CERES :: Browsing by Author "Sansom, Christopher L."

Browsing by Author "Sansom, Christopher L."

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Open Access
Adopting machine learning and condition monitoring P-F curves in determining and prioritizing high-value assets for life extension
(Elsevier, 2021-03-13) Ochella, Sunday; Shafiee, Mahmood; Sansom, Christopher L.
Many machine learning algorithms and models have been proposed in the literature for predicting the remaining useful life (RUL) of systems and components that are subject to condition monitoring (CM). However, in cases where data is ubiquitous, identifying the most suitable equipment for life-extension based on CM data and RUL predictions is a rather challenging task. This paper proposes a technique for determining and prioritizing high-value assets for life-extension treatments when they reach the end of their useful life. The technique exploits the use of key concepts in machine learning (such as data mining and k-means clustering) in combination with an important tool from reliability-centered maintenance (RCM) called the potential-failure (P-F) curve. The RCM process identifies essential equipment within a plant which are worth monitoring, and then derives the P-F curves for equipment using CM and operational data. Afterwards, a new index called the potential failure interval factor (PFIF) is calculated for each equipment or unit, serving as a health indicator. Subsequently, the units are grouped in two ways: (i) a regression model in combination with suitably defined PFIF window boundaries, (ii) a k-means clustering algorithm based on equipment with similar data features. The most suitable equipment for life-extension are identified in groups in order to aid in planning, decision-making and deployment of maintenance resources. Finally, the technique is empirically tested on NASA’s Commercial Modular Aero-Propulsion System Simulation datasets and the results are discussed in detail.
Open Access
Advanced data-driven methods for prognostics and life extension of assets using condition monitoring and sensor data.
(Cranfield University, 2021-12) Ochella, Sunday Moses; Sansom, Christopher L.; Shafiee, Mahmood
A considerable number of engineering assets are fast reaching and operating beyond their orignal design lives. This is the case across various industrial sectors, including oil and gas, wind energy, nuclear energy, etc. Another interesting evolution is the on-going advancement in cyber-physical systems (CPS), where assets within an industrial plant are now interconnected. Consequently, conventional ways of progressing engineering assets beyond their original design lives would need to change. This is the fundamental research gap that this PhD sets out to address. Due to the complexity of CPS assets, modelling their failure cannot be simplistically or analytically achieved as was the case with older assets. This research is a completely novel attempt at using advanced analytics techniques to address the core aspects of asset life extension (LE). The obvious challenge in a system with several pieces of disparate equipment under condition monitoring is how to identify those that need attention and prioritise them. To address this gap, a technique which combined machine learning algorithms and practices from reliability-centered maintenance was developed, along with the use of a novel health condition index called the potential failure interval factor (PFIF). The PFIF was shown to be a good indicator of asset health states, thus enabling the categorisation of equipment as “healthy”, “good ” or “soon-to-fail”. LE strategies were then devoted to the vulnerable group labelled “good – monitor” and “soon-to-fail”. Furthermore, a class of artificial intelligence (AI) algorithms known as Bayesian Neural Networks (BNNs) were used in predicting the remaining useful life (RUL) for the vulnerable assets. The novelty in this was the implicit modelling of the aleatoric and epistemic uncertainties in the RUL prediction, thus yielding interpretable predictions that were useful for LE decision-making. An advanced analytics approach to LE decision-making was then proposed, with the novelty of implementing LE as an on-going series of activities, similar to operation and maintenance (O&M). LE strategies would therefore be implemented at the system, sub-system or component level, meshing seamlessly with O&M, albeit with the clear goal of extending the useful life of the overall asset. The research findings buttress the need for a paradigm shift, from conventional ways of implementing LE in the form of a project at the end of design life, to a more systematic approach based on advanced analytics.
