风光联合制热的系统设计分析

研究日用250 L、温度为55℃热水的某农场发现：单独风力机制热,需要匹配5 kW的风力制热系统;单独太阳能集热,需要匹配20 m²太阳能制热系统,且不能100%全年满足用户需求。太阳能集热的介入,能够有效提高风力制热系统制热效率,提升效果会随着风力机功率的增加而减弱;风力制热的介入,能够有效减小太阳能集热系统水温波动,提高系统稳定性。采用4 m²太阳能集热+4 kW的风力制热系统的风光联合制热系统能够满足用户制热需求,夏秋两季(2 160～6 552 h)内,采用4 m²太阳能集热+2 kW的风力制热就能满足制热需求,将多余的风能用于发电,每年累计发电量为2 193.2 kWh,每年创造1 228.2元的收益。     

基于TRNSYS的太阳能谷电蓄能供热采暖系统性能研究

为了研究太阳能谷电蓄能供热采暖系统运行特性,采用TRNSYS软件建立系统各部件模型,分析了太阳能辐照强度、集热面积和空气流量对系统太阳能保证率的影响,对系统进行优化研究。结果表明：太阳能辐射强度对系统太阳能保证率的影响较大,拉萨全年太阳能保证率波动比上海和北京小;太阳能保证率与集热面积呈正相关;空气流量对太阳能保证率影响较小,当空气流量为40 m³/(h∙m²) 时太阳能保证率最大,相比36 m³/(h∙m²)工况提高了0.26%;选择集热面积为650 m²、最佳空气流量为40 m³/(h∙m²) 的优化系统,相比集热面积为716 m²、空气流量为36 m³/(h∙m²) 工况下的年均太阳能保证率降低了1.22%。本研究可为太阳能谷电蓄能系统的后续研究提供参考。     

平板太阳能集热器冬季运行策略优选实验与集热性能对比研究

为进一步改善平板太阳能集热器(FPSC)冬季水温提升能力的不足，通过搭建的实验平台对FPSC冬季运行策略展开多项实验，分析不同运行模式所对应的集热性能以及适用条件，为平板集热器更高效利用提供参考方案。研究发现：单块FPSC高流速运行的集热效率可达63.74%，各项热性能指标参数优异，但水箱温度偏低；串联、并联系统的水温提升能力较单块模式显著增强，全天温升超过30℃，■效率达到5.15%。其中，并联系统的热效率、对流换热系数、热损失系数分别为51.52%、41.95 W/(m²·K)、4.74 W/(m²·K)，明显优于串联系统的45.33%、38.74 W/(m²·K)、4.81 W/(m²·K)，集热性能更佳；系统冬季低流速运行将出现断流现象，同时水箱内部温度分层明显；高流速运行工况下，降低水箱容积将缩短有效集热时间，无法充分吸收太阳辐照能；增大水箱容积虽能减少集热损失，但系统温升下降造成热能品质降低。     

环境温度对太阳能协同燃煤发电站性能的影响

环境温度不仅影响集热场光热效率,也会通过影响凝汽器背压而影响集热场热电效率,为分析其对太阳能协同燃煤发电(Solar aided coal-fi red power generation,SACPG)系统的性能影响,建立了基于Matlab/Simulink的600 MW太阳能协同燃煤发电系统的机理模型,在性能耦合分析的基础上,研究环境温度对集热器光热、热电和光电效率及协同系统效率和省煤量的影响。研究表明:集热场光电效率随环境温度的升高而先增后减,最佳值是环境温度为0℃时;在完全取代第一段抽汽时,协同系统较原系统效率约提高1.5%,省煤量可超过8.8 g/kWh。     

135 MWe塔式太阳能热发电站全生命周期碳排放研究

以中国西北地区135 MW_e塔式太阳能热发电站(太阳直接辐射量为2015 kWh/m²，年均光电效率为14.9%，储热时长为11.2 h，全生命周期为25年)为研究对象，基于全生命周期评估方法，通过研究边界定义、清单统计，计算得到该电站全生命周期4个阶段的度电碳排放量，并对结果进行分析。结果显示：1)该塔式太阳能热发电站的全生命周期度电碳排放量为22.7 gCO_2e/kWh，处于国内外同类电站度电碳排放量(22～35 gCO_2e/kWh)的低位水平，折合到单位镜场面积的度电碳排放量为1.56×10^-5 gCO_2e/(kWh?m²)。2)在该塔式太阳能热发电站全生命周期4个阶段中，设备、材料制造阶段的度电碳排放量最高(占比约为87.4%)，运营维护阶段次之(占比约为7.2%)，废弃处置阶段位列第3(占比约为3.3%)，建设安装阶段最低(占比约为2.1%)。3)当新增的百兆瓦级塔式太阳能热发电站发电量替代全国火力发电发电量的1%～20%时...     

