the measurements and model results it contains, the tools available to access the information, and high- lighting some interesting climatic features revealed by the observations. With a latitudinal extent that spans from the tropics to the Southern Ocean (18°S to about 56°S in latitude and roughly along the 70°W meridian), Chile is subject to a large variety of climatic regimes. North of about 30°S, climate is largely con- ditioned by the southeast Pacific anticyclone, provid- ing for a very dry and stable free troposphere. To the south, the weather is deter- mined by the midlatitude westerlies and the synoptic modulation provided by the successive migration of low and high pressure systems. Zonally, the basic surface contrast provided by the ocean–continent interface to the west is further modu- lated inland by complex FIG. 1. Location map showing 45 meteorological stations over the Atacama Desert (inset shows location of the region in South America). Colors denote terrain that rises in less than the mean wind speed field simulated with the EE for 2010 at 100 m AGL. 300 km from sea level up to Letters and dashed ellipses indicate selected main zones for wind prospection. the Andes Cordillera along The bottom layer corresponds to a 30-m Shuttle Radar Topography Mission the eastern border of Chile, (SRTM) hillshade relief map. with maximum altitudes above 5,000 m north of community (e.g., Kusiak 2016). The present work 30°S. While this wide variety of climates and topog- describes a measurement and modeling program raphy led naturally to the assumption that there could funded mainly by the Chilean government over the be many regions in Chile where solar and wind energy last several years that is aimed at generating public potentials were high, the national energy agency (Min- information about the potential of renewable energy istry of Energy) realized in the early 2000s that a lack resources across the country. As such, it has not only of reliable measurements and quantitative information provided information upon which private investors about these resources was one of the main barriers have been able to develop new renewable energy for the development of renewable energy projects. A 2080 | OCTOBER 2018 Unauthenticated | Downloaded 10/10/21 07:22 PM UTC FIG. 2. Timeline of the national wind and solar exploration program. (top) Description of the observational ef- forts and measurement periods for the different selected zones, with color intensity representing higher station density. Blue is for 20-m towers, green for 60/80-m towers, yellow for solar monitoring sites, and red for PER stations. (bottom) Description of the modeling initiatives and the evolution of the EE: WF indicates wind farms in operation and LH and LV refer to the Loma del Hueso and Lengua de Vaca stations, respectively, which are the stations with the longest records in the observational database. series of projects were then initiated with the collabo- measure and quantify the solar energy resource being ration of both national universities and international documented in other reports (Rondanelli et al. 2015; assistance agencies, dedicated to the compilation of Molina et al. 2017). historical databases, measurement campaigns, and numerical modeling of wind and solar resources over EXPLORATION PROGRAM. Evolution. The the country (Santana et al. 2014). While the spatial first efforts of the national energy agency to gather extent of some of these activities encompasses all of information on wind potential over Chile involved Chile, the focus of the present contribution is on the the compilation of existing wind data from private northern part of the country, where the Atacama Des- and public sources (DGF 1993; UNTEC 2003; CERE ert is located (Fig. 1). This area was prioritized by the TABLE 1. Configuration of the WRF Model used for the EE. energy agency because its WRF version 3.2 energy demand is very high as a result of the presence Dynamical core Advanced Research core of the WRF (ARW) of a large copper mining Horizontal resolution (km) 27, 9, 3, 1 industry, while the aridity of Nesting method One way the region makes hydroelec- Vertical grid 42 sigma levels, 10-m spacing in the first 100 m tric energy generation (the Upper boundary (hPa) 50 principal renewable energy Model topography SRTM source in southern Chile) Time step (s) 40, 40, 13.33, 4.44 impossible. Therefore, in Time period simulated 2010 calendar year northern Chile solar and wind generation constitutes Data save interval (min) 60 a very attractive alterna- Lateral boundary condition 6-h operational analyses from the Global Forecast System tive to the fossil fuel–based Planetary boundary layer QNSE generation that has histori- Surface layer Monin–Obukhov cally supplied energy to the Solar radiation Rapid Radiative Transfer Model (RRTM) region. The focus of the Longwave radiation RRTM paper is further restricted to Cloud microphysics WRF single moment (5 class) the exploration of the wind resource, with the efforts to Convection scheme Kain–Fritsch (27- and 9-km grids only) AMERICAN METEOROLOGICAL SOCIETY OCTOBER 2018 | 2081 Unauthenticated | Downloaded 10/10/21 07:22 PM UTC EXAMPLES OF CIRCULATION FEATURES OVER THE ATACAMA DESERT ased on the data gathered by these zone B (b21 and T80CN in Fig. SB1) projected. While a diurnal cycle in wind Bprojects, a picture of the near-sur- are located along broad valleys running direction is noticeable in the annual face wind regime over several points from high elevations to the west down climatology of this station, the diurnal in the Atacama Desert is beginning to the lowlands in the east. Both show phase during winter is much reduced to emerge. An overriding character- a conspicuous nocturnal wind regime and strong northerly winds dominate, istic of this regime is a strong diurnal characterized by very persistent down- except for a brief weakening during the variability in wind speed and direction, valley wind directions (easterly in the evening transition (not shown). The hardly surprising given the extreme case of b21 and northerly in the case of location of these sites near the top insolation over the desert surface and T80CN) and relatively high wind speeds, of a zonally oriented mountain chain the general lack of synoptic variability. traits that are more marked during win- around 2,000 m MSL suggests that the The top panels in Fig. SB1 show the ter (not shown). Furthermore, the 80-m topography may be interacting here mean spatial pattern of mean diurnal towers in this zone show that the verti- with a northerly barrier jet existing in (left) and nocturnal (right) wind speed cal profiles of these nocturnal winds this region at this altitude (Rutllant et al. at 80 m simulated by the WRF Model. have a nose-like shape, with maximum 2013), a hypothesis that could eventu- The model shows the diurnal wind speeds occurring between 20 and 60 m ally be tested with numerical model regime to be spatially homogenous, AGL (see the “Nocturnal drainage flows diagnostics of these winds.