Monday, 23 December 2019
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Dear TechNet community,

Poor power conditions are a major challenge to maintaining the vaccine cold chain in many LMICs, necessitating the development of specialized CCE such as ILRs and SDD refrigerators to help keep vaccines at safe temperatures in areas with limited or no mains power.  Even in places with an electrical grid connection or a generator, intermittent power can lead to ILRs running out of holdover, and erratic voltages can damage many types of medical devices and equipment.

Despite these well-known issues, to date, data on power conditions in LMIC health facilities have been largely anecdotal or small-scale, which impedes evidence-based policymaking.  To quantify power availability and quality challenges, Global Good – in close partnership with Nigeria’s National Primary Health Care Development Agency (NPHCDA) and Kenya’s National Vaccines and Immunization Program (NVIP) – has compiled an analysis of mains power data reported over nearly 18 months by WHO-prequalified ILRs operating in health facilities across Nigeria and Kenya.  We are sharing this analysis in hopes of informing tangible improvements in both the performance and reliability of mains-powered CCE, as well as other priority medical devices and equipment utilized in health facilities within LMICs.

This analysis, co-authored by NPHCDA and NVIP officials, is based on approximately 96,000 facility-days of mains power data collected over a nearly 18-month period from ILRs operating in more than 300 health facilities spanning both countries.  These power data and other information collected by the ILRs belong to the respective countries; Global Good has been granted access to the data to enable collaboration with pertinent national and global stakeholders on tools to better utilize CCE data and make it actionable.  This overview of grid quality realities on the ground shows that multi-day interruptions are common, and that proper protection for medical equipment is essential given the widely varying line voltages experienced at most health facilities.  

The initial analysis in this paper focuses on general power availability and quality at health facilities, with a few specific implications for CCE at those facilities including:

  • 68% of the monitored devices in Kenya and 92% of those in Nigeria experienced power outages in excess of 48 hours. Therefore, long holdover times provide additional safety, even at those facilities with generally reliable mains power.
  • Voltages fluctuate significantly, and stabilization can increase the ‘usable power’ availability at many health facilities – only 32% of the devices in Nigeria had access to in-range power (i.e., within 10% of nominal voltage) more than 30% of the time. However, with PQS-defined extended range voltage stabilization (i.e., 110 to 278 V), 58% of devices would have access to ‘usable power’ more than 30% of the time.
  • Damaging high voltage events are common and can persist for hours or days – the graphs below show example voltage profiles from Kenya and Nigeria that would require protection between the socket and CCE (or other medical devices and equipment) to prevent damage to the electronic controls over time. These traces show data measured every 10 seconds, illustrating sustained voltages both above 400 V and below 100 V, and rapid fluctuations in and out of the CCE’s usable voltage range.



Additional graphics and discussion are in the full document, and Global Good will continue analyzing data and sharing conclusions as more information is collected. 

We hope this analysis will prove valuable for specifications- and standards-setting bodies, equipment designers and equipment purchasers, and we look forward to a vibrant discussion with the TechNet-21 community via this forum.

We wish to acknowledge and extend our sincere appreciation to NPHCDA and NVIP for supporting and co-authoring this analysis.  We also want to acknowledge Qingdao Aucma Global Medical Co. for producing the WHO-prequalified ILRs that collected the study data, and eHealth Africa, Caroga Pharma Kenya Ltd, and Fenlab Ltd. for installation and service support in the two countries.

The document is also availble here: 


Best regards,

Jenny Hu

Senior Engineering Lead

Global Good

4 years ago

Evidence base prompts changes to global policy for vaccine refrigerators

A month ago a document titled Power Quality Challenges in LMICs - Data and Analysis was posted here on Technet Forum. Unfortunately, there has not been much feedback.  I am disappointed in the lack of discussion because in my view this study presents findings which support changes in global policy for vaccine refrigerators. The paper presents data from two representative countries on the availability and quality of electric power that are major determinants of the performance of vaccine refrigerators. The data suggest that, in both countries, the variability and intermittent supply of electric power indicates that three features are needed, universally to assure continuous, correct refrigerated storage:

  • Holdover passive cooling 
  • Integral voltage stabilizers
  • Remote temperature and power monitoring

Consider these three issues as a basis for discussion.


Hold-over passive cooling

The period of ‘safe’ vaccine storage when power is interrupted is boosted for vaccine storage by an ‘ice-lining’ that is charged with cooling when power supply is on or when sun is shining and then provides cooling when the power is cut. The data show that interruptions of the grid supply are variable and unpredictable. So a universal policy to provide a holdover of 120 hours might replace the current standards. The holdover capacity in hours remaining could be displayed on the refrigerator to inform the user of the security of stored vaccines.


