solar energy vol. 65, no. 4, pp. 237–249, 1999 1999 ... · in india, solar pond research dates...

Solar Energy Vol. 65, No. 4, pp. 237–249, 19991999 Elsevier Science Ltd

Pergamon PII: S0038 – 092X( 98 )00134 – 0 All rights reserved. Printed in Great Britain0038-092X/99/$ - see front matter

2CONSTRUCTION AND OPERATIONAL EXPERIENCE OF A 6000 m SOLARPOND AT KUTCH, INDIA

† ‡AMIT KUMAR and V. V. N. KISHORETata Energy Research Institute, Darbari Seth Block, Habitat Place, Lodhi Road, New Delhi 110003, India

Received 13 February 1998; revised version accepted 27 October 1998

Communicated by TY A. NEWELL

2Abstract—A 6000 m solar pond was constructed at Bhuj in India in the premises of a milk processing dairyplant to supply process heat and demonstrate the technical and economic viability of solar pond technology inthe Indian context. An inexpensive lining scheme, consisting of alternating layers of clay and LDPE (lowdensity polyethylene) combination was used for lining the pond. The pond attained a maximum temperature of99.88C under stagnation in May 1991 but developed leakage soon after. A failure analysis that was carried outsubsequently indicated that the leakage was caused by the combination of high stagnation temperature andlarge air pockets below the liner. The lining scheme was re-designed and the pond re-established in June 1993.Hot water supply to the dairy started in September 1993 and continued until April 1995. After an interruptionof nearly one year, hot water was resumed in August 1996. The total cost of construction of the Bhuj SolarPond was US$90 000 (1997 prices), including heat exchanger and piping etc., corresponding to a unit cost of

22US$15 m . 1999 Elsevier Science Ltd. All rights reserved.

1. INTRODUCTION Phase 4: Salt addition and renewal of hot watersupply (December 1995 to April 1997).

In India, solar pond research dates back to 1971.This paper describes in detail, the experience

Solar ponds were constructed in Bhavnagar, Pon-gained during construction and operation of the

dicherry, Bangalore and other places. But whileBhuj solar pond.

these ponds helped in demonstrating solar pondtechnology, they were not connected to any enduse (Kishore and Kumar, 1996). Keeping this in 2. PHASE 1: INITIAL CONSTRUCTION ANDview, in 1983, a proposal for National Solar Pond OPERATION OF PONDProgramme was submitted to the Ministry (then a

2.1. Site planning and excavationdepartment) of Non-conventional Energy Sources(MNES), and a feasibility study was carried out A barren tract of undulating land was available

2in 1985 for establishing a 5000 m salinity for construction of the solar pond within thegradient solar pond for supplying process heat to Kutch Dairy premises. These undulations necessi-a dairy. The construction of the pond with a tated a large degree of filling and embankment

2revised top surface area of 6000 m started in construction. Taking into account the land area1987 at Kutch Dairy, Bhuj, in the state of Gujarat available, the size of the solar pond was fixed at

2in western India as a collaborative effort between 6000 m (98 m 3 61.25 m). From the point ofGujarat Energy Development Agency (GEDA), view of structural stability, the side wall slopeTata Energy Research Institute (TERI) and Gu- was kept at 2:1 (Fynn and Short, 1983). Thejarat Dairy Development Corporation Ltd depth of the pond was 3.5 m initially, but was(GDDC). The project can be divided into four increased to 4 m later, so as to try a 1.5-m thickdistinct phases, as outlined below: gradient zone. Along with the solar pond, two

Phase 1: Initial construction and operation of smaller ponds with dimensions of 15 3 15 3 4 mpond (July 1987 to May 1991). and an evaporation pond of size 30 3 30 3 1 mPhase 2: Failure analysis (June 1991 to April were also planned. After the finalization of site1992). plans in July 1987, excavation work started. SincePhase 3: Re-establishment and hot water sup- the northeast portion of the pond area was at aply to dairy (May 1992 to April 1995). lower level as compared to the southwest portion,

a northeast embankment was constructed by†Author to whom correspondence should be addressed. Fax:preparing embankments of 10-m width at the191-11-4621770; e-mail: [email protected]

