Economic evaluation of a tunnel type solar dryer

Arut. Btutgladesh Agric. (2008) _{12( I ):} I l9-130 ^{ISSN IO25-482X}

ECONOMIC EVALUATION

OF A

TUNNEL

TYPE SOLAR DRYER

M A

Rahman',

A T M'ZiaUddin

and ^S

M I

Hossain2

Dept. of Farm Power and Machinery, Bangladesh Agricultural University, Mymensingh-2202.

B angladesh, ^I Bangladesh Sugarcane Research Institute, Ishurdi, Pabna, Bangladesh, 2Department of Agricultural Engineering, Bangabandhu Sheikh Mujibur Rahman

Agricultural University, Gazipu r - I7 06, B angl adesh

Abstract

A

runnel type solar dryer was fabricated

in

the farmyard

of

^Bangladesh

Agricultural University, Mymensingh

in

2000. The study was ^{conducted to} evaluate the economic performance

of

tunnel type solar dryer and that of traditional sun drying for fish, vegetable and fruits. Data used in this study was collected from experiment and literature. The market values of the raw materials and their products used were considered for cost analysis. Annual operattng cost

of tunnel type solar dryer was found Tk.19,773.32 and that of traditional sun

drying was Tk.13,593.60. Annual drying loss

for

tunnel dryer was ^found Tk.1661.00 only whereas annual drying loss for traditional sun drying was found Tk.49555.80. The Expected Net Present Value (ENPV,) of cost of tunnel dryer with drying ^losses was Tk.205240.80 but ^ENPV5

of

cost

of

sun drying with losses was Tk.493,429.93. So a significant amount of money can be saved every year by using tunnel type solar dryer.

Keywords.' Economic evaluation, Tunnel, Solar dryer, ENPV

Introduction

Tunnel type solar dryer

is

an improved method

of

drying system. Solar drying can be considered as an elaboration

of

sun drying and an efficient system

of

utilization of solar energy

for

drying

of

agricultufal products such as

fruits,

vegetables, fishes and ^grain crops

(Bala

L997 and Muhlbauer 1986). Sun

drying

does

the

traditional

drying

of agricultural products. Although ^sun drying offers the cheapest method,

it

often results in

inferior

quality due

to its

dependence

on

weather conditions and vulnerability

to

^the

attack of insects, pests, microorganisms and dust.

Every year the country ^{losses a} substantial amount of agricultural products due to lack

of

proper preservation and processing

of

products during and after harvesting of crops. Tunnel type solar dryer ^can help preserve seasonal agricultural products by drying with solar energy maintaining the quantity of the products . Large scale drying is not only an energy consuming process

but

also

a

process

for

producing products

of

required quality where the qualities

of

dried products do have an effect to economy.

It

can also maintain natural quality of products.

M A Rahman, A T MZiaUddin and S M I Hossain

All the

areas

of

Bangladesh

receive

abundant

solar radiation and it

^is

environmentally sound.

It

has been justified _that artificial solar dryers have the potential

for

adoption and application

in

Bangladesh

for

drying

of

agricultural products (Bala L997). The tunnel type solar dryer has been proved technically feasible and potential for adoption

in

Bangladesh

(Bala 1997). But it

has not yet been

justified for

economic performance

in

Bangladesh. Therefore the objective

of

the study was

to

evaluate the economic performance and potential of the tunnel type solar dryer in Bangladesh.

Materials and Methods Solar Tunnel Dryer

The tunnel type solar dryer essentially consist

of a flat

plate

air

heating collector, a

tunnel-drying unit and a small fan to provide the required airflow over the product to be

dried. These are connected

in

series.

A

schematic view of a tunnel type solar dryer with its functional components is shown in the Fig. 1. The dryer was considered to be used for the year round drying

of

agricultural products. Fruits, vegetables and fishes were the operating raw materials of this study. The perfoffnance of the dryer was evaluated on the basis of cost analysis.

Fig. 1. A schematic view of a tunnel type solar dryer: 1. Air inlet, 2. Fan, 3. Solar module, 4. Solar collector, 5. Side metal frame, 6. Outlet of the collector, 7. Wooden support, 8. Plastic net, 9. Roof structure for supporting the foil, 10. Base structure for supporting the tunnel dryer, 11. Rolling bar, 12. Outlet of the dryng tunnel.

