Solar Food Processing and Cooking Methodologies

Abstract

In this study, a theoretical analysis of food processing (e.g., solar drying), worldwide cooking pattern, and cooking methods by using the solar energy has been reviewed. Solar food processing method is applied as direct absorption, air heater, and a combination of direct and indirect drying by solar radiation. Therefore, this process is one of the most accessible and hence the most widespread processing technologies. Traditional solar drying involves keeping products in the direct sunlight. Solar drying and cooking processes take place at different temperatures and timescales, and it depends on the nature of the food or substance. The amount of solar energy that reaches to the system and design parameters determines the performance of food processing and cooking systems. The time duration of drying and cooking depends on the temperature of heated air and environment. The temperature distributions, mass, and ingredient of food have an important role in the performance of dryers and cooker boxes. For a better understanding of the system parameters, the concept of solar food processing has been discussed thermodynamically. Energy saving by using solar systems has also been discussed.

Full text

Solar Food Processing and Cooking
Methodologies
Abhishek Saxena, Varun Goel and Mehmet Karakilcik
Abstract In this study, a theoretical analysis of food processing (e.g., solar drying),
worldwide cooking pattern, and cooking methods by using the solar energy has
been reviewed. Solar food processing method is applied as direct absorption, air
heater, and a combination of direct and indirect drying by solar radiation. Therefore,
this process is one of the most accessible and hence the most widespread processing
technologies. Traditional solar drying involves keeping products in the direct
sunlight. Solar drying and cooking processes take place at different temperatures
and timescales, and it depends on the nature of the food or substance. The amount
of solar energy that reaches to the system and design parameters determines the
performance of food processing and cooking systems. The time duration of drying
and cooking depends on the temperature of heated air and environment. The
temperature distributions, mass, and ingredient of food have an important role in the
performance of dryers and cooker boxes. For a better understanding of the system
parameters, the concept of solar food processing has been discussed thermody-
namically. Energy saving by using solar systems has also been discussed.
Keywords Solar food processing ⋅Solar drying ⋅Cooking methodologies
Energy analysis
A. Saxena (✉)
Mechanical Engineering Department, Moradabad Institute of Technology,
Moradabad 244001, India
e-mail: culturebeat94@yahoo.com
V. Goel
Mechanical Engineering Department, National Institute of Technology,
Hamirpur, India
M. Karakilcik
Faculty of Sciences and Letters, Department of Physics, University of Cukurova,
Adana 01330, Turkey
© Springer Nature Singapore Pte Ltd. 2018
H. Tyagi et al. (eds.), Applications of Solar Energy, Energy, Environment,
and Sustainability, https://doi.org/10.1007/978-981-10-7206-2_13
251

Nomenclature
Symbols
PBP Payback period
x Interest rate
yInflation rate
Z Manufacturing cost of cooker
M Maintenance cost
E Energy saving per year
FC Fuel combusted per year
OF
fc
Fuel oxidation factor
HHV
fc
Fuel higher heating value
CCC
fc
Carbon content coefficient
MW
CO2
Molecular weight of CO
2
MW
c
Molecular weight of carbon
E Energy
zdT Drop in temperature
MC Heat capacity
Q Heat
F Heat exchanger efficiency factor
L Latent of heat vaporization
W Weight of water evaporated
LCV Lower calorific value of fuel
P
f
Power of fan
Mb Mass of fuel consumed
Asc Crop surface area
K
f
Thermal conductance of air
K
m
Mass transfer coefficient of vapor
P
v
Vapor pressure
Subscripts
o Output
in Input
avg Average
w Water
wf Final
if Initial
th Thermal
amb Ambient
pm Plate mean
i Insulation
p Plate
c Glass cover
w Wind
252 A. Saxena et al.

L Loss
a Air
d Dried substance
sc Solar collector
e Equilibrium
Greek letters
ɛEmissivity
τDrying time
ηEfficiency
λLatent heat evaporation
1 Introduction
Sun is a very large, inexhaustible source of energy. The power from the sun
intercepted by earth is approximately 1.8 × 10
11
MW which is many thousands of
times larger than the present consumption rate on earth of all commercial energy
sources. Smoke caused by cooking and heating is the main cause of many respi-
ratory diseases altogether with environmental pollution. The World Bank’s
Development Report—1993—reports that eliminating indoor smoke could cut
childhood pneumonia by half and reduce the burden of other diseases by 5%. It has
been estimated that at present more than 15 million hectares of forest are lost per
year in developing countries mainly due to consumption of firewood. According to
UN Food and Agricultural Organization, some 2400 million people are expected to
face acute fuelwood shortage by the end of century with serious nutritional and
health consequences. So we need to move to renewable sources of energy in which
solar energy is the most promising one. Thus, in principle, solar energy could
supply all present and future energy needs of the world on a continuing basis. Also
in India, energy subsidies are provided for petroleum products including kerosene,
diesel, and LPG as well as for electricity. In 2010–2011, this accounted to more
than `25,000 crores in total LPG subsidies (IISD 2012). So, this huge amount of
money can be utilized to develop and improve methods to harness solar energy, i.e.,
solar cell, solar cooker, solar drier.
1.1 History
Food processing times back to the early age when the crude processing containing
different types of cooking, such as over biomass firing, smoking, baking and
Solar Food Processing and Cooking Methodologies 253

steaming, fermenting, solar drying, solar cooking and preserving with some salts
was in practice. Food preserved in this manner was a mutual part of ‘soldiers’and
‘sailors’diets. These crude processing methods were continued to be the same until
the initiation of the industrial revolution [1]. In 1809, Nicolas Appert had developed
a vacuum bottling practice by using heat energy for supplying food to the troops in
the French army, which was ultimately led to sacking in tins by Peter Durand in
1810. He developed the theory of food preservation in airtight jars and containers
by applying sufficient heat energy, and by this, food would last longer safe from
bacterial spoilage. In 1864, Louis Pasteur discovered pasteurization which
improved the quality of preserved food. In the nineteenth century, food processing
technologies were developed on a large scale to fulfill military needs [2]. Later on,
in the twentieth century, the major changes in food habits (eating and cooking both)
and the quality awareness of the humans toward the development of food pro-
cessing have been observed [3]. Apart from this, at present, the trends of cooking
and the demand of food have quite changed. Now, ready-to-eat foods are available
across the globe with a possibility of cooking/baking or roasting, at almost all
locations [2–4]. Some common techniques of food preservation are shown in Fig. 1.
In technical aspect, heating is a common and reliable practice for food treatment.
Thermal proces sing of foods, such as heating, pasteurizing or boiling, drying, baking
or roasting, frying and grilling, affects the quality of the food (nutritional values).
Thermal processing can be done by both conventional methodology and modern
techniques for a quality food [5]. During heating of food (based on Millard reaction),
all bacteria, inactive enzymes, and microorganisms are died, while the vitamins,
flavors, colorants, and quantity are less affected [6]. In the present modern techniques
Food Preservation Method
Inhibition Inactivation Avoid Recontamination
Low temperature storage
Reduction of water activity
Decrease of O2
Increase of CO2
Acidification & Fermentation
Control of pH
Freezing & drying
Concentration
Adding preservatives
Adding antioxidants
Chemical modifications
Phase transition
Gas removal
Sterilization
Pasteurization
Irradiation
Electrifying
Cooking
Frying & baking
Extrusion
Light
Sound
Magnetic field
Packaging
Hygienic processing
Aseptic processing
Hygienic storage
Hazard analysis &
critical point
ISO 9000
TQM
Risk Analysis
Management
Fig. 1 Major food preservation techniques [5]
254 A. Saxena et al.