‡ ISES member. base. But since the civil contractor did not carry

237

238 A. Kumar and V. V. N. Kishore

out the compaction of soil properly, this embank- characteristics of clays and clay–soil mix arement failed in the first year and was repaired by shown in Table 1. Finally, the following liningirrigation and further compaction. The cost of scheme was decided:

23excavation worked out to be $2.2 m of pond 1. 75-mm thick, compacted layer of 3:1 mixturevolume (1987 prices). To provide an escape route of china clay and finely sieved soil.for any gaseous formations below the lining as 2. 250 m black LDPE film with in-situ, thermallywell as to monitor the seepage, a pipe network welded seam joints.made out of 75-mm diameter, perforated PVC 3. 100-mm thick, compacted layer of mixed claypipes was laid out at the bottom of the solar pond. as in (1) but divided into two layers so that the

extent of shrinkage cracks could be reduced.4. Brick lining only on the side slopes with joints

2.2. Lining of solar pond filled with 1:2 cement mortar.One of the main objectives of setting up the This lining scheme ensured that LDPE film was

Bhuj solar pond was to develop an indigenous and not exposed to radiation. Moreover, sandwichingcost-effective lining scheme based on locally LDPE film between clay layers made the liningavailable materials. The Beith Ha’ Arava solar insensitive to blow-holes and other minor defectspond in Israel employed a combination of clay in the film. The selected lining configuration was

2and polyethylene for lining but the technique first tried out in the 225 m ponds. Once sufficientbeing proprietary, exact details were not available. practical experience was gained in lining theSimilarly, the solar pond at Cuernavaca, Mexico smaller ponds, the lining of the solar pond waswas also lined with a clay–polyethylene combina- taken up. A mixture of pulverized clay, sievedtion but details were not available. Laboratory soil and water at OMC was prepared and then laidstudies had shown that clay could be a potential manually over the pond surface and compacted.lining material (Almanza et al., 1988). However, Since the efficacy of the clay lining dependsuse of clay-only lining might not be suitable for largely on the degree of compaction, the compac-the hostile environment of a solar pond because tion process was closely supervised. The slopesthe hot brine can cause some clays to flocculate, were compacted with the help of hand rammersmaking them more porous (Almanza and Cas- whereas the bottom was compacted in two stages.taneda, 1993). Experiments conducted in a liner In the first stage, a roller was used followed bytest rig (Raman and Kishore, 1990) showed that a manual ramming in the second stage. Clay liningplastic membrane, sandwiched between two layers was followed by LDPE lining where 9-m wideof compacted clay was very effective. While LDPE films were heat sealed in-situ and thenLDPE (low density polyethylene) was chosen as spread over the surface. One of the problemsthe membrane material, the choice of clay had to encountered was of improper sealing on accountbe made between bentonite and kaolinite (China of fine clay particles. A thin layer of clay particlesclay), both mined locally. However, since bento- would adhere to the plastic film, probably involv-nite was six times costlier than kaolinite and also, ing electrostatic attraction, and could not bemore prone to form cracks, the latter was selected. removed by wiping, rendering the thermal weld-

To test different lining configurations, experi- ing weak. Hence the LDPE film had to be cleanedments were conducted at the site where five test with the help of dilute acid before heat sealing.pits were made and lined differently (Motiani et Moreover, the residual air beneath the liner couldal., 1990). Pure kaolinite compacted at optimum not be removed completely. To compensate formoisture content (OMC), although desirable from the weak joints an additional, 100-m thick LDPEthe point of view of impermeability, poses two liner was introduced which was sealed at thepractical problems. First, when it dries, huge factory itself. Before putting this second liner inshrinkage cracks appear and second, wet clay is place, clay lining was covered with a 50-mm thickvery difficult to work with due to stickiness. To layer of compacted, sieved soil. The LDPE linerimprove the workability and also to minimize the too was covered with a 50-mm thick layer ofshrinkage cracks, it was decided to mix sieved coarsely screened soil. The complete details oflocal soil with the clay. Addition of sieved soil lining are given elsewhere (Motiani et al., 1990).minimized the formation of shrinkage cracks at A schematic of the final lining scheme is shown

22the cost of the permeability coefficient. By experi- in Fig. 1. The cost of lining was $8 m (1987menting with various proportions, an optimal ratio prices) of lined surface including the cost ofof clay and sieved soil was found to be 3:1. The material and labour.

