TechNet-21 - Forum

This forum provides a place for members to ask questions, share experiences, coordinate activities, and discuss recent developments in immunization.

Discussions tagged Solar

An Alternative to Energy Harvesting Controls (EHC)

EHC is a valuable method of obtaining excess energy from an SDD refrigerator, however an autonomous solar direct system powering USB ports is a simpler, more reliable and less expensive method of providing auxiliary power. USB ports can be powered directly from a solar panel, no batteries are required. The conversion device is simple and reliable; these ports can be used for charging cell phones, ipads, lights and AA or AAA batteries.There are a large variety of lights available: lanterns, directional lights, headlamps and lights with motion sensors. Jump starting car batteries can also be charged by a USB port. If desired a 12 volt port could also be incorporated to power a fan and if needed a 12 Volt battery. USB charged devices typically require an average of 3 watts of charging power. Twelve watts of solar per USB port will supply reliable charging at the beginning and end of the solar day and during overcast conditions. For 4 ports a 48 watt module would provide highly reliable power. This would charge at least 8 devices each day. Having an autonomous system for auxiliary loads has a number of advantages: - With EHC’s the controller is designed for a specific brand and model of refrigerator. An autonomous solar system will work with all types of refrigerators.
- As a consequence of working with only a specific brand and model of refrigerators the aggregate cost of testing will be very high.
- Testing must also be carried out for each specific type of load, resistive, battery charging, etc.
- Trouble shooting system in the field will be much simpler with an autonomous power system there will not be the possibility of interaction between the two systems.
- The autonomous system with USB ports would be inexpensive and easy to install.
- When solar conditions are poor the autonomous system will provide more reliable power for a greater portion of the day. I would be glad to discuss the pros and cons of this system further. EHC’s are a good concept because a 60 watt load is typically powered by a 300 watt array. However, I think a separate autonomous system is a more appropriate solution.

UNICEF/WHO guidance on Decommissioning and safe disposal of CCE now available in ARABIC and RUSSIAN

Dear TechNet-21 community, Further to the publication of the English and French versions of the Decommissioning and safe disposal of cold chain equipment guidance earlier this year (available here, we are glad to share with you that the Arabic and Russian versions of the document are now available in the TechNet-21 Resource Library. To access these documents, please click on the following links:
1. For the Arabic version:
2. For the Russian version: On behalf of UNICEF and WHO, I wish you an insightful reading and look forward to interesting and fruitful discussions with the TechNet-21 community! Michelle Seidel, Cold Chain Specialist - Immunization Supply Chain, UNICEF Programme Division (UN City Copenhagen)  

Les inscriptions pour la formation en chaîne de froid solaire sont ouvertes

Nous avons le plaisir de vous informer que le Centre LOGIVAC organise la Formation en Chaîne de Froid Solaire, du 12 au 17 février 2018. Les dossiers d’inscription seront reçus jusqu’au 30 janvier 2018. Délivrée entièrement en présentiel à destination des agents de maintenance et logisticiens du PEV, la formation en chaîne du froid solaire répond aux enjeux de conservation optimale des vaccins par les équipements fonctionnant à l’énergie solaire. Il permet aux programmes de vaccinations qui sont dans le processus de transition vers le solaire, de disposer de ressources humaines compétentes pour accompagner la gestion des équipements de chaine de froid solaire mis à leur disposition par les partenaires. A l’issue de la session, les apprenants auront les compétences techniques pour : choisir les équipements de la chaîne du froid solaire adaptés ; assurer les conditions optimales pour l’installation des équipements de chaîne du froid, selon les spécificités du site ; installer et mettre en service les équipements de chaîne du froid solaire (système photovoltaïque et équipement réfrigérant) ; diagnostiquer les dysfonctionnements des équipements de la chaîne du froid;  solaire et identifier les conduites à tenir ; diagnostiquer et effectuer des réparations simples sur sites ; former et superviser les agents de santé à l’utilisation et l’entretien courant des équipements de chaîne du froid solaire. Nous vous invitons à vous inscrire ou à faire une large diffusion dudit message après avoir consulté la plaquette de présentation expliquant en détail le programme de formation et les modalités d’inscription. Meilleures salutations !

