Current World Environment

Introduction

Approximately 27 million rural population rely on biomass for cooking.¹ Fuelwood, Liquid Petroleum Gas (LPG) and biomass wastes are being used for community cooking. Traditional fuels being used, release hazardous smoke. Use of traditional inefficient biomass burning cookstove causes poor air quality, affecting human health, deteriorating forest eco system, global warming and climate change. According to WHO, 1.5 million people die annually worldwide due to indoor air pollution.^2-9

Renewable energy share is 12% of a total 200 GW of electricity produced in India. Due to rise in population, economic development, and changing lifestyles electricity requirement in India has been increasing despite of continuous rise in capacity.

India receives solar radiations ranging 3.0–6.5 kWhm^-2 per day.¹⁰ Solar radiations can be utilized for cooking, heating, lighting and other applications. With the technology advancement and economical viability the SPV, SWH, solar desalination, solar drying and steam cooking system are popular practical applications of solar energy. Solar steam cooking (SSC) system is solar energy based technology used to cook food for large number of persons. In solar steam cooking system, the solar radiation falls on a solar concentrator, water become steam at high T&P, which is taken to the kitchen using insulated pipes.^11-14 The solar concentrators being propagated in the country are single axis TFFS dish and dual axis TFP (ARUN© Dish).^(15,16)

A solar cooking system of community size consists of number of automatically TPRs (Scheffler dish), assembled in series and parallel combinations to generate steam for cooking food for thousands of people twice a day without polluting environment with in short period of time.

In SSC, temperature of 350-400⁰C is generally achieved. A 7m² sized solar dish can cook the food for 50 people and large sized dish (16m²) can prepare meal for more than 50–100 person.¹⁷ Traditional food such as chapattis, boiling or frying rice, vegetables, cereal, pulses, regional dishes etc. can be prepared. The JNNSM aimed to support solar based heating system that has set the ambitious target for domestic and industrial applications. The MNRE will install 20 million m² of collector/reflector area during phase III (2017-2022) under the mission.¹⁸ Scheffler type dish is used as concentrator for cooking.^19-21 Because of simple design, the industrial & maintenance expenditure of a Scheffler dish is cheaper than the other concentrators.^15,22-23

Components of Solar Steam Cooking System

Figure1: The various components of solar steam cooking system are presented in this section. Click here to View Figure

Design and Dimensions of Solar Steam Cooking System

The design specifications of various components of SSC have been presented in this section.

Scheffler Dish

Wolfgang Scheffler initially developed Scheffler reflector in 1986 which is a parabolic dish in which single axis tracking is provided to move along with sun. Scheffler reflector has a fixed focal point, which makes cooking easily and temperatures, rises to 450° - 650°C. The Scheffler reflector system installed at Scheffler reflector system installed at Prajapita Brahma Kumaris Ishwariya Vishwa Vidhyalaya, Om Shanti Bhawan, Madhuban, Mount Abu Rajasthan, India in 1999 has capacity to cook food for 35,000 persons daily was a largest in the world. The Scheffler dish concentrates solar beam at concentration ratio of 100 at absorber to get steam.²⁵

Dimensions

Diameter: 1 m

Reflector Material: Acrylic

Steam pressure: 10 bar

Steam temperature: 180⁰C

Absorber

The absorber is used to receive the concentrated solar radiation to convert water into steam.²⁶

(a) Specifications

Capacity: 2 kg

Material: Aluminum

(b) Design Calculation:

Steam jacketed utensils

Initial temperature of rice, T₁: 20⁰C

Final temperature of rice, T₂: 100⁰C

Steam Jacketed Utensils

The steam from absorber is carried to kitchen using insulated pipe ²⁷.

(a) Specifications

Capacity: 2 kg

Material: Steel

(b) Energy Required in Solar Collector Energy for Cooking Rice:

M₁: 2Kg
Dp: 1.8 KJ(Kg ^oC) ^-1

Estimation of the useful energy required for cooking has been reported by.^28-31

Energy Requirement for Water Boiling

M₂: 2 Kg

Specific heat of Water: 4.187 KJ(Kg ^oC) ^-1

Water temperature initially, T₁: 20 ^oC

Final temperature of water, T₂: 100 ^oC

Energy Required for Cooking Pot

M₃: 2 Kg

Specific heat capacity of Stainless steel: 0.510 KJ(Kg ^oC) ^-1

Initial temperature, T₁: 20 ^oC

Final temperature, T₂: 100 ^o C

Energy for Water Vaporization

Mass of water (M₄₎: 2 Kg

hfg = 2260 KJKg^-1

Total Energy

The one-third of the required energy for cooking get lost

Loss

Total Energy Required for Cooking 2 Kg of Rice

Collector Area

Energy for cooking rice (2kg) = 7.5 MJ

Hourly GSR = 1.583MJm^-2

Cooking time

Time required = 7.5/ 1.583 = 4.74 hours.
Collector area = 6 m²
Cooking time with 6 m² = 7.5/ (6 × 1.583) = 0.79 hours

