solar energy for india -status, potential and...

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Journal of Scientific & Industrial Research

Vol . 62, January-February 2003, pp 25-45

Solar Energy for India - Status, Potential and Impact

C L Gupta*

Applied Sciences, Solar Energy Unit, Sri Aurobindo Ashram, Pondicherry 605002, India, solagni@a lle.org.in

and A Ramachandran

National Institute of Advanced Studies, Indian Institute of Science Campus, Bangalore 5600 1 2, India susi lar@ hotmai l .com

It reviews the development of solar energy science and technology in India during last 40 y to a stage where India has one of the l argest R&D and solar technology application program in the world touching every nook and corner of the country. Solar water heaters, box type cookers and home l ighting systems using solar PV have become widely available at reasonable costs appropriate to them. Original lacunae of top down planning without participatory decision making of users, subsidy driven programs, lack of monitoring and preventive maintenance and non-application of the solar energy with a view to resource augmentation and equity, are now in the process of being eliminated. Emergence of considerations of pol lution free clean development, global climate change and stress on creation of l ivelihoods vis-a-vis satisfaction of basic needs and requirements of quality in open marketing system rather than hands on indigenisation are the current stream in ful l force. The real solution wil l be somewhere in the middle for developing countries, where efficiency per unit cost of devices and systems and least capital cost of creating sustainable l ivelihoods wil l define the site specitic recipes most effective to each situation. This has yet to happen. A technological shift has been from dreams of complete energy autonomy to hybridization and partial autonomy because, given the requirements of entrenched l i fe styles in rich countries and aspirations of less developed countries, the former was economically not viable. Passive systems of building for climate tempering and solar PV integrated with buildings are taking shape now and will be the mainstream of immediate future. Also, briefly covered are the path breaking scientific advances of photochemical and microbial production of hydrogen, its storage and use in fuel cel l s which are in their initial stages, but are promising avenues. S ince most of these technologies are proprietary, even at the risk of rei nventing the wheel. India has to strike its own path. Direct solar, biomass based power generation and wind electric generation are i mmediate options; solar PV integrated with buildings along with hydrogen based fuel cells (hydrogen being generated from (wastes/sea water by solar energy) are the solution for the next decade. Considerations of energy equity, security and quality along with non-administered realistic tariffs of oil and electricity provided by conventional means will take care of the economic and ecological options sooner than we expect.

Introduction

India is a l and imbued with sunshine. Annual sunshine hours range between 2000 to 3000 hours for most parts except in parts of the Eastern and Western Ghats . Average dai ly design radiation on horizontal varies between 4.5 to 6.SkWh/m2 per day except in monsoons l . In the electric sector, there is an energy deficit of 1 1 .5 per cent and peak power deficit of 1 8 per cent which has no chance of being bridged by conventional supply sources2• India has a population of I bi l l ion, 70 per cent of whom l ive in 0.7 mil l ion vi l lages, of which 82,000 are not electrified and 1 8,000 have no chance of having electricity except by onsite power packs. Most of those e lectrified by rural grid supply, are economical ly unviable on account of

* Author l'or correspondence.

low load densities thereby necessitating cross sector subsidies and low qual ity tail end voltages. Our vi l lages need rel iable power supply and thermal energy sources, industry needs assured grid power supply and thermal heat through combined cycle systems or efficient combustion and niche areas such as islands, mountains, remote areas and defence instal lations have their own criteria of energy supply and security. Figure I gives the alarming picture of oil sector. As such, the current Energy policy has three componentsJ :

• Energy equity for rural areas through rural energisation

• Grid interactive quality power: tai l end rural feeders voltage support and peak shaving for urban centres

26 J SCI IND RES VOL 62 JANUARY-FEBRUARY 2003

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Figure I - Year wise curve of petroleum consumption in India

• Capti ve power supply for energy security In industry

Capacity addition of 1 0 per cent of the total installed so far, is targeted to be achieved by renewable sources by 20 1 2 when currently it is less than 1 per cent (Nuclear is less than 3 per cent), in addition to demand side management through energy effic iency. Cogeneration and resource recovery from industrial and agro wastes have to be vigorously implemented as wel l . Energy efficiency audits in i ndustry have been made mandatory.

Eight per cent has been projected to be achievable through sustained efforts, reasonable pol icy options and steady focus through R&D implementation via structures already in place4. As a matter of fact, there is no choice except to meet these targets for there is pers istent demand for generation of l i ve l ihoods through v i l lage industrialization and low energy input agriculture and on account of considerations of c l imate change and urban requirements of restricting population influx and pol lut ion control on an urgent basis . Most recent estimates of sector wise energy demand and suppl/ are given in Figure 2 A & B . A possible Task Technology Matrix for Solar Energy Uti l ization, as proposed by Gupta6.7 in Figure 3, is relevant to developing countries l ike ours .

Nuclear ,

�Jatllral ga5 82':,

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Figure 2 - India' s reference energy base'

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SOLAR TECHNOLOGY

TASK

Operation Energy Need

A. FOOD

GUPTA & RAMACHANDRAN: SOLAR ENERGY FOR INDIA

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I rrigation Production --=-------I----t--+----;--+--+---+--+---;I--+--+----+--+----1 * * * Winnowing * *

* * Drying Storage -��----+-_+--:;:__t__-:;:-+-_f--+__:::_+----1I__-+---+--t__-+--.-_I-__I

Cooling * * * * Pasteurizing *

* Processing Grinding ----�-----+--_r--�---+----�--�_4---+--�--�--4_--+---�__I * * * *

Cooking

B. POTABLE WATER

C. HEALTH

D. HABITAT

Pumping

Sterilization

Purification

Chilling

Sterilizing

Distilled Water

Hot Water

Bricks Drying

Steam Curing

Hot Water

Space Heating and

Cooling

Lighting

E. CRAFTS AND VILLAGE

INDUSTRY

Shaft Power

Process Steam

Electricity <1 kw, 3kw >

F. TRANSPORTATION

Mobile Power

Distilled Water

G. EDUCATION

TV I Radio

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* Figurc 3 - Task-technology matrix

27

28 J SCI INO RES VOL 62 JANUARY-FEBRUARY 2003

Historical Survey of Early Solar Energy Developments

Except for evolving swadeshi devices during freedom struggle, such as solar cooker8, pioneering efforts in solar energy were initiated in late fifties at the National Physical Laboratory on solar water heaters9, dish cookers, solar hot air engines; in solar dist i l lat ion and solar pond at Central Salt and Marine Chemical Research Institute; Radiation Statistics, Comfort Studies and Long Term Collector Designs at Central Bui lding Research Institute. Additional ly, there was systematic work on Radiation Resource Assessment by India Meteorological Department, which got considerable boost because of International Geographic Year (lGY) studies 10 in 1 972. Valuable energy courses were also started in IITs around 1 970s. Principal stress was on indigenisation and to meet the keenly felt needs of the people with overrid ing social relevance and rather superficial appraisal of ecological and economic impl ications.

