Experimental Analysis of Partial Evaporation Micro-ORC for low -temperature Heat Recovery

In this paper, we present an experimental assessment of the performance of a partial evaporating organic Rankine cycle (PE-ORC) power system. The system converts low temperature heat into electrical energy, with a power size around 1 kW, thus suitable for micro generation in the residential sector. Although the test bench was designed for operating with superheated vapour at the expander inlet, it has demonstrated to be able to work with the expansion occurring entirely in two-phase condition. Since the direct measurement of the vapour quality is not possible using the sensors installed in the test rig, the state of the fluid in the two-phase condition is estimated by means of the thermal balance at the heat exchangers, so the thermodynamic cycle can be evaluated. Temperatures of the heat source in the range between 40 C and 75 C have been tested, and for each temperature value the vapour quality at the expander inlet has been varied by regulating the feed -pump rotating speed. Experimental data are provided regarding the performance of the overall cycle, of the heat exchangers, of the expander and of the feed -pump. It was observed that the effectiveness of the evaporator and the efficiency of the pump are improved with respect to the operation with superheated vapour at the expander inlet. However, the overall performance is lower, especially due to the high ratio of the pump consumption over the expander produced power, commonly called back work ratio (BWR). The latter, under some boundary conditions, has resulted higher than the unit, meaning that the system is not able to produce net electrical power. The aim of the paper is to identify the design characteristics required by a micro -ORC energy system in order to enhance its performance in the PE operating mode

Control strategy and performance of a small-size thermally integrated Carnot battery based on a Rankine cycle and combined with district heating

To encourage decarbonization and promote a widespread penetration of renewable energy sources in all energy sectors, the development of efficient energy storage systems is essential. Interesting grid-scale electricity storage technologies are the Carnot batteries, whose working principle is based on storing electricity in the form of thermal energy. The charging phase is performed through a heat pump cycle, and the discharging phase is conducted through a heat engine. Since both thermal and electric energy flows are involved, Carnot batteries can be adopted to provide more flexibility in heat and power energy systems. To this aim, efficient scheduling strategies are necessary to manage different energy flows. In this context, this work presents a detailed rule-based control strategy to schedule the synergetic work of a 10-kWe reversible heat pump/organic Rankine cycle Carnot battery integrated to a district heating substation and a photovoltaic power plant, to satisfy a local user's thermal and electric demand. The coupling of a Carnot battery with a district heating substation allows for shaving the thermal demand peaks through the thermal energy stored in the Carnot battery storage, allowing for a downsizing of the district heating substation, with a considerable reduction of the investment costs. Due to the multiplicity of the involved energy flows and the numerous modes of operation, a scheduling logic for the Carnot battery has been developed, to minimize the system operating costs, depending on the boundary conditions. To investigate the influence of the main system design parameters, a detailed and accurate model of the Carnot battery is adopted. Two variants of the reference system, with different heat pump cold source arrangements, are investigated. In the first case, the heat pump absorbs thermal energy from free waste heat. In the second case, the heat pump cold source is the return branch of the district heating substation. The simulation results show that, in the first case, the Carnot battery allows the downsizing of the district heating substation by 47 %, resulting in an annual gain of more than 5000 €. About 70 % of the economic benefit is due to the possibility of reducing the power size of the district heating substation, which can be from 300 to more than 500 kW. The payback period is estimated to be lower than 9 years, while in the second case, the Carnot battery is not able to provide a gain. Eventually, the influence of some parameters, such as the photovoltaic power plant surface, the storage volume, the electricity price profile and the reversible heat pump/organic Rankine cycle specific investment cost, on the techno-economic performance of the system, is investigated through a wide sensitivity analysis. According to the results, the photovoltaic panels surface does not significantly affect the economic gain, while the storage capacity strongly affects the system scheduling and the operating costs. Indeed, it is possible to identify that 13 m3 is the size of the storage volume that minimizes the payback period to 8.22 years, for the considered application. An increase in the electricity price without an increase in the thermal energy price leads to a decrease in economic gain because the benefit brought by the downsizing of district heating is less significant on the economic balance. The specific investment cost of the reversible heat pump/organic Rankine cycle does not influence the operating cost; thus, it does not change the Carnot battery management, nor the economic gain. The specific investment cost affects the payback period, which increases from 8.6 years for a specific cost of 2000 €/kWe to 15.7 years for a specific cost of 5000 €/kWe

Therapeutic sequences in patients with grade 1−2 neuroendocrine tumors (NET): an observational multicenter study from the ELIOS group