Open Access
Airborne sand and dust soiling of solar collecting mirrors
(AIP, 2017-06-27) Sansom, Christopher L.; Almond, Heather; King, Peter; Endaya, Essam; Bouaichaoui, Sofiane
The reflectance of solar collecting mirrors can be significantly reduced by sand and dust soiling, particularly in arid environments. Larger airborne sand and dust particles can also cause damage by erosion, again reducing reflectance. This work describes investigations of the airborne particle size, shape, and composition in three arid locations that are considered suitable for CSP plants, namely in Iran, Libya, and Algeria. Sand and dust has been collected at heights between 0.5 to 2.0m by a variety of techniques, but are shown not to be representative of the particle size found either in ground dust and sand, or on the solar collecting mirror facets themselves. The possible reasons for this are proposed, most notably that larger particles may rebound from the mirror surface. The implications for mirror cleaning and collector facet erosion are discussed
Open Access
Case study: meeting the demand for skilled precision engineers
(Emerald Group Publishing Limited, 2008-01-01T00:00:00Z) Sansom, Christopher L.; Shore, Paul
This paper aims to demonstrate how science and engineering graduates can be recruited and trained to Masters level in precision engineering as an aid to reducing the skills shortage of mechanical engineers in UK industry.
Open Access
A comparison of polymer film and glass collectors for concentrating solar power
(Elsevier, 2014-06-02T00:00:00Z) Sansom, Christopher L.; Comley, Paul; Bhattacharyya, Debabrata; Macerol, Nastja
This paper describes work to compare the optical properties and surface texture of glass and polymer film collectors. We also present the results of experiments designed to simulate collector cleaning processes (both contact and non-contact), and the degradation of glass and polymer reflecting surfaces owing to sand and dust abrasion. Finally we present initial results on the applicability of anti-soiling and self-cleaning coatings on glass and polymer film collector surfaces. Measurements, which include specular and hemispherical reflectance, surface roughness, and electron microscopy, indicate the excellent performance of currently available polymer film in terms of its optical performance and robustness in comparison with traditional glass collectors in CSP applications.
Open Access
A concentrated solar still for community scale desalination.
(2018-08) Bahrami, Mohammadali (Parsa); Sansom, Christopher L.; Tonnellier, Xavier P.
Water and energy are two main basic elements that human lives are dependent on to improve our life standards. Unreliability and a lack of safe drinking water source constitute a major difficulty in developing countries. Among many water purification technologies, solar desalination/distillation has become one of the best solutions as the most attractive and sustainable method to supply drinkable water in remote areas at reasonable cost for future generations. Seawater desalination technologies needed substantial amount of energy in order to convert brackish water into drinkable water. Thus, an extensive research on many desalination technologies has taken place in the last few decades, and solar desalination technology has become one of the most favourable sustainable methods to provide fresh water of sufficiently high quality for human communities. However, this method is not commercialized yet due to its low productivity, but improving this t has become a great source of interest for many researchers. A solar still consumes direct solar energy to produce distilled water through evaporation and condensation process of brackish water. Much research has been conducted in order to increase the productivity, but the outcomes mostly require complex components and a notable increase in cost. Consequently, developing a productive, compact, easy to operate and reasonable cost solar distillation unit was the main challenge in this body of work. A comprehensive literature review is presented in order to illustrate different modifications and their properties on the productivity of solar stills. Even though there are considerations, which cannot be controlled by human intervention (such as meteorological parameters), design and operational factors could make a direct influence on the productivity of the solar still. A novel transportable single basin, double slope shape solar still, enhanced with an internal ventilation fan connected to a copper material heat exchanger, was designed and built without forsaking its basic remit order to increase both evaporation and condensation process. The unit was also designed to use two linear focused Fresnel lenses as a solar radiation concentrator to direct radiation onto the top of solar still basin area. A detailed comparison of theoretical and laboratory experimental results were obtained for the present solar still to find the influence of different modification factors to the present solar still productivity. The temperatures of different parts of the solar still unit such as basin water, top cover glasses, heat exchanger condenser etc. were measured to evaluate different modifications including different fan airflow ratios, with and without a fan shroud, and lava stone effects to the distillate water output. The results presented an increase in productivity of 25.73% in comparison with a conventional solar still, by using a ventilation exhaust fan at its maximum airflow. Also an increase of 16.3% was also achieved by using lava stone as a heat storage material in the basin area.
