Potential of solar energy utilization in the textile industry — a case study

There is high energy consumption in the industrial sector at low-temperature levels, and solar energy could save a considerable part of this energy. A feasibility study to obtain the potential of solar energy utilization in the textile industry is presented. Two categories were considered in this study. The first category is a preheat solar system that can feed the boiler with hot water. This system can be efficiently utilized in this case because it can operate under different conditions of flow rate and output temperature. The second category is to feed the process of textile dyeing that needs low temperatures (up to 85°C) directly with hot water. In this case, the collector area is limited by the available area in the factory. Economic comparison between the two categories was provided to determine the optimal system that can be used efficiently. The optimum design of the two systems was studied depending on the optimum collector area and flow rate. It was found that the second system is more economic and efficient than the first. The environmental impact of using such a system was studied for different air and water pollutants. Reduction of carbon dioxide emission was found to be the main advantage of using solar energy as a clean energy source.     

Review of brackish water reverse osmosis (BWRO) system designs

Brackish water are any water sources with TDS between 1000 and 15 000 mg/L. Brackish water cannot be consumed by us directly due to its high salinity. According to World Health Organization (WHO), water with salinity below 500 mg/L is acceptable as drinking water. There are quite a large number of research that had been done on BWRO. Each of them has agreed with a common design on optimum BWRO design with a slight modification in order to improve more and make a better BWRO system. BWRO systems which have been tested in real situation agree that the single stage system with module connected to reject water is the most optimum system both economically and environmentally. There is some improvement done to the design by using SWRO membrane at the second stage. This improvement increases recovery rate to about 83% and reduces boron concentration at the same time. Another design is by using hybrid combination of ultra-low and conventional RO membranes. Hybrid improves permeate quality. It is also possible to create a hybrid array by mixing membrane element types within a pressure vessel itself. Co-operating an efficient module arrangement into a complete BWRO system will reduce energy consumption. Energy-recovery device is a component that must be included in any small or large-scale systems. A small-scale RO system, without energy recovery, would typically consume two to three times more energy. This will be more for large-scale systems. While single stage system with module connected to reject water is preferred by researchers who have done real environment testing, simulation prefers to add another membrane to the reject water of the second module. This system is yet to be tested in real environment to prove its standing.     

Prospects of energy savings in the national meat processing factory

This investigation is conducted to examine potential opportunities of energy savings in the meat processing industry. It demonstrates that energy saving can be considered as a major factor to increase profit and competition within this sector. Detailed energy audits were carried out for meat processing equipment in the national factory. This work shows that there are large opportunities of savings which can be achieved by installing the economiser; using compressed air leakage points in the distribution air network, increasing the suction temperature of the high stage compressors as well as recovering of heat in blow down by preheating feed water which will save even more energy. It was found that the refrigeration systems consume more electricity compared to other departments. However, modification of the water pumping system will save an extra amount of energy. Finally, valuable recommendations to factory management are proposed and required additional research, analysis, and data collection are identified.     

Heat pipe based cold energy storage systems for datacenter energy conservation

In the present paper, design and economics of the novel type of thermal control system for datacenter using heat pipe based cold energy storage has been proposed and discussed. Two types of cold energy storage system namely: ice storage system and cold water storage system are explained and sized for datacenter with heat output capacity of 8800 kW. Basically, the cold energy storage will help to reduce the chiller running time that will save electricity related cost and decrease greenhouse gas emissions resulting from the electricity generation from non-renewable sources. The proposed cold energy storage system can be retrofit or connected in the existing datacenter facilities without major design changes. Out of the two proposed systems, ice based cold energy storage system is mainly recommended for datacenters which are located in very cold locations and therefore can offer long term seasonal storage of cold energy within reasonable cost. One of the potential application domains for ice based cold energy storage system using heat pipes is the emergency backup system for datacenter. Water based cold energy storage system provides more compact size with short term storage (hours to days) and is potential for datacenters located in areas with yearly average temperature below the permissible cooling water temperature (∼25 °C). The aforesaid cold energy storage systems were sized on the basis of metrological conditions in Poughkeepsie, New York. As an outcome of the thermal and cost analysis, water based cold energy storage system with cooling capability to handle 60% of datacenter yearly heat load will provide an optimum system size with minimum payback period of 3.5 years. Water based cold energy storage system using heat pipes can be essentially used as precooler for chiller. Preliminary results obtained from the experimental system to test the capability of heat pipe based cold energy storage system have provided satisfactory outcomes and validated the proposed system concept.     

