(16/02/2023)
Objective: We ( VA team) had doughs regarding the efficiency of solar water heaters (typically vacuum tube) installed on campus. Hence it was taken as one of the assignment to revisit the efficiency calculations . We discussed in this meeting regarding the modalities of calculating the efficiency of solar water heater.
for finding out the efficiency of that water heater we know the following term are as follow we discussed in meeting
- Area of tube which get exposed to direct sun light
- Temperature difference water i.e. Delta T
- Total incident energy on vacuum tube during the time of experiment
The major problem is solar irradiation data is non available with precision and as shadows , cloud cover is noise., which are not accounted when data is assumed form open source literature
The best way to start was to visit old VA t Blog and understand the step-in measuring efficiency.
त्यांनी आम्हाला मागील ब्लॉग वाचण्यास आणि कार्यक्षमता मोजण्याची पायरी समजून घेण्यास सांगीतले
(17/02/2023)
Prasad sir gave mi assignment related to efficiency topic. I starched to google company manufacturing in solar water heater. also started looking for reviews to understand which solar water heater is good? Which solar water heater is more efficient.
Could find 10 + leading names which includes Supreme Solar , Racold Solar Domestic, We could not find any efficiency data or claims in open advertising literature. On the other hand i could gather lot of information on different types of solar water heaters which includes flat plate, parabolic as well as evacuated tubes. My own understanding form literature is a Vacuum tubes heater are better and more efficient and cost effective. But no claims or understanding regarding the efficiency or overall efficiency with respect to incident solar radiation could be achieved. Details regarding study are available on link below
difference between Evacuated Tube Collectors and Flat-Plate Collector
https://1drv.ms/w/s!AhypCsFYbnwdgl2KoNFkzw0f2TdW?e=hwv8eg
18/02/2023
We don’t have an equipment to measure the radiation of sunlight in the Ashram, so I studied the pyranometer.
आपल्याला solar water heater ची efficiency काढण्यासाठी solar irradiation काढावा लागतो.
18/02/2023
दीक्षित सर डिस्कशन मध्ये असे म्हणाले की
कोणी पूर्ण वर्षभराचा irradiation डेटा सेव करून ठेवला नाही आणि हे हुडकून काढायला सांगितले जेणेकरून आपल्याला उपयोग करता आले पाहिजे.
https://1drv.ms/w/s!AhypCsFYbnwdgmABU84Run8d9qRp?e=gmdNOu
(20/02/2023)
Prasad sir they gave me assignments to find out irradiation data in Maharashtra
(22/02/2023)
One of the google link we could get following data which talks about average incident energy of solar radiation in MJ per day, This data is an average over a month and hence has to be taken with lot of care as big variation can lead due to change in atmosphere on any particular day. We decided to go ahead as no immediate option was available to us.
or
https://footprinthero.com/solar-irradiance-calculator
with the help of this link, we assume Solar Irradiance at Pabal as instrument was not available
Taken 2 water heater reading of solar water heater.
For finding out efficiency, we need to calculate area of solar plate on which the light is falling, and the second parameter would be capacity of water tank.
1.Evacuated Glass Solar Tubes area measurement on which light fall.
Length of tube=174.............(all dimension in cm)
= Diameter of tube 5.5
One tube area = 174 *5.5 = 957 per tube Total 32 tubes on the solar water haeter under study
hence total are for enegy capture = 32*957 cm² =30624cm² which accounts to
Total area = 3.06 m².... (Total 32 tube)2.water tank capacity (not accurate because we take dimension from outer side, but we know inside tank insulated is their)
length =2740mm
diameter=580mm
in this 723.93 liter, this includes thickness of wall and insulating material. From Vigyan Ashram old data ( memories of employee)
we considered water tank is 500 liters (there is we use insulation)
1> DIC boys hostels solar water heater reading.
The next task was to get output data i.e. heat capture. This was mCp (T2- T1) . T2 is final temperature at at 17 hrs. and T1 i.e. initial temperature at 9.00 Hrs
1>at 9 am water temperature 47 degree Celsius
2>at 5pm water temperature 51 degree Celsius
Efficiency of solar water heater take reading.
1) Take readings of solar water heater
time 8 hr. (9 am to 5 pm)
=3600*8= 28800 sec
pune = 4.85 KWh /m²/day………. (In February)
convert it into CHU/h ft² (Celsius heat unit per hour per square foot)
1) DIC boys’ hostel (1)
1>in morning at 9 am water temp=47.5 °C
And in evening 5pm water temp=51 °C
Input=Area of ETC ×Energy in 1m²×Time
=3.06*20.58*106 Joule…..(Evacuated tube area[m square], in one m square how match light come [MJ m square/day])
= 62974800 joule
Output = mcpΔT or Capacity of strong thank *water heat constant * temperature difference
= 5,00,000* 4.187*(51-47) (mass of water in gm, water temperature in degree Celsius, temp diff(t2-t1) in second)
= 8374000 joule
efficiency of solar water heater (output/input) *100
=13.29%
1> Meditation Hall solar water heater reading.
1>at 9 am water temperature 27 degree Celsius
2>at 5pm water temperature 45 degree Celsius
Efficiency of solar water heater take reading.
1) Take readings of solar water heater
time 8 hr. (9 am to 5 pm)
=3600*8= 28800 sec
pune = 4.85 KWh /m²/day………. (In February)
convert it into CHU/h ft²
1) Meditation Hall solar water heater reading.
1>in morning at 9 am water temp=27 °C
2>And in evening 5pm water temp=47 °C
Input=Area of ETC ×Energy in 1m²×Time
=3.06*20.58*106…..(Evacuated tube area [m square] , in one m square how match light come [MJ m square /day])
= 62974800 joule
Output = mcpΔT or Capacity of strong thank *water heat constant * temperature difference
= 5,00,000* 4.187*(47-26) (mass of water in gm, specific heat of water Jull/gram, temp diff(t2-t1) in second)
= 4,39,63,500 joule
efficiency of solar water heater (output/input) *100
=69.81%
A dramatic difference between the efficiency of two different water heater were noted. This could be due to very high initial temperature of DIC hostel water heater compare to mediation hall water heater. Need to re do the measurement exercise to verify said hypothesis.