or food processing methods, there is no risk of toxicity, bacterial or allergic reactions.
Heating also improves palatability, microbiological safety, and shelf life [7].
1.2 Solar Food Processing
Solar food processing is a developing technology which provides quality foods almost
at negligible or minimum cost. There are a number of drying techniques for various
substance or chemicals [as shown in Table 1]. Solar drying is a common practice for
the drying of vegetables, fruits, or chemicals without losing their useful properties [8].
Different designs of solar dryers are used globally according to the substance. Besides
this, open sun drying is also used for some foods with low moisture such as chili,
pepper, pickle. Forced convection-type solar dryers are comparatively better to open
sun drying for dehydration [9]. In general, solar food processing fetches in two
emergent concepts together to resolve the two major issues of the twenty-first century:
First one is how to produce sufficient energy for global population, and second is how
to meet their demands of feeding and living. Obviously, the reason is population blast
and unequal wealth distribution in different nations [9,10]. Food production per capita
above poverty line is necessary for a sustainable life. But, the problem still prevails in
major portions of the different countries because of lack of education and unem-
ployment [11]. By knowing the easy and a safe way of food preservation and full
utilization of reliable energy sources (such as solar energy), people can sort out this
problem at their end, especially in rural areas.
If one can talk about the effect of heat on microorganisms, then it is notable that
the preserving result of heat dispensation is just because of denaturation of proteins,
which terminates enzyme commotion and enzyme-controlled absorption in
microorganisms. The level of demolition is a first-order reaction, i.e., when food is
heated up to a temperature at which contaminating microorganisms destroy; the
same proportion of microorganism decease in a particular period of heating [5]. The
demolition of microorganisms depends upon the temperature; cells decease more
swiftly at peak temperatures. There are many factors that control the heat resistance
of microorganisms, but common reports of the result of a assumed variables for heat
resistance are not continuously conceivable [13]. Given factors are acknowledged
for significance.
(i) Nature of microorganisms,
(ii) Cultivation conditions during cell evolution or spore development (temper-
ature, age of the culture, and culture mediocre used),
(iii) Improper heat treatment (i.e., pH value of the food, water activity of the food,
composition of the food, and the growing media and cultivation conditions).
Knowledge of the temperature resistance of the different enzymes or microor-
ganisms found in particular food can be used to estimate the temperature conditions
desired for destruction of them. In common practice, the most heat-resilient enzyme
or microorganism in a specified food is generally used as a base of calculating
process conditions. It is supposed that supplementary less heat-resistant species will
also be destroyed [14].
Solar Food Processing and Cooking Methodologies 255

Besides this, if one takes a look in typical mechanism of irradiance, then ionizing
radiation takes the form of gamma rays from isotopes or from X-rays and electrons. It
has already been acceptable in 38 countries to preserve foods by devastation of
microorganisms or reserving of biochemical variations [13,14]. The irradiation
procedure includes exposing foods either prepackaged or in bulk, to a determined
level of ionization heat. The application of solar irradiance [Table 2] to organic
materials has a direct/indirect effect, in which the direct effect is a result of energy
deposition by the irradiance in the object molecule, while the unintended effects
transpire as a significance of sensitive diffusible free extremists fashioned from the
radiolysis of water. Solar irradiance has a very wide scope in food disinfection, shelf
life allowance, refinement, and substance quality improvement. All the details are
thoroughly investigated through a comprehensive review by Wilkinson and Gould
[15] with an importance of solar irradiance. The common benefits of solar irradiance
are as follows:
(i) There is only marginal heating of the substance and thus negligible change to
physical characteristics.
Table 1 Summary of novel and conventional drying techniques for food [12]
Technique Suitability/current
usage
Advantages Disadvantages
Microwave drying and
dielectric drying
High value-added
products
Low temperature, batch
or continuous operation,
good quality
Slow and expensive
Microwave-augmented
freeze drying
High value-added
products
Low temperature, rapid,
good quality
Expensive
Centrifugal fluidized
bed drying
Small particles,
vegetable pieces,
powder
Rapid, easy to control Loss of product integrity,
noisy
Ball drying Small particles,
vegetables pieces
Relatively low
temperature, rapid
continuous
Loss of product integrity,
difficult to control
Ultrasonic drying Liquids Rapid Requires low fat
solutions
Solar open drying Fruit, meat, fish
plant
Simple, low cost Large space required,
slow, labor intensive,
difficult to control
Smoking Meat, fish Added flavors Difficult to control, slow
Convection drying Low value-added
products
Continuous Difficult to control
Drum drying Liquids, gelatin Continuous Modification of liquid
Freeze drying Value-added
products
Continuous, no
restriction particle size,
low temperature
Slow, expensive
Fluidized bed drying Small uniform
particles, small
vegetables
Usually batch operation,
uniform drying, rapid
Restriction on particle
size
Osmotic drying Sugar infused fruit High quality Two-step process
256 A. Saxena et al.

(ii) Packed and freezing foods may be treated.
(iii) Fresh foodstuffs may be conserved in a single process and without using
chemical preservers.
(iv) Energy demand is very low.
(v) Variations in nutritive value of foodstuffs are comparable with other
approaches of food conservation.
(vi) Processing is habitually organized and has low functioning costs.
1.2.1 Concepts of Thermal Processing
Concepts of thermal processing clearly show that the traditional thermal food pro-
cessing depends on certain old ideas and keys, which are employed well, while
current food study has raised some queries in contradiction to those perceptions. The
traditional theory of the Dvalue and of the zvalue is illustrated in Fig. 2a, b. To
define a Dvalue of a specific strain of microorganisms, illustrations of these
microorganisms are bare to a higher temperature for a figure of time steps. The
Table 2 Applications of food irradiation [15]
Application Dose
range
(kg)
Examples of
foods
Countries with commercial processing
Sterilization 7–10 Herbs, spices Belgium, Canada, Croatia, Denmark,
Finland, Israel, Korea, Mexico, South
Africa, USA, Vietnam
Up to
50
Long-term
ambient storage
of meat
None
Sterilization of
packaging
materials
10–25 Wine corks Hungary
Destruction of
pathogens
2.5–
10
Spices, frozen
poultry, meat,
shrimps
Belgium, Canada, Croatia, USA,
Denmark, Finland, Israel, Korea,
Mexico, South Africa, Vietnam
Control of molds 2–5 Extended storage
of fresh fruit
China, South Africa, USA
Extension of chill
life from 5 days to
1 month
2–5 Soft fruit, fresh
fish, and meat at
0–4°C
China, France, South Africa, USA, the
Netherlands
Inactivation of
parasites
0.1–6 Pork –
Disinfection 0.1–2 Fruit, grain,
flour, cocoa
beans, dry foods
Argentina, Brazil, Chile, China
Inhibition of
sprouting
0.1–2 Potatoes, garlic,
onions
Algeria, Bangladesh, China, Cuba
Solar Food Processing and Cooking Methodologies 257

