August 2017
Solar E Technology
[SOLAR HYBRID COLD STORAGE]
A pilot R & D site at Chuadanga sponsored by IDCOL & World Bank
Executive summary:
Bangladesh is one of the largest producer of fruits and vegetables but the availability of
fruits and vegetables per capita is significantly low because of Post-harvest loses which
account for about 25% to 30% of production. Further, the quality of sizeable quantity of
produces also deteriorates the moment it reaches the consumer. This happens because of
perishable nature of the products. If consumption is not getting stabilized, the farmers
switch over to other crops instead of going for one crop in the subsequent year, and cycle
continues. Our farmers continue to remain poor even though they take risk to cultivate
high value fruits and vegetables year after year. Introduction of Cold storage / Cold room
facility will help them in removing the risk of distress sale and simultaneously will ensure
better returns.
On the other hand, the fruits, vegetables and flowers have also limited life after harvest.
Post-harvest cooling rapidly removes field heat, reduces respiratory - activity, reduce
internal water, wilting, slow the growth of microorganism and reduces the production of
natural ripening agent i.e. ethylene. Post-harvest cooling also provides marketing flexibility
by allowing the grower to sell produce at the most appropriate time.
With the financial assistance of World bank and IDCOL , Solar E Technology has embarked
on a demo solar hybrid cold storage project at Chuadanga and conducted a
comprehensive R & D exercise on cool room temperature & humidity control
performance, assessment of shelf life of different vegetables, fruits and flowers, freshness
quality of produce after removing from storage.
A comprehensive cost benefit was conducted considering a commercial project of storage
capacity of 60MT of fresh produce. Payback periods for various financial modelling
scenario for both off-grid and on-grid solar hybrid cold storage are presented in this
report. This is a crucial time for the Government of Bangladesh and IDCOL to make policies
of introducing commercial solar hybrid cold storage.
Solar cold storage system schematic
Cold storage specification:
BASIC DESIGN OF COOL ROOM
SN Description Specifications
1 Cool room dimension 5m (L) X 3m (W) X 2.5 (H)
2 Cool room temperature 4˚C ±2˚C
3 Humidity 85-90% RH
4 Ambient temperature 35˚C
5 Storage goods Fresh vegetables, fruits & flower
6 Product storage capacity 2 MT
7 Product entry average temperature 30˚C
8 Product incoming rate (loading rate) 50% ( 1000 kg per day)
9 Maximum pull down time 24 hrs/batch
Polystyrene sandwich panel (EPS sandwich
board which made of outer layers both sides of
10 Insulation
pre-painted steel coil and inner layer of
polystyrene.
11 Floor 100mm thickness of RCC and top paper board
12 Hinge door 1000mm (W) X 2500mm (H), 1No.
13 Cooling demand 3.76 kW
6.0 kW at -3˚C SST and condensing
15 Compressor cooling capacity
temperature of 40˚C
16 Evaporator cooling capacity 8.64 kW
17 Refrigerant R404A
18 Compressor type Reciprocating
Cooling load calculation sheet:
Condensing unit specification:
Evaporator specification:
Photos of solar hybrid cold storage:
Front view
Side view
Photo of rear side view showing evaporator unit and control room entrance
Control room
Ultrasonic humidifier
Solar Inverter
Water vapour
Evaporator unit generates from
humidifier
Test set up:
Cooling performance was observed during
1) Test 1: Cool room average temperature 4.0 ˚C
2) Test 2: Cool room average temperature 6.0 ˚C
3) Test 3: Cool room average temperature 10.0 ˚C
4) Test 4: Cool room average temperature 2.0 ˚C
Relative humidity was set to 90% with 5% hysteresis (RH 85% - 90%)
Produce Freshness quality observation:
1) Inspect freshness quality of fresh produce removing from cool room after 14 days of storage.
Freshness inspection has taken over 24 hours
2) Inspect freshness quality of fresh produce removing from cool room after 21 days of storage.
3) Inspect freshness quality of fresh produce removing from cool room after 24 days of storage.