2C

onstructionand

operationalexperience

ofa

6000m

solarpond

atK

utch,India

239

Table 1. Characteristics of clays and local soil

Particulars Grain size analysis Atterburg limits Classification Maximum Optimal Swelling Permeability

Gravel Sand Silt Clay Liquid Plastic Plasticity as per Indian dry density moisture index coefficient at21 21 2 6% % % % limit % limit % index standards (g ml ) content % % 278C (cm s 310 )

Kaolinite 0 04 48 48 48 26 22 CI 1.54 23 15 0.563Bentonite 0 01 13 86 317 62 255 CH 1.8 – 250 –Local soil 02 70 11 17 26 18 08 SC 2.0 10 10 –75% Kaolinite1 0 19 37 44 45 23 22 CI 1.67 17 – 0.6425% Sieved localsoil


Fig. 1. Lining scheme of the Bhuj solar pond.

2.3. Salt dissolution and gradient establishment system consisting of a mixing pond, settling tankand a sand bed filter, shown schematically in Fig.Preparing concentrated brine (salt dissolution)2 was constructed. The solar pond was first filledis usually a time consuming process. For example,

1 with water. The top layers of water were pumpedfive months were spent dissolving 1100 MT ofinto the mixing pond, salt was added, and thesalt required for the solar pond at UTEP, El Pasoconcentrated brine obtained after mixing was(Reid et al., 1983). Moreover, commercial gradepumped to the settling tank and to the sand bedsalt contains impurities, sufficient to render thefilter. After filtration and the addition of chemicalspond turbid. To overcome these problems, alike hydrochloric acid and copper sulphate foralgae control, brine was pumped to the bottom of

1 the solar pond through a diffuser. This processOne metric ton (MT)51000 kg.

Fig. 2. Salt dissolution system.

2Construction and operational experience of a 6000 m solar pond at Kutch, India 241

enabled dissolution of 3500 MT salt within two U]]]]]]and half months. This was probably the first time Fr 5 1 / 2(r 2 r )s ithat such an elaborate process of salt dissolution ]]]g.d.F Griand clarification was attempted in solar ponds.

Most solar ponds built hitherto established a21where U is injection velocity of fluid (m s ); glinear salinity gradient. However, since the

22is acceleration due to gravity (m s ); d isequilibrium salinity profile is nonlinear, in-diffuser slit /gap width (m); r is the density of thestabilities tend to develop during the changeover s

23from linear to equilibrium profile. Hence it was surrounding fluid (kg m ); and r is the densityi23decided to establish a nonlinear salinity gradient. of the injected fluid (kg m ). It has been rec-

The equilibrium profile was obtained by solving a ommended that for the mixing of two fluids toone-dimensional steady state mass transfer equa- occur at and above the diffuser level, Fr has to betion. For establishing a nonlinear gradient, the maintained at 18 (Liao, 1987). The mild steelmovement of the injection diffuser would no diffuser moved along a guide rail, driven by anlonger be linear, and has to be determined at each electric winch. A suitable gear arrangement en-step based on the remaining portion of the salinity sured slow and precise movements of the diffuser.profile. An algorithm was developed to calculate During the gradient establishment process, the slitthe diffuser movement. Appendix 1 gives the flow width of the diffuser was adjusted seven timeschart for calculating the trajectory of the diffuser, (slit width ranged from 4.5 mm to 18 mm), toalong with other parameters. The inputs were, (i) maintain the critical Froude number. While theequilibrium salinity values, (ii) geometry of the process of gradient establishment was in progress,pond, (iii) diffuser diameter, (iv) slit width of the it was observed that the actual profile had a shapediffuser and, (v) the Froude Number to be main- which intersected the desired profile at a par-tained during the injection of fresh water into the ticular point, as shown in Fig. 3. The samebrine. The Froude Number (Fr) is defined as: phenomenon had been noticed during gradient

Fig. 3. Density profile just after gradient establishment.


