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398
Medical Laboratory Technology: Volume 1
method of Blood collection
Blood collection as specimens for various laboratory tests has been described in Chapter 5.
Here we shall focus on the blood collected for transfusion therapy.
Blood coagulates after it is taken out of circulation. Hence, an anticoagulant is added to
prevent cloing. Most commonly used anticoagulant in the blood bank is acid–citrate–dextrose
(ACD solution) or citrate-phosphate-dextrose (CPD). Citrate prevents coagulation by
removing ionized calcium and glucose
provides the red cells with necessary energy in
order to prolong their viability. Acid–citrate–
dextrose-preserved blood is suitable to use for
at least 21 days after donation, provided it is
stored continuously at 1–6°C. Some solutions
(e.g., adenine) allow the blood to be used until
42 days.
Blood is drawn using aseptic technique
by trained personnel (Figure 16.3). As most
blood donations are voluntary it is essential
that the procedure be as pleasant, safe and
convenient as possible. This helps to recruit
new donors and continued participation of
current donors.
Figure 16.3 Donation of blood
Use of Disposable Plastic Bags
Disposable plastic bags for blood collection have now totally replaced the old glass boles
(Figures 16.4 and 16.5). The glass boles were dicult to wash and did not meet blood
bank requirements. They also broke easily and created biohazards. Today’s plastic bags are
Figure 16.4 (a) Modern blood collecting plastic bags, (b) Satellite bags are used for separating blood
components. The primary bag (a) contains the anticoagulant (and additives) and is used
for both blood collection and blood transfusion. During blood collection, lters may be
attached to reduce the number of white cells in donor’s blood. The entry ports (a) are
used to connect to the recipient or satellite bags.
Collection and Processing of Blood for Transfusion
399
commercially prepared, sterilized and lled with
appropriate amount of anticoagulant-preservative
solution. These are ideal for preparing blood
components. In addition, they are light, take up
less space, and are non-breakable and disposable.
The bag expands during blood collection and
hence does not require any air-venting system
during blood taking or giving.
As the bag is directly connected to the bloodcollection set, the risk of bacterial contamination
is extremely low. However, defective plastic bags
occasionally can cause contamination and the
blood collection agencies could not pinpoint the
cause. In addition, the chemical composition of
bags used can vary widely without government
regulation. As a result, any pyrogenic reaction
was dicult to trace back from batch to batch
supply of bags. These issues have largely
been corrected in many countries. Current
manufacturers of the plastic bags for blood
collection strictly follow international guidelines
for the chemical composition of the bag and its
added anticoagulant and preservative. They also
print out the identication number on each bag
Figure 16.5 Bag for blood collection
so that collection agencies can immediately trace
back each bag used in blood collection and supplied to the
hospital. In that way defective bags as well as a defective
lot of bags are withdrawn from the market and appropriate
corrective action is implemented.
Blood is collected under aseptic conditions by
venepuncture from a large vein in the arm, usually the
cephalic vein (Figure 16.6), after sterilizing the puncture
site. Approximately 450 mL of blood is collected into a
sterile closed bag containing a citrated anticoagulant. This
process takes approximately 10–20 min. A small portion of
the blood remains in sealed, segmented tubing external to
the sterile unit. Each tubing segment is coded to match the
code on the blood bag. The blood in these tubing segments
is used for various tests so that unit sterility is maintained
until it is transfused. At the time of donation, blood is also
collected into separate tube(s) without anticoagulant to be
used for typing donor blood and other screening tests.
Figure 16.6 Major veins of
the arm: Median
cephalic is the
vein of choice
Preparation for Blood Drawing
Iodophor compounds or other sterilizing compounds are used to sterilize the venepuncture
site before blood collection. Before starting to draw the blood, see that the required materials
are available:
• Supplies for venepuncture: Tourniquet; forceps; strippers; adhesive tape; rubber band.
• Equipment to measure blood pressure.
400
Medical Laboratory Technology: Volume 1
• Scrub solution: Disposable povidone–iodine scrubs 0.75% or disposable povidone—
iodine swab stick 10%; available in pre-packaged single-use form. These disposable
supplies may not be available locally. Follow local laboratory policy.
• Preparation solution: 10% povidone–iodine; available in pre-packaged single-use form.
Follow local laboratory policy.