现有燃煤空冷机组迎峰度夏的增容改造措施

论述了原大同二电厂空冷机组度夏发电出力受阻情况和原因分析,介绍了通过增容改造使空冷机组发电能力增加60 MW,发电煤耗下降20g/kWh的情况.     

太阳能-生物质能联合供暖系统研究

为研究太阳能-生物质能联合供暖系统的供暖效果,通过正交实验设计了多种工况,并利用TRNSYS软件对不同工况进行模拟计算得出了最优工况,按照最优工况参数进行实验研究。结果表明：在集热器面积21 m²、生物质锅炉容量10 kW、集热水箱容积1.9 m³、谷电蓄热水箱容积1 m³的工况下,联合供暖系统具有良好的热舒适性,系统平均供热效率为68.70%。     

无盖板型水冷式PV/T模块光电/光热综合性能实验研究

无盖板PV/T组件相比于盖板式PV/T组件有更高的光电转换效率,在电能输出方面的优势明显。基于此,提出一种无盖板型水冷式PV/T模块,并搭建由光伏对比模块、水冷式PV/T模块以及无冷却水循环的PV/T对比模块构成的实验平台开展对比实验,研究温度、流量对无盖板PV/T模块电、热转换效率的影响。结果表明,在水冷作用下,PV/T模块的光伏组件温度显著降低,与PV/T对比模块相比发电效率提升11.54%;环境平均温度为21.7 ℃、平均辐照度650 W/m²的测试条件下,流量0.12 m³/h时模块的电效率为17.44%,热效率为19.80%,综合效率达到65.69%,考虑到循环泵消耗的电能,表面积1.93 m²的水冷式PV/T模块全天可存储有效能3.72 MJ。     

不同装机容量下S-CO2塔式太阳能热发电系统的热力及经济性能分析

建立超临界CO₂布雷顿循环塔式太阳能热发电系统的热力性能和经济性能模型,比较不同装机容量下系统的年均效率,分析系统中各项成本占比及其随容量增长的变化规律,提出进一步降低发电成本的方法。结果表明,主要受镜场效率的影响,系统年均效率随装机容量增加先升后降,峰值为20 MW时的17.4%。发电成本随装机容量的增加而减小,由1 MW时的0.477 美元/kWh降至100 MW时的0.125 美元/kWh。减小镜场和储热的投资成本是降低大规模电站发电成本的关键。     

300 MW级ACC机组冷端提效技术及方案研究

直接空冷(以下简称ACC)机组在夏季高温时段背压升高且变幅较大,不能满负荷运行,需采用尖峰冷却技术降低背压。基于此,提出零水耗、近零传热端差的蓄冷式冷端提效技术,以某电厂330 MW直接空冷机组为对象,对其加装蓄冷式冷端提效系统的热力性能进行研究分析。结果表明,高温时段掺喷前背压降低6.7～9.9 kPa,对应的煤耗降为5.36～7.92 g/kWh;掺喷蓄冷水后背压继续降低2.2～3.3 kPa,对应的煤耗降为1.76～2.64 g/kWh,2个部分背压降之和在8.9～13.2 kPa,对应的煤耗降为7.12～10.56 g/kWh。低温时段使用一半间接空冷单元,抽汽量减半,背压降低1.86～3.2 kPa,对应的煤耗降为1.49～2.56 g/kWh,实现了尖峰冷却目的。     

Evaluation of CPC-collector designs for stand-alone, roof- or wall installation

An asymmetrically truncated non-tracking compound parabolic concentrator type collector design concept has been developed. The collector type has a bi-facial absorber and is optimised for northern latitudes. The concept is based on a general reflector form that is truncated to fit different installation conditions. In this paper collectors for stand-alone, roof and wall mounting are studied. Prototypes of six different collectors have been built and outdoor tested. The evaluation gave high annual energy outputs for a roof mounted collector, 925 MJ/m², and a stand-alone collector with Teflon, 781 MJ/m², at an operating temperature of T_op = 75 °C. A special design for roofs facing east or west was also investigated and gave an annual energy output of 349 (east) and 436 (west) MJ/m² at T_op = 75 °C. If a high solar fraction over the year is the objective, a load adapted collector with a high output during spring/fall and a low output during summer can be used. Such a collector had an output of 490 MJ/m² at T_op = 75 °C. Finally a concentrating collector for wall mounting was evaluated with an estimated annual output of 194 MJ/m² at T_op = 75 °C. The concentrator design concept can also be used for concentrators for PV-modules.     