2establishment in the 225 m test pond at Bhuj as For a very clear pond, the transmittivity–ab-well as during establishing the gradient for a sorptivity product (ta), which is related to thesecond time during phase 3. A similar cross-over transmission of solar radiation in the pondwas reported for the UTEP pond also (Liao, (Kishore and Joshi, 1984), has a value of about1987). A close examination of all these profiles 0.45. In Bhuj pond, a sealed silicon cell sensorreveals that the cross-over was occurring at a was used to measure the transmission functionlevel between 180–190 cm in all the cases. This and a (ta) value of 0.434 was obtained during thesuggests that the Froude number should perhaps summer of 1991, which indicated very goodbe changed during gradient establishment rather levels of brine clarity.than kept at a single predetermined value. The To avoid gradient break down, it is essential tophenomenon, however, needs further investiga- ensure that there were no dynamic instabilities intion. NCZ. The margin of stability is a function,

Most large scale solar ponds used a central normally used to quantify the dynamic stabilityinjection diffuser, like UTEP (Reid et al., 1983) criterion (Hull et al., 1989). The pond is consid-and the Margherita di Savoia Pond (Folchitto, ered to be stable as long as the margin of stability1990). In the Bhuj solar pond, measuring 100360 is more than two. The margin of stability for them, the diffuser was installed at the middle of one Bhuj pond near the NCZ–LCZ interface is shownof the 60-m sides. The other end of the pond was in Fig. 4 and had not gone below two even at a100 m away from the diffuser. Measurements on high temperature of 998C.the farthest end showed that there was no change One of the crucial components of solar pondin the profile (Motiani et. al., 1993). This kind of maintenance is the control of wind-induced distur-diffuser positioning simplified the piping and bances. Bhuj is a windy area having an annual

21other infrastructural requirements. It took 173 wind speed of more than 3.6 m s and largehours to establish the gradient. waves did develop during salt dissolution. The

Bhavnagar pond in India used square as well as2.4. Control of clarity and wind disturbances, circular rings, made out of PVC conduit pipes andheating up and liner failure joined together (Mehta et al., 1987) to form a

Brine transparency is one of the most crucial wave suppression device. Still the thickness offactors as far as thermal efficiency of solar ponds UCZ remained very high there throughout theis concerned. Wind borne debris such as dirt, dust operation period. At the UTEP solar pond, a waveand leaves etc., floating on the pond surface does suppression system made of polyethylene tubingsnot always sink to the bottom but sometimes was used but was found to be ineffective in highremains suspended at a particular level in the winds (Reid et al., 1983). Later on, this systempond. Bhuj pond had to face a peculiar problem of was replaced with another system which consistedplastic milk pouches which were being regularly of polymer foam nets, tied between ropes. Thesediscarded by the dairy, scattered all over the pond nets were especially developed in Israel for wavesurface due to high winds. These had to be suppression (Reid et al., 1983). Importing the netsskimmed out at regular intervals. Alum was used from Israel was considered initially but the quotedto facilitate flocculation of suspended particles. prices were too high to be accommodated within

2For algae control, initially bleaching powder and the project budget. Experiments in the 225 m testliquid chlorine were tried but these were found to pond showed that HDPE nets, manufactured by anbe ineffective. Thereafter a combination of hydro- Indian company, were adequate. Moreover, thesechloric acid and copper sulphate was used to get nets were 1/3 the cost of the imported nets. Apartthe desired clarity. The process involved prepar- from being very effective even during peak winding a solution of copper sulphate in dilute hydro- speeds, the nets showed no degradation after sixchloric acid (commercial grade) and injecting this years of use.at the level where algae had grown. The injections The history of temperature gain during phase 1were done through a small diffuser with 2-mm slit is shown in Fig. 5. The pond attained a maximumwidth. It was observed that copper sulphate was temperature of over 998C in May 1991 as heatmore effective if the brine is acidic, and more- extraction could not begin in time on account of aover, by making the brine acidic, further growth delay in procurement of the heat exchanger. Soof algae was suppressed. During one year opera- far, the pond was in good condition. But on Maytion, quantities of chemicals added were as fol- 18, 1991 a routine monitoring indicated a 5-cmlows: alum – 595 kg, hydrochloric acid – 550 l drop of pond level, which was well above theand copper sulphate – 47 kg. evaporation losses. Monitoring of salinity profiles


