Definition of LCA guidelines in the geothermal sector to enhance result comparability

Geothermal energy could play a crucial role in the European energy market and future scenarios focused on sustainable development. Thanks to its constant supply of concentrated energy, it can support the transition towards a low-carbon economy. In the energy sector, the decision-making process should always be supported by a holistic science-based approach to allow a comprehensive environmental assessment of the technological system, such as the life cycle assessment (LCA) methodology. In the geothermal sector, the decision-making is particularly difficult due to the large variability of reported results on environmental performance across studies. This calls for harmonized guidelines on how to conduct LCAs of geothermal systems to enhance transparency and results comparability, by ensuring consistent methodological choices and providing indications for harmonized results reporting. This work identifies the main critical aspects of performing an LCA of geothermal systems and provides solutions and technical guidance to harmonize its application. The proposed methodological approach is based on experts’ knowledge from both the geothermal and LCA sectors. The recommendations cover all the life cycle phases of geothermal energy production (i.e., construction, operation, maintenance and end of life) as well as a selection of LCA key elements thus providing a thorough base for concerted LCA guidelines for the geothermal sector. The application of such harmonized LCA framework can ensure comparability among LCA results from different geothermal systems and other renewable energy technologies

Definition of LCA guidelines in the geothermal sector to enhance result comparability

Geothermal energy could play a crucial role in the European energy market and future scenarios focused on sustainable development. Thanks to its constant supply of concentrated energy, it can support the transition towards a low-carbon economy. In the energy sector, the decision-making process should always be supported by a holistic science-based approach to allow a comprehensive environmental assessment of the technological system, such as the life cycle assessment (LCA) methodology. In the geothermal sector, the decision-making is particularly difficult due to the large variability of reported results on environmental performance across studies. This calls for harmonized guidelines on how to conduct LCAs of geothermal systems to enhance transparency and results comparability, by ensuring consistent methodological choices and providing indications for harmonized results reporting. This work identifies the main critical aspects of performing an LCA of geothermal systems and provides solutions and technical guidance to harmonize its application. The proposed methodological approach is based on experts' knowledge from both the geothermal and LCA sectors. The recommendations cover all the life cycle phases of geothermal energy production (i.e., construction, operation, maintenance and end of life) as well as a selection of LCA key elements thus providing a thorough base for concerted LCA guidelines for the geothermal sector. The application of such harmonized LCA framework can ensure comparability among LCA results from different geothermal systems and other renewable energy technologies

Application of the method of data reconciliation for minimizing uncertainty of the weight function in the multicriteria optimization model

The multicriteria decision process consists of five main steps: definition of the optimisation problem, determination of the weight structure of the decision criteria, design of the evaluation matrix, selection of the optimal evaluation method and ranking of solutions. It is often difficult to obtain the optimal solution to a multicriterion problem. The main reason is the subjective element of the model – the weight functions of the decision criteria. Expert opinions are usually taken into account in their determination. The aim of this article is to present a novel method of minimizing the uncertainty of the weights of the decision criteria using Monte Carlo simulation and method of data reconciliation. The proposed method is illustrated by the example of multicriterion social effectiveness evaluation for electric power supply to a building using renewable energy sources

Przykładowe zastosowanie analizy efektywności substytucji energii i kosztów granicznych

In this paper the economic efficiency and the marginal cost of energy substitution (EEES and MCES) have been introduced. The EEES and analysis are applied in order to satisfy individual living and municipal requirements of inhabitants by means of different kinds of energy production and utilization appliances. The applied form of energy influences not only its cost (purchase energy prices) but also requires different investment and maintenance costs and, above all, it determines the final environmental impact. That is why described indicators are different for final energy production while using different types of energy carriers and methods of energy conversion. However, there are different utilization effects for each of the considered forms of energy in its final application. It may be particularly significant when the analyzed form of energy is the one that does not commonly occur. In the final part of this paper, the method of EEES and MCES along with a few examples of efficiency of energy substitution and its evaluation have been presented.Wykorzystując pojęcia wskaźnika efektywności substytucji oraz kosztu granicznego paliwa substytucyjnego, przeprowadzono ocenę efektywności różnych sposobów wykorzystania tego samego źródła energii (paliwa lub nośnika) w różnym zastosowaniu oraz porównano efektywność wykorzystania różnych źródeł energii w tym samym zastosowaniu. Te same produkty użyteczne można uzyskać przy stosowaniu różnych sposobów energetycznego zasilania procesów ich wytwarzania. Przez sposób energetycznego zasilania należy rozumieć zastosowane paliwo, nośnik energetyczny i jego parametry lub rodzaj energii. Poszczególne sposoby zasilania wpływają na koszty paliwowe, koszty pozapaliwowe, nakłady inwestycyjne na urządzenia i instalacje, straty środowiskowe oraz inne. Zróżnicowane są, w związku z tym, efekty ekonomiczne wytwarzania tych samych produktów użytecznych lub zaspokajania takich samych potrzeb, przy korzystaniu z różnych sposobów energetycznego zasilania. W pracy zaproponowano wykorzystanie powyższych wskaźników do oceny efektywności substytucji energii przy pozyskaniu komunalnobytowych produktów użytecznych: ciepła oraz ciepłej wody użytkowej

Thermo-fluid dynamic and kinetic modeling of hydrothermal carbonization of olive pomace in a batch reactor