• Blood collection bag: Properly labelled sterile blood collection bag with donor’s
identication number. Always inspect the bag for any defect. The bag must have the
required anticoagulant, with integrally aached tubing and needle. The tubing leads to
16 gauge intake needle with cover.
• Metal clips and hand sealers.
• Balance system to monitor volume of blood drawn.
• Sterile gauze and clean instruments (scissors, haemostats, forceps).
• Test tubes for sample collection (often aached to the disposable blood collection bags).
• Device for stripping blood in the tubing.
• Dielectric sealer (optional).
Special Note All equipment for the procedure should be prepared in advance or at least
be easily accessible to the phlebotomist. This brings condence in the donor and makes the
process more professional.
Procedure
1. Identify the donor and compare it with the donor’s record. If necessary, ask the donor
to spell the name and conrm his or her identication.
2. Ask the donor to lie on the bleeding table. Make sure the donor is relaxed and comfortable.
Place the blood collection bag approximately 30 to 40 cm below the level of the bleeding
table. Since many individuals are afraid of venepuncture, it is important that the
procedure be performed quickly, eciently and with an aitude of professionalism.
Caution Under no circumstances should the subject be standing or siing on a high
stool during the process of blood collection because of the possibility of fainting.
3. Ensure that all labelling on blood container, processing tubes, retention segment and
donor records is correct.
4. When identication is completed, apply the tourniquet to the upper arm when the
vein may become prominent. The tourniquet should be tight enough to be slightly
uncomfortable (but not painful) to the donor. When it is securely in place, ask the donor
to make a tight st. This makes the veins more easily palpable. A blood pressure cu
inated to 50–60 mm Hg may also be used.
5. Choose the site of venepuncture. The three major veins of the arm are the cephalic,
median cephalic and median basilica (Figure 16.6). While all the three are suitable for
venepuncture, the median cephalic is usually the vein of choice because in most cases it
is well anchored in tissue and will not move when punctured; unlike the median basilica
vein, which has a tendency to move in many donors. The cephalic vein is generally not
the rst choice because it is located on the outer part of the arm where the skin tends to
be lile tougher. Using the left index nger, palpate the arm until the best vein, which
should feel similar to an elastic tube, is found. (Note: Be sure that you cannot feel a pulse,
as this indicates that the vessel is an artery and not a vein.) Having the donor make a st
is usually helpful in making the veins more prominent.
Special Note In some cases, it is almost impossible to locate a vein in one arm, although
there may be a suitable one in the other arm. It is a good general practice to check both
arms in every case unless large good veins are found, in which case the choice of which
arm to use may be left to the patient.
Collection and Processing of Blood for Transfusion
401
6. Arm preparation for blood collection: Detailed instructions are specic to each
manufacturer of blood collection supply and should be followed as indicated. The
following procedure is followed in most Red Cross blood collection agencies (AABB
Manual, 15th Ed):
• Scrub the area at least 4 cm in all directions from the intended site of venepuncture
(i.e., 8 cm in diameter) for a minimum of 30 s with 0.7% aqueous solution of iodophor
compound. Excess foam may be removed; however, the arm need not be dry before
the next step.
• Starting at the intended site of venepuncture and moving outwards in a concentric
spiral, apply ‘prep’ solution; let stand for 30 s or as indicated by manufacturer.
• Cover the area with dry, sterile gauze until the time of venepuncture. After the skin
has been prepared, it must not be touched again. Do not re-palpate the vein at the
intended venepuncture site.
Notes
• For donors sensitive to iodine (tincture or povidone preparations), another
method (e.g., Chloraprep—2% Chlorhexidine and 70% isopropyl alcohol) should
be designated by the blood bank physician. Do not use Green Soap.
• For donors sensitive to both iodine and Chlorhexidine, a method using only
isopropyl alcohol could be considered. The preferred procedure is the use of a
30-second up-and-down scrub, followed by enough time for the skin to dry. A
second scrub is then applied.
7. Make sure that the skin is dry before inserting the needle in the following step. Many
technicians prefer to release the tourniquet before disinfecting the puncture area and
apply it again.
8. When ready, uncover the sterile needle (16 gauge) and perform venepuncture
immediately. Anchor the needle and tubing with an adhesive tape. Cover the needle at
its entry point with dry sterile gauze.
Note Venepuncture hole for blood donation is considerably bigger ( 16 gauge needle)
than used during blood specimen collection for laboratory testing (20 to 22 gauge).
