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Research and development of transparent insulation systems (TI-systems) has been ongoing for 20 years with transparent insulation materials (TIMs) used to replace standard opaque insulation materials. TIM not only performs similar functions to opaque insulation, reducing heat losses and controlling indoor temperatures, but allows solar transmittance of more than 50%. With a thickness of less than 20 cm, it can provide a financial return to building occupants when applied to building facades, maximising occupiable and sellable spaces in urban areas, without compromising thermal comfort within buildings. In this review of TI-systems for building applications, drawbacks to previous applications, cost trends, and analysis of the limitation in information from previous studies are discussed. A major drawback in the development of TI-systems identified is the lack of cost information; the payback periods for TI-systems used in previous renovation projects are virtually unknown. Simple payback period calculations were undertaken based on information available from a demonstration project documented by the Solar Heating and Cooling (SHC) Programme of the International Energy Agency (IEA) Task 20 'Solar Energy in Building Renovation'. The calculations indicated an encouraging 5-8-year payback period for this particular case study. It was concluded that the simple payback period calculation may be used for feasibility studies to indicate the time required to recoup investment when installing TI- systems and to provide initial guidance for building designers when evaluating the potential application of TI-systems in their buildings. Keywords: Transparent insulation material (TIM); Transparent insulation system (TI-system); Building applications

A novel, non-tracking concentrator is described, which uses nano-scale quantum dot technology to render the concept of a fluorescent dye solar concentrator (FSC) a practical proposition. The quantum dot solar concentrator (QDSC) comprises quantum dots (QDs) seeded in materials such as plastics and glasses that are suitable for incorporation into building facades. Photovoltaic (PV) cells attached to the edges convert direct and diffuse solar energy collected into electricity for use in the building. Small scale QDSC devices were fabricated. Devices have been characterised to determine current, voltage and power readings. Electrical conversion efficiencies, fill factors and comparative concentrating factors are reported. Keywords: Quantum dot; Solar concentration; Fluorescence; Photovoltaic cell; Non-imaging concentrator

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.solener.2005.10.006 Byline: M.J. Huang (a), P.C. Eames (a), B. Norton (b) Keywords: Phase change material; Photovoltaic cell; Thermal control; Building integration Abstract: Elevated operating temperatures reduce the solar to electrical conversion efficiency of photovoltaic devices. This paper presents an experimental evaluation of phase change materials for thermal management of photovoltaic devices. Two particular phase change materials were used to moderate the temperature rise of photovoltaics. The thermal performance of different internal fin arrangements for improving bulk PCM thermal conductivity are presented. Using RT25 with internal fins, the temperature rise of the PV/PCM system can be reduced by more than 30[degrees]C when compared with the datum of a single flat aluminium plate during phase change. Phase change materials are shown to be an effective means of limiting temperature rise in photovoltaic devices. Author Affiliation: (a) Centre for Sustainable Technologies, School of the Built Environment, University of Ulster, Newtownabbey BT37 0QB, Northern Ireland, UK (b) FOCAS Institute, Dublin Institute of Technology, Aungier Street, Dublin 2, Ireland Article History: Received 13 January 2005; Revised 16 September 2005; Accepted 3 October 2005 Article Note: (miscellaneous) Communicated by: Associate Editor Peter Lund

An experimental investigation of an inverted absorber integrated collector storage solar water heater mounted in the tertiary cavity of a compound parabolic concentrator with a secondary cylindrical reflector has been performed under simulated solar conditions. The solar water heaters performance was determined with the aperture parallel to the simulator for a range of transparent baffles positioned at different locations within the collector cavity. Results indicate that glass baffles located at the upper portion of the exit aperture of the CPC can reduce thermal losses through convection suppression without significantly increasing optical losses. Keywords: ICSSWH; Baffle convection suppression; CPC; Inverted

A novel non-imaging asymmetric compound parabolic photovoltaic concentrator (ACPPVC) has been designed, constructed and experimentally characterised at the University of Ulster, Northern Ireland (54[degrees]36'N, 5[degrees]37'W). Different numbers of PV strings connected in series were experimentally characterised under outdoor conditions both with and without concentrators. Transient I-V curves for each set of parameter data points were determined and the maximum power generation, fill factor and efficiency of the system calculated for each individual I-V curve. Experiments showed that the use of an ACPPVC increased the maximum power point by 62% (i.e. the power by a factor of 1.62) when compared to a similar non-concentrating PV panel. Keywords: Photovoltaics; Asymmetric compound parabolic concentrator; Building integration

An integrated collector/storage solar water heater (ICSSWH) that can significantly reduce heat loss to ambient during non-collection periods has been developed. Two thirds of the ICS vessel is mounted within a concentrating cusp, McIntire 'W' modified concentrator and incorporates an inner heat retaining vessel. The remaining upper 1/3 of the vessel is situated outside the reflector cavity and is heavily insulated. Over 60% of the thermal energy stored within the total vessel, and up to 67% of that in the upper immediate draw-off region can be retained over a 16-h non-collection period. Results of an experimental analysis of this design and a comparison with a standard ICS design are presented.

An indium-based seal augmented with an adhesive, developed to maintain a vacuum between two sheets of glass, avoids the high temperatures required to produce a seal in evacuated glazings to date. An experimentally-validated three-dimensional transient model has been used to predict heat transfer for an indium/adhesive sealed 1 [m.sup.2] area evacuated window with a highly insulating frame, An overall heat loss coefficient of 0.9 W [m.sup.-2] [K.sup.-1], with a midplane value of 0.36 W [m.sup.-2] [K.sup.-1], can be achieved with 0.72 visible transmittance for two 6 mm panes separated by 0.2 mm diameter pillars 40 mm apart. The conduction through a 3 mm edge-seal was 1.14 W [m.sup.-2] [K.sup.-1]. Detailed three-dimensional isothermal contour plots through the system are presented.

A theoretical and experimental investigation into the modifications in optical and thermal performance resulting from the introduction of a baffle into the cavity of a compound parabolic concentrating solar energy collector has been performed. Results are presented in the form of velocity vector diagrams and isothermal plots. A comparison is made of the collector loss coefficient and Hottel-Whiller-Bliss graphs are produced for cavities with and without a baffle present. The introduction of a baffle reduces internal convection thereby reducing heat losses. The associated reduction in optical efficiency is small.

A detailed parametric analysis of heat transfer in compound parabolic concentrating solar energy collectors has been performed, using a unified model for their optical and thermophysical behaviour. The effects of angular inclination and collector acceptance angles on free convection within the cavity are presented. The circumferential variation of local Nusselt number about the absorber is determined. A convective heat transfer correlation is obtained for the average Nusselt number with respect to Grashof number that takes into account acceptance angle and angular inclination. The developed correlation is extended to truncated compound parabolic concentrators.

A rigorous numerical simulation model for the prediction of the combined optical and thermofluid behaviour of line-axis concentrating solar energy collectors combines two-dimensional steady-state finite element analysis of convective heat transfer and ray-trace techniques. The optical analysis considers both direct and diffuse insolation components and is therefore useful for the analysis of compound parabolic concentrating collectors. Experiments using Mach-Zehnder interferometry indicate a parametric range for which such a two-dimensional representation is valid.