When to consider solar, based on hours of mains/generator electricity available each day

I’ve been reading with great interest the most recent issue of Vaccine, which is dedicated to “Building Next-Generation Immunization Supply Chains”. I particularly enjoyed the following article but was surprised to read that the authors identified a discrepancy between WHO PQS and Gavi Cold Chain Equipment Optimization Platform guidance relating to solar refrigerators and under what conditions (how many hours of mains/generator electricity are available each day on average) they should be considered for vaccine storage. 'When are solar refrigerators less costly than on-grid refrigerators: A simulation modeling study' The article states: "To effectively maintain an adequate supply of life-saving vaccines in low and middle income countries, where electricity supplies can be capricious [1], the World Health Organization (WHO) currently recommends solar refrigerators for regions with less than four hours of electricity per day, on average, and electric mains-powered ice-lined refrigerators (ILRs) for areas with more reliable electricity [2]. Gavi recommends solar refrigerators for locations with fewer than eight hours of electricity per day or power outages that last more than 48 h [3].
[2] World Health Organization Department of Immunization, Vaccines and Biologicals Quality, Standards and Safety. PQS devices catalogue: prequalified
equipment for the Expanded Programme on Immunization (EPI); 2016 March 11.
[3] Gavi. Cold chain equipment optimisation platform technology guide; February 2016." I went back to the PQS Catalogue and the “Selecting a suitable energy source” graphic on page 35 (this also appears in the WHO-UNICEF solar guidance document). My understanding is that the guidance offered here is in fact the same as Gavi's, in other words solar - in addition to other solutions - should be considered at locations with fewer than eight hours of electricity per day (if the answer to the question "On average, how many hours a day is mains/generator electricity available?" is between 0 and 7). After some thought, I realised that the confusion has probably arisen from the way that solar is presented under the 0-3 box. Under 4-7 it is stated: “Use ice-lined refrigerator* rated 4 hours electricity a day, or consider solar”. However, it seems the “or consider solar” has (understandably) been missed by the authors of the journal article. I don't think this impacts the findings of the article in any way; however, it is worth calling out the discrepancy, as it’s clear that Platform and PQS guidance should be closely aligned if possible (and I think they are). It may be worthwhile to create a new, clearer version of the PQS graphic. I am in discussion with the PQS team in relation to this and hope to update members in future if a new graphic is developed. In summary, for a location with 0 to 7 hours of mains/generator electricity available each day, solar, long-term passive, or liquid petroleum gas solutions should all be considered. And for locations with 4 to 7hours of mains/generator electricity, ice-lined refrigerators rated 4 hours electricity a day should also be considered. Refer to the PQS Devices Catalogue for more information.

New reports on harvesting unused energy from SDD installations

To ensure that solar direct drive (SDD) appliances can keep vaccines at acceptable temperatures continuously, the installed photovoltaic array often produces excess power that is not used by the primary cooling load and this excess power generally goes unutilized. If this power is to be used, the primary SDD appliance load must be prioritized above any other load. WHO and other organizations have been working to define how this can be done safely and reliably. In support of WHO/PQS, PATH has recently posted results from lab testing of a couple of prototype devices intended to do just this. The Solar Electric Light Fund (SELF), organized and provided the prototypes and also carried out initial field tests on this energy harvesting control (EHC) technology. You can access the report here: Additionally, the recently posted PQS specification and verification protocol are available on the WHO website: I would be interested to know - what do people think of this approach with the intent to safely access excess power through EHCs? What do you think could be the most important uses for this power in remote health settings? Thank you, Steven P. Diesburg Product Development Engineer PATH, Seattle, WA, USA

