D. Assimacopoulos

Aessessment of biomass potential for power production: a GIS based method

Abstract A method is presented, which estimates the potential for power production from agriculture residues. A GIS decision support system (DSS) has been developed, which implements the method and provides the tools to identify the geographic distribution of the economically exploited biomass potential. The procedure introduces a four level analysis to determine the theoretical, available, technological and economically exploitable potential. The DSS handles all possible restrictions and candidate power plants are identified using an iterative procedure that locates bioenergy units and establishes the needed cultivated area for biomass collection. Electricity production cost is used as a criterion in the identification of the sites of economically exploited biomass potential. The island of Crete is used as an example of the decision-making analysis. A significant biomass potential exists that could be economically and competitively harvested. The main parameters that affect the location and number of bioenergy conversion facilities are plant capacity and spatial distribution of the available biomass potential.

Evaluation of Renewable Energy potential using a GIS decision support system

A GIS Decision Support System has been developed for the evaluation of Renewable Energy Sources potential and the financial analysis of RE investments. A GIS database with data on wind, topography, urban areas, and special activities has been developed and used for the evaluation of theoretical potential through the spatially continuous mapping of Renewable Energy Resources. The available and technological potential are evaluated by the application of availability and technological restrictions. The evaluation of economical potential is performed by a precise estimation of the expected energy output and installation cost. The financial analysis based on the Internal Rate of Return, identifies the financial viability of alternative investments. The evaluation of wind energy potential for the island of Crete, Greece and the financial analysis of a wind park installation are presented as a case study.

A GIS-based decision support system for planning urban transportation policies

Abstract A decision support system (DSS) integrated in a geographical information system (GIS) for the analysis and evaluation of different transport policies is presented. The objective of the tool is to assist transport administrators enhance the efficiency of the transportation supply while improving environmental and energy indicators. The DDS works on three levels. The first performs the transport network analysis, the second assesses the energy consumption and pollutant emissions and the third evaluates the several policies selected. Road traffic is simulated using a deterministic, multi-modal traffic assignment model with capacity constraints. The model allows the estimation of traffic flow patterns within each link of the road network starting from the knowledge of the network characteristics and traffic demand. Energy consumption and pollutant emission calculations are based on the methodology developed by the CORINAIR working group. The evaluation of each policy scenario is based on a number of traffic, environmental and energy indicators. A multi-criteria analysis, where decision is based upon judging over appropriate weighted criteria, is adopted. Models are integrated in a GIS environment, which serves as the repository of the data as well as the user interface of the tool. The use of the tool is demonstrated through characteristic case studies on the Greater Athens Area in Greece. Two policy measures, one concerning the extension of the region where half of the private cars are prohibited from entering to the Municipality of Athens and the other the reduction of parking places in the same region by 50% are evaluated.

Wall effects for motion of spheres in power-law fluids

The steady motion of spheres representing particles inside tubes filled with different fluids has been investigated using both a finite-element and a finite-volume method. The rheology of the fluids has been modelled by the power-law able to describe the shear-thinning (pseudoplastic) behaviour of a series of polymer solutions. New results have been obtained for a series of tube/sphere diameter ratios in order to investigate the wall effects on the drag exerted by the fluid on the sphere. The results agree well with previous simulations for an unbounded medium (infinite diameter ratio). Experimental investigations have also been carried out and simulated, and the results compare favourably with the experiments. The present simulations revealed the convergence of the drag coefficient to a constant value independent of tube-to-sphere diameter ratio when the power-law index approaches zero.

