从上海世博会看新能源科技及其产业化现状和趋势

新能源科技展示已经成为世博科技的亮点。在世博会园区及场馆中,太阳能技术得到充分的展示,江水源热泵和地热泵供能技术凸显了能源技术中低碳环保的理念,储能技术、智能电网技术以及其他新能源技术如风能、生物质能、清洁煤技术等也在不同场馆以不同的形式得以介绍或展示。文章还分析了新能源技术的产业化应用的现状和趋势。     

Cost-optimal energy performance measures in a new daycare building in cold climate

New municipal service buildings must be energy effective, and cost-optimality is one of the criteria for selecting the suitable energy performance improvement measures. A daycare building in a cold climate was studied by means of simulation-based, multi-objective optimisation. Using a genetic algorithm, both target energy use and life-cycle cost of the selected measures were minimised. It was found that extensive insulation of the building envelope is not a cost-optimal method to reduce the daycare building energy use. Improving energy efficiency of the ventilation system, utilising solar energy on-site and employing a light control strategy are preferable ways of improving the building energy performance. Ground-source heat pump is a more cost-optimal heating system for the daycare building than district heating. The cost-optimal sizing of the heat pump is small, only 28% of the required maximum heating power.

Abbreviations: AHU: air handling unit; CAV: constant air volume; COMBI: comprehensive development of nearly zero-energy municipal service buildings; COP: coefficient of performance; DH: district heating; DHW: domestic hot water; EPBD: energy performance of buildings directive; EU: European Union; FINVAC: Finnish Association of HVAC Societies; GSHP: ground-source heat pump; HRU: heat recovery unit; IDA ICE: IDA Indoor Climate and Energy; LED: light-emitting diode; MOBO: multi-objective building optimisation tool; NSGA-II: Non-dominated Sorting Genetic Algorithm II; nZEB: nearly zero-energy building; PV: photovoltaic; TRY: test reference year; VAV: variable air volume; ZEB: zero-energy building     

An evaluation of domestic solar energy potential in Taiwan incorporating land use analysis

Solar energy is widely regarded as a major renewable energy source, which in future energy systems will be able to contribute to the security of energy supply and the reduction of CO₂ emissions. This study combined an evaluation of solar energy resources in Taiwan with land use analysis, which allows the potentials and restrictions of solar energy exploitation resulting from local land use conditions to be considered. The findings unveiled in this study indicate that photovoltaic electricity generation and solar water heating have the potential of producing 36.1 and 10.2 TWh of electricity and thermal energy annually in Taiwan, accounting for 16.3% and 127.5% of the total domestic consumption of electricity and energy for household water heating in 2009, respectively. However, the exploited solar photovoltaic power generation in 2009 accounted for only 0.02% of total potential in Taiwan, while the exploited solar water heating accounted for 11.6% of total potential. Market price and investment incentive are the dominant factors that affect market acceptance of solar energy installation in Taiwan. The administrative barriers to the purchase and transmission of electricity generated from renewable energy sources have to be removed before the potential contribution of solar energy can be realized.     

建筑节能新方向:太阳能光伏-地源热泵系统

减少我国冬季采暖所造成的大气污染,降低供暖系统的能耗,节约能源一直是建筑节能追求的目标.目前太阳能光伏发电已经成为人类利用太阳能的最主要方式之一,地源热泵已被作为一项旨在解决建筑冷热源问题的新技术,日渐受到人们的重视.将光伏转换与热泵循环有机结合在一起,从而形成了太阳能光伏-地源热泵系统.该系统提高了光电转换和光热吸收效率,光电/光热综合利用,极大地提高了单位面积太阳辐照的利用效率,同时可提高热泵系统在寒冷地区运行的适用性;利用光电效应把太阳能中高能带区域的光能直接转化成电能,可大大提高太阳能的可用能效率;在增加能量储存装置和逆变器的条件下,可以使系统脱离公用电网运行,从而增加了系统的适用性和灵活性;与普通的空气源热泵相比,太阳能地源热泵具有较高的热性能,具有一机多用的功效;与建筑物相结合的太阳能热泵系统,可以增加建筑物的隔热效果,起到减少建筑物冷暖负荷的作用,同时可极大地减少环境污染.     

