Experimentally-validated models for the off-design simulation of a medium-size solar organic Rankine cycle unit

Organic Rankine Cycle is an efficient and reliable technology for the thermal-to-electricity conversion of low-grade heat sources but the variability in boundary conditions often forces these systems to operate at off-design conditions. The development of reliable models for the performance prediction of organic Rankine cycle power systems under off-design conditions is therefore crucial for system-level integration and control implementation. In this paper, a mathematical model for the evaluation of the expected performance of organic Rankine cycle power units in a large range of operating conditions based on experimental data collected in a medium-size solar organic Rankine cycle power plant is presented. Two different empirical approaches for the performance prediction of heat exchangers and machines, namely, constant-efficiency and correlated-based approaches, are proposed and compared. In addition, empirical correlations based on experimental data are proposed for the preliminary assessment of the energy demanded during the start-up phase and the corresponding duration. Results demonstrate that a good achievement in terms of accuracy of the model and reliability of the simulation performance can be obtained by using a constant-efficiency approach, with average errors lower than 5% and 2.5 K for the expected net power and outlet oil temperature respectively. The use of polynomial correlations leads to a more accurate estimation of the performance parameters used for evaporator and the turbine (in particular the evaporator heat effectiveness and the isentropic and electromechanical efficiency for the turbine), which strongly affect the main output variables of the model and, at the same time, are remarkably influenced by the operating conditions. A reduction in the average error in the prediction of the net power and outlet temperature of the heat transfer fluid to about 4% and 1.5 K respectively is therefore achieved by this approach. Average errors of 18.5% and 12.5% are achieved for the start-up time and the corresponding energy absorbed, respectively. Although the results obtained in terms of accuracy could be improved, these correlations can give an initial indication about the duration and energy required during this phase

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

Evidence-based calibration of a building energy simulation model: Application to an office building in Belgium

Energy services play a growing role in the control of energy consumption and the improvement of energy efficiency in non-residential buildings. This work consists in the application of a simulation-based approach dedicated to whole-building energy use analysis for use in the frame of an energy efficiency service process. Focus is given to the calibration of a simplified dynamic hourly building energy simulation model by means of available energy use data and to the integration of the calibration process into the Energy Service Process. The developed simulation tool and the associated calibration method are applied to a real case study building located in Brussels, Belgium. The use of an evidence-based method ensures sticking to reality and avoids bad representation and hazardous adjustment of the parameters. Moreover, it is shown that the use of a sensitivity analysis method is of a great help to orient data collection and parameters adjustment processes

Phase I trial combining temozolomide plus lapatinib for the treatment of brain metastases in patients with HER2-positive metastatic breast cancer: the LAPTEM trial

Background Brain metastases (BMs) pose a clinical challenge in breast cancer (BC). Lapatinib or temozolomide showed activity in BM. Our study assessed the combination of both drugs as treatment for patients with HER2-positive BC and BM. Methods Eighteen patients were enrolled, with sixteen of them having recurrent or progressive BM. Any type of previous therapy was allowed, and disease was assessed by gadolinium (Gd)-enhanced magnetic resonance imaging (MRI). The primary end points were the evaluation of the dose-limiting toxicities (DLTs) and the determination of the maximum-tolerated dose (MTD). The secondary end points included objective response rate, clinical benefit and duration of response. Results The lapatinib-temozolomide regimen showed a favorable toxicity profile because the MTD could not be reached. The most common adverse events (AEs) were fatigue, diarrhea and constipation. Disease stabilization was achieved in 10 out of 15 assessable patients. The estimated median survival time for the 16 patients with BM reached 10.94 months (95% CI: 1.09-20.79), whereas the median progression-free survival time was 2.60 months [95% confidence interval (CI): 1.82-3.37]. Conclusions The lapatinib-temozolomide combination is well tolerated. Preliminary evidence of clinical activity was observed in a heavily pretreated population, as indicated by the volumetric reductions occurring in brain lesion

