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 SDD

SDD freezers that maintain -10C and below

Hello, I am brand new to TechNet-21 so this will be my first posting.  I am trying to find an SDD (Solar Direct Drive) freezer which will maintain -10C and below. The product I need to store in Nigeria is surfactant (injected into the lungs of premature babies with collapsed lungs to give them life) which must be kept at that cold temperature to maintain a shelf life of 3 years. The electricity supply throughout the country in Nigeria is erratic and undependable, thus I would like to install an SDD freezer with a distributer (in Lagos) which would be independent of grid power. Surfactant is a very high value and low volume product so a smaller (50-100 liters) SDD freezer would be ideal. My understanding is the freezers designed for freezing ice packs may not maintain -10C and colder thoughout a 24 hour cycle which includes night. The only other solar option I am aware of is to revert back to older technology that relies on solar charged batteries to either operate a 12 or 24 volt DC freezer of use an inverter to power an AC powered freezer. I was hoping to eliminate the weak link in the system, the battery. To date I have not been able to identify an SDD freezer among the mainline manufacturers -- Dulas, SunDanzer, SureChill, Vestfrost, Haier. Thanks for any advice! Dave

WHO PQS Manufacturer Consultation Report

Dear TechNet Community, On Tuesday 10th July 2018, the WHO Performance, Quality and Safety (PQS) Working Group conducted its first face-to-face technical consultation with manufacturers of PQS prequalified immunization products and devices from the E003 (Refrigerators and freezers) and E006 (Temperature Monitoring Devices) equipment categories - some of you may also have followed the event in real time via the TechNet-21 Twitter account. Thirty industry representatives took part in the meeting, alongside ten non-industry members and partners of the WHO PQS Working Group, to discuss and agree on a path forward for some significant proposed changes to immunization cold chain equipment standards. The PQS Manufacturer Consultation proved to be a highly successful first step towards greater collaboration with manufacturers on PQS standards-review and standards-setting processes. In particular it provided manufacturers with greater visibility on in-country realities and complexities and helped solicit industry insights and inputs on technical and product solutions to meet varying challenges in EPI program environments. More insights on the themes covered during the meeting as well as key discussion points and meeting outcomes have been provided in the PQS Manufacturer Consultation Report. The report can be accessed in the TechNet Library by clicking on the following link: https://www.technet-21.org/en/library/main/4926.  Enjoy the read! On behalf of the PQS Team,  Denise 

SPOTLIGHT: Installation of SDD Refrigerators in Colombia

Dear TechNet-21 communty, I would like share with you some pictures of the installation process of 37 SDD that we are doing in Colombia. Best regards.

Total Cost of Ownership (TCO) tool version 1.4 available now

We are happy to announce the latest version of the Total Cost of Ownership tool for cold chain equipment (v1.4) is now available to download and use. If you have been using an earlier version of the tool, please download the latest version from the link below.   Version 1.4 includes filters for CCEOP eligible equipment, as well as filters for refrigerator/freezer combination devices.  The latest version of the TCO tool contains PQS pre-qualified equipment as of May 2017. Please download the latest version (in English or French) for the most up to date products and pricing. http://www.path.org/publications/detail.php?i=2576  If you have any questions or would like any training/demos please email Matt Morio mmorio@path.org

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: http://www.path.org/publications/detail.php?i=2699 Additionally, the recently posted PQS specification and verification protocol are available on the WHO website: http://apps.who.int/immunization_standards/vaccine_quality/pqs_catalogue/catdocumentation.aspx?id_cat=36 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: http://www.who.int/immunization/documents/general/WHO_IVB_17.01 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”
http://www.who.int/immunization/documents/9789241509862 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. http://www.technet-21.org/en/forums/looking-for-more-information-on-sdd-vaccine-refrigerator-performance-in-the-field

Looking for more information on SDD vaccine refrigerator performance in the field

