Products

 
  The STL consists of two parts
  Principle of operation

The STL consists of two parts

    The STL is composed of a tank(s) filled with nodules (balls) and heat transfer fluid. Approximately 60% of the volume of the tank is occupied by the nodules and the remaining 40% is fluid. The heat transfer fluid is usually mono-ethylene glycol. Other brines such as mono-propylene glycol or calcium chloride may also be used. The number of nodules in a system determines both the heat exchange rate between the nodules and the heat transfer fluid and also the total energy stored in the STL.

The nodules... The Cristopia Nodule
 
The spherical nodules (balls) are blow moulded from a proprietary blend of polyolefins and filled with PCM (Phase Change Material). A range of PCMs allow thermal energy to be stored at temperatures between -33°C and +27°C (see table). 
 
The nodules are manufactured in two diameter sizes : 77 mm and 98 mm for use respectively at very low phase change temperatures (-18 to –33°C), intermediate phase change temperatures (-3 to –15°C) and conventional building air conditioning ice storage temperature (0°C). A special heat storage nodule with phase change capability at +27°C for use as a heat recovery media is also available (AC.27 nodule).
 
The mechanical and chemical characteristics of the nodule shell are fully adapted to the nodule life conditions. The nodule lifetime is higher than “the equivalent of 20 years of normal utilization”. Indeed, the nodules withstand 10,000 cycles without any breakage. In addition, the polyolefine materials used are completely neutral towards phase change materials (eutectic salts) and heat transfer fluids. Once filled with a phase change material the nodule plug is sealed by an ultrasonic welding machine to ensure a perfect watertight seal.
 

Characteristics for 1 m³ STL

Nodule
type
Phase
change
temperature
Latent
heat
Sensible
heat
Heat transfer
factor
Nodule
weight
Toxicity
LD50 value
Operating
temperature
limits
 
 
Tst
°C
 
QI
kWh
Solid
Qss
kWh/°C
Liquid
Qsl
kWh/°C
cristallisation
Kvcr
kW/°C
fusion
Kvfu
kW/°C
 
 
Kg
 
 
mg/Kg*
 
 
°C
SN.33
SN.29
SN.26
SN.21
SN.18		 -33
-28.9
-26.2
-21.3
-18.3		 44.6
39.3
47.6
39.4
47.5		 0.7
0.8
0.85
0.7
0.9		 1.08
1.15
1.2
1.09
1.24		 1.6
1.6
1.6
1.6
1.6		 2.2
2.2
2.2
2.2
2.2 		724
681
704
653
706		 2600
1200
1200
1300
2700		 -40

To

+60
AN.15
AN.12
AN.10
AN.06
AN.03
AC. 00
AC.27		 -15.4
-11.7
-10.4
-5.5
-2.6
0
+27		 46.4
47.7
49.9
44.6
48.3
48.4
44.5		 0.7
0.75
0.7
0.75
0.8
0.7
0.86		 1.12
1.09
1.07
1.1
1.2
1.1
1.04		 1.15
1.15
1.15
1.15
1.15
1.15
1.15		 1.85
1.85
1.85
1.85
1.85
1.85
1.85		 602
620
617
625
592
560
867		 8400
5000
11000
18000
58000
85000
2500
-25

To

  +60

Data for 1 m³ of tank

Allow an useful expansion volume of 1% to 5% according to service pressure (i.e. 10 to 50 L for 1m3 of tank).
* : according to the O.E.C.D convention of May 12, 1981.
LD 50 : (median lethal dose), oral, is a statistically derived single dose of a substance that can be expected to cause death in 50% of animals when administered by the oral route. The LD 50 value is expressed in terms of weight of test substance per unit weight of test animal (mg/kg)

Characteristics of the nodule

Blend of polyolefins
Chemically neutral towards eutectics and heat transfer fluid
Thickness 10/10 : no migration of the heat transfer fluid
Sphere obtained by blowing : no leakage
Welding of the cap by a ultrasonic welding machine
Air pocket for PCM expansion  : very little stress on the shell

 Description of the Nodule

The Cristopia Nodule

    The nodule is the result of a long product development work. Several tests were used to determine the nodule characteristics (diameter, shell thickness, shell thickness regularity, shell materials, etc...) :

Tensile test
Accelerated life test
Measurement of failure pressure
Determination of viscoelastic behavior (creep test and relaxation test)
Chemical aging in commercial glycols and PCMs
Measurement of internal pressure during freezing
Polarized optical microscopy
Impact test

The result is an outstanding lifetime, higher than 10000 cycles (more than 27 years).

Cycles of the Nodule

...In a made to measure tank Cristopia Tank

A purpose manufactured tank is filled with nodules around which heat transfer fluid is circulating to ensure heat exchange.
These tanks may be cylindrical, with design service pressures up to 10 bars or rectangular for atmospheric systems. Cylindrical tanks can be designed horizontally, vertically, or for burial underground.

Tanks are fitted with upper manholes for installing the nodules, lower manholes for emptying the nodules and internal baffle pipework designed to generate maximum heat transfer efficiency.
Each tank is specifically designed to accommodate the energy storage requirement for a particular system.

  

 

Examples of tank characteristics

Volume


m³		 External
diameter

mm		 Total
lengh

mm		 External
surface area
for insulation
m²		 Connections
inlet / outlet

mm		 Number
of cradles		 Empty
weight

kg		 Heat transfer
fluid volume

m³
2
5
10
15
20
30
50
70
100		 950
1250
1600
1900
1900
2200
2500
3000
3000

2980
4280
5240
5610
7400
8285
10640
10425
14770

 10
18
29
37
47
61
89
106
147		 40
50
80
100
125
150
175
200
250		 2
2
2
2
3
3
4
4
6		 850
1250
1990
2900
3700
4700
6900
7300
12700		 0.77
1.94
3.88
5.82
7.77
11.64
19.40
27.16
38.80

Total length : Standard pressure drop 2.5mWG.

  The STL consists of two parts
  Principle of operation