• Energy Research
• Closed Access close
• Open Source close
• 7. Clean energy close
• 2. Zero hunger close
• 13. Climate action close
• Aurora Universities Network close

Efficiency of energy resource use is a key factor for a sustainable energy future. By matching the exergy levels of supply and demand, Energy Quality Management (EQM) of building energy supply systems may achieve more efficient use of energy resources. Beyond this, environmental impact of energy supply systems is another essential issue. This work addresses the influence of EQM on CO 2 emissions in the operation optimization of a Distributed Energy System (DES). A multi-objective linear programming problem is formulated to reduce energy costs and increase the overall exergy efficiency. Total CO 2 emissions are evaluated for the optimized operation strategies of the DES. The operators of the DES can choose the operation strategy from the Pareto front, based on their priorities and also aware of effects on CO 2 emissions. Results demonstrate more efficient use of energy resources and reduction in CO 2 emissions through EQM, as compared with conventional energy supply systems.

Cogeneration of heat and electricity is an important pillar of energy and climate policy. To plan the production and distribution system of combined heat and power (CHP) systems for residential heating, suitable methods for decision support are needed. For a comprehensive feasibility analysis, the integration of the location and capacity planning of the power plants, the choice of customers, and the network planning of the heating network into one optimization model are necessary. Thus, we develop an optimization model for electricity generation and heat supply. This mixed integer linear program (MILP) is based on graph theory for network flow problems. We apply the network location model for the optimization of district heating systems in the City of Osorno in Chile, which exhibits the “checkerboard layout” typically found in many South American cities. The network location model can support the strategic planning of investments in renewable energy projects because it permits the analysis of changing energy prices, calculation of break-even prices for heat and electricity, and estimation of greenhouse gas emission savings.

This paper presents an optimal control strategy for a district heating power plant with thermal energy storage. The main goal of the control strategy is to reduce the operation costs of the power plant, by scheduling the boilers, the operation of the thermal energy storage and the curtailment on the loads. The problem is stated as a constrained optimization in the form of a Mixed Integer Linear Program (MILP), embedded on an Model Predictive Control (MPC) framework. Particular attention is paid to modeling of boilers operating constraints, including the outlet water flow temperature, to the energy exchanged with the thermal energy storage and to the operating modes of the power plant layout, including the constraints related to the supply water temperature needed from the network. The results are performed using the data and the layout of the power plant located in the city of Ylivieska, in Finland. The cost analysis performed shows the advantages of using the predictive control strategy.

Historical time trends indicate that both carbon and energy intensity have declined in the United States over the last several decades, while economic performance, as measured by per capita GSP, has improved. This observation indicates that it may be possible to reduce carbon intensity without a reduction in economic performance. This paper assesses using panel analysis, the empirical relationship between carbon emissions intensity and economic performance, and examines the direction of causality between the two variables. Data for the analysis covered 48 states, excluding Hawaii, Alaska, and Washington DC, from 1980 to 2000. The results indicate significant bi-directional relationship between carbon emissions intensity and state economic performance, both using an aggregate indicator for carbon emissions intensity, decomposed using Laspeyres indexes and disaggregated by sector. This implies that it should be possible to implement statewide and sector-specific policies to reduce energy and carbon intensity and at the same time improve economic performance.

The progressive integration of Distributed Energy Resources (DERs) at distribution level is reshaping the role of distribution networks in the power system operation. Controllable loads, renewable sources, and storage systems can be managed from grid operators to provide services to the electrical grid. Nevertheless, a reliable and effective network control requires coordinated and optimized actions among transmission (TSO) and distribution (DSO) system operators. Assuming a shared balancing responsibility coordination model, the DSO will be called during the daily power system operation to dispatch optimally all control resources at distribution level in order to fulfil power exchange programs scheduled by the TSO. The feasibility of the application of a distribution optimal power flow routine in the assumed TSO-DSO coordination framework is studied through simulations on a detailed representation of an Italian MV urban distribution grid.

