Cutting and drilling plans for flat metal segments to make an approximate

parabolic reflector suitable for a solar concentrator or solar cooker

parabolic reflector suitable for a solar concentrator or solar cooker

(dx)² : square of incremental change in x

(dy)² : square of incremental change in y

dS : incremental change along strip

parabola : y=x²/300

focal length =75

calculation radial increment= 2 ; results (diam.) shown every 10

Diam. | Arc length | arc' | hole c/c | Eff. area /m² | P max/W |
---|---|---|---|---|---|

55 | 0 | 0 | 8.2 | 0 | 0 |

75 | 10.233 | 10.1 | 11.2 | 0.2042 | 184 |

95 | 20.629 | 20.4 | 14.2 | 0.4712 | 424 |

115 | 31.225 | 30.9 | 17.2 | 0.8011 | 721 |

135 | 42.061 | 41.6 | 20.2 | 1.1938 | 1074 |

155 | 53.169 | 52.6 | 23.2 | 1.6493 | 1484 |

175 | 64.584 | 63.9 | 26 | 2.1677 | 1951 |

195 | 76.334 | 75.5 | 29 | 2.7489 | 2474 |

215 | 88.446 | 87.5 | 32 | 3.3929 | 3054 |

235 | 100.946 | 99.8 | 35 | 4.0998 | 3690 |

255 | 113.857 | 112.6 | 38 | 4.8695 | 4383 |

268 | 123.86 | 122.5 | 40 | 5.4034 | 4863 |

Diam. | Arc length | arc' | hole c/c | Eff. area /m² | P max/W |

segments per sheet=8;

Number of sheets (250 cm x 125 cm) required for 21 segments = 3

Possible suppliers of reflective Al sheet:

Alcan "Eloxal" - manufacturer (worldwide corp. find your local distributor)

Alanod Mirosolar. German company, UK/US Offices

(avoid stainless steel which absorbs IR and gets hot.)

Care should always be taken when designing and using solar concentrators to avoid the possibity of burns. Please note that concentrated

The above tables are calculated by numerical integration of the arc of the parabolic section as follows:

Determine the quadratic equation of parabola from diameter and focal length.

Use incremental changes in x and y and pythagorus to calculate incremental lengths along parabola arc.

Sum to obtain successive drilling points, use cosine of semi-angle to project distances onto segment centre line

Use sine of semi-angle to find distance between hole pairs as a chord of each circlular cut through paraboliod.

Add selected clearance for drilling and plot sheet metal plan.

The power is the product of the effective area taken perpendicular to the axis of the paraboloid, the insolation and the reflectivity of the sheet.

The information on this page is provided AS IS. The author and domain owners make no waranty, expressed or implied of it's suitability for a given purpose.

This page is generated by a PHP script as a function of the data entered, not by fully engineered software. It has not been thoroughly tested under extreme conditions and results should not be used in critical applications, including but not limited to : life-support systems, nuclear power stations, aerospace applications, guided missile systems, penile temultulance detectors, etc.

If you are designing a parabolic solar reflector the results should be reliable enough.

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