1000
10000
100000
0 1 2 3 4 5 6 7 8 9 10 11 12 13
Microbial population
Time (min)
10
100
1000
116 119 122 125 128 131 134
Decimal reduction time (s)
Temperature (°C)
z
D
(a)
(b)
Fig. 2 a Microbial survivor curve on semi-logarithmic coordinates (D value) [10], bA plot of
logarithm of D versus temperature used to determine the thermal resistance constant (z) [10]
residual amount of microorganisms is plotted on a log-scale versus treatment phase,
and the data points bring into line linearly. The Dvalue can be defined as the time
required for reducing the sum of microorganisms at that particular temperature by
one log cycle. The zvalue defines the necessity of the Dvalue on a fixed temperature
[16]. These standards are usually used to define the heat inactivation of bacteria.
Yet, all thermal falling-off reactions, including the obliteration of heat-sensitive
food constituents, follow these laws. Figure 2b shows a mutual concept of thermal
food processing, i.e., a high-temperature short-time treatment (HTST). Besides this,
as per the ‘D’and ‘z’values, various time–temperature configurations can be
established, which are really adequate to attain the same consequence of
pasteurization.
258 A. Saxena et al.

1.2.2 Effect of Heat on Nutritional and Sensory Characteristics
The obliteration of various vitamins, aroma amalgams, and stains by heat follows a
similar first-order reaction to microbial demolition. Commonly, both the values are
greater than those of microorganisms and enzymes. As an outcome, nourishing and
sensory properties are improved and retained by the usage of high heat (tempera-
ture) and short span of time during heat treating [17]. It is thus conceivable to select
specific time–temperature permutations from a thermal death time curve (all of
which attain the same degree of enzyme or bacterial demolition), to optimize a
method for nutrient preservation of desired sensory potentials. This conception
forms the basis of specific rapid blanching, high temperature, short-time pasteur-
ization, high heat sterilization, extrusion, etc. [18].
Heat treatment is an important method, generally used in food processing, due to
the desired belongings on eating quality (different eatables are consumed in cooking
processes such as baking yield flavors which cannot be produced by other method),
but due to a preserving effect on diets by the annihilation of enzymes, microor-
ganisms, pests, and organisms. Some other main advantages of heat treatment of
foods are as follows [16]:
(i) Relatively a simple mechanism of dispensation conditions,
(ii) Competence to develop shelf-stable foods which do not need freezing,
(iii) Obliteration of anti-nutritional issues (e.g., trypsin inhibitor in some pulses),
(iv) Improvement in the obtainability of certain nutrients (e.g., better digestibility
of proteins, gelatinization of starches).
Besides this, the some common nutritious benefits of thermal treatment of food
are [10]:
(i) Removal of harmful constituents (bacterial contamination, venom, enzyme
inhibitors, or allergens protection of food);
(ii) Modifications in food environment erection and texture (advancement in
digestion, improved bioavailability);
(iii) Generation of valuable new combinations (smell, antioxidants, etc.).
1.3 Cooking Scenarios in Different Countries
Cooking is a primary need, or it is a major activity of every household and commercial
places (such as hotels, hostels, hospitals, restaurants, small roadside shops) and in
some common transportation models such as trains and airplanes. It is also notable that
nowadays, ready-to-eat meal (light and heavy stuffed food) is available in the market,
which is usually carried by various persons to their working places, and through a
heating process, this will be ready within few minutes for eating. This is the actual
practice for eating and selling of different kinds offood, across the globe [4,19]. Also
in some countries like, India, Pakistan, Nepal, Bangladesh, Bhutan etc., where some
religious trends such as celebrations of festivals (Diwali, Holi, Eid, Lohri, X-Mas,
etc.), marriages, other functions/parties or even a funeral gathering, when food is
Solar Food Processing and Cooking Methodologies 259

Fig. 3 Energy consumption of different households for some different countries [19]
cooked and served to all gathered people [20]. The food in these activities is generally
cooked in open or closed places (like an open field or ground and a banquet hall) for a
long time through various cooking fuels such as LPG, firewood, or coal.
In this section, the efforts have been made to highlight the present scenario of
cooking foods with their methodologies and obviously the fuel used for cooking in
different countries or region.
In emerging countries, at present around 2.6 billion people rely on biomass in
rural areas to meet their daily energy needs for cooking or heating [19]. Figure 3
shows the energy consumption for different household activities in which energy
consumption for cooking is much higher than other activities, across the globe.
Apart from this, it is also notable that these resources account for more than 90% of
household energy consumption in many countries. If the problem remain same, i.e.,
lack of certain new policies, then the number of people depending on biomass will
rapidly increase to over 2.7 billion by 2030 due to unstoppable population growth.
Statistics shows clearly that one-third population of this world will still be
depending on these conventional fuels [21].
There are few corresponding methods which can improve this condition [19–21]:
(i) Encouragement of more effective and sustainable use of conventional bio-
mass (fuel) as well as encouraging people for switching to updated cooking
fuels and skills.
(ii) Dynamic and rigorous government plan and action is required to accomplish
this target, organized with improved funding from both the public and private
sectors/sources.
(iii) Strategies to encourage, more efficient cleaner fuels and technologies for
cooking necessity to report barriers to access, adoptability or affordability
and supply chain, and to formulate a dominant module of larger development
policy.
Lack of new policies for the development of cleaner fuels and new technologies
of cooking is the major components in consumption of conventional fuels, while
another major issue is world’s population blast and continuously increasing daily
higher energy demands for cooking and heating across the globe. The government
of different countries (or state-wise) should develop new policies for cleaner fuels
such as LPG, electricity.
260 A. Saxena et al.