Hydrothermal carbonization (HTC) represents one of the emerging and most promising technologies for upgrading biomass. Among the residual biomass waste, olive pomace and olive mill wastewater may be seen as valuable energy sources, especially for the Mediterranean countries, given the key role of the olive oil industry in those regions. This paper deals with the thermo-fluid dynamic performance of the HTC process of olive pomace. Computational Fluid Dynamics (CFD) modeling is employed in this study to numerically simulate such a process in batch reactor with the aim of understanding the complex fluid dynamics, heat transfer and reaction kinetics phenomena occurring under hydrothermal conditions. A parametric analysis is performed to evaluate the temperature fields inside the reactor and the output mass yields as a function of the power input required by the process. Velocity flow fields and the spatial distribution of the mixture during the process are also investigated to understand the change in feed conversion at different regions within the tubular reactor under different reaction times. The numerical results are validated and compared with experimental measurements conducted previously on a similar batch reactor. The model predictions are found to be in line with the experimental findings, thus laying the foundations for further modeling improvements towards the design optimization and scale-up of HTC reactors

Experimental and Numerical Electro-Thermal Characterization of Lithium-Ion Cells for Vehicle Battery Pack Applications

Batteries are the key elements for the massive electrification of the transport sector. With the rapidly growing popularity of electric vehicles, it is becoming increasingly important to characterize the behavior of battery packs through fast and accurate numerical models, in order to support experimental activities. A coupled electro-thermal simulation framework is required, as it is the only way to realistically represent the interactions between real world battery pack performances and the vehicle-level thermal management strategies. The purpose of this work is to pave the way for a comprehensive methodology for the development of a supporting modeling framework, to efficiently complement experiments in the optimal design and integration of battery packs. The full methodology consists of the following steps: i) an experimental analysis of the temperature and current dependence on various internal parameters of selected lithium-ion cells based on their electrochemical properties, ii) development and implementation of a battery cell electric model that takes into account the aforementioned dynamics and their dependencies; the electrical model is based on the Equivalent Circuit Model (ECM) and can be used to calculate the electrical output and losses of Li-ion cells as a function of state of charge and current; iii) development of a cell-level multi-domain computational framework for coupled electro-thermal simulations, based on state-of-the art CFD software tools; iv) validation and tuning of the multi-domain framework through ad-hoc designed experiments with controlled cell charge-discharge profiles and temperature measurement; v) extension of both the ECM and multi-domain approaches to full-scale battery packs, to be adopted for electric vehicle characterization under realistic driving conditions, with detailed battery thermal management. Results shown in the present paper cover steps i) to iv) and include a series of static and dynamic experimental tests with voltage response and temperature measurements performed on the selected Li-ion cells. It is shown that the proposed modeling tools can accurately predict the electro-thermal behavior of the cells under static and dynamic current conditions. Most of the average relative errors between predicted values and test values obtained do not exceed 10%

Feasibility of passive solar tracking through the thermal expansion of a PCM medium in a residential TES application: a numerical analysis

Phase Changing Materials (PCMs) are widely adopted and studied for Thermal Energy Storage (TES) applications, due to their inherent capability of storing and releasing high amounts of thermal energy in a narrow temperature range. At the same time, some of the materials commonly implemented in PCM-based TES devices (e.g. paraffin waxes or other organic materials) are known to experience a significant volumetric expansion (up to 20% or more) during their solid-to-liquid phase transition. Such expansion is generally considered a side effect, which should be accounted for to avoid damaging the PCM containment structure in the TES device. Recently, the thermally driven expansion of PCMs has been considered as a driving force for passive solar tracking, showing promising technical developments for dedicated solar tracking devices. In the present paper, we evaluate the feasibility of using the volumetric expansion cycles in a PCM-based TES device for PV solar tracking purposes, thus assuming an innovative and efficient integration between thermal and PV solar installations. To this aim, the temporal evolution of the temperature and density fields inside the PCM are modeled through a finite-difference/finite-volume numerical implementation. Accurate charge and discharge profiles of the TES device are implemented, assuming data from a previously investigated solar-assisted heating/cooling plant for a typical residential application in southern Italy. Outcomes from this numerical analysis allow to perform a parametric study in terms of specific tracking capability of the chosen PCM (paraffin wax) vs. the installed PV modules surface

Technical assessment of phase change material thermal expansion for passive solar tracking in residential thermal energy storage applications

Phase changing materials (PCMs) have been widely investigated for Latent Heat Thermal Energy Storage (LHTES) applications in the last decades, due to their inherently high volumetric storage density and thermal control features. Nonetheless, PCMs and their related LHTES systems still require significant scientific and technical advancements and more efficient market penetration strategies, to be able to play a key role in the massive transition towards renewable energy that is expected to take place in EU in the near future. Some of the most investigated PCMs for low to medium temperature LHTES belong to the alkanes/paraffins family, which is characterized by a relatively high volumetric expansion solid-to-liquid phase transition. This is generally considered a side effect, which should be accounted for to avoid damaging the containment structure. However, it could also represent an opportunity to add extra functionalities and increase the overall efficiency of LHTES systems. In this paper, we evaluate the feasibility of using the mechanical work generated by the volumetric expansion cycles in a paraffin-based LHTES device for photovoltaic (PV) solar tracking purposes, thus assuming a novel paradigm for the efficient integration between thermal and PV solar installations. To this aim, the temporal evolution of temperature and density fields inside the PCM are modeled through a finite-difference/finite-volume numerical approach. Accurate charge/discharge profiles of the TES are implemented, considering data from a previously investigated solar-assisted heating/cooling plant for a typical residential application in southern Italy. Outcomes from this analysis allow to estimate the tracking capability of the chosen PCM in terms of number/surface of actuated PV panels