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:
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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
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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
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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.)