Natural Resources, 2010, 1, 88-94
doi:10.4236/nr.2010.12009 Published Online December 2010 (http://www.SciRP.org/journal/nr)
Indirect Solar Drier with Electric Back up System
for Quality Hill Products
Rajeev Kumar Aggarwal1, Madan Mohan Sharma2, Ashwani Kumar Sharma2
1Department of Environmental Science, Dr Y S Parmar University of Horticulture & Forestry, Nauni (Solan), India; 2Department of
Basic Sciences, Dr Y S Parmar University of Horticulture & Forestry, Nauni (Solan), India.
Received October 25th, 2010; revised November 23rd, 2010; accepted December 3rd, 2010.
ABSTRACT
An indirect solar drier of 25 kg capacity has been developed fitted with solar cell for running the fan. The bulbs are
provided in the solar collector for air heating during clouds and evening & morning for faster drying reducing drying
time. Various hill crops (Punica granatum L, Ginger, Turmeric and Red chili) have been dried in open sun, oven and
solar drier for quality/caparison. The dried products were tested in the post harvest technology laboratory for value
addition. The market value of dried products has also been compared.
Keywords: Solar Drier, Drying, Hill Crops, Quality, Income Generation
1. Introduction
The Himachal Pradesh is a hilly state known as fruit
bowl of India. Large quantities of fruits and vegetables
are damaged due to perishable nature/bad weather or lack
of transportation facilities resulting in loss to the farmers.
About 20% tomato, 10% ginger, 10% mushroom, 30%
amla (Emblica officinalis) and 5% apple are generally
damages/waste during a year. People in the state dries
fruits apple, peach, palm nut, and vegetables chilly, tur-
meric, ginger and pomegranate in open sun resulting
poor quality of the dried product due to dust/fungus in-
fection, insects, sudden rains, bacteria and loss due to
wetting by rainsqualls wild animals and monkeys etc..
The part of perishable crops like tomatoes and pome-
granate harvested during rainy season are wasted due to
bad weather. This gives low return to the farmers. The
open sun drying requires more time and labour to carry
products from inside to outside during bad weather. Solar
drying of fruits and vegetables can reduce the losses and
improve the quality of products for better price in the
market. Several types of driers are available in the coun-
try but these are not popular in rural areas due to high
costs, technical know how, or lack of skill to use these
driers [1]. An indirect solar powered drier has been de-
veloped for the drying of fruits, vegetables, seeds and
medicinal plants. This drier reduces the drying time con-
siderably as it provides heat during night through bulbs.
The quality of the products improves for better market
values. The pay back period of the drier is less because
the drier will be used throughout the year. The major
portion of the initial expenditure on fabrication of drier is
on wood, which is easily available with the farmers. Thus,
the total cost of the drier will be reduced which can be
recovered in shorter span. The hill products dried for
commercial use are presented in Table 1.
Table 1. Calendaring of hill crops dried for commercial use.
Crop to be dried
Month of
harvesting FruitsVegetables/Seeds Medicinal plants
January Turmeric, Methi,
Sarson,
February Amla Brass, Guchhi
March Bnaksha,
April Peas, Garlic
May
June Mango
July Beans, Potato,
Pumpkin
August Anardana, Kala Jeera,
September Red Chilly, Maize
October
Apples,
Walnut,
Apricot,
Almond
Ginger Brahme, Kesar
November
December
Mulhathi, Tulsi,
Sarpgndha, Ashwa-
gandha, Jatamansi