Dear TechNet members, I'm putting together a document on the performance of solar direct-drive (SDD) vaccine refrigerators and would like to request your assistance. If you have experience of SDD projects in the field I would be very grateful if you could share your thoughts on how well they have performed (particularly in relation to other types of vaccine refrigerator), problems that were encountered, solutions identified, and any other observations you might have.
More than 20 SDDs are now WHO PQS-prequalified, and many of these are eligible for funding as part of the GaviCold Chain Equipment Optimisation Platform. It's an exciting technology that has the potential to be a "game-changer" for immunization programs, as iteliminates the need for expensive/problematic energy storage batteries used to power solar refrigerators. However, with all new technologies it is uncertain how well suited it is for use in "the real world" outside of the laboratory.
As part of Project Optimize, PATH and WHO worked with ministries of health in in Vietnam and Senegal toconduct some SDD pilot studies, but this was five years ago. I've also heard that CHAI have been doing some work in this area, but don't think they have yet published their experiences. I wonder if TechNet members can share any more recent experiences with these devices? Both good and bad!
Many thanks.

La version française de l’outil de calcul du Coût Total de Possession (CTP) d’équipements de la chaîne du froid est maintenant disponible.

Outil de calcul du Coût Total de Possession d’équipements de la chaîne du froid
L’outil de calcul du Coût Total de Possession (CTP) d’équipements de la chaîne du froid a été développé afin d’assister les utilisateurs dans leur compréhension du coût d’achat et de maintenance des équipements de la chaîne du froid. L’outil peut être personnalisé pays par pays et calcule les dépenses en capital et en coûts d’opération pour les équipements préqualifié par le département Qualité et Sécurité de l’Organisation Mondiale de la Santé.
Pour accéder le CTP cliquez ici: https://www.path.org/publications/detail.php?i=2576

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!

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.

PATH’s cold chain equipment Total Cost of Ownership tool now available

PATH’s Total Cost of Ownership (TCO) tool for cold chain equipment is now available for download and use. The TCO tool is designed to help countries compare and understand the costs associated with the purchase, installation, and ongoing operation of cold chain equipment. The tool currently covers 82 cold chain equipment devices including all 72 PQS (Performance, Quality and Safety) prequalified devices from the E001 (cold rooms and freezer rooms), E003 (refrigerators and freezers), and the long-term passive devices under E004 (cold box and vaccine carriers) categories. Using local country costs such as labor and energy rates, the TCO tool calculates costs for purchasing and operating cold chain equipment over time through multiple views such as: cost over useful life, cost per liter of storage, and recurring operational costs. Additionally, the tool can incorporate facility segmentation requirements to match equipment and country needs. These features not only allow users to understand cost differentials of one technology versus another (absorption gas refrigerator versus solar direct–drive refrigerator), but they also provide the ability to drill down and compare costs on a model by model basis over a user-defined horizon from 1 to 20 years. The TCO tool can be downloaded from PATH via the following link: https://www.path.org/publications/detail.php?i=2576. After downloading, please check back regularly to ensure you have the latest version/updates. A large thank you to all who have contributed to our efforts developing the tool. The total cost of ownership tool for cold chain equipment was made possible with support from the Bill & Melinda Gates Foundation. Please send any questions or comments to Matt Morio mmorio@path.org.

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: http://www.who.int/immunization/documents/9789241509862 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: http://www.technet-21.org/en/reviews For example, to read reviews of SDD refrigerators: http://www.technet-21.org/en/refrigerators-and-freezers/solar-direct-drive-refrigerators-with-without-ancillary-battery 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.