Energy consumption by multi-stage flash and reverse osmosis desalters

Kuwait and most of the Gulf countries, depend mainly on desalted water from the sea for satisfying their fresh water needs. These countries are using the multi-stage flash (MSF) desalting system, as the ‘work horse’ for their water production. This system is less efficient in energy consumption as compared to the reverse osmosis (RO) system. Moreover, large units based on the MSF system have to be combined with steam or gas turbines power plants for better utilization of steam supplied to the MSF units at moderately low temperature and pressure (as compared to steam produced by large steam generators). The value and the cost of the thermal energy supplied to the MSF desalting system depends on the method of supplying this energy. This steam can be supplied directly from a fuel operated boiler or heat recovery steam generator associated with a gas turbine. It can also be supplied from the exhaust of a steam back pressure turbine or bled from condensed extraction steam turbine at a pressure suitable for the desalting process. Any energy comparison should be based on simple criteria, either how much fuel energy is consumed to produce this energy or how much mechanical energy is needed per unit product. The energy consumed in the light of the practice used in most Gulf countries are discussed here. In this study, reference desalting and power plants are used for comparison purposes. This study shows that shifting from MSF desalting system to the RO system can save up to 66% of the fuel energy used to desalt seawater.     

Energy savings in single-purpose desalination systems

In this paper, an energy efficient combination is suggested for single-purpose desalination systems. The present analysis is based on data for existing units known for their reliabilities and high performances. For a specific steam power cycle, the generated power drives a RO, RO/MSF or RO/MEB system. In these combinations, the pretreated hp brine discarded by the RO is introduced as the feed for the distillation unit. Thus, the feed treatment, as well as the feed pumping required, is saved. The TBT and the bottom temperature in the distillation unit are set at 112 and 47°C, respectively.

Results show that, using the same steam power cycle, a water production of 4, 4·26 or 6·2 MGD can be produced if it drives a RO, RO/MSF or RO/MEB system, respectively. Moreover, the energy consumed per unit of fresh water produced (in kJ/kg) is 281, 265 or 182 for the RO, RO/MSF or RO/MEB system, respectively.     

Photovoltaic-powered desalination system for remote Australian communities

This paper reports on the design and successful field testing of a photovoltaic (PV)-powered desalination system. The system described here is intended for use in remote areas of the Australian outback, where fresh water is extremely limited and it is often necessary to drink high salinity bore water. A hybrid membrane configuration is implemented, whereby an ultrafiltration (UF) module is used for removing particulates, bacteria and viruses, while a reverse osmosis (RO) or nanofiltration (NF) membrane retains the salts. The concepts of water and energy recovery are implemented in the design. Field trials, performed in White Cliffs (New South Wales), demonstrated that clean drinking water was able to be produced from a variety of feed waters, including high salinity (3500 mg/l) bore water and high turbidity (200 NTU) dam water. The specific energy consumption ranged from 2 to 8 kW h/m³ of disinfected and desalinated drinking water, depending on the salinity of the feed water and the system operating conditions. The optimum operating pressure when filtering bore water was determined to be in the range 6–7 bar.     