1.3.1 Household Cooking Patterns, Fuel Switching, and Policies
Commonly, there are three types of household in every country that are categorized
according to particular household income, viz higher income household (HIH),
medium income household (MIH), and lower income household (LIH), and they
can also be categorized as rural or urban households in some developing countries.
Each household has their own choice of fuel for cooking and heating according to
their need and affordability [22]. According to the energy ladder [23], LIHs gen-
erally use the wood (including wood chips, straw, shrubs, grasses, and bark),
charcoal, agricultural residues, and dung, while MIHs use wood, residues, dung,
kerosene, and biogas and lastly HIHs use wood, kerosene, biogas, LPG, natural gas,
electricity, and coal for cooking in developing countries [24].
Available literature and reports by World bank, IEA (International Energy
Agency), WHO, and energy outlooks show that households normally use a com-
bination of different fuels for cooking and heating (see Table 3for example) which
can be characterized as traditional (such as dung cakes, crop residues, and fuel-
wood), transitional (such as charcoal, lignite, and kerosene), or modern (such as
LPG, biogas), while electricity is used for small appliances for cooking and heating
but mainly for lighting. The share of population relying on the traditional biomass
for cooking in 2012 was: 67% for Africa, 80% for sub-Saharan Africa, 51% for
developing Asia, 15% for Latin America, and 4% for Middle East. Table 4shows
the traditional biomass consumption for cooking in different countries [26,27].
The excessive dependence on solid fuels for cooking is an indicator of energy
deficiency. It is familiar that access to modern energy facilities (clean fuels such as
electricity) is important to the success of Millennium Development Goals. The
burden on women and children for collecting fuelwood (wood pellets) can be
reduced by applying the modern energy services (MES). By this, not only the time
will save, but also one can be educated or get some other employment opportunities.
There will also be a notable effect on child mortality [28]. It is also well known that
traditional biomass fuels generate a bundle of pollution. These harmful pollutants
have a poor effect on our health and sometimes become a major cause of death [29].
Jain [30] had discussed the energy security issues for all types of households by
focusing on clean energy fuels for cooking in India. It was mentioned that the clean
energy fuels (LPG, electricity, and kerosene) must be affordable for LIHs for
cooking and heating and the policies should be revised for the same.
Pandey and Chaubal [31] had developed a logit model for rural household (India)
fuel choices for cooking by using database of around 403, 207 observations. Authors
focused on some major indicators such as females and children’s education, regular
income of the particular household, and possession of ration card (BPL—below
poverty line type, especially). It was concluded that clean fuel such as kerosene should
be provided in sufficient quantity for cooking and lighting. Akpalu et al. [32] had
discussed that the almost all energy policies in Ghana or other developing countries
are focused primarily on industrial energy consumption instead of household energy
use. The socioeconomic factors such as household income and fuel switching cost
were considered. It was concluded that a good subsidy on LPG and kerosene is a better
and effective option to a LIH and MIH for fuel switching option. It was noticed that
LPG is primarily chosen for cooking in Ghana’s households.
Solar Food Processing and Cooking Methodologies 261

Wickramasinghe [33] had carried out a research project in Sri Lanka to extend
the appreciative of human aspect of energy access. A questionnaire was prepared to
survey around 2269 households for gathering a data on socioeconomic situations
and matters influencing a transition toward clean cooking services. The results of
the present study show that to develop a transition (switching of fuels), two domains
must be addressed: risk capability and livelihood (Fig. 4).
The results have also shown that the transition is hampered by the following
aspects:
(i) Lack of motivation and financing;
(ii) Burden for switching over to cleaner fuels;
(iii) Lack of updates of energy technology options and other supports;
(iv) The financial risks (the results also reveal that there is a need for a policy
agenda linking the stakeholders, funding, and standardized technologies).
Foell et al. [34] had discussed the use of biomass fuel by the people of world and
the impacts of biomass burning used for household cooking systems (China). This
chapter focuses on the framework and policy development for clean cooking
accesses, to develop a strategy for suppliers of clean fuels, and to revise the failures
policies to improve the program. Maes and Verbist [35] had reviewed the biomass
cooking literature and discussed the sustainability of domestic cooking pattern in
Table 3 Combination of
cooking fuels in Nigeria
(2015) [25]
Fuels used Population share
(%)
Wood + Kerosene 17.71
Wood + Kerosene + Charcoal 3.21
LPG + Kerosene + Solar 8.21
LPG + Kerosene 1.04
LPG + Electricity 4.27
Kerosene + Electricity + Wood 4.27
LPG + Wood + Charcoal 3.13
LPG + Wood 5.21
Wood + LPG + Kerosene + Charcoal 10.42
Table 4 People using
traditional biomass for
cooking [28]
Region/Country 2009 2015 2030
(Millions)
Africa 657 745 922
Sub-Saharan Africa 653 741 918
Developing Asia 1937 1944 1769
Other developing Asian countries 659 688 709
India 855 863 780
China 423 393 280
Latin America 85 85 79
Total 2679 2774 2770
262 A. Saxena et al.

developing countries and how this can be improved. As a solution to air pollution,
the use of energy ladder and switching of fuels (traditional to cleaner) was discussed
with a result-oriented fashion, in which it was shown that the health damages can be
reduced, and time and money can be saved as well as the green environment. Duan
et al. [36] had focused on same points and discussed that the household fuels are
intensely associated with numerous effects comprising the air quality, health, and a
district environment change. The study reveals the results of first Chinese envi-
ronmental exposure-related human activity patterns survey (CEERHAPS), carried
out among 91,121 households located in 9745 villages and towns. The objective of
the study was to investigate the cooking and heating pattern in China. It was
observed that the LPG and biomass fuels are principal energy fuels for cooking,
used by 45% (approximately) and 32% of households, respectively. Biomass
(47.6%) has been observed as a main fuel for cooking in rural households, while
urban population was more likely to cook with gas (65.8%). A model was devel-
oped to WHO for indoor air pollution (IAP), health effects, and burden of disease.
There are numerous data available on cooking fuel choice and modern stoves
[37–43], fuel switching theory and models [44–51], energy ladder [52–55], IAP
[56–60], respired illness, and burden of disease and death [61–72] in developing
countries. As reference to the above literature, the daily demand of cooking energy
fuels with increasing world’s population is very tough to adopt the clean cooking
fuels by MIHs and LIHs, while the new improvements in cookstoves are intro-
ducing day by day to achieve more efficient performance of cooking systems.
Government of different nations are promoting the clean fuels and providing
various offers (subsidies, special discounts, etc.) on them. According to a report of
the World Bank, different designs/types of cookstoves are used by different
households (here for MIH and LIH) which are commonly associated with particular
fuel types such as a three-stone type for biomass fuel, a traditional clay pot/simple
ceramic liner-type stove for dung cakes or wood pellets, a round cylindrical stove
for charcoal, and gasifier stoves. For a HIH or a rural area population, modern
Fig. 4 Risk capacity and income for switching cleaner cooking fuels and stoves [33]
Solar Food Processing and Cooking Methodologies 263

(i) (ii) (iii)
(iv) (v) (vi)
(vii) (viii) (ix)
(x) (xi) (xii)
Fig. 5 Different designs of modern cooking stoves for clean cooking: imicrowave oven, ii LPG
stove (5 burners), iii electricity induction stove, iv modern coal stove (Angeethi), vmodern
kerosene stove, vi large wood pellets stove (big Chulha), vii modern single burner small family
LPG stove, viii compact wood pellets stove for grilling and roasting, ix solar box cooker, xsolar
dish cooker, xi modern biomass stove, xii solar evacuated type cooker for roasting [139]
264 A. Saxena et al.

