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.     

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.     

Performance assessment of empirical models for prediction of daily and monthly average global solar radiation: the case study of Ibadan,Nigeria

In this study, the performance assessment of empirical models for modelling global solar radiation in Ibadan is presented. The empirical models are derived from the three basic models: Angstrom–Prescott model, Garcia model and Hargreaves–Sammani model. The data used in the analysis consist of daily average global solar radiation, daily average sunshine hours, daily average maximum temperature and daily average minimum temperature collected over a period of nine years (2000–2008). Regression constants are determined for each of the model for each months of the year. The study reveals that Garcia Quadratic model puts up the best overall performance. The model can predict the daily average global solar irradiation with Mean Absolute Error of 1.86?MJ?m^?2?day^?1, Root Mean Square Error of 2.7?MJ?m^?2?day^?1, Mean Absolute Percentage Error 9.34% and Coefficient of Determination (R²) of 0.68.     

低能耗绿色建筑中针对被动式太阳能技术应用评价方法研究

建筑作为人类文明最重要的产物之一,在全球范围内消耗约40%的一次能源,排放约30%温室气体。在全球能源危机与气候问题的背景下,应采取积极措施减少和取代化石燃料的消耗,同时又不能降低建成环境的舒适度水平。实际上,为实现建筑的"开源""节流"并举的目标,提高建筑能源效率与应用可再生能源的建筑技术已经在建筑领域取得诸多成就。被动式太阳能建筑技术是指通过建筑朝向的合理选择和周围环境的合理布置,内部空间和外部形体的巧妙处理,以及建筑材料和构造的恰当选择,使其在冬季能够收集、储存并使用太阳能,辅助建筑的采暖;同时在夏季通过采取遮阳、自然通风等措施又能屏蔽太阳辐射,帮助室内散热,从而辅助建筑的降温。常见的被动式太阳能建筑技术,例如直接受益太阳能系统、间接受益太阳能系统、独立太阳能系统已经被广泛应用于各类建筑之中。但是,通过综述美国LEED与德国En EV,以及我国《绿色建筑评价标准》与《被动式超低能耗绿色建筑技术导则》等评价体系的相关调研情况发现,在现行的绿色建筑、低能耗建筑评价标准中,太阳能利用的评价方法是以主动式技术应用为基础的,并未全面考虑被动式太阳能建筑技术的贡献率问题。针对此问题,通过分析评价原则与目标、评价指标性质、核心评价指标遴选,提出一种低能耗绿色建筑中针对被动式太阳能贡献率问题的评价方法,以相对太阳能贡献率概念,应对我国太阳能资源分配不均的问题,并提出评价被动式太阳能建筑技术的算法。最后对评价结果的交流、弹性与适应性进行了讨论。并以一栋坐落于中国天津的绿色建筑为例。天津属于太阳能采暖适宜气候区A区,《被动式太阳能建筑技术规范》中的太阳能贡献率参考值为20%。在室内设计温度设置为18℃的情况下,若通过实测计算该建筑的太阳能贡献率为25%,则相对太阳能贡献率在15%~30%区间范围内,因此该建筑可以被认定为第二等级或加分。该评价方法坚持了低能耗绿色建筑"被动设计优先,主动技术优化"的设计原则,完善了现行绿色建筑评价标准中对被动式太阳能技术应用的考虑。寄希望于建筑参与者可以理解、应用这个方法在被动式太阳能建筑中的技术评价,以推动建筑可再生能源技术的发展,并有利于建设资源节约型与环境友好型社会。     

Revision of the Trombe wall calculation method proposed by UNE-EN ISO 13790

The European and International Standard UNE-EN ISO 13790 presents a set of calculation methods for the evaluation and design of energy and thermal performance of buildings. These methods have diverse range of details for calculating the energy use of heating and cooling in different building zones, as well as for calculating the heat transfer and solar heat gains of special elements, such as ventilated solar walls (Trombe walls). In this article, the authors have revised the aforementioned document in order to check the proposed mathematical models and their implementation within Mediterranean climates. This assessment pinpoints the existence of some errors in the equations provided in EN ISO 13790 under steady state conditions. Concurrently, the corrected equations are shown and new correlations are proposed for the ratios δ and ω which are more suitable for Mediterranean climates.     