New case studies on SDD vaccine refrigeration projects

WHO and UNICEF have just published a new evidence brief on solar direct-drive (SDD) vaccine refrigerators and freezers. It includes case studies from Tanzania, Colombia and Kenya, as well as an overview of SDD technology and how to make sure that SDD technology is the right choice. Here's the link: This is the document summary: “Solar direct-drive (SDD) refrigerators and freezers can be a good option for vaccine storage in areas without reliable electricity, and many models are now WHO-prequalified. But with little information on SDD field performance currently available, making a case for investing in this new technology can be problematic. This evidence brief provides supply chain managers in low- and middle-income countries with a summary of how recent SDD projects have performed, highlighting problems encountered and the steps that were taken to resolve them. An overview of how SDD technology works, and how to make sure that SDD technology is the right choice, is also provided.” It provides a nice overview of SDD projects, but for those looking for more detailed guidance on how to implement successful solar-powered vaccine refrigerator and freezer systems, I would also recommend the following much longer WHO-UNICEF publication: “Introducing solar-powered vaccine refrigerator and freezer systems - A guide for managers in national immunization programmes” I would be interested to hear the thoughts of other members on the new evidence brief. PS. If you’re looking for more information on other SDD projects, check out at the following forum discussion, which includes contributions from members regarding SDD projects in Somalia, Ethiopia, Malawi, and Rwanda.

Experience about solarchill in Colombia

I like to share with you in this space a video about the instalation, basic maintenance and operation of one of the solar equipments with PQS that are installed in my country (Colombia), nowadays we have 300 equipments in operation.
Best regards

Universal, hybrid refrigerator for vaccines?

Among the TECHNET postings on cold-chain equipment there are embedded remarks pointing towards the need to make vaccine refrigeration simpler and less expensive to procure, more responsive to energy changes and easier to use and maintain. For example, to choose a refrigerator now current WHO, UNICEF and GAVI guides require that you make equipment choices according to energy availability and quality conditions. But in practice, energy availability and quality are changing, they do not remain static over the life of the equipment. The grid may arrive, or it may deteriorate; you may need a standalone refrigerator or one included in solar energy providing for a whole health facility. Solar direct drive refrigerators and Ice-lined refrigerators are starting to share the same design, both using an ‘energy buffer’. Opportunity exists to merge these two refrigerator types in a single model able to run with electrical grid electricity or solar energy or both linked together. Advantages of this hybrid include flexibility for the same refrigerator to adapt to any energy situation, greater production quantities will reduce excessive price differences between the two types and refrigerators are likely to adopt front door opening as the most usable, more compact installed and more efficient at avoiding freezing. Your opinions will be much appreciated to continue this reasoning!

Performance evaluation of solar adsorption cooling systems for vaccine preservation in Sub-Saharan Africa

In case this new article published in Applied Energy is of interest Abstract
An intermittent solar adsorption refrigerator can supply cold needed in third world countries, especially for vaccine and medicine preservation. This paper investigated theoretically the potential of solar adsorption refrigerators in Sub-Saharan Africa. The dynamic behavior of the system and its performance were assessed using real climatic conditions of four Sub-Saharan African sites. A refrigerator operating with activated carbon/methanol as a working pair was simulated using a 1-D mathematical model to investigate its dynamic optimization. The results showed that the best solar coefficient of performance (SCOP) was predicted in Garoua (Cameroon) and Beitbridge (Zimbabwe). The maximum specific cooling power (SCP) was achieved in Beitbridge (Zimbabwe). Under the climate of Lamu (Kenya), the system presented the lowest performance indices.

Error in suggested sizing method for SDD systems

I was recently looking at the “System Sizing tool 3/3” in a 2DI3 “Technical evaluation and Methodology” a unicef publication. The publication originated from a 2DI3 SDD industry meeting. The sizing method prescribed is based on the premise that “the daily potential solar energy supply is calculated as the number of sunshine hours 1000 W/m2 multiplied with the corrected power output.” The compressor of an SDD refrigerator requires about 70 watts to run and start. When the output of the solar array is below 70 watts no useable energy is collected. If for example the refrigerator is connected to a solar array with an actual output (corrected for dust and other losses) of 300 watts the output of the array may not go above 70 watts for a 1.5 hour solar day. From the method in section 3/3 the calculated useable energy collected will be 300 watts x 1.5hr or 450 watt hrs. This result would be correct for a battery based system however zero useable energy would be collected for an SDD system with this sizing method the errors are particularly large when sizing is most critical, during periods of low insolation. Manufacturers apparently know about the failure in this sizing method because the arrays they are incorporating are about 3x larger than the arrays suggested by this method. If any one knows if there is a sizing method for SDD systems currently being suggested by WHO please let me know.

