Autoclaving is one of the techniques used in moist heat sterilisation. All R&D organisations and other hospitals requiring their tools to be sterilized need autoclaves. Inlet water to the Autoclaves is normal raw water which is having a temperature between 20˚C - 26˚C depending upon the season. The operational temperature for the Autoclave is 121˚C. There is huge gap between the inlet temperature to the Autoclaves and required for operation. By using the different technics, the experiments are carryout on the Solar flat plate collectors with different models (with inserts, without inserts & by using Nano-fluids) to enhance the output temperature at 90˚C. Considerable energy is saved in this system by using solar heated water than the conventional Electrical water heaters. The savings are not only the Electrical Energy savings but also the savings on the SITC (Supply, Installation, Testing and Commissioning) of Electrical Installations (Electrical Distribution System). The principle behind the working of an Autoclave is that-The higher the pressure created inside the autoclave, the higher would be the attainable temperature inside it.
The boiling point of water at normal atmospheric pressure is 100˚C. when the free-flowing steam at a temperature of 100˚C is subjected under pressure of 1 atmosphere above the sea-level pressure i.e., 15 lbs pressure per sq. inch, the temperature inside the autoclave happens to rise up to 121˚C, which is an usual and common parameters employed in the moist heat sterilisation.
Steam enters the chamber jacket, passes through an operating valve and enters the rear of the chamber behind a baffle plate. It flows forward and down through the chamber and the load, exiting at the front bottom. A pressure regulator maintains jacket and chamber pressure at a minimum of 15 psi, the pressure required for steam to reach 121˚C. Overpressure protection is provided by a safety valve. The average American home would take 45 years to consume that much energy. This extreme example serves as a reminder of how resource-intensive high- volume, high-throughput medical-grade autoclaves can be.
Moist heat destroys microorganisms by the irreversible denaturation of enzymes and structural proteins. The temperature at which denaturation occurs varies inversely with the amount of water present. Sterilization in saturated steam thus requires precise control of time, temperature, and pressure.
Pressure serves as a means to obtain the high temperatures necessary to quickly kill microorganisms. Specific temperatures must be obtained to ensure the microbicidal activity. Minimum sterilization time should be measured from the moment when all the materials to be sterilized have reached the required temperature throughout.
Most of the manufactures recommends the sterilization process in an autoclave are 15 min. at 121˚C and pressure at 2 atm.
Sterilization may be carried out some time even below at 121˚C shown in
Steam held at elevated temperature and pressure for time is used to transfer moist heat. Steam has much greater heat transfer than boiling water, −80 calories to boil water, 540 calories to produce steam. Heat acts to denature proteins, effectively killing all cells present.
The steam of the autoclave shown above has been provided from a solar flat plate collector which was stored in a thermal storage system. The required temperature for the Autoclave system is 121˚C. Normally the solar water heating system is designed for 60˚C. But by using the different technics (with inserts and with Nano-fluids) the temperature of the solar flat plat collector is enhanced from 60˚C - 90˚C.
Hospitals, R&D labs and other regional health centres can greatly benefit from using solar Autoclaves. Rural Primary Health Clinics where Electricity is not available to generate steam could benefit from solar Autoclaves.
Impact on Solar thermal Autoclaves on Electrical Distribution Load in Institutional Building @60˚C and its cost analysis at 500 kVA level is shown in
| S No. | Temperature in ˚C | Approx. corresponding pressure (atm) | Mini. sterilization time (minutes) |
|---|---|---|---|
| 1 | 126 - 129 | 2.50 | 10 |
| 2 | 129 - 134 | 2.75 | 7.5 |
| 3 | 134 - 138 | 3.0 | 5 |
| Description | No of heaters | kW | Units/day | No. of units/ month | Unit rate (Rs) | Expenditure/ month (Rs) | Expenditure/ annum (Rs) |
|---|---|---|---|---|---|---|---|
| Autoclaves on electric heaters | 04 × 2 systems (8 Nos) | 18 kW × 04 × 02 = 144 kW | 432 (72 kW for 30 Min × 6 loads × 2 systems | 8640 (20 day month) | 7.00 | 60,480 | 725,760 |
| Autoclaves on electric heaters | 04 × 1 system (4 Nos) | 18 kW × 04 × 01 = 72 kW | 216 (72 kW for 30 Min × 6 loads × 01 systems | 4320 (20 day month) | 7.00 | 30,240 | 362,880 |
| Autoclaves on SWHS | Nil | Nil | 08 flat plate collectors | Nil | Nil | Nil | Nil |
Capacity of the Autoclave is 72 kW. Each Electrical Element is 18 kW.
Number of Electrical elements is 04 Nos.
So, total capacity of the Autoclave is 18 kW × 04 Nos = 72 kW.