Fig. 4. History of stability margin for the Bhuj solar pond.

confirmed that the level drop in the pond was leakage was probably from the bottom. Theabout 5 cm. When the venting system at the leakage spots were located and mapped by pump-bottom of the pond was evacuated, hot and ing compressed air through the venting systemsaturated brine came out, indicating that the and finding the points from where air bubbles

Fig. 5. History of LCZ temperatures (phase 1).


were coming out. An attempt was made to plug 4. While a major portion of the vent pipe gridthe leaks by dumping powdered china clay over was in good condition, some pipe length wasthem (Motiani et al., 1993). While this exercise completely distorted. The distortion was obvi-resulted in bringing down the rate of level drop ously due to the entry of very hot brine into thefrom 5 cm to 1 cm per day, the seepage could not PVC vent pipes. Just above this distortedbe stopped altogether. Hence it was decided to portion, three through and through holes ofempty the pond, remove the lining and sys- about 15 cm diameter were observed throughtematically analyze the cause of failure. the clay layers.

These observations suggested that the liningfailure was most probably due to the formation ofair pockets below the lining. The air present in the

3. PHASE 2: FAILURE ANALYSISshrinkage cracks and vent pipes could have

The clay removed from the pond was sent for formed confined and pressurized air spaces. Theselaboratory testing to ascertain whether it had could have initially caused leaks in a few places,changed, either physically or chemically, com- allowing hot brine to enter the vent pipes thuspared to the virgin clay. The test results, given in blocking air escape in a portion of the vent pipeTable 2 showed that there were no significant grid. With the escape route of air thus blocked, thechanges in the properties of the clay after usage in air would get heated up and pressurized. If the airthe solar pond. Almanza et al. (1987) also pocket was originally at brine column pressure ofreported that there were no significant variations about 1.4 atm, at 258C, the air pressure at brinein properties like liquid limit, plasticity index, and temperature of about 808C would be 1.43(2731

vertical permeability of clays before and after use 80) /(273130)51.63 atm. The pressure on thein solar ponds. Measurements made at the site other side of the lining scheme, corresponding toindicated a vertical permeability coefficient of a brine column of 3.5 m, would be about 1.4 atm.

27 21 27 222.52310 cm s before use and 3.01310 Thus a differential of 0.23 atm (0.2376 kg cm )21cm s after use. It can thus be concluded that the would exist across the lining layers, causing a

problem was not due to any changes in clay. significant local upward force if the area of theMeanwhile, details of the lining along with the spread of air pocket is large, sufficient to rupturehistory of Bhuj pond were sent to Professor the clay layer as it has a very low tensile strength.Zaslavsky, who developed the lining schemes for The tensile strength of LDPE at elevated tempera-several Israeli ponds, for his comments. While he tures would also be small and hence the completevalidated the lining scheme adopted for the Bhuj lining scheme was susceptible for ruptures underpond, he could not spend more time on analysis of upward forces.the cause of leakage. The following observationswere made while dismantling the lining:1. The 250-m LDPE film had degraded somewhat

4. PHASE 3: RE-ESTABLISHMENT AND HOTalthough it was buried completely. The tearWATER SUPPLY TO DAIRYresistance of the film was reduced and, cracks

and brittleness were observed along some Considering that the most probable cause offolds. leakage was the presence of air pockets, it was

2. The heat-sealed joints were intact, except for a decided to remove the vent pipe grid to avoid anyfew joints. kind of air pockets. Also, to avoid folds and air