Purpose: Many different treatments are suggested by guidelines to treat grade 1−2 (G1−G2) neuroendocrine tumors (NET). However, a precise therapeutic algorithm has not yet been established. This study aims at identifying and comparing the main therapeutic sequences in G1−G2 NET. Methods: A retrospective observational Italian multicenter study was designed to collect data on therapeutic sequences in NET. Median progression-free survival (PFS) was compared between therapeutic sequences, as well as the number and grade of side effects and the rate of dose reduction/treatment discontinuation. Results: Among 1182 patients with neuroendocrine neoplasia included in the ELIOS database, 131 G1–G2 gastroenteropancreatic, lung and unknown primary NET, unresectable or persistent/relapsing after surgery, treated with ≥2 systemic treatments, were included. Four main therapeutic sequences were identified in 99 patients: (A) somatostatin analogs (SSA) standard dose to SSA high dose (n = 36), (B) SSA to everolimus (n = 31), (C) SSA to chemotherapy (n = 17), (D) SSA to peptide receptor radionuclide therapy (PRRT) (n = 15). Median PFS of the second-line treatment was not reached in sequence A, 33 months in sequence B, 20 months in sequence C, 30 months in sequence D (p = 0.16). Both total number and severity of side effects were significantly higher in sequences B and C than A and D (p = 0.04), as well as the rate of dose reduction/discontinuation (p = 0.03). Conclusions: SSA followed by SSA high dose, everolimus, chemotherapy or PRRT represent the main therapeutic sequences in G1−G2 NET. Median PFS was not significantly different between sequences. However, the sequences with SSA high dose or PRRT seem to be better tolerated than sequences with everolimus or chemotherapy

Performance prediction of a reciprocating piston expander with semi-empirical models

Abstract The aim of this study is to characterize a prototype of reciprocating piston expander integrated into a micro-ORC system test bench (in the kW range of power), installed at the laboratory of the university of Bologna. In order to simulate behavior and performances of the expander in not yet explored operating conditions, two semi-empirical models proposed in the literature have been opportunely adapted to the case of study and calibrated over a full set of available experimental data. One model is based on polynomial correlations on the expander efficiencies, whereas the other one is based on a lumped parameters approach with a more physical sense. Both the models have been evaluated on the error on predict the outputs and compared into performance prediction maps. The preliminary results demonstrate that the polynomial fitting functions model is the most accurate in predicting the outputs in the range of the explored working conditions. However, in order to verify the models extrapolation capability, more experimental points should be collected. The validation of the models outside the calibration range will be object of further investigations

Cytokine release syndrome after CAR infusion in pediatric patients with refractory/relapsed B-ALL: is there a role for diclofenac?

BACKGROUND: Cytokine release syndrome (CRS) is a major complication after chimeric-antigen receptor T-cell treatment, characterized by an uncontrolled systemic inflammatory reaction. We investigated the potential role of diclofenac in the management of CRS in five pediatric patients treated for relapsed/refractory B-lineage acute lymphoblastic leukemia. METHODS: In case of persistent fever with fever-free intervals shorter than 3 hours, diclofenac continuous infusion was initiated, at the starting dose of 0.5 mg/Kg/day, the lowest effective pediatric dose in our experience, possibly escalated up to 1 mg/Kg/day, as per institutional guidelines. RESULTS: CRS occurred at a median of 20 hours (range 8–27) after tisagenlecleucel infusion. Diclofenac was started at a median of 20 hours (range 13–33) after fever onset. A mean of 3.07 febrile peaks without diclofenac and 0.95 with diclofenac were reported (p = 0.02). Clinical benefit was achieved by hampering the progression of tachypnea and tachycardia. Despite fever control, CRS progressed in four of the five patients, and hypotension requiring vasopressors and fluid retention, as well as hypoxia, occurred. Vasopressors were followed by 1–2 doses of tocilizumab (one in patient 2 and two in patients 3, 4, and 5), plus steroids in patients 4 and 5. CONCLUSION: Based on a limited number of patients, diclofenac leads to better fever control, which translates into symptom relief and improvement of tachycardia, but could not prevent the progression of CRS

Dynamic Control of a Novel Planar Cable-Driven Parallel Robot with a Large Wrench Feasible Workspace

Cable-Driven Parallel Robots (CDPRs) are special manipulators where rigid links are replaced with cables. The use of cables offers several advantages over the conventional rigid manipulators, one of the most interesting being their ability to cover large workspaces since cables are easily winded. However, this workspace coverage has its limitations due to the maximum permissible cable tensions, i.e., tension limitations cause a decrease in the Wrench Feasible Workspace (WFW) of these robots. To solve this issue, a novel design based in the addition of passive carriages to the robot frame of three degrees-of-freedom (3DOF) fully-constrained CDPRs is used. The novelty of the design allows reducing the variation in the cable directions and forces increasing the robot WFW; nevertheless, it presents a low stiffness along the x direction. This paper presents the dynamic model of the novel proposal together with a new dynamic control technique, which rejects the vibrations caused by the stiffness loss while ensuring an accurate trajectory tracking. The simulation results show that the controlled system presents a larger WFW than the conventional scheme of the CDPR, maintaining a good performance in the trajectory tracking of the end-effector. The novel proposal presented here can be applied in multiple planar applications