Electrical Power Consumption/day:
18 kW × 04 Nos × 30 min (0.5 Hrs) = 36 kWh.
Daily number of loads is 06 times, Number of Autoclaves is 02 Nos.
So, the total Electrical Energy consumption/day = 36 kW × 06 Nors × 02 systems = 432 kWh.
Number of units per month:
Normally R&D labs will work only 05 day week, so, the number days per month = 20 days.
Number of units consumed per month = 432 kWh × 20 days = 8640 units.
As per Cat-II tariff, per unit charge is Rs 7 per unit.
So, the Electrical Power consumption per year is 8640 units × Rs 7 = Rs 60,480.
Electrical Power Consumption per year:
Rs 60,480 × 12 Months = Rs 725,760.
Designed capacity of the Electrical Distribution system is 500 kVA:
Without using the solar water heating system, the required temperature of the Autoclaves is around 121˚C. To increase the temperature at 121˚C, 144 kW (18 kW × 8 Nos) of Electrical Heaters are used. The capacity of the Electrical Load is 144 kW at 0.98 P.F (say 150 kVA).
The Electrical Distribution system, one of the feeder (250 Amps, TPN MCCB-Power Load) is connected to the domestic water heating load, the total Electrical load of 40 rooms of each 2.5 kW capacity Electrical heaters are connected.
There for the total capacity of the domestic heating Electrical load = 2.5 kW × 40 rooms = 100 kW = 102 kVA (100 kW at 0.98 P.F). The load reduction is 150 kVA + 102 kVA = 252 kVA, the other Distribution loads are 248 kVA.
Based on the above Electrical loads the recommended size of Transformer is 500 kVA and its cost analysis is shown in
Techniques can be applied to the industries, power systems and also households to make them stable and due to that the system becomes stable and efficiency of the system as well as the apparatus increases. The use of microcontroller reduces the costs. Automatic Power factor correction (APFC) device reads the power factor from line voltage and line current, calculating the compensation requirement switch on different banks. Improving the power factor of an installation requires a bank of capacitors which acts as a source of reactive energy. This arrangement is said to provide reactive energy compensation.
An inductive load having a low power factor requires the generators and transmission/distribution systems to pass reactive current with associated power losses and exaggerated voltage drops. If a bank of shunt capacitors is added to the load, its (capacitive) reactive current will take the same path through the power system as that of the load reactive current. Since, as pointed out, this capacitive current Ic is in direct phase opposition to the load
| S No. | Description | Qty | UoM | Rate (Rs) | Total system cost (Rs) |
|---|---|---|---|---|---|
| 1 | HT cable: supply of 11 kV 3C × 120 Sq. mm HT XLPE armoured Cable. | 50 | Mtr | 1100 | 55,000 |
| 2 | LT cables: supply of 3.5c × 400 Sq. mm XLPE insulated, 1.1 kV grade armoured aluminium cable. | 100 | Mtr | 1800 | 180,000 |
| 3 | HT metering panel (11kV) | 1 | Nos | 332,000 | 332,000 |
| 4 | 500 KVA O/D TRANSFORMER (OIL FILLED) | 1 | each | 720,000 | 720,000 |
| 5 | APFC PANEL (Thyristor Switched) | 1 | No | 459,400 | 459,400 |
| 6 | LT KIOSK 800A TPN 4P 50KA EOD type ACB | 1 | No | 288,000 | 288,000 |
| 7 | Main LT Panel: I/C: 800A 4 pole EDO type ACB (50 KA)-1 No. O/G (400 A TPN MCCB-2 Nos, 250 A-2 Nos, 125 A-2 Nos, 100 A-3 Nos) | 1 | No | 644,000 | 644,000 |
| 8 | AMF Panel suitable for 750 kVA | 1 | Set | 1,027,500 | 107,500 |
reactive current (IL). The two components flowing through the same path will cancel each other, such that if the capacitor bank is sufficiently large and Ic = IL, there will be no reactive current flow in the system upstream of the capacitors. This is indicated in
In
kVAR required for transformer compensation:
Calculation of required capacitor:
Fixed compensation of the 500 kVA Transformer is (500 kVA × 6%) = 30 kVAR.
Suppose actual P.F is 0.8, required P.F is 0.98 and total connected load is 354 KVA.
kW = 354 × 0.8 = 283.20. Required capacitance = 283.20 × Multiplying Factor = 283.20 × 0.547 (from
Total capacity of the APFC panel = Fixed compensation + Variable compensation i.e., 155 kVAR + 30 kVAR = 185 kVAR (available rating).
The capacity of the APFC panel in
Impact on Solar Thermal Autoclaves on Electrical Distribution Load in Institutional Building @60˚C and its cost analysis at 315 kVA level.