9. Release any temporary closure in the tubing to allow the blood to ow freely into the
bag (Figure 16.7). Gently agitate the bag to mix blood with the anticoagulant. Mix
periodically (approximately every 45 s) during collection. Mixing can be done by hand
or by continuous mechanical mixing.
Figure 16.7 Blood collection procedure: (a) Perform venepuncture, (b) Allow the blood to collect
in the collection bag placed on a balance with mixing capability, (c) Ask the patient to
squeeze a hard object in the palm in order to facilitate the ow of blood
402
Medical Laboratory Technology: Volume 1
10. Have the donor open and close his or her hand, squeezing a rubber ball or other resilient
object slowly and continuously during donation.
11. Be sure that blood ow remains fairly brisk, so that coagulation activity is not triggered.
If there is continuous adequate blood ow and constant agitation, rigid time limits are
not necessary. However, units requiring more than 15 min to draw may not be suitable
for preparation of platelets, fresh frozen plasma or cryoprecipitate.
12. The ow should be stopped when the weight of the bag is between 425 to 520 grams.
Note The above weight does not include the weight of the container and its anticoagulant,
which must be compensated for.
13. When the required volume of blood has been collected (about 450 ± 45 mL) stop the
blood ow by clamping the tubing,
using a haemostat, metal clip or other
temporary clamp. The chosen site is
about 8 cm from the needle.
14. Grasp the tubing on the donor side of
this seal, press to remove the blood or
a distance of no more than 2 cm, clamp
with a haemostat and cut the tubing
between the seal and the haemostat
(Figure 16.8).
15. Fill the processing tube for laboratory
tests by releasing the haemostat and
allowing the blood to ow directly
from the vein. Ensure that all tubes are
Figure 16.8 Haemostat
properly identied with the bag.
16. Release the blood pressure cu/tourniquet to 20 mm Hg or less and ll the tube(s) by a
method that prevents contamination of the contents of the bag.
17. Deate the cu and remove the tourniquet. Remove the needle from the donor’s arm, if
not already removed.
18. Apply pressure to the phlebotomy site using sterile, dry gauze (the donor might assist
by holding the gauze in place with the other hand.) Discard the needle into a special
sharps container to prevent accidental contamination to personnel.
19. Strip donor tubing, forcing the blood back into the bag; invert the bag several times to
ensure thorough mixing and then allow the tubing to rell with anticoagulated blood
from the bag.
20. Seal tubing into segments suitable for compatibility testing using knots, metal clips or
a dielectric sealer. Make a double seal about 5 cm from the bag to allow segments to be
separated from the container without breaking the sterility of the container.
21. Finally, re-inspect the bag for defects. Recheck all the identity numbers on bag,
processing tubes and donor record. Complete donor’s record and put your initial on the
bag and on the record book (Table 16.1, Figure 16.5).
22. Do not let the donor stand up immediately after blood donation. Make sure that any
bleeding from the venepuncture has stopped (Figure 16.3). Cover the wound with a
dressing. Give a lile time (5 to 10 min) for the donor to adjust to the loss of blood. Ask
the donor rst to sit up and then get o the table and stand up. Occasionally, the donor
might show signs of fainting; let the donor lie down for a while more until he/she feels
comfortable.
23. Give the donor uids and some sort of oral nutrition. He should be encouraged to drink
a lile extra water or other uids during the next several hours.
24. Store the blood at 1–6°C. If the blood is collected in the eld (outside the laboratory), use
ice packs and send the blood promptly to the blood bank.
Collection and Processing of Blood for Transfusion
25. If platelets are to be harvested from the donated blood, it should be maintained at room
temperature (20–24°C) until platelets are separated. This must be completed by no more
than 4 h after donation is complete.
403
Adverse Reactions of Donor
Donor reactions are rare; yet when they do occur, personnel must be prepared to recognize
and treat such reaction without delay. Typical donor reactions include:
• Dizziness
• Fainting
• Weakness
• Excessive perspiration
• Pallor
• Nausea
• Occasionally, donors may have convulsions, loss of consciousness or involuntary bowel
or urinary passage.
• Haematoma
Phlebotomist’s Response
At the rst sign of adverse reaction, the phlebotomist should stop the bleeding process and
remove the donor to an isolated area for privacy. Summon the blood bank physician without
any delay. Call for ambulance or emergency unit if cardiac arrest is suspected. In case of
apparent fainting, ask the donor to lie down with raised feet above the level of the head (i.e.,
Trendelenburg position). Loosen the clothing and ensure the donor has an adequate airway.
