REA: Resource Exergy Analysis - A basic guidline for application

This publication provides a basic guideline to the application of Resource Exergy Analysis (REA). REA is a proven application of exergy analysis to the field of technology comparison. REA aims to help decision makers to obtain an indicator in addition to GHG emissions, that is grounded in science. Resource exergy consumption can replace the less comprehensive primary energy consumption as an indictor and reduce the risk of suboptimal decisions. Evaluating energy systems using REA is key to ensure that climate targets are reached in time.

REA: Resource Exergy Analysis - A basic guidline for application

This publication provides a basic guideline to the application of Resource Exergy Analysis (REA). REA is an application of exergy analysis to the field of technology comparison. REA aims to help decision makers to obtain an indicator in addition to GHG emissions, that is grounded in science. Resource exergy consumption can replace the less comprehensive primary energy consumption as an indictor and reduce the risk of suboptimal decisions.

Exergy-Based Assessment of Polymers Production and Recycling: An Application to the Automotive Sector

In the last century, the economic growth has been accompanied by a worldwide diffusion of polymers for multiple applications. However, there is a growing attention to the environmental pollution and energy consumption linked to the unconditional use of plastic. In the present work, exergy is used as a measure of the resource consumption during the life cycle of polymers. Nine commercially diffused polymers are chosen, and their production chains are identified according to the “grave to cradle” approach. The global Embodied Exergy (EE) is calculated as the sum of the contribution of each step of the chain, including the production process and the Exergy Replacement Cost (ERC) of the fossil fuel. Then, recycling routes and the associated exergy consumption are analysed. Thermodynamic recycling indexes are developed depending on the final product, namely the crude polymeric material and the oil derivatives or structural molecules. The main results show that some commonly used polymers have a considerable impact in terms of EE (e.g., PET). Recycling indexes encourage the recycling processes, which are always energetically convenient (from 10% to 60% of exergy savings) compared with the production from virgin raw material. Results from EE calculation are used for the thermodynamic assessment of the plastic content of vehicle components, to obtain useful information for recycling practices development.

Modelling Grid Constraints in a Multi-Energy Municipal Energy System Using Cumulative Exergy Consumption Minimisation

Efficiency measures and the integration of renewable energy sources are key to achieving a sustainable society. The cumulative exergy consumption describes the resource consumption of a product from the raw material to the final utilisation. It includes the exergy expenses for energy infrastructure as well as the imported energy. Since consumers and renewable potentials are usually in different locations, grid restrictions and energy flows have a significant impact on the optimal energy system design. In this paper we will use cumulative exergy minimisation together with load flow calculations to determine the optimal system design of a multi-cell municipal energy system. Two different load flow representations are compared. The network flow model uses transmission efficiencies for heat, gas and electricity flows. The power flow representation uses a linear DC approximated load flow for electricity flows and a MILP (mixed integer linear programming) representation for heat and gas flows to account for the nonlinear pressure loss relation. Although both representations provide comparable overall results, the installed capacities in the individual cells differ significantly. The differences are greatest in well meshed cells, while they are small in stub lines.

Internal Microclimate: Cumulative Exergy Consumption in a Sandcrete and a Burnt Brick- Walled Structure

Current practices of planning and designing of buildings in Nigeria do not consider the thermal comfort, the building energy and exergy demand. There is a need for better understanding of exergy analysis to improve the quality match between building energy demand and supply. The aim of this study is to estimate the exergy consumption value for a hollow sandcrete and a burnt brick-walled structure in a tropical sub-region. The properties of the building were assessed, eQuest software was used to estimate the energy demand of the respective buildings and the exergy analysis was conducted using the exergetic factor of electricity. The cumulative exergy consumptions of the existing sandcrete-walled building, the modelled sandcrete and the burnt brick-walled building were found to be 246,074.4 MJ/year, 128,646 MJ/year, and 128,595.6 MJ/year respectively. The modelled sandcrete-walled building, as well as the burnt brick-walled building, were found to be 48% more energy efficient than the existingbuilding as a result of improving the airtightness of the building, reducing the solar heat gain, and utilizing extremely efficient systems. However, the exergy analysis suggested that the hollow burnt brick-walled building perform better than the hollow sandcrete-walled building. Keywords: Building, electricity, energy, eQuest, exergy, sandcrete.

Exergy as Criteria for Efficient Energy Systems—A Spatially Resolved Comparison of the Current Exergy Consumption, the Current Useful Exergy Demand and Renewable Exergy Potential

The energy transition from fossil-based energy sources to renewable energy sources of an industrialized country is a big challenge and needs major systemic changes to the energy supply. Such changes require a holistic view of the energy system, which includes both renewable potentials and consumption. Thereby exergy, which describes the quality of energy, must also be considered. In this work, the determination and analysis of such a holistic view of a country are presented, using Austria as an example. The methodology enables the calculation of the spatially resolved current exergy consumption, the spatially resolved current useful exergy demand and the spatially resolved technical potential of renewable energy sources (RES). Top-down and bottom-up approaches are combined in order to increase accuracy. We found that, currently, Austria cannot self-supply with exergy using only RES. Therefore, Austria should increase the efficiency of its energy system, since the overall exergy efficiency is only at 34%. The spatially resolved analysis shows that in Austria the exergy potential of RES is rather evenly distributed. In contrast, the exergy consumption is concentrated in urban and industrial areas. Therefore, the future energy infrastructure must compensate for these spatial discrepancies.

Optimal Municipal Energy System Design and Operation Using Cumulative Exergy Consumption Minimisation

In developed countries like Austria the renewable energy potential might outpace the demand. This requires primary energy efficiency measures as well as an energy system design that enables the integration of variable renewable energy sources. Municipal energy systems, which supply customers with heat and electricity, will play an important role in this task. The cumulative exergy consumption methodology considers resource consumption from the raw material to the final product. It includes the exergetic expenses for imported energy as well as for building the energy infrastructure. In this paper, we determine the exergy optimal energy system design of an exemplary municipal energy system by using cumulative exergy consumption minimisation. The results of a case study show that well a linked electricity and heat system using heat pumps, combined heat power plants and battery and thermal storages is necessary. This enables an efficient supply and also provides the necessary flexibilities for integrating variable renewable energy sources.