cooking stoves (see Fig. 5) are used in developing countries because of using clean
cooking fuels such as LPG (1–5 burner type cooking stove), natural gas, electricity
(a microwave oven, induction stove, or an electric kettle). The conversion efficiency
of these stoves is much better over previous designs of cooking stoves. Apart from
this, in modern era, biogas cookstoves and solar cookers are also getting a good
attention in rural areas of emerging places. It is notable that solar cookers are not
popular in only rural area but some urban households are using them well in both
developing and developed countries because of their simplicity, low maintenance,
no carbon emissions, and obviously performing on free fuel from the sun. Apart
from this, by using of solar cookers one can save the limited fossil fuels and power
energy for a fair amount annually.
2 Solar Drying Technologies
Solar drying is simple and an economic way to preserve the food since nineteenth
century. This treatment removes water or heavy moisture presents in various
ingredients and prevents fermentation. Solar food dryer (SFD) presents a significant
progress upon this primeval method of drying foods. SFD has an initial expense,
but it provides a better taste and a safe nutritious food and their marketability. They
perform a fast and safe drying process more efficiently than other traditional sun
drying methodologies. Solar drying can be categorized into two simple categories:
open sun drying and cabinet solar drying. Solar cabinet dryer produces a
high-quality dried foodstuff more quickly in humid or arid climates. Dried stuffs
contain a high value of vitamin C content [73].
In recent years, several attempts have done across the globe to design or develop
novel solar dryer for various activities such as for agriculture or industrial sector.
The previous research shows that the efforts has been made not only to improve the
efficiency of the SFD but also for cost and design optimization as well as to
improve the year-round performance by making a hybrid SFD. In the next section,
the discussion is made on various types of solar dryers and their performance.
2.1 Types of Solar Dryers
Solar dryer simply utilizes solar radiant energy to heat the air which flows over the
substance placed inside the SFD. Warm or dry air that flows through the system
carries away the moisture contents from the different substances through evapo-
ration. A solar dryer generally consist of a solar air collector or air heater [74], a
drying unit and an air handling unit. The main components of a solar drying are
shown in Fig. 6. It is notable that the efficiency of the SFD majorly depends on the
efficiency of air heater. Classification of the solar dryers is shown in Fig. 7, and
some commonly used solar dryers are discussed in Table 5.
Solar Food Processing and Cooking Methodologies 265

Fig. 6 A solar chimney fruit dryer with a solar air heater (consisting of single or double glazing, a
solar collector, an air blower, ducts for air supply, and sometime a PV module in case of hybrid
solar dryer)
Fig. 7 Classification of solar drying [75]
266 A. Saxena et al.

2.2 Solar Open Drying
Solar drying is an important application of the sun energy. Earlier farmers were
fully dependent on solar energy for drying agriculture crops, herbs, or spices. For
this, a ground or a bed of concrete was prepared to achieve a high temperature range
through solar energy. The ambient temperature and wind velocity support this as
natural convection. Obliviously, the process is much slow; therefore, it generally
took 3–4 days to dry the substance. The initial and operation cost of open sun
drying is almost negligible. Volume wise and despite a very simple process, the
open sun drying is still a most common technique of drying [76]. Table 6shows the
various studies conducted on open sun drying of commonly used crops.
2.3 Solar Cabinet Drying
It is a single- or double-glazed rectangular cabinet (Fig. 8). Solar irradiance directly
incident on the substance, and interior surface is blackened to enhance the heat
Table 5 Types of solar drying
Types Working
Open sun
drying
In this, the substance is spread in the form of a thin layer on the ground.
Solar radiant energy directly incident on the substance, and the moisture
contents removed through the natural convection with low wind velocity. In
this phenomenon, the present substance also absorbed radiation which
results in a high vitamin C value. This drying is still most common drying in
rural areas. The ambient parameters have a major significant effect on open
sun drying
Cabinet solar
dryer
A cabinet solar dryer is a hot box-type dryer in which fruits, herbs, spices,
vegetables, etc., can be dehydrated. It consists of a long rectangular basin, an
insulated base, and a single or doubled glazing. Irradiance passes through
the glazing and absorbed by blackened surface (absorber) and raises the
internal temperature. Small holes are made in the cabinet for providing
ventilation to induce fresh air inside the cabinet
Greenhouse
dryer
It is a low cost, simple in design, and easy to fabricate. It is used across the
globe for crop dehydration. It has a parabolic shape and covered by a
polycarbonate sheet. The base of the dryer is generally a concrete floor. The
substances are placed in a thin layer on the black concrete floor. Solar
irradiance passing through the polycarbonate sheets heats the air and stuffs
inside the dryer, as well as the absorber floor. The heated air, when pass over
the stuffs, absorbs moisture from the stuffs. A direct exposure to irradiance
of the stuffs and the heated air augment the drying rate
Hybrid solar
dryer
A hybrid solar dryer generally performs on two or more fuels for drying.
This is because the said systems become more efficient by operating on two
or more fuels, simultaneously. This system is capable of generating an
adequate and continuous flow of hot air for a higher temperature range.
Likely hybrid dryers used biomass or electricity along with solar energy
Solar Food Processing and Cooking Methodologies 267

Table 6 Various studies conducted on open sun drying of commonly used crops
Reference Research work outcome
Anwar and Tiwari
[77]
An attempt had been made to estimate the value of ‘hc’for six
different crops, such as green chillies and green peas under open sun
drying conditions. The value of ‘hc’was varied from crop to crop
because of differences in their properties such as moisture content,
porosity, shape, and size of the crop
Mulokozi and
Svanberg [78]
In the present work, 8 vegetables commonly consumed in the living
areas were traditionally sun-dried and the pro-vitamin ‘A’carotenoid
was counted. It was remarked that the amount of pro-vitamin
A-carotenes in conventionally dried vegetables was much reduced by
open sun drying
Kabasa et al. [79] The present work focused on the availability of vitamins A and C in
vegetables and fruits. These vitamins were found out for a major cause
of blindness for 54% in Uganda. The government of Uganda promotes
solar drying as an economic and reasonable substitute. The effect of 3
drying methods (open sun drying, visqueen-covered solar dryer, and
greenhouse solar drying) was investigated for vitamins A and C
contents in fruits and vegetables
Jain and Tiwari [80] In the present work, open sun drying was carried of green pea and
chillies, white gram, potatoes, cauliflower, and onions to investigate
the thermal behavior of the said vegetables. A mathematical model
was developed to estimate the temperature and moisture removal rate
from species. The value of ‘hc’was estimated for different drying
times with respect to different vegetables under open sun drying, and a
significant variation was found in this with a change of species. The
moisture removal rate for cauliflower and potato slices was
significantly high in comparison with other crops
Akpinar and
Cetinkya [81]
In the present work, drying response of parsley leaves was carried with
forced and natural convection (open sun drying) conditions. It was
observed that no constant drying falling rate was occurred during
performing on both the modes
Prasad et al. [82] The efforts have made to investigate the drying characteristics of
ginger under open sun drying and a hybrid drying system (biomass
based). It was concluded that drying depends upon the product
thickness and ambient conditions of the drying place under open sun
drying. In comparison with open sun drying, the hybrid solar drying
system was found better for drying other stuffs, vegetables, and fruits
Al-Mahasneh et al.
[83]
The open sun drying and forced convection drying have been carried
of sesame hulls at Jordan University of Science and Technology. In
total, six mutual thin-layer drying prototypes were tailored to the
experimental data. The experimental results were compared with
theoretical models, and it was found that open sun drying took place in
nearly 180 min while forced convection drying needed 120–250 min.
Both the drying techniques were found adequate for drying sesame
hulls
Kooli et al. [84] The open sun drying and greenhouse drying of red pepper were carried
out inside a laboratory by using a 1000 W lamp for radiant energy.
The effect of drying was investigated for moisture contents and drying
rate by repeating the experiments under open conditions. It was
(continued)
268 A. Saxena et al.