Low-cost green building practice in China: Library of Shandong Transportation College

This paper introduces the design idea and technique utilized in the Library of Shandong Transportation College, which ranked 1st in the 2nd National Green Buildings Innovation Award in China in March 2007 due to its low cost and climate-oriented green strategy during its design and construction phase, including land saving, energy efficiency, water conservation, and so on. Originally, the place was a landfill site with an odor pool. After reconstruction, it was changed into the construction site of the library with an area of 7000m² and a scenery pond. With the integrated use of passive shading, daylighting, ventilation with atriums, high-insulation materials, underground duct ventilation, and the substitution of cooling tower with the pond water, the HVAC load design indexes are 59 W/m² and 21.8 W/m² for space cooling and heating, respectively, much lower than the newly issued Chinese energy efficient design code for public buildings. Moreover, a set of measures is utilized for water conversation, material saving, and improvement of indoor environmental quality. After three years of operation, the real effect has been validated by electricity meter and field measurement. The total initial cost for the building with the above mentioned integrated technologies was only RMB 2150 per square meter, which was worth spending in China due to the climatic adaptability and the relative low cost.     

低低温电除尘及高效电源协同烟气处理技术的应用

为研究低低温电除尘及高效电源协同烟气处理技术的应用效果,以一循环流化床锅炉为研究对象,通过试验方法,对协同烟气处理技术投运前后烟气中的粉尘颗粒特性及排放质量浓度进行了测量及对比,并对该技术投运后的经济性进行了分析。结果表明:协同烟气处理技术投运后,机组排放的粉尘质量浓度由49.5 mg/m³降低至10.7 mg/m³,可显著提高除尘器的除尘效率;可降低机组供电标煤耗2.835 g/(kW·h),年节煤量1473.5 t;可进一步减少CO₂,SO₂,NO_x及粉尘等污染物的排放;可节约用电160 kW·h/h,每年节约电量6.16×10⁵ kW·h。     

Statistical analysis of residential building energy consumption in Tianjin

To analyze the effect of energy conservation policies on energy consumption of residential buildings, the characteristics of energy consumption and indoor thermal comfort were investigated in detail in Tianjin, China, based on official statistical yearbook and field survey data. A comprehensive survey of 305 households indicates that the mean electricity consumption per household is 3215 kWh/a, in which annual cooling electricity consumption is 344 kWh/a, and the mean natural gas consumption for cooking is 103.2 m³/a. Analysis of 3966 households data shows that space heating average intensity of residential buildings designed before 1996 is 133.7 kWh/(m²·a), that of buildings designed between 1996 and 2004 is 117.2 kWh/(m²·a), and that of buildings designed after 2004 is 105.0 kWh/(m²·a). Apparently, enhancing the performance of envelops is effective in reducing space heating intensity. Furthermore, the results of questionnaires show that 18% of the residents feel slightly warm and hot respectively, while 3% feel slightly cold in winter. Therefore, the electricity consumption in summer will rise for meeting indoor thermal comfort.     

Effect of economic parameters on power generation expansion planning

The increasing consumption of electricity within time forces countries to build additional power plants. Because of technical and economic differences of the additional power plants, economic methodologies are used to determine the best technology for the additional capacity. The annual levelized cost method is used for this purpose, and the technology giving the minimum value for the additional load range is chosen. However, the economic parameters such as interest rate, construction escalation, fuel escalation, maintenance escalation and discount factor can affect the annual levelized cost considerably and change the economic range of the plants. Determining the values of the economical parameters in the future is very difficult, especially in developing countries. For this reason, the analysis of the changing rates of the mentioned values is of great importance for the planners of the additional capacity.In this study, the changing rates of the economic parameters that influence the annual levelized cost of the alternative power plant types are discussed. The alternative power plants considered for the electricity generation sector of Turkey and the economic parameters dominating each plant type are determined. It is clearly seen that the annual levelized cost for additional power plants varies with the economic parameters. The results show that the economic parameters variation has to be taken into consideration in electricity generation planning.     

A water requirement model for salt gradient solar ponds

A model for predicting the salt gradient solar pond (SGSP) area that could be maintained with a given water supply is presented together with several specific applications. For example, based on 30-year average water flows, the model predicts that 1.93 × 10⁹ m² (477,000 acres) of solar ponds, 1.02 × 10⁹ m² (253,000 acres) of evaporation ponds to recycle salt, and 0.51 × 10⁹ m² (125,000 acres) of freshwater storage reservoirs could be maintained at the Great Salt Lake of Utah. Water use requirements per unit of electrical energy from solar ponds are calculated as 600,000 m³/MW·yr. This is roughly 30 times the water evaporated per unit of electrical energy from coal-fired generating plants using wet cooling towers, but substantially less than water evaporation losses per unit of electrical energy produced from typical hydropower dams and reservoirs. It is concluded that water use requirements for solar ponds, although not necessarily prohibitive, are substantial; and in many locations may be the physical factor that limits solar pond development.     