3. The clay layer below the LDPE film had spaces below the film, it was decided that LDPEdeveloped small shrinkage cracks. films would not be heat sealed but overlapped

Table 2. Comparison of various properties of clay before and after exposure to solar pond conditions

Property Before After (clay above 250m film)

Chemical composition (%)SiO 57.92 58.692

AI O 29.11 29.952 3

CaO 2.17 1.78MgO 0.65 0.44Fe O 0.40 0.302 3

Cl 0.66 1.56


while laying down. While the overlapping will establishment was completed in 115 h wherein 5.9allow some percolation, the clay layers will million litres of water was injected. The slit widthremain wet thus reducing shrinkage cracks and air of the diffuser was changed eight times. Thepockets. Further, based on the opinion of polymer increased thickness of clay layer necessitated ascientists that black pigmentation in polyethylene reduction in the storage zone depth to 1.0 m.accelerates thermal degradation, it was decided to The pond started heating up from June 1993use colourless film as it has fewer oxidation sites. and achieved a storage zone temperature of 808CIt was further decided to use a combination of by August 1993. Meanwhile the heat exchangerlinear low density polyethylene (LLDPE) with was designed, procured and installed at the siteLDPE. The improved lining scheme for re-lining and pipe line laid for transporting hot water to thethe pond bottom had the following features: dairy plant which was 175 m away from the pond.1. Vent pipe grid below the lining was removed.

4.3. Supply of hot water to the dairy2. Polyethylene film did not have any additives.3. Composition of polymer changed from 100% Heat extraction from the solar pond can be

LDPE to a combination of 50% LDPE150% carried out in two ways. The first method uses aLLDPE. submerged heat exchanger in the pond, as was the

4. Plastic membrane liners were not heat sealed case for the Bhavnagar and Bangalore ponds. Inbut just overlapped. the second method, brine is pumped from the

5. Total clay thickness increased to 90 cm (three lower convective zone (LCZ), to an external heatlayers of 30 cm thickness). exchanger and returned to the pond. The mainThe relining was undertaken at the bottom of advantage of having an external heat exchanger is

the pond only, without disturbing the side walls. that the overall heat transfer coefficient is muchThe new plastic liner was heat sealed to the old higher and hence the heat exchanger can be veryLDPE liner around the periphery of pond bottom. compact. Also, the maintenance of an external

heat exchanger is much easier than that of a4.1. Installation of revised lining scheme submerged one. The brine extraction system

The first 30-cm clay layer was subdivided into consisted of brine suction and discharge diffusers,three layers of 10 cm each, to obtain better brine pump and associated piping. It is verycompaction. After completion of the first 30-cm crucial that the brine circulation rate and theclay layer, laying of the first plastic film was location of the suction diffuser with respect to thestarted along with simultaneous laying of the lower interface must be selected carefully in suchsecond clay layer. The process consisted of laying a manner that withdrawal and re-injection of brinethe plastic film and covering it with a 10-cm clay does not disturb the salinity gradient. The suctionlayer. The second strip of film was then laid diffuser was kept at a level of 20 cm below theadjacent to the previous strip in such a manner LCZ–NCZ interface. The discharge diffuser-that a 50-cm overlapping was obtained. The same carrying cooler, return stream was placed 20 cmprocedure was repeated for the second plastic below the suction diffuser. Diffuser design andlayer and third clay lining. Care was taken to brine flow rate will be dependent on the Bulkensure that overlapped joints of the first and Richardson Number and Local Richardson Num-second plastic lining were staggered. ber. According to Zangrando, the values of Bulk

Richardson and Local Richardson numbers should94.2. Salt dissolution and gradient establishment be around 10 and 500, respectively, in order to

While it took more than two months for salt avoid the disturbance of gradient (Reid et al.,dissolution in phase 1, it was decided to accom- 1983). Based on these limiting numbers and someplish this task within a month by improving the trial runs carried out directly on the pond, a brine

3 21agitator design. Accordingly, the impeller was flow rate of 70 m h and water flow-rate of 83 21modified and enlarged. It took less than a month m h were selected for heat exchanger design.

to dissolve 3200 MT of salt. Some additional salt Both, suction and discharge diffusers were placedwas dumped directly in the pond to take care of on the same side of the pond but separated by apossible future salt depletion. horizontal distance of 3 m.

