Experimental investigation of a reversible heat pump/organic Rankine cycle unit designed to be coupled with a passive house to get a Net Zero Energy Building

This paper presents an innovative reversible Heat Pump/Organic Rankine Cycle (HP/ORC) experimental unit designed to be coupled to a Net Zero Energy Building (connected to a 120 m² thermal solar roof and a ground heat exchanger). The system can operate in three different modes: an ORC mode to produce electricity when a large amount of heat is collected by the solar roof, a direct heating mode using exclusively the solar roof, and a HP mode for space heating during cold weather conditions. This paper describes a comprehensive experimental campaign carried out on a prototype unit using a modified HVAC scroll compressor (4 kWe). From the results, the technical feasibility of the system is demonstrated. A cycle efficiency of 4.2% is achieved in ORC mode (with condensation and evaporation temperature respectively of 25 °C and 88 °C) and a COP of 3.1 is obtained in HP mode (with condensation and evaporation temperature respectively of 61 °C and 21 °C).     

Turbomachinery for small solar power plants

Conversion of solar energy into mechanical or electrical energy in small solar power plants (10–500 kW) requires new design criteria, especially with regard to turbomachinary. The cycles suitable for solar power production are affected by many variable such as kinds of working fluid, range of power and maximum cycle temperature determined by the type of collector. Also, the size of the plant will influence the selection of the various components of the plant, especially that of the turbomachinery. A study of a suitable thermodynamic cycle and working fluid is done for diffèrent ranges of power and temperature. The working fluids considered are steam, toluene, and refrigerant 113 for the Rankine cycle systems and air for gas turbine systems. For Rankine cycles, turbine selection is a problem in the small power range. This is mainly due to the fact, that for high efficiency the enthalpy drop should be as high as possible, and the mass flow rate of the working fluid through the turbine becomes very small. This, in turn, requires high rotational speed, multistaging and partial admission, especially if water is the working fluid. Toluene offers better design criteria for the turbine in the same temperature and power range (50–200 kW). For the very small range (10 kW) refrigerant 113 or similar should be used, otherwise severe design problems with the turbine will occur. In this power range, photovoltaics may also be considered. For high concentration systems with “Brayton cycles” (800–1000°C) only open-cycle gas turbine plants should be used.     

A strategy for the optimization and economic evaluation of an ORC system for energy recovery

Abstract

A strategy for the performance prediction and economic evaluation of an ORC (organic Rankine cycle) system for power conversion is studied. Different assumptions and system boundaries are used to understand the constraints of the boundaries as well as their effects on the evaluation results. A series of methods, including cost estimation, operation’ research, sensitivity analysis and optimal design of heat exchangers, is employed in evaluating this thermal to power conversion system. It is found that the resultant variations in the economic evaluation, no matter what economic index is used, are mostly depending on the input parameters and the unpredictable variables at the preliminary design stage. The analysis strategy, the detailed procedures as well as the computer programs, is presented with a 400°F, 2.5 ×10⁷ Btu/hr flue gas recovery case as an illustration. This study shows a large variation of payback period ranging from 5 to 15 years, depending on different assumptions, operating conditions, and system boundaries. This analysis recommends a more conservative approach to evaluate an energy recovery project to avoid an inappropriate judgement of an engineering design project.     

Development and test of solar Rankine cycle heating and cooling systems

This paper describes the design, fabrication and test of a prototype 63.3 kW (18 ton) solar-powered Rankine cycle heat pump, as well as the assembly and field test of a 63.3 kW (18 ton) solar powered chiller.     