Cost Analysis

Fixed and variable costs of the tunnel type solar dryer were determined for the economic performance

of

tunnel type solar dryer and sun drying. Depreciation and interest were included in fixed cost but taxes,'housing and insurance were not considered because these

120

Economic evaluation of ^a tunnel type solar dryer

parameters were

not

applicable to. tunnel type solar dryer

in

Bangladesh condition.

Depreciation cost was calculated by using the straight line method ^as follows:

p _{_s}

D-^ ---(1)

L

where, D = Depreciation ^cost, Tk.

P = Purchase/construction ^cost of tunnel dryer, Tk.

S = ^Salvage value, Tk.

L

= Economic life of the dryer, yr

Interest in a particular year of operation for a dryer was estimated by using the following formula.

1=If

^*,

-

^{P+0' lP*i}

=0.55pi ---<2) 22

where,

I

= Total interest, Tk./yr

i

= Interest rate, decimal

Assumin g l\Vo salvage value of ^purchase price (S = 0.1P), estimated economic length

of

life in years

L

₌ ¹² and interest

i

_=107o (Rahman 2000).

The total fixed cost (annual)

-

Depreciation + Interest.

FC

=D+ I= P-s *

^P+S

xi

=

P-0'lP

* P+9'lP x0.1=0.13P----(3) L2t22

Variable cost of the tunnel dryer includes (i) repair and maintenance cost and

(ii)

labour cost.

Repair

&

maintenance cost was determined by using the following equation.

where, RM=Repatr

&

maintenance cost Tk./yr

Pr = Plastic

foil

^cost, Tk./yr

Nl=

No. of labour required per ^day to change and fitting the plastic

foil

Cr= Cost of labour per day, Tk./ labour/ day

U= Requirements of time for repair and maintenance, day/yr

The cost of labour for tunnel dryer was determined by using the following equation.

LC,,,,,,.r =

iW., xI' xQ"

----(5)

i=l lti

where, LCt*r*"I = Labour ^cost for tunnel dryer, Tk./yr

Wu

-

Labour required per batch for drying of ^crop9, i by tunnel dryer, labour/batch Tti= Total drying time crop

i,

daylyr

Kr= Utilization factor.of dryer

M A Rahqnan, A T M ZialJddinand S M I Hossain Cr,t= Cost of labour per day, Tk./labour/day

Tu= Drying time per batch for crop

i ,

^daylbatch

The variable cost of tunnel dryer = Repair

&

maintenance cost + labour cost.

VC=RM+LC,unn"r --(6)

Lobour cost of sun drying was determined by using the following equation.

=i

^t,i

where, LCrun = Labour ^cost for drying Tk./yr

Wr1= Labour required per batch for drying of crops i by sun drying, labour/ batch Tsi = Total drying time for crop

i

day/yr

Ksi = Utilization factor of dryer

Crrr = Cost of labour per ^day, Tk./labour/ day Tsi = Drying time per batch for crop

i,

day/batch Determination of

Drying

Losses

Drying losses

of

the products to be drjed

or of

dried products may'be quantitative or qualitative and may occur separately or together.

Quantitative drying ^loss of tunnel dryer was calculated by using the following equation.

, -'"

tquantity

-ZY,,xFrixP,,*- -(8)

i=1

where, lquantity

-

_Quantity ^loss of dried product by tunnel dryer, Tk./yr Yti = Drying ^rate or capacity of the tunnel dryer, kg.lyr Rr= Loss factor

Ri = Unit price of wet product of crop i, Tk.lkg

a

I i

' ii

Again drying rate or capacity

of

the tunnel dryer was calculated by using the

following

;

equation.

ⁱ

\,

_Yti

=

^{S,i XA,, xT,, XK,i}

--:-- *(9)

t,,

where, Ati = Effective drying ^area of tunnel dryer,

m2

^,

Sti = Amount of sample per batch per

m'

area, kglbatch/m2 Tr = Total drying time of crop i per season, daytyr

Kti

₌ Utilization factor of dryer

tti = Drying time per ^batch for crop i, day/batch

Assuming that the entire dried product, dried by tunnel dryer was of good quality. So the qualitative loss of dried product by tunnel dryer was neglected.