Installation of Solar Cooking System

Due to high temperature achieved in the system, the cooking time has reduced by 45 minutes than conventional solar cookers.³² The suitability of solar steam cooking in institute’s kitchen with SR was found by More.³³ Four dishes of 16 m² SR were used to cook food for 500 persons daily by generating steam of 230 kgd^-1 resulted in saving of 19 kg of LPG/day. A SSC system was installed at automobile department, Nehru College of Engineering and Research Centre, Kerala. The maximum water temperature at the outlet was 140.2⁰ C by using aluminum sheet reflector. GI sheet is not better option to cook food.³⁴

A SSC system was installed at Sai Baba Shridi, Ahmednagar, Maharashtra for cooking 20,000 people per day during 2009. The system is generating 3,500 kg of steam daily, which resulted in saving of 100,000 kg of cooking gas.³⁵ The system cost was about Rs 133 lakh out of which 43% was paid by the government. TTD, Andhra Pradesh has set up a SSC system for preparing meal for 15,000 persons daily. The system generates around 4,000 kg of steam d^-1 at 180⁰C and ten kgcm^-2 that sufficient to prepare food two time for nearly15,000 devotees. It was modular and consisted of 106 automatic TPC arranged in series & parallel combination, each of 9.2 m² reflector area. The all concentrators were attached to a central steam piping connected to the kitchen. The system helped in saving of 1,18,000 liters of diesel annually amounting Rs. 0.23 million. The system cost was about Rs. 11crore with 5.5 crore paid by MNRE, rest was paid by the TTD trust.³⁶ A SSC system was installed at Golden Temple, Amritsar in 2017 for cooking food for 50,000 persons costing Rs. 17.25 million, which significantly reduced daily consumption of 600 LPG cylinders and 30,000 kg of firewood.³⁷

A solar steam cooking system was installed at Shantivan Complex, Gyan Sarovar Complex and Madhuban campuses; Mount Abu in 1988 in collaboration with Switzerland based Wolfgang Scheffler, along with Brahma Kumaris World Spiritual University (BKWSU’s) for catering meal for 35,000 persons.³⁸ The roof consisted of 84 parabolic concentrators of 96m² size. The temperature reached to 500ºC at its focal point. It generates 3500 Kg of steam daily and cooking time for 50 kg of rice was 12-14 minutes. It saveda bout 200 liters of diesel, 1.2 tons of CO₂ daily and saved 184 kg of LPG every day (ENVIS Center on Human Settlement’s Hosted by School of Planning and Architecture, Delhi). Sarkari Kumar Chhatralay, Vyra has installed the Parabolic Dishes based Concentrated Solar Cooking System consisted of 4 concentrators of 16 m² each of collector area. The system was commissioned in 2011 costing Rs. 8 Lakh out of which Gujarat State Tribal Development Residential Educational Institutions Society (GSTDREIS) has granted Rs. 5.6 Lakh & MNRE granted of Rs. 2.4 Lakh as subsidy. The system is cooking 20 kg of rice, 10 kg of Dal and 10 kg of vegetables daily resulted in saving 120 of LPG/year. The Uttrakhand Renewable Energy Development Agency, Department of Renewable Energy GOI, Uttrakhand has installed solar steam cooking system at various locations which has been summarized in Table 1.

Table 1: Details of Solar Steam Cooking Systems installed/being installed in Uttarakhand³⁹

Discussion

The study revealed that solar steam cooking system can be installed at community level for energy conservation in various institutions. It will help in reduction of CO₂ for mitigating climate change also. It reduces the consumption of LPG thus saving the fuel bill of the institutions. It will also reduce the cooking time and labour for cleaning of utensils as the washing of utensils is done using steam only. On the basis of successful functioning of solar steam cooking system at various locations, this university intends to install the similar system for 1500 students under a common mess for boys and girls.

Conclusions

It is evident from the above discussion that solar steam cooking system is suitable for cooking food for 50 to 50,000 persons thus, reducing the consumption of conventional fuels. It can also be used for water heating also. It will also reduce the cooking time without detouring indoor air quality. It will result in reducing the emission of greenhouse gases and mitigating the climate change. The number of LPG cylinder saved can be utilized for providing LPG to low income group families.

List of Acronym

Acknowledgement

The facilities provided by department of Environmental Science, Dr Y S Parmar University of Horticulture & Forestry, Nauni are highly acknowledged.

Conflict of Interest

There is no conflict of interest of this paper.

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