Performance assessment of a Stirling engine plant for local micro‐cogeneration

In this paper, we evaluate the viability of a 9.5‐kW_e wooden pellet‐fueled Stirling engine‐based micro‐cogeneration plant as a substitute for small‐scale district heating. The district heating systems against which the micro‐cogeneration plant is compared are based either on a pellet‐fueled boiler or a ground‐source heat pump. The micro‐cogeneration and district heating plants are compared in terms of primary energy consumption, CO₂ emissions, and feasibility of the investment. The comparison also considers an optimally operated individual 0.7‐kW_e pellet‐fueled Stirling engine micro‐cogeneration system with exhaust gas heat recovery. The study is conducted in two different climates and contributes to the knowledge base by addressing: (i) hourly changes in the Finnish electricity generation mix; and (ii) uncertainty related to what systems are used as reference and the treatment of displaced grid electricity. Our computational results suggest that when operated at constant power, the 9.5‐kW_e Stirling engine plant results in reduced annual primary energy use compared with any of the alternative systems. The results are not sensitive to climate or the energy efficiency or number of buildings. In comparison with the pellet‐fueled district heating plant, the annual use of primary energy and CO₂ emissions are reduced by a minimum of 25 and 19%, respectively. Owing to a significant displacement of grid electricity, the system's net primary energy consumption appears negative when the total built area served by the plant is less than 1200 m². On the economic side, the maximum investment cost threshold of a CHP‐based district heating system serving 10 houses or more can typically be positive when compared with oil and pellet systems, but negative when compared with a corresponding heat pump system. Copyright © 2010 John Wiley & Sons, Ltd.     

Application of a ground source heat pump system with PCM‐embedded radiant wall heating for buildings

This paper deals with the utilization of a renewable energy‐based integrated system with the latent heat storage option for building thermal management systems. Both energy and exergy‐based assessments of the current combined system are conducted. For this purpose, phase change material (PCM)‐embedded radiant wall heating system using solar heating and ground source heat pump (GSHP) is studied thermodynamically. Heat is essentially stored within the PCMs as used in the panels to increase the effectiveness. The stored heat is released when the solar energy is not available. In the thermal energy storage analyses, four different PCMs are considered. The present results show that the overall first ‐ law (energy) and second ‐ law (exergy) efficiencies of the PCM‐free radiant heating system are much lower than the case with the PCM‐embedded radiant heating system. Therefore, it is confirmed that the energy efficiency increases from 62% to 87% while the exergy efficiency rises from 14% to 56% with the option where SP26E PCM is employed accordingly.     

Optimal operation of DC smart house system by controllable loads based on smart grid topology

From the perspective of global warming mitigation and depletion of energy resources, renewable energy such as wind generation (WG) and photovoltaic generation (PV) are getting attention in distribution systems. Additionally, all-electric apartment houses or residence such as DC smart houses are increasing. However, due to the fluctuating power from renewable energy sources and loads, supply-demand balancing of power system becomes problematic. Smart grid is a solution to this problem. This paper presents a methodology for optimal operation of a smart grid to minimize the interconnection point power flow fluctuation. To achieve the proposed optimal operation, we use distributed controllable loads such as battery and heat pump. By minimizing the interconnection point power flow fluctuation, it is possible to reduce the electric power consumption and the cost of electricity. This system consists of photovoltaic generator, heat pump, battery, solar collector, and load. To verify the effectiveness of the proposed system, results are used in simulation presented.     

First and second law analysis of a solar assisted heat pump based heating system

We propose a model for the heating system of an ecological building whose main energy source is solar radiation. The most important component of the heating system is a vapour compression heat pump. Both the first law and the second law were used to analyse the heat pump operation. The state parameters and the process quantities were evaluated by using, as input, the building thermal load. The second law analysis emphasised that most of the exergy losses occur during compression and condensation. Preliminary results show that the photovoltaic array can provide all the energy required to drive the heat pump compressor, if an appropriate electrical energy storage system is provided.     

Potential of power-to-heat from excess wind energy on the city level

ABSTRACT

This study discusses the potential of power-to-heat (P2H) as an effective option to reduce greenhouse gas emissions in the heating sector and energy curtailment. P2H promotes the integration of electricity from renewable energy sources into the power grid by utilizing otherwise unused electricity (excess energy) for space heating. To estimate the contribution of this effect from a techno-economic perspective, a linear problem is defined by minimizing the overall heating costs and solved by an open source model generator. Four different scenarios are modeled on a city level, using real heat demand data from a case study regarding the municipality of Greifswald, a region with dominant wind-energy. Results indicate that district heating networks are an important technology for coupling power and heat to meet CO₂ reduction targets. In addition, further integration of renewable energy is promoted to reduce overall emissions and achieve Germany’s climate protection goals by 2050.     