122

Economic evaluation of a tunnel type solar dryer

The quantitative loss

of

products, dried by sun drying was determined using the ^above same equation and quality loss of the ^same product was calculated by using ^the following equation.

, -t"

rquarity

-LP;,(P,,-P,r) --(10)

i=l

where, ^lquality = Qualitative ^loss of product by sun drying

Poi = Amount of dried product of crop i, kg/kg

Ri = Unit price of product for same quality as dried by tunnel dryer, Tk./kg

Psi = Unit price of the product as dried by the sun drying, Tk./kg Total drying loss of sun drying

-

Quantity ^loss + Quality ^loss.

or 1,. =

lq.,on,i,y

+lquority ---(11)

Artrtuul C ^{ost C} alculation

The annual cost for both the tunnel dryer and sun drying were calculated by using ^the following equation.

Annual cost = Fixed cost + Variable ^cost + Total drying loss.

or AC=FC+VC+1"--

^--(12)

To evaluate the economic performance of the tunnel type solar dryer, the annual cost was converted into the Expected Net ^Present Value (ENPV) of cost, which was calculated by the following equation (Gutting 1994).

..ll-. AC

ENPY

=P+

> ,

_--r=

^-(13)

? (l+

^r)"

where, ENPVT = Expected Net ^Present Value of cost for tunnel dryer, Tk.

P = ^Purchase price of the tunnel dryer, Tk.

AC _{= Annual} cost of the tunnel dryer, Tk.

r = Interest rate, decimal n = No. of ^years.

The

Expected

Net

Present

Value

(ENPVT)

of cost of traditional sun drying

was determined by using the following equation.

ENpv, =i ? ++ (r+ r)" --(r4)

where, ENPVs = Expected Net ^Present Value of cost for sun drying, Tk.

M A Rahman; A T M Zia Uddin and S M I Hossain

AC _{= Annual} cost of the drying, Tk.

r = Interest ^rate, decimal n = No. of ^years.

Results and Discussions

Drying Cost of the Tunnel Dryer

Fixed Cost: Annual fixed cost of tunnel dryer was found

Tk.

756L 32 using the equation (3) where the construction cost of the dryer was Tk. 58,164.00. A breakup of the total cost of the dryer is shown in the following Table 1.

Table l. Construction Cost of Solar Tunnel Drier at BAU, Mymensingh

i

II

{

fit f;r

Items with Specification Unit Price

Sl. No

I

2 J 4 5 6 7 8

I

l0

ll

t2 l3 t4 l5 l6 t7 l8 t9 20 2l

22 23 24

887 kg I no.

2 nos.

50 kg 20lb.

160 16 nos.

4 cft.

40 ft.

35 kg 165 kg 66 ft. x 3ft.

3 gross 4 gross

l8 gross 2 gross

4lb.

4lb.

2 liter l0 nos.

250 gm 250 em 3 nos.

23949.00 14500.00 1500.00 1400.00 700.00 400.00 r600.00 2200.00 840.00 73s .00 3300 .00 t254.00

2t6.00 208 .00 432.00 60.00 220.00 260.00 80.00 100.00 10.00 10.00 90.00 4100.00 TotalCost (TK.) M/S sheet (18 _Gauge)

PV Module (12V,40W) D.C fan (6 in. l2V)

Glass wool

Plastic foil (0.2mm thickness) Rubber rope (0.25in. _{Q )}

Aluminum U-channel ( I 2ft.x0.25in) Timber

G.I. pipe (3/a in. _Q) M/S rod (2/8 in. _Q) Angle bar (l.5in.x l.5in) Wire rnesh (0.25in.x0.25in.) Rivet pin (2mm-Q) Cot screw (ll?in0)

Screw (3l4in.) Scrqrv ⁽ lin.) Aluminum paint Black paint Turpentine oil Drill bit Iron pin (l.5in.) Wire (Fastening) Grinding carbon

Cutting, bending & fitting

27 Tk.lkg 14500 Tk.&g 750 Tk./Pc 28 Tk/kg 35 Tk./tb.

2.50Tk.lft 100 Tk/Pc 550 Tk/cft 2lTktft 2tTktkg 20 Tk/kg

t9 Tk/fr 72 Tk/Gross 52 Tk.lGross 24 Tk./Gross 30 Tk./Gross 55 Tk./tb 65 Tk./lb 40 Tk./Liter