Economic assessment of a two-stage solar organic Rankine cycle for reverse osmosis desalination

The current paper presents the economic evaluation of a two-stage Solar Organic Rankine Cycle (SORC) for using the mechanical energy produced during the thermodynamic process to drive a Reverse Osmosis (RO) desalination unit. The developed integrated system is briefly analysed and the specific fresh water cost, as well as the cost of energy is calculated. The economic assessment results are compared with those obtained from a low-temperature SORC-RO and two alternative variants of PhotoVoltaic RO (PV–RO) systems (with and without batteries). It is found that the critical fresh water cost for the system under consideration is 7.48 €/m³ of permeate water and the cost of energy equals to 2.74 €/kWh, when the water cost is slightly higher than the critical one (meaning 8 €/m³). These values are considered satisfactory enough, in comparison to the other autonomous desalination technologies. Additionally, the specific fresh water cost of the developed technology was calculated to be 6.85 €/m³, being very close to the values of the PV–RO systems. The variant of two-stage SORC significantly improves the efficiency and reduces the cost of the already developed prototype system (single-stage low-temperature SORC for RO desalination), because the specific cost is found to be much lower and taking into consideration its reliability, this technology can constitute an alternative desalination method competitive to the PV–RO on the basis of techno-economic feasibility.     

Energy and exergy analyses on a novel hybrid solar heating,cooling and power generation system for remote areas

In this study, a small scale hybrid solar heating, chilling and power generation system, including parabolic trough solar collector with cavity receiver, a helical screw expander and silica gel–water adsorption chiller, etc., was proposed and extensively investigated. The system has the merits of effecting the power generation cycle at lower temperature level with solar energy more efficiently and can provide both thermal energy and power for remote off-grid regions. A case study was carried out to evaluate an annual energy and exergy efficiency of the system under the climate of northwestern region of China. It is found that both the main energy and exergy loss take place at the parabolic trough collector, amount to 36.2% and 70.4%, respectively. Also found is that the studied system can have a higher solar energy conversion efficiency than the conventional solar thermal power generation system alone. The energy efficiency can be increased to 58.0% from 10.2%, and the exergy efficiency can be increased to 15.2% from 12.5%. Moreover, the economical analysis in terms of cost and payback period (PP) has been carried out. The study reveals that the proposed system the PP of the proposed system is about 18 years under present energy price conditions. The sensitivity analysis shows that if the interest rate decreases to 3% or energy price increase by 50%, PP will be less than 10 years.     

Effect of feed pressure on the performance of the photovoltaic powered reverse osmosis seawater desalination system

This paper describes the potential of the development of a seawater desalination system that combines the technologies of reverse osmosis (RO) and photovoltaic (PV) to deliver 100 m³/day of sweet water. Silicon cells are chosen for the PV array and the polyamide thin-film composite seawater Filmtec membranes are selected for the RO system. The software ROSA is adopted to study the influences of the feed pressure on the performance of the system. It is found that as the feed pressure increases, the specific energy of the plant decreases but the percentage of recovery increases.     

Thermodynamic analysis of combined electric power generation and water desalination plants

The performance of three systems combining reverse osmosis (RO) to produce drinkable water and a steam power plant is modeled and calculated. The RO subsystem incorporates a power recovery unit: a hydraulic turbine in the first two cases and a pressure exchange unit (PES) in the third case. The coupling between the RO and power plant subsystems is only mechanical in the first case (the power plant provides mechanical power to the pumps of the RO subsystem) while in the two other cases the coupling is both mechanical and thermal (part of the heat rejected by the condenser of the power plant is transferred to the seawater). The effects of feed water flow rate and salinity, energy recovery system (hydraulic turbine or pressure exchanger) and operating pressures on the energy and exergy efficiencies and on the permeate quantity and quality are analyzed. Energy and exergy fluxes for all the components, as well as the quantity of drinkable water produced by each of these systems, are also compared for identical operating conditions.     

Simulation and thermoeconomic analysis of different configurations of gas turbine (GT)-based dual-purpose power and desalination plants (DPPDP) and hybrid plants (HP)