These researches have been documented in the proceedings of allnual meetings of the informal Solar

Energy Working Group, which was quite active t i l l 1 976 and were summarized in a country paper to UNESCApl l . In 1 975, a national plan was formulated by the Solar Energy Panel of National Committee on Science and Technology of the Department of Sc ience and Technology, Government of India with far reaching recommendations with regard to structure and program of R&D and institutional framework requi red for the effort. Principal stress was on 3-5 y duration short term projects on solar water heating, solar thermal pumps, active solar heating of factory spaces, absorption cool ing, low temperature ORC power, Cu in diselenide (CIS) solar cel ls , technology development for mono crystal si I icon cells, col lector design and analysis of radiation data. Thi s committee laid the foundat ions for systemati c research and technology development in the field of solar energ/ 2 for the next 1 5 y. Solar thermal pumping, absorption air conditioning and low temperature ORC power generation, even though technical ly feasible, got left out on the way in l ate seventies and were substituted by solar PV systems in early e ighties not only in India, but around the world as we l l . In India, the philosophy sti l l was for satisfaction of basic needs in vi l lages, and indigenisation i e, energy equ ity. This report, known as Bhide Repore2, was i ncorporated in the general S&T Plan of the Nation.

Energy security became an important factor after oil shock of 1 973 and energy qual ity in early nineties after the stress shifted from bas ic needs to income generation and commercial i zation of renewable systems-a process sti l l going on . State Nodal Agencies, a significant base for manufacturina 0' Indian Renewable Energy Development Agency (IREDA) as a financial arm for subsidies, loans etc . , and National Institute of Renewable Energy (NIRE) as a technical arm for systems design for end use packages through hybrid systems, have been configured and are now in place. India today has one of the largest solar energy R&D and appl ication programs in the world and this is coordinated by a ful l fledged union ministry of Government of India : the Ministry of Non-Conventional Eneray Sources

1 4 0 (l\,1NES) . Solar Energy Working Group has become Indian Section of International Solar Energy Society.

What then stops solar energy from becoming effectively vis ible: national malaise of non-focused effort, unwi l l ingness to learn from earl ier fai lures, a lurking dichotomy between rural concerns and industrial priorities and tendency to get away with shoddy engineering, which is su icidal for ful ly exposed solar systems in high temperature, dust/ moisture prone ambience of tropical c l imates. However, we are definit ively on the way and there are some outstanding successes to cheer, as we sha l l see in the section of case studies.

Solar R&D and Technology before 1975

Solar Energy can be used in three modes:

Direct solar heat 2 Direct solar electricity (mainly using PV solar

cel l s) 3 Bio-solar using biomass : biomethanation,

gasifier and producer gas and photolytic bacteria based microbial hydrogen or photochemical cel ls producing hydrogen

In the unstructured program before 1 975, main concentration was in Sector I on direct solar heat and on Sector 3 on bio methanation (biogas) 1 5 . There was practical ly no work in Sector 2 except for pioneering research in India done by Central Electrochemical Research Institute, Karaikudi and Electronics Department of Jadavpur University, Calcutta on solar cel ls . Only enduring work that provided sc ient ific challenges or is highly relevant in scale of soc ia l priorities is being included in th is review for reasons of space availabi l ity.

)-

GUPTA & RAMACHANDRAN: SOLAR ENERGY FOR INDIA 29

Solar Hot Water and Hot A ir

Natural c irculation type water heaters designed for 60 DC and 1 40 L/day capacity were designed and developed in Indi a prior to 1 975 _ High capaci ty, highly effic ient corrugated col lector system')

developed by NPL, New Delh i , was abandoned in favour of mechanical ly bonded pipes and fin system, developed by CBRI, Roorkee, because of difficulties of repairing leakages due to corrosion_ Nonpressurized vertical storage tanks were used with float valve water control, external to the hot water tank. There was some problem coupl ing these to showers or electric geysers because of h igh pressure in the latter. Prel iminary i ntegration with bu i ldings was attempted by providing cold feed water tanks, normal ly at terrace level , on the top of stairwel l to give the necessary head. Electric heater in the hot water tank with thermostat control (but w ithout sacrific ial anode) was optional addition for regions having winter monsoons". Some of them were tried for space heating at DRL in Ladakh by making the storage tank as a rectangular flat panel heater ' 6 . There were also tri als with fan coi l units with c irculating hot water 1 11 a BHEL factory 1 7 . At least three manufacturers were supplying these systems commercial ly by 1 978 . Complete des ign procedures for solar water heating systems, using solar uti l i zabi l ity concept were also evolved along with data on radiation statistics for four princ ipal metro ci ties and anc i l lary data on opt imum slopes, t i l t factor for radiation estimation and integrated design I X. Properly tested solar air heaters with pulsating flow in cross placed corrugated absorbers and absorbers with aluminium and G.I . mesh matrices were also tested and evolved for possible use in solar drying '6 .

A honeycomb solar col lector lls ing drinking straws was evolved at BITS, Pi lani and later analyzed by others ' 9 . Concurrently, the first solar pond using sea water was designed and tested by CSMCRI at ryo Bhavnagm-- .

Solnr Thermal Pumping and Power

Four sign ificant attempts were made for solar pumping, al l us ing flat plate col lectors:

At Aurovil le, water based non-boi l ing collectors coupled to an imported reciprocating type SOFRETES motor with bui l t in pump for re-c i rculation and using butane (cooking gas) working flu id attained sun to water efficiency of

0.5 per cent and was therefore abandoned. It was neither s imple nor cheap2 1 .

2 Direct contact pentane based water pump, was developed at Pi lan i22. However i t could not stop loss of pentane carryover by pumped water. Even though i ts s impl ic i ty was tru ly attractive, i t had to be abandoned because of pentane loss.

3 A Swiss designed motor pump was coupled to boi l ing collectors having Freon 1 2 as heat transfer f1uid23 . The motor pump was designed on site as an appropriate technology mechanism and i t gave endless trouble and was thus abandoned.

4 A 1 0 kW solar power station using water at 80-90 DC via flat plate solar collectors with mirror boosters at lIT Madras, in collaboration with MBB from Germany. The station worked for many years but had a parasite power of 6kW and the overal l effic iency ( including parasite power) was less than I per cene4.

