TechNet-21 - Forum

  1. Dan Brigden
  2. Supply chain and logistics
  3. Friday, 28 April 2017

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.

Attachments (1)
Accepted Answer Pending Moderation

Hi Dan,

When the availability of electricity per day is less than 24 hours, or when power cuts per month is greater than 30 hours, it is preferable to use solar panels or absorption. This is because the electronic thermostat of the ILR is very sensitive to voltage variations. If power cuts occur and suddenly come back, this instability creates faults in the thermostat relay and the temperature falls below 0°C quickly, which leads the vaccine gets freezing.

I have seen this situation in places where the grid quality is not good, the voltage is low and it does not matter if a voltage regulator is connected, another cause of failure is not to connect the ground line. Sometimes the power of the voltage regulator is less than 1,500 VA and when the LRA occurs the fuse is blown.

  1. more than a month ago
  2. Supply chain and logistics
  3. # 1
  • Page :
  • 1

There are no replies made for this post yet.
Be one of the first to reply to this post!