TREND AND APPLICATIONS OF ABSORPTION CHILLER
Sea Group
B.C. Chung - Century Corporation, Korea
1. INTRODUCTION
Since human being's desire for comfortable environment is
instinctive, demand for HVAC increasingly grows as one's increases. Therefore
propagation of air-conditioning facility is highly enlarged in countries which
have been achieving economic growth. At present, most of the popular chillers
as large tonnage of air conditioners are electrically driven. These electric
chillers, which work perfectly under sufficient power supply, are causing
a great deal of problems when the electric power condition is poor. In this
area, the electric chiller is not proper to carry out varying cooling load
according to the seasonal changes a peak load in some seasons and a partial
load in other seasons. The electrically driven chiller have some problems
something like this. In this case, the electric power condition can be improved
by replacing the electric chiller system with those which use different types
of energy, which is relatively sufficient compared with electricity. In general,
when there is a peak load for air conditioning in a building, about 20% of
the total electric power consumption is due to the air-conditioning system. Furthermore, electric chillers consume 70%
out of the 20%, which amounts to 14% of total electric power consumption.
Therefore it is required to substitution these electric chillers to non-electric
ones to cope with an electric power shortage. A representative of non-electric
chiller is an absorption type. The absorption chiller consumes only 5∼10%
electric power compare with an electric chiller, as auxiliary power and power
for control. The main energy can be used several kind of heat source, for
instance gas fuel, liquid fuel, steam, hot water, solar heat, high temperature
exhaust gas, etc. instead of electricity. About 12∼13% of the total electric
power consumption in a building can be saved if an absorption type is adopted.
Therefore if the absorption chillers are adopted on a nationwide scale, it
is an effective and efficient solution to solve problems associated with an
electric power shortage. Since any heat energy that has high temperature but
has been wasted, and than if it can be used as a driving heat source of the
absorption chiller, it is more useful energy saving application of the absorption
chiller. The absorption chiller utilizes distilled water as a refrigerant
not freon. Hence it is very friendly to the global environment.
2. ADVANTAGE OF ABSORPTION CHILLER
1) Electric power consumption is only 1/20∼1/10 of
a vapor compression type chiller.
The comparison for the electric power consumption is as follows
in case a 170 usRT chilled installed. The electric power consumption is around
187 kWh when an electrically driven centrifugal chiller and a boiler are installed
as a HVAC system. Here the centrifugal chiller consumes about 130 kWh and
takes up nearly 70% of the electric power consumption of the entire air-conditioning
system. On the contrary, if a direct-fired double effect absorption chiller
installed, the power consumption of the entire air-conditioning system can
be reduce to 70 kWh. In this case the direct-fired double effect absorption
chiller consumes about 8 kWh, which is only 6.1% of the electric power consumption
of the centrifugal chiller.
2) Contributes to prevention of environmental pollution by
introducing non-freon refrigerant.
Centrifugal chillers mainly used for the cooling load of
more than 100 usRT and they have used R123 as a refrigerant whose ODP(Ozen
Deplection Potential) is 0.022 and GWP(Global Warming Potential) is 0.02.
From several years ago, it is in the process of replacing R123 with R134a
whose ODP is 0 and GWP is 0.29. But, because the GWP of R134a is very higher
than R123's, R134a is not a complete alternative refrigerant. On the contrary,
the absorption chiller utilizes distilled water as a refrigerant, and lithium
bromide solution as a absorbent. The absorbent is also stable and unharmful
to the human body. Hence the absorption type is very favorable to the environment.
3) The system is safe since it is operated under vacuum state.
Water serving as a refrigerant evaporates at 5℃, condenses
at 40℃,
and regenerates at 90℃
during operation of the fully vacuumed absorption chiller. This is meaning
that the system maintains vacuum condition in operation. So, there is no chance
for the system to experience physical damage of explosion.
4) Saving installation area
In case of heating and cooling are required, the direct fired
absorption chiller heater system reduces required installation area by 40%
when compared with a system composed of an electric centrifugal chiller and
a boiler. Consequently, the absorption chiller heater system increases availability
of the building.
5) Operating characteristics under a partial load are excellent.
The chillers are operated under a partial load rating between
50 and 70% for the most period of operation. And then, the absorption chiller
has higher efficiency at partial load operation more than full load operation.
It is also higher compare with the electrically driven centrifugal chiller.
Thus absorption chiller system can save running cost to a great extent.