Even though all these projects were finally abandoned, they were at that t ime right at the frontiers on worldwide scale and were based on tremendous scientific effort and human fai th . These experiments also gave the first hard data on costs, performance, problems of system des ign and fostered i nter-inst itutional cooperation nationally and international ly .

Solor Distillation and Drying

The;-e were major projects in Solar Dist i l lation based on masonry col lectors topped with glass sheets at CSMCRI, Bhavnagar25 and for drying of cereals by tunnel type dryers with glass i nflated plastic covers at Annamalai Univers it/6. These were technically successful but paying capacity of users in water defic ient areas was far below the rates expected on no profit no loss bas is for potable water and the drying of cereal crops had too Iow a load factor to make any economic sense. Drying of vegetables, plantation crops etc, had not yet been undertaken. However, a conical plastic solar shel l 'THOY AM' of MCRC became quite popular for indiv idual households27 .

Other Solar Thermal Technologies

There were some projects on Solar absorption refrigeration and open cycle desiccant type of refrigeration28• 2') with COPs of nearly 0.4 but they never came off the ground for users, in spite of pi lot


trials on a cold store. These were thrown on the dung heap of history for socio-economic reasons in spite of being technical ly successfu l .

Undue stress on energy autonomy rather than energy security through hybridization postponed possible successes for future as we shall shortly see in the next phase of the work. This myopic outlook nurtured by ideali stic zeal had its tol l world wide, as reported by Tabor'o in a retrospective published recently in h is col lected papers.

R&D after 1975

Solar R&D was ful ly structured since 1 975 with central ized funding and many inst i tutions doing R&D efforts in various areas l isted as of priority interest . Only significant ones are detai led here.

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Solar Collector Research

Flat Plate Collectors Using Water

First major advance in making high efficiency solar exchanger was fabrication of Bonduct panel s' )

originally meant for freezer cabinets i n refrigerators. Bad quality of water created the problem of corros ion in thi s integral uni t containing pneumatical ly expanded tubes in two layers of aluminium bonded thermally . It has now been replaced by aluminium fins, plate with copper tubes integrated with minimal contact resistance.

. Second major advance was mechanical fabrication of Sol chrome Cu in Cu col lector strips with an integral black chrome selective coating with LIE ratio of nearly 8- 1 0 and stable l ife ti l l ) 50 °C [55] . Thi s has now been upgraded to selective nickel

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(1 =0.01 1 7 , V=1 .058

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Figure 4 - Experimental performance curves of PEN solar air heater for large area use 1 - S mooth metal plate with underflow, Single

olass, 2 - Matrix ( = 0,667), underflow below glass through I , 3 and 3a - Corrugated metal plate with overflow ahove plate, below �lass, 4 - Diagonal matrix between p late and glass-ordinary paint, 5 - Selective copper p late With underflow, Single glass, and

6 - Diagonal matrix between plate and glass-selective paint

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GUPTA & RAMACHANDRAN: SOLAR ENERGY FOR INDIA 3 1

and cobalt coating33 stable up t i l l 250 DC. Absorber plates used by Sarvodya water heaters have NALSUN coating. Two phase water heating col lector was developed by Soin 34.

Low mass systems, proposed by Hol land [35] . using foi l type fins have not been developed in India, BNL col lectors (Mumbai) using stretched PVF cover sheets were punctured by crows in less than a week,

Low flow systems having a better annual col lector efficiency have been recommended36 for pumped systems, but not yet integrated for thermosyphon water heating systems in India.

Advanced collectors with a loss coeffic ient of less than 2 watt/m2 Dk, developed at CSIR037 using paral lel strips of Teflon in accordion fashion for convection suppression, non iron glass and extra insu lation would be ideal for India, if durable materials can be obtained on an industrial scale, as these do not involve a change of technology.

For existing technology col lectors, an Indian standard has been framed to ensure use of durable materials for long l ife trouble free operation.

2-D Concentrating Collectors

Some scattered work has been done on evacuated tubular col lector (ETC's) and on parabol ic trough col lectors but not developed industrial ly . Integrated glass tube col lectors with heat pipes, as proposed3x for uses between 1 00- 1 50 DC, wou Id be the next l ine of development/adaptation as they are stationary and cou ld have longer l ife in tropical c l imates than VG series col lectors developed by Phi l l ips earl ier and now manufactured by Fournel l in Canada.

3-D Concentrators

Schaffler concentrators with a secondary reflector at focus and alterable focal length for seasonal adjustment and c lockwork based diurnal movement from East to West have been widely adopted for community cooking and some R&D has been done to format them for avai lable Indian materials and cost effecti veness. These are manufactured in India at three places and have been used in a series of 84 numbers to do steam cooking for ten thousand people39.

Flat PLate Collectors Using Air

The earl iest work on solar air heaters with proper scientific testi ng was done on four solar air

heaters l 6-one with pulsating flow, one plane sheet absorber and two with aluminium and G.I. mesh matrices. The recent work has been for developing configurations for l arge-scale roof integrated air heaters for drying tea, coffee, spices, cashew, vegetables and fish in a hybrid mode4o. One integrated col lector with aluminium corrugated sheet absorber and overflow between glass cover and other with a matrix diagonall y placed within the overflow space and sprayed with a selective b lack paint have been tested. Test resu l ts are given in Figure 4. As can be seen, there is doubl ing of efficiency in over flow col lectors by using in depth matrix absorption and reducing radiation loss using selective paint.

Solar Bowl

While developing a solar bowl for steam generation at Aurovi l le, in i t ia l ly for cooking, a whole series of analyses and technology have been developed for making a large, 1 5 m diam spherical bowl integrated with the kitchen bui lding on one side and the conventional Instant steam Boi ler cooking on the other side. Achieving an accuracy of 1 0 min arc at 4 m distance, required choice of special adhesives with neutral pH to fix 1 1 000 back coated mi rror segments on prefab ferrocement curvi l inear channels with laser contro l , thin enough to take some curvature. Ray tracing techniques were used, with proper provision of a fini te Sun size, to achieve a focal width of 28 cm as compared to earl ier 40 cm with this low energy technique. To avoid pressurized water flow or two phase heat transfer using water, a gear pump was devised to circulate thermic fluid from a tank to the heating loop in the boiler, tracking the Sun with the aid of a computer and a split PV sensor. A secondary heat exchanger was used for steam generation in tandem with fuel fired instant steam boi ler4 1 .