transfer. For ventilation, small holes are drilled to the bottom surface to induce the
fresh air inside the box. Opening ports are positioned on the top segments of the
sideways and rearmost panels of the cabinet frame. As the box temperature rises,
the hot air passes out of these openings by means of natural convection. In this
process, both the heat and mass transfer take place [89]. The heat is transferred to
the stuff through radiant energy or energy from any other heating source, while the
mass transfer of moisture is from the entire stuff to the surface and then to the
surrounding air. The objective of the cabinet drying is to supply the more heat to the
crop than open sun drying. A cabinet dryer can also be a forced convection or
hybrid SFD, which results in a fast moisture removal rate, less drying time, quality
drying characteristics of the matter, and an economic process. Some novel designs
of cabinet-type solar dryers are shown in Table 7.
Table 6 (continued)
Reference Research work outcome
concluded that experiments carried out in laboratory overestimate the
drying process with respect to time
Tripathy and Kumar
[85]
In the present article, the experiments have been conducted for drying
of potato slices to find out the optimum fast rate drying methodology.
The testing was carried out for open sun drying and mix-mode sun
drying to observe the drying characteristics such as surface color,
texture, and drying rate. It was concluded that the water captivation
ability of done product is partial mostly by the variation in rehydration
temperature tracked by sample geometry
Gudapaty et al. [86] An LPG-based drier has been developed for drying of 50 kg of Indian
gooseberry, and the comparisons were made with open sun drying of
the same. The quality and rehydration characteristics of LPG-based
dried stuff were higher and free from impurities. Beside this, the value
of vitamin C in the dried product was high rather than dried by open
sun technique
Akpinar [87] Drying characteristics of mint leaves were was studied and
investigated in a chimney type solar dryer and under open sun drying.
Energy and exergy analysis was performed for both conditions. It was
concluded that there was no change in dried mint leaves either by open
drying or by solar cabinet drying
Hande et al. [88] In the present work, the study of drying characteristics for open sun
drying of Kokum rind was carried out. The important parameters were
the temperature of crop surface, moisture removal rate, and drying
time. The value of ‘hc’was estimated on the value of constants ‘C’
and ‘n’which were calculated by regression analysis. Some other
important parameters were also considered for study such as acidity,
pH value, non-reducing sugar contents, carbohydrates, protein ash,
calorific value, and color, before and after open sun drying of kokum
rind
Solar Food Processing and Cooking Methodologies 269

Fig. 8 Different designs of solar dryers [95,135,140,141]
Table 7 Research outcome of some novel solar cabinet dryers
Reference Research work outcome
Datta et al. [90] In the present work, a solar cabinet drier has been developed and
transient analysis of the SFD was carried out with some applied
assumptions. The model was feasible to predict the instant
temperatures inside the cabinet, the drying rates, and the moisture
contents. Experiments were conducted for no load and for load
conditions (10–40 kg of drying substance). It was concluded that up to
20 kg/m
2
of wheat can be dried per day
Sharma et al. [91] A SCD was fabricated, and thermal performance was carried out with
help of energy balance equations at New Delhi. The collector
temperature was observed around 85 °C on no load, while around
50 °C was observed for load conditions (20 kg of wheat). The
cauliflower, turnip, and green peas were also dried for a comparison at
small load conditions. It was concluded that the cabinet dryer was
much efficient than a open sun dryer and the product dried in cabinet
dryer was superior in quality
Ampratwuma and
Dorvlo [92]
In the present work, a reverse FPC has been used for air heating for
drying of agriculture stuffs inside a SCD in climatic conditions of
Delhi. Energy balance equations were developed for thermal modeling
of the system. The design optimization of SCD was done for
parametric studies over ambient conditions. It was concluded that new
type SCD was much efficient than conventional SCD
(continued)
270 A. Saxena et al.

Table 7 (continued)
Reference Research work outcome
Goyal and Tiwari
[93]
A prototype SCD was fabricated and tested at no load as a solar
air-heating system. The system was operated for 28 days of May 1996
in Oman. During the testing, the SCD achieved a temperature around
81.3 °C. The system was observed for temperature variations inside
SCD during the duration of 28 days, but no significance difference was
observed in inside temperature of SCD during 10:00–15:00 h. The rate
of solar radiant energy absorbed by SCD was approximately 0.90 kW
sq/m
Adapa et al. [94] An SCD integrated with a dehumidifier loop was designed and
fabricated to study the drying characteristics of a highly moisture
content (70%) alfalfa. The stuff was spread on the trays inside the SCD
and operated for 10% of moisture content alfalfa. The system was
operated on the forced convection for a temperature range of 25–
45 °C. The drying time for alfalfa chops was observed from 4 to 5 h.
The explicit moisture removal rate was observed from 0.35–1.02 kg/
kWh
Srikumar et al. [95] A new type of SCD has been developed and tested for drying fruits
and vegetables. In this design, the stuff was placed beneath the
absorber to avoid the problem of discoloration due to irradiance. Two
small fans used for forced convection accelerate the drying rate. The
system was found adequate for solar drying by removing 90% moisture
from the stuff (4 kg) within 6 h. The economic analysis has also been
done, drying cost was found around Rs. 17.52 for 1 kg of bitter gourd,
and the payback was estimated around 3.26 years
Rawat et al. [96] The energy analysis of an economic, simply designed, natural
convection SCD was studied for India. Present work focused on
manufacturing sectors who wish to know energy requirement and to
reduce greenhouse emissions. Grown chillies were taken as drying
object. Energy payback period was estimated for different
conventional fuels. The overall energy input to the system was
estimated around 2744.61 MJ, while the energy payback was found in
the range of 1–2 years (i.e., depended on the drying characteristics of
object)
Signh and Pandey
[97]
In the present work, the drying properties of sweet potato (Ipomoea
batatas L.) were investigated in a SCD. The convective drying has
been carried out under the five different temperatures and the air
velocities for different sample thicknesses of sweet potatoes. Results
shown that the drying of samples took place in the falling rate phase
and the diffusivity was observed to be increased with increasing
temperature. The effective moisture diffusivity of the taken samples
was observed for a range 1.26 × 10
−9
to 8.80 × 10
−9
m
2
/s, while the
activation energy was estimated around 11.38 kJ/mol
Demiray and Tulek
[98]
In the present work, the effect of the drying behavior of garlic slices
has been investigated in a SCD at a constant velocity (2 m/s) and a
temperature range of 55–75 °C. The effective moisture diffusivity of
the taken samples was observed for a range of 2.22 × 10
−10
to
2×10
−10
m
2
/s, while the activation energy was estimated around
30.58 kJ/mol
(continued)
Solar Food Processing and Cooking Methodologies 271

