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This work addresses the problem of transmission expansion-planning in the context of the reregulation and liberalization of power systems. The transmission expansion-planning problem is formulated as an integer problem and it is solved keeping that characteristic using simulated annealing. In the scope of the access to the transmission networks and the corresponding payments for use of networks, the paper discusses the advantages and drawbacks from adopting several cost methods and, more specifically, short-term and long-term nodal marginal prices. Long-term marginal prices are computed in the framework of the simulated annealing algorithm and led to the calculation of the marginal based remuneration to the transmission company. The paper includes case studies based on the Portuguese 400/220/150 kV network and on a didactic 6-bus system.

Enhanced weathering (EW) is one of the most promising negative emissions technologies urgently needed to limit global warming to at least below 2 °C, a goal recently reaffirmed at the UN Global Climate Change conference (i.e., COP26). EW relies on the accelerated dissolution of crushed silicate rocks applied to soils and is considered a sustainable solution requiring limited technology. While EW has a high theoretical potential of sequestering CO2, research is still needed to provide accurate estimates of carbon (C) sequestration when applying different silicate materials across distinct climates and major soil types in combination with a variety of plants. Here we elaborate on fundamental advances that must be addressed before EW can be extensively adopted. These include identifying the most suitable environmental conditions, improving estimates of field dissolution rates and efficacy of CO2 removal, and identifying alternative sources of silicate materials to meet future EW demands. We conclude with considerations on the necessity of integrated modeling-experimental approaches to better coordinate future field experiments and measurements of CO2 removal, as well as on the importance of seamlessly coordinating EW with cropland and forest management.

Shallow Geothermal Systems (SGS) are widely used to provide low-cost heating and cooling of residential and commercial buildings. SGS can be an economically-viable solution even for commercial buildings, where controlled temperature is fundamental for the production processes. To assess the thermal resistance of the soil and the performance of a SGS, Thermal Response Tests (TRT) must be performed. TRT machines are today designed mainly for short term monitoring, for relatively deep SGS (up to 200 m) and for being used by expert operators. Lightweight, low-cost machines for both fast and long term, reliable and unattended TRT for very Shallow Geothermal Systems (vSGS) are not available today. This paper describes the design of a micro-TRT machine (mTRT) for vSGS, which is gaining interest in the civil engineering, environmental, energy and food chain sectors. The paper describes the features of the wireless monitoring system, the design choices to achieve the required accuracy and the software developed for adding remote control capability. Experimental validation in a real test field demonstrates the quality of measurements collected for analysing the TRT data.

Many different PBR designs have been proposed for biofuel production, few of them have been tested at pilot-scale, none developed at the (large) scale necessary for a complete and correct evaluation. Thus the main issues that impact on the reactor's performance (i.e., suitable construction materials, efficient mixing, heating/cooling, CO2 supply and oxygen removal), although explored at pilot level, still await evaluation at real scale. Although the main limitations of PBR are the high cost and the reduced scalability, with few exceptions, R&D on photobioreactor design is aimed at achieving high photosynthetic efficiencies and at pushing productivity beyond that currently attainable. The main strategies explored to this end are intensive mixing, light dilution via large external surfaces or internal light conducting structures. This chapter reviews and examines recent advances and innovations in photobioreactor design and operation.

The reduction of the dioxin levels in the exhausts of today waste-to-energy plants relies on the control of the thermo-fluid-dynamic processes occurring within the combustion chamber, rather than on policies aimed at restricting the amount of chlorine in the waste material to be treated. This is a consequence of the fact that waste-to-energy plants currently receive the bulk of discarded PVC and other chlorine sources that are deliberately burned in order to increase the waste heating value. Indeed, severe law regulations are into force in many industrialised countries, posing constraints on the value of some relevant in-chamber thermo-fluid-dynamic variables, such as temperature and residence time of the gases resulting from the combustion process, whose accurate experimental monitoring is extremely expensive and difficult to achieve. The present work analyses the shortcomings of the methods generally employed in full scale plants for the verification of the temperature and residence time of gases produced during the combustion process, and presents the advantages of using a new procedure developed by authors, based on the numerical simulation of the waste combustion process to optimise monitoring of the quantities of interest. The verification of the developed model, which accounts for both the solid and the gaseous phases, and for the various modes of heat and mass transfer between these phases, is obtained through a comparison with the results of an experimental campaign carried out on a full scale plant in Italy. The temperature distribution in the combustion chamber is calculated considering various waste compositions, and both forced and mixed convection. In fact, it is also shown that neglecting buoyancy effects may lead to appreciable errors.

Abstract We define heat as a particular kind of nonwork interaction that involves only energy and entropy transfers, and that is entirely distinguishable from work. The existence of heat interactions is a consequence of the first and second laws of thermodynamics. The requirement that heat be entirely distinguishable from work implies strict conditions on the end states of the interacting systems, and guarantees a definite relation between such states and the energy and entropy transfers. We illustrate these conditions by using energy versus entropy graphs. Many experiences can be represented as heat interactions, including the exchanges between two black bodies at temperatures that differ infinitesimally. We discuss the latter point in a companion paper at this conference.

The effective compression ratio of spark ignition engines is influenced by several factors, and can feature a relatively wide range even for production power units. This is given mainly by the tolerances used for different components, but also due to the actual operating parameters that can result in different thermal regimes and therefore in dimensional variations. Given their design, optical engines are characterized by high crevice volumes and increased blow-by losses. Within this context, this work was aimed at developing a procedure for estimating the effective compression ratio and charge losses, based on the analysis of in-cylinder pressure traces. Compared to existing methods that require heat release rate modeling for ensuring good accuracy, the proposed route follows a different approach, that uses sub-models only for simulating heat transfer and blow-by losses. In this way, acceptable error levels were ensured, with minimum computational demand. The new procedure was applied on two different engine configurations, as well as operation with different fuels. Estimation of combustion efficiency was found to be an important issue for correct blow-by losses determination, while compression ratio evaluation depended mostly on the thermal regime of the piston.

The synchronous generators' excitation is usually regulated by means of a real-time digital control system, while other apparatuses are dedicated to secondary functions (e.g human machine interface, remote control unit, logic and control functions). A performance increase and a cost reduction can be achieved by integrating all the functions into a single platform. However, this requires assessing the dependability performance of the control systems currently in use, to set a base benchmark for future evaluations. In this paper, the quantitative dependability analysis of a digital excitation control system is performed, by using as a case study a real system installed in a hydroelectric power station. Two configurations are analyzed, and their dependability performance are compared.