Integral voltage stabilizers

Voltage stabilizers markedly increased the percent of usable electricity supply in all refrigerators monitored during the study, both those with widely varying voltages and those with frequent variations. At present, stabilizers may be supplied as separate accessories ‘bundled’ with refrigerator purchase or they may be provided within the refrigerator product. Incorporating stabilizers universally into vaccine refrigerators could benefit repair and maintenance and would assure that sensors were correctly installed,

Remote monitoring of temperature and power

The paper describes the system of power recording that was adopted in this study. Analysis of this data has, for the first time in over 30 years, informed manufacturers, vaccine managers and international stakeholders. Power data, when used in conjunction with temperature alarm data and vaccine management should be routinely monitored by an LMIS. The collection, transmission, analysis and dissemination of information by countries should become universal.


The WHO PQS Specification Working Group might plan a discussion on the implications of this paper for the future of a universal vaccine refrigerator specification for all countries. The benefits of a universal vaccine refrigerator might be:

  • A single simple standard for all vaccine refrigerators
    • Rejecton of domestic refrigerators
    • Hybrid use of solar and grid electricity 
  • Oversight of the implementation by National Regulatory Authorities
  • Larger market, concentrated on a single universal standard
    • Better prices
    • More manufacturer interest
4 years ago

John, thanks for the comments!

Our goal with this paper was to provide information to various stakeholders to inform evidence-based policy and decision making.  Some of the obvious areas where this data can directly affect deployment decisions and specifications are holdover time and voltage protection/stabilization – how often is additional holdover needed to prevent temperature excursions? What voltage range is most beneficial?  What kinds of electrical events need to be protected against?

We’re doing some additional analysis to help address those questions and will have more results to share soon.  Even with clear data showing outage lengths and voltage histograms, more input and debate will be needed to balance technical benefits with manufacturer constraints and country implementation logistics and get to the specification changes that John mentioned.  We welcome feedback from the TechNet-21 community on the data and their implications for CCE.

4 years ago

Thank you, Jenny, for sharing the report and John for the comments.  These are very useful. We look forward that WHO PQS team and vaccine refrigerator manufacturers will consider these data for the improvement and development of existing and future cold chain equipment. Other LMICs may have the same problems but were not documented.  Hope similar study will be extended to other LMICs.  

Please find a summary table of some important aspects mentioned in the report and comments namely: 1) power supply source, 2) voltage stabilization, 3) refrigeration system, 4) holdover, and 5) temperature monitoring.   Remarks and commentsmay be used for improvement and development of future vaccine refrigeration equipment.

Power supply source 

Voltage stabilization

Refrigeration system

Holdover (Passive cooling)

Temperature monitoring


1. On-grid

a) within ±10% of nominal value

Not required but useful if installed

Electric compression using digital inverter compressor

ILR with at least 120 hours holdover

30 DTR


WHO PQS compliant refrigerators and freezers have varied holdover at different vaccine storage capacity.  Holdover to at least 120 hours will ensure vaccine protection when power supply becomes intermittent.

Almost all designs of vaccine refrigerators/freezers are electric compression with the following features: 

*single speed, 

*start and stop at preset thermostat setting.

*need high starting current to start motor

*noisy operation

Latest electric compressor design has the following features:

*digital inverter 

*multi speed *compressor does not stop but adjust its speed based on heat load requirements. No need for frequent start and stop of motor compressor 

*upfront cost is high but can be recovered by savings in electricity

*quiet operation

b) fluctuating voltages

Extended voltage stabilizers

Digital inverter compressor

ILR with at least 120 hours holdover

30 DTR 


Same remarks/ comments as above

c) extreme voltages: low (undervoltage) and high (overvoltage) 

Voltage stabilizers to automatically shut off

Refrigerant compressor and electronic control automatically shut off

ILR with at least 120 hours holdover

30 DTR

Voltage stabilizers and compressor to shut off at extreme conditions to prevent damage to both

2. SDD

Not required

Digital inverter compressor or purely 12/24V DC compressor

SDD with at least 5 days autonomy 

30 DTR

Continuous operation during daytime but switch off at night

3. Hybrid 

a) electricity (with fluctuating voltages) and SDD

Extended voltage stabilizers

Single digital inverter compressor 

ILR with at least 120 hours holdover

30 DTR

Electricity (AC) and Solar (DC) goes to the grid to power the digital inverter compressor.

b) electricity (with fluctuating voltages) and SDD

Extended voltage stabilizers

Dual compressors with dual refrigeration system

ILR with at least 120 hours holdover and SDD with at least 5 days autonomy 

30 DTR

At nighttime digital inverter compressor will operate.

At daytime when electricity is fluctuating SDD will operate.

4. Both power sources are not available

Not applicable

Not applicable

Use freeze free cold boxes with cold life of at least 30 days

30 DTR

Freeze tag

Replacement of melted icepacks has to be done on regular basis

Hope these are useful.  

Alejo H. Bejemino


Cold chain and Vaccine Management

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