Mehreen Gul

Evaluation of sunshine and cloud cover based models for generating solar radiation data

Abstract Solar radiation models based on meteorological parameters serve as the substitute to measured irradiation and illuminance data. Models originating from sunshine or cloud cover information constitute the two main classes of meteorological radiation models. Further improvements in the accuracy of these models is under research. One such approach, attempted by Page, has resulted in the formation of a model that utilises a combination of the above mentioned variables. This article briefly discusses the new combined approach and evaluates it against other models developed by the authors: the Meteorological Radiation Model (MRM) based on sunshine fraction and the Cloud Cover Radiation Model (CRM) based on cloud cover. Results show that Page’s approach is quite successful under overcast conditions. The MRM, however appears to provide better estimates under part clear and clear sky conditions.

Models for obtaining solar radiation from other meteorological data

The application of solar energy requires a knowledge of long-term solar radiation and daylight data. Because of the limited availability of measured data, various formulae have been derived to compute the solar irradiance using other, more commonly available, weather data. In this article two such models are presented, MRM (meteorological radiation model) and CRM (cloud-cover radiation model). MRM requires hourly data for sunshine duration, dry- and wet-bulb temperature; while CRM requires only cloud amount. Both models can generate hour-by-hour data for horizontal global, diffuse, and beam irradiance. A brief comparison of the two models is presented. Results showed that MRM has the advantage over CRM, on account of its consistency with the measured data. Both models are now available via the Internet in the form of electronic spreadsheets.

Evaluation of an all-sky meteorological radiation model against long-term measured hourly data

Abstract With the proliferation of cheap, high performance desktop computers, the building services profession is demanding detailed (hourly or sub-hourly) weather data for simulation, optimum plant sizing and design of buildings which may use passive solar and/or natural ventilation features. Even in a developed country, such as the United Kingdom, there is a dearth of measured long-term solar radiation and daylight data. Herein, a simple and precise meteorological radiation model (MRM) is presented, which enables computation of horizontal beam and diffuse solar radiation to be accomplished, given four basic meteorological parameters—hourly dry- and wet-bulb temperatures, atmospheric pressure and bright sunshine duration. These data are available worldwide for very many locations. The present model is of a semi-general nature as demonstrated by its applicability to ten widespread locations in the United Kingdom. The model enables computation of hour-by-hour insolation. Statistical analysis of 100 station-years hourly data indicates that the MRM can compute insolation with an average error of 9% for clear skies and 25% for overcast conditions. On a monthly-averaged hourly and daily basis, this error reduces to 3%.

Models for Estimating Solar Radiation and Illuminance From Meteorological Parameters

Sunshine fraction, cloud amount, temperature, and global irradiation are the most commonly measured meteorological parameters. In this article five models based mainly on the abovementioned variables for the determination of irradiation and illuminance components are presented. These models are divided into three categories. Category 1 includes three solar radiation models: (a) Meteorological Radiation Model (MRM), developed by present authors based on sunshine fraction and temperature data, (b) Cloud-Cover Radiation Model (CRM)-modification of an earlier model for the UK by the present authors based on cloud-cover in oktas, and (c) Page Radiation Model (PRM), developed by Page based on simultaneous sunshine and cloud data. Category 2 comprises of a new Diffuse Ratio Model (DRM), developed by authors, for estimating diffuse irradiation when global irradiation is provided as the input parameter. The third category includes luminous efficacy models that enable estimation of diffuse and global illuminance once the respective irradiation components have been obtained from category I models.

Tailoring a future overheating risk tool for existing building design practice in domestic and non-domestic sectors

The Low Carbon Futures Project, as part of the Adaptation and Resilience to Climate Change (ARCC) programme, has developed an overheating tool, based on probabilistic UK Climate Projections (UKCP09), to provide design advice for building adaptations in future. For dwellings this tool, initiated by a single simulation, relies on just hourly climate information to predict the internal temperature profile and for a non-domestic building, it includes internal activity profiles to account for lighting, equipment, metabolic gains and air change. To produce a tailored design tool, a qualitative investigation has been carried out to understand current building practices. This investigation shows that the two sectors take a significantly different approach to design, where dynamic building simulation is rare for domestic developments. The diversity of the non-domestic building stock poses different challenges and requires more detail to perform any overheating analysis, with dynamic building simulation playing a key role. The suitability of this tool, and the need to balance complexity and detail with usability and applicability, will be explored for the two sectors, with an approach for implementing this in the future proposed. Practical application: This paper compares current overheating analyses, as reported through correspondence with practitioners, with a suggested approach for a more detailed future overheating assessment using the latest climate projections. The required steps to bridge the gap between current and possible future design methods are explored for both the domestic and non-domestic sectors, with a prototype tool proposed that has been formulated with the aid of industry feedback. The described project is therefore able to translate complex building and climate science into an approach that is potentially useful for building practitioners.