Test Result – Cooling performance
Cool room temperature chart:
Test3
Daily mean
temperature °C
Test2
Test1
Test1 Test4
Test1
Test2
Test 3
Test 1
Test 4
Cool room relative humidity chart:
Daily average ambient temperature chart at project site
Test Result – Produce freshness quality assessment
The freshness quality was done by comprehensive inspection of storage produce removing from cool
room after
14 days of storage
21 days of storage
24 days of storage
Photo showing the vegetables, fruits and flower after 14 days of storage inside cool room
Photo showing quality of freshness removing outside from storage after 14 days kept in solar cold
storage.
Freshness quality observation for 24 hours after taking from cool room after 14 days
After 2 hours After 6 hours After 24 hours
After 2 hours After 6 hours After 24 hours
After 2 hours After 6 hours
After 24 hours After 2 hours
After 6 hours After 24 hours
After 2 hours After 24 hours
After 2 hours After 24 hours After 2 hours
After 24 hours After 2 hours After 24 hours
Photo showing quality of freshness removing from storage after 21 days kept in solar cold storage.
Photo showing quality of freshness removing from storage after 24 days kept in solar cold storage.
24 days
24 days
24 days
24 days
24 days
24 days
24 days
Power system:
1) Off-grid solar system
2) Alternative source (main grid and diesel generator)
Power system specification:
Item Specification Quantity Total capacity
Solar Panel 250Wp poly 36 9.0kWp
8.0kW hybrid
Solar inverter inverter with 1 8.0kW
MPPT controller
130Ah, 12V
Storage battery Hamco solar 36 56kWh
battery
Diesel generator Self-start 5kVA 1 5kVA
diesel generator
Inverter specification:
Power consumption:
Cold storage daily power consumption was recorded by power analyser.
Power consumption pattern:
Compressor cycling
Defrost
Compressor off
Total Energy Consumption (TEC) per day = 38.98 kW/day (measured via power analyser)
Generation mix:
As July and August is rainy season and it was found most of the day has low sun shine, rainy and
cloudy. There had been 6-10 hours of load shedding every day at project site. In order to monitor
continuously and optimize cold storage performance, the priority of electricity supply was set to grid
first and at the event of load shedding from solar system. Once cold storage performance is
optimised, electricity supply priority has changed to solar first, second grid and diesel generator third.
Supply mix for solar hybrid cold storage Note: This supply
mix is for the month
Supply from solar system
of August and based
Supply from alternative source ( grid & generator)
on complete
continuous 4 days
(96 hours) data.
32%
68%
Cost- benefits analysis:
We are making the following initial considerations & assumptions about a commercial project of off-
grid solar hybrid system for the exercise of cost-benefit analysis:
• Considering project size of 100KWp solar panel.
• With 100KWp solar panels, an expected cold storage of 40kW cooling load can be made.
• Evaporator and condenser size is estimated to be 50kW and 60kW cooling capacity
accordingly.
• Storage battery total capacity to be 650kWh
• Produce storage capacity is estimated to be 60MT.
• Total project cost estimated to be Tk.300 Lac.
• Estimated revenue Tk.0.2 per kg/day
• Occupancy 80%
• Management cost expected to be Tk.1,000,000.
• Supply mix 70% solar & 30% alternative source (grid & generator)
• Diesel generator size 20kVA
• Inflation rate 3%. It is also assumed that the sponsor will provide 15% equity with
incurring further loan at 10% interest for 8 years
Estimated investment at different financial model scenario
(Storage battery based off-grid solar system)
Scenario Financial model
Investment return, year
Equity 15%
1 Loan 55% 9.5
Grant 30%
Equity 15%
2 Loan 45% 7.2
Grant 40%
Equity 15%
3 Loan 35% 6.0
Grant 50%
Equity 15%
4 Loan 25% 4.8
Grant 60%
Attractive model
Acceptable model
Financial risk
As most of the fresh produce trading markets/ bazar have the access of electricity, it is a proposition
to analyse the financial viability for a solar hybrid on grid cold storage system (no storage battery).
