solar-dc_

Solar-DC and Electric Vehicles
An Opportunity for India
Ashok Jhunjhunwala, IITM
ashok@tenet.res.in

In first week of December 2015
When whole of IITM had no power for 75 hours
• Even 1 MW solar plant at IITM failed to provide any power
– There was one home which continued to have lights
and fans and cell-phone / lap-top charger
• 125W solar panel + 1 kWh battery (50% can be used)
• Two tube-lights were used regularly + bulb and fan
occasionally + laptop charged / discharged fully 15 times +
cell phone charging
• Fails to add up
– Solar DC Inverterless
• Full DC wiring, all Loads DC, solar and battery connected on
DC line, input grid power converted to DC
2Solar-DC and Electric Vehicles: An opportunityfor India

Decentralised Solar Power at Homes
• Solar PV gives DC Power
– But load is AC
– Needs a DC-AC convertor
• Now if we add a battery
– Battery stores only DC
• Requirea AC-DC convertorfor
charging
• Requirea DC-AC convertor
duringdischarging
• For low power, each convertor
can have 10 to 15% loss
– Solar with battery may have up
to 45% loss + battery loss
3
AC Load
DC-AC
Battery
AC-DC DC-AC
Grid
Solar DC
Solar-DC and Electric Vehicles: An opportunityfor India

And it gets Worse
• As one realises that home-load is moving towardsDC
• 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 futurewill be
BLDC motors
• Use of DC-powered and energy-efficientdevices
– Consumption down by 50%
4
Fans AC fan BLDC fan
At full Speed 72W 30W
At speed 1 60W 9W
Lighting CFL Tube light LED tube
At Max. Intensity 36W 15W
At Lowest Intensity NA 4W
Volume prices
similar for fans
LED tube life much longer (DC
powering enhances reliability)

Move to Solar-DC at Home Premises
• Home Micro-grid connecting
– Solar Panel
– Battery
– DC Appliances
• Highly efficient usage of Power
– Low-power from grid alone converted from
AC-DC (Designed to have minimal losses)
• 48V DC chosen due to
– Safety considerations
– Lower cable losses compared to 12V/24V
DC systems
• But design non-trivial
– Solar MPPT voltage varies
– Battery needs independent charge voltage
– Load is at some fixed voltage
– DC-DC converters will add similar losses
AC-DC
battery
Loadgrid
Solar
48VDC
48VDC
48VDC

Solar-DC Inverterless
6
125W to 500W 48V DC
(and possibly150W
uninterrupted AC) Power
with BLE prepaid recharge
125W panels
• Upto 500W possible
230V AC
Special 1 kWh VRLA battery
with 1600 cycles for 50%
DoD
• Up to 5 kWh possible
Designed as an expandable
product, still keeping losses low
Monitored using
Bluetooth

Appliances
7
LED Bulb
• 5W instead of 30W bulb
BLDC Fan
• 30W instead of 72W AC fan
• 9W at lowest speed RemoteControlfor Fan &
Tube light
• ON/OFFand for dimming
Cell phoneCharger/Socket
• DC charger with USB port
LED Tube light
• 15W - dimmable to 4W, instead of 36W
fluorescenttube
Cost: ₹20000 for 125W SP +
1 kWh Battery

Products in pipeline
8
DC-powered19” Colour TV
• Consumes 30W along with
set-top box at 48V DC
DC Desert Cooler
• Consumes 60W
instead of 180W
AC cooler
DC 100L
Refrigerator
• In design
Solar Water-stove
• Still experimental
• Will require at least
500W solar power
• Pilot to be carried out

Deployment in Rajasthan
• Electrifying 4000 off-grid
homes with support from
Ministry of Power
(Government of India), Rural
Electrification Corporation
(REC), and Jodhpur Vidyut
Vitran Nigam Ltd (JDVVNL)
• Deployment started with
Bhoom Ji ka Gaon, December
2015: tough terrain, no road
connectivity, sandstorms, lack
of local resources
Solar-DC and Electric Vehicles: An opportunityfor India 9

A home at Bap, Rajasthan
• Monitoring performancethrough Blue-tooth
– Paramount in design tuning