Indirect Solar Drier with Electric Back up System for Quality Hill Products
89
Pomegranate has great economic importance because
of its high acetic nature. Nearly 1000 tones of dried
anardana extracted from wild pomegranate fruits costs
about $ 3.0 billions. Wild pomegranate is widely found
in dried and sub-marginal land of mild hill region of out-
er Himalayas at an altitude of 400 m to 1,800 m above
mean sea level. In India it grows in vast track of the hill
slopes of Jammu & Kashmir, Himachal Pradesh and Ut-
ranchal. In Himachal Pradesh it is found in Solan and
Sirmour districts in abundance. The size of fresh pome-
granate varies from 5.31 cm to 7.53 cm and diameter
varies from 4.35 cm to 6.50 cm. The weight ranges be-
tween 59.77 gm to 101.0 gm. The average weight of 100
arils is 12.65 gm and its colour is blood red-light pink.
Ginger is one of the important spice crops that are
preferred for its therapeutic values. An herbaceous per-
ennial plant, belonging to family Zingiberaceae is be-
lieved to be native of south East Asia. It is propagated
through rhizomes, leafy stem 30-90 cm in height. It is
widely used in food beverages, confectioneries and med-
icine. Total production in the world is 1004546 metric
tones and total world area under cultivation is 33826
hectares. The average productivity of the world is 2956
kg/hectare. Major ginger producing countries in the
world are India, Nigeria, China, Thailand, Indonesia,
Bangladesh, Philippines and Korea. Nigeria ranks first
with respect to area under ginger covering about 56.23%
of world total area under ginger followed by India
(23.60%), China (4.47%), Indonesia (3.37%) and Bang-
ladesh (2.32%) India ranks first with respect to ginger
production contributing about 32.75% of total world’s
ginger product followed by china (21.41%), Nigeria
(12.54%) and Bangladesh (10.80%). India is the largest
producer of dry ginger. The total production of ginger in
India is 305900 tones in an area of 85100 hectare with an
average production of ginger 3.60 metric tones per hec-
tare. In India, Kerla is the highest producer of ginger
contributing almost 23.08% of country’s total production
followed by 19.57% in Meghalaya. Major ginger pro-
ducing area in country is Karnataka Tamil Nadu, west
Bengal, Himachal Pradesh, UP, Orrisa Gujart, Maharastra,
Rajasthan and North-Eastern states [3]. In Himachal
Pradesh, ginger is one of the important cash crops of mid
and lower hills covering an area of 3695 hectares and
total production is 37,000 tones. In Himachal Pradesh,
this crop is mainly grown in Sirmaur, Solan, Hamirpur,
Bilaspur, Mandi and Shimla districts.
2. Methodology
The drier has been developed under the project funded by
the Ministry of Science and Technology, Government of
India. A survey was conducted to identifying the drying
techniques of the farmers and to identify the commercial
crop which are being dried. On the basis of this survey an
indirect solar drier has been developed. The design pa-
rameters of the drier have been presented in Section 1).
The results and discussion is presented in Section 2). The
economics of drying has been discussed in Section 3).
1) Design parameters of the drier
The solar drier of 25 kg capacity has two components.
One a solar collector constructed with water proof board
fitted with 4 mm glass at an angle of 30o (the latitude of
the place) for maximum transmission of solar radiation
(drawing is enclosed) [2]. Solar collector with a glass
area of 2.4 square meter and volume is 0.693 m3. The
solar collector base has black painted plywood to ab-
sorbed solar radiation insulated with saw dust. The dry-
ing chamber with dimension of 1.1 m * 0.7 m * 1.0 m
has three removable trays. Each tray with size of 1.02 m
* 0.7 m * 0.05 m is made of iron square mesh in wooden
border. Front side of drying chamber is covered by glass
having thickness of 6 mm. The eight bulbs of 100 W
each are provided in the solar collector for heating during
rains and after sunset to reduce the drying time. The holes
are provided at the bottom (south orientation) in solar col-
lector. A dc fan is provided at top of the drying chamber
(north orientation) for air circulation. A solar battery has
been attached with the drying chamber to run the fan. A
schematic view and camera photograph of solar drier are
presented in Figure 1 and Figure 2 respectively.
2) Result and discussion
The three samples (solar dried, open sun dried, oven
dried) of each dried products were given for value addi-
tion test to the Department of Post Harvest Technology,
Dr Y S Parmar University of Horticulture & Forestry,
Nauni (Solan) India. No preliminary chemical treatment
was given to the products to be dried. Drying results of
pomegranate which are presented in Table 2 reveal that
reducing sugar was found maximum (21.70%) in the arils
dried in indirect solar drier while minimum (20.25%)
was in open sun. The total sugars were found maximum
(24.18%) in arils dried in indirect solar drier and mini-
mum (22.60%) in open sun. The maximum titratable
acidity (13.71%) in the arils dried in oven, whereas
minimum titratable acidity of 12.40% was observed in
the arils dried in open sun. The electric oven was used
for drying at constant temperature. Data on the effect of
drying modes on the ascorbic acid content show that in-
direct solar dried arils had maximum (12.09 mg/100 g)
ascorbic acid, whereas open sun dried arils had minimum
(7.85 mg/100 g) ascorbic acid. Data pertaining to the
effect of drying modes on the visual colour of arils indi-
cate different colour shades of pink to light brownish.
Arils dried in indirect solar drier had pink colour, which
was most attractive as compared to the other two modes.
Brownish pink colour of arils was observed in oven

