A fully integrated renewable energy atlas is presented which provides the wind and solar photo-voltaic (PV) power generation potential as well as cooling demand for Pakistan at a temporal resolution of 1-hr and spatial resolution of 14x14 km 2. The proposed atlas uses weather based modelling for calculating renewable power generation time-series and the power-demand modelling is performed using real hourly electrical-load demand, conventional power generation and power consumption data for the year 2016. It has been found that Pakistan has much higher potential for the wind power generation than solar (PV) power generation and very good potential for the concentrated solar power. Furthermore, the optimum wind/solar power mix suggests that 95% of wind power generation and 5% of solar (PV) power generation leads to the least amount of power-shortfall. It is envisioned that the integration of renewable energy with cooling sector can be instrumental in overcoming Pakistan's electrical power-crisis. The current power-shortfall of 38.36 TWh can be resolved by installing rated wind and solar (PV) power generation capacity of 10.4 GW and 882 MW, respectively.

A new multilayer slip‐flow model has been developed to simplify and to overcome current numerical difficulties of two‐dimensional model in predicting the internal air temperature inside a mold during a rotational molding process. The proposed methodology considers a macroscopic “layer‐by‐layer” deposition of a heating polymer bed onto the inner mold surface. A semi‐implicit approach is introduced and applied to compute the complex thermal interactions between the internal air and its surroundings. In the model, the lumped‐parameter system and the coincident node technique are incorporated with the Galerkin finite element model to address the internal air and the deposition of molten polymer beds, respectively. The simple phase‐change algorithm has been proposed to improve the computational cost, numerical nonlinearity, and predicted results. The thermal aspects of the inherent warpage are explored to study its correlation to the weak apparent crystallization‐induced plateau in the temperature profile of the internal air, as in practice. The overall predicted results are in favor with the available experimental data for rotomolded parts of cross‐sectional thicknesses up to 12 mm. POLYM. ENG. SCI. 46:960–969, 2006. © 2006 Society of Plastics Engineers

This article details steps in creating low-power artificial muscles using 3D printing. It describes a manufacturing system that can be used to fabricate seamless tubular dielectric elastomer actuators (DEA), for eventual use in biorobotic devices. The focus is on producing passive elastomeric components of DEA and the dimensional changes that occur after printing is complete. A four-axis printing system is described, capable of spray depositing multilayer tubular silicone membranes onto an air-permeable mandrel. Mechanical strain was imparted in the membranes by means of inflation. A laser measurement system was constructed to act as a 3D scanner, which measured the shape of the inflated ''balloon.'' The surface shape was reconstructed in software using the parametric modeling tool Grasshopper. Seamless auxetic tessellations were calculated across the entire surface, and then converted to CNC GCode. These toolpaths were then physically extruded over the surface of the balloon, stacked five layers high. When the extruded silicone structure was completely cured, the pneumatic strain was released, allowing the structure to collapse evenly. The compression in the printed structure was balanced by the tension in the stretched membranes, thus producing a minimum energy structure.

This article is the second in a two-part series describing a process for conformal 3D printing onto inflated substrates. The article describes the design and build of a custom-built four-axis 3D printer with the ability to measure the shape of any uneven substrate, and to then accurately extrude a thixotropic silicone onto the substrate by using Direct Ink Writing techniques. Details of strategies for 3D scanning a double-curved tubular inflated substrate using an industrial triangulation laser measurement device are given. Methods to import scan data and create a digital representation of the surface within the parametric design software Grasshopper 3D are explained. Geodesic print paths are created over the surface of the computed substrate, and these are the basis for calculating 3D printer toolpaths. A constant surface linear velocity strategy is developed, allowing the printer to move the print nozzle at a varying speed over the substrate surface. The change in speed is correlated with changes in the surface linear velocity of a fourth axis rotation of the variable radius balloon substrate. This ensures that the extruded bead maintains a constant thickness, even while using a constant flow rate deposition. The process is achieved by adapting cartographic techniques to re-project to the desired print paths. The efficacy of this technique is analyzed by 3D scanning a printed patterned balloon, then measuring and comparing multiple cross-sections of the extruded beading.

In the rotational moulding process, the internal air temperature has been widely recognised as a tool to predict an optimum cycle time. This paper presents a new numerical approach to predict the internal air temperature in a two-dimensional (2-D) static model without requiring the consideration of the tumbling motion of polymer powder. The initial non-isothermal heating of the static model is actually formed by two changeable plastic beds (stagnant and mixing beds), which represent the actual stagnant and mixing pools inside a rotating mould respectively. In the numerical approach, the lumped-parameter system and coincident node technique are proposed to incorporate with the Galerkin Finite Element Method in order to account for the complex thermal interaction of the internal air. It helps to overcome the difficulty of multidimensional static models in predicting an accurate internal air temperature during the heating stage of rotationally powdery plastic. Importantly, the predicted temperature profiles of the internal air, oven times for different part thicknesses and process conditions accord with the available experimental results.PRC/2029