Open Access
Contact cleaning of polymer film solar reflectors
(AIP Publishing, 2016-01-31) Sansom, Christopher L.; Fernández-García, Aránzazu; Sutter, Florian; Almond, Heather; King, Helen
This paper describes the accelerated ageing of polymer film reflecting surfaces under the conditions to be found during contact cleaning of Concentrating Solar Power (CSP) collectors in the presence of dust and sand particles. In these situations, contact cleaning using brushes and water is required to clean the reflecting surfaces. Whilst suitable for glass reflectors, this paper discusses the effects of existing cleaning processes on the optical and visual properties of polymer film surfaces, and then describes the development of a more benign but effective contact cleaning process for cleaning polymer reflectors. The effects of a range of cleaning brushes are discussed, with and without the presence of water, in the presence of sand and dust particles from selected representative locations. Reflectance measurements and visual inspection shows that a soft cleaning brush with a small amount of water can clean polymer film reflecting surfaces without inflicting surface damage or reducing specular reflectance.
Open Access
The design and modification of a parabolic trough system for the hydrothermal liquefaction of waste
(AIP Publishing, 2019-07-26) Almond, Heather; Tonnellier, Xavier; Sansom, Christopher L.; Pearce, Matt; Sengar, Namrata
We describe the design of a small-scale parabolic trough with a high-pressure absorber bundle to convert microalgae into bio-oil. The “proof-of-concept” system uses an existing Global CSP solar captor, with its reflectance enhanced by the addition of Skyfuel® ReflecTech Plus polymer film and has its original receiver tube replaced by a novel high-pressure multi-tube absorber and reactor. Initial results obtained at Kota University in Rajasthan, India demonstrated that temperatures up to 320°C are possible, and a bio-oil, similar to palm oil, was extracted from the reactor.
Open Access
Design of a novel CSP/MED desalination system
(American Institute of Physics (AIP), 2022-05-12) Sansom, Christopher L.; Patchigolla, Kumar; Jonnalagadda, Kranthi; King, Peter
We describe the design of a large-scale thermal desalination demonstrator unit for use in arid locations with a medium-to-high DNI. Most of thermal energy is provided by a conventional parabolic trough field, in the case of the demonstrator this being 4MWt. The desalination sub-system comprises a 3-effect MED, the first stage of which is a large 20 m diameter glass and steel-structured geodesic and transparent dome. The thermal energy is supplemented by direct sunlight transmitted through the dome and by an arc of small heliostats which focus yet more sunlight onto the dome itself. The prototype is under construction at Neom in KSA.
Open Access
The design of dust barriers to reduce collector mirror soiling in CSP plants
(American Institute of Physics, 2018-11-08) Sansom, Christopher L.; King, Peter; Fernandez-Garcia, Aranzazu; Almond, Heather; Kayani, Talib; Boujjat, Houssamme
In this work we investigate, design, and evaluate a number of dust barrier designs that would be appropriate to reduce soiling of glass mirror solar collectors in the solar field of an existing CSP plant. The principal objective was to reduce the amount of soiling (and hence the amount of cleaning water consumed) by 50% in comparison with current cleaning procedures (considering particles of size >25 µm). “Fluent” CFD software was used to model of a range of potential dust barrier shapes, sizes, and porosities. Airflows and wind loadings were analyzed in this way. A number of potential designs were then taken forward for experimental validation. Initial validation involved wind tunnel evaluation of a small number of potential designs, using a new wind tunnel specifically designed and built for this project. Larger-scale outdoor validation was carried out both at Cranfield University in the UK and at CIEMAT-PSA (Plataforma Solar de Almeria) in Spain. Initial results were independent of location and barrier shape and showed that the percentage of particles that were stopped completely or travelled less than 1m beyond the barrier was in the range 45.8 ± 5%.