Administer aromatic spirits of ammonia by inhalation. (Note: Do not hold the vial too close
to the nose). Apply a small cold wet towel on the forehead or the back of the neck. Check and
record the blood pressure, pulse and respirations periodically until the donor recovers. If the
donor complains of vomiting sensation, have the emesis basin ready along with a wet towel.
Turn the donor’s head to the side in order to avoid any aspiration. Donor showing muscular
spasms or convulsions should be allowed to lie on the oor and any nearby hard objects
should be removed. If symptoms of hyperventilation are seen, divert the donor’s aention by
engaging in conversation or have the donor rebreathe into a paper bag. Do not give oxygen.
In case of haematoma, remove the tourniquet and needle from the donor’s arm. Place
three or four sterile gauze squares over the haematoma and apply rm pressure for 7–10
min with donor’s arm held above the level of the heart. You may apply ice if it comforts
the donor. Serious cardiac diculties are extremely rare. If they occur, call immediately for
an emergency care unit and begin cardiopulmonary resuscitation immediately and continue
until the emergency medical aids arrive.
Note All adverse reactions occurring during or after blood donation must be recorded on
donor’s register and on the special incident form of the blood bank along with an explanation
of the treatment given. This should include a note as to whether the donor should be accepted
for future donations.
Basic Laboratory Tests
If blood is collected in the eld without laboratory facilities, it should be transported as soon
as possible to the laboratory where storing facilities are available. Collected blood should
always be kept between 1–6 °C unless platelets will be produced from the donation. (This
is further discussed in the following section). Donor’s blood, after collection, is subjected
to ABO blood grouping and Rh typing in the laboratory and the result is displayed on the
label aached to the blood bag (Figure 16.5). This helps in the preliminary choice of the blood
which undergoes more rigorous compatibility testing. Compatibility testing is done only
404
Medical Laboratory Technology: Volume 1
near the recipient’s (patient’s) location. The laboratory also performs weak D testing, and if
positive, the blood is reported as Rh+.
The laboratory also tests the blood to be free from blood-borne diseases. This includes HIV
(human immunodeciency virus), hepatitis and other sexually transmied diseases (STDs).
The liver enzymes (alanine aminotransferase, ALT) should be within the normal range. In an
emergency situation, blood may be transfused before the completion of these tests; however, a
notation to the eect that testing is not completed must appear conspicuously on the aached
label or tag. If any test is subsequently found to be reactive, the recipient’s physician should
be notied immediately. The details of these tests are given in other sections of this book.
tranSportation of Blood after collection
Following the collection of blood, it is important
that the blood is kept between 1–6°C (Figure
16.9). Cold temperature prolongs the viability
of the red blood cells (RBCs). Care should be
exerted so as not to allow cells to freeze, as
this causes lysis. A temperature of 4°C (±2°)
is considered to be ideal but this is dicult to
maintain during transportation. To maintain the
required temperature, place the material in wet
ice in a waterproof container (plastic bag) placed
in sturdy, well-insulated cardboard or plastic
shipping containers (e.g., polystyrene). The
insulated boxes need to be made of lightweight
but durable material to facilitate movement, to
minimize transport costs and to guard against
damage in transit.
The cooling material (ice) should be kept
above the container containing blood. This
is done in order to take advantage of the
downward movement of cool air. Considering
the hot weather of India and other developing
countries, during long hot trips it is advisable to
keep the ice and the blood unit in direct contact
with each other. In very hot weather, the ice may
be placed both above and below the blood units.
Any air space or a layer of cardboard between ice
and blood bole might act as internal insulation,
preventing the ice from adequately protecting the blood from high atmospheric temperature.
Wet ice from a commercial ice-making company is commonly used for short distance
travel, but cubed ice is considered to be beer than chipped ice for long-distance shipments
because it melts more slowly. The volume of ice and blood should be equal, especially when
long-distance shipping or high environmental temperatures are involved.
With proper insulation and care in transport, cases containing blood can be kept in a cold
room (i.e., below 10°C) for at least 12 h and possibly over 24 h depending on the ambient
temperature. No containers should have a capacity of more than 10 units; anything larger
becomes too heavy and bulky for convenient handling.