3 Solar Cooking
Food is the prime need of humans. Various types of fuels are used to cook the food
worldwide. Due to limitations of using the fossil fuels for cooking as well as to
reduce the environmental pollution and need of safe cooking, the concept of solar
cooking was generated in 1951. But, the efforts toward solar cooking were suc-
cessfully evaluated in 1767 by H.D. Saussure, a French-Swiss Physicist [101]. After
this, efforts were continued by various pioneers of the field toward the effective solar
cooking in eighteenth century and later. At present, various designs are available for
solar cookers for efficient solar cooking across the globe. These solar cookers are not
only simple in design but economic, accident, and pollution-free cooking, easy to
maintain and feasible to perform round the year even in low ambient conditions.
Indian government programs like Jawaharlal Nehru National Solar mission
(JNNSM) ambitious target to generate 100 GW solar energy by 2022. Also Off-grid
and Decentralized Solar Cooker Program (phase 2, JNNSM) promotes off-grid
cooking application such as cooking/baking/frying using solar device with central
financial assistance from Ministry of New and Renewable Energy (MNRE).
3.1 Types of Solar Collector and Solar Cookers
Solar collector—a solar-type collector is a flat wooden or metallic box which
generally composed of a transparent glass cover, some glass or metallic tubes
carrying coolant or heat-carrying working fluid, and an insulated back plate. The
working principle is a simple greenhouse effect; whenever solar beams incident
Table 7 (continued)
Reference Research work outcome
Sallam et al. [99] In the present work, two similar solar dryers (direct and indirect) were
used for drying the mint by operating it on natural and forced
convection. In the case of forced convection, velocity of the air was
around 4.2 m/s. The effect of flow mode was investigated with the
significant effect on drying kinetics of the object. The results shown
that the drying of mint was occurred in a falling rate period with
different climatic conditions (with no constant rate period of drying).
The drying rate was observed to be high in forced convection
operation. The effective moisture diffusivity of the taken samples was
observed for a range of 1.2 × 10
−11
and 1.33 × 10
−11
m
2
/s
Yahya et al. [100] In the present work, a solar-assisted pump dryer (SAHPD) and a SCD
were investigated for solar drying of cassava chips. The moisture
content of cassava was notified to be reduced from 61 to 10.5% with a
flow rate of 0.125 kg/s. Results shown that drying rate by using
SAHPD was quite higher than SCD. Thermal efficiencies were notified
as 25.6% for SCD and 30.9% for SAHPD with an average solar
fraction as 66.7% for SCD and 44.6 for SAHPD
272 A. Saxena et al.

upon the glazing, the direct radiation strikes on the blackened surface of solar
collector through passing the transparent cover and the heat energy is trapped by the
collector. There are mainly two types of solar collector, i.e., flat plate collector and
concentrating collector. Concentrating collector can further be classified as:
(a) Flat plate collector with plane reflectors;
(b) Compound parabolic collector;
(c) Cylindrical parabolic collector;
(d) Collector with fixed circular concentrator and moving receiver;
(e) Fresnel lens concentrating collector;
(f) Parabolic dish collector.
From the design prospects, solar cookers can generally be categorized into two
types: tracking solar cookers and non-tracking solar cookers (Fig. 9). But, in pre-
sent scenario, the research on solar cooking and standard of solar cookers have
broaden the categories of solar cooker as following.
3.1.1 Tracking Solar Cookers
It is a solar cooker which consists of a parabolic dish (combination of small
reflectors), a pressure cooker, a continuous tracking mechanism, and a rigid stand
for holding both the elements. The sun beams incident on the cooker directly, and
reflectors reflect the energy to the cooking vessel placed at focal point. The said
cooker requires a continuous movement to follow the sun (each 10 or 15 min) and
to retain the focus image on the object. These types of cookers give the highest
cooking efficiency (Fig. 5i).
Fig. 9 Types of solar cookers
Solar Food Processing and Cooking Methodologies 273

3.1.2 Non-tracking Solar Cookers
It is a simple box-type solar cooker which consists of a rectangular or square
well-insulated blackened box, 2–4 cooking utensils, and single or double glazing
with a reflector mirror booster. The stuff is placed inside the cooking vessel, and the
glazed cover is then easily closed. The sunlight directly falls on the blackened
surface (aperture area), on the top surface of vessel, and on the mirror booster. In
this manner, conduction and convection take place inside the cooker through the
solar radiant energy and the stuff get cooked. These cookers are used on a large
scale around the world because of less time taken in quality cooking (Fig. 5j).
3.1.3 Indirect-Type Solar Cookers
These cookers are quite different in design and use. In these types of solar cooker,
obviously the heat source is solar radiant energy but it is utilized indirectly for
cooking purpose. Generally, they consist with a solar collector integrated with heat
pipes, a solar boiler, etc. The food is cooked with the help of steam produced
through the solar boiler inside the cooking chamber. The use of PCM has been
observed effective in these types of cookers. Sometimes, Fresnel lens or additional
mirror boosters can also be used to enhance the thermal performance of the unit
(Fig. 10).
Fig. 10 Schematic diagram of indirect solar cooker [102]
274 A. Saxena et al.

3.1.4 Hybrid Solar Cookers
These types of solar cookers are more efficient in comparison with other solar
cookers because of operating on dual fuel. These cookers are operated on dual
inputs, say solar energy and electricity or solar energy and LPG or any other fuel
along with solar energy. The system decently performs on solar energy, when the
ambient conditions are good, but as they became low or poor, the other fuels initiate
and maintain the cooking speed without any interruption. It results in timely and
safe cooking (Fig. 11). They often provide a fast thermal response of solar cooking.
3.2 Cooking Methodologies and the Use of Solar Cookers
Cooking is a major end-use activity in which we find robust and frequently high
specific energy carrier priorities. The extent and the form of energy carrier used by
an individual family depend on the capability of the household to recompense the
subsequent fuel costs as well as the lifestyle. The cause of this change is simple; i.e.,
low-income families cannot invest in high energy efficiency technology because of
unawareness toward the costs of energy and poor information barriers. Accessibility
and cost of the cooking fuels clearly demonstrate the reason of fuel choice for
cooking and heating. Households that change the cooking fuels for a clean envi-
ronment were much aware, and this also shows their capability toward paying a
higher cost for the replacement (especially shifting to LPG from kerosene). Besides
this, the cooking methodology is adopted by the various households by taking into
account the economical use of food and resource fuel as well as the safety of food.
Following are cookery methods for different households of different countries
(Fig. 12).
Fig. 11 Experimental setup of a hybrid solar cooker [103]
Solar Food Processing and Cooking Methodologies 275