Considering a Max/Min range for Vaccine Storage Capacity in refrigerators

The percent difference between the gross refrigerator (ILRs and SDDs) volumes quoted in the PQS Catalogue and the net vaccine storage volume varies from 29.6% to 88.6 %. This is a wide variation for front opening fridges, due to space for air-circulation. Increasingly, new models of ILR and SDD are emerging with cooled internal walls and cooled ceilings. Some of these models maintain a satisfactory internal temperature distribution whether they are packed according to the test procedure (with air spaces) or when the vaccine load fills the whole gross volume (without air spaces). The impact of this finding is that the storage capacity of a new model of ILR or SDD may be double or even treble the catalogue figure. The difference in capacity at intermediate levels of storage in-country will affect the economic decision to procure a cold room or maintain a bank of ILRs or SDDs. Running costs will be affected. Cold-chain equipment planners be made aware of this issue when they choose new equipment and when they re-equip stores. What about these next steps – just my own suggestion? we maintain the method of loading by the test laboratories that uses 1.0 and 0.5Lt. boxes and we maintain the 'net vaccine storage capacity' measured by the laboratory. But I suggest that this parameter be titled 'Minimum vaccine storage capacity'. we maintain the manufacturer's gross capacity, but we add a 'Maximum vaccine storage capacity' that is measured by the laboratory as the maximum vaccine load (represented by the dummy load) without airspaces, without baskets or shelves IF this extra loading step is done (Optional, requested by client) then: ◦ the Maximum vaccine storage capacity is reported by the lab. and entered in the catalogue ◦ the rest of the testing that requires a dummy load would be loaded according to the Maximum capacity IF it is not done, the Maximum capacity will be the same as the minimum and the Minimum capacity will be loaded for the rest of the testing. the country clients for cold chain equipment would be informed that the laboratory reports generate a range of capacity (Min./Max) for each refrigerator and that, within this range and according to the vaccines they use, the country managers can choose a value for the Vaccine storage capacity in that country. The consequence of this approach is that ILRs and SDDs with satisfactory temperature disitribution performance even when fully loaded, will be more efficiently loaded, less numerous in larger stores and less energy and space consuming. Usually, this would result in lower cost of procurent and maintenance. Also, the coldchain manager has an opportunity, even an obligation, to check the capacity that he/she will use when equipping stores to better correspond to the vaccines in use. Finally, if an equipment model requires airspaces to assure a correct temperature range, then the manufacturer does not invoke the additional measuremnt during testing - the dummy vaccine load simply reverts to the current procedure.

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 (http://www.sunfrost.com/batteryless_direct_drive_freezer.html) 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 (http://wrdc-mgo.nrel.gov/). 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

Are SDD refrigerators solutions or challenge in solution for the low resources countries?

The decision of a National Immunization Programme to use Solar Direct Driven (SDD) Refrigerators instead of Solar Panels to run refrigerators I think is like presenting challenges in the so called expected “better and sustainable solution” especially for the low resources countries. It is true that, SDD are compressor powered directly from the sunlight (they are really environmental friendly) and therefore does not need additional running costs for batteries which in other way these batteries are” less environmental friendly”. The other field tested facts is that, they are more efficient in maintain the temperature between +2 to + 8 degree Celsius than the absorption types where freezing can occur due to temperature excursion on the lower side especially in cold climate areas. This seem to be better solution, However the challenge remains that, they have no application for lighting and therefore the temperature cannot monitored/recorded in dark rooms and or at night. Lighting is very important, this could be provided in using solar panel instead of SDD, one will benefit with improved curative (and delivery) services at night, I understand major problem is home deliveries and maternal deaths; Improved data transmission using phone for health initiative, I believe data transmission and quality remains to be major problem; improved human resources for health by ensuring lighting for health workers houses and even security in the health facility, I believe shortage of skilled staff and equity in distribution of few available health workers is also a problem. I therefore think, solar panels installation, is more supportive for health system rather than the SDD which are primary immunization delivery centered intervention, thinking as health system strengthening intervention. More challenge is the fact that, even some of SDD have been per-qualified and within short period removed from ore-qualification, thinking of no recovery of damage. When purchasing SDD one should consider, the vaccine volume, costs, climatic condition and autonomy/safety margin for ensure no temperature excursion. However, a major issue on the spare parts which may not be a problem on using panel is extremely important. My question still remains, is SDD solution or a challenge in solution for the low resources countries? No right no wrong answers, but we need to have better decision making for the limited resources.