Solar Pond

A NaCI salt stabi l ized solar pond has been made at Pondicherry and is working for the l ast four years to give temperatures of 70-80 DC for ten months/year for power generation using ORC engines with methyl chloride. Four of the critical problems of Solar Pond technology namely:

Salt containment strategy 2 Passive and continuous dosing of salt :1 Pond clarity in tropical humid c l imate 4 The security against cyclones and monsoon rain

have been solved in a satisfactory mode by


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GOOD CLARITY

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Figure 5 - Transmission in solar pond (hot humid cl imate)

using local ly avai lable low energy materials, green wind break shelter fences. A new equation of Bryant Colbeck type by Arumugam42, i s :

T(x) = 0.28 - 0.08 e ln(x), where T (x) i s the transmittance at pond depth x

from the surface, and the equations are shown in Figure 5 .

Solar Cooker with TIM

After years of country wide trials on Mohan Parikh's Box type cookers evolved in early seventies, a national model of box type cooker has been evolved with a corresponding Indian Standard on solar cooker43 . Some of the R& D to enhance its peak temperatures, decreased cooking t ime, reducing the need for hourly orientation, cooking in cloudy days and even sun down cooking have been researched . For sun down/cloudy cooking, a thermostatical ly control led relay switch with a t imer activates a 200 W strip heater thermally bonded to cooker plate44. Peak temperatures are enhanced by using a step type two part reflector based on truncated CPC concept or a Transparent Insulation material (TIM) with a proprietary name ORALUX between two glass covers. Nahar45 (Figure 6) describes the results of a

box cooker with TIM of LlD= I 0, 40 mm cel l s ize and 0.2 mm thick Polycarbonate wal l s . Position of two reflectors : S-W in the morning and S-E in the afternoon obviate the need for tracking completely.

Solar Photovoltaics

Monocrystalline Silicon Cells

As stated in an earlier section, India started manufacturing its own Monocrystal-S i l icon cel l s around 1 975. The recipes were developed by Bhabha Atomic Research Centre and these cells were produced at Central Electronics Ltd, Ghaziabad. These cel l s have seen duty from Everest to Antarctica and i slands to desert areas in diverse appl ications. Solar lanterns, home l ighting systems, street l ighting systems and vi l lage e lectrification projects based on these rel iable cel l s are widespread even though costs of electricity currently works out to be Rs. 1 5-Rs. 1 8/kWh (administered electrical tariff i s around Rs . 2-1 . 4.50/kWh) . At present, there are three wafer manufacturers, two manufacturers of solar cel l s and 23 manufacturers of PV modules. Solar cel l s have a production l ine capacity of 9 .5 MW/y and an idle capacity of I I MW/y for which cel l s are imported because of economics. Somewhere in late I 980s,

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Figure 6 - TIM solar cooker (box type)

when S i l icon became a strategic material , India started manufacturing its own solar cel l purity grade si l icon ingots based .on a process developed at Indian Institute of Science. However, production costs of Indian wafers have been h igher than imported ones because of need for capt ive power, impure H2 and slightly less effic iency at production level and greater proportion of rejects . Life , rel iabi l i ty, material and energy costs are as good as international cel ls . In early nineties, a pi lot production l ine for high efficiency cel ls (> 1 6 per cent) based on laser grooved

I h b · . 46 buried contact techno ogy as een 111 operatIon .

BOS Components with greater efficiency and reliabi l i ty are also being designed and fabricated by main stream manufacturers. Qualification standards have been codified and getting gradual ly incorporated. But qual ity assurance program of components, systems and ful l turnkey projects has yet to take off. Some stand-alone projects providing power to remole unelectrified vil lages are described in ' technologies' subsection . Sector wise break up by end users are avai lable in the annual report of IREDA47

Thin film Solar Cells

To save on material costs and improve energy payback period, a number of projects on Thin fi lm solar cel ls have been init iated in India and are at various stages of R&D, pi lot production and

commercial production . As these are proprietary processes, technical detai ls are hardly avai lable. State . . � d' � of Art RevIews for US developments and for In la are available.

Single Junction-Silicon Cells

B harat Heavy Electricals (BHEL) set up a pi lot plant for production of single jn s i l icon cel ls to produce 30 cm x 30 cm solar cel ls with glass substrate during 1 985- 1 992, using imported technology . Even though trial samples were produced, it has not gone in mainstream.

Multimple Jn - Silicon Cells

A 2-jn s i l icon cel l process know how and a pi lot production unit is being developed49 at lACS, Kolkata. They have produced 30 cm x 30 cm cel ls with an unstabi l ized cel l efficiency of 10 per cent . The Process has yet to go for production .

Polycrystalline Cells

CIS (copper indium diselenide) cel l s are being researched at Indian Institute of Sc ience ( IISc), Bangalore (Krupanidhi , private communication), where smal l area CIS cel l s with conversion effic iency of 1 1 .2 per cent have been fabricated. Indian Institute of Technology (lIT), Delh i has started work on nano composite copper dioxide thin fi lm cel ls . Work on CdTe (cadmium tel luride) thin fi lm cel l s has proceeded at National Physical Laboratory, New Delh i . Global Solar India, Polyflex Corporation, near Delh i , and Eco Solar, Pune have produced sample cel ls but they have yet to go into production48 .

Silicon Thin Film Cells

S i l icon thin fi lm cel ls are also being developed at Jadavpur University and lACS, Kolkata. Microcrystal l ine SC:H cel ls are sti l l at conceptual stage in India. World class qual ifying fac i l ities exist at Solar Energy Centre of MNES4 near Delh i .

Photovoltaic Powered Electrochrol11ic Windows

(ECWs)

The switching operations of an electrochromic window (ECW) demand a small DC voltage. In a typical ECW, the current dens ities involved are of the order of 0 . 1 mA/cm2 and the switching times are in minutes. The power required to operate an ECW is general ly drawn from mains via special wiring. This adds to the i nstal lation cost of an ECW, in addition to operational cost, however, smal l i t may be. One of the ways for lowering the instal lation charges and to


make an ECW self powered is the integration of EC and photovoltaic (PV) .

A smal l area PV cell can provide sufficient electrical power to switch a large area EC window slowly, as would be appropriate for an architectural window NPL (private communication, 200 1 ) . I l ists some typical characteristics of EC coatings and thin fi lm, hydrogenated amorphous si l icon (aS i :H) PV cel ls and shows general compatibil ity. As can be seen from this table, the typical PV current density output is compatible with the switching requirements of an EC device, as are the overall energy and power densities.

Different designs integrating EX with PC, e g, side-by-side PV -EC or the tandem PV -EC can be thought of. In the former design, the PV array can be interconnected to provide multiples of the individual cell voltages whereas in the latter one, the single cel l PV voltage can be increased by incorporating a double-junction cel l at some cost in window transparency.