Experimental and thermodynamic analysis of a bottoming Organic Rankine Cycle (ORC) of gasoline engine using swash-plate expander

This paper deals with the experimental testing of an Organic Rankine Cycle (ORC) integrate in a 2 liter turbocharged gasoline engine using ethanol as working fluid. The main components of the cycle are a boiler, a condenser, a pump and a swash-plate expander. Five engine operating points have been tested, they correspond to a nominal heat input into the boiler of 5, 12, 20, 25 and 30 kW. With the available bill of material based on prototypes, power balances and cycles efficiencies were estimated, obtaining a maximum improvement in the ICE mechanical power and an expander shaft power of 3.7% and 1.83 kW respectively. A total of 28 steady-state operating points were measured to evaluate performance of the swash-plate expander prototype. Operating parameters of the expander, such as expander speed and expansion ratio, were shifted. The objective of the tests is to master the system and understand physical parameters influence. The importance of each parameter was analyzed by fixing all the parameters, changing each time one specific value. In these sensitivity studies, maximum ideal and real Rankine efficiency value of 19% and 6% were obtained respectively.This work is part of a research project called "Evaluation of bottoming cycles in IC engines to recover waste heat energies" funded by a National Project of the Spanish Government with reference TRA2013-46408-R.Galindo, J.; Ruiz Rosales, S.; Dolz Ruiz, V.; Royo Pascual, L.; Haller, R.; Nicolas, B.; Glavatskaya, Y. (2015). Experimental and thermodynamic analysis of a bottoming Organic Rankine Cycle (ORC) of gasoline engine using swash-plate expander. Energy Conversion and Management. 103:519-532. https://doi.org/10.1016/j.enconman.2015.06.085S51953210

Resilient cooling strategies – A critical review and qualitative assessment

The global effects of climate change will increase the frequency and intensity of extreme events such as heatwaves and power outages, which have consequences for buildings and their cooling systems. Buildings and their cooling systems should be designed and operated to be resilient under such events to protect occupants from potentially dangerous indoor thermal conditions. This study performed a critical review on the state-of-the-art of cooling strategies, with special attention to their performance under heatwaves and power outages. We proposed a definition of resilient cooling and described four criteria for resilience—absorptive capacity, adaptive capacity, restorative capacity, and recovery speed —and used them to qualitatively evaluate the resilience of each strategy. The literature review and qualitative analyses show that to attain resilient cooling, the four resilience criteria should be considered in the design phase of a building or during the planning of retrofits. The building and relevant cooling system characteristics should be considered simultaneously to withstand extreme events. A combination of strategies with different resilience capacities, such as a passive envelope strategy coupled with a low-energy space-cooling solution, may be needed to obtain resilient cooling. Finally, a further direction for a quantitative assessment approach has been pointed out

NoWaste: waste heat re-use for greener truck

peer reviewedThe present paper summarizes the key points of the European NoWaste Project, which aims at developing Rankine cycle systems for integration into long-haul trucks with the aim to convert the waste heat of the exhaust gases into useful energy usable in mechanical or electrical form. The first part of the paper describes the ORC system architectures defined for two different truck engines: one with EGR and the other one without EGR. For both engines, different cycle configurations and working fluids are compared in terms of energy performance and technical constraints. For both ORC systems, the paper shows the final technical choices made in terms of main components: boiler, condenser, expander and pump. The second part of the paper presents preliminary experimental results carried out on demonstrators of the two ORC systems. The objectives of these tests were to check the performance announced by the components’ manufacturers. Finally, the last part of the paper compares the cost of both systems

Experimental characterization of a hermetic scroll expander for use in a micro-scale Rankine cycle

