A combined optical, thermal and electrical performance model of a Building Integrated Photovoltaic/Thermal Concentrator (BIPVTC)

The electrical output of concentrating photovoltaic devices is significantly affected by the temperature of the photovoltaic cells. The ability to actively cool photovoltaic cells under concentrated radiation allows their electrical efficiency to be maintained particularly during periods of high solar radiation when concentration offers the maximum benefit. In this study, the design of a novel photovoltaic/thermal solar concentrator for building integration (BIPVTC) is discussed. The optical, thermal and electrical performance of the collector was theoretically modelled and validated with experimental data. The results show that BIPVTC offers improved electrical yields from both concentrating radiation onto the photovoltaic cells and also by actively cooling them

Experimental and Numerical Investigation of Thermal Performance of a Crossed Compound Parabolic Concentrator with PV Cell

Crossed compound parabolic concentrator (CCPC) is a solar energy device used to increase the photovoltaic (PV) cell electrical power output. CCPC’s thermal and optical performance issues are equally important for a PV cell or module to work under a favourable operating condition. However, most work to-date is emphasised on its optical performance paying a little attention to the thermal characteristics. In this contribution, we investigate the thermal performance of a CCPC with PV cell at four different beam incidences (0o, 10o, 20o, 30o and 40o). Initially, experiment is performed in the indoor PV laboratory at the University of Exeter with 1kW/m2 radiation intensity. 3D simulations are carried out to first validate the predicted data and then to characterise the overall performance. Results show that the temperature in the PV silicon layer is the highest at 0o and 30o, with the top glass cover of CCPC having the lowest temperature at all the incidences. The temperature and optical efficiency profiles at the various incidences predicted by simulation show very good agreement with the measurements, especially at 0o incidence. This study provides useful information for understanding the coupled optical-thermal performance of the CCPC with PV cell working at various conditions

Smart windows: Thermal modelling and evaluation

Copyright @ 2014 The Authors. Published by Elsevier Ltd. This is an open access article shared under the CC BY license (http://creativecommons.org/licenses/by/3.0/).A numerical investigation of the performance of a multi paned smart window integrated with water-cooled high efficiency third generation GaAsP/InGaAs QWSC (∼32% efficiency) solar cells illuminated by two-axis tracking solar concentrators at 500× in the inter pane space is presented. Optimising system parameters such as optical concentration ratio and coolant (water) flow rate is essential in order to avoid degradation in system performance due to high cell temperatures and thermal stresses. Detailed modelling of the thermo-fluid characteristics of the smart windows system was undertaken using a finite volume CFD package. Results of this analysis which considered the conductive, convective and radiative heat exchange processes taking place in the interior of the smart window system as well as the heat exchange to the internal and external ambient environment are presented.Engineering and Physical Sciences Research Counci

Distributed Simulation of Real Tunnel Junction Effects in Multi-Junction Solar Cells

In this paper, we present an improved 3D distributed model that considers real operation regimes in a tunnel junction. This advanced method is able to accurately simulate the high concentrations at which the current in the solar cell surpasses the peak current of the tunnel junction. Simulations of dual-junction solar cells were carried out with different light profiles and including chromatic aberration to show the capabilities of the model. Such simulations show that, under some circumstances, the solar cell short circuit current may be slightly higher than the tunnel junction peak current without showing the characteristic dip in the J-V curve. This behavior is caused by the lateral current spreading towards the dark regions, which occurs through the anode region of the tunnel junction

Energy and economic analysis of a residential Solar Organic Rankine plant

To answer the actual energy, water, economic, social and environmental challenges, renewable, distributed power plants need to be developed. Among renewables, solar tri-generative power plants can be a solution where there is big low temperature heating/cooling demand and small electricity demand, like many residential and industrial utilities. In this case, solar thermal plants can produce thermal energy with low cost and high efficiency. The higher temperature heat not needed by the user can be exploited via Organic Rankine Cycle to produce electrical energy and desalinized water via reverse osmosis. The present paper analyses, via TRNSYS simulation, a system composed of 50 m2 of CPC solar thermal collectors, 3 m3 of thermal storage, a synthetic heat transfer fluid, 3 kWe ORC, 8 kWth absorber, 200 l/h direct reverse osmosis desalination device. The system is able to produce power, heating/cooling and fresh water needs for a residential house. Although system’s components are well known technologies, the integration to a efficient and economic working system is still a challenge. Global energy and economic analyses have been performed. Low temperature heating/cooling terminals allow to increase not only the use of thermal energy but also the ORCand absorber efficiency. ORC-Absorber configuration and relative fluids and temperatures are central. Government support and/or cost reduction of 30% are necessary to have positive NPV and acceptable PBT and IR