3. TREND OF ABSORPTION TYPE IN KOREA
The typical outdoor temperature in Korea is in the range
of 28 ∼
38℃
in summer and 5 ∼
-20℃
in winter. Therefore energy consumption patterns are very much different from
season to season like as shown in Fig. 1. The electric power consumption and the fuel oil consumption
cross each other to the opposite direction in a period of 1 year. This requires
facility which corresponds to the maximum consumption of both energy types.
However the operating time under a peak load is relatively short. Accordingly
the Korean government makes every effort to reduce these maximum points.
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Fig. 1.
DEMAND PATTERNS OF LNG AND ELECTRICITY
1) The policy and circumstances of electric power in Korea.
The maximum electric power demand reached 41,007 MW in August,
2000. And then, the electric power consumption for air conditioning systems
takes around 20% of the total power consumption under the peak load in Korea.
And the amount of the power used for the air-conditioning is 8,073 MW which
amounts to the power generated by the 8th nuclear power plants.(Total construction
expense is approximately $9.2 billion.) The Korean government is in the process
of considering and carrying various policies. Typical examples are as follows.
(1) Enhancing propagation of the absorption chiller and ice
storge system.
(2) Enhancing propagation of high efficiency appliances.
(3) Enlarging the role of co-generation facility and emergency
electric generators.
(4) Power late policy for demand management.
Among the above countermeasures, propagation of the absorption
chiller is enlarged through the policies
as belows.
2) Policy and subsidy for augmenting propagation of absorption
of chiller.
(1) Financing for the purchase of the facility.
(2) Applying discounted gas rates.
(3) Reduction and exemption from taxes.
(4) Discounting the installation cost for city gas piping.
(5) Mandatory installation of the gas-fired absorption chiller
for new buildings.
(6) Restrictive policy for the types of fuel.
(7) Korea Electric Power Institute has started providing
a loan, and renting the absorption chiller system.
4. NEW APPLICATIONS OF ABSORPTION CYCLE IN KOREA
As advanced comments, the korean government adopted various
policies to reduce the electric peak
load in summer season. One is the installation of the district co-generation
system which produces electric power by generator and produces hot water by
wasted heat. The hot water is used for absorption chiller to make chilled
water for cooling. Another is the development for commercial product of small
capacity absorption chiller-heater for housekeeping. It is able to substitute
the electric packaged air-conditioner which is occupied most portion of electric
peak load.
1) Development of absorption chiller driven by low grade
hot water for district cooling and heating. In the present, The hot water
condition inlet 95℃
and outlet 80℃,
is supplied to drive an absorption chiller for district cooling. But if the
hot water is supplied at inlet 95 and outlet 55℃ in same pipe network, the
cooling capacity is increased to 2.4 times with same hot water flow rate.
For this purpose, The consortium comprised Century, Carrier, KDHC(Korea district
heating corp.). and POSCO(Phohang steel corp.) and developed the pilot unit,
40 usRT, from 1998 to 1999 which is installed in the office building of KDHC
and is operating for two years. The primary character of this system is that
the absorption chiller has auxiliary absorber and auxiliary generator to be
driven by low grade hot water to 50℃. And, the auxiliary solution heat exchanger and low
temperature solution heat exchanger is added to enhance COP. Even though the
achieved COP is 0.6 which is less than that of commercial product 95/80℃, 0.7 and
The size is 1.3 times and the cooling tower is needed large capacity, hot
water can be supplied to many unit and the cost of pipe network can be decreased.
The following figure 2 and 3 shows the cycle and duhring diagram.
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Fig.
3. Cycle diagram of single effect-double lift absorption
2) Commercializing of household small absorbtion air-conditioner
To reduce the peak load of electricity, it is commercialized
by century that is household small absorbtion air-conditioner, in stead of
electrically driven package air conditioner.
Which, applied double effect absorbtion cycle, is introduced
technological know-how from KO-GAS. The first commercialize product should
be produced in 2002 of which capacity is 3 usRT(The sort of capacity should
be extended to 1.5, 5, 7.5 usRT etc.).
This unit is adopted water cooled type for miniaturization
and effectiveness, of which C.O.P for cooling & heating is 0.8. And also
that is developed to multi type as three of indoor unit can be connected to
one outdoor unit. The cooling cycle of the unit and duhring diagram are shown
in Fig. 4 and 5.
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Fig. 4. Cooling
cycle of small absorption air conditioner
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Fig. 5. Duhring diagram of small absorption air conditioner.