Indirect Solar Drier with Electric Back up System for Quality Hill Products
90
Figure 1. Design of indirect solar drier.
samples, whereas, least attractive light brown colour was
observed in the arils dried in open sun. Minimum (7.58%)
moisture content was recorded in the arils dried in oven,
whereas maximum (11.32%) moisture content observed
in arils dried in open sun. The time taken to dry the po-
megranate is 21 hours in solar drier. The eight bulbs were
remained on during sunset which resulted in continuous
heating. The temperature variation with time during the
drying of pomegranate has been presented in Figure 3
and moisture content variation with time in case of po-
megranate has been presented in Figure 4.
Data pertaining to the effect of drying modes on the
visual colour of zinger indicate different shades of origi-
nal yellow to dull. Zinger dried in indirect solar drier had
original yellow colour, which was most attractive as
compared to the other two modes. Greenish yellow col-
our observed in the sun sample, whereas, as least attrac-
tive dull colour observed in the oven sample. Minimum
(5.88%) moisture was recorded in the zinger dried in
oven, while maximum (9.54%) moisture observed in
zinger dried in sun. The moisture content (9.3%) between
other two modes was observed in indirect solar drier.
Maximum (5.25%) oleoresin oil on dry weight basis was
recorded in the indirect solar drier where as minimum
(4.79%) oleoresin oil was recorded in open sun sample.
This shows that in indirect solar drier the oil erosion was
less as compared to other modes. The drying time of
ginger is 20 days in solar drier. The eight bulbs were
remained on during sunset which resulted in continuous
heating. The moisture content could not be recorded due
to instrument failure although the drying was continued.
The temperature variation and moisture content variation
with time in case of ginger have been presented in Fig-
ure 5 and Figure 6 respectively.

Indirect Solar Drier with Electric Back up System for Quality Hill Products
91
Figure 2. Indirect solar drier.
Table 2. Value addition test results of various dried products.
Anardana
Characteristics Open sun Oven Solar drier
Reducing sugar (%) 20.25 21.20 21.70
Total Sugar (%) 22.60 23.49 24.18
Titratable acidity (%) 12.40 13.71 13.09
Ascorbic acid (mg/100 gm) 7.85 10.39 12.09
Moisture content (%) 11.32 7.58 9.02
Colour Light brownish Brownish pink Pink
Ginger
Colour Greenish yellow Dull Original yellow
Oleoresin (%) on dry wet basis 4.79 4.98 5.25
Moisture content (%) 9.54 5.88 9.3
Red Chili
Colour Light red Blackish dark red Redish pink
Moisture content (%) 11.94 6.38 7.34
Turmeric
Colour Light redish yellow Blackish yellow Dark redish yellow
Moisture content (%) 11.37 7.59 9.23

Indirect Solar Drier with Electric Back up System for Quality Hill Products
92
Figure 3. Temperature variation with days in three modes of drying of pomegranate.
Figure 4. Moisture content variation during month of November and December in case of pomegranate.
Figure 5. Temperature variation during month of November and December in case of ginger.

Indirect Solar Drier with Electric Back up System for Quality Hill Products
93
Figure 6. Moisture content variation during month of November and December in case of ginger.
Table 3. The cost per unit capacity of different products.
Product
Item
Pomegranate Turmeric Ginger Chilli
Electricity charges (Rs.) 25.92 16.2 87.48 12.96
Maintenance charges (Rs.) 100 100 100 100
Labour charges (Rs.)
Loading
Operating cost
6.9
3.68
6.9
2.3
6.9
12.42
6.9
1.84
Depreciation charges (Rs.) 22.4 14.0 75.6 4.2
Cost per unit capacity 6.36 5.57 11.29 5.04
Table 4. Rates (Rs./kg) of dried products in the local market.
Product Open sun dried Oven dried Solar drier dried
Anardana 170 170 190
Ginger 190 195 210
Red chilly 115 105 130
Data pertaining to the effect of drying modes on the
visual colour chilli indicate different colour shades of
light red to reddish pink. The colour of chilli dried in
indirect solar drier was most attractive than the other two,
modes. Minimum (7.34%) moisture content recorded in
the chilli dried in oven whereas maximum (11.94) mois-
ture content recorded in the open sun sample. Moisture
content (6.38%) was recorded in the indirect solar drier
sample.
Data pertaining to the effect of drying modes on the
visual colour turmeric indicate different colour shades of
reddish dark yellow to light reddish yellow. Colour of
turmeric dried in indirect solar drier was most attractive
than the other two, modes. Minimum (7.59%) moisture
content recorded in the turmeric dried in oven whereas
maximum (11.37%) moisture content recorded in the
open sun sample. Moisture content (9.23%) was recorded
in the indirect solar drier sample.
3) Economics of drying
The cost per unit capacity of various dried products
have been calculated taking into account the cost of drier,
labour charges, maintenance charges, electricity charges
and depreciation charges [4]. The cost of dried product
has been found to be in the range of Rs.5 to Rs.6 per kg.

Indirect Solar Drier with Electric Back up System for Quality Hill Products
94
The details are presented in Table 3.
3. Market Value
The dried products were taken to the local market for
assessing the rates of these products. It was found that
rates of solar dried products are higher than the dried
products by other methods. The rates are presented in
Table 4.
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