Reorganizing Nigeria’s vaccine supply chain reduces need for additional storage facilities, but more storage is required

Interesting paper on system design in Nigeria from Health Affairs. Abstract One of the major problems facing Nigeria’s vaccine supply chain is the lack of adequate vaccine storage facilities. Despite the introduction of solar-powered refrigerators and the use of new tools to monitor supply levels, this problem persists. Using data on vaccine supply for 2011–14 from Nigeria’s National Primary Health Care Development Agency, we created a simulation model to explore the effects of variance in supply and demand on storage capacity requirements. We focused on the segment of the supply chain that moves vaccines inside Nigeria. Our findings suggest that 55percent more vaccine storage capacity is needed than is currently available. We found that reorganizing the supply chain as proposed by the National Primary Health Care Development Agency could reduce that need to 30percent more storage. Storage requirements varied by region of the country and vaccine type. The Nigerian government may want to consider the differences in storage requirements by region and vaccine type in its proposed reorganization efforts.

Next Generation Supply Chains – A Dialogue with EPI and Child Health Managers

Reposted from JSI's The Pump Jeff Sanderson,Senior Technical Advisor African immunization supply chains need to be transformed. Between 2010 and 2020, new vaccine introductions will quadruple the volume of vaccines per immunized child. The number of vaccine doses that health workers will administer is increasing six-fold. Evidence fromEffective Vaccine Management(EVM) assessments in70 developing countriesfound that in nearly all countries, immunization supply chains are not functioning well enough to ensure vaccine availability and potency and to meet coverage targets. Worse, only a few countries have prioritized supply chain strengthening as a strategy to strengthen immunization program performance. The future of immunization supply chains was the topic of an evening dialogue at the January 25-29, 2016 “Exchange of best practices workshop on Reaching Every Community (REC); Equity and Integration of Child survival interventions in East and Southern African Countries” in Cape Town, South Africa. The key theme of the meeting was to support the increase of coverage for immunization and child survival interventions through the reaching every community/child approach. This evening session, organized by John Snow, Inc. in collaboration with PATH, featured a panel of EPI officials from four African countries that aretransforming their public health supply chainsto accommodate the increasing demands on these supply chains from immunization and other health programs. Each of the four panelists discussed ongoing changes in their country supply chains; their key points are in the full blog post here.

Solar vaccine fridges and freezers - new guidance available

WHO and UNICEF have just released a new joint publication on solar fridges and freezers that is intended to provide managers in national immunization programmes with guidance on how to implement successful solar-powered vaccine refrigerator and freezer systems. It takes into account new developments in refrigerator technology like solar direct-drive (SDD) refrigerators and water-pack freezers, as well as containers with passive cooling, and is based on lessons learned during the 30 years since solar refrigerator systems were first used in immunization programmes. The document is available in English on the WHO website: A French version will be published soon. I would be very interested to hear the thoughts of other TechNet members on this document; please reply to this post with your comments, questions and any other feedback. Is the guidance accurate and appropriate? Is anything missing? Do you know of other resources that might also be useful to those planning to implement solar vaccine refrigerator and freezer systems? To read "reviews" of particular PQS-prequalified solar equipment, as submitted by TechNet members, please visit the the Reviews area of the TechNet website: For example, to read reviews of SDD refrigerators: You can also share your own "real-world" experiences of equipment by clicking "Add new review" for a particular device (you will need to be signed in).Sharing such practical knowledge of these systems with others may, I suspect, be of equal or even greater usefulness than the guidance document itself. I have attached a PDF of "Figure 5. Selecting the most appropriate energy source for vaccine refrigeration" as members also might find this of particular interest/use. This decision tree is an updated version of the one included in Section E003.5 of the WHO PQS Devices Catalogue.