Solar Energy: true computations and deceiving hopes

An assessment of the point of economic competitiveness of solar technologies in France is given. Payback period criterion and Cost-Benefit Analysis are discussed for the case of the solar hotwater heater and the solar heatina of houses and flats. Macroeconomic obstacles to the penetration of solar energy are considered along with financial efforts in favour of solar energy and the part played by solar energy in the energy balance in the year 2000.     

Optimising the tilt angle for solar surfaces using different solar irradiation models in Yazd,Iran

This paper deals with the determination of the optimum tilt angle for south-facing solar surfaces to collect the maximum solar irradiation in Yazd, Iran. In order to increase the accuracy of results, different models are used in this study. The accuracy of the models is compared in terms of the statistical indicators, RMSE and MBE. The results indicate that the Klucher model gives the best results for estimating the solar radiation reaching the solar surfaces. In comparison to the horizontal surface, on average the gain of energy during the year will be 22.82% if a solar surface is installed at yearly optimum tilt angle. For higher efficiency, it is suggested that the solar surface mounts at the seasonal tilt angle. This leads to an increase in the efficiency of the solar surface of more than 8.86% over that of a similar fixed solar surface at the annual tilt angle.     

光伏发电与建筑一体化技术在住宅小区中的应用

本文通过对小区内一高层住宅公共照明太阳能供电系统的设计及造价估算,增强大家对太阳能在新型节能小区内的应用的认识。     

高层住宅太阳能一体化项目风险评价研究

随着城市化进程的加剧,各大城市出现了一大批高层住宅与太阳能热水系统同步设计同步施工的项目,这些项目由于更加的复杂,其风险较传统工程项目的风险有了很大的不同,给项目管理人员的风险管理带来了挑战。为了应对这一挑战,构建了高层住宅太阳能一体化项目风险评价指标体系,并结合了模糊综合评价和层次分析法的优点建立了基于模糊综合评价的风险评价模型,并最终得出了工程项目风险因素发生的概率以及风险因素对于项目目标的影响程度。最后将风险评价模型应用于西安某太阳能示范小区工程中,得出了该项目的风险程度,验证了此模型是可信的,适用的。     

相变蓄热装置在太阳能热泵系统中的应用

为了研究相变蓄热装置在太阳能热泵系统中的应用,本文建立了具有相变蓄热装置的间接串联式太阳能热泵系统相应的模型,并利用模型对位于长沙的太阳能热泵系统进行了模拟计算.     

Simplified mathematical modelling for a solar humidification compression desalination system

The performance of a solar humidification‐dehumidification desalination where dehumidification is carried out by compression is studied. The mathematical models are developed to assess the effect of operating condition on desalination system. Two models are developed for solar heater and humidifier tower and after solving the models, the obtained results are compared with the experimental data for model verification. The results indicate a good conformity between the model and experimental data. There exist a 1.9–13.3% error between experimental data and modelling. The lowest error is assigned to water temperature in the humidifier and the highest to air temperature in the solar heater.     

天津市太阳能资源分析及其在供暖上的应用

本文利用天津市气象台站近9年来的气象资料,对天津市的太阳能资源进行了分析和评价,并介绍了太阳能在供暖方面的一些新应用,主要包括太阳能地板辐射采暖和太阳能季节热量存储供暖,指出了由于天津地区太阳能资源较为丰富,因此在天津地区开发利用太阳能十分必要。政府应该把开发和利用太阳能放在能源发展的优先地位,应该对阳光经济给予大力支持。     

Development of solar heat gain factors database using meteorological data

In tropical and subtropical regions, solar heat gain via fenestration, particularly on vertical surfaces, plays an important role in determining the thermal performance of a building. For sizing air-conditioning equipment, maximum solar heat gain factors (SHGFs) are used for estimating the design peak load. Recently, the SHGF data representing the prevailing weather conditions have become essential and more practical for part load performance designs and daylighting schemes evaluation. In the absence of measured solar radiation data for the determination of SHGFs, meteorological radiation models may be used. This paper presents the validation of SHGFs prediction models based on sunshine hours and horizontal solar data. Statistical assessments for the models have shown that using sunshine hours to predict the hourly SHGFs may not be appropriate for dynamic building simulation studies. For the average SHGFs computation, all models present acceptable results. In determining the SHGFs for horizontal and vertical surfaces at the peak and other significant levels, all prediction models perform better than the ASHRAE clear sky approach, particularly at high significant levels. This finding also provides information for the estimation of total air-conditioning plant capacity at both the peak load operation and the multiple equipment sizing under part load condition.     

