The study, development and experimental investigation of a novel, solar powered refrigeration system based on the jet-pump cycle

Every year, millions of people die from diseases that are preventable by vaccination. The
lack of an effective cold-chain in developing countries means that many of the
vaccinations intended for administration are spoiled and wasted. Poor energy
infrastructure in these countries is often coupled with high solar irradiance values,
providing a compelling reason for research into effective solar powered refrigeration
systems.
A number of studies have shown that a refrigeration system, thermally powered via a
jet-pump circuit, as an alternative to an electrically driven compressor, could provide a
working solution. Such a system could be powered largely by heat (i.e. solar energy) and
would find application in developing countries with high solar availability. A
comparative review of prior research into small scale jet-pump refrigeration systems
highlighted a gap in existing knowledge as the performance of small scale units (<500W)
has not previously been investigated.
A system specification was defined, based on current World Health Organisation (WHO)
standards for solar-powered vaccine refrigerators. A jet-pump, rated to deliver 100 W evaporator cooling capacity using R134a as a working fluid, was developed and tested at
the defined operating conditions (Te=6°C, Tg=90°C and Tc=42°C). The experimental
study focused on the need for technology that is suited to off-grid applications and the
use of secondary heat sinks (i.e. cooling water circuits) was avoided. Alternatives to an
electrically powered refrigerant feed pump were investigated and a novel reservoir
transfer system is presented and experimentally evaluated. In order to minimise moving
parts, the use of natural convection heat transfer (i.e no fans) was also investigated for
both the evaporator and condenser heat exchangers. Automated systems were used to
control the apparatus and experimental data collected to evaluate the systems thermal
coefficient of performance (COP).
Experimental results showed that the system could achieve COPs of 0.06 - 0.12 and
demonstrates the potential for small capacity jet-pump cooling systems using less than
50 W electrical power.