Reviews of the SunDanzer BFRV 55 solar direct-drive refrigerator

Choices, choices, choices – they are both the bane and blessing of our times. As immunization managers, we now have a wide array of PQS-prequalified cold chain equipment to choose from, but how do we make the right choices and get the best value for our bucks? The TechNet Product Reviews area helps you do just that, with users in the field, who are constantly ‘testing’ the product, giving you feedback about the equipment they are using be it refrigerators, thermometers or vaccine carriers. Take, for example, the SunDanzer BFRV 55 DC solar direct-drive refrigerator. Gopal Nadadur from Clinton Health Access Initiative (CHAI) writes, “As is widely acknowledged, improper installations are the cause of a significant percentage of malfunctioning or broken down refrigerators. Easier installation procedures could help to alleviate this problem.” And that is just what CHAI did, ensuring that the manufacturer was kept in the loop, allowing for improvements in product installation. Some of Gopal’s comments have to do with installation while the others recommend changes to the product itself or deal with maintenance. To list some of them: • Visual job aids to assist in routine maintenance and daily usage would be valuable. • The product’s fasteners use the English system of units, all countries where the SDD will be installed use metric sizes. Although the tools are provided with the unit, it would be simpler for all parts to be in metric units if replacement parts need to be procured in country. • Include spare parts of all components needed, especially simple parts that are likely to be easily misplaced (nuts, bolts, screws, etc.). • Could a modified mounting solution be developed for positioning the E-W array at the top convergence of both sides of the roof? This would add greater flexibility to mount on different roof orientations. Note: The manufacturer has accepted this feedback and is working on a solution to this problem. • Constructing the mounting frame of the solar arrays around a pole proved problematic, since some of the fasteners, brackets, nuts, bolts, and screws were confusing to position properly. Need a simpler design and better instructions. Refrigerator • Handles on the side of the refrigerator made carrying it and positioning it in the vaccine storage room easy. • The ON-OFF switch is located in a corner at the back of the fridge. It can be repositioned to be easier to locate. Hamadou Modibo Dicko in his review says that he would “fully recommend this equipment as it has been working well according to agents on the ground”. He lauds the manufacturer’s honesty in informing him that the equipment may not work efficiently at sites that receive heavy rainfall and where the skies are clouded for large parts of the year. However, the staff has had difficulties using all the available baskets at once, and he suggests that the manufacturer should make suitable modifications to this design feature. The third review is from Kshem Prasad, who evaluated the units that were installed in Kenya during 2012. He states that, “most of the models were found having a distorted ice-lining, which is factory installed with some gel compound into the unit. Most likely, it is suspected that the plastic deformation of the ice lining on the 4 walls, occurred during the storage and transport in the container, during which the units were exposed to temperatures higher than expected.” The deformation has compromised efficient cooling and interferes with proper placement of the baskets. The UNICEF SD has communicated these limitations to the manufacturer and the latter is expected to come up with a solution in its new models. You can read the detailed reviews of the product here: You can also comment on the reviews above or submit your own review:

