Using CUDA for Solar Thermal Plant Computation. Background Problem Solution Algorithm Polygon Clipping Why CUDA? Progress

Our Team. Claus Nilsson Sahithi Chalasani Pranav Mantini Arun Kumar Subramanian

Instructor:Dr.Bun yue Mentor:Michel Izygon

Background Structure  Central receiver A type of solar furnace. Receives the sunlight redirected by Heliostats.  Heliostat A type of mirror. redirects sunlight towards the central receiver.

Background. Field  Generally huge  Heliostats are placed in a radial stagger formation.  Broken into Grids containing cells.  Each cell has one representative heliostat and about 8 to 80 neighbor(hypothetical) heliostats.

Background. Shading and Blocking.  A field of heliostats suffers loss in efficiency caused by shading and blocking by neighbouring heliostats.  For our purpose we assume that shading and blocking occurs only within a cell.  Shading is the loss of illumination on a given mirror due to the interception of the incident sunlight by a neighboring mirror. [3]  Blocking is the loss of illumination on the central receiver due to the interception of reflected sunlight by another neighboring mirror. [3]

Background.

Problem. Solar thermal fields in general have considerably large number of heliostats. A computation algorithm to calculate shading and blocking has been designed and implemented by Tietronix Software, Inc. This computation algorithm takes significant amount of time to calculate shading and blocking for thousands of heliostat. The objective is to decrease the computation time.

Solution. To increase the efficiency of this computation algorithm, Tietronix Software, Inc. has proposed to create an application that computes the shading and blocking among the heliostats simultaneously. For this purpose, CUDA(Compute Unified Device Architecture), a parallel computing architecture was chosen.

Algorithm. An algorithm was designed by Mr. Peter Armstrong of Tietronix Software, Inc., to calculate the shading and blocking among the heliostats.[4] This algorithm makes use of Vector Mathematics, including vector projection and a polygon clipping algorithm.

Algorithm.

Shadingv Shading

Algorithm.

Polygon Clipping. Sutherland-Hodgman Algorithm:  Most used algorithm for clipping convex polygons.  Uses a divide-and-conquer strategy.  Window must be a convex polygon  Polygon to be clipped can be convex or not

Example The original polygon and the clip rectangle.

Example After clipped by the right clip boundary.

Example After clipped by the right, bottom, and left clip boundaries.

Example After clipped by all four boundaries.

Why this algorithm? It is relatively simple. Relatively straightforward and is easily implemented in C. Very efficient in two important cases. i) when the polygon is completely inside the boundaries. ii) when it's completely outside.

CUDA What is CUDA ◦ Scalable programming model and ◦ Software environment for parallel computing [2] ◦ Extension to the C programming language

CUDA What CUDA does  Allows utilization of GPU  Allows parallel execution of code Kernels  Manages threads automatically Exception: __syncthreads()‏

CUDA Example Source: “Parallel Processing With CUDA” by Tom R. Halfhill [1]

CUDA Scaling

CUDA How does it work

CUDA

Progress. Two Tower Demo. Full Cell. (linear)‏ Full Cell. (Parallel)‏ Full Grid. (linear)‏ Full Grid. (parallel)‏

Progress. Two Tower Demo:  Successfully calculated the vertices of the neighbor and the representative heliostat.  Working on the projected vertices and polygon clipping algorithm. Full Cell Demo:  Created the eight neighbors and generated the unit normal vector to the heliostats  Working on the vertices and projected vertices.

Progress. Two Tower Demo.  Input: Tower height meters. The coordinates of the center of each heliostat are: 2002(source) (neighbor) Heliostats - 5 meters by 5 meters square. sun azimuth degrees. sun elevation degrees. Date - 20 March 2008 at 07:07:27.4 UTC with the field origin located at latitude 0, longitude 0, elevation 0.

Progress. Full Cell Demo.  Input: Tower height meters. Heliostats meters by 4.5 meters square. no. of rows, columns – 10 & 10 respectively. Row and column of the tower – 10 & -1 respectively. Date - 09/22/ :40: UTC-8 sun azimuth degrees. sun elevation degrees. Site – elevation 670 latitude longitude

References [1] Tom R. Halfhill. Parallel Processing With CUDA. Microprocessor, 01/28/08-01, f f [2] Greg Ruetsch, Brent Oster. Getting Started with CUDA. Getting_Started_w_CUDA_Training_NVISION08.p df

References [3] Lipps, F. W.; vant-Hull, L. L., Shading and blocking geometry for a solar tower concentrator with rectangular mirrors, American Society of Mechanical Engineers, Winter Annual Meeting, New York, N.Y., Nov , 1974, 7 p. NSF- supported research. [4] Peter Armstrong, An Algorithm For Shading And Blocking Computation Of A Field Of Heliostats Arranged In A Grid Layout.

References [5] Polygon clipping,  ClippingApplets%20Folder/Sutherland- Hodgeman/index.html   y.pdf  wei.Hsieh/Haowei.Hsieh/sec3_step.html

Thank You! Any Questions?