Open Access
Effect of sodium rich pretreatments and processing conditions on microstructure and property evolution of sodium cobalt oxide thermoelectric materials
(Cranfield University, 2014-06) Jakubczyk, Ewa; Dorey, Robert A.; Sansom, Christopher L.
Global environmental and sustainability issues have led to a growth in interest in oxide based thermoelectric materials. Sodium cobalt oxide, which presents low toxicity, is one of the most promising p-type thermoelectric materials for high temperature power generation applications. However, reproducibility and ease of manufacture limits its common use. NaCo2O4 bulk ceramic materials were prepared from powders synthesized using a solid state reaction (SSR) and sol gel (SG) method. The effect of time and temperature of treatment were investigated in order to determine their influence on microstructure and physical properties. The effects of three different Na-enriching pretreatments were evaluated with respect to microstructural evolution and their impact on thermoelectric and electric behaviour of the materials. Such modifications were found to be a critical factor affecting the microstructure of the bulk ceramic materials. The Na-rich pretreatments were found to improve density by up to 15%, increase electrical conductivity and help to compensate for Na loss at high sintering temperatures. The thermoelectric figure of merit ZT was found to increase for Na-rich pretreatment samples due to increases in Seebeck coefficient and low thermal conductivity. The highest value of ZT was found to be for the infiltration pretreatment where the value of 0.025 was observed at 350K. Na rich pretreatments, when compared with unpretreatment samples, reduces thermal conductivity by up to 35%, electrical resistivity by up to 67%, increases Seebeck coefficient by up to 23% and as a consequence increases ZT for ball milling preatreatment by 28%, for mixing preatreatment by 71% and for infiltrating by 250%. A range of films were also produced using a spin coating technique, with thicknesses ranging from 200 nm, for single sol gel layers, up to ~ 32μm for 4 (ink + 2 sol layers) structures. Several factors such as: process conditions, substrates, surfactant and base components used, were investigated in order to improve the quality of films. Process conditions were found to be a critical factor affecting the quality of films. The use of sol infiltration of each layer and a higher preheated temperature were found to reduce surface roughness by up to 23%. The films showed good electrical resistivity ranging from 260 to 500 μΩcm. The lowest value of electrical resistivity was found to be for films annealed at 700ºC.
Open Access
Enhancing thermoelectric properties of NaCo2O4 ceramics through Na pre-treatment induced nano-decoration
(Elsevier, 2019-02-19) Jakubczyk, E. M.; Mapp, A.; Chung, C. C.; Sansom, Christopher L.; Jones, J. L.; Dorey, Robert A.
High quality NaCo2O4 thermoelectrics are challenging to process due to the volatile nature of Na, the slow densification kinetics, and degradation of NaCo2O4 above 900–950 °C leading to the formation of Na-poor second phases. Fine grained sol-gel derived powders have been used to enhance the densification kinetics while pre-treatment of the NaCo2O4 powder with NaOH, to provide a Na rich environment, has been shown to mitigate Na loss at elevated temperatures. While insufficient to compensate for Na loss at processing temperatures of 1000 °C and above, at lower temperatures it is able to enhance densification and facilitate the formation of complex crystal structures yielding low thermal conductivity (0.66 Wm−1K−1) coupled with high electrical conductivity (3.8 × 103 Sm−1) and a Seebeck coefficient of 34.9. The resultant room temperature power factor and ZT were 6.19 × 10−6 Wm−1K−2 and 0.0026, respectively.
