Development of the typical meteorological database for Chinese locations

The typical meteorological database for 57 Chinese locations was developed for building simulations and air-conditioning design. The database consists of three parts: the typical meteorological years (TMY), the typical meteorological days (TMD) and the design temperature and humidity (DTH). The typical meteorological year (TMY) is the main part of the database. Because there are not data on solar radiation in the observations, a method to estimate solar radiation with dry bulb temperature difference, relative humidity, total cloud cover and wind speed was developed. Methodologies of interpolations were developed to produce 1 h data with the 3 h data. The global solar radiation on the horizontal surface was separated into direct and diffuse components with the Gompertz function. The typical meteorological day (TMD) consists of the monthly average values of dry bulb temperature, solar radiation, relative humidity, etc. for each hour of the day. The design temperature and humidity (DTH) was developed for the purpose of air-conditioning design. The frequencies of 2.5% and 5.0% were selected to decide the design temperature and humidity for the 57 Chinese locations.     

Efficiency analysis of a solar photovoltaic array coupled with an electrolyser power unit: a case study

Hydrogen as an energy carrier is one of the most potential candidates for clean energy and can be produced by water electrolysis. The use of 10?kW photovoltaic arrays for supplying a 5?kW electrolyser which consists of 10 series-connected electrolyser stacks and a 28% alkaline (KOH) solution electrolyte has been investigated at the Taleghan renewable energies site in Iran. The hydrogen produced by the electrolyser provides energy for the 1?kW polymer electrolyte membrane fuel cell, which meets the load when the solar energy is insufficient. Variations of the solar radiation intensity, the hydrogen production rate, the solar hydrogen efficiency and the overall efficiency of the solar hydrogen energy unit were monitored in detail. The overall energy efficiency was found to range from 0.93% to 5.01%. The obtained results demonstrate the great potential of such a power system for producing and storing energy in a solar-belt country like Iran.     

典型气象年和典型代表年的选择及其对建筑能耗的影响

介绍了典型气象年和典型代表年的选择原理和几种常见的选择方法。不同的方法考虑了不同气象参数的加权因子和气象数据的连续性。介绍了将太阳辐射总量分为太阳直射辐射量与太阳散射辐射量的应用模型,并依据香港的气象数据,分别计算选出了香港的典型气象年与典型代表年。为了验证不同方法计算出的典型气象年与典型代表年对研究对象、系统的影响,作了一个实例建筑物能耗动态模拟。结果表明,不同典型气象年对模拟结果的影响偏差较小,而典型代表年的影响较大;选择合适方法计算的典型气象年对保证模拟评估结果的正确性具有重要意义。     

建筑节能分析太阳总辐射模型研究综述

太阳辐射是建筑节能分析的重要基础气象参数,实测数据远远不能满足需求,理论计算是目前获取辐射数据的主要途径。将常用水平面太阳总辐射模型归纳为气象参数、空间插值和基于DEM三类,详述了各自的原理和计算方法。对三类模型在建筑节能分析中的适用性进行了分析,展望了建筑节能分析用太阳辐射模型的发展趋势:气象参数模型与DEM模型的融合。     

Potential for a Danish power system using wind energy generators,solar cells and storage

Some overall properties of a power system in a northern climate based mainly upon renewable energy are studied.

The power system consists of wind energy generators and solar cells in combination with a storage system and a back-up system. The type of power plants constituting the back-up system are not specified. The back-up system could be used to generate power only when the rest of the system is unable to cover the load. The predicted performance of the solar/wind power system is calculated on the basis of hourly meteorological data measured in Denmark during the years 1959 to 1972.

It has been established from this data that to maximise the fraction of annual load covered by solar and wind energy the ratio of solar to wind production capacity is approximately 40% solar to 60% wind. With only small changes in the energy provision, however, the ratio could be varied between 20:80 and 60:40.

The saving in energy resulting from provision of various storage capacities has been studied. This saving will be negligible if less than half of the annual load is covered by the solar/wind power system. For a solar/wind power system with a production capacity of 1.25 times the annual load the marginal energy saving effect of a storage system is reduced by a factor of 10 when the storage capacity is increased from 0 to 24 hours. The marginal costs of producing the electricity rise steeply when more than about 80–90% of the load is to be covered on the basis of renewable energy. Finally it is shown that when 80% of the load is covered by renewable energy the storage capacity should not exceed 40 hours.     