The gradient-establishing set up was the same Since fouling of the heat exchanger is a majoras that in phase 1. However, the capacity of the problem with saturated brine, it was decided topump was increased, and the diameter of diffuser adopt a shell and tube type design. Brine was onwas increased from 30 to 50 cm. The gradient the tube side and water on the shell side. The


Fig. 6. History of LCZ temperatures and hot water supply.

tubes were made of cupro-nickel whereas the ernment to re-vitalize the National Solar Pondmaterial for the shell was carbon steel. The heat Programme which involved a few more demon-

2transfer area was 36.1 m for a heat duty of 396.5 stration ponds and extend the technology to other21kW (341000 kcal h ). applications such as desalination. The Bhuj solarth

Fig. 6 shows the history of LCZ temperatures pond was dedicated to the nation in May 1994 byand hot water supply. Heat extraction commenced the then Union Minister of State for Non-conven-in September 1993 and was continued till April tional Energy Sources.

31995. A total of over 15 000 m of hot water wassupplied to the dairy at an average temperature of758C. The design capacity of the pond is to supply

5. PHASE 4: SALT ADDITION AND RENEWAL380 m of hot water per day at 708C (3720 kW ).th OF HOT WATER SUPPLYThe average daily demand of the dairy was about

325 m per day which is about 31% of the pond The solar pond was expected to be maintainedcapacity. As a practice, the heat extraction was by the GDDC. Maintenance included daily opera-carried out as per the design capacity and the tion of pumps, weekly monitoring of tempera-surplus hot water was discharged over the pond tures, density and levels, regular injection ofsurface itself. The full capacity heat extraction did chemicals for clarity control and yearly additionnot result into a noticeable temperature drop. A of salt. However, GDDC went into the red inrough calculation showed that the dairy can save 1994, and the operation of the dairy suffered a set935 MT of lignite per year with continued use of back, resulting in a poor maintenance of the solarthe solar pond at its full capacity. This amounted pond. Subsequently, MNES agreed to give a one-to a monetary savings of Rs.700 000 ($19,444) time maintenance grant in 1995. With the help ofper year. The simple payback period is estimated this grant, fresh salt addition was made and theto be less than 5 years without any subsidy or tax gradient was established again in June 1996. Hotincentives. Considering that this was the first large water supply was resumed at the end of Julyscale pond to be used in an industrial environment 1996. The temperatures of LCZ during this phasein India, the economic viability appears to be are shown in Fig. 6. After a comprehensivequite strong. Further improvements, especially on training to the GDDC employees on the mainte-the lining method are expected to bring down the nance aspects, the solar pond was handed over tocosts. A recommendation was made to the gov- the dairy in April 1997. Fig. 7 depicts a


Fig. 7. A panoramic view of the Bhuj solar pond.

panoramic view of the Bhuj solar pond with the imperative to construct ponds with varied liningheat extraction system in the foreground. configurations and materials until adequate confi-

dence is achieved in cost effective containment ofhot brine. Efforts are also required to minimize

6. CONCLUSIONSand standardize the operation and maintenance of

The successful operation of Bhuj solar pond solar pond. It also appears that solar ponds can behas set a stage where a beginning could be made gainfully employed for applications like desalina-for commercial exploitation of solar pond technol- tion, refrigeration, drying, bromine recovery fromogy. The simple payback period works out to less sea water, manufacture of magnesium chloridethan five years (without considering any subsidy etc. A comprehensive programme consisting ofor incentives), which is reasonable for an upcom- further demonstration and application oriented Ring renewable energy technology. While the Bhuj and D thus seems to be highly desirable.solar pond project contributed a great deal to-wards the development and perfection of thetechnology, some more developmental work still Acknowledgements—Several people contributed to this project

and space is too short to name all of them individually.needs to be carried out, the most important beingHowever, the support and contribution of some individuals

the standardization of a foolproof brine contain- and organizations merits special mention. The late Dr. K.S.ment scheme. The fact that the Bhuj pond could Rao, former Director of GEDA, was the chief architect of the

