Sunday, 23 March 2014

Reno Rhythm - DIY 2.2kWp

Reno Rhythm – DIY 2.2kWp

Switching Domains

My mind was constantly switching between loneliness and fulfilment; I had walked into the National Art Gallery, looking at painting and browsing through pictures that expressed abandonment.  Pictures that expressed this feeling of total sense of bliss in loneliness.  There was an exhibit by Amrita Sher-gil called “The Passionate Quest”.  Amrita Sher-Gil had had a short life (1913-1941).  It was the human touch that one saw in all her paintings, the emoting and empathising with the human feeling made me stand up and stare.

Sometime back, I had driven with Deanna through the Sierras about an hour from Reno.  I was still an intern and this was 2007 when I had realised that art ran through my blood, I had in that year quit my job and bought a trailer home to go with my Dodge V8, Deanna had been happy for me and had agreed to travel with me, she was building a Summer House in the Sierras and we had travelled from the city to the outskirts of the Sierra and parked right next to the construction.  It was a large house facing the mountains which were towards the South.  It had a 2.2kW Solar Photo Voltaic system that was being installed on the roof and Deanna’s face beamed every time I spoke of how beautiful the place was. “I wouldn’t have got here without you,” she spoke in a soft adoring voice.

We went back a long way and this drive was more in lieu of me quitting my job, I would head back to my country this summer, and wanted to spend time with my friend.
“It’s cold here,” I mentioned.
“Yes, country boy,” she had jest fully replied pointing to the setting sun by the yonder mountains.  “It normally is cold in the winter,” she smiled and we moved into the living room that was ready to move into, while the rest of the house was still being constructed.  There was a satellite link for internet and we both got our laptops out, the rucksacks were in place for the night and the fireplace had a bright glow to it as a fire was beginning to roar.  I had cut the firewood from the nearby forest, “It’s allowed?” I had asked and she had replied, “Go right ahead.”

Firewood crackling and a dinner to cook, she and I had slipped quietly into the browsing mood, I had started to play some music on the laptop, while she continued on the internet, I walked to the semi furbished kitchen and had decided to fry some baked beans with pita bread.  While I corked open the baked bean cans, there was already coffee brewing, I had made sure that I had made enough to last us the night.
“You look busy,” she said, looking over, I was snappy and fast at cooking and she could see me running around with the utensils and cans, organising, cutting and beginning to wash the used dishes simultaneously.
“The salad to go with the baked beans and lots of coffee,” I beamed as I walked back into the high ceiling living room.  This house was going to see more of me.

          “Stories to Be Told and Not Much Talking To Do These Days”

The 2.2kWp Solar PV

The house was ready in the summer of 2008 and along with other components that went into making a green certified house; it had Solar PV system installed on the roof.  The Solar Panels came with Trojan Batteries and Inverters and the specifications are as given below:

Solar Design for roof mounted Solar PV system for Remote Regions with no or little grid power.

Total Watts = 675 Watts
Total WHrs/day = 5400WHrs/day
8 nos. 12v/150 Ah individual battery
12 nos. 12v/185Wp PV modules

Battery Sizing

Step I
Find the inverter efficiency which in this case is 0.9
5400 /0.9Inv Eff = 6000 Whr/day
Step II
Calculate the ampere-hour/day, remember  watts = Volts x Amps
6000 Whr/day / 24 DC system Volts =250 avg    AH/day
Step III
Use the above figure to find the System AH which will generate the battery specs
250 x 1.11 battery temp multiplier x 1 days    autonomy /0.5 DOD
= 555 total system AH
Step IV
555 total AH / 150 Ah individual battery    capacity = 4 parallel battery strings
24 V system voltage / 12v battery voltage = 2 batteries in series
4 parallel strings x 2 batteries in series = 8 batteries

Array Sizing

Step I
Get that formula:
5400 Whr daily load / 4.6 peak sun hours /0.8 battery eff /0.88 temp losses / 0.9 shading coefficient / 0.85 system derate
= 2200W peak array

Step II
Find the no. of modules needed :
2200/185 W STC@12V = 12 modules needed
24 V Nominal array Voltage / 12 V nominal module voltage = 2 modules/string, 6 strings total

 “It’s all in the Rhythm, That’s When I Find Out The Design Of Things”