Open Access
Equipment and methods for measuring reflectance of concentrating solar reflector materials
(Elsevier, 2017-04-06) Fernandez-Garcia, Aranzazu; Sutter, Florian; Martínez-Arcos, Lucía; Sansom, Christopher L.; Wolfertstetter, Fabian; Delord, Christine
The proper optical characterization of solar reflector materials is a challenging task. Although several commercial instruments exist to measure reflectance, they have been developed for other applications and often do not meet all the specific requirements demanded by the solar thermal industry. In particular, the characterization of solar reflectors involve the complete solar spectral wavelength range, an incidence angle range from near normal to 70° and most importantly a very narrow acceptance angle range from near specular to 20 mrad. The accurate measurement of reflectance as a function of all the previously mentioned parameters has not been commercially implemented. This paper reviews the different alternatives to measure reflector materials, describes reflectance models used to approximate the missing information and presents current research work on prototype reflectometers to fill the gap.
Open Access
Extending the functionality and efficiency of energy storage tanks in solar power plants
(2011-09-23T00:00:00Z) Sansom, Christopher L.; Dorey, Robert A.; Jones, Paul M.; Peterson, J.; Jakubczyk, Ewa
Improvements to the efficiency of Solar Power Plants are a key objective as the technology matures. Oneopportunity yet to be explored involves energy harvesting from hot components located within the powerplant, utilizing waste heat. We describe two approaches to energy harvesting in this context. These are basedfirstly on TEC device technology, where we describe the use of both commercially available components andour work to develop more efficient TEC devices based on nanostructured oxides. Secondly, we describe analternative thermomagnetic approach based on nanoparticle ferrofluids for thermal scavenging and theconversion of heat to usable electrical energy. For both approaches we present concept designs for theharvesting of waste heat from thermal energy storage (TES) tanks, in order to demonstrate the potential of thetechnology.
Open Access
Form measurement and durability of mirror surfaces for concentrating solar power applications
(Cranfield University, 2014-11) King, Peter; Sansom, Christopher L.; Comley, Paul
Concentrating solar power systems currently have a high capital cost when compared with other energy generating systems. The solar energy is captured in the form of thermal energy rather than directly electrical, which is attractive as thermal energy is easier and currently cheaper to store in large amounts. It is also used directly as processing heat including desalination and water purification. For the technology to compete against other generating systems it is important to reduce the electrical energy cost to the $0.05 per kilowatt-hour level. One of the significant capital costs is the solar field, which contains the concentrators. To reduce the cost of this field, novel constructions and improvements to the durability and lifetime of the concentrators are required. Techniques for characterising the shape, durability and optical properties of such novel mirrors are the focus of this thesis. The thesis describes the development and validation of an inexpensive, highly portable photogrammetry technique, which has been used to measure the shape of large mirror facets for solar collectors. Photogrammetry has demonstrated its versatility and portability by successful measurements across concentrating solar power sites globally. The accuracy of the technique has been validated to show a measurement capability of better than 100 µm using a large coordinate measuring machine. Measurements performed on novel thin glass mirrors and their comparison with conventional thick glass mirrors are presented, showing that the increased flexibility of thin mirrors is an important consideration during installation, but that it is possible for such novel mirrors to perform to the same level. ...[cont.]
Open Access
Impact of dust on electrical power output of solar PV modules in North-East, Nigeria
(Niger State College of Education, 2022-05-30) Abdulkarim, Hauwa Talatu; Sansom, Christopher L.; Patchigolla, Kumar; Almond, Heather; Karim, Mounia
The impact of dust on the solar PV modules deserves more attention. North-eastern Nigeria has high potential of solar irradiance but it is proned to dust accumulation. This paper therefore, investigated the impact of dust on the performance of solar Photovoltaic modules in North-Eastern Nigeria. The investigation entailed field experiment carried out in Maiduguri to assess the performance of the module based on continuous dust deposition for 14 days during dust accumulation period. The results show that more than 50% loss in power output was recorded under 14 days of continuous deposition. The efficiency of the module reduced from 17.1% on the first day to 7.2% on the fourteenth day of the experimentation. The investigation also shows that at high humidity the PV performance drops. Solar irradiance increases the performance. The deployment of solar PV energy supply system is recommended in spite of dust accumulation challenges. To maintain adequate performance of the system, a once a week cleaning is recommended during intense dust accumulation period.