室外气温与太阳辐射的随动性关系研究

室外气温与太阳辐射强度之间存在某种随动关系,以中国南方13个典型城市气象数据为依据,通过回归分析方法,得到了太阳辐射与地表温度的动态拟合关系及地气温差随时间变化的动态拟合关系,各拟合公式相关系数R2均在0.97以上,说明拟合结果能显著的反映数据点的变化规律,进而建立了室外气温与太阳辐射强度的随动性关系。结果表明:高原地区,太阳辐射是室外气温与时间的一次函数;平原地区,太阳辐射是室外气温与时间的对数函数。对建筑冷负荷计算提供简便的方法,同时,也为太阳辐射强度与建筑冷负荷的随动性关系及太阳能空调的适宜性研究提供科学依据。     

天津地区太阳能-土壤源复合式热泵系统性能研究

北方某些地区南于冷热负荷的不平衡性,单一的土壤源热泵系统受到限制。太阳能辅助土壤源热泵系统是一种有效利用可再生能源的系统形式。本文对天津地区太阳能辐射情况、建筑全年逐时冷热负荷量及复合热泵系统的制热机组效率进行研究,分析在天津地区太阳能-土壤源复合热泵系统的节能性。     

New correlations for estimation of monthly average daily solar radiation on a horizontal surface using meteorological data

This study deals with the estimation of monthly average daily global solar radiation incident on a horizontal surface at a location using meteorological data for different cities of Andhra Pradesh state. The regression equations of two types of models are developed for various locations of the state having varied climatic regions using measured meteorological parameters obtained from different measuring stations. Parameters such as the latitude and height of the location, maximum and minimum temperature and relative humidity are considered to develop linear and quadratic regression equations to estimate the monthly average daily global radiation. The estimated values are compared with measured data and with other theoretical models in terms of mean percent errors calculated using recognised statistical criteria of MBE, MABE, MPE and RMSE. The proposed quadratic model performs better than the proposed linear models and shows good agreement with the long-term pyranometer data of various locations with a deviation of less than 10%. In comparison with other theoretical models presented so far, the suggested models are expected to perform with a higher degree of accuracy.     

A simple model for assessing the energy performance of windows

A simple model for the annual energy balance of the window taking solar radiation and heat losses into consideration has been further developed and analysed. Hourly meteorological data for the solar irradiation and the outside temperature are used together with the optical and thermal performance of the window to evaluate the net energy heat flow through a window. The model renders a very simple way to compare different advanced windows in different geographical locations, orientations and buildings using basically only the balance temperature as building input. The energy balance and the cost efficiency for several glazing combinations are evaluated for buildings with different balance temperatures in a typical mid-Swedish climate. This model has a potential to be used for energy rating of windows.     

太阳辐射直散分离模型比较研究——以北京地区为例

在建筑能耗模拟与太阳能建筑系统设计中,逐时的太阳直射和散射气象数据是最重要的基本参数。由于中国辐射观测数据的缺失,逐时直射和散射数据很难获得。很多学者对此进行了研究,提出了数十种直散分离模型。采用北京地区2009年—2011年3年太阳总辐射和散射实测数据,选取Erbs模型、Orglill模型、清华大学随机气象模型、宇田川光弘模型、张晴原模型5个代表性的直散分离模型进行计算验证,分析比较了实测数据和计算数据之间的相关系数R、均方根误差RMSE和相对误差RE,得出晴空指数Kt可以作为最主要的影响因子,Erbs模型预测散射的准确率最高,其次为张晴原模型和Orglill and Hollands模型。     

Energy absorbing materials used in solar still for enhancement in distillate output: a review

Solar energy is an abundant and secure source of vitality and thus is described as one of the most promising alternative energy options. Nevertheless, solar energy is intermittent in nature as there is no sun at night. Its total availability value is seasonal and is hooked on the meteorological conditions of locations. Hence, solar energy presents an unsteady energy resource. So, thermal energy storage will be necessary to save the available solar energy at a period of no load or when excessive solar energy is available, and to make up for the shortage of energy when the load is in need of energy. This article reviews the different energy storage materials tried by various researchers to improve the distillate output of solar stills.     

