![]() ![]() having maximum y = D/2), height h and focal length a, then equation 1 becomes:Ī simple curved plane (rather than dish shape) solar heater is shown in photo 1 and we shall use this as an example, of course what follows can also be used for a full 'dish shaped' parabola and for much larger designs.įigure 2. If we want to make a parabolic reflector to our own particular specification i.e. Light rays coming from infinity will tend to be reflected towards a point called the focus. The constant a is known as the focal length - the distance from the origin to the focus point.įigure 1. ![]() Where y represents the distance away from the mirror centre and x represents the 'height above' the centre, see figure 1 and 2. The basic shape of a parabola is derived from the equation: You can use this energy to heat something. The parabolic mirror therefore directs the energy arriving over its surface to a 'hot spot' at the focus. When Sun light (parallel rays) falls onto a correctly aligned parabolic mirror it will be reflected back towards a single point known as the focus. The shape of the parabola is given by equation, see table 1. Apart from the screws and plastic mirror all the parabola 'bits' were made from scrap. There is a black temperature data logger at the focus which is where the solar energy is being concentrated. Two photos of a small solar heater made from plastic mirror sheet bent into a parabola shape by a wooden template. Here we explore the parabola to design solar heaters. You find them built into car headlights, spotlights as well as astronomical telescopes. ![]() Parabolic mirror surfaces are found wherever energy needs to be focused efficiently and accurately. Note: for details of talks and workshops on this topic click here: 42 (2007) 267-270 and is here reproduced by permission of IOP) (Note: this article has been published: J. Solar heaters and other parabolic devicesīy Dr Jonathan Hare, The Creative Science Centre, Sussex University ![]() Full 2 Year Warranty.The Creative Science Centre - by Dr Jonathan P. For use with Compact Fluorescent (CFL) Lamps up to 250w. Ventilated 'Heat Escape' top plate ensures minimal heat build up.įor use with Sodium (HPS) or Metal Halide (HQI) Lamps & Bulbs up to 1000w. Vertical burning bulb/lamp allows you to position your reflector closer to your plants and reduce hotspots. The Medium and Large Parabolic are supplied unassembled For use with: 150w to 1000w HPS & MH Bulbs or 125w to 250 CFL Bulbs.Ī High Quality Reflector constructed of Highly Reflective Polished Hammertone Aluminium. Although the light is less intense, this set-up provides a good even distribution of light over a wide area. So it could be said to be less efficient than the vertical alternative. Reflectors like this are very popular in the US! With horizontal bulbs a good quarter to a third of the light goes straight up into the reflector before passing down again. It has a vertical lamp and air vents, which allows a lot of heat to escape. Parabolic reflectors often have a more precise and uniform spread of light. The Parabolic is available in large and medium sizes. Parabolic Silver Reflector vertical supplied with vented top plates to disperse heat build up. The benefit of vertical reflectors is that you can position them closer to your crops creating an even canopy of light coverage without hot spots. Parabolic Silver Reflector vertical with E40 Socket ![]()
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