城市建筑冷热电能源提供模式的探讨

21世纪能源以及环境问题已经成为了各国的头等问题。我国建筑耗能的数字非常惊人：在建造和使用过程中直接消耗的能源占全社会总能耗的20%。根据发达国家的发展经验,这一比例将逐步提高35%左右,建筑能耗极有可能在不远的将来成为我国第一耗能大户。本文介绍了城市建筑中提供冷热电能量的四种方式。结合作者自身能源审计的经验比较了传统的中央空调加锅炉供能系统、分布式三联供系统以及地源热泵、太阳能供能的新能源供给系统的能效与减排量。得出了传统的能源供给系统虽然操作简单但是比较耗能而且排出的有害气体较多,三联供系统受天然气价格影响偏大,太阳能、地热能如不受限制应该尽可能运用的结论。最后笔者提出了我国建筑节能的设计方法以及发展前景。     

The role of district heating in future renewable energy systems

Based on the case of Denmark, this paper analyses the role of district heating in future Renewable Energy Systems. At present, the share of renewable energy is coming close to 20 per cent. From such point of departure, the paper defines a scenario framework in which the Danish system is converted to 100 per cent Renewable Energy Sources (RES) in the year 2060 including reductions in space heating demands by 75 per cent. By use of a detailed energy system analysis of the complete national energy system, the consequences in relation to fuel demand, CO₂ emissions and cost are calculated for various heating options, including district heating as well as individual heat pumps and micro CHPs (Combined Heat and Power). The study includes almost 25 per cent of the Danish building stock, namely those buildings which have individual gas or oil boilers today and could be substituted by district heating or a more efficient individual heat source. In such overall perspective, the best solution will be to combine a gradual expansion of district heating with individual heat pumps in the remaining houses. Such conclusion is valid in the present systems, which are mainly based on fossil fuels, as well as in a potential future system based 100 per cent on renewable energy.     

空气源热泵与燃气锅炉辅助加热太阳能供热水系统的设计和应用

太阳能作为可再生能源,在建筑节能中越来越受到人们的重视.根据工程实例,分析和探讨空气源热泵和燃气锅炉辅助加热太阳能供热水系统的特点,应用范围,工作工况以及运行系统,力求实现太阳能热水器与建筑的优化设计,促进空气源热泵和燃气锅炉辅助加热太阳能热水技术在建筑领域的推广应用.     

Assessment of technical and economical viability for large-scale conversion of single family residential buildings into zero energy buildings in Brazil: Climatic and cultural considerations

This paper addresses the viability of converting single-family residential buildings in Brazil into zero energy buildings (ZEBs). The European Union and the United States aim ZEBs implementation to address ‘peak oil’ and environmental concerns. However, literature shows no agreement on a consensual definition of ZEB. Seeking a Brazilian ZEB definition, this paper addresses PassivHaus and thermal comfort standards for hot climates, source metrics for ZEB, Brazil′s energy mix, residential energy end uses and Brazilian legal framework for residential photovoltaic (PV) generation. Internal Rate of Return for PV systems in two Brazilian cities is calculated under various scenarios. It shows grid parity was reached from April 2012 to November 2012 assuming residential electric tariffs of that period and the financial conditions given by the Brazilian government for the construction of new dams in the Amazon and the lowest rates offered by Brazilian banks to private individuals. Governmental decision to lower electric residential tariffs in November 2012 reduced the scope of grid parity. Later revocation of a tax exemption in April 2013 ended grid parity in Brazil. It concludes, conversely to developed countries, it is the volatile Brazilian energy policy, instead of economical barriers, the main obstacle for ZEB viability in Brazil.     

Determinant factors in site selection for photovoltaic projects: A systematic review

The choice of great places for installation of solar power plants has become a key issue in terms of project planning because of the increased number of investments in the photovoltaic sector. This study is a systematic review of the literature that seeks to identify the determining factors in choosing the best location for solar photovoltaic power plants, through previous research on the application of renewable energy technologies in great contexts of location. Among a total of 130 academic studies filtered by the keywords “photovoltaic energy,” “power plants,” “location,” and “factor” on the bases ScienceDirect, Scopus, Web of Science, and IEEE, a total of 27 studies were identified. These articles were carefully explored, including years of publication, countries of origin, and identification of factors that each author demonstrated. It has been extracted 28 factors, organized in six points of view: socioenvironmental, location, economic, political, climatic, and orographic. It was verified that the determining factors for choosing the best locations are solar irradiation, substation distance, slope, distance of roads, distance from urban areas, and land use. The results of this research may assist academic students and investors in identifying factors that they should consider in their decision making and may also assist in the efficient planning of renewable energy management to ensure the sustainable development of power generation through the photovoltaic source.     

Hydrogen systems for large-scale photovoltaic plants: Simulation with forecast and real production data

The unevenness of solar photovoltaic energy output poses a number of issues that reduce its capability to be considered a reliable substitute for fossil fuels. For instance, solar photovoltaic plants convert and inject energy in the grid during the daytime, but fail to do so during bad weather conditions or at night. Variable weather conditions also render a reliable energy injection planning impossible, causing the photovoltaic power plant output to be most often unpredictable. Furthermore, all the energy converted and immediately injected in the grid poses the risk of creating imbalances in the electric energy distribution lines. A nation-wide energy system characterized by a large penetration of photovoltaic and wind energy sources can therefore be extremely difficult to manage and cannot be considered dependable. The core issue is how to improve the reliability of electricity production from such renewable energy sources.     