气象参数对成都地区办公建筑能耗的影响及预测

气象参数是影响建筑热环境和供暖空调能耗的主要因素之一。基于成都地区1971—2000年共30a的历史观测数据,生成了建筑能耗模拟软件EnergyPlus所需要的逐时气象数据文件。比较分析了该地区30a干球温度、太阳辐射等各气象参数月均值的变化,模拟分析了该地区建筑的采暖、制冷及总能耗,利用多元回归建立了建筑能耗与气象参数之间的关系式,并检验了该关系式的准确性。结果表明:成都地区办公建筑能耗变化与各气象参数没有呈现明显的规律性;建筑月总能耗与各气象参数呈纯二次多项式关系,月采暖能耗、月制冷能耗与各气象参数呈交叉二项式关系;建筑月能耗回归模型能够较准确地预测建筑月能耗与各气象参数的关系,且月采暖能耗和月制冷能耗回归模型预测的准确性优于月总能耗模型。     

建筑负荷预测中太阳辐射透过窗户引起的冷负荷

通过对建筑物玻璃窗所受太阳辐射得热的性能分析,建立了太阳辐射得热模型;根据《民用建筑热工设计规范》中划分的5个建筑热工分区,建立了典型玻璃窗的太阳辐射得热系数（SHGC）数据库,由此构建了透过玻璃窗的瞬时太阳辐射得热模型。参考DeST中的家具平板模型,建立了玻璃窗的室内蓄热平板模型,通过模型将太阳辐射得热量转化为瞬时冷负荷,并与相同条件下冷负荷系数法中的透过玻璃窗的日射得热形成冷的负荷进行对比,其相对误差不超过20％,满足城市规划阶段负荷预测的要求。从而为解决太阳辐射透过玻璃窗形成的冷负荷提供了一个新的思路,为修正用于区域能源规划中建筑负荷预测用的负荷因子模型提供了一个实用方法。     

Renewable energy potential and adoption of renewable portfolio standards

Thirty states have adopted renewable portfolio standards (RPSs) that set targets for renewable energy generation by mandating electric power utilities obtain a minimum percentage of their retail load from renewable sources. To date, a number of studies have consistently found that political and economic factors impact RPS adoption. Studies have also examined the impact of renewable energy potential in a state on the probability of RPS adoption, but results have largely been statistically weak and inconclusive. After controlling for political and economic factors, we estimate that a one standard deviation increase in wind potential is associated with an approximately 4.2 percentage point increase in the probability of having an RPS, and a one standard deviation increase in solar potential is associated with a 6.1 percentage point increase in the probability of having an RPS.     

Multi-step-ahead forecasting of daily solar radiation components in the Saharan climate

ABSTRACT

Accurate estimation of renewable energy sources plays an important role in their integration into the grid. An unexpected atmospheric change can produce a range of problems related to various solar plant components affecting the electricity generation system. Global solar radiation (GSR) assessment has been increased in the past decade due to its important use in photovoltaic application. In this paper, we propose the use of machine learning-based models for daily global and direct solar radiation forecasting in a semi-arid climate, using a combination set of meteorological parameters on a horizontal surface in the Ghardaïa region. The models are presented and implemented on 3-year measured meteorological data at Applied Research Unit for Renewable Energies (URAER) at Ghardaïa city between 2014 and 2016. The results show that both MLP and RBF models perform well for three-step-ahead forecasting with a slight improvement in MLP models in terms of statistical metrics.     

