• Energy Research
• Closed Access close
• CA close
• EC close
• Solar Energy close

Abstract Empirical equations have been developed which correlate the monthly average daily horizontal diffuse and beam radiation with the fraction of maximum possible number of bright sunshine hours. These correlations are based on measured data from three widely spread Canadian stations. Depending upon whether or not the total horizontal radiation is known, the two correlations for the diffuse radiation are: H d H =0.791−0.635 n N H d H o =0.163+0.478 n N −0.655 n N 2 . The correlation for beam radiation is: H d H o =0.176+1.45 n N −1.12 n N 2 , for n > 0 .

Abstract The heating of domestic hot water (DHW) to supply bathing, cleaning, and appliance needs contributes significantly to energy demands in housing. Despite the demonstrated significance of DHW draw profiles on performance, it is common practice when analyzing solar DHW and solar combisystems to conduct long-term simulations (e.g. annual) using repeating daily profiles. New DHW profiles that can be used for such analyses have been developed based upon measurements that were taken in 73 houses in Quebec (Canada). Annual DHW draw profiles at a time-resolution of 5 min have been created for 4 consumption levels and 3 temporal consumption patterns (sparing consumers who tend to use DHW in the mornings, average consumers who tend to use DHW in the evenings, etc.). Simulations of a solar DHW system conducted with these new profiles revealed that both temporal and annually integrated predictions can be significantly affected by timing of DHW draws.

Abstract We propose a novel design for a solar updraft tower, wherein the chimney that generates the updraft is a self-supporting, free-standing stack of hollow gas-filled tori. Considerations for the design stabilizing the structure via a combination of shape, overpressure, and buoyancy are presented. Filling the tori with air rather than with a light gas may be advantageous for stability. The chimney shapes are optimized for deformation under wind loading. We also present simple cost calculations and results of CFD modeling to confirm the viability of the design.

Abstract Steady natural convection heat transfer has been studied in a modified Trombe wall solar collector with a porous medium used as an absorber. The boundary conditions were: Two isothermal walls at different temperatures, two horizontal bounding adiabatic walls and either uniform or nonuniform heat generating porous layer with orifices. The aspect ratio A was from 5 to 10. The influence of orifice opening and position as well as the nonuniform heat generation within the porous medium have been studied in detail with the Darcy number varying from 10−8 to 10−2. The results are presented in terms of practical parameters (θ, θmax, q) as a function of Ra, Da and other nondimensional geometrical parameters. The isotherms and stream lines within the cavity are also produced. The overall results indicate that Da and geometrical parameters are the most important parameters affecting system performance.

Abstract Unglazed transpired plate solar air heaters have proven to be effective in heating outside air on a once-through basis for ventilation and drying applications. Outside air is sucked through unglazed plates having uniformly distributed perforations. The air is drawn into a plenum behind the plate and then supplied to the application by fans. Large collectors have been built that cover the sides of sizeable buildings, and the problem of designing the system so that the air is sucked uniformly everywhere (or nearly so) has proven to be a challenging one. This article describes an analytical tool that has been developed to predict the flow distribution over the collector. It is based on modelling the flow-field in the plenum by means of a commercial CFD (computational fluid mechanics) code, incorporating a special set of boundary conditions to model the plate and the ambient air. This article presents the 2D version of the code, and applies it to the problem of predicting the flow distribution in still air (no wind) conditions, a situation well treated by a 2D code. Results are presented for a wide range of conditions, and design implications are discussed. An interesting finding of the study is that the heat transfer at the back of the plate can play an important role, and because of this heat transfer, the efficiency of a collector in non-uniform flow can can actually be greater than that of the same collector in uniform flow.