DIY Solar Food Dryer

A DIY solar food dryer that works well and the capital cost is virtually zero (make out of scrap materials), and the running costs are also nil. Below is a brief description and illustration of the dryer.

Many gardens have productive trees and the soft fruit -- peaches, apricots, etc -- have a tendency to ripen all at once. Eat local and eat healthier by preserving the goodness of your favourite seasonal foods, garden veggies, fruits and herbs to enjoy all year long.

Preserving by bottling is often put forward as a solution to this problem. Freezing the excess fruit is another option. However, both these methods are fairly energy intensive, and in terms of power consumption, the method of preserving which wins hands down is sun drying.

Dried fruit needs no special storage requirements and is also very convenient. Dried fruit can easliy be popped into lunch boxes, camping / hiking / boating / bicycle bags, snacks for car trips - something that's not so easy with bottled or frozen produce.

In addition to apples, apricots, peaches and bananas, try strawberries, pears, mangoes, kiwis, jakfruit, cherries. Dried pineapple tastes like candy, and melons are altogether wonderful: take away the water from a watermelon and all that's left is super-concentrated melon essence.

DIY Solar Food Dryer

There are no hard-and-fast rules on size, materials or shape, the sizes shown were used and therefore know they work.The dryer works simply: the radiation transmitted by the glass cover is absorbed by the blackened interior surfaces. The temperature of the air in the box rises. This box air rises and passes out of the upper set of holes by natural convection. The partial vacuum created in the box then draws in fresh air from outside via the holes in the base of the dryer. This gives a continuous flow of warm air around and over the fruit, which removes the moisture.

The illustration is pretty self explanatory. Make the length of the dryer at least three times the width. This will minimise the shading effects of the ends. Since most fruits are in abundance in the summer, make the angle of the glazing about 25 degrees to horizontal to maximise the entry of the summer sun.

If you want to dry fruits available in the shops during winter, such as apples and pears, an angle of about 55-60 degrees would be more suitable.

The number and position of the holes will determine the climate in the dryer.The more holes you have. the greater the airflow, but the lower the temperature.

Ideally you should have an airflow which is just enough to avoid condensation forming.

If you are fortunate to pick up a wood framed glass window, to a certain extent, this will govern the size of the dryer. A quick solution for the fruit trays is to make them out of recycled aluminium fly screens. These are simple to cut down to size.

However, this will also depend on the amount of moisture in the fruit.

The number and spacing of holes shown in the diagram worked well, but had to wipe condensation off the inside of the glass when drying plums probably indicated that there were not enough holes. However, it is no hassle and takes little time at all to do this.

You will find also that juicey fruits will drip and then the juice will caramelise and then burn, but you can easily clean the screens with hot soapy water.

Make the most of the long hot summer by drying your excess fruit and vegetable crops.Sunshine, drying is free and easy. It is easy to do and you will find the end product so much tastier than the bought variety. You will also know that no chemicals or preservatives have been used in its preparation.

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Reference Books

A good cheap reference book for information drying fuits and vegetables - How to Dry Foods (Paperback)
by Deanna Delong (Author) "Preserving foods when they are in season is not a new idea..."

Mary Bell's Complete Dehydrator Cookbook (William Morrow, 1994). The Lightweight Gourmet: Drying and Cooking Food for the Outdoor Life by Alan Kesselheim (Ragged Mountain Press, 1994), is full of recipes, menu planning tips etc.

Most books on backcountry cookery have sections on food dehydration; see, for example, Good Food for Camp & Trail by Dorcas S. Miller (Pruett, 1993); Camper's Companion by Rick Greenspan and Hal Kahn (Foghorn Press, 1993), and The Well-Fed Backpacker by June Fleming (Vintage Books, 1985).