TechNet-21 - Forum

This forum provides a place for members to ask questions, share experiences, coordinate activities, and discuss recent developments in immunization.
  1. Steven P. Diesburg
  2. Cold chain equipment
  3. Friday, 07 April 2017

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

Dear all

The new health center kit of B Medical or any device designed to take advantage of the excess power of the solar panels is an excellent option. In this moment we are doing the installation process of 37 SDD (17 units TCW40 SDD, 14 units VLS024 SDD and 6 units Sure Chill Godrej GVR 50 DC SDD). All of them have compressor BD35K Danfoss, and the nominal power in solar panels are between 400 and 500 watts, the compressor has a power input of 35 Watts at -18°C. In this sense, lanterns, or power outlets is amazing in those zones.

Best regards

  1. more than a month ago
  2. Cold chain equipment
  3. # 1
Christopher Morgan Accepted Answer

Thanks very much to Gilles, Murat, and Steven for these updates - very helpful information I can pass on to our NGO partners in the Pacific.

  1. more than a month ago
  2. Cold chain equipment
  3. # 2
Gilles Ries Accepted Answer

Good morning All

Interesting discussion coming up again. Truely, this is an area of wide interest and possibilities.

At Bmedical, we have already designed and developped a so called HCK (health center kit). The HCK can be coupled with any of our SDD refrigerators, and does provide enough power to charge on a daily basis:

2 LED laternas, each of them providing then light for 35h

2 standard smart phones

operate a 5W fan during 8h

provide up to 20W power through a standard 12V cigarette lighter socket

The device has gone through and passed lab testing according to PQS specifications and is currently field tested in Nigeria. Field testing is expected to be complete by end of April, and we expect a PQS to be ready by end of June / beginning of July. The feedback so far has been very positive.

It is true that users are in bad need of power for their phones in order to keep up communication. For a fact their is GSM coverage but no electricity to charge the phone batteries. The need is equally important for lights, during the nights in the labour rooms. And a small fan, even though this is far away from an AC, was very welcome as well. It is today possible to provide those basic needs from excess energy of the PV array feeding the SDD refrigerators. It is difficult though to "guarantee" daily excess power to more sophisticated medical equipment, as this would for sure require extra PV / battery installation.

A super side effect of the HCK is to see users taking better care of their fridge / solar array since they are now entitled to charge their phones. Knwoing that charging the phone will only work if their SDD installation is kept up well, the HCK gets them to do the basic maintenance effectively.

Here is the link to more information :

Attached also a picture of the installed kit

I am happy to reply to any questions


Attachments (1)
  1. more than a month ago
  2. Cold chain equipment
  3. # 3
Murat Hakan Ozturk Accepted Answer

Dear Chris,

Greetings from Fiji. As UNICEF Pacific, we have been exploring variuous options on providing solar technologies for healthcare centers around the Pacific. 

Especially after the Tropical Cyclone Winston in Fiji, solar direct drive refrigerators along with power packs were our main focus.

There are also some other options (based on energy harvesting concept) we are currently piloting and please don't hesitate to reach us for more information:

Best Regards,



  1. more than a month ago
  2. Cold chain equipment
  3. # 4
Steven P. Diesburg Accepted Answer

Hello Chris,

I do have some general updates and can ask around (and check-in with Pat Lennon who leads this work at PATH) and see if I can find any more detailed information. In terms of PATH's progress on this, we are still solidifying plans and funding for more field implementation trials to provide more evidence-base for EHCs in general. We're also in communication with the WHO/PQS about how to support EHCs moving through pre-qualification and into the market. Although no stand-alone EHCs or EHCs integrated into refrigeration appliances have gone through PQS pre-qualification to date, multiple manufacturers are at different levels of considering, designing, and building-out appliances including an EHC.

Acknowledging that the developments are somewhat slow, I agree with you that lighting and phone charging can be extremely important. We are also hoping that other important health uses and collateral benefits will become evident when the technology is taken up. There is energy being produced and left unused and I hope that we can push this forward sooner rather than later!

Thanks for the post,



  1. more than a month ago
  2. Cold chain equipment
  3. # 5
Christopher Morgan Accepted Answer


I wonder if there is any update on the potential for Solar Direct Drive installations to provide solar power for other uses.  We have been asked for advice for remote facilities in Pacific Island nations where standard solar is being installed for lighting and mobile phone recharging - both seen of similar importance as refrigerator functions.  At present it seems to them that the only option is to use non-SDD refrigeration if they want to get the benefits of more general use of solar power.

  1. more than a month ago
  2. Cold chain equipment
  3. # 6

Dear Steven P. Diesburg

I am totally agree with this inniciative. I always have believed that the cold chain in a far away community is compused by vaccines for humans and animals and medicines and laboratory reactives, etc. If in a Health Center could be possible to install a PV array with the capacity to energize the lights, the refrigerators and the computers, the compressor for odontology, all of this would be amazing. It does not matter if some of these equipments need battery and charge controller to work, because the PV is the general power source.

This will take save money and efforts for to do individuals projects, and the community will see improving your life quality.

Best regards

  1. more than a month ago
  2. Cold chain equipment
  3. # 7

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