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Direct Drive Photovoltaic Milk Chilling Experience in Kenya

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The Photovoltaics for Sustainable Milk for Africa through Refrigeration Technology (PV-SMART) uses direct drive PV for off-grid milk cooling under the USAID Powering Agriculture Energy Grand Challenge Program (PAEGC). The project is implemented by Winrock International and SunDanzer Refrigeration Inc. refrigeration. The PV chillers are direct drive using a dc compressor that chills ice stored in the walls of the refrigeration unit. This eliminates the need for electro-chemical batteries and successfully chills milk to 10°C in 2 hours and 4°C by morning preventing bacteriological growth. Farmers can receive a premium price for providing higher quality, refrigerated evening milk to dairy processors that would otherwise spoil. These PV farm milk chillers are the first of their kind with 80 pilot units deployed in Kenya.
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IEEE Photovoltaic Specialists Conference 44, Paper #575
Washington DC, June 28, 2017
Best Poster AwardArea 12: PV Deployment & Sustainability
Direct Drive Photovoltaic Milk Chilling Experience in Kenya
Robert Foster1, Brian Jensen2, Brian Dugdill1, Wendy Hadley1, Bruce Knight1b
Abdul Faraj3, Johnson Kyalo Mwove3,
1 Winrock International, Arlington, Virginia (1 USA and 1b Kenya)
2 SunDanzer, Inc., Tucson, Arizona (USA)
3 Egerton University, Department of Dairy and Food Sciences (Njoro, Kenya)
Abstract - The Photovoltaics for Sustainable Milk for Africa
through Refrigeration Technology (PV-SMART) uses direct drive
PV for off-grid milk cooling under the USAID Powering
Agriculture Energy Grand Challenge Program (PAEGC). The
project is implemented by Winrock International and SunDanzer
Refrigeration Inc. refrigeration. The PV chillers are direct drive
using a dc compressor that chills ice stored in the walls of the
refrigeration unit. This eliminates the need for electro-chemical
batteries and successfully chills milk to 10°C in 2 hours and 4°C
by morning preventing bacteriological growth. Farmers can
receive a premium price for providing higher quality,
refrigerated evening milk to dairy processors that would
otherwise spoil. These PV farm milk chillers are the first of their
kind with 80 pilot units deployed in Kenya.
I. INTRODUCTION
The Photovoltaics for Sustainable Milk for Africa through
Refrigeration Technology (PV-SMART) project aims to
tackle off-grid milk cooling under the United States Agency
for International Development (USAID) Powering Agriculture
Energy Grand Challenge Program (PAEGC). In collaboration
with Winrock International (WI), SunDanzer Refrigeration
Inc. (SDZR), a leading US solar refrigeration technology
company, was awarded a USAID grant to implement the
project. PV-SMART began in 2013 to develop the world’s
first on-farm solar milk chiller. Direct drive PV refrigerators
were developed nearly 20 years ago and are commonly used
for vaccine refrigerators for remote clinics [1]. This project
has scaled up this concept to develop an affordable direct
drive with thermal ice storage capable of chilling up to about
40 liters of evening milk. The project has piloted 80 of these
innovative milk chillers in Kenya and soon in Rwanda,
allowing farmers to sell between 5 to 40 extra liters per day of
higher quality evening milk. This results in additional farmer
income, ranging from US$60 to US$500 extra incomes per
month, depending on the number of cows per farm. Solar
investment payback averages about 6 months for these
smallholder farmers.
This 4-year project began in 2013 and is implemented in
collaboration with the County Governments and Agriculture
Ministries of Baringo and Nakuru, and the Department of
Dairy and Food Science and Technology at Egerton
University located at Njoro, and various partner dairy
cooperatives and dairy processors in Kenya, as well as with
Chloride-Exide leading field installations.
There are over 850,000 smallholder dairy farmers in Kenya,
about 85 percent of who do not have access to the national
electric power grid. Diesel fuel is expensive and logistics
difficult to deliver to small rural dairy farmers. Thus, there has
not been an economical method available for on-farm milk
chilling for the vast majority smallholder dairy farmers in
Kenya and other less developed regions globally. The typical
Kenyan dairy farmer has about 3 to 5 cows, producing an
average of about 8 liters per day of milk per cow (typically
~60% as morning milk and ~40% as evening milk). Dairy
cooperatives have an organized morning milk collection
system, but normally do not accept evening milk since by
morning due to high bacteriological counts growing overnight.