Based on this novel concept, devices employing a wide band gap thin fil m a-SIC: H n-I-p- as a PV cell and a LixWO,/LiAIFJV205 deposited monol i thical ly on a conducting glass substrate have been successful ly demonstrated. Thin film group at NPL has in itiated this study recently to find a suitable combination of EC and PV for architectural windows This project has just been started at NPL 50.

Photo-electrochemical and Bio-solar

Main work in this field has been production and storage of hydrogen produced by solar radiation input.

Septum Cells for Hydrogen

This uses mixed oxide Ti02 (nano structured)In203 photochemical e lectrode cell producing 1 005

Llh .m2 of hydrogen under an external input voltage of 0.9V with i l luminat ion of 0.5 W/um2 in NAOH electrolyte. These mixed oxide electrodes give h igher rate of production due to i ncreased range of absorption caused by M20" decreased energy gap and increased photoactive surface area of electrode. To get the voltage, a semiconductor SC-SEP (PEC) solar cell ratio is used, using thylekoid membrane as used in photosynthesis.

This is a two compartment cel l in which the semiconductor thin film acts as a propel ler electrode between two Redox solutions, one being i l luminated by Sun and the other being in dark. This wi l l produce enough voltage for photo electrolysis of water to produce H2 and O2. Final configuration, as evolved, up t i l l now is SCE/IM/NaOHIT102 (ns) + In20,l (V02)/TiiSM It2S04 PEW) and results have been obtained under a radiant flux of 80 W/m2 at the rate of 1 6.8I/h.m2. A cascaded design is being final ized for a demonstration model at the Hydrogen Research Centre of Benaras Hindu Universit/ ' .

Microbial Hydrogen Using Photolytic Bacteria

After a decade long study of photolytic bacteria at Murugappa Chettiar Research Centre, Chennai they have now optimized a blend of microbial co- culture of C freundii and biogas isolates to produce H2 sustainably from spent disti l lery wash, sago waste and whey in the laboratory. A pre-commercial pi lot scale plant of 6 m3 bioreactor capacity (nominal ly 1 0 rn' for di lution to suppress sulfate inhibitor) using disti l lery waste as substrate has been commiss ioned alild tested at a factory site. It produced 1 .2 m' H2/h at a purity level of 96 per cent52. In most photo biological systems using natural acti vity of bacteria and green algae to produce hydrogen, conversion efficiency from sun to hydrogen is nearly 5 per cent; the process being absorption of sunl ight by

Table I - Solar PV and EC compatibilit ies for Architectural windows

General Characteristics PV (a - SI : h.S per cent efficient) EC (L1*ion based)

Voltage ( V ) 0.85 0.80

Current densi ty ( M A/cm2 ) 35* 1 0*

PV requirements for switching PV area x conversion Switching time

One meter 2 EC* efliciency ( m2) S

0.005 80

0.05 8

+ Assume 600W/m2 irradiance, EX switching, I m2 area, 50 per cent- I 0 per cent T solar, in 60 seconds, EC=Electrochromic

"

»-.

-


ch lorophy l l and enzymatic use of this energy to dissociate water to produce hydrogen and oxygen . The O2 impl ies that for production to be on a sustainable basis, the inhibit ing oxygen is removed microbial l y and the effic iency of sun to H2 i s increased cons iderably .

Pre-commercial p i lot p lan t H2 was used in an exploratory trial to operate a fuel cel l of PEM type and 250 watt capacity developed by SPIC Foundation, Chennai . Based on the parameters of p i lot p lan t of 6 m3 capacity, a 70 m3 bioreactor p lan t has been designed and i s under fabrication a t Parry & Co. , Nel l i kuppam43 .

Storage of Hydrogen

Hydrogen is being projected as the c lean renewable fuel for coming years. Its energy conversion efficiency is higher than the hydrocarbon fuels and the c lean combustion leads to zero pol lut ion and better engine l ife . The safety aspects are not more severe than those of other fuels . However, because of low density of hydrogen, i ts energy density per un i t volume is low and therefore, compact containment of storage as wel l as its del ivery are of critical importance to i ts use.

Srin ivasmurth/4 has out l ined these detai l s . Metal hydrides have a high energy density of storage, have flexible PTC characteristic making for easier del ivery and creating no hazard in terms of t ime of storage or even leakage. However, there are problems of cost, lower thermal conductivi ty, part ic le breakdown and swel l i ng and pyrophoricity. These are proposed to be solved by simple chemical and physical methods. Also, i nexpensive hydriding all oys are being synthesized and characterized so as to yield cost effective systems for hydrogen storage and del ivery. The hydrogen thus avai lable has experimental ly been used for mnning motorcycles at B HU, Varanasi, at NPL for a refrigerator prototype and at nT, Madras for design ing efficient heat transfer reactors suitable for heat pumps and fue l cel l s4 .

Solar Passive Buildings

Solar passi ve heat ing and cool ing of bui ld ings fol low the same basic requirements and systems i n temperate and tropical c l imates . However, tropical bui ld ings as general l y used in India, have some special features6. They have mostly h igher storage capacity i n the bui ld ing envelop, they have floors d irectly on the ground and the rat ing parameters have to be different because there is normal ly no

mechanical heating and cool ing . Further, it has been found that natural l y condit ioned bui ld ings (without mechanical heating or cool ing) with a float ing i ndoor temperature al low significant heat exchange between the various i ndoor surfaces thereby nu l l ifying the concept of t ime lag of bui ld ing elements, which is so cmcial for bui ldings having a reference set temperature.

A new method cal led solar heat effectiveness method has been devised55 so that it is possib le to separate the effects of good design, conservation practices such as enhanced i nsu lation and passi ve techniques for heat ing or cool ing. It i s a ratio of the heat equi valent of the temperature e levation or depression of a solar room with reference to an untreated room (not outside c l imate) and the heat equ ivalent of the untreated room to reach the comfort temperature. Thus it i s a measure of the fractional d iscomfort removed for a given type of bui lding on account of the conservation or solar strategy used .

Matured Solar Energy Technology Options

Defin ing matured technologies as those, which have gone through qual ify ing tests and pi lot scale testing in the field so as to be bankable projects, fol lowing solar energy technology options can be considered matured for India56.

Solar Thermal

• Solar water heat ing from 1 02_ 1 05 Lip/d . • Roof i ntegrated solar air heat ing systems up t i l l

400 m2 for p lan tation crops, spices and pulses. • Solar cookers for domestic and community

cooking up t i l l 1 0,000 persons .

• Solar dist i l l at ion for l abs, rai l ways , petrol stations, primary health centers and l ight houses.

Solar PV

• Roof top l i ghting systems for homes and schools (up t i l l I kW) .

. • Pumping systems for water supply for agricul ture and community u se from wel l s up to 60 m deep.