有机朗肯循环的发电系统的实验研究

以低温热蒸汽来模拟废热作为有机朗肯循环(ORC)的热源,建立了以R134a为制冷剂的有机朗肯循环发电系统。通过EES(engineering equation solver)软件对ORC系统进行了数学建模,并将实验与模拟结果进行了比较。结果表明:系统以R134a为工质运行,可以达到8%的发电效率;当膨胀机进口的状态为饱和或者过热时,系统的热效率与发电量都会随着进口压力的增加而增加;系统压力较低的时候,系统的不可逆程度较大,系统效率会有较大损失。     

Line-focusing concentrating solar collector-based power plants: a review

Concentrated solar power (CSP) plant is an emerging technology among different renewable energy sources. Parabolic trough collector (PTC)-based CSP plant, using synthetic or organic oil as a heat-transfer fluid, is the most advanced technology. About 87 % of the operational capacities of CSP plants worldwide are based on PTC technology. Direct steam-generating linear Fresnel reflector (LFR) systems have been developed as a cost-effective alternative to PTC systems. Line-focusing concentrating solar collectors (PTC and LFR), with single-axis tracking, are simple in design and easy to operate. Prior to the detailed design of a CSP plant, it is necessary to finalize type of the solar field, type of the power-generating cycle, overall plant configuration, sizing of the solar field and the power block, etc. The optimal design of a CSP plant minimizes the levelized cost of energy for a given site. In this paper, a detailed review of important design parameters which affect the design of line-focusing concentrating solar collector-based power plants is presented. This includes parameters for solar collector field design, receiver, heat-transfer fluid, thermal energy storage, power-generating cycle, sizing and configuration of the plant, etc. This review may provide a reference for designing CSP plants. Future research directions are also identified.     

Thermal and exergoeconomic analysis of a novel solar driven combined power and ejector refrigeration (CPER) system

In the present study, a novel solar driven combined power and ejector refrigeration system (CPER) of 50 kW power capacity composed of an ORC (organic Rankine cycle) and an ejector refrigeration system is investigated. Solar driven CPER system is composed of two main cycles: collector cycle and refrigeration cycle. The collector cycle is made of a U-tube ETC and circulation pump and the ejector refrigeration cycle consists of generator, turbine, ejector, heat exchanger, condenser, evaporator, expansion valve, and pump. Thermodynamic performance of the proposed CPER system is evaluated and a thermo-economic analysis is conducted using the SPECO (specific exergy costing) method. A parametric study showed the effects of condenser temperature, evaporator temperature, generator pressure, turbine back pressure and turbine extraction ratio. The genetic algorithm optimization analysis is conducted which shows 25.5% improvement in thermal energy, 21.27% in exergy efficiency, and 7.76% reduction in the total cost of the CPER system. The results reveal that the performance of the CPER system is considerably improved at higher temperatures of generator and evaporator.     

The CNPM thermal heat pump. Part 1 — general description and thermodynamic analysis

A research programme, funded by CNR (National Research Council), has been undertaken by CNPM since 1973. The aim of the programme is the construction and testing of a prototype thermal heat pump. The most significant component is an organic Rankine cycle engine, driving the compressor of a heat pump. Since the heat rejected by the engine is supplied to the user — water for domestic heating — the whole system performs as a ‘heat multiplier’, converting the high temperature heat given to the engine into a larger amount of low temperature heat, to be used for domestic heating.In this paper, the selection criteria for the working fluid — a completely fluoro-substituted hydrocarbon — and the main thermodynamic data of both power and heat pump cycles, are discussed; the finally adopted plant configuration is described, with particular emphasis on the influence exterted by the working fluid nature on the heat exchangers and turbo-machinery dimensions and performance. A discussion on the merits of the single fluid solution (ie the same working fluid in the power and the heat pump cycle) and dual fluid solution is also carried out. The feasibility of a low-temperature heat distribution, based on compact-surface, natural-draft convectors, with the relevant advantages on the Rankine and heat-pump cycles, is also investigated.Finally, the expected overal; system performance is given, both at design and part-load conditions. As a premium for the rather complex but efficient thermodynamicscv of the system, significant energy savings are obtained in all situations.     