Due to the lack of on-farm refrigeration, evening milk is either
forced consumed, sold cheaply to nearby neighbors or
hawkers, or spoils. Only about 40% of milk produced
nationally is processed in Kenya.
Fig. 1. PV array installation for FMC in Mogotio, Kenya
IEEE Photovoltaic Specialists Conference 44, Paper #575
Washington DC, June 28, 2017
Best Poster AwardArea 12: PV Deployment & Sustainability
This failing in upstream milk production causes milk
spoilage and lost farm earnings. It also causes poor quality
milk and further losses in earnings along the downstream
dairy value chain. Of the milk that does arrive, much of it still
has a high bacterial count due to lack of refrigeration,
resulting in poor quality dairy products. Farmers could receive
a premium price for better quality, refrigerated milk; dairy
processors could charge a premium for better quality products
if milk can be kept cool all the way from cow to consumer;
especially during the all-important first four hours after
milking that determine quality.
In order to enhance the value of milk from remote
producers, PV-SMART has developed an affordable solar
powered farm milk chiller (FMC) so these producers can
deliver cool milk rather than warm to the central collection
stations. The farmers also use FMCs on the farm to preserve
other produce such as eggs, meat, fruits and vegetables.
Besides demonstrating the technology proof of concept, PV-
SMART is also working with stakeholders like Kenyan
SACCOs (Savings and Credit Cooperative Associations) to
provide financing for solar technologies like FMCs that can
increase on-farm productivity and incomes. Farmers often
need access to technology and credit on reasonable terms to
finance the initial purchase of solar power systems, which
have higher capital costs but lower operating costs when
compared to traditional remote generation energy technologies
like diesel gen-sets.
PV-SMART has a four-phase implementation strategy for
developing, disseminating, and financing FMCs in Kenya:
Year 1Technology Development: Designed and tested
prototype solar farm milk chiller (FMC) by scaling up an off-
the shelf photovoltaic refrigerator (PVR) model. Surveys were
conducted of smallholder dairy farmer’s needs, and besides
milk chilling, a wire basket was added for perishable
household food items, as well as two 5V USB ports for
daytime cell phone, radio, and LED lantern charging.
Year 2Pilot Phase 1: Piloted the world’s first solar FMCs to
39 smallholder dairy farms in Baringo and Nyandarua
Counties of Kenya. A baseline control unit was also installed
at the Egerton University (EU) Department of Dairy and Food
Science for more in-depth testing and milk quality
evaluations. Field evaluations and farmer surveys were
conducted by EU.
Year 3 Field Testing Pilot Phase 2: Based on Phase 1 field
experience, design and testing of a next generation prototype
was developed with 40 units deployed to Kenya: (i) design
adaptations notably moving from a ground to roof mounted
PV system; (ii) established a local dealer network with
Chloride-Exide; and (iii) begin financing units to farmer with
Kenyan Savings and Credit Cooperative Associations
(SACCOs), starting with Skyline SACCO in Mogotio.
Demonstrations are also expanding to new regions with NGOs
like Mercy Corps and GiZ, including for camel milk chilling.
Year 4Commercial Rollout Phase 3: Planning is underway
to expand the solar FMC technology commercially both inside
and outside of Kenya with Chloride-Exide and SACCOS
II. DIRECT DRIVE PHOTOVOLTAIC REFRIGERATION
The SunDanzer direct drive solar farm milk chiller (FMC)
uses a vapor compression refrigeration system and directly
couples a PV array to a dc compressor. The FMC uses thermal
phase change material (PCM - ice storage) instead of electro-
chemical battery storage. By storing ice in the walls of the
refrigerator, it eliminates the needs of battery storage; ice
never wears out and provides sufficient energy storage to cool
40L of milk overnight. The embodied technologies were
originally developed in support of NASA’s future planetary
missions’ refrigeration requirements in the late 1990’s [2, 3].
Fig. 2. PV direct drive milk chiller array, note E-W orientation.
Fig. 3. PV powered chiller using thermal ice storage and brine
bags to chill evening milk.