太阳能热泵多功能复合机实验系统建模与仿真分析

本文简要介绍了太阳能热泵多功能复合机(SAHPM)制热系统的工作原理,建立了系统各主要部件的数学模型。考虑到仿真计算的实用性和稳定性,对冷凝器和蒸发器采用分区集总参数法建模,对压缩机和毛细管建立了稳态集中参数模型,给出了太阳能集热器能量平衡方程,通过对仿真结果和实验测试结果的对比分析,验证了模型的正确性。     

太阳能热泵多功能复合机实验系统建模与仿真分析

本文简要介绍了太阳能热泵多功能复合机(SAHPM)制热系统的工作原理,建立了系统各主要部件的数学模型。考虑到仿真计算的实用性和稳定性,对冷凝器和蒸发器采用分区集总参数法建模,对压缩机和毛细管建立了稳态集中参数模型,给出了太阳能集热器能量平衡方程,通过对仿真结果和实验测试结果的对比分析,验证了模型的正确性。     

Forecasting peak-day consumption for year-ahead management of natural gas networks

Security of supply is at the forefront of energy policy in the EU and elsewhere. This paper develops a methodology to forecast peak-day gas consumption for the consideration of gas transmission system operators. It is developed for the domestic and small-to-medium enterprise (SME) gas market, based on a review of current practice. From this assessment, a climate-adjusted network degree day (NDD_CA) variable is developed to estimate the weather-dependent gas consumption of such markets. We show that solar radiation significantly affects gas consumption and should be considered in consumption models. The study also quantifies the difference in capacity required under alternative gas supply standards.     

Coupling simulation system of annual building energy and microclimate

We have developed a simulation system for a year-round assessment of environmental comfort, energy conservation, and CO₂ emissions in buildings and street blocks where active utilization of sunshine, vegetation and solar energy resources is fully considered. An analysis model has been constructed for handling interactions between highly complex street-block wide solar radiation patterns and building air-conditioning load. As a demonstration case of the present system, coupled solar radiation-thermal load analysis for an eleven-story office building has been performed. By comparing the result of a building located in a city block with a reference case of a self-standing building, the proper arrangement of buildings and spaces such as solar reflectance of building surface may be proposed.     

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。     

Uncertainty quantification of microclimate variables in building energy models

The last decade has seen a surge in the need for uncertainty analysis (UA) for building energy assessment. The rigorous determination of uncertainty in model parameters is a vital but often overlooked part of UA. To undertake this, one has to turn one's attention to a thriving area in engineering statistics that focuses on uncertainty quantification (UQ) for short. This paper applies dedicated methods and theories that are emerging in this area of statistics to the field of building energy models, and specifically to the microclimate variables embedded in them. We argue that knowing the uncertainty in these variables is a vital prerequisite for ensuing UA of whole building behaviour. Indeed, significant discrepancies have been observed between the predicted and measured state variables of building microclimates. This paper uses a set of approaches from the growing UQ arsenal, mostly regression-based methods, to develop statistical models that quantify the uncertainties in the following most significant microclimate variables: local temperature, wind speed, wind pressure and solar irradiation. These are the microclimate variables used by building energy models to define boundary conditions that encapsulate the interaction of the building with the surrounding physical environment. Although our analysis is generically applicable to any of the current energy models, we will base our UQ examples on the energy model used in EnergyPlus.     

Passive solar research and practice

Passive solar applications in buildings are described and examples are given to illustrate how research in the field has been approached. The major emphasis of the research has been on devising mathematical models to characterize heat flow within buildings, on the validation of these models by comparison with test results, and on the subsequent use of the models to investigate the influence of both various design parameters and the weather on system performance. Results from both test modules and monitored buildings are given. Simulation analysis, the development of simplified methods, and systems analysis are outlined. Passive solar practice is described and the key elements that have led to successful passive solar applications are discussed.