After the blood has arrived at the laboratory, it is safer to check the temperature by keeping
a thermometer between the blood collection units. If the temperature of blood is above 10°C,
it should not be stored but may be released for immediate use if advised by the supervisor.
Figure 16.9 The ow of blood from donor
to the recipient
Collection and Processing of Blood for Transfusion
Always discard haemolysed blood. Never leave the blood at room temperature for a
prolonged period. Donor’s blood is precious and should not be wasted due to negligence.
People handling the transportation of blood should be made aware of any problems. Good
organization and team work are necessary to reduce mishandling of donor blood.
The problem of blood transportation is not only a maer of concern between the blood
collection point and the blood bank but also within the hospital. There is a time gap between
the issue of blood or its components and initiating the transfusion to the patient. During
this period, the blood is most often kept at room temperature, which varies widely during
dierent seasons.
The transit condition within the hospital must also be controlled and properly monitored
by the blood bank in collaboration with other hospital services. The unused blood should be
returned promptly to the blood bank no later than 30 min because blood stored at 2°C–6°C
warms up to 10°C or above in approximately 30 min at room temperature. In hot weather,
the time between the issue of blood and the return of the unused blood should be further
reduced.
405
Storage of Blood
Blood anticoagulated with ACD or CPD and refrigerated between 2–4°C can be stored for
21 days. With the addition of adenine to the anticoagulant (ACDA, acid-citrate-dextroseadenine), the blood can be stored for 35 days instead of 21 days. With the addition of an
additive solution, red cell units can be stored for up to 42 days. The use of adenine is not
common in the developing countries due to its non-availability.
Blood may be stored in walk-in cold rooms, in free-standing, reach-in refrigerated cabinets or
in refrigerators on vehicles. The installation requirements of walk-in cold rooms and reach-in
refrigerators are identical. The refrigerator should maintain a temperature between 2° and 4°C.
A blower circulates the air so that the same temperature is maintained through the refrigerated
space. A dial-type thermometer indicating the air temperature within the refrigerator should
be placed in a prominent position. There should be an audible and visible alarm system that
gives the earliest possible indication of any undesirable change in the air temperature (above
6°C), whether this be due to electrical or mechanical failure or a careless act of keeping the
refrigerator door open. The air temperature uctuates more rapidly than the uid (blood)
stored in containers. Hence the alarm gives sucient time to protect the blood.
The alarm system should not be connected to the electrical system. A baery-operated alarm
system is recommended. It is desirable to extend the alarm indicator from the laboratory to
some place likely to be staed at all times (e.g., the security oce or a telephone switchboard).
A permanent record of the actual storage temperature of the blood is necessary. This
is done by placing a standard bole with 500 mL of water within the refrigerator and by
immersing a sensor (thermocouple or thermometer bulb) in the water. The sensor is linked to
a continuous recording chart to trace the temperature. A seven-day circular chart is preferred
to a strip chart (daily) so that the variations can be compared, at a glance, over several days.
The recorder should have an independent power supply from the refrigerator and should be
mounted on an adjoining wall not subject to any vibration.
All the free-standing blood storage refrigerators should be wired back to a fuse box or
distribution board in a permanent way and should not be connected with a switched outlet.
This precaution is taken in order to avoid accidental switching o of the refrigerator’s power
supply. It is also important that the alarm system aached to the blood bank refrigerator be
checked periodically to ascertain that it is functioning properly. One of the ways to check
it, is to warm up the sensing device with warm water. The alarm should function when the
temperature reaches 6°C. Similarly, cool the sensing device by dipping it in chipped ice, and
the alarm should sound when the temperature goes below 1°C.
406
Medical Laboratory Technology: Volume 1
Organization in storage
Refrigerators in the blood bank must be properly organized. There should be separate areas
(or separate refrigerators) for the following groups:
1. Unprocessed blood: Blood recently collected from donor and is waiting for ABO blood
grouping and Rh-typing.
2. Processed blood: This is the group of collected blood whose blood group and blood
type have been determined and is available for cross-matching. Separate shelves or
areas may be labelled for blood of dierent groups.
3. Cross-matched blood: This group of blood has been cross-matched with the respective
patient (recipient) for whom the blood was requested. It is now waiting for delivery.
Each blood collection container must bear the identication of the recipient and the
pilot tubes (or vials) have been separated and stored for future use in case of transfusion
reaction.
4. Rejected blood: This is the group of outdated or quarantined blood and is waiting for
disposal.
