S. G. Stephens BE (Hons) 1

June 2012

M E M O R A N D U M O N I N I T I A L T R I A L O F S O L A R

B O T T L E B U L B I N J O R G E N B A B U R M A R T S L U M ,

D I N A J P U R , B A N G L A D E S H

Prepared by S. G. Stephens 7th June 2012 for SAFE Bangladesh (NGO)

Pictures and video by Marianne Keating

INTRODUCTION

SAFE Bangladesh is a small NGO working primarily in the low-cost housing sector in North West

Bangladesh. As part of their work improving quality of life through improved building techniques, SAFE

has started to experiment with using water-filled plastic bottles to provide low-heat and electricity-free

lighting.

OVERVIEW OF INTIAL TRIAL

Intial trial bulb was installed 6th June 2012, at the house of local slum builder Delowar. As this was an

initial trial, bulb was placed near wall where it would be less-effective but where it could be placed

through a small section of rather tired corrugated iron (CI) sheet that could be easily replaced.

A 2L coke bottle was filled with a mix of boiled water and approximately 250ml of Clorox liquid bleach

purchased in Dhaka. Bangladeshi bleach seems to be far weaker than the equivalent in the UK. The bottle

of Clorox states an active ingredient (Sodium Hypochlorite) concentration of >5,25%. Taking the label at

its word, the bottle bulb should contain approximately 6.5ml of Sodium Hypochlorite per liter.

The bulb was initially placed and sealed into a small 500x500 section (or 'patch') of CI sheet using McCoy

General Purpose Acetoxy Silione Sealent purchased from a glaziers in Dinajpur. After curing, a hole was cut

in the roofing CI sheet and the bottle and 'patch' sealed on top.

PHOTOS

Bottle and CI sheet 'patch' before sealing Cutting hole in roofing sheet

S. G. Stephens BE (Hons) 2

June 2012

Sealing between patch and roof sheeting Placement

INTIAL COST ESTIMATE

Intial Cost Estimate of Solar Bottle Bulb

In Dinajpur, Bangladesh (June 2012)

Item Cost No. Bulbs Cost/Item

Silicone applicator gun BDT 400 ignored

Tin Shears BDT 100 ignored

2nd hand plastic bottle BDT 10 1 BDT 10

Silicone 280ml tube BDT 250 2 BDT 125

Bleach (1L 5.25% NaOCl) BDT 210 4 BDT 53

CI sheet 'patch' BDT 500 10 BDT 50

BDT 238

238BDT/bulb is possibly too expensive for the Solar Bottle Bulb to be widely adopted in JBM slum.

The following areas could produce savings in the cost of each bulb;

1. Finding a cheaper silicone or sealant, possibly in bulk with a brush application. Important

qualities for the sealent are; elastic, bonds to steel and plastic and resistant to water, sun and

elevated temperatures.

2. Finding a cheaper and locally sourced bleach. 'Bleaching powder' was found in Dinajpur though

this powder had only very week concentrations of Chlorine and was cut with an insoluble

powder that would make the bulb ineffective. Bleach needs to be found with as little colouring as

possible, the Clorox used in the test has a slight yellow tinge which coloured the bulb.

3. Using second hand CI sheet to form the patches. This was done for the initial test bulb though it is

hard to discern a cost for such a second hand item and new CI sheet prices are used in the

calculation above.

S. G. Stephens BE (Hons) 3

June 2012

RESULTS

Once placed, the bulb was very bright and provided a large amount of light into the previously very dark

room. Please refer to http://youtu.be/rlS17jVZ6s0 for a visual demonstration of effectiveness.

The installation will be monitored over the upcoming Bangladesh rainy-season to evaluate effectiveness

and durability of sealing system used.

Room interior with Solar Bottle Bulb covered

Room interior with Solar Bottle Bulb un-covered

S. G. Stephens BE (Hons) 4

June 2012

COMPARISSON TO OTHER LIGHTING ALTERNATIVES

CLEAR PLASTIC CI SHEET

One strip or even a short section of clear plastic corrugated sheet provides large amounts of light into a

room. A 7' sheet costs 700BDT which is approximately 1.5times the cost of the thick CI it replaces. So, this

is not inordinately expensive yet there is not one house in the slum where this has been used.

Possible reasons for the clear plastic sheet not being adopted are;

• Heat. A small, 1'x2' section of the plastic sheet was installed in a SAFE demonstration house and

provided a lot of light though the owner complained about the heat.

• Frailty and durability. The plastic sheeting is seen to be weaker than the CI sheet it replaces and is

likely to get dirty.

Comparing cost;

A 2'4" x 2'6" clear plastic corrugated sheet suitable to make a skylight costs about 233BDT which

is comparable with the 238BDT it cost for the initial trial solar bottle bulb.

It is hoped that the cost of the bottle bulb can be significantly reduced and that it performs better

that the plastic corrugated sheeting in terms of heat and durability therefore making the solar

bottle bulb a viable alternative.

ELECTRIC BULB

Almost all the houses in the slum use at least one electric bulb, sometimes through an illicit connection.

The electric bulb works at night while the solar bulb obviously won't. This disadvantage is somewhat

mitigated by the fact that the electricity supply is very intermittent. During peak irrigation season, rural

areas of Dinajpur can receive as little as a few hours of electricity each day while the sun shines almost

perpetually.

Comparing cost;

From a recent electricity bill, the current price of electricity in Dinajpur appears to be

4.2BDT/kWh (1/6th of the price in the UK).

Assuming a 50watt bulb is used for 6 hours each day;

0.060� × 6ℎ × 4.2��

�ℎ= 1.512

��

���

At the initial solar bottle bulb cost of 238BDT, the payback period is about 5½months.

It is hoped that, by reducing the cost of the solar bottle bulb, the pay-back period can be reduced

and the financial advantage increased.

The cost of a traditional tungsten filament bulb is only 22BDT. If we consider a 5watt energy-

saver bulb, the pay-back period jumps to over 5years. However, the initial cost of an energy saver

bulb is approximately 250BDT and therefore more expensive than the solar bottle bulb. An

energy-saver bulb will also be susceptible to the sporadic electricity supply.

S. G. Stephens BE (Hons) 5

June 2012

LESSONS LEARNED AND KNOWLEDGE GAINED

1. Bulb is effective yet expensive (≈240BDT). Steps described earlier in 'Initial Cost Estimate' could

significantly decrease cost and improve likelihood of technique being adopted.

2. A cheaper and possibly simpler form of sealant needs to be found locally.

3. A cheaper and possibly 'clearer' bleach or disinfectant needs to be found locally.

4. Monitoring and experimentation is required to see which concentrations of which

bleaches/disinfectants are most effective and affordable.

5. It is important to use good quality CI sheet for the patch as well as select a good piece of receiving

CI sheet on the roof. This is because worn CI sheet can have a less-pronounced or deformed

corrugation profile and therefore be difficult to seal.

6. It is important to center both the hole in the patch and the hole in the receiving sheet to the same

orientation of the corrugations. i.e. a corrugation ridge should correspond to the centerline of

both the hole in the patch and the receiving sheet.

7. Financial and other advantages of these bulbs are currently not very convincing to slum

residents. Further study is required to produce a stronger case to submit as to "why?" they should

install a solar bottle bulb.

LONG-TERM VISION

It is hoped that one or more of the local Jorgen Babur Mart slum builders (Delowar, Masud or Baush) can

be trained how to install solar light bottles and do so for a reasonable price while earning some money

for themselves. In short, to create a small entrepreneurial business to provide improved lighting

throughout the slum.