IEEE Photovoltaic Specialists Conference 44, Paper #575
Washington DC, June 28, 2017
Best Poster AwardArea 12: PV Deployment & Sustainability
Fig. 4. Rooftop PV installation for Mogotio dairy farmer FMC.
In addition to increasing the quality of product for farmers, the
solar FMC has two 5 V USB plug ports capable of charging
cell phones, radios, and solar lanterns which farmers use for
themselves or rent out. Likewise, there are dietary and health
benefits for farmer families to store vegetables, fruits, meat,
etc. in the solar FMCs, which also reduces the frequency of
trips to town to purchase fresh produce.
A. “Fixed Tracking” Array
The solar FMC system also uses an innovative East-West
“fixed tracking” array to maximize compressor run time and
not daily energy production. Conventional tracking increases
both capital and operating costs due to additional hardware
and maintenance requirements for moving parts. While a
conventional equatorial facing PV array power output is well
over the required power requirements for the FMC at solar
noon; the East-West array’s output wattage supplies the
required compressor power for a longer period. Thus,
increasing compressor run time providing longer operating
hours for farmers to chill more milk. While this approach does
not maximize energy usage, it does maximize ice production
over the course of the day. PV prices have come down
sufficiently that fixed tracking is a viable economic option
over tracking without the future maintenance concerns. This
type of approach works especially well in equatorial latitudes
like Kenya. This simple approach provides reliable
performance [4].
Fig. 5. PV direct drive PV array with “fixed E-W tracking.”
With the compressor running most of the daylight hours due
to the E-W “fixed tracking” array (the array is not actually
moving like a conventional tracker, but is fixed with half the
array facing East and the other half facing West to maximize
daily compressor run time). Ice is formed and stored into the
walls of the PVR. Thus, there is no need for expensive battery
storage and replacements. Ice does not wear out. Testing at
New Mexico State University for NASA and SDZR on an
early prototype PVR with ice storage was successful [2] and
led to the development of direct drive vaccine PVRs using ice
storage. The proven PVR technology was then increased in
size for larger scale milk chilling.
Fig. 6. E-W “fixed tracking” array designed to maximize daily
compressor run time rather than energy capture.
In order to maximize heat transfer, the solar FMC
incorporates brine bags, which do not freeze at 0°C, that are
placed around the milk cans to increase heat transfer and cool
milk quickly. Milk naturally contains antibacterial agents to
protect the suckling young from potential infectious diseases;
these antibacterial agents also slow bacteriological growth
the cause of milk souring. This effective natural protection is
called the lactoperoxidase system, and has both bacteriostatic
and bactericidal effects against some milk spoilage microflora
for about the first four hours after milking. Bacteriological
IEEE Photovoltaic Specialists Conference 44, Paper #575
Washington DC, June 28, 2017
Best Poster AwardArea 12: PV Deployment & Sustainability
growth is further retarded when milk temperatures fall below
10°C and is essentially halted at 4°C. The FMC chills 25 liters
of milk down to 10°C in a couple of hours, and the milk
temperature by morning is about 4°C [4].
Since dairy farmers typically milk cows twice a day, once in
the morning (~60%) and again in the evening (~40%), evening
milk must be consumed or sold to neighbors or hawkers at a
cut price. Even so, much of the evening milk spoils overnight.
About 60% of milk in Kenya is not processed mostly due to
the lack of on-farm chilling options. Solar FMCs increase
farmer incomes from selling milk that would otherwise spoil,
and some innovative dairy processors making cheese and
yoghurt who need better quality product offer a Quality Milk
Payment system incentive to dairy farmers. Solar chilling
provides farmers the means to improve their milk quality and
overall sales.
III. OPERATIONAL FINDINGS
WI in collaboration with Egerton University Dairy and
Food Sciences Department has been monitoring and
evaluating (M&E) the performance and benefits of the Solar
FMCs installed on the Mogotio and Ngorika Cooperative
dairy farms.
PV-SMART team is also monitoring solar irradiance at
Ngorika and Egerton University sites. A few selected milk
cans have a Hobo data logger installed on them to monitor
milk can temperature data. The temperature probe is installed
on the can with foam over it so that it measures true milk can
temperature only.