Changes in stored blood (storage lesions)
• The viability of red cells decreases during storage.
• Approximately one-third of the coagulation factor VIII activity decreases in 48 h.
• Platelets lose their functional ability.
• Potassium concentration in plasma increases during storage due to release of intracellular
cations.
• The pH of plasma decreases and the diphosphoglycerate (DPG) level declines.
common equipment in a Blood Bank
Collected blood must be carefully protected before it is used. Any failure in storing the blood
and its components under proper conditions compromises their integrity. Except platelets,
most other components of blood should be stored at cold temperatures and connected to an
alarm system. In case of emergency, alternate methods of storage must be put in use.
Refrigerators and Freezers
The basic dierence between a refrigerator and a freezer is that the refrigerator keeps things
above freezing while the freezers hold things below freezing (0°C). Usually freezers hold
frozen plasma and its various components, while refrigerators hold the whole blood. Red
cells cannot be frozen unless it is especially processed. Platelets tend to agglutinate at low
temperature and hence they are kept at room temperature under constant agitation. Blood
refrigerators and freezers rely on refrigeration systems. The following are ideal features
common to both:
• Audio-visual alarms: Temperature out of range, door ajar and warning for power
failure with baery back-up.
• Temperature display unit at 0.1 °C graduation.
• Continuous temperature recorder: Seven-day chart with baery back-up.
• Roll-out type of drawers or trays.
• Stainless steel construction (recommended).
Upright refrigerators
Blood bank refrigerators are usually of ‘upright type’ with glass doors. This is because they
are frequently opened to place or retrieve blood packs. It is useful to have the blood packs
Collection and Processing of Blood for Transfusion
displayed so that the blood group and date of expiry can be identied without opening the
door. Blood bank refrigerators generally have a cooling fan to ensure air circulation within
the cabinet.
407
Chest refrigerators
Ice-lined and solar powered refrigerators are of the chest type and have a cooling fan to ensure
air circulation within the cabinet. Ice-lined refrigerators are designed to achieve a relatively
longer hold-over temperature because they are used in locations that experience frequent and
lengthy power cuts. Solar-powered equipment needs heavier insulation because the energy
source may be unreliable. Furthermore, the chest type refrigerator is not ideal for the placing
or retrieving of blood packs because baskets have to be lifted out completely.
Upright freezers
The general construction of an upright freezer is very similar to the blood bank refrigerator.
The insulation is heavier so that temperature of –35°C or colder can be maintained. An upright
freezer takes up less space but is not as ecient as the chest type, because every time the door
is opened, air inside escapes at the boom of the opening and moisture enters with the air.
This can be minimized by having solid shelves to hold components and fan air cooling which
automatically stops when the door is opened, thus reducing air exchange with that from the
outside.
Chest freezers
The most common and ecient design of freezers is the chest type, for several reasons. Since
chest freezers are opened less frequently than the upright version, they maintain desired
temperatures beer. They also stop a considerable amount of moisture from entering the
cabinet, since cold air does not spill out when the lid is opened as it is heavier than warm air
(the door is referred to as the lid). However, it is sometimes dicult to gain access to frozen
products near the boom of the chest freezer, despite the assistance of ed baskets that can
be lifted out.
Ice-lined refrigerators
Ice-lined compression type refrigerators are designed for environments where the national
grid electricity power supply is unreliable. Ice-lined refrigerators are usually of the ‘chest
type’ and are especially designed to have a long hold-over time. This means that, unlike
standard electric refrigerators, they may hold the temperature below 10°C for up to 17 h
following a power cut. The ice lining consists of plastic tubes or other containers lled with
water that is frozen during operation. They may also have a freezer section for the storage
of ice packs. During periods of power failure and load shedding, the ice packs act as cold
storage to protect units of blood in the refrigerator. The freezer section is approved for the
freezing of ice packs, but not for the storage of plasma products.
Solar or photovoltaic refrigerators
Solar- or photovoltaic-powered compression refrigerators convert solar energy into Direct
Current (DC), as an alternative source of electricity to the mains supply. The major dierence
from standard electric refrigerators is that the insulation of the cabinet is higher so that the
hold-over time is at least 24 h. Baeries store the electrical energy during daylight. In the event
of disconnection from solar panels or poor sunlight, baeries continue to provide electricity,
thus adding to the hold-over time. Only WHO approved companies should provide the solar
panels and related accessories. This ensures that the design of panels suits the energy needs