Deployment Experience in
Off-Grid and Near Off-Grid Homes
Prabhjot Kaur, Sudeep Jain*, Ashok Jhunjhunwala
IIT, Madras, India
* CMD, TEDA, Govt of India

Outline
• Power Requirements for Indian Homes
• Existing Technology Solutions: Issues and Problems
• Proposed Solar-DC Solution
• Deployments
• Comparisons with other existing solar Systems

225M Indian Homes: Power Connectivity Status
• 32.8% households are Off-Grid - 80 Million homes
• Another 30-40 million homes are near off-grid
• Black-outs for more than 12 hours a day
• Power shortage as high as 56% in one of the
Indian states.
- 2011 National Census

How much do the connected homes Consume?
– Total domestic consumption: 200TWh per year for 1.25 billion people
• An average of about 500Wh/day per person or 2.5 kW per home /day
• Average power consumption for grid connected homes is only 4 kWh per day (33% homes do not have power)
– requires less than 600 W solar panel at a home to generate this
– Most lower-income homes will consume no more than 1000Wh a day
• 250W solar panel will generate this

Grid
Decentralised Solar Power at Homes
AC-DC
Solar
DC
DC-AC
Battery
DC-AC
Load
AC
• Solar PV gives DC Power
– But load is AC
– Needs a DC-AC convertor
• Now as we add a battery
– Battery stores only DC
• Require a AC-DC convertor for charging
• Require a DC-AC convertor during discharging
• For low power , each convertor can have 10 to 15% loss
– Solar-AC may have 30 to 45% loss plus battery loss
5

And it Gets Worse
• As one realises that home-load is moving towards DC
AC fan at speed 1
CFL tube low intensity
72W
60W
36W na
BLDC fan
LED tube
30W
9W
15W
4W volume prices similar for fans
LED tube life much longer (DC powering enhances reliability)
• All Electronics devices work on low-voltage DC
– TV (LED/LCD), laptops. Cell-phones, speaker-phones, tablets, speakers
• AC to DC conversion has losses from 20% to 50% in each device
• Even the refrigerators, air-conditioners, washing machine in future will be BLDC motors
• Use of DC-powered and energy-efficient devices
– Consumption down by 50%

for off-grid and near-off-grid
Grid
(optional)
AC-DC
48VDC
Battery
Solar
48VDC
DC – appliances: fans, light and electronics
48VDC
• 48V DC micro-grid at home to connect solar, battery and Load
– Highly power-efficient usage of
Solar
– Battery added without converters
– Designed to have minimal end-toend losses
• When grid is available
– Low-power from grid added to DC micro-grid
7

125W-500W
IITM-CYGNI
1kWH – 5kWh
230V AC
Invertor less
Solar DC System
48V DC (125 – 500W)
Normal Load Line
Emergency Line
Bluetooth interface
48V DC chosen for Microgrids at Homes due to
• Safety considerations
• Lower cable losses compared to 12V/24V DC systems

And the Industry Lined Up
– For 48V DC appliances
• BLDC Fans- Crompton Greaves/Lucas-TVS
• LED Tube Lights and LED Bulbs – Inteligon
• Cell phone chargers and Laptop Chargers – Cygni
• OGH unit - Cygni
• VRLA Battery: 48V/1KWh, (1600 cycles at 50% DOD) – Amara Raja
• Solar PV Panels at MPPT of 48V - Cygni
– And the Deployment of DC-microgrid for Off Grid and Near Off-
Grid Homes started

Deployment
• Irakkam Island, Andhra Pradesh, in proximity to
India's one of the two satellite launch centers,
Sriharikota; but
– only some households get electricity once in a while,
– others are off-grid
• Kundithal, The Neelgiris, Tamil Nadu, India
– Tribal village, down hill, forest area
– Restricted movement after 5pm

Total 204 households in the Village.
Scheduled Tribes (ST) colony.
People of ST colony are small land holders and economically weaker than rest of the communities.
Irrukkam Island, AP, India
Number of Homes 28, 1 community
Centre, 1 school,
1 temple
Types of Homes Mixed: Thatched and concrete

Feedback
“ It is easier to cook with the light by our side. Earlier I couldn’t place my utensils properly because of the dark, but now there is enough light for me to navigate through my cooking.“*
One of The Nilgiris beneficiaries.
“ Our kids can now study in dark and we can carry our routine activities with much ease now.”*
– A beneficiary from Irrukkam
Island, AP, India.
* translated from Tamil in English

• This habitation is 59 Kms from Ooty
(nearest City)
• No EB supply
• Surrounded by Forest
Kundithal, The Nilgiris, India
Number of Homes 20
Types of Homes Thatched Roofs

Changing Lives
I am now watchful of the snakes and animals, even during dark
A lot more stories I can narrate in the light, with better expressions
Its no more scary !!

Comparisons – Specifications
Results
System
Solar PV Panel
Nominal Battery Voltage
Battery capacity
Battery Type
Load type
Max Load capacity
Emergency Mode
Enables Billing
System
Solar AC
System 1
100W
12V
75Ah
AC
45W
No
No
Solar DC
System 2 System 3/OGH
50W
12V
125W/250W/500W
48V
40Ah 26Ah- configurable
Lead Acid/VRLA
DC
50W
DC
500W
No
No
End- End Efficiency
Yes
Yes
System Efficiency
(without battery)
System 1 (solar-AC) 19.8%-31.4%
System 2 (solar-DC) 49.6% - 68.8%
OGH (solar-DC) 83.9%
47.2% - 60.9%
69% - 75.8%
91.4%

– While losses in OGH(solar-DC system) can be brought down to 7%
(without battery loss) as compared to 25-45% losses in other solar systems
• How does it impact costs?
– Solar Panel size comes down to nearly a factor of 2
– Battery size reduces by 20%
– OGH system with 1 ceiling fan, a tube light, a bulb, a charger, 1 solar panel, 1KWh Battery costs Rs20K (350 USD)
• System can be upgraded to accommodate more lights, fans, LCD TV

Ministry of Power announced immediate installation of IITM Solar
DC system in 4K Off Grid rural homes in Jodhpur and nearby districts, Rajasthan, India
A lot more to do
The journey just begun…
Thank You