Small Hydropower Potential Assessment using Remote Sensing and - PDF document

Jan-Philipp Grett and Torsten Fay Small Hydropower Potential Assessment using Remote Sensing and Hydrological Data – The hydroMinds Model. Technical Report and Model Presentation. Identifjcation of new renewable energy resources is of crucial importance to reduce fossil fuel dependency and to address the cause of climate change. In many countries, and particularly developing countries, insuffjcient information on stream networks and topography as well as a lack of expertise and project funding are often burdens for the implementation of new hydropower projects. To identify hydroelectric power opportunities even in remote areas, the hydroMinds model uses globally available remote sensing data. Stream networks and catchment areas are derived from a digital elevation model (DEM). Hydrological modeling and a GIS-based terrain analysis allow an estimation of the theoretical hydroelectric power potential of individual water courses, regions and whole countries. Regional data and local expertise is not obligatory to produce results, but will help to validate or improve the accuracy of the results. The web-based and stand-alone hydroMinds Tool allows modifying several parameters to prove and analyze impacts at identifjed sites without having to use additional software. Both, map outputs and the software tool allow estimating the hydropower potential for water courses even with few local data records, and help concentrating cost- and time-intensive in-depth studies to pre-identifjed sites. 1 Background and Data (DEM). Input Data Elevation Vegetation Soil Rainfall Requirements Data Data Data Data Water courses suitable for hydropower generation have sustainable and ideally Pre-Processing Digital Terrain Analysis Hydrological Modeling high fmow rates as well as steep gradients between intake and powerhouse creating the necessary head. Hydropower facilities Analysis require a diversion dam to direct water Physical Parameters from a stream into the hydraulic system that conveys the water to a powerhouse. Technical Technical Parameters Hydropower Potential Turbines and generators convert potential energy into electricity before the water Ecological Parameters returns to the stream. To locate hydropower opportunities, Economically viable reliable elevation data, information Economic Parameters Hydropower Potential on land-use and land-cover as well as precipitation data is required. Remote sensing data products can be used Post-Processing to derive a Digital Elevation Model Visualization (DEM) of the study area and to classify vegetation structures. Information about precipitation may be obtained from global Fig. 1: Flow Chart of the main components and processes of the hydroMinds model. climate databases, if local precipitation data is not available. Local discharge measurements and high accurate 2 Methodology elevation data will increase the accuracy Tie grid points represent cells with a of the outputs. square shape with the grid point being Data Pre-Processing Several data products with difgerent located in the center of the cell. All accuracy levels can be used when applying As all input data of the hydropower relevant spatial information is joined to the hydroMinds model. Even minimum potential analysis is referring to spatial the grid points according to its spatial standard data provide a good overview information, a Geographic Information location. Tie attribute data of all grid and allow comparing river sections as of System (GIS) will be established. For all points is transferred to a sql-database their estimated hydropower potential. calculations and data storage, a point serving the computer-based analysis More accurate data products along with grid layer of the study area is developed and decision-making tool to estimate local data and expertise may lead to fjrst referring to the spatial resolution of the the technically and economically viable capacity appraisals of identifjed sites. raster-based Digital Elevation Model. hydropower potential. www.geominds.de 1

Tie GIS-based analysis can be divided assigned information about elevation, direct runofg of each grid cell is calculated into the digital terrain analysis and the vegetation, soil and rainfall according under consideration of variable runofg hydrological modeling. to their spatial location and linked to coeffjcients depending on the CN value the river data point they drain into. Tiis and a 21-day prior rainfall-index as well Digital Terrain Analysis allows the calculation of the available as of regional climatic conditions [9], Tie objective of the digital terrain analysis discharge for every river grid point. [13]. As steep slope conditions reduce is to identify catchment boundaries and the infjltration rate, a linear regression Hydrological Modeling to model the topographic characteristics algorithm based on the slope inclination of the catchment as well as the resulting To minimize skew results of the hydrologic of the grid cell complements the stream network. modeling process it is very important to hydrological modeling. Depending on the Tie GIS-based terrain analysis is apply only models that are suitable for the temporal resolution of the precipitation subject to the presumption that the direct study region. Several hydrologic models data, the available mean discharge at each runofg of any given cell fmows downhill in have been developed and verifjed for the river data point is calculated. the direction of the greatest slope. To allow use in certain regional areas of the world. all cells of the input DEM-data draining For all study areas with a good downhill, the elevation model is cleared of availability of essential input data, 3 Estimating the Technical errors such as surface depressions, which regionally verifjed hydrologic models can Hydropower Potential would act as water sinks. be applied. Tiis allows considering any To calculate the fmow direction for kind of specifjc climatic condition of the each grid point, the deterministic 8 (D8) study area that may have a strong impact Tie potential energy of downhill fmowing algorithm is applied [4]. According to the on the runofg processes, as for example water of a stream regardless of any physical, fmow direction of all cells, each grid point snow and ice occurrence during winter technical or economic limitation is defjned is assigned a value corresponding to the time in moderate climate zones. as the gross theoretical hydropower number of cumulated cells fmowing to it For all areas with limited data potential. According to physical and [8]. Cells with no infmow correspond to availability, a modifjed version of the technical reasons hydropower plants the pattern of ridges and form catchment US Soil Conservation Service Curve aren’t able to fully use the gross theoretical boundaries. Number (SCS-CN) method for modeling hydropower potential. Tie technical To introduce a lower boundary the precipitation-runofg processes is potential of hydropower describes the for the calculation of the hydropower applied to allow fjrst assumptions about energy capacity that is actually useable potential, a minimum hydraulic head and the hydropower potential of the stream when technical, infrastructural, ecological a minimum area to accumulate runofg network. Globally available satellite- and other conditions are taken into water are defjned. Tie minimum size based data products can be obtained to consideration [3]. of the hydrologic catchments is set to compensate for any missing yet relevant Applying the hydroMinds model, 4.5 km² which allows a sensible minimum input data. Tie original SCS-CN method is the technical hydropower potential is fmow accumulation. Tie data processing an empirical approach based on simplifjed, calculated for each grid point representing routine recognizes only those grid points experimentally derived relationships. Tie a river. Tius, each assessed river point as river that are connected to at least the combination of land-use, land-cover, forms a virtual powerhouse location. Tie minimum catchment size. hydrological soil type and the antecedent virtual intake for the respective virtual All river grid points of each catchment moisture condition of a grid cell are project is defjned being 1,000 m upstream. are joined to form the primary river of refmected in defjned curve number values Tiis assumption creates a series of virtual the respective catchment. All other grid [1], [11], [12]. hydropower projects along the considered points which are not defjned as rivers are According to the modifjed version, the river to ensure compatibility. Fig. 2: Streamfmow Discharge Analysis of the Roseau River. Final product of the Hydropower Potential Analysis Dominica in 2013 applying the hydroMinds model . 2 www.geominds.de