Reactive Metals as Energy Storage and Carrier Media: Use of Aluminum for Power Generation in Fuel Cell-Based Power Plants

In recent years, the energy production sector has experienced a growing interest in new energy vectors enabling energy storage and, at the same time, intersectoral energy applications among users. Hydrogen is one of the most promising energy storage and carrier media featuring a very high gravimetric energy density, but a rather low volumetric energy density. To this regard, this study focuses on the use of aluminum as energy storage and carrier medium, offering high volumetric energy density (23.5 kWh L$^{-1}$), ease to transport and stock (e.g., as ingots), and is neither toxic nor dangerous when stored. In addition, mature production and recycling technologies exist for aluminum. Herein, the performance of power systems driven by aluminum powder in terms of electrical efficiency (η$_{(I)}$) and round‐trip efficiency (RTE) is analyzed. Along with the additional advantages relating to high volumetric energy density, and safety and management aspects, the aluminum‐based technology appears to outperform the power‐to‐power systems based on hydrogen and liquid fuels

Performance and operation of micro-ORC energy system using geothermal heat source

Abstract In the electricity production sector, geothermal energy is considered a reliable energy source because of its independence of seasonal, climatic and geographical conditions. Low-temperature geothermal wells present a huge potential of exploitation, as the development of binary cycles and the technological improvement in drilling make this heat source a competitive solution for electricity generated distribution and self-consumption. The Organic Rankine Cycle (ORC) is currently the best solution to convert heat into electricity using low enthalpy heat sources. The ORC technology is already mature and widespread for medium and large-scale power plants, applying for geothermal, solar, biomass or waste heat recovery exploitation. Micro-scale ORC applications are still not diffused in the market: the system layout, the working fluid selection and the expander architecture can significantly vary depending on the specific realization requirements, thus a standard configuration has not established yet. In this paper, a particular case study of a micro-ORC power system using a geothermal well is presented. The application in analysis is a plug-and-play ORC facility, currently installed and operating in a pool centre. The system layout and the main components are described. The heat source is a geothermal well, which continuously supplies (by pressure difference) liquid water at a temperature lower than 60 °C to a binary Rankine cycle working with R134a. The ORC system is driven by a prototypal radial-piston expander and adopts an external-gear feed pump and a recuperative cycle. It is developed for working continuously, delivering the generated electricity directly into the grid. The facility is provided with temperature, pressure and electric power sensors for monitoring the operation and for a preliminary evaluation of the performance. The global efficiency of expander and feed pump and the ORC net efficiency have been evaluated at the regular working conditions of the geothermal well, showing values equal to, respectively, 53 %, 41 % and 4.4 %

Experimental Performance of a Micro-ORC Energy System for Low Grade Heat Recovery

Abstract The state-of-the art of ORC energy systems is mainly dominated by large scale units in the MW range of power output, in the field of heat recovery at mid-high temperature levels (around 200-500°C), where multiple commercial realizations are available. Nevertheless, the cutting-edge niche of micro-ORC energy systems offers good solutions for low-temperature heat recovery. Many prototypes are currently under investigations, but a leading technology is not yet established. This work reports an experimental activity carried out for performance characterization of a prototypal micro-ORC energy system. In particular, the paper presents the test bench developed in the laboratories of the University of Bologna and the first obtained results in terms of thermodynamic performance and main components characteristics. The ORC system comprises a small reciprocating three-piston expander, run on R134a as operating fluid. Heat is provided to the ORC from an external source, via hot water at temperature below 100 °C, in order to simulate a low-enthalpy heat recovery process. The system rejects unused heat via a water cooled condenser. Thus, the investigated ORC is a plug and play system, requiring only to be connected to the hot and cold heat sources. The ORC system has been tested for prolonged operation at various thermal input conditions. In particular, the behavior of the key cycle parameters and performance indexes (e.g. max. and min. pressures, superheating temperature, expander isentropic efficiency, electric power output, etc.) are investigated as function of pump rotational speed (i.e. organic fluid mass flow rate), for three different set point values of the hot source (65 °C, 75 °C, 85 °C). The operating thermodynamic cycle has been completely characterized by means of a real-time measurement and acquisition tool, developed in LabVIEW environment. Performance variations of the system have been monitored: the electric power output ranges between 0.30 to 1.2 kW, with gross efficiency in the range 2.9-4.4 %, while the expander "electro-isentropic" efficiency results in the range of 35-42 %