National Solar Pond Programme, and the establishment of thesupply process heat for about two and half yearsBhuj solar pond was a result of it. Several officials of MNES

is proof enough about the adequacy of the lining provided enthusiastic support. Dr. R.K. Pachauri, Director,scheme used. However it cannot be termed as the TERI, was a source of constant encouragement and support

throughout the project. The contribution of Mr. M.D. Motianibest choice especially because LDPE and LDPE-and other team members is sincerely acknowledged. Several

variants are not meant for high temperature other researchers of TERI made specific contributions. Theservices. Moreover, the viability of such lining support provided by GEDA and GDDC deserves to be

specifically acknowledged. In fact, this project set out andepends on soil and clay characteristics. So farexample of a very meaningful and successful collaboration

this lining scheme has been tried for only one site between a user, a research institute, state nodal agency and aand is not proven for other sites. Therefore it is central ministry.


APPENDIX: FLOW CHART OF THE GRADIENT ESTABLISHMENT PROGRAMME


Kishore V. V. N. and Kumar A. (1996) Solar pond: an exerciseREFERENCESin development of indigenous technology at Kutch, India.Energy for Sustainable Development, Vol III (1), 18.

Liao Y. (1987) Gradient stability and injection analysis for theAlmanza R., Munoz F., Segura G. and Martinez A. (1987)El Paso solar pond. MS Thesis, p. 36. University of Texas atStudy of CH-type clays as liners for solar pond. InEl Paso.Proceedings of International Conference on Solar Ponds,

Mehta A. S. et al. (1987) Five year operating experience onCuernavaca, Mexico.bittern based solar pond. In Proceedings of InternationalAlmanza R., Martinez A. and Segura R. (1988) Study of aConference on Solar Ponds, p. 143, Cuernavaca, Mexico.kaolinite clay as a liner for solar ponds. Solar Energy 42,

Motiani M., Kumar A., Kishore V. V. N. and Rao K. S. (1990)395.2Constructional details of 6000 m solar pond at KutchAlmanza R. and Castaneda R. (1993) How to test a liner clay

Dairy, Bhuj. In Proceedings of 2nd International Confer-for solar ponds. In Proceedings of 3rd International Confer-ence on Solar Ponds, p. 239, Rome.ence on Solar Ponds, p. 6, El Paso, USA.

Motiani M. D., Kumar A., Kishore V. V. N. and Rao K. S.Folchitto F. (1990) Margherita Di Savoia Solar Pond. In2(1993) One year performance of the 6000 m solar pond atProceedings of 2nd International Conference on Solar

Bhuj. In Proceedings of 3rd International Conference onPonds, p. 25, Rome, Italy.Progress in Solar Ponds, p. 38, El Paso, USA.Fynn R. P. and Short T. H. (1983) Solar Ponds – A Basic

Manual. p. 12. Special Circular No 106, The Ohio State Raman P. and Kishore V. V. N. (1990) An alternate liningUniversity, Wooster, Ohio. scheme for solar ponds – results of a liner test rig. Solar

Energy 45, 193.Hull J. R., Nielsen C. E. and Golding P. (1989) SalinityGradient Solar Ponds, p. 57. CRC Press, Inc., Florida. Reid R. L. et al. (July 1983–Sep 1985; 3rd and 4th: 1984;

Kishore V. V. N. and Joshi V. (1984) A practical collector Final: 1985; Jan–Mar and April 1986; July–Sept 1986) Elefficiency equation for non-convective solar ponds. Solar Paso Solar Pond Test Project. Quarterly Reports, UniversityEnergy 33, 391. of Texas at El Paso, USA.

solar energy vol. 65, no. 4, pp. 237–249, 1999 1999 ... · in india, solar pond research dates...

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