A finite volume approach in the simulation of viscoelastic expansion flows

Abstract A finite volume technique is presented for the numerical solution of viscoelastic flows. The flow of a differential upper-convected Maxwell (UCM) model fluid through an abrupt expansion has been chosen as a prototype example due to the existence of previous simulations in the literature. The conservation and constitutive equations are solved using the finite volume method (FVM) in a non-staggered grid with an upwind scheme for the viscoelastic stresses and a hybrid scheme for the velocities. An enhanced-in-speed pressure-correction algorithm is used and a new method for handling the source term of the momentum equations is introduced. Improved accuracy is achieved by a special discretization of the boundary conditions. Stable solutions are found for high Deborah numbers, further extending the range of previous similar simulations with the FVM. The solutions have been verified with grid refinement and show that at high elasticity levels, the domain length must be long enough to accommodate the slow relaxation of high viscoelastic stresses. The FVM is proven quite capable for numerically handling viscoelastic models with low computational cost and its use is recommended as a viable alternative to the solution of viscoelastic problems using a variety of constitutive models.

SOLAR POTENTIAL FOR WATER HEATING EXPLORED BY GIS

A method is presented for the estimation of solar energy and market potential for water heating in the residential sector. The model was developed under a Geographical Information System and provides the tools to handle the spatial and time discrepancies of solar radiation and energy demand. A geographic database with climatic data is used for estimating efficiencies and monthly/annual coverage of water heating load. Financial analysis is conducted on the basis of the energy production cost and the Net Present Value of the investment. Different financial scenarios are considered and the expected energy yields from a large-scale deployment of solar thermal systems in the residential sector of Greece are assessed.

MODEL FOR TRAFFIC EMISSIONS ESTIMATION

Abstract A model is developed for the spatial and temporal evaluation of traffic emissions in metropolitan areas based on sparse measurements. All traffic data available are fully employed and the pollutant emissions are determined with the highest precision possible. The main roads are regarded as line sources of constant traffic parameters in the time interval considered. The method is flexible and allows for the estimation of distributed small traffic sources (non-line/area sources). The emissions from the latter are assumed to be proportional to the local population density as well as to the traffic density leading to local main arteries. The contribution of moving vehicles to air pollution in the Greater Athens Area for the period 1986–1988 is analyzed using the proposed model. Emissions and other related parameters are evaluated. Emissions from area sources were found to have a noticeable share of the overall air pollution.

Water supply modeling towards sustainable environmental management in small islands: the case of Paros, Greece

Abstract The present approach has a two-fold emphasis. On one hand, water supply options are modeled and the optimal combination is presented through the identification of the least cost water supply scheme. On the other hand the results may be used towards the delineation of sustainable environmental policy options, particularly in the vulnerable system of small islands. Hence an optimization model has been developed that minimizes the Net Present Value (NPV) of water supply projected costs for the period 2002–2030 for Paros Island, Greece. The non-linear generalized reduced gradient method is used, taking the capacity of water supply options as the decision variable. The model incorporates the operation of groundwater wells and boreholes, surface storage reservoirs, conventional and wind-powered desalination and water hauling by ships. Finally, it estimates the monthly water production as well as the water supply costs. The identified solution involves the combined use of all water supply options and may provide the optimal contribution of each one of the supply sources, on a monthly time step. The results indicate that conventional water supply topped by versatile desalination schemes used for the particularly demanding water consumption peaks may be the focal area of responses for the island of Paros, and by extension for other areas around the world facing similar problems.

Market potential of renewable energy powered desalination systems in Greece

The present work analyzes water management strategies based on advanced desalination schemes powered by renewable energy sources. The framework for developing a decision procedure, which monitors water shortage problems and identifies the availability of renewable energy resources to power desalination plants, is presented. Cost of alternative solutions, taking into account energy cost or profits by energy selling to grid, is estimated. Emphasis is given to the market forces and the relationship of technology prices and market potential. A case study for the Aegean Islands in Greece is presented.

Enhancement of the momentum interpolation method on non-staggered grids

A novel interpretation of the momentum interpolation method (MIM) is presented in this paper. A revised method using quadratic interpolating polynomials for the calculation of the cell-face velocities is proposed. The performance of the proposed method (referred to as QMIM) is examined and its application to the well-known lid-driven flow in a square enclosure problem is tested. The computed results are compared with standard reported benchmark solutions for a wide range of flow conditions. The numerical experiments show clearly the superiority of the new approach over the original MIM, in terms of numerical accuracy, rate of convergence towards the grid-independent solution, and computational efficiency