Realistic generation cost of solar photovoltaic electricity

Solar photovoltaic (SPV) power plants have long working life with zero fuel cost and negligible maintenance cost but requires huge initial investment. The generation cost of the solar electricity is mainly the cost of financing the initial investment. Therefore, the generation cost of solar electricity in different years depends on the method of returning the loan. Currently levelized cost based on equated payment loan is being used. The static levelized generation cost of solar electricity is compared with the current value of variable generation cost of grid electricity. This improper cost comparison is inhibiting the growth of SPV electricity by creating wrong perception that solar electricity is very expensive. In this paper a new method of loan repayment has been developed resulting in generation cost of SPV electricity that increases with time like that of grid electricity. A generalized capital recovery factor has been developed for graduated payment loan in which capital and interest payment in each installment are calculated by treating each loan installment as an independent loan for the relevant years. Generalized results have been calculated which can be used to determine the cost of SPV electricity for a given system at different places. Results show that for SPV system with specific initial investment of 5.00 $/kWh/year, loan period of 30 years and loan interest rate of 4% the levelized generation cost of SPV electricity with equated payment loan turns out to be 28.92 ¢/kWh, while the corresponding generation cost with graduated payment loan with escalation in annual installment of 8% varies from 9.51 ¢/kWh in base year to 88.63 ¢/kWh in 30th year. So, in this case, the realistic current generation cost of SPV electricity is 9.51 ¢/kWh and not 28.92 ¢/kWh. Further, with graduated payment loan, extension in loan period results in sharp decline in cost of SPV electricity in base year. Hence, a policy change is required regarding the loan repayment method. It is proposed that to arrive at realistic cost of SPV electricity long-term graduated payment loans may be given for installing SPV power plants such that the escalation in annual loan installments be equal to the estimated inflation in the price of grid electricity with loan period close to working life of SPV system.     

Levelized cost of storage — Introducing novel metrics

The increasing share of variable renewable generation capacity leads to a growing interest in electricity storage technologies and a summarizing cost metric to analyze the economic viability of such electricity storage units. For conventional generation technologies, the levelized cost of electricity (LCOE) is a well-known metric. In the context of electricity storage however, such LCOE-like metrics are only limitedly applicable as the finite energy storage capacity can limit the charge and discharge scheduling decisions of the storage operator. In addition, the “fuel”, i.e., charged electricity, and “generated electricity”, i.e., discharged electricity, is one and the same commodity which provides the opportunity to use an adapted levelized cost metric. This work analyzes three different levelized cost metrics and their application to electricity storage units used for electric energy arbitrage. The strengths and shortcomings of these storage cost metrics are analyzed in order to determine how they can be applied correctly. This analysis results in the following recommendations. First, it is recommended to use a levelized cost metric in combination with an analysis of a representative price profile upon which the storage operator will act. This allows a more accurate estimation of the number of charging and discharging hours and the associated charging cost and discharging revenue, given the energy storage capacity constraints of the storage unit. Second, when a number of different representative price profiles, hence with different charging costs, is available, it is recommended to use a cost metric which is independent of the charging cost as this single metric can be compared to each price profile, thereby facilitating the interpretation of the results. The results and conclusions from this work provide a framework on how to use levelized cost metrics in the context of electricity storage. Such metrics may help policy makers and investors in prioritizing energy storage investment decisions.     

Combined heat and power generation via hybrid data center cooling-polymer electrolyte membrane fuel cell system

Although there has been a lot of waste heat utilization studies for the air-cooled data center (DC) systems, the waste heat utilization has not been studied for the liquid-cooled DC systems, which have been rapidly gaining importance for the high-performance Information and Communication Technology facilities such as cloud computing and big data storage. Compared to the air-cooled systems, higher heat removal capacity of the liquid-cooled DC systems provides better heat transfer performance; and therefore, the waste heat of the liquid-cooled DC systems can be more efficiently utilized in the low-temperature and low-carbon energy systems such as electricity generation via polymer electrolyte membrane (PEM) fuel cells. For this purpose, the current study proposes a novel hybrid system that consists of the PEM fuel cell and the two-phase liquid-immersion DC cooling system. The two-phase liquid immersion DC cooling system is one of the most recent and advanced DC cooling methods and has not been considered in the DC waste heat utilization studies before. The PEM fuel cell unit is operated with the hydrogen and compressed air flows that are pre-heated in the DC cooling unit. Due to its original design, the hybrid system brings its own original design criteria and limitations, which are taken into account in the energetic and exergetic assessments. The power density of the PEM fuel cell reaches up to 0.99 kW/m² with the water production rate of 0.0157 kg/s. In the electricity generation case, the highest energetic efficiency is found as 15.8% whereas the efficiency increases up to 96.16% when different multigeneration cases are considered. The hybrid design deduces that the highest exergetic efficiency and sustainability index are 43.3% and 1.76 and they are 9.4% and 6.6% higher than exergetic and sustainability performances of the stand-alone PEM fuel cell operation, respectively.