Review on recent trend of solar photovoltaic technology

Solar photovoltaic technology is one of the renewable technologies, which has a potential to shape a clean, reliable, scalable and affordable electricity system for the future. This article provides a comprehensive review of solar photovoltaic technology in terms of photovoltaic materials efficiency and globally leading countries. Based on past years review and photovoltaic installations in the year 2014, the major five leading countries identified are China, Japan, USA, Germany and UK. These five countries altogether accounted for 80% of photovoltaic installations in 2014. The article also discusses the driving policies, funding and Research and Development activities: to gauge the reasons behind the success of the leading countries. Finally, this article reviews the photovoltaic cost analysis in terms of the photovoltaic module cost, balance of system cost and project cost with the help of listed 98 globally installed projects.

Communicating future overheating risks to building design practitioners: Using the Low Carbon Futures tool

The Low Carbon Futures tool provides a probabilistic assessment of future overheating risks and cooling demands for domestic and nondomestic buildings in the UK. The approach adopted for the development of the Low Carbon Futures tool includes academic rigour within the development of the calculation engine, and also practitioner feedback throughout the process. This paper discusses the journey of the tool from modelling and simulation to the practitioner engagement, which took place by means of a questionnaire, focus groups and interviews with building design professionals aimed at understanding how the issue of overheating in buildings is being addressed. Throughout these events, the synergies between designing for low-carbon targets and designing for a future climate were explored. A final dissemination event was held to identify output styles that could be generated by the Low Carbon Futures tool that would be more practical and useful for specific client types. The workshop discussions serve to shape the outputs from the tool, and the feedback gathered will be used to inform a number of output styles, based on client type. Practical application : This paper outlines the development of the Low Carbon Futures tool for analysing overheating risks in buildings and discusses the practitioner feedback obtained from industry professionals on the use and applicability of the tool, in a final event hosted by the Low Carbon Futures research team in London. This event confirmed that practitioners need to be comfortable with the layout and format of the output in order to communicate its meaning and possible implications to a range of clients. A balanced output is required, which conveys some of the complexity of the underlying analysis, but which is easily understood and conveyed to a potentially lay audience.

Solar diffuse irradiance: Estimation using air mass and precipitable water data:

The influence of meteorological variables on the hourly fraction of diffuse solar irradiance was studied. The goal was to determine whether including variables other than the clearness index (ratio of hourly global to hourly extraterrestrial irradiance) will further improve the results of existing correlations. Two new models were developed in this regard. In the PAC model (for precipitation, air mass and clearness index) the diffuse fraction was predicted as a function of three independent variables: the precipitable water, air mass and clearness index. No further improvement was observed. An entirely new approach is proposed on the basis of a relationship between diffuse irradiance and the product of air mass and precipitable water. The new correlation shows significant improvement under all sky conditions and reduces the mean bias error by an average of 37% under overcast conditions, 28% under intermediate conditions and about 33% for clear sky conditions. The proposed correlation has been fitted against data for several locations in the United Kingdom and outperforms the other models on all statistical criteria.

Finite-element view-factor computations for radiant energy exchanges

Radiation heat transfer has very many applications within the building services sector. CIBSE (Chartered Institution of Building Services Engineers) Guide A provides the physics background and the relevant mathematical functions for radiant energy exchanges between surfaces of different configurations in chapters 2 and 5. The aim of this article is to present procedures for inter-surface radiant energy exchange that range from the most simple (macro-) to most general formulations that are based on a micromesh, finite-element approach. The justification for such detailed procedures and their applicability within the modern building energy simulation software is also covered.

Towards an overheating risk tool for building design

Purpose – The work set out to design and develop an overheating risk tool using the UKCP09 climate projections that is compatible with building performance simulation software. The aim of the tool is to exploit the Weather Generator and give a reasonably accurate assessment of a buildings performance in future climates, without adding significant time, cost or complexity to the design teams work.Methodology/approach – Because simulating every possible future climate is impracticable, the approach adopted was to use principal component analysis to give a statistically rigorous simplification of the climate projections. The perceptions and requirements of potential users were assessed through surveys, interviews and focus groups.Findings – It is possible to convert a single dynamic simulation output into many hundreds of simulation results at hourly resolution for equally probable climates, giving a population of outcomes for the performance of a specific building in a future climate, thus helping the use...