In this paper a high temperature thermal storage in a honeycomb solid matrix is numerically investigated and a parametric analysis is accomplished. In the formulation of the model it is assumed that the system geometry is cylindrical, the fluid and the solid thermophysical properties are temperature independent and radiative heat transfer is take into account whereas the effect of gravity are neglected. Air is employed as the working fluid and the solid material is cordierite. The evaluation of the fluid and thermal behaviors are accomplished assuming the honeycomb as a porous medium. The Brinkman-Forchheimer-extended Darcy model is used in the governing equations and the local thermal non equilibrium is assumed. The commercial CFD Fluent code is used to solve the governing equations in transient regime. Numerical simulations are carried out with storage medium at different mass flow rates of the working fluid and different porosity values. Results show the effects of storage medium, different porosity values, porosity effect and mass flow rate on stored thermal energy and storage time. Results in terms of temperature profiles and stored thermal energy as function of time are presented.

The growing recognition that global climatic change is a pressing reality and that its impacts on humans and ecological systems are inevitable makes adaptation a core topic in climate change research and policymaking. The glacier tourism sector that is highly sensitive towards changing climatic conditions is among the most relevant in this respect. This study aims to examine empirically how adaptation to climate change impacts is practiced by small- and middle-scale glacier tour operators. Data was collected by means of a set of semi-structured interviews with the managers or owners of nine small- or middle-scale tour companies operating in the Vatnajökull National Park in Southeast Iceland and observations of glacier sites where the respondents' companies are operating. The results indicate that all entrepreneurs consider climate change to be a real phenomenon that affects their present daily operations, but they perceive these implications not as significant threats to their business. The interaction of operator's attributes of agency such as firsthand experiences, risk perceptions, and abilities to self-organize, with structural elements of the glacier destination system such as economic rationales and hazard reduction institutions, has shaped and consolidated operators' adaptation processes in the form of a wait-and-see strategy combined with ad hoc reactive adaptation measures and postponed or prevented proactive long-term adaptation strategies.

A one-dimensional unsteady model is formulated for biomass gasification in a stratified concurrent (downdraft) reactor. Heat and mass transfer across the bed are coupled with moisture evaporation, biomass pyrolysis, char combustion and gasification, gas-phase combustion and thermal cracking of tars. Numerical simulation has allowed to predict the influence of model parameters, kinetic constants and operational variables on process dynamics, structure of the reaction front and quality of the producer gas. In particular, two different stabilization modes of the reaction front have been determined. For high values of the air-to-fuel ratio and of the primary pyrolysis rate, the process is top-stabilized, resulting in a high conversion efficiency and good gas quality. As the air flow is decreased below a critical limit value, the reaction front becomes grate-stabilized. The two different configurations are largely determined by the gas-phase combustion of volatile pyrolysis products. Finally, the predictions of the gas composition and the axial temperature profiles are in agreement with experimental data.

AbstractNowadays, many health, environmental, and economic concerns are associated with fossil fuel use, and therefore the improvement of new and advanced technologies and the use of renewable fuel...

Abstract An attractive path to the production of hydrogen from water is a two-step thermo chemical cycle powered by concentrated sunlight from a solar tower system. In the first process step the redox system, a ferrite coated on a monolithic honeycomb absorber, is present in its reduced form while the concentrated solar energy hits the ceramic absorber. When water vapour is fed to the honeycomb at 800 °C, oxygen is abstracted from the water molecules, bond in the redox system and hydrogen is produced. When the metal oxide system is completely oxidised it is heated up for regeneration at 1100–1200 °C in an oxygen-lean atmosphere. Under those conditions and in the second process step, oxygen is set free from the redox system, so the metal oxide is being reduced and after completion of the reaction again capable for water splitting. Since the overall process consists of two core reaction steps, which need to be carried out sequentially in a reactor unit at two different temperature steps, a special process and plant concept had to be developed enabling the continuous supply of product regardless of the alternating nature of the solar reactor operation. The challenge of the process control is to keep the two core reaction temperatures constant and to ensure regular temperature switches after completion of the individual process steps, independent of the weather conditions, like DNI fluctuation, clouds and wind speed. Also start-up, the fast switching after completion of half-cycles and the shutdown must be controlled. State of the art is the manual switching of heliostats to fulfil those control tasks. This paper describes the development and use of a system model of this process. The model consists of three main parts: the simulation of the solar flux distribution at the receiver aperture, the simulation of the temperatures in the reactor modules and the simulation of the hydrogen generation. It can be used for the analysis of the operational behaviour. The model is intended to be used in the future for the control of the whole process.