A New Solar Hybrid Refrigerator/Freezer

Sun Frost developed a hybrid refrigerator/ice pack freezer, the FRH-3. The Sun Frost FRH-3 has a SDD freezer and a battery powered refrigerator. The SDD freezer is the same size as our F-1 ( and incorporates the same technology which allows the freezer to operate at low levels of insolation. The F-1 has been successfully tested in Colombia this past year. Testing was supported by the BMG Foundation. The refrigerator has a net storage capacity of 32 liters and is battery powered. The refrigerator compartment is extremely efficient at 32 deg C, it consumes only 96 watt hours/day or 8 amp hours/day at 12 volts. The FRH-3 can be powered by two 140 watt module’s at any location in the tropics. The cooling systems are independent and one module will be connected to each cooling system. A 140 watt module will provide enough energy to run the refrigerator section with only 1 KWH/m^2/day. At poor solar locations in the tropics levels of insolation at or below 1 KWH/m^2/day may occur once or twice a year. This is based on the examination of many years of data on the WRDC data base ( We primarily looked at locations with low levels of insolation. At this level of energy consumption for 363 days per year the battery will have to supply only 4 amp hours/day to keep the refrigerator operating at night. For one or two days per year the load will be 8 amp hours. In terms of the Autonomy Tool the array oversize factor will be at least 3.5; an array oversize factor of 1.25 is all that has been required by WHO. Using a larger oversize factor greatly reduces the necessary storage capacity of the battery and also reduces the amount the battery is discharged. In a conventional battery powered combination unit the freezer is also battery powered. The freezer is a major part of the load, and this load could vary considerably depending on the quantity of ice manufactured. Eliminating the freezer load significantly reduces the amp hour draw on the batteries. In addition the efficiency of the refrigerator was increased by incorporating a newly developed evaporator. A battery as small as 40 amp hours would typically be cycled only 10% each day; each night 4 amp hours will be used to keep the refrigerator operating. The expected life of a battery is highly dependent on the percent discharged. Data for MK Battery DEKA gel cell shows that the cycle life of a battery increases from 600 cycles to 6000 cycles as the percent discharged decreases from 80% to 10%. We expect the life of a high quality battery to be at least 10 years. If the battery is replaced by a lower quality locally available battery in this shallow cycle application we expect the life of the battery to be at least 3 years. A 40 amp hour battery is about the size of a small car battery. Loss of battery capacity is typical mode of failure for a battery, however, even if a 40 amp hour battery loses 80% of its capacity it will continue to operate the refrigerator. Advantages of a Hybrid System: - System is sized to operate at any location in the tropics. Sizing is typically a problem with SDD refrigerators. From the PQS Sheets “For solar direct drive units, the correct sizing of the solar panel array for a specific site is complex and critical. It must be agreed with both the appliance manufacturer and with the Qualified Supplier of the solar energy system at the time of ordering.” - The system will be considerably less expensive than an SDD refrigerator/freezer. In a poor solar location the savings could be as much as 40%. - The refrigerator and power system will be smaller and easier to transport than a SDD refrigerator/freezer. - Connection will be plug and play. - Since the panel powering the refrigerator is significantly oversized the battery will typically be full early in the day. Excess power could than be used to power a second battery which could be used for lights or cell phone charging, etc. Typically 24 amp hours or 288 watt hours will be available for other applications. This could light eight 5 watt LEDs (40 watt incandescent equivalent) for 7 hours each day. - In emergency situations where a spare battery is needed the auxiliary battery could be used to run the refrigerator. A spare battery will then always be available. Sincerely, Larry Schlussler, Ph.D. Sun Frost

Solar power in health: What’s your story?

Success has many fathers, failure is an orphan. Yet, we can learn so much more from failure than successes. The amazing safety of modern flight is a result of this systems-based analysis of failures. In contrast, medical safety continues poorly with a culture of 'blame' focusing on individuals rather than systems diagnosis – and cure! As reported in the April 2012 issue of GIN, the CCLT is aiming to support efforts to accelerate solarization of the cold chain, with benefits for the planet as well as children who live in places with no reliable power source – except the sun. We know that there have been many failures of solar-powered fridges in the past. We know that maintenance of the battery and solar panel theft have been two important causes of failure. We also heard that underestimated budgets and human aversion to change can give a bad name to good technology. But we need to learn more. Contribute to the safe flight of solar power and tell your story of its failure. What was the project and where did it go wrong? What did you learn from it? Send your contributions to Dmitri Davydov at UNICEF ( and you will hear from us.

