Solar dryers are mainly devices which make use of solar energy and tap it to dry different kinds of substances. The concept is relatively simple as it involves converting light to heat and subsequently trapping the heat so that it can later be subjected to food to dry it up.
The Concept Of Solar Dryer
Let us take a closer look at how the whole concept of how a solar dryer works.
- Energy change: the first step is to trap any light which falls on it and convert it into heat. The presence of any black surface on the dryer is likely to push the effectiveness of the energy conversion substantially.
- The heat trap: The next step is to trap the heat so that it could be put to use later. This is why the air is isolated inside the dryer and separated from the one outside it. A plastic bag or a glass cover is used to make sure that light when entered inside is unable to move outside. Due to this mechanism, regardless of the outer weather and temperature, specific temperatures can be attained with the solar dryer.
- Transfer of heat: the final step is to apply the convection form of the heated air over the food or the substance which is to be dried by application of this trapped heat.
The Types Of Solar Dryer
There are ideally two different types of solar dryer namely
- Direct dryer
- Indirect dryer
The Direct Solar Dryer
This kind of device exposes the substance/food to be dried directly to sunlight. Previously, subjecting the food to the light of the sun could also be considered as a form of direct solar drying. In recent times, the drying racks and even the solar tents could act like the right example for direct solar drying. You will also find black absorbing surface in use in recent times. The substance to be heated is directly placed on it.
Indirect Solar Dryer
In this form of device, the black surface ends up heating the incoming air instead of directly heating the substance which is to be dried. It is this heated air which is then passed on to the substance until it gets heated and dried completely. Once the work is done, the heat is then moved upwards and subsequently removed with the help of a chimney. Once again, the designs are really simple and they are open to modifications based on the requirements and needs.
The basic concepts and design of a solar dryer are easy for anyone to come up with the desired modification. Also, one can make apt use of the solar light for heating and drying of different products/food and thereby preserving it.