• Solar power system up t i l l 1 00 kW peak with grid i nter phas ing or standalone w{th battery backup.

Passive Low Energy A rchitecture

• Roof top fabric cooling systems for multi-storeyed bui ldings such as offices, hotels and hospitals.


• Pass ive draft evaporating cool ing systems for commercial bui ldings and laboratories.

• Roof ponds with moveable shades for houses for hot dry and hot humid c l imates for heating and cool ing.

• Passi ve solar systems for space heating in cold regIOns.

• Low energy bui lding materials with embodied energy per unit floor area at half to one third of the existing bui ldings without reduction of l ife or comfort.

These are systems actual ly working on many si tes with proper turnkey designs, post instal lation moni toring inc luding economic data. What is needed is their mu lt ipl ication and commercial ization to an extent that trained operators can rUIl them with an operating and maintenance manual . Thi s has yet to happen and must happen. However, it w i l l only happen when the National Renewable Energy Pol icy, reported to be on the anvi l now, wi l l see to it that it i s done.

Additional ly on software side, Amer and Nayak57 have developed a method of transient testing of col lectors. Hazra et al58 have developed a computer software on Auto-CAD platform to do thermal design of bui ld ing envelopes, which is undergoing testing of its B-version.

Successful Case Studies

Six cases of solar projects, which have considerable promIse because of their scale, indigenous content, distribution in the various c l imatic zones in the country and priority end uses, are I isted here:

I Solar Bowl

It is a stationary three-dimensional spherical col lector with an opening angle of 1 20 °C, diam of 1 5 m and accuracy at the focus of 1 0 min arc. It has e leven thousand segmented facets of nominal size 1 5 cm x 1 5 cm with back s i lvering stuck with a neutral pH grade s i l icon adhesi ve. Each has been fixed by using a laser beam for fi xing correct ly and it i s sufficiently th in to take sl ight curvature. It i s one of the three bowls in the world of its size and the only one to use prefabricated ferrocement ribs which are doubly curved to give the necessary strength and basel ine shape . Plate I gives a view of the fin ished bowl along with the focused spot on a clear day.

Plate 1 - Aurovil le solar bowl conCCl1lrator

Even though, the solar radiation in hot humid c l imates has 1 5 to 20 per cent diffused component, the bowl is des igned to produce 200 Kg steam at 250 °c with the requisite pressure. The primary thermal loop consists of a thermic fluid with proper expansion tank and a storage capacity of 8 m' for I h transients. The circulation pump is a gear pump with variable flow control led by output temperature. Thi s choice was necessitated to avoid two phase heat transfer, hot spots and pressurized systems.

The secondary loop is a waterline in a heat exchanger i ns ide the tank. Currently, it is operated in tandem with a conventional oi l fired fast response steam boiler using LDO. Bowl is being used for cooking but can be used for absorption refrigeration and industrial process heat . The moveable boi ler arm has to be perfectly balanced, has a diameter of 23 cm with a length of 8 m, counter weighted within less t han I kg accuracy to ensure smooth down movement using differential spl it beam as PV control for clear days and a c lock driven override for cloudy days. Al l the normal operations including emergency procedures are computer control led and use i.ndigenous stepper motors and l ocal ly manufactured boom with a three-l ine surface heat flow exchanger with tangential inputs and special high temperature, moderately select ive i mported paint . It has taken a material input of Rs 2 mi l l ion (funded by Ministry of Non-Conventional Energy Sources, Government of India, New Delh i ) and engineering resource input valued at Rs I mil l ion ( 1 US $ = Rs 46.00. August

>


Plate 2 - Standalone solar PY system at Sagar islands (25 kWP)

200 I ) . The complete system is undergoing post commissioning trials and user acceptance. This wi l l be monitored for ful l one year before the technology is released for public use with complete documentation. It i s a low embodied energy system with ful l bui lding integration and is expected to find some niche use in the temperature region of 1 20-200 °C on a distributed scale4 1 • With the experience gained, a steerable, 8 m dia. reflector is being manufactured for a 10 kW electrical project using an i mported Stirl ing engine from Germany and located less than 200 km away at Vellore Institute of Technology, Eureka59.

2 Standalone SPV Power Station for RL: '-at Electr!fication

Standalone 25 kW solar cel ls based power station for grid qual i ty power supply at Sagar Islands in remote Sundarbans (less than 1 00 km from Kolkata) is one of the 1 2 such projects being tried in those vi l lages which have no chance of being electrified by grid. Typical project costs Rs. 1 0 mi l l ion with 50 per cent outright grant from Ministry of Non-Conventional Energy Sources, 40 per cent low interest 1 0-y long loan from IREDA to the

Vi l lage Energy Cooperative and 1 0 per cent down payment by the users . The system is meant to supply 220 V electric i ty to houses, run a v i l lage solar pump and a flour grinding machine. Three 1 5 kV inverters are used for rel iabil ity. The users pay according to the connected load which is current l imited. The duration is fixed from the Power Station by mutual agreement. Plate 2 shows one such station started recently and reported by Gonchaudhuri60. There is tremendous enthusiasm and demand and energy tariffs are less than diesel based power supply with the additional advantage of noise and pollution free power supply. Based on the experience of other smaller projects in Ladakh and Spiti i n the Himalayas, the only snag is going to be the replacement cost of batteries after 5-7 years . The energy density of Indian batteries and their l ife under cyc l ing operations has to be enhanced by a factor of 2-3 to reach the international standards. Just now, i t i s smooth going in terms of energy quality, security and equity. Two parallel projects based on gasifier for 500 kV A are being studied s imultaneously. It is too early to make a decisive comparison because, even though, they are cheaper, more rel iable and have no battery problem, they are not as neat and status providing. A sociological


Plate 3 - Solar air heating systems (SAHS) installed by Planters Energy Network (PEN)

survey by Indian Statistical Institute52 concluded that it has increased not only the convenience of individual user but has also provided for community faci l i t ies for television entertainment and internet connection later on . It has also increased the working time of cottage industry units and made i t possible to have more crops than normal with rel iable i rrigation water supply. It is almost a revolution in making.

3 Roof Integrated Solar A ir Healing Systems for Plantation Crops

Almost 25 such projects have been done in the Ni lgiri Hi l ls, South India during the last 1 5 y b

.y

Madurai based Planters Energy Network (PEN). AIr heater uni ts are in modules of 200 m2 unit integrated with factory roofs . Products so far dried in a solar diesel hybrid mode have covered tea, coffee, veaetables and fruits, spices, fish and lent i l s . The fin�ncing terms are simi lar to Rural Electrification projects and are demand driven.