10 Tk./Pc 40 Tk./kg, 40 Tk.lkg 30 Tk./Pc

I tl

i

1

l

I

I

I

t

I

124

Grand Total = Tk. 58,164.00 voriable cost: It includes the repair & maintenance cost and labour cost

Economic evaluation of a tunnel type solar dryer

Repair and

Maintenance

(R & M) Cost: Repair and

maintenance

cost

^includes

maintenance as well as the cost of parts, which need to be changed or replaced, and the skilled labour cost to replace ^the parts. For tunnel type solar dryer 0.02 mm thick plastic

foil

was changed every year ^as

well

as after every three alternative years, painting ^cost was also added to

it,

which increases the repair and maintenance cost. The annual repair

&

maintenance

(R&M)

cost

of

the tunnel dryer was found

Tk

820.00 per year using equation (4) where pr =Tk.700/yr,, NL

= 2,

Cy= Tk.60.00/ labour and

U =l

^{daylyr were}

assumed (Rahman, 2000).

lnbour

Cost: Number of labourer as well as labour cost required to dry the various ^types of fruits, fishes and vegetables in the tunnel dryer depends on the following factors:

1)

Performance and skill of the labour,

2)

Drying time ^{per batch} ,

3)

Total drying time per season,

4)

Utilization factor of the dryer.

Labour cost was calculated from the equation (5) as shown in the Table ^2.

Table 2. Calculation of labour cost for drying products by tunnel dryer Item (i) Drying

time/batch for crop i, (t,i) day/batch

Labour required/

batch for crop i, (w,) nos.

Total drying time for crop i, (T,i) daylyr

Utilization factor for dryer (k,;)

cost of labour (Cr,i) TWdaylyr

Labour cost for dryer Tk./yr

t 2 ^aJ 4 5 6 7=(3)(4)(s)(6)t(2)

Cabba-ee 1.5 2.A 58 0.8 60.0

³¹¹²

Man-qo 3.0 3.0 22 0.8 60.0

¹⁰⁵⁶

Pineapple 3.0 3.0 47 0.8 60.0

²²⁵⁶

Fish 5.0 5.0 9t 0.8 60.0

⁴³⁶⁴

Total labour cost Tk. ll392lyr.

From equation (6) variable cost was calculated as Tk.l22l2lyr.

Drying Loss of Tunnel Dryer

Quantitative ^loss of tunnel dryer: Quantitative ^loss of tunnel dryer ^as obtained from experimental data was determined from equation (8) and shown in Table 3.

'

M A Rahman,"A TMZiaUddin and S

MI

Hossain

Table 3. Quantitative ^loss of ^the products from tunnel dryer

Itenr (i) Amount of

sample (S,i) kB lbatch/

m2,

Eft'ective drying area (A,i) m2

Drying time/bat ch lbr crop i (T,i) day.

Total drying time for crop i (Tti) daylyr

Utiliz ation factor for dryer (Kr)

Drying rate capacity, (T,r) ke/yr

Loss factor for crop l, (fr)

Unit price of crop i, (Pti) Tk /ke

Total loss, Tk. /yr

I 2 ^a., 4 5 6 7 8 9 l0

Cabbage Mango Pineapple Fish

5.5 6.0 6.0 7.0

r.5 3.0 3.0 5.0

s8 22 47

9l

0.8 0.8 0.8 0.8

0.01 0.01 0.01 0.0r

5 35

l5

50 3403

704 r504 2038 20

20 2A 20

170. l 5

246.t5 225.40 1019.00 Total quantitative loss of tunnel dryer, I qu,,rrtity = ^{Tk.L 66 I .321} Yr

Annual Cost Jbr ^Tunnel Dryer

The total annual cost (Drying cost + drying loss) for tunnel dryer was determined as Tk.

21,434.32by using the equation (12). The effective working

life

of the tunnel solar dryer was assumed 12 years (Rahman, 2000). The total annual costs

for

the effective working

life of

the tunnel solar dryer (12

years)

were converted

into

the Expected Net Present Value of cost (ENPVI), which was found to be Tk205,240.80 by using equation (13) are shown in the following cash flow diagram (Fig. 2).