Thermodynamic optimization of combined power and refrigeration cycle using binary organic working fluid

A combined cycle has been proposed for the production of power and refrigeration simultaneously. The cycle can be driven by low grade heat sources such as solar, geothermal and waste heat sources. In the first part of this paper, a model has been developed to perform a parametric analysis to evaluate the effects of important parameters on the performance of the cycle, which is a combination of Rankine and absorption refrigeration cycle. Propane–decane has been used as an organic dual working fluid. In the second part, multi objective genetic algorithm is applied for Pareto approach optimization of the cycle. There are three important conflicting objectives namely, turbine work (W_t), cooling capacity (Q_c) and thermal efficiency (η_th) which have been selected to find the best possible combination of these performance parameters. Optimization has been carried out by varying turbine inlet pressure, superheated temperature and condenser temperature as design variables. Among optimum design parameters, a trade-off point is selected. Turbine inlet pressure, superheated temperature and condenser temperature are assumed to be 29.5 bar, 410 K and 386.6 K respectively as the values assigned to this point. Furthermore, it has been shown that some interesting and important relationships can be discovered among optimal objective functions and decision variables involved, consequently.     

新型布雷登塔式太阳能热发电系统

太阳能热发电通常以水工质吸热作为第1代,以熔盐吸热作为第2代,以空气、超临界二氧化碳或固体粒子作为介质的布雷登循环系统称为第3代太阳能热发电系统。通过采用空气或陶瓷粒子作为吸热介质,采用干热存储介质（如耐火砖和陶瓷材料等）进行规模化储热,能提高系统效率和降低成本,系统的储热能力可保证电站在任何时候都按照电网调度要求发电。采用标准化模块设计,通过工厂化制作,使电站设计、设备生产、安装、调试和运行都大为简便,储存的热量可用于食品加工、干燥、农业应用等。根据美国能源部的研究,具有储热功能的模块配备小型燃气型透平可实现快速启停,改善电网电压和频率质量。     

Exergy analysis of the active solar distillation systems integrated with solar ponds

Active solar distillation system integrated with solar pond is the green energy system for desalination without negative environmental impact. This clean technology has potential to contribute a lot to water security, sustainable development, and world stability. In this article, results of the energy as well as exergy analysis performed on this novel system integrated with solar pond are presented. This theoretical analysis is carried out in the climatic conditions of New Delhi (India) during a typical summer day. The model and procedures can be helpful in the design, and performance investigation of the actual system anywhere in the world. The daily productivity, energy, and exergy efficiency of the passive solar still are found to be 5 L/m², 38.63 %, and 2.71 %, respectively, corresponding to a sum total of 24.436 MJ/m² day solar energy input in passive mode. With the integration of solar pond in the active solar still, the daily productivity, energy, and exergy efficiency rises to about 9.5 L/m², 46 %, and 14.81 % respectively, for thermal energy input from 100 to 500 W/m² during off-sunshine hours. The further improvement in the performance of the same system is observed if the thermal energy is supplied continuously (24 h) to the solar still in addition to incident solar radiation. The proposed system will meet the demand of freshwater in both rural and urban areas and help in reducing the load of CO₂ emission on the environment, saving high grade energy consumed for desalination through conventional devices and technologies.     

Performance analysis of a combined system for cold and power

This paper presents a theoretical study of a combined thermal system, which combines the Rankine cycle and the ejector refrigeration cycle. This combined cycle produces power and refrigeration simultaneously. The thermal system could use low temperature heat sources. A simulation was carried out to evaluate the cycle performance using several working fluids as R123, R141b, R245fa, R601a and R600a. A one-dimensional mathematical model of the ejector was developed using the equations governing the flow and thermodynamics based on the constant area ejector flow model. The ejector is studied in optimal operating regime. The influence of thermodynamic parameters on system performance is studied. The results show that the condenser temperature, the evaporation temperature, the extraction ratio, the fluid nature and the generating temperature have significant effects on the system performances (the coefficient of performance of the combined cycle and the entrainment ratio of the ejector).     