Implementing the solar cool chain successfully

With many thanks to John Lloyd for this post. Countries that currently use absorption refrigeration (gas, electric or kerosene-powered) are facing increasing pressure to switch to solar photovoltaic-powered refrigeration for vaccine as manufacture of absorption equipment shrinks. We have a substantial evidence from the field on the success of solar refrigeration systems that point to a few critical success factors: ? Systems designed rigorously to match climatic and irradiation, site-specific data ? Installation following standard procedures and quality norms of WHO ? Commitment and budgeting for routine maintenance (including battery replacement) and timely repair The stakeholders of immunization are the lead position to assure systematic procedures in the field, thus assuring future success. Plans are in process for a major new field assessment of solar ‘direct drive’ refrigerators (four models that do not depend on battery systems) that have already been prequalified by WHO/PQS. Procurement by countries will proceed in parallel to this assessment and pending the results the following criteria for successful implementation of solar refrigeration should be pursued: • Solar refrigeration is now the preferred option where grid electricity is not available or is available less than 4 hours per day and where sufficient solar radiation exists to permit a reliable and affordable system design (See figure 1) ? Kerosene/electric absorption options for areas without electricity have a lower performance, are less reliable and more costly to operate then solar refrigerators ? Direct drive solar refrigerators are more reliable than battery based solar refrigerators because they rely less on battery systems and have simpler control equipment and have less electrical connections ? No direct drive solar refrigerators available at this time include icepack freezers, so they are only suitable where water packs or Phase Change Materials (PCM) packs are used for outreach immunization – or where there is no outreach immunization • Solar refrigerators should be selected from the WHO/PQS list of pre-qualified products and the Qualified Suppliers responsible for supply and contractors/technicians (could be MOH techs) responsible for installation should conform to WHO/PQS (ref) norms. The process of procurement and installation should include the following main steps: ? Identify appropriate sites GPS data (country desk study) o No prolonged cloud (> 1 week continuous) o No shading between 9AM and 3PM o Electricity less than 4-8 hours / day o Solar technical service is, or can be, available ? System design (solar technician site visit) o Review climate data for temperature, solar radiation and to determine autonomy needed o Site visit to determine shading, panel support structure, fridge location, cable routing, etc. ? Documents assembled for open tender: o System design documents (technician) o Site visit reports (technician) o Installation procedures o Maintenance and repair plan and commitment ? Bidding and adjudication o Technical review bidding documentation o Send out request for bids to Qualified Suppliers. o Technical review of bids to ensure appropriate specifications proposed. o Award, installation and acceptance • Resources will be needed to follow the process described above including: ? Technical staff or consultants, training: o to visit each candidate site for solar PV refrigerators and collect data o to assemble system design briefing documents for tender o to install or supervise installation of solar PV equipment ? Guide materials: o WHO PQS solar refrigeration (E3) documents o Refrigerator manual in appropriate language o Copy of the Markvart system design tool ? Multi-year Plan: o Budgeting, maintenance and repair of solar refrigerators ? Need for consultants, training, guide materials, software tools etc. Figure 1: Decision chart for selection of power source for vaccine refrigeration equipment: (Please click on the image for a bigger picture.)

Solar Cold Chain Training

Compressor Replacement Without a Vacuum Pump

Compressor Replacement Without a Vacuum Pump

Replacement of a compressor requires the use of a vacuum pump. Solar
powered vaccine refrigerators are generally located away from the
utility grid. Most vacuum pumps are powered by AC grid power making
compressor replacement difficult. We have developed a method of
removing the air from a system without the use of a vacuum pump. The
method requires the installation of an access valve on the high and
low side of the system.

Evacuation Procedure

1 - With the new compressor installed, turn on the compressor and
depress the access valve on the high side of the system. Monitor the
pressure on the low side of the system. When the pressure is as low
as it will go, close the access valve on the high side of the system
and turn off the compressor. This process will take about 5 minutes.
2 - Charge the low side of the system to approximately 14 psi.
3 - Wait about 3 minutes for the pressures on the high and low side
to equalize.
4 - Now turn the compressor on and depress the access valve on the
high side. When the pressure on the low side is as low as it will go,
let the high side access valve close and turn off the compressor.
5 - Repeat steps 2, 3 and 4. Note, on successive evacuations, the low
side pressure will not go as low because of the absorption of
refrigerant in the compressor oil and it’s slow release.
6 - Charge the low side of the system to approximately 14 psi.
7 - Wait 3 minutes for the pressure to equalize. Turn on the
compressor and depress the access valve on the high side. This time,
when gas is no longer coming out the high side access valve, let the
valve close. The air is now purged from the system.
8 - Charge the system with the appropriate amount of refrigerant and
turn on the compressor.
9 - Make appropriate adjustments in system charge if necessary.

Target service life for vaccine refrigerators

What service life do you think vaccine refrigerators should be able to provide? For example, some products may suggest a 10 year life while others suggest longer, with typical repairs. PQS requires a 2 year warranty for a vaccine fridge.
Solar powered vaccine fridge systems require solar electric modules (minimum 20 year warranty is typical and 20 year is required by PQS). Most also have batteries (5 year warranty per PQS).
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