Multiscale approaches to high efficiency photovoltaics

While renewable energies are achieving parity around the globe, efforts to reach higher solar cell efficiencies becomes ever more difficult as they approach the limiting efficiency. The so-called third generation concepts attempt to break this limit through a combination of novel physical processes and new materials and concepts in organic and inorganic systems. Some examples of semi-empirical modelling in the field are reviewed, in particular for multispectral solar cells on silicon (french ANR project MULTISOLSI). Their achievements are outlined, and the limits of these approaches shown. This introduces the main topic of this contribution, which is the use of multiscale experimental and theoretical techniques to go beyond the semi-empirical understanding of these systems. This approach has already led to great advances at modelling which have led to modelling software which is widely known. Yet a survey of the topic reveals a fragmentation of efforts across disciplines, firstly, such as organic and inorganic fields, but also between the high efficiency concepts such as hot carrier cells and intermediate band concepts. We show how this obstacle to the resolution of practical research obstacles may be lifted by inter-disciplinary cooperation across length scales, and across experimental and theoretical fields, and finally across materials systems. We present a European COST Action MultiscaleSolar kicking off in early 2015 which brings together experimental and theoretical partners in order to develop multiscale research in organic and inorganic materials. The goal of this defragmentation and interdisciplinary collaboration is to develop understanding across length scales which will enable the full potential of third generation concepts to be evaluated in practise, for societal and industrial applications.Comment: Draft paper accompanying a plenary presentation to the World Renewable Energy Conference WREC 2015, June 2015, Bucharest. In press (IOP

Novel system for distributed energy generation from a small scale concentrated solar power

The present work describes the realization of a modular 1-3 kWe, 3-9 kWth micro Combined Heat and Power (m-CHP) system based on innovative Concentrated Solar Power (CSP) and Stirling engine technology. The cogeneration of energy at distributed level is one of leading argument in large part of energy policies related to renewable energy resources and systems. This CSP m-CHP will provide electrical power, heating and cooling for single and multiple domestic dwellings and other small buildings. The developed system integrates small-scale concentrator optics with moving and tracking components, solar absorbers in the form of evacuated tube collectors, a heat transfer fluid, a Stirling engine with generator, and heating and/or cooling systems; it incorporates them into buildings in an architecturally acceptable manner, with low visual impact. Some good results have already been achieved, while developments on several technology subcomponents will be finalized through first part of 2013. Two Cer.Met. have been modelled, realized and tested. The up scaled receiver, in form of Cer.Met. coating based on TiO2 - Nb, has been confirmed an absorptance of 0.94 and emittance of 0.1 (@350°C). A second Cer.Met. coating based on SiO2 - W has demonstrated an absorptance of 0.93 and emittance of 0.09 (@350°C). A full-evacuated solar tube has been designed and realized, with absorber of 12 mm in diameter and length in 2 meters. The system is provided of a concentration ratio 12:1, and a single module is 200 cm long, 40 cm wide and 20-25 cm high. Two or more modules can be combined. The evacuated solar tube, located on the focus, has the selective absorber on a tube of 12 mm in diameter. A very thin glass mirror has been developed (< 1 mm). The overall mirror reflectivity has been measured, the verified value is 0,954. Research has proposed a high energy density, double acting Stirling engine, provided of innovative heat exchangers realized through Selective Laser Melting process. The engine is a low speed (250 RPM), high pressure (130 Bars) and compact solution able to be run at 300°C and generate 3,5 kW nominal power. The solar technology has actually entered the proof-of-concept stage. A solar plant has been installed in Malta, by Arrow Pharm company, supplying the industrial process of generated steam at 180°C and 3.5 absolute pressure. The solar collector's efficiency is close to 47% in presence of 900 W/m2 of direct solar radiation. During 2013, solar evacuated tubes with innovative Cer.Met. coating, together with new thin glass mirrors will upgrade the demonstration site, together with a new and innovative low temperature difference and high energy density Stirling. By end-2013, the system will be demonstrated, with the overall objective to achieve a minimum of 65% in solar collectors' efficiency at 300°C, and 12 - 15% of overall electrical efficiency by the Stirling cycle.peer-reviewe

Design and characterisation of a novel translucent solar concentrator

This thesis begins with an investigation into the optical performances of the Crossed Compound Parabolic Concentrator (CCPC) for photovoltaic application and introduces the novel concept of a Translucent Integrated Concentrated Photovoltaic (TICPV). The use of solar concentrators in BIPV enables a reduction in the cost of generating photovoltaic electricity lending to yet another field of research known as Building Integrated Concentrated Photovoltaics (BICPV). The potential of BICPV as the most promising technologies for future electricity supply is examined by the design, optimisation and testing of the main component of the TICPV, a novel static nonimaging transparent 3-D concentrator coined the Square Elliptical Hyperboloid (SEH), for the use in building fenestrations. The SEH concentrator was designed and optimised via ray-tracing technique. A preliminary investigation into the optical efficiencies of 160 SEH concentrators of varying geometries was conducted and from this 20 concentrators were chosen and studied in more detail using the developed optical model with the aim of obtaining an optimised SEH concentrator out of these 20. The optimisation process proved to be far from straightforward, however, after careful consideration, five SEH concentrators with the best optical performances, each with different heights, were chosen. These concentrators were fabricated and used to assemble five separate TICPV modules. Subsequent to carrying out the simulation, the five optimised TICPV modules were examined in different environments (indoor and outdoor). The results of the indoor test, where the TICPV modules are exposed to direct radiation from a solar simulator, provided clear validation of the optical model; the results of the outdoor test added further to the validation and confirmed the power output of the TICPV modules when exposed to both direct and diffuse radiations. The TICPV modules are developed in a way such that they collect sunlight during most of the hours throughout the day, allowing the generation of electrical power whilst maintaining the level of transparency of the fenestration. It was found that the TICPV modules are capable of saving more than 60% of the solar cells used in conventional flat PV systems. The designed TICPV modules simultaneously provide solar energy generation and optimised day lighting. The TICPV module designed in this thesis provides a viable solution to coping with the increasing energy demands and will create a new age of energy efficient buildings reducing the carbon footprint of both existing buildings and buildings of the future