Designed capacity of the electrical distribution system is 315 kVA:
With using the solar water heating system, the hot water output is at 60˚C, but required temperature is around 121˚C. To increase the temperature from 60˚C - 121˚C, 18 kW × 4 Nos of Electrical Heater are used. The capacity of the Electrical Load is 75 kVA (72 kW at P.F 0.95).
| 0.9 | 0.91 | 0.92 | 0.93 | 0.94 | 0.95 | 0.96 | 0.97 | 0.98 | 0.99 | 1 | |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 0.6 | 0.849 | 0.878 | 0.907 | 0.938 | 0.970 | 1.005 | 1.042 | 1.083 | 1.130 | 1.191 | 1.333 |
| 0.7 | 0.536 | 0.565 | 0.594 | 0.625 | 0.657 | 0.692 | 0.729 | 0.770 | 0.817 | 0.878 | 1.020 |
| 0.8 | 0.266 | 0.294 | 0.324 | 0.355 | 0.387 | 0.421 | 0.458 | 0.499 | 0.547 | 0.608 | 0.750 |
| 0.85 | 0.135 | 0.164 | 0.194 | 0.225 | 0.257 | 0.291 | 0.328 | 0.369 | 0.417 | 0.477 | 0.620 |
| 0.9 | 0.029 | 0.058 | 0.089 | 0.121 | 0.156 | 0.193 | 0.234 | 0.281 | 0.342 | 0.484 | |
| 0.91 | 0.030 | 0.060 | 0.093 | 0.127 | 0.164 | 0.205 | 0.253 | 0.313 | 0.456 | ||
| 0.92 | 0.031 | 0.063 | 0.097 | 0.134 | 0.175 | 0.223 | 0.284 | 0.426 | |||
| 0.93 | 0.032 | 0.067 | 0.104 | 0.145 | 0.192 | 0.253 | 0.395 | ||||
| 0.94 | 0.034 | 0.071 | 0.112 | 0.160 | 0.220 | 0.363 | |||||
| 0.95 | 0.037 | 0.078 | 0.126 | 0.186 | 0.329 |
The Electrical Distribution system, one of the feeder (250 Amps, TPN MCCB-Power Load feeder) is connected to the domestic water heating load, the total Electrical load of 40 rooms of each 2.5 kW capacity Electrical heaters are connected,
There for the total capacity of the domestic heating Electrical load is 102 kVA (100kW at 0.98 P.F).
The load reduction is 177 kVA (say 180 kVA).
Required size of Transformer after load reduction i.e., 500 kVA - 180 kVA = 320 kVA
Recommended size of Transformer is 315 kVA and its cost analysis is shown in
Fixed compensation of the 315 kVA Transformer is (315 kVA × 5%) =15.75 kVAR.
Suppose actual P.F is 0.8, required P.F is 0.98 and total load is 282 KVA.
kW = 282 × 0.8 = 225.60, Required capacitance = 123.40 kVAR.
Total capacity of the APFC panel is 139 kVAR (i.e., fixed compensation + variable compensation). The capacity of the APFC panel in
Designed capacity of the Electrical Distribution system is 500 kVA. With using the solar water heating system with inserts (twisted inserts with Nano fluids), the hot water output is at 90˚C, but required temperature is around 121˚C.
| Description | Electrical load (Auto claves) kVA | Electrical load (DWHS) kVA | Load reduction kVA | Recommended TFR sizes in kVA | @60˚C | @90˚C |
|---|---|---|---|---|---|---|
| Conventional Electrical System. | 150 | 105 | Nil | 500 | Nil | Nil |
| Load reduction by STWH’s- with inserts @90˚C | 75 | 105 | 180 | 315 | Up to 60˚C for DWHS | With twisted inserts |
| Load reduction by STWH’s with Nano fluids and twisted tape inserts@90˚C | 19 | 105 | 236 | 250 | Up to 60˚C for DWHS | With inserts and Nano fluids |
| S No. | Description | Qty | UoM | Rate (Rs) | Amount (Rs) for 315 kVA |
|---|---|---|---|---|---|
| 1 | HT Cable: Supply of 3 Core 11 KV 120 Sqmm HT XLPE (E) armoured Cable. | 50 | Mtr | 1100 | 55,000 |
| 2 | LT cables: Supply of 400 Sqmm 3.5 Core XLPE insulated, 1100V grade armoured aluminium cable. | 100 | Mtr | 1800 | 180,000 |
| 3 | HT Metering Panel (11kV) | 1 | No | 332,000 | 332,000 |
| 4 | 315 kVA O/D Transformer (Oil Filled) | 1 | each | 600,000 | 600,000 |
| 5 | APFC PANEL(Thyristor Switched) 100 kVAR | 1 | No | 368,000 | 368,000 |
| 6 | LT KIOSK 630A TPN 4P 50KA EOD type ACB | 1 | Set | 260,000 | 260,000 |
| 7 | Main LT Panel: I/C: (800A 4 pole EDO type ACB-50 KA-1 No) and Outgoings (400 A TPN MCCB (35 KA)-2 Nos, 250 A-2 Nos, 200 A-2 Nos, 100 A-2 Nos. | 1 | Set | 540,500 | 540,500 |
| 8 | AMF Panel suitable for 500 kVA | 1 | Set | 860,000 | 860,000 |
| Total | 3,195,500 | ||||
To increase the temperature from 90˚C - 121˚C, 18 kW × 1 No of Electrical Heater are used. The capacity of the Electrical Load is 19 kVA (18 kW at P.F 0.95).