Open Access
The Integrated Knowledge Centre: A Partnership Between UK Higher Education and Engineering Industry
(Common Ground Publishing, 2012-02-21) Sansom, Christopher L.; Shore, Paul
We discuss the creation of an Integrated Knowledge Centre, a unique collaboration between academia and industry, which is delivering to UK industry 'disruptive' technologies based on ultra precision engineering. The partners include Cranfield University, the University of Cambridge, University College London, and the OpTIC Technium. This paper concentrates on the development of Knowledge Transfer systems and the successful implementation of processes for the delivery of postgraduate taught courses, short courses for industry, and distance learning packages. In order to retain competitive advantage, UK precision engineering industry requires a regular supply of technically proficient and organizationally prepared graduates. This paper explains the approach taken by Cranfield University and its partners to increase the size of the pool of postgraduate precision engineers and to enhance the skills of industrially based engineers. The approach involves the design of a multi-level system, which draws on increased connectivity between the University, UK Engineering companies, and the student. The main vehicle for providing the technical training is the postgraduate Masters degree in "Ultra Precision Technologies". We explain how this course has been designed for broad appeal, whilst incorporating world class technical teaching and an external focus on the needs of participating companies.
Open Access
Light source selection for a solar simulator for thermal applications: A review
(Elsevier, 2018-04-24) Tawfik, Mohamed M.; Tonnellier, Xavier; Sansom, Christopher L.
Solar simulators are used to test components and systems under controlled and repeatable conditions, often in locations with unsuitable insolation for outdoor testing. The growth in renewable energy generation has led to an increased need to develop, manufacture and test components and subsystems for solar thermal, photovoltaic (PV), and concentrating optics for both thermal and electrical solar applications. At the heart of any solar simulator is the light source itself. This paper reviews the light sources available for both low and high-flux solar simulators used for thermal applications. Criteria considered include a comparison of the lamp wavelength spectrum with the solar spectrum, lamp intensity, cost, stability, durability, and any hazards associated with use. Four main lamp types are discussed in detail, namely argon arc, the metal halide, tungsten halogen lamp, and xenon arc lamps. In addition to describing the characteristics of each lamp type, the popularity of usage of each type over time is also indicated. This is followed by guidelines for selecting a suitable lamp, depending on the requirements of the user and the criteria applied for selection. The appropriate international standards are also addressed and discussed. The review shows that metal halide and xenon arc lamps predominate, since both provide a good spectral match to the solar output. The xenon lamp provides a more intense and stable output, but has the disadvantages of being a high-pressure component, requiring infrared filtering, and the need of a more complex and expensive power supply. As a result, many new solar simulators prefer metal halide lamps.
Open Access
Modelling and techno-economic analysis of a solar PV system for power supply: case study of a rural area in North-Eastern NIgeria.
