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Solar Radiometer

Difficulty Level: 2/5 fairly easy

Parts and Tools

  • Small amount of aluminium foil
  • Candle
  • Matches
  • Scissors
  • Beaker or jar with lid
  • Petri dish or acrylic lid (for beaker)
  • Single long hair
  • PVA glue or similar
  • Flat knife

Instructions

This guide shows how to construct a solar radiometer. This radiometer consists of four squares of aluminium foil attached to a suspended match. These squares are painted black on one side and white on the other. When the device is exposed to direct sunlight or a strong artificial light or heat source, the vanes turn. Cooling causes the vanes to turn in the opposite direction.

Fig 1: Aluminium foil squares attached to match
Fig 1: Aluminium foil squares attached to match

Firstly four small squares of aluminium foil need to be cut. Each square should be about 3cm in length and height. The four pieces should be attached to a single match as shown in Fig 1. These can be glued in place using PVA and left to set.

Each square needs to be blackened on one side, with the bright sides all facing in the same direction. To do this, light a candle and carefully hold each square over the candle flame until soot has blackened the majority of the surface. Take care when doing this as the foil becomes obviously very hot. To assist in this, a knife can be held behind each foil piece.

Fig 2: Beaker
Fig 2: Beaker

Fig 2 shows a beaker of an appropriate size. A glass jar could also be used. A lid also needs to be selected that the foil pieces can be suspended from. The seal around the lid does not need to be air tight but should form a fairly good seal so that heat is trapped within the jar.

Fig 3: Hair attached to the match
Fig 3: Hair attached to the match

Fig 3 shows the hair which is attached to the match. Again, use glue to secure this in place. The thinner the hair or string, the more movement you are likely to see from the vanes so the thinner the better. This hair should be glued to the lid of the jar or beaker so that the vanes are suspended within the centre of the jar.

Fig 4: Completed model
Fig 4: Completed model

Fig 4 shows the completed model. This should be placed in direct sunlight for it to work most effectively.

Click here for more information about solar radiometers.

Disclaimer

Before attempting any of the construction projects featured on this website, ensure you have, and know how to use, the appropriate tools, components and safety equipment and are competent to undertake the project. These guides are for information only and we hold no responsibility for any accidents, injuries or damage caused by the use or misuse of any equipment, project or information contained within this website. In short - use common sense and stay safe!