This paper contains a simulation and a thermoeconomic analysis of several configurations of gas turbine (GT)-based dual-purpose power and desalination plants (DPPDP): Gas turbine with reverse osmosis (GT+RO), combined cycle with reverse osmosis (CC+RO), combined cycle with multi-effect distillation (CC+MED) and two different hybrid plant (HP) arrangements combining CC, MED and RO (CC+MED+RO, CC+MED+RO_bis). The last two configurations only differ from the feed solution to the MED units (raw seawater or brine coming from the RO discharge). A complete thermodynamic simulation at both design and at part load conditions has been made, as well as an exergy and an exergo-economic (thermoeconomic) analysis of each configuration, in order to compare the evolution of the water and electricity cost for different arrangements. The results show that even for a significantly reduced fuel cost (1.42 $/GJ), the CC is much more profitable than a GT operating in open cycle, with electricity cost values of 1.647 and 2.166 c$/kWh, respectively. As was expected, RO is more efficient and profitable than MED desalination processes, the difference in the obtained desalted water cost being significant. In the hybrid configuration with MED fed by the RO brine discharge, a decrease in the equivalent electrical consumption of nearly 2 kWh/m³ was achieved, but even in this case RO was more efficient (14.15 vs. 4.048 kWh/m³). The evolution of electricity cost in each configuration is more similar at part load operation than at full load, but in the case of water cost, RO is once again more profitable and less sensitive to load variations. Costs given in this paper correspond to investment and fuel costs. Further, profitability and operation strategies of HP, i.e., DPPDP combining distillation and membrane processes, are also analyzed. It is shown that HP can be more profitable than RO plants in the case of increasing the water production capacity of existing DPPDP, because the profit margin of HP remains positive within a substantial range for fuel price and investment costs. The operation strategies of HP were also studied in detail (by means of linear optimization) in order to minimize production costs; and it was concluded that electricity cost minimization gives the same result as the minimization of whole production cost; and water cost minimization could give a lower water cost than in the previous cases, but could lead to prohibitive electricity cost.     

A novel hybrid heat-pipe solar collector/CHP system—Part II: theoretical and experimental investigations

A theoretical analysis has been carried out to investigate the thermodynamic and heat transfer characteristics of a hybrid heat pipe solar collector/CHP system based on the assumption that the system operates on a typical Rankine cycle. Experimental testing of the prototype was also carried out using two types of turbine units. The variation of refrigerant pressures and temperatures, hot water temperatures in the collector and boiler systems, as well as chill water temperatures were recorded. The results were used to estimate the heat from the boiler and the solar collectors, the electricity and hot water generation (indicated as kW energy) from the CHP operation and the gas consumption of the system. The modelling and experimental results were compared for the impulse-reaction turbine system, and a simple analysis of the energy and environmental benefits of the system was carried out. The analysis indicated that the proposed system would save primary energy of approximately 3150 kWh per annum compared to the conventional electricity and heating supply systems, and this would result in reduction in CO₂ emission of up to 600 tonnes per annum. The running cost of the proposed system would also be lower than conventional heating/power systems.     

一种新型太阳能冷库系统的模拟及实验研究

针对太阳能光伏发电技术、需求侧管理（DSM）技术和储能技术提出一种新型太阳能冷库系统。探讨利用冷能储存和光伏发电来减少和转移峰值电力需求、降低电力消耗成本的潜力。建立系统的仿真模型并通过实验进一步修正,结果表明系统在5—8月份基本可节约60%以上的电费,能源节约率最高可达48.38%,相应的电费支付最高可节省65.40%。     

Study of humid air turbine cycle with external heat source for air humidification

In this paper, through introducing an external heat source to the conventional humid air turbine (HAT) cycle, we have studied the performances of the improved humid air gas turbine cycle mainly by exergy analysis method. In order to attain the performance of the humid air gas turbine with external heat source, we compare it with the conventional HAT cycle in detail with different factors such as the pressure ratio, turbine inlet temperature (TIT) and the external circulating water mass flow. The results showed that the specific work of the new system and the humidity ratio of saturator are all increased in some degree. For example, in the same pressure ratio and TIT, when the ratio of the external circulating water mass flow rate with that of the internal water is 0.2, the specific work increases more than 15.2 kJ kg⁻¹a, and the humidity raises at least 2.0 percent points. By introducing the external circulating water into the system, though thermal efficiency of the new HAT cycle is lower than that of the conventional HAT cycle, the exergy efficiency exhibits different results. Generally, when the pressure ratio is over 8, the exergy efficiency for the proposed HAT cycle is higher than the conventional HAT cycle; while less than 8, whether or not the exergy efficiency increases will mainly depend on TIT. In addition, the exergy destructions of components in systems were investigated. Through the comparison of the new system with the conventional HAT cycle, it was found that the exergy loss proportion in combustion declines for the new system, and the proportion of exhaust loss increases. From the viewpoint of total energy system, the HAT cycle with utilization of external heat source is a beneficial way to improve the overall performances of energy utilization. Copyright © 2009 John Wiley & Sons, Ltd.     