SDD Ice Pack Freezer: High Demand – Successfully Field Tested – Unavailable

Two solar direct drive ice pack freezers have been successfully tested for seven months in Columbia. The F-1 was manufactured by Sun Frost and a second freezer was produced by Sun Danzer. The freezers were tested by Steve McCarney of SELF and the project was supported by BMGF grant. The tests results were highly successful: To quote Denis Marie the performance of the units was “beyond user expectations”. F-1 Runs at Low Light Levels The Sun Frost F-1 incorporates some unique technology which we call the Power Block. The Power Block allows the compressor to run at low light levels. Typically with a SDD refrigerator or freezer the compressor will not run if the output of the solar array is less than approximately 60 watts. As a consequence, the solar array is typically over sized so that the compressor can run during periods of low insolation. The Power Block is also helpful on sunny days as well as cloudy days because it allows the compressor to run closer to sunrise and sunset, as a result there are more hours per day for ice making. In Columbia the Sun Frost F-1 was powered by a single 180 watt module. A relatively small 135 watt module would be adequate in most locations. Ice Packs are Pre-Conditioned with SDD Freezers Water packs typically freeze during the day, and overnight the temperature of the ice packs will rise. The next morning most of the ice packs will typically contain a small quantity of water while some may be totally frozen. A valuable feature of SDD freezers is that the ice packs containing water will be completely conditioned. The temperature of the ice packs which are totally frozen will be close to 0 deg C and require minimal conditioning. The temperature of the freezer could be adjusted so that all the packs are conditioned the next morning. The partially melted ice packs will typically contain only about 10% water. The health care workers will have to judge how many ice packs to take partially based on the percent of ice in each ice pack. Field Tests are of High Value There are a number of design flaws which may not show up in a lab test but will become evident in a field tests. One example is moisture problems, there have been SDD refrigerators which have successfully passed PQS testing but have serious condensation problems in the field. Another example is one model of an electronic unit for a Danfoss compressor, it would continually try to start at low light levels and burn out. The electronics problem was resolved by Danfoss, yet, it never showed up in lab tests. Another example pointed out on the Tech Net 21 website, the unexplained expansion of containers holding phase change material. An SDD freezer could possibly have problems with ice accumulation or expansion which may not show up in a lab test. Problems such as these did not show up in the field tests. Tests Comparison Refrigerator Versus Freezer With SDD freezers, unlike refrigerators, their performance can be easily evaluated by visually looking at the ice packs in the morning and judging the net ice production. Temperature measured during the day would be of little value to the end user, unlike a refrigerator where too high or too low a temperature could effect the efficacy of the vaccines. With a vaccine storage refrigerator if unusually poor solar weather is encountered the vaccines could be lost if the system was not properly sized. Under very poor solar conditions a likely consequence with a SDD freezer is that there will not be the extra energy available to freeze new ice packs, however, there may be enough output from the array to keep stored ice packs cold. Fortunately even in the unlikely event that the freezer would not run at all and the ice was lost the weather would probably be so bad that the outreach program would be rescheduled. Unlike the operation of an SDD refrigerator vaccine efficacy is not compromised by a weather related change in the freezers performance. High Demand, No PQS There is currently a high demand for SDD ice pack freezers, thousands will be needed in Nigeria. However there are no PQS standards and no PQS approved freezers available. I suggest that SDD freezers that have been field tested by a reputable testing organization have their availability published along with other PQS approved products. They would also need some type of WHO approval so that they can be purchased with support from major donors. If information on SDD freezers is not made readily available SDD freezers with proven performance will not make there way into the cold chain where they are needed. Larry Schlussler, Ph.D. Sun Frost

PQS sheets: Solar refrigeration

The data given for solar-powered refrigerators in the PQS sheets is not given consistently enough so that comparisons of various models can be made. The data needed for a fair comparison most often is energy consumption at 32 deg C without ice making, energy use with ice making and quantity of ice made. It would also be useful to know the number of days of autonomy time for direct-drive refrigerators. Looking at the PQS sheets it is not always clear how to obtain total energy consumption when refrigerator and freezer consumption are given separately. Perhaps it should state whether or not it is a two compressor model and if the refrigerator and freezer consumption should be added together to obtain the total energy consumption. Another confusing point on the PQS sheets is that the solar radiation reference period is often given without energy consumption data or recommended solar array size. Without this information the radiation reference period has little meaning. There are few places in the world where average daily temperatures are over 32 deg C. It is important to know if afternoon temperatures peak at 43 deg C that the vaccines will be safely stored and remain between 2 deg C and 8 deg C. However, the average ambient temperature will probably be at 32 deg C or below and the stable running consumption at 32 deg C will be used for system sizing. The latest data I received for a direct drive refrigerator E003/037, for example, gives no energy consumption at any temperatures or any recommendations on a array sizing, it does however give the solar radiation reference period, which alone would be no help judging efficiency or in sizing a system. When the compressor for this model (E003/037) was switched to an AC model so that it could be transformed into an ice lined refrigerator (E003/036) for some reason stable run energy consumption at 43 deg C was given in addition the cool down energy consumption was listed. If the pertinent data is not consistently published there is no incentive for a manufacture to build a more efficient product and no way for a buyer to make an intelligent purchasing decision. I hope the PQS sheets can be transformed into a more useful document.