No doubt that a large figure of households instantaneously uses a different
cooking pattern or variety of fuels for cooking, but another considerable factor is the
choice of cooking fuels according to their cost that suits their family budget. If one
can talk about the fuel choice for cooking than in rural households, biomass (wood
pellets, charcoal, dung cakes, dry grass, etc.) is common fuel for these activities. On
the other hand, LPG and kerosene are used for the same purposes in urban
households. Besides this, clean energy fuels such as electricity and solar energy are
also used for cooking at different locations of the various countries in the present
era.
However, it is difficult to measure the exact involvement of solar energy in
cooking or heating activities in developed or developing countries, but people from
different countries are aware about this source of free energy. Countries such as
China, India, Turkey, South Africa are paying attention toward solar energy
applications and continue for promoting it by launching new schemes and by
providing attractive financial aids. People from these countries are using solar
cookers along with LPG and electricity in urban areas while along with kerosene
and biogas in rural areas. Still that biomass fuel is used by some rural households
for cooking and heating. Both the households (rural and urban) have a different
pattern for cooking and use the cooking fuels accordingly. Both the households use
solar cookers for cooking pulses and rice, to boil eggs and potatoes, and other light
meals or the meals which require less time for cooking. It is also notable that the use
of solar cookers is not limited to rural or urban households in different countries but
they are also used in hospitals, institutes, hotels, hostels, and many other places
where the sunshine is available in plenty [104–108].
Generally, rural households start their routine life early in the morning with
preparing breakfast. At this time, solar radiant heat is not available in appropriate
amount. During the solar noon (from 11:00 AM to 15:00 PM), one dish for the
lunch and one dish for dinner (such as pulses or rice) are prepared by solar cooking.
Cooking Methods
Dry heat cookery methods Moist heat cookery methods
Boiling
Stewing
Frying-
Barbequing
Basting
Baking
Steaming
Grilling
Roasting Shallow frying
Fig. 12 Cooking methodologies across the globe
276 A. Saxena et al.

For this, a dish cooker, a box cooker, or an especially designed solar cooking unit
can be used. A solar dish cooker is more efficient than a box cooker to cook the stuff
which requires high temperature (potatoes, eggs, meat). On the other hand, box
cooker is used for pasteurization of milk or water, for cooking rice or pulse, etc.
Other cooking materials are prepared by biomass or kerosene (such as chapatis,
some dry vegetables, or other stuff required hard boiling or deep frying).
Table 8shows the cooking schedule of five different families in which three
from rural area (families A, B, and C) ‘Naya-Gaon’and two from the town (families
D and E) in Moradabad district. This table demonstrates the time of cooking and
use of solar cooker by particular family. It is also clear from Table 8that the people
from rural and urban areas use the solar cooker only for cooking two dishes, i.e.,
one for the lunch and one for dinner.
3.3 Energy Savings Through Solar Cooking
Estimation of energy savings through the use of solar cookers is a simple exercise in
which the amount of fuel saved per year by solar cooking is calculated. These
savings depend on the efficiency of solar cooker, design parameters of cooker,
ambient parameters during solar cooking as well as the nature of substance to be
cooked inside the cooker. For this exercise, a survey-based research is necessary by
considering some basic assumptions with the effective cooking time. Let us assume
that a simple household of 5 family members uses an electric oven (1200 W) for
Table 8 Cooking schedule of different households in Moradabad [109]
Family Time of cooking Cooking by solar cooker
A (05
members)
Breakfast (7:30–8:00 h), lunch
*2
(12:30–14:00 h), dinner
*2
(19:00–
20:15 h)
lunch
*2
(10:00–13:00 h) and (13:15 h–
up to the finishing of one dish for
dinner)
B (07
members)
Breakfast (7:30–8:15 h), lunch
*2
(12:30–14:15 h), dinner
*2
(19:00–
20:15 h)
lunch
*2
(10:00–12:45 h) and (13:00 h–
up to the finishing of one dish for
dinner)
C(07
members)
Breakfast (7:30–8:15 h), lunch
*2
(12:30–14:15 h), dinner
*2
(19:00–
20:15 h)
lunch
*2
(10:15–12:45 h) and (13:10 h–
up to the finishing of one dish for
dinner)
D (06
members)
Breakfast (7:30–8:00 h), lunch
*2
(12:30–14:00 h), dinner
*2
(19:00–
20:15 h)
lunch
*2
(10:00–12:30 h) and (13:00 h–
up to the finishing of one dish for
dinner)
E (08
members)
Breakfast (7:30–8:25 h), lunch
*2
(12:30–14:15 h), dinner
*2
(19:00–
20:15 h)
lunch
*2
(10:15–13:15 h) and (13:30 h–
up to the finishing of one dish for
dinner)
*shows the number of dishes to be cooked for both lunch and dinner
Solar Food Processing and Cooking Methodologies 277

cooking, then what would be the amount of electricity consumed for cooking? This
can be simply estimated by knowing the cooking pattern of the same household.
Assumptions are as follows:
1. For a single dish, the amount of electricity is consumed 0.25 kW.
2. For a single dish, the amount of LPG is consumed 0.20 L.
3. A single dish means 600 g of vegetables or cooking substance (not non-veg).
4. Solar cooking is performed during the sunshine hours.
Now, for the estimation of electricity consumption by considering the cooking
pattern of the said household:
Electricity consumed for cooking breakfast, the lunch, and dinner by
oven = 1 kW,
Electricity consumed for cooking the light snacks by oven = 0.25 kW.
Electricity consumed on ideal conditions by oven = 0.10 kW.
Total electricity consumed for cooking by oven = 1 kW + 0.25 kW +
0.10 kW = 1.35 kW.
If the electricity connection is through the hydel board of electricity, then the
cost of total electricity consumed is (by `4.40/unit) around `6.00. It means that the
monthly bill is around `180 for cooking on electricity.
Similarly in the case of LPG, the estimation of LPG consumption by considering
the cooking pattern of the said household is:
LPG consumed for cooking breakfast, lunch, and dinner by LPG
stove = 0.50 L.
LPG consumed for cooking the light snacks by stove = 0.10 L.
Total LPG consumed for cooking by stove = 0.50 ltr + 0.10 ltr = 0.60 L.
If the LPG connection is through the authorized gas agency by government, then
the cost of total LPG consumed is (by `32.50/unit) around `19.50/-. It means that
the monthly bill of LPG is around `604.50/- for cooking.
From Table 8, it is shown that a solar cooker is feasible to cook the two dishes
per day, i.e., one for lunch and one for the dinner. Now, one can accept that the
electricity consumption for cooking -two dishes is 0.50 kW (from the assumptions)
and the price for this amount is `2.20/day which can be `66.00/month or `742.00/
year. Similarly, for the LPG the saving amount will be `13.00/day and this will
around `390/month or `4680/year. But these savings are not the actual because it
includes the PBP of the cooker. If one has to estimate the net savings of fuels or the
amount which is spent to buy the cooking fuels, then the PBP of the cooker has to
also be estimated and subtracted from this savings amount.
The PBP of the cooker can be calculated by considering some economic factors
as follows [110]:
N=
Log E−MðÞ
x−yðÞ
hi
−Log E−MðÞ
x−yðÞ
−Z
hi
Log 1+xðÞ
1+yðÞ
hi
278 A. Saxena et al.