Currently, these air heaters are baffled, separated overflow systems under suction mode (Plate 3) with a temperature rise of 30-35 DC. As discussed in Solar Energy R&D earl ier, these air heaters are being improved to achieve double the effic iency by using corrugated absorbers and diagonally placed galvanized iron mesh matrices with local ly developed selective paint that i s sprayed. No slUch project has been done with the new heaters yet detail ing the incremental costs per unit area, reduction in the specific area per unit dried product and reduced blower capacity required. The current status of these systems was out l ined40. This app lication has great future in view of the stress being laid on agro-processing for qual i ty improvement. Coupled with organic farming, the solar dried products command a premium price in the i l!lternational market. Extension has st i l l to be made to cover herbs for beauty and healthcare.

).

J

GUPTA & RAMACHANDRAN: SOLAR ENERGY FOR I NDIA 39

4 Five kW Wind Solar Hybrid System at Chunambar Island

A vacation retreat was created on a small i sland in the delta of a small river near the coast in Pondicherry. Local tourism department in collaboration with State Nodal Agency has commissioned IT Power (India/2. 50 to design a standalone hybrid windsolar energy system of 5 kW rating for l ighting 6 guest rooms, one conference room, few outdoor l ights and one solar pump, all using CFL lamps. The system is shown in Plate 4.

The system specifications are for providing a connected load of 460 W (operati ng for various t imes of operati on) with a total consumption of 12 kWh/d.

Wind electric generator 3 .3 kW (rated at I I mls)

Solar PV System 1 .8 kW (Peak)

Expected annual generation is 5000 kWh/y with two th ird generated by wind and one third by solar energy with costs provided by Central Government

and State Government in the same ratio . The system is going to be moni tored for a ful l year at 1 5 per cent of total equipment costs of Rs 1 .5 mil l i on to check if the l oads are properly met. Breakdowns in terms of equipment rel iab i l i ty and operation are sti l l to be checked. MNES i s providing a lot of hybrid systems to create rel iable sources of mini power supplies up t i l l 1 0 kW in isolated locat ions with obvious relevance for campuses, defence instal lations, is lands and h i l l communi ties. This s i te has an annual mean wind speed of 4.5 mls and an average global dai ly radiation of 6.5 kWh/d except for winter monsoons. But i t so happens that when solar radiation is lower, winds are higher, both durabi l i ty and seasonally, and that is l ikely to make the wind-solar hybrid both technically and economically feasible.

5 Solar Passive Heating: LEDeG Trainees ' Hostel, Leh

LEDeG (Ladakh Ecological Development Group) is an active NGO in Ladakh . This project is

Plate 4 - 5 kW wind-solar hybrid at Chunambar island


located at Chans'pa Centre in Leh . . C limate in Leh i s cold and summer (temperatures below 30 °C and has over 320 sunny days per year. The LEDeg Hostel provides sleeping accommodation for 24 persons with toi let, laundry, and study faci l i ties al l integrated in the bui lding. The bui lding has two floors with 1 2 double bed rooms and anci l l iary spaces. It is set to the northern part of the Chans'pa campus, on a slightly south facing slope. Tradit ional techniques have been modified and adapted to ach ieve energy efficiency . The load bearing walls of the ground floor are made in rubble masonry with mud mortar. The upper floor uses load bearing sun dried mud bricks (adobe) in mud mortar. Partit ion wal ls are a lso executed in adobe. The i ntermediate floors and roofs are timber framed, with poplar wood joists covered by twigs, grass and earth. A small slope has been given to the flat roof so as not to create a sag in the middle. Most of the rooms are predominantly south facing with no overhangs for max imum winter gains. Two wings of rooms are s l ightly angled to each other, demonstrating that solar orientation need not be interpreted i n a strict orthogonal grid lay out, and can allow some latitude for variations in orientation.

At the center of the bui lding is a south approached air-locked entrance leading to the study room which has another study room on its top which can be used as a dining space when needed. S ince these spaces are used at day t ime only, they are heated by south glazing ti lted at 60 degrees to the horizontal . The directly gained solar heat is stored in

J P

. t

, S "" ,,:6 ()<., pn 'J.:., .....

the mass of the bui lding and the warmth is retained for few hours after sunset. P late 5 shows the bui lding in plan .

The bedrooms have been provided with a mix of windows and glazed wall s . Some of these are in Trombe wall design with vents for convecti ve loop formation. Others are without vents for comparative studies, special ly as heat is not required in the bed rooms i n the evenings. South wal l s are painted black for better heating. For tight sealing, all openings have cork based weather strips at the edges. For hot water supply round the year, a flat plate solar col lector using thermosyphon system is provided on the roof at an angle of 60° t i l t . All spaces in the bui lding have good daylight. For l ighting at n ight, solar PV cel ls wi l l be used.

The thermal systems worked satisfactori ly in winter. Temperature i nside bedrooms stayed above 8 °C during moderate winter when outside �emperature dropped to - 1 7 °C. Hot water systems also worked wel l .

This type of architecture is new for Ladakh, cost was lower than the normal construction due to better management. Payback period of even the expensive components l ike glass is as low as as one winter season. The bui lding uses just the minimum amount of artificial heating by bukharis whereas it would have typical ly consumed over six tonne of firewood to heat every winter per room64.

' .

. ). M_I '�lrll!" '�:"�,.-1. YI'! ri �-:� ·;r(�, c-tf'�"""""1-� f"�r� r('.o�.! (.1 %·.,t ,:, ��, {·,;;:tlC(\ -�

Plate 5 - Solar passively heated LEOEG trainee hostel, Leh, Ladakh, India-plan showing orientation

>

'r


6 Solar Passive Cooling: Torrents Research Centre, Ahmedabad

This i s one of the largest solar passively cooled commercial bui ldings in hot dry c l imates. It has a floor area of 20,000 m2 and with an additional cost of civi l works of 1 2- 1 3 per cent ( including that on the extra insulation). A ircondi ti oning plant capacity has been reduced by 40 per cent and the payback period is less than one year.

The center is a complex of research laboratories comprising al l the disciplines of pharmaceutical research requi ring c lean areas of class 1 0000 and dirty areas emitting obnoxious gases. It demonstrates the use of innovative technology solutions which have integrated space condit ioning, day l ighting and dust control without compromising required levels of thermal and visual comfort and indoor quality. In the process a new bui lding ethic has been created, which is quite stunning.

Passive cool ing is provided by a system of downdraft evaporative cooling stations operating in in let shafts and powered by solar chimneys on the bui lding periphery . The inlets and outlets of the laboratory are careful ly designed so that there i s

continuous natural flow of fresh a i r so much so that even the chemistry laboratory does not stink. The maximum inside temperature has been 30 °C with a fluctuation of not more that 4 °C during 24 h with observed 6-9 changes/h . The only uncomfortable season was during the monsoon when fans had to be used. Plate 6 shows a view of the bui lding; its performance and economics are l isted by Patel and Zaveri65 .