Solar powered RO desalination: Investigations on pilot project of PV powered RO desalination system

Water scarcity are serious problem in many areas of the world, such as the Middle East and North African countries (MENA), the Southern European Mediterranean Islands (SEMI) and isolated communities in desert or arid areas of Central Asian countries. One of the promising solutions for this problem is developing of autonomous system of drinking water supply or desalination systems working on RES, particularly solar energy. However, RES especially solar energy potential of the most arid areas is usually high. In addition, the cost of primary fuel is getting up while the need to maintain clean environment is becoming an important issue worldwide [1, 2]. There are a number of desalination methods proposed by scientists and available on the market. Among them, reverse osmosis (RO) is quite suitable for small to medium capacity systems and also has good perspectives for cost reduction and improvement in efficiency in the near future. And a number of research works on solar powered RO systems, from pilot project to industrial scale developed and proposed by researches which can be found from literature. This paper presents a review of the highlights that have been achieved during the last years in solar powered RO desalination. Also proposed the preliminary investigations on developed small scale PV powered RO desalination system, which supposed to be feasible system to use by small farmers in rural areas of Central Asia.     

基于热回收的游泳池热泵除湿供暖系统

基于国内室内游泳馆能耗较高且大部分未设热回收装置的现状，讨论了利用热泵对游泳池供暖除湿的同时实现废热回收的系统设计方案以及回收效果，提出了利用太阳能辅助热泵运行的思想，并给出联合运行的设计方案。从能源利用的角度对二者进行了分析，并与常规的锅炉加冷水机组系统进行了经济性分析和比较，阐明将热泵应用于游泳池除湿供暖，不仅可以有效地节约能源，而且在经济上也是一个非常可行的方案。     

新型太阳能喷射与电压缩联合制冷系统研究

为提高太阳能与辅助能源的综合利用率，提出了一种新型的太阳能喷射式与电压缩式有机结合为一体的联合制冷系统，进而对这种新型联合系统及传统联合系统进行了热力学对比分析，对联合系统太阳能喷射式制冷时最佳发生温度进行了选择，并计算了典型年气象条件下两种联合系统相对于电压缩制冷系统的节能量及节能率。结果表明：两种联合系统相对于电压缩式制冷系统而言都是节能的，但新型联合制冷系统比传统联合制冷系统更节能，更能高效地综合利用太阳能与常规能源：在文中计算条件下，新型联合系统比传统联合系统多节能13．6％。     

Solar space and domestic water heating for West Bank

Solar energy utilization for domestic hot water and house heating is investigated in this paper. The TRNSYS program is used for system simulation. The annual solar fraction of such a system is 0.80 in the West Bank. Solar heating can save up to 28% of the conventional annual heating cost.     

蒸汽发生器供水泵电动机负载特性与能耗分析

针对井楼油田蒸汽发生器供水系统能耗高的实际情况 ,进行了供水泵电动机负载特性分析 ,进行了回流调节和变频调节两种方法下的泵压及功率计算 ,绘制了泵压、电动机轴功率和节电率与需水量之间的关系曲线。计算结果表明 ,需水量在 10～ 18.6 81m3 h范围内 ,用变频器代替回流调节是节电的 ,锅炉需水量越小节电率越大 ;井楼油田锅炉实际需水量为 14.6 0 5m3 h ,节电率为2 4.38% ;需水量在 10～ 18.6 81m3 h范围以外 ,采用变频器调节将更耗电 ,建议改用工频供电。