(Cranfield University, 2019-10) Abdulkarim, Hauwa Talatu; Sansom, Christopher L.; Patchigolla, Kumar
Energy which is vital in the economic and social growth of any country is facing increased demand because of technological and industrial developments in the world. Most of the energy supplied globally is being generated from fossil fuels. However, studies have shown that these resources have many negative environmental and health impacts. This gives reason for development of renewable energy sources especially solar photovoltaic system. The investment for large solar PV power plants is capital intensive, therefore, a solar photovoltaic system model (SPVSM) which can be rapidly used for accurate sizing of the system components for optimized solar PV system for power supply becomes imperative. Soiling, which has not received adequate global attention, is a major problem in the operation of solar PV systems. It affects the performance of PV systems; therefore, the study of its impact is crucial especially for location with potential for dust accumulation. The main aim of this research is to develop a novel, simple and robust decision- making model, Solar-Photovoltaic-System-Model (SPVSM) for an optimised power supply at a competitive cost and to determine the impacts of dust accumulation on the performance of solar PV modules. The collection and analysis of solar and climatic data is of utmost importance to the development of solar energy conversion system in any location because the knowledge of the availability of solar resource is key to the decision on installation of solar PV systems. For this research, three locations (Maiduguri, Minna and Port Harcourt) were carefully chosen to represent the three radiation regions in Nigeria. This becomes very important because of the scanty availability of solar and climatic data analysis for these regions. Solar irradiance, relative humidity, temperature and sunshine hours data were collected for these locations for a period (2006 to 2016) from the Nigerian Meteorological Agency, Abuja. The data were statistically analysed using Minitab 17 software and Microsoft Excel. The SPVSM which was developed on a single graphical user interface platform in MATLAB17 is made up of six panels, each handling the sizing of different system components (PV modules, inverters, charge controllers and batteries) as well as energy and economic analysis of the system. A PV model which generates the I-V and P-V characteristics of the 50W module was developed using Simulink in MATLAB2017. A single diode model was used to produce the ideal equivalent circuit of solar cell, which is a current source in parallel with a single diode. Two sub-systems were developed to handle saturation current and photocurrent. A maximum power point tracking (MPPT) system was developed using thePerturb and Observe algorithm in Simulink. The specification of a 50 W PV module model TDG-PV T050M365 was used for the simulation. The MPPT simulation gave a 50.09 W for solar irradiance of 1000 W/m² and 37.9 W/m² for irradiance of 800 W/m². A field experiment was carried out in a location in North-eastern Nigeria to assess the impact of dust accumulation on the performance of PV modules. The experiment was conducted for 14 days using a 50W module of model TDG-PV T050M365. The current and voltage output of the module were concurrently measured and logged using Mooshimeter. The temperature, solar irradiance, wind speed and relative humidity were measured and recorded every hour. Dust were collected at different heights (50 cm, 100 cm, 150 cm and 200 cm).The dust so collected were analysed in Cranfield. For dust accumulation to have effect on performance of PV module, there must be adhesion. This led to the laboratory experimentation on the effect of temperature, particle size, humidity, type of sand, and height on the adhesion of sand to glass cover of PV module. The data analysis shows that the three locations have adequate daily solar irradiance and therefore, have potential for viable development of solar PV systems for power supply with Maiduguri being more viable than Minna and Port Harcourt. The economic analysis from the SPVSM shows that the Levelized cost of electricity is $0.081/kWh and the net present value (NPV) is positive for Maiduguri, therefore it can be concluded that development of solar PV system in Maiduguri is economically viable. The use of lower peak watt module rating has economic implications on the project total cost and consequently on the overall economics of the system. Dust accumulation can reduce the performance of solar PV module by more than 50% and the analysis of sand/dust samples from Maiduguri shows varying sizes and shapes of roundness that roll off the panel with less effect on the panel surface erosion; and sharpness that deteriorates the PV module. Also, the chemical analysis further shows that dust from Maiduguri is high in silica (SiO2) i.e. prevalence of quartz which confirm the zone being desert. The results of the laboratory experiments show that, some of the factors studied have effect on the amount of sand that sticks to glass. Humidity is the factor with the highest influence. At higher humidity more sand adhere to the glass, this is due to the higher moisture content of the air which aids in dissolving any soluble materials and bind the particles to the surface. Also, desert natural sands adhere more strongly to the glass than artificial quartz-based sands, this is possibly due to the fact that natural sand contains higher amounts of soluble materials.
Open Access
Numerical and experimental study of a lens-lens beam generator solar concentrator.
