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Alejo Bejemino replied to a discussion, Power Quality Challenges in LMICs - Data and AnalysisThank 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
Remarks/Comments
1. On-grid
a) within ±10% of nominal value
Not required but useful if installed
Electric...
MoreThank 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
Remarks/Comments
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
RMTD
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
RMTD
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
Consultant
Cold chain and Vaccine Management
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