Solar power will be the first priority during day operation and during night operation supply will be
from grid and generator. For on-grid solar hybrid cold storage with 40kW cooling load, it is estimated
to have 40kWp solar panel. There will be no storage battery requirement. The estimated project cost
will be Tk 170 lakh. A CBA analysis of such on-grid solar hybrid cold storage has resulted of
investment return as below:
Scenario Financial model
Investment return, year
Equity 20%
1 Loan 80% 8.5
Grant 00%
Equity 15%
2 Loan 65% 5.5
Grant 20%
Equity 15%
3 Loan 55% 4.5
Grant 30%
Equity 15%
4 Loan 45% 3.8
Grant 40%
Equity 15%
5 Loan 35% 3.2
Grant 50%
Attractive model
Acceptable model
Financial risk
Scalability of the project
The current solar hybrid cold storage has designed and produced by Solar E Technology is a
prototype for a commercial system and this design is based on modular concept. No technical
modifications are required when upscaling this system into a large scale commercial system. The
current design ensures an expected project life of 20 years. Furthermore, the every effort has been
made to ensure a reliable resource supply chain which is a vital factor in commercial production.
Social impact of the project
The showcase of our pilot solar hybrid cold storage project attains a great success; it garnered
positive attention from several NGOs and we anticipate that there will be widespread uptake of this
technology when we embark solar hybrid cold storage for commercial use. Several media
representatives have already interviewed us and taken video of our R & D project.
Shelf life observation
Expected shelf life
Name of Fresh Observation
Comment with regards to
fruits/vegetables/flower period
Bangladesh climate
24 days 2 months
Apple ( normal & green) No change in freshness.
Orange/malta 24 days No change in quality 4-5 weeks
24 days Remains fresh and 3-4 weeks
Green Chilli saleable to market
Cabbage 24 days Slight change in freshness. 2 weeks
24 days Remains fresh and 3-4 weeks
Potol saleable to market
Kakrol 24 days Slight change in freshness. 2-3 weeks
24 days Remains fresh and 3-4 weeks
Laou (gourd) saleable to market
Green banana 24 days Colour changed 2 weeks
Ladies finger 24 days Colour changed 2 weeks
Taro (Kochu) 24 days No change in freshness. 4 month
Pumpkin 24 days No change in freshness. 5 -6 month
Rose flower 24 days Leaf becomes slight dry 2 weeks
Night queen flower 24 days Remains fresh and 3-4 weeks
(Rojonigandha) saleable to market
24 days Remains fresh and 3-4 weeks
Marigold flower (Ganda) saleable to market
Potato 24 days No change in freshness. 5-6 month
Eggplant (Bagoen) 24 days Slight change in freshness. 3 weeks
Conclusion
Solar hybrid cold storage for fresh vegetables, fruits and flowers for short term preservation
is an innovative and environmentally sustainable alternative which will help the farmers to
store their produces and market them at the opportune time.
Cold storage performance (temperature & humidity control performance) was monitored
for 24 days and found to be very promising. Ultrasonic humidifier maintained relative
humidity (85-90%) smoothly via humidity controller which helps to preserve perishable
goods longer time. In traditional cold storage in Bangladesh, it is a common practice to spray
water manually and as local water has bacteria and helps to increase rotten the perishable
goods. Ultrasonic humidifier does not produce any heat while producing steam. It atomises
the water particles and kills the bacteria of the water if present.
The shelf life and freshness of flower found to be very attractive and as there is huge existing
fresh flower supply demand in all major cities in Bangladesh, the introduction of solar hybrid
cold storage will bring more business opportunities.
One of the key elements for fresh produce preservation is to maintain suitable relative
humidity and that is why shelf life for fruits and vegetables in the demo project found more
than expected.
Based on the experience gained of fruits preservation in demo project, it anticipated that
mango and jack fruit can be preserved up to 6- 8 weeks.
Power supply mix found to be 68% solar and 32% alternative source (grid & generator). The
theoretical supply mix for the month of August was estimated to 69%. This has revealed the
performance ratio (PR) of solar system is 98.4%.