Year

Pr = 700

ljrg. J. ('ush {'low diagranr frtr tuntrel solar dryer.

1'2b

AC

I,

Tk.

V _{= Tk. 205240.80}

= Tk. 58164

ENPVT

Economic evaluation of a tunnel type solar dryer Drying Cost

for

Traditional Sun Drying

Fixed Cost: Traditional sun drying does not require capital cost, but needs only open space. Therefore, no fixed cost was considered for using of open space for dryer

Variable Cost:

In

the variable cost, only labour cost was considered

for

traditional sun

drying and necessary data were obtained from market price during this study ^(Rahman 2000).

Labour cost for traditional sun drying was calculated using equation (7) ^{as shown} in Table 4. Total drying time, utilization factor and cost of labour were considered ^same

as of tunnel dryer.

Table 4. Calculation of labour cost for traditional sun drying

Item (i) _Drying required/bat ch fbr crop i, (Tri) dayi batch

Labour required/ba tch fir crop i, (W,) nos

Total drying time for crop i, (Ts) daylyr

Utilization factor for dryer (K,i)

Cost of labour (Cr'i)

Tk./day/lab

Labour cost for dryer Tk./yr

I 2 _J- _{4 5 6} 7=(3X4XsX6y(

2)

Cabbage 2.5 3.0 58 0.8 60.0

3340.8

Mango 5.0 7.0 22 0.8 60.0

^1478.4

Pineapple 5.0 7.0 47 0.8 60.0

^3158.4

Fish 7.0 9.0 91 0.8 60.0

^5616.0

Total labour cost = Tk.L3,593lyr

Drying ^Losses

for

Traditional Sun Drying

Quantitative ^as well ^as qualitative losses are also involved in drying _I losses for traditional sun drying.

Quantitative loss: Quantitative loss means the loss

of

weight which may occurs due ^to different reasons viz. poor performance

of

labour, carelessness

of

labour during drying period,

birds,

rodents and insect damage. Besides,

the

lengthy unfavorable weather condition damage the product, which is not suitable

for

human consumption, ^has to be removed. Quantitative loss of sun drying was determined from equation (8) and equation (9) as shown

in

Table 5. Necessary data (price

of

cabbage, mango, pineapple and fish, utilization

factor

and loss

factor)

were obtained

from

^market

price

^as

well

as from literature (Rahman 2000).

M A Rahman, A T MZiaUddin and S M I Hossain

Table 5. Calculation of quantitative loss for sun drying

Item (i) Amount of sample (s.i) kg

lbatch/mz

Effectiv

e drying afea (A.i) m2

Drying tirne/batc h

for crop i, (T.i) day.

Total drying

time for crop i (T.i)

dav/vr.

Utiliz ation factor for dryer (K"')

Drying rate capacity , (T.i) kglyr

Loss f'actor fbr crop i, (Ri)

Unit price

of crop i,

(P,i) Tk. /ks

Total loss, Tk. /yr

2 J 4 5 6 7 8 9 t0

Cabbage Mango Pineapple Fish

5.5 6.25 6.25 7.0

4A 40 40 40

2.5 5.0 5.0 7.0

58 22 47

9l

0.8 4083

0.05

0.8 880

0.r2

0.8

^r

880

0.r2

0.8 2912

^0.10

5

^1020.8

35

³⁶⁹⁶

15

3384

50

14860

Total quantity loss of tunnel dryer. I ouuntitu =Tk. 22,960.8/Yr

Qualitative ^Loss

for

^{Sun Drying}

Qualitative ^loss of dried products is generally occurred due to several factors, viz. colour, taste or odour and flavour. The contaminants such as insect fragments, rodent's hairs and dust

within

the products are also responsible

for

the loss

of

quality and these results in monetary loss. Qualitative loss

from

sun drying was determined

by

using the equation

(10) with

respect

to the quality level of the

product

as dried by the

tunnel dryer.

Necessary data were obtained from market ^as well as from literature, which are shown in Table 6.