寒区太阳能_土壤源热泵系统太阳能保证率的确定

在寒冷地区以太阳能、土壤源作为热泵的低位热源对节约能源、保护环境、开发利用新能源和可再生能源具有重大的意义。文中首次提出了土壤源热泵系统在不同的运焦比下的土训温度场恢复率,并以此为指标,衡量土壤源热泵在各种不同运停比下土壤温度场的恢复程度,确定土训源热泵的最佳运停比及太阳能保证率,从而确定太阳能集热装置的容量。     

水源热泵在空调系统中应用的经济性分析

本文对水源热泵的能耗进行了分析,表明水源热泵机组的性能系数与水源的温度直接相关,讨论了水源热泵在嵊州市空调系统集中供冷供热的可行性,对集中冷热水供水系统夏季空调工况与冬季热泵工况的经济性进行了计算与分析,结果表明,嵊州市利用水源热泵建立集中冷热水供水系统的社会经济效益显著,具有重要的节能与环保意义。     

光伏/光热-地源热泵联合供热系统运行性能研究

为解决太阳电池的发电效率随温度升高而下降以及地源热泵系统供热引起的土壤热失衡问题,以典型居住建筑的光伏/光热-地源热泵（PV/T-GSHP）联合供热系统为研究对象,基于TRNSYS软件,采用土壤温度、地源热泵机组季节能效比、光伏发电效率和太阳能保证率为评价指标,对该联合供热系统进行运行性能分析。研究结果表明：夏热冬冷地区（以长沙为例）太阳能保证率相对较高,PV/T组件面积为满屋顶最大化安装（900 m²）时,第20年末土壤温度相比初始地温仅升高0.8 ℃,热泵机组季节能效比约为5.1,太阳能保证率为97.0%~98.7%;不同气候地区的太阳能保证率与PV/T组件面积和建筑全年累计供热量有关,通过定义单位建筑全年累计供热量PV/T组件面积指标,得到中国不同气候地区的太阳能保证率与该指标的耦合关系,回归方程的决定系数R²为0.983,得出在已知建筑全年累计供热量和太阳保证率设计目标值的条件下所需PV/T组件面积的计算方法。PV/T-GSHP联合供热系统的全年运行能耗显著小于平板太阳能集热器-地源热泵联合系统（最小降幅为沈阳,49.7%）,远小于空气源热泵（最小降幅为石家庄,79.8%）和燃气壁挂炉（最小降幅为沈阳,65.1%）。     

太阳能-空气复合热源热泵热水器的性能模拟与分析

介绍了一种新型太阳能—空气复合热源热泵热水装置(SAS-HPWH)。该装置通过使用独特设计的螺旋翅片蒸发管的平板型集热/蒸发器,可以在不同的天气情况下切换运行太阳能热源热泵模式、太阳能与空气双热源热泵模式和空气源热泵模式,制取生活热水。论文主要针对自行设计的一台150L的SAS-HPWH,建立系统的数学模型,并以太阳能输入比例为准则研究系统的运行模式与特性。模拟结果显示该热水器在不同天气特征情况下可高效率地制造55℃热水。论文还分析了太阳辐射、环境温度以及压缩机的容量对系统特性的影响,提出使用变频压缩机,根据不同的天气情况调节制冷剂流量,进一步提高系统的整体性能。     

Techno-economic analysis of a local district heating plant under fuel flexibility and performance

Brovst is a small district in Denmark. This paper analyses the use of local renewable resources in the district heating systems of Brovst. The present use of fossil fuels in the Brovst district heating plant (DHP) represents an increasing environmental and climate-related load. Therefore, an investigation has been made to reduce the use of fossil fuels for district heating system and make use of the local renewable resources (biogas, solar, and heat pump) for district heating purposes. In this article, the techno-economic assessment is achieved through the development of a suite of models that are combined to give cost and performance data for this district heating system. Local fuels have been analyzed for different perspectives to find the way to optimize the whole integrated system in accordance with fuel availability and cost. This paper represents the energy system analysis mode, energyPRO, which has been used to analyze the integration of a large-scale energy system into the domestic district heating system. A model of the current work on the basis of information from the Brovst plant (using fossil fuel) is established and named as a reference option. Then, four other options are calculated using the same procedure according to the use of various local renewable fuels known as “biogas option,” “solar option,” “heat pump option,” and “imported heat option.” A comparison has been made between the reference option and other options. The greatest reduction in heat cost is obtained from the biogas option by replacing a new engine, where 66 % of the current fuel is substituted with biogas.