The findings are based on milk can temperature data
collected, co-op milk sales, surveys with the end-users, milk
can temperature data, and field observations by the WI and
Egerton University team. All of the original 40 piloted solar
FMCs have functioned for 2.5 years with no failures, and no
failures in the next 40 Phase 2 units as well. There was one
Phase 1 unit which had a refrigerant leak upon delivery due to
springing a refrigerant leak over some extremely rough roads
traversed for delivery; this was easily repaired by a local
refrigeration technician from Chloride-Exide for US$40 and
the unit has functioned with no issues ever since. The solar
FMC technology couples mature PV technology with mature
vapor-compression technology and is very reliable.
Milk temperature: The FMCs work well to chill 25 liters of
evening milk to 4OC and lower. If some milk is not removed
the next morning and left throughout the day, small quantities
of milk can freeze, indicating the prototype FMC may have
‘spare’ cooling capacity for Kenya. The figure below shows
daily milk cooling cycle for one of the farmers, milk
temperature is repeatedly cooled to aboutC. Note that the
farmer puts the milk can outside in the direct sunlight for
drying after cleaning so the can heats up to above ambient
peak temperatures during the daytime.
Fig. 7. Example Daily milk cooling temperature cycles on a dairy
farm: milk can temperature °C. Note after cans are cleaned they are
placed outside in the sun to dry and UV disinfect during the day.
Fig. 8. Total Viable Count (TVC) of bacteria show there is no
bacterial growth once the milk is placed in a solar farm milk chiller.
Cooling Capacity: About half the users did not have
enough evening milk to fill the pilot FMC. About ¼ of users
utilize full capacity at 25 liters either from their own
production or by also combining production with that of their
neighbors, thus earning extra income for milk
handling/bulking. Another user also earns extra income from
charging cell phones from the two USB ports installed on the
refrigeration unit, as much as US$1 per day (rate of US$0.10
per phone charge).
Some users are storing/cooling milk in plastic containers in
the FMC and already exceeding the original design capacity
by chilling up to 40 liters milk in food grade plastic
containers, achieving overnight cooling to ‘below 10OC,
indicating the potential of the unit to chill more milk
adequately.
IV. IMPACTS AND RESULTS
PV-SMART is piloting 80 solar FMCs in Baringo, Kisumu,
Nakuru, Nyandarua, and Wajir counties, as well as one control
IEEE Photovoltaic Specialists Conference 44, Paper #575
Washington DC, June 28, 2017
Best Poster AwardArea 12: PV Deployment & Sustainability
unit at Egerton University. The first 40 Phase 1 Pilot solar
FMCs have operated flawlessly in the Nakuru milkshed of
Kenya with no equipment failures in the first 2.5 years.
Table 1
Change in farmer evening milk usage with solar Farm Milk Chillers (FMCs)
Location
Did milk
sales
increase?
Evening Milk Usage
After FMC Installation
Forced Home
consumption
Local sales
Forced Home
cons. / Local sales
Sales to Dairy
Processors/Coops
Mogotio
Hot climate
No (7.7%)
69%
31%
8%
92%
Yes (92.3%)
Ngorika
Cool climate
No (16.7%)
27%
73%
0%
100%
Yes (66.7%)
Source: Egerton University
The average dairy farmer chilled about 25 L of evening
milk to 4°C; a few farmers chill as much as 40 L every night.
Milk quality is maintained after milking and there have been
zero rejections of solar chilled milk for any of the participating
dairy farmers using solar FMCs, unlike from before. An
informal farmer-to-farmer milk supply network was also
organically created by solar FMC owners with excess capacity
provided to their neighbors through FMC sharing (rent, barter,
or purchase).
Over 92 percent of Mogotio farmers (lower elevation and
hotter climate) and 67 percent of Ngorika farmers (higher
elevation and cooler climate) reported increased milk sales
directly attributable to chilling evening milk using solar
FMCs. Other on-farm production factors include a severe
drought in 2017 reducing forage and milk production for some
farmers.
Fig. 9. Satisfied Ngorika dairy farmer with solar FMC unit chilling
40 liters of evening milk every day for sale the next morning.
Thus, milk quantity and potential incremental gross
earnings gain at current milk prices is excellent for these pilot
units, with simple payback ranging anywhere from six months
to one year depending on user milk production. From the
initial surveys users sell between 5 and 45 liters of extra
evening milk each day, indicating gross incremental income
gains ranging from US$50 to $650 per month. Kenyan small
scale financial credit institutions (SACCOs) have begun
financing PVRs during Phase 2 of PV-SMART.