Table 6. Calculation of qualitative loss for sun drying

Cabbage Mango Pineapple Fish

)ZJ 100 214 1067

t4 l5 l5

16.7

40 100 25

75 50 t20

20 60

8075 7500 10700 128040

6460 6000 8560 106700

l6 t5

l 500 2t40 21340 Itern (i) Amount of

dried product, (Pa;) kg

Safe moisture content Vo mc

Unit price of product as dried by tunnel dryer,(P,;) Tk.lkg

Unit price of product as dried by sun drying, (P.i) Tk./kg

Annual cost of product dried by tunnel dryer, Tk./yr

Annual _cost of product dried by tunnel drying, Tk./yr

Total quality loss, Tk./yr

I 2 J 4 5 6=(2)(4) 7=(2)(5) 8=(6)-(7)

Total quality loss for sun drying, 26595|yr

Total annual drying loss of sun drying was determined as Tk. 49,555.81yr from epuation _1t

t;

Annual Cost of Traditional Sun Drying

The total annual cost

of

sun drying was calculated

Tk

63,L49.40 by using equation (lZ).

The total annual cost (Drying cost + drying loss) is shown in a cash flow diagram (Fig.3).

The total annual costs for the same time of effective working

life

of tunnel solar dryer ⁽¹² years) were converted into Expected Net Present Value (ENPVs) of cost from equation

t28

Economic evaluation of a tunnel type solar dryer

(14).The total Expected Net ^Present Value of cost was found

TK.

4g3,42g.d3 ur" shown in Fig. 3.

AC ₌ Tk.63,149.4

Tk. 49,555.8

63,r49.4

AC Y

ENPV.

=

Tk.493,429.93

Fig. 3. Cash flow diagram for traditional sun drying Comparison of costs between two methods of drying:

The total annual cost and Expected Net Present Value (ENPV) of costs with and without drying ^losses in two methods are shown in Table ^7.

AC ₌ Tk.

Table 7. Comparison of drying costs between two methods of drying

Method

Total annual cost with losses,Tk.

Total annual operating cost without losses,Tk.

Total annual drying losses without operating cost,Tk.

Total ENPV of

cost with losses,Tk.

Total ENPV of operating cost without losses,Tk.

Total ENPV of cost of drying losses,Tk.

2 J 4 5 6 ¹

Tunnel dryer Sun dLjing

.21,434.32 631,049.00

19,713.32 '13,593.60

1,661.00 49,555.80

205,238.55 493,429.93

t93,921.00 I1,3t7.50

65,t93.93

^428,236.00 Conclusion

The total expected Net Present Value of costs of tunnel dryer was

Tk

205,240.40 and that

of

sun dr"ying was Tk.493,429.93, which

is

about 2.40 times gteater than that

of

tunnel dryer method.

A

significant amount of money (about Tk. 49,555.80) is being lost every year due to sun drying. On the other hand, a significant amount

of

money can be saved every year

by

using tunnel dryer. Besides, the quality

of

dried products obtained from tunnel dryer is good

in

colour, flavour and taste. In contrast, the quality

of

dried product from sun drying is bad in colors, flavors and taste and sometimes not suitable for human consumption. Therefore,

it

may be concluded that the tunnel solar dryer is economically feasible and potential in Bangladesh for drying of wide ^range of agricultural products.

M A Rahman, A TM Zia Uddin and S :.4 I Hossain

References

Bala, R.K. 1997. F.Yperi1tu?ntal Inve .. trigndnn nfSnlar Drying of ^Fish, Fruits and \¹eg�tnbf,.,t U'iing Tt1nuel Dryer. Department of �JJm Power and M&:hincry. RAl�. Mymcnsingh, Bangladesh.119-129 .

Guuing, J.P. 1994. &-om>mic.11,a/yjis ofAgricultural Projectt, 2"' Bd.. Johns Hopkins University Press, Baltimore.

Hunt, D.R. 1978. Farm Power and Mm:iu,tl.'ry Managemenl. Sixth Ed .. Low State University

Press AMES, Lower, U.S-".. 48.p.

Muhlbauer, W. 1986. Present Sta�s of Solar C:mp <lr}ing. &rergy i11 Agricu/n,re, 5: 121-137.

Rahman. M.A. 2000. Economic Evaltuuion o/Tunnel Type Solar Dryer. An under- graduate prujcct report submitted to che Dept. of Fann Power and Machinery, Bangladesh

Agriculnrral University, Mymensingb. Bangladesh. 26-32.

130

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i

1

�

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