• Energy Research
• Closed Access close
• engineering and technology 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.

In order to protect our health and the environment, numerous limit and guideline values have been laid down for substances and contaminants that need to be regularly monitored. In such cases, the result of an analytical measurement is compared with its corresponding limit value, and a conclusion is then drawn as to whether the given limit has been violated or not. A simple approach to this would be to simply check whether the measured value is higher than the limit value or not. However, this approach is only acceptable when the measured value is far from the limit value. In cases where the analytical result is close to the limit value, the measurement uncertainty must also be taken into account when deciding whether an observed limit value transgression is significant or not—as, for example, demanded in DIN EN 17025 [1]. Therefore, it is very important that chemical laboratories that perform routine tests for limit value transgression determine the measurement uncertainties associated with their methods by long-term validation [2, 3]. However, even in cases where a measurement result is presented together with its measurement uncertainty, clear rules should be established for comparing the measured value with a limit or guideline value [4, 5]. If such rules are misunderstood or ambiguous, feelings of insecurity can arise among the decision makers. If systematic errors are excluded, the measurement uncertainty can be reduced to random errors and dealt with statistically. Therefore, statistical concepts can be used to unobjectionably and reproducibly justify a decision made about whether a limit value has been violated or observed, and on the other hand to estimate the analytical effort required to achieve significant results. A test result leading to the statement that the limit value μ0 (in analogy to the terminology of clinical chemistry [7, 8]) has been transgressed will be called “positive,” while an inconspicious result will be termed “negative.” In this case, a test for a limit value transgression can lead to four possible outcomes, as listed in Table 1. Two types of erroneous outcome can occur, namely a false-positive (type I error) or a false-negative (type II error) result. The probability of a type I error is usually denoted α, and that of a type II error β.

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.

Abstract Sodium-promoted vanadium oxide catalysts supported on MCM-41 and TiO 2 (anatase) were investigated for the partial oxidation of ethanol to acetaldehyde. The catalysts were prepared by incipient wetness impregnation with a vanadium oxide content of 6 wt.%. The experimental characterization was performed by X-ray diffraction (XRD), N 2 adsorption, temperature-programmed reduction (TPR), and diffuse reflectance UV–vis. Temperature-programmed oxidation (TPO) was also used to identify carbon deposits on the spent catalysts. The presence of sodium plays a strong role in the dispersion and reducibility of the vanadium species as detected by TPR analysis and optical absorption spectroscopy. While sodium addition increases the dispersion of the VO x species, its presence also decreases their reducibility. Additionally, TPO of the spent catalysts revealed that an increase in the Na loading decreases the carbon deposition during reaction. In the case of the catalysts supported on MCM-41, these modifications were mirrored by a change in the activity and selectivity to acetaldehyde. Additionally, on the VO x /TiO 2 catalysts the catalytic activity decreased with increasing sodium content in the catalyst . A model in which sodium affects dispersion, reducibility and also acidity of the supported-vanadia species is proposed to explain all these observations.