Direct-drive freezer operates at low levels of isolation

Sun Frost has been building vaccine storage refrigerators for the past 20 years. Sun Frost is now building a direct-drive ice pack freezer. Some new technologies incorporated into the design allows the freezer to run even at very low light levels. On a cloudy day if the output of the PV array is less than about 60 watts the compressor in a direct drive system will not start. The Sun Frost F-1 will run on cloudy days even if the output of the solar array is minimal. On a sunny day the number of run hours will be increased because the F-1 will run closer to sunrise and sunset leaving less night time hours for the ice to melt. On a standard poor solar day (3.5 KWH/m^2/day) the Sun Frost F-1 will freeze about 3 kg of ice by sunset while being powered by a 140 watt PV module. Some of the ice will melt overnight giving a net production of 2.4 kg. If these partially froze ice packs are left in for a second day they will be cooled well below 0 deg C by sunset. The following morning the coolth stored in the sub-cooled ice packs will keep them from thawing. Another major advantage of running at low levels of isolation is that performance on marginal solar days can be predicated using total daily solar data rather than hourly data. What makes sizing direct drive refrigerators difficult in developing countries is that this data is typically not available hence the comment in 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” Steve McCarney at Solar Electric Light Fund (SELF) is currently running long term tests on the F-1 in Columbia. Preliminary results look good. (attachment) Contact Sun Frost for more information. Larry Schlussler, PhD (Engineer and owner of Sun Frost) PQS-F1.pdf

Approach for extensive field monitoring of solar generator

Hi, I would greatly appreciate your expert opinion on a technical question regarding extensive field monitoring of solar generator. The objective is to carry out a long-term, rather in-depth field monitoring of solar (DD) fridge installations for their long-term performance evaluation and programmatic learning about their operations- hence only a subset of all solar units would be monitored. To monitor and evaluate a solar generator, the basic set up should probably track the solar exposure at the panel site with a pyranometer and the electrical output of the solar generator (should it be best voltage? intensity? power? a combination? is there a specific location where it should be measured?). Any related protocol or recommendation for specific data logger brand or toolkit is welcome. Secondly, I am also wondering whether there are any other valuable elements to monitor, either as performance indicators of the solar generator or as key environmental factors that could impact the solar generator performance. For example, I wonder whether it is valuable to monitor the ambient temperature of the solar panel , or the temperature of the panel itself. I anticipate those complementary measurements might only be insightful in case of unexpected performance or issue as it might help identify the causes of the unexpected situation. Looking forward to your thoughts, Yann

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.)

Refrigerator/Ice Pack Freezer or Refrigerator Only

Recently, I have seen a number of relatively large RFQ’s for direct drive refrigerators. These refrigerators do not have an ice pack freezer. From past feed back from our customers and WHO we have heard that ice packs are necessary to distribute vaccines to more remote areas. We are concerned that these remote clinics may not be getting a refrigerator, which fits all their needs. We would like to get feed back on this point.

The Battery-Free Solar Refrigerator Challenge

by Joanie Robertson, Technical Officer, PATH

In March 2009, six companies submitted designs to PATH in response to its Battery-Free Solar Refrigerator Challenge. Product designs that meet desired specifications will receive financial assistance to cover the cost of third-party testing required for consideration under the World Health Organization's Product Quality and Service (PQS) process.

The purpose of the Battery-Free Solar Refrigerator Challenge is to encourage the development of new products in the solar refrigeration category for use in developing-country immunization programs. Solar-powered refrigerators are an attractive alternative to gas- and kerosene-powered absorption devices: they are environmentally sound, provide an alternative to grid electricity where it is unreliable, and can be produced affordably. However, most existing solar refrigerator products are inadequately designed to meet the needs of developing-country immunization programs. The main issues relate to the lack of or inappropriate replacements for exhausted batteries, inappropriate system sizing, and poor installation work.

The Battery-Free Solar Refrigerator Challenge is designed to help address the first of those issues. By providing clear specifications to known solar refrigerator manufacturers and helping facilitate the PQS testing and submission process, Optimize hopes to reduce some of the market barriers and spur innovation and growth in this important refrigeration category.
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