基于PSO算法优化的热水分流式双级ORC系统

以有机朗肯循环的结构优化为基础,建立了热水分流式双级有机朗肯循环数值模型,以粒子群算法为计算方法分析系统设计时最大净输出功,通过理论分析得到了影响系统净输出功的独立变量为热水经过高压蒸发器时换热后的温度和热水出口温度。结果表明热水分流式双级有机朗肯循环可以对热水进行更好的利用,高压循环蒸发温度随着热水入口温度升高更快;热水在进行分流的过程中随着热水入口温度的升高,分流比下降;热水入口温度更高时采用该系统更有优势。     

全封闭式涡旋膨胀机在车用有机朗肯循环中的特性研究

本文针对中低温余热特性搭建了2kW目标发电量的小型有机朗肯循环发电系统。实验研究了全封闭式涡旋膨胀机在有机朗肯循环系统中的参数特性。通过改变膨胀机进出口的状态,研究了运行压比和转速对于膨胀机单体及系统性能的影响。性能参数主要包括等熵效率、容积系数、循环热效率及循环净功。结果表明:膨胀机运行压比是影响系统性能的重要参数,循环净功随压比的增大而增加,循环热效率及膨胀机的等熵效率随压比变化均存在最优值;考虑内泄漏及摩擦损失等影响,最优运行压比一般应略大于膨胀机设计比;提高膨胀机转速能有效减少内泄漏损失。     

The potential of solar energy use in desiccant cooling cycles

The use of heat produced by solar thermal collectors is an interesting option for thermal driven air conditioning processes. A thermal driven cooling technique which fits well to non-tracking solar collectors is the desiccant cooling technique. Recently several projects have been carried out which focus on the connection of desiccant cooling systems with solar thermal energy for regeneration of the sorbents. This communication deals with three main topics: (1) experiences achieved in a realized system which is coupled to a solar collector are discussed, (2) a new concept is presented, in which a solar air collector is integrated into the desiccant cooling cycle as the only heat source and (3) a comparative study is presented which compares system performance for different system configurations and different climatic situations.     

Modern trends in heat pump development

Modern trends in heat pump development are discussed. Motor/compressor units are now being designed specifically for heat pumps. The use of solar heat, direct fired domestic heat pumps (eg with natural gas), the Stirling engine and Rankine cycle heat pump are being investigated.     

Stirling engine heat pumps

A Stirling engine is a thermal system that may be used to produce power from a high temperature heat source or as a refrigerator and heat pump to deliver energy at a higher temperature than abstracted from the source. A Stirling engine may therefore be used as the driver for natural gas heated air conditioning/heat pump Rankine cycle vapour compression systems or itself be used as the refrigerating/heat pump system requiring an input of work. Two Stirling systems, one acting as the driver, the other as the heat pump may be combined into the Stirling-Stirling or duplex Stirling arrangement. This paper touches briefly on a number of topics about fundamental aspects and recent developments in this field.     

3D‐Printed,All‐in‐One Evaporator for High‐Efficiency Solar Steam Generation under 1 Sun Illumination

Using solar energy to generate steam is a clean and sustainable approach to addressing the issue of water shortage. The current challenge for solar steam generation is to develop easy‐to‐manufacture and scalable methods which can convert solar irradiation into exploitable thermal energy with high efficiency. Although various material and structure designs have been reported, high efficiency in solar steam generation usually can be achieved only at concentrated solar illumination. For the first time, 3D printing to construct an all‐in‐one evaporator with a concave structure for high‐efficiency solar steam generation under 1 sun illumination is used. The solar‐steam‐generation device has a high porosity (97.3%) and efficient broadband solar absorption (>97%). The 3D‐printed porous evaporator with intrinsic low thermal conductivity enables heat localization and effectively alleviates thermal dissipation to the bulk water. As a result, the 3D‐printed evaporator has a high solar steam efficiency of 85.6% under 1 sun illumination (1 kW m^?2), which is among the best compared with other reported evaporators. The all‐in‐one structure design using the advanced 3D printing fabrication technique offers a new approach to solar energy harvesting for high‐efficiency steam generation.