Field surveys found that 83 percent of the Phase 1 pilot
FMC farmers felt the solar FMC technology was worth the
initial cost and is a worthwhile investment. Financing is key as
over 70 percent of small holder farmers prefer a short-term
loan mechanism to purchase the technology.
V. CONCLUSIONS
PV direct drive solar milk chillers (FMCs) have been used in
Kenya with zero failures in the first 2.5 years of operation.
Smallholder dairy farmers have sold between 5 and 40 extra
liters of evening milk each day, depending on their dairy herd
size. Resulting farmer income gains ranged from US$60 to
$500 per month, with expected FMC payback typically in less
than a year. This type of solar milk chilling uses no batteries
and has no regular maintenance requirements. There are over
5 million smallholder dairy farmers in East Africa who can
benefit from this technology, not to mention the millions more
of other off-grid smallholder dairy farmers in the rest of
Africa, Asia, and Latin America that can also benefit from
solar FMCs to improve livelihoods and delivered milk quality.
REFERENCES
[1] R. Foster, M. Ghassemi, A. Cota, Solar Energy, Renewable Energy
and the Environment Series, Volume 2, Taylor and Francis
Publishing, CRC Press, A. Ghassemi (Ed.), ISBN:
13:9781420075663, Boca Raton, Florida, August, 2009.
[2] R. Foster, R., L. Estrada, D. Bergeron,Photovoltaic Direct Drive
Refrigerator with Ice Storage: Preliminary Monitoring Results,”
ISES Solar World Congress, Adelaide, Australia, 2001.
[3] M. Ewert, D. Bergeron, R. Foster, L. Estrada, and O. LaFleur,
"Photovoltaic Direct-Drive Battery-Free Refrigerator Field Test
Results," SOLAR 2002, ASES, ASME, NPSC, Reno, Nevada,
June 15-20, 2002.
[4] R. Foster, B. Jensen, B. Dugdill, B. Knight, A. Faraj, J. K.
Mwove, and W. Hadley, “Solar Milk Cooling: Smallholder
Dairy Farmer Experience in Kenya,” ISES Solar World
Congress, Daegu, South Korea, November 12, 2015, 11 pp.
Foster, R., L. Estrada, D. Bergeron, 2001. Photovoltaic Direct Drive Refrigerator with Ice Storage: Preliminary Monitoring Results, Presented at “ISES Solar World Congress,“ Adelaide, Austr
... In this research a smart cooling system is proposed based on the thermoelectric cooling module (TECM). A similar approach has been proposed in [8]. TECM, also known as Peltier cooler, because it is based on the Peltier effect is a semiconductor-based electronic component that functions by removing the heat from one side to the other when a low DC power source (12 V) is applied. ...
Conference Paper
Full-text available
This paper describes the results of laboratory and field testing conducted on photovoltaic (PV) direct-drive solar refrigerators using ice thermal storage.
  • R Foster
  • M Ghassemi
  • A Cota
R. Foster, M. Ghassemi, A. Cota, Solar Energy, Renewable Energy and the Environment Series, Volume 2, Taylor and Francis Publishing, CRC Press, A. Ghassemi (Ed.), ISBN: 13:9781420075663, Boca Raton, Florida, August, 2009.
Photovoltaic Direct Drive Refrigerator with Ice Storage: Preliminary Monitoring Results
  • R Foster
  • L Estrada
  • D Bergeron
R. Foster, R., L. Estrada, D. Bergeron, "Photovoltaic Direct Drive Refrigerator with Ice Storage: Preliminary Monitoring Results," ISES Solar World Congress, Adelaide, Australia, 2001.
Solar Milk Cooling: Smallholder Dairy Farmer Experience in Kenya
  • R Foster
  • B Jensen
  • B Dugdill
  • B Knight
  • A Faraj
  • J K Mwove
  • W Hadley
R. Foster, B. Jensen, B. Dugdill, B. Knight, A. Faraj, J. K. Mwove, and W. Hadley, "Solar Milk Cooling: Smallholder Dairy Farmer Experience in Kenya," ISES Solar World Congress, Daegu, South Korea, November 12, 2015, 11 pp.