Special care has been taken to cover the roof deck with white ti les over vermicul i te insu lation ,

cavity brick wal l s have also been fi l led with vermicul ite and heat bridges caused by beams have been reduced by terminating them before the ends. Dust control has been achieved by creating local turbulence due to half round ceramic t i les on the inlet and cobwebs have been avoided by rounding all the corners.

Economic and Ecological Impact of Solar Energy Utilization

The normal overriding consideration of evaluating energy systems alternatives by economic yardstick of $ 1 .0 mi l l ion/MW instal led cost and 6 cents/kWh energy delivered as the upper constant do

Plate 6 - Solar passively cooled building-Torrents Research Centre, Ahmedabad (20,000 m2)


not apply to a developing country l ike India because of perennial energy shortfalls and requirements of energy qual i ty, security and equi ty . We do not have grid system everywhere and cannot have i t everywhere. Even though energy efficiency has a higher priority over solar energy, as the investments involved are less than a quarter of the amount, solar energy uti l i zation has to be resorted to for considerations of clean development and environmental benign-ness as wel l as availabi l i ty at the point of use66. This is , provided we have rel iable working systems backed up by trained energy service teams, which additional ly provide l ivel ihoods. India has taken the route of commercial ization under the consistent pressures of international agencies but it cannot be the single option . It may be valid for urban areas and i ndustries (even in rural areas) because of space constraints but a partial hands on approach incorporated in a composite recipe, dictated by site specific considerations based on scientific approach

e.g. the criteria of maxImum efficiency per unit capital cost and energy payback period of less than ten years has to be adopted. Comparative costs of various renewable options per unit insta l led and energy delivered have been compi led44 and on a ratio basis , these should be sti l l valid (see Table 2) .

In spite of all the noise by planners, level field does not exist for new technologies in view of socially determined prices of fuel delivered. I-Iowever, heavy debts i ncurred in i mport of o i l and crushing envi ronmental consequences of coal based generation with the additional burden on transportation systems, h igh ash and sulphur content of Indian coal, inefficient operation of power plants and pitiable condition of electric distribution lead to the imperative of using solar energy if and only if rel iable systems can be delivered, instal led and guaranteed. However, since solar energy can meet only up to 1 0- 1 2 per cent of national needs, efficiency of generation of conventional power, distribution and

Table 2 - Various Energy Alternatives: Discounted Costs and Tariffs ( Including T & D Costs)

Costs of Alternatives I nterest rate 1 2 per cent I nterest rate 5 per cent Rs/kW Rs/kWh

Power, Energy, Power, Energy, Power, per cent Energy, per cent Rs.lkW Rs.lkWh Rs.lkW Rs.lkWh Ratio With Coal Ratio With Coal

A. CONVENTIONALS CONS IDERED AT 1 2 per cent I NTEREST

I Nuclear (AEC) 72798 1 .83 50942 0.7 1 1 30 1 32 Taking i nto account

2 Nuclear (AEC) + 87279 2.20 57649 0.8 1 1 56 58 period of waste disposal gestation of

conventionals

3 Coal ( 800km) 5n053 1 .39 56406 0.79 1 00 1 00

4 Natural Gas 492 1 0 1 .22 56308 0.79 88 88

(800km)

5 Hydel by Dam 52 1 00 1 .20 29345 0.38 93 88

6 Diesel Power 50857 1 .56 1 04 1 99 1 .49 9 1 1 1 2

B. RENEW ABLES CONSIDERED AT 5 per cent I NTEREST

7 Small Hydro 1 780 1 0.43 1 4532 0.2 1 26 1 5

8 Biogas 47855 1 .23 77358 1 . 1 1 1 38 80

9 Producer Gas 425 1 1 .3 3 85367 1 .22 1 52 88

Power

10 Solar Pond 1 4464 0.35 1 7924 0.23 32 23* *Saved energy

(Thermal)

I I Cogeneration 27573 0.64 30765 0.29 55 40

(Bagasse)

1 2 Wind Farm 39085 2.0 1 37633 1 ..34 67 96

:../

>-

GUPTA & RAMACHANDRAN: SOLAR ENERGY FOR I NDIA 43

improvement as wel l as end use effic iency measures have to be vigorously adopted apart from energy conservation, cogeneration and combined cycle plants. Concise surveys of possible advances in conventional power generation68 and biomass residue

. 62 d optIOn are reporte .

The Future

The future is both bright and frightening. Business as usual s i tuation can lead to a debt trap as oil deficit alone amounts to Rs. 390 bi l l ion and to regular brownouts and blackouts. It can be bright if decentralized solar option is taken in tandem with biomass, energy use efficiency, cogeneration and improved means of conventional electrical generation in a concentrated manner. For these, pioneering examples and some competent studies exist, but a national integrated energy policy i s taking too long to be announced and implemented. It wil l require courageous action, as it is pol i tically risky and would mean tightening the belt by al l sections of the society. There is no choice.

Acknowledgements

This review has been a great joy because both the authors have been in the main stream of solar energy effort right since i ts inception. To see i n perspective over a period of t ime, the contributions of our col leagues and students in the background of worldwide developments has been truly a privi lege. Any omission of significance is unintended and regretted.

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C L Gupta is a Professor of Applied Sciences and Head of Solar Energy Unit, Sri Aurobindo Ashram, Pondicherry since 1968. He is one of the early workers in solar energy. Earlier he was with the Central Building Research Institute, Roorkee. He was a visiting scientist at CSIRO, Division of Building Research, Melbourne, Australia (/968 to 1 970). His research interests are in thermal physics applied to solar energy and science of buildings. He has been a member of the International Solar Energy Society since 1 969. Dr C L Gupta, Solar Energy Unit, Sri Aurobindo Ashram, Pondicherry 605002; Phone: 91 +413+346993, Fax: 91 +413 +334836, e-mail: sola([email protected]. in. saaric@ l.snl.net

Dr Arcot Ramachandran, Honorary Professor at National Institute of Advanced Studies, Bangalore and Chairman of Governing Council of Tata Energy Research Institute, New Delhi was born in 1923. He has a doctorate from Purdue University under the legendary Prof Jakob. He started the first pas-graduate course in thermal engineering at the Indian Institute of Science, Bangalore in 19505. He has been Director, liT, Chennai, and Director General, CSIR, New Delhi, and Under Secretary General of UN, heading UNCHS at Nairobi. He did pioneering research in heat transfer and renewable energy, and he is a Fellow of ASME, USA.

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