Solar disinfection (SODIS): simulation of solar radiation for global assessment and application for point-of-use water treatment in Haiti

Haiti and other developing countries do not have sufficient meteorological data to evaluate if they meet the solar disinfection (SODIS) threshold of 3-5 h of solar radiation above 500 W/m2, which is required for adequate microbial inactivation in drinking water. We have developed a mathematical model based on satellite-derived daily total energies to simulate monthly mean, minimum, and maximum 5-h averaged peak solar radiation intensities. This model can be used to assess if SODIS technology would be applicable anywhere in the world. Field measurements were made in Haiti during January 2001 to evaluate the model and test SODIS efficacy as a point-of-use treatment option. Using the total energy from a measured solar radiation intensity profile, the model recreated the intensity profile with 99% agreement. NASA satellite data were then used to simulate the mean, minimum, and maximum 5-h averaged peak intensities for Haiti in January, which were within 98.5%, 62.5%, and 86.0% agreement with the measured values, respectively. Most of the discrepancy was attributed to the heterogeneous nature of Haiti's terrain and the spatial resolution of the NASA data. Additional model simulations suggest that SODIS should be effective year-round in Haiti. Actual SODIS efficacy in January was tested by the inactivation of total coliform, E. coli, and H2S-producing bacteria. Exposure period proved critical. One-day exposure achieved complete bacterial inactivation 52% of the time, while a 2-day exposure period achieved complete microbial inactivation 100% of the time. A practical way of providing people with cold water every morning that has undergone a 2-day exposure would be to rotate three groups of bottles every morning, so two groups are out in the sun and one is being used for consumption.     

水平与垂直遮阳效果的解析研究

采用透光计算的方法,以深圳地区为研究对象,从直射、散射和总辐射的角度进行了水平和垂直遮阳系数的计算,分析了不同朝向水平、垂直遮阳装置的全年遮阳特性,得到了冬、夏季遮阳系数计算公式的回归系数,并与采用能耗计算方法得出的结果进行比较分析。结果表明,直射辐射遮阳系数和总辐射遮阳系数由于全年不同季节直射、散射所占比例不同而产生不同的变化趋势,利用透光计算方法和能耗计算方法得到的遮阳系数有较好的一致性,并发现垂直遮阳不宜作为东西向遮阳方式。     

Soft computing for solar radiation potential assessment in Algeria

ABSTRACT

Precise estimation of solar radiation is a highly required parameter for the design and assessment of solar energy applications. Over the past years, many machine learning techniques have been proposed in order to improve the forecasting performance using different input attributes. The aim of this study is the forecasting of one day ahead of horizontal global solar radiation using a set of meteorological and geographical inputs. In this respect, the Gaussian process regression methodology (GPR) and least-square support vector machine (LS-SVM) with different kernels are evaluated in order to select the most appropriate forecasting model. In order to assess the proposed models, the southern Algerian city, Ghardaia regions, was selected for this study. A historical data of five years (2013–2017) of meteorological data collected at Renewable Energies (URAER) in Ghardaia city are used. The achieved results demonstrate that all the proposed models give approximately similar results in terms of statistical indicators. In term of processing time, all the models showed acceptable computational efficiency with less computational costs of the GPR model among all machine learning models.     

Prediction of solar heat gain of double skin facade windows

A linear model involving the solar heat gain coefficient and U value is often used to calculate the solar heat gain of traditional windows; however, it is not known if such linear model is applicable to double skin facades, which is typically featured by ventilated cavity and often with blinds inside. This paper reports on an experimental investigation into the relation between the two coefficients and the energy gain by a double skin facade without blinds. A small-scale solar calorimeter was constructed to measure the energy gain of a double skin facade window about 1.1 m high. Four tests with solar radiation intensity ranging from 205 to 793 W/m² showed that the energy gain can be represented by such linear model. The solar heat gain coefficient can be determined from the data fitting process with more accuracy than the U value, which, being a minor determinant of the heat flow in the presence of the solar radiation, may require more data for reasonable accuracy. The advantage of this linear model lies in its simplicity, which makes it easy to incorporate into present building energy simulation tools.     

不同气候区建筑获得太阳辐射的动态分布特征

提高太阳能资源在建筑中的利用水平是减缓建筑对传统能源依赖程度的重要途径,也是推广可再生能源建筑应用的基本举措。基于全国五类气候分区代表性城市全年典型气象数据,结合计算模型研究分析了建筑屋面、东面、南面、西面、北面获得太阳辐射量的动态分布特征,确定了建筑各个方位利用太阳能资源的潜力。研究结果表明除了传统地发挥屋面利用太阳能的方法外,建筑立面接收太阳能辐射的能力也能达到良好的效果,即建筑立面利用太阳能具有较好的应用价值。