(2018-06) Tawfik, Mohamed Mostafa Hassan; Sansom, Christopher L.; King, Peter
The increased risk of climate change, besides the rapid depletion of non-renewable sources, motivated researchers to replace non-renewable energy sources with renewable ones. Solar energy can be considered as the “mother” of all renewable energy sources. The research trend in concentrated solar power systems tends to study optimising the utilisation of such power source. However, most researches deal with building new facilities that uses solar thermal power efficiently. Although it is important to improve innovative designs for our energy future, parallel thinking in currently existing facilities is necessary. The aim of this work is to lower the Carbon footprint of currently existing conventional power systems that uses fossil fuels through hybridisation with solar energy efficiently. This would encourage countries, especially developing ones, to move forward to solar technologies. Therefore, an overview of different concentrated solar power (CSP) technologies is carried out. Among different CSP technologies, a two-stage lens system was used to generate a powerful and controllable concentrated solar beam, namely Lens-Lens Beam Generator (LLBG), is found to allow achieving the aim with minimum modifications requirements. The LLBG provides a unique flexibility in selecting the receiver location. This facilitates implementing solar energy in fossil-fuel systems which are currently in service and affording reduced land usage. However, it was built on a small scale with a restricted concentration ratio (CR) of 6.25 to avoid overheating its rear lens, using two bi-convex lenses. As a relatively high efficiency of 82.65% was reported at this low CR, it has the potential to achieve high CR values and higher thermal efficiency using a dual-axis tracking system. Building large aperture refractive-based solar concentrating systems tends to employ Fresnel lens geometry due to their cost and design advantages. Then, an evaluation of implementing Fresnel lenses in building such LLBG system became as the gap of knowledge for the current research. covering this gap required investigating the front and rear lenses geometries and materials. However, because of the UK location within a relatively low-DNI region with an average annual direct normal irradiation (DNI) of 400-1000 kWh/m², building a solar simulator for thermal testing arose as a critical need to achieve the required objectives within the limited research time-scale. Therefore, it became as one of the main research objectives of the present work. To fulfil this, different light sources have been reviewed and two of them are selected to be further studied. These selected light sources were metal halide and tungsten halogen. Metal halide lamps showed better match with solar spectrum over full spectral bandwidth compared to tungsten halogen light source. Despite that, utilising dimmable tungsten halogen lamp is more recommended for thermal testing, use as it provides controllable good output spectrum over the IR spectral zone. For the front lens design, manufacturing and cost studies carried out within the present work indicated that using plastic Fresnel lenses is the most cost-effective option for large-scale aperture refractive systems. Based on optical study performed, PMMA has been selected as the best material due to its higher ideal optical efficiency, compared to polycarbonate. For the rear lens geometry, thermal study indicated that positive meniscus geometry can withstand higher CRs, compared to both plano- and bi-convex geometries. Combination of thermal and optical studies showed that SiO₂ represents the optimum material for the rear lens, allowing highest CRs with maximum transmittance. Two Fresnel-based LLBG systems are designed and built to experimentally asses their performance. These systems were: prototype- and full-size systems, with results showing average field efficiencies of 17.30% and 17.65%, respectively, within 0.5m from the control mirror. By suppressing the influence of optical efficiencies due to different components used, a thermal conversion efficiency of 29.5% was obtained for both systems. These values showed that building a unit aperture area of an LLBG system can save up to 25.76 kg/year and 29.37m³/year of petroleum and natural gas, respectively. This can lead to annual CO₂ footprint reduction by 26.95 and 23.84 kgCO₂ for power generation systems that use combined cycles fuelled by petroleum and natural gas, respectively. Further optical investigation of Fresnel-based LLBG system to study the effects of different parameters on its performance. Although this investigation showed that IR spectrum deviates less than VIS and UV spectra, it also indicated that using Fresnel geometry for the front lens causes increases in the generated beam deviation angle. This reduces the system efficiency dramatically and its ability to carry the beam efficiently over long distances.