The load reduction is 126 kW (133 kVA, P.F as 0.95).
The Electrical Distribution system, one of the feeder (250 Amps, TPN MCCB-Power Load feeder) is connected to the domestic water heating load, the total Electrical load of 40 rooms of each 2.5 kW capacity Electrical heaters are connected,
There for the total capacity of the domestic heating Electrical load = 102 kVA (100 kW at 0.98 P.F). Load reduction is 235 kVA.
The required size of Transformer after load reduction i.e., 500 kVA − 235 kVA= 265 kVA. So, recommended size of Transformer is 250 kVA, the cost analysis of the system is represents in
Calculation of required capacitor:
Fixed compensation of the 500 kVA Transformer is (250 kVA × 5%) = 12.5 kVAR.
Actual P.F is 0.8, required P.F is 0.98 and total load is 210 KVA.
kW = 210 × 0.8 = 168,
Required capacitor = kW × Multiplying Factor = 168 × Multiplying Factor= 168 × 0.547 (from table to find Value according to P.F 0.8 to P.F of 0.98) = 92 kVAR.
Total capacity of the APFC panel is 105 kVAR (i.e., fixed compensation + variable compensation).
The capacity of the APFC panel in
In the first stage of the study, the hot water temperature is enhanced to 90˚C by using inserts into the solar flat plate collector fins. The enhanced water is fed to the Autoclaves for generation of the steam at 121˚C. Information such as current (Amps), voltage (Voltage) and power (kW) was collected directly from the nameplate affixed on the Autoclave.
| Description | No of Geysers | kW | Units/day/ geyser | No. of units | Unit rate (Rs) | Cost/day (Rs) | Cost/month (Rs) | Cost/annum (Rs) |
|---|---|---|---|---|---|---|---|---|
| Electric Geyser (2.5 kW) | 40 | 100 | 11 | 440 | 7.00 | 3080 | 92,400 | 1,108,800 |
| SWHS | Nil | Nil | 08 FPC | Nil | Nil | Nil | Nil | Nil |
| S No. | Description | Qty | UoM | Rate (Rs) | Amount (Rs) at 250 kVA level |
|---|---|---|---|---|---|
| 1 | HT Cable: Supply of 11 kV, 3c × 120 Sqmm HT XLPE armoured Cable. | 50 | Mtr | 1100 | 55,000 |
| 2 | LT cables: Supply of 400 Sqmm 3.5 Core XLPE insulated, 1100V grade armoured aluminium cable. | 100 | Mtr | 1800 | 180,000 |
| 3 | HT Metering Panel 11 kV | 1 | No | 332000 | 332,000 |
| 4 | 250 kVA O/D Transformer (Oil Filled) | 1 | each | 520000 | 520,000 |
| 5 | APFC Panel (Thyristor Switched) | No | 1 | 294400 | 294,400 |
| 6 | LT KIOSK 800A TPN 4P 50KA EOD type ACB | 1 | Set | 260000 | 260,000 |
| 7 | Main LT Panel: I/C (800A 4 pole EDO type ACB-50 kA-1 No, Outgoing (400 A TPN MCCB-35 kA-1 Nos, 250 A-3 Nos, 100 A-3 Nos. | 1 | Set | 455,000 | 455,000 |
| 8 | AMF Panel suitable for 320 kVA | 1 | Set | 660,000 | 660,000 |
| Total | 2,756,400 | ||||
After measuring the power consumption of the Autoclaves without solar hot water, the capacity of the Transformer was estimated. Then by using the solar hot water at 90˚C was estimated. The cost savings of the system was calculated with Autoclave Electrical Heaters and without Electrical heaters for 60˚C and 90˚C. For the equipment which was tested, the weekly power consumption (kWh/week) can be obtained using the same equation. But instead of using the nameplate power rating, the actual measured power rating was used. According to the calculations, the cost of the Transformer changes from rating to rating. In this context, it is important to note that this rate of cost of higher capacity Transformer and its associated feeders is less than smaller capacities and also considerable Electrical Energy savings are noted with and without Solar Hot water systems.