This paper presents the results of an experimental study carried out on a prototype of a hermetic scroll expander, integrated into a gas cycle test rig, whose working fluid is HFC-245fa. This system was designed to test only the performance of the expander. It is mainly made up of a scroll compressor, a scroll expander, a heat exchanger and a by-pass valve. The latter is used to adjust the pressure ratio imposed to the expander. The expander is originally a compressor designed for heat pump applications and characterized by a nominal power input of 2.5 kWe. Performance of the expander is evaluated in terms of isentropic effectiveness and filling factor as function of the main operating conditions. The study also investigates the impact of oil mass fraction on the expander performance. Maximum overall isentropic effectiveness of 71.03% is measured, which is partly explained by the good volumetric performance of the machine. Using the experimental data, parameters of a semi-empirical simulation model of the expander are identified. This model is used to analyze the measured performance of the expander. Finally, a polynomial empirical model of the expander is proposed for fast and robust simulations of ORC systems

Friendly simulation of residential heating systems.

Until now, the choice of a heating system is, in most cases, rather intuitive, but not based on significant comparisons among the many options available on the market. Friendly calculation tools are badly needed. A prototype of simulation model is shortly presented in this paper. It is designed as a preliminary design tool, allowing the different partners of a project to evaluate the energy impact of the very first design options: building envelope heat transfer coefficients, glazing areas, orientations, solar factors, ventilation mode, heat emission, distribution, generation and control strategy. The heating demand is calculated hour by hour with consideration to the time variations of inside and outside temperatures and free gains, to the control law and to the heating power actually available. The emitter is a water-ambient heat exchanger. It may have some thermal mass. Two emitters are here proposed: the radiator and the flow heating system. A steady state water distribution model is included in this simulation; it takes heat losses in unheated spaces into account: Three typical heating sources are proposed: classical boiler, condensing boiler and heat pump. All heat generators are here simulated with the help of very simple polynomial (“daughter”) models. The polynomial expressions are fitted on the simulation results obtained with reference (“mother”) models, themselves fitted on experimental data available. Examples of simulation results are presented in the paper

Estimation du profil de la demande énergétique des centres de sante en zones rurales – cas du Bénin

Cet article présente la première partie d'une étude dont l'objectif est de concevoir un système hybride pour des centres de santé ruraux. Il présente l'estimation d'un profil de charge annuel détaillé, estimé à partir d’investigation de plusieurs centres ruraux de santé. Dans la plupart des pays en développement, il y a un manque de données statistiques et d’informations réelles sur la consommation énergétique de la population et des différents types de bâtiments. Ainsi, la méthodologie présentée dans ce travail combine l’enregistrement sur site de la consommation d'électricité, l'estimation statistique des besoins en eau chaude sanitaire (ECS) et la simulation thermique du bâtiment sur TRNSYS 17.Les résultats obtenus permettent de définir un profil détaillé de la charge d'un centre de santé rural avec un pas de temps de 15min à 1 h dont les variations proposent diverses possibilités de scénarios pour l'analyse technicoéconomique. Des informations d'analyses quantitatives et qualitatives sur l'électricité fournie par le réseau sont également présentées.Mots-clés: profil de charge, centre de santé rural, qualité de l’électricité, Trnsys 17, modélisation des bâtiments, coupures d’électricitéEnglish Title: Estimating the energetic load profile of a rural health care centre in rural area of BeninEnglish AbstractThis paper presents the first part of a study which aim is to design a hybrid optimized renewable energy system for rural health care centres supply. It presents the estimation of a detailed yearly load profile estimated from rural centres monitoring. Estimating the demand of energy is an important preliminary step to technico-economic study of hybrid systems. In most developing countries there is a lack of statistical data and retro information on building and population energy consumption. Thus the method presented in this work combined electricity consumption monitoring on site, domestic hot water needs estimation, and thermal building simulations on TRNSYS 17.The obtained results are a detailed profile of the load of a standard rural health care centre with time steps down to 15 min. It shows lots of different variations that while offer various scenarios possibility in technique economic analysis. Quantitative and qualitative analysis information on the grid delivered electricity are also presented.Keywords: Load profile, health centres, grid quality, TRNSYS17, building modelling, load estimation, grid blackout