Users Response
• “Apne Vidyarthiyon ko ghar ka
kaam dene laga hu. Khush hu
ki is baar garmiyon mein bhi
bachhe mann laga kar padhai
karenge.”
- Masterji
• “Sab ko utshah se apne ghar
ka Solar system dikhata hu ji,
hamare ghar mein bhi pankha,
light aur remotehai”
- Dunga Ram
• feedback:
https://youtu.be/NF6EgdRsBXk

Motivation for going Solar Inverterless
• It is a Solar + power back-up, but far more
efficient
– as 100 Watts DC
• Can support 3 lights + 2 fans + cell-phone charging
• Or 3 lights + 1 fan + TV (24” LED/LCD) + cell-phone
charging
– Solar Panel and Batteries have to be appropriately
sized
• Devices can be added as required

Small Home AC Home DC Home
Energy/
day
kWh
Cost
per
day ₹
Battery
Size
kWh
solar
panel
Wp
Energy
/ day
kWh
Cost
per
day ₹
Battery
Size
kWh
solar
panel
Wp
AC Grid + 0 LS 3.16 15.79 1.21 6.04
AC Grid + Battery + 4h LS 3.63 31.35 2.11 1.28 10.22 0.61 125
off-grid + Battery + Solar 5.60 71.44 6.7 1375 1.28 15.85 1.78 375
AC +Battery + Solar + 4h LS 3.67 30.53 1.9 125 1.24 8.66 0.45 125
Small AC / DC Home Power Costs
Device Numbers
deployed
Operation
hrs/ day
Tubelights 2 6
Fans 2 12
Bulbs 2 10
Air coolers - -
Phones 1 4
Laptops - -
TV 1 10
Cost / day includes depreciation and
interest for solar panel and battery
assuming grid costs of ₹5 per unit
Off-grid home costs with solar-DC (₹15.85 per day) becomes comparable to
costs of on-grid AC homes with no power-cuts (₹15.79 per day). If one uses AC
wiring with DC appliances, costs for off-grid home shoots up to ₹24.24 per day.

Even for grid-connected home
• Solar-DC Inverterless + DC power line at home + DC
appliances can be huge savings
• Further, 500W solar power with DC appliances can take
care of most essential loads in middle class homes
– Except washing machines, mixers / grinders, air-conditioners
– Small power drawn from grid: reduces power-bill
– 240Mhomes: average 500W solar (50 sqft), will produce nearly
• 240M x 0.5 kw x 1600 solar hours a year = 190,000 GWh per year
• Close to total Domestic consumption in a year
• India can become the most green nation

UDC Innovation
15
• Issues
– Acceptance among people for technology and DC
– Lack of standardization and availability of Home appliances
• What it Needs? Insteadof Push  createa Market
PULL
• UDC Innovationaimed to createsuch a market PULL by
– Providing a limited Power DC line at each home from
existing AC distribution grid in addition to existing AC line
– During Load shedding, AC line is cut-off, but DC line is kept
ON
• Making the DC line free of Load-shedding

Addition of a DC Power line at each Home
16
 Substation charges feederswith 11kV Distribution Line
 Distribution transformer steps down voltage to 230V in each of the three
phases
 UDPM at home allows using presentAC line and a limited powerDC line
DT Normal:230V
TRANSFORMER
33KV 11 KV
•
Substation
Home
Unlimited Pow er existing
230Vac line
New Limited Power DC
line at 48V
UDPM
M

Load shedding: 90% power cut – Brown-out
17
 Brown-out: continue feeding 10% power to Distribution Line
 Substation feeds 11kV in normal and with 4.4kV in brown-out condition (only 10%) on DL
 Distribution transformer steps down voltage to 230V in normal / 90V in brown-out condition
 UDPM detects voltage drop to 90V: cuts off AC line but continues feeding 48V DC
 10% BO Power small enough to be made available even during worst power-shortage
DT Normal:230V
Brown-out:90V
TRANSFORMER
33KV 11 KV
•
Tap or Step-down
transformer(0.4)
•Brown-out
4.4 KV
Some 10%
of pow er
Substation
Home
230Vac line: cut-off
during Brow n-out
Limited Pow er DC
supply at 48V:
Uninterrupted
Brown-out
Control
UDPM
No change in DT or distributionlines

A free of Load Shedding line at homes
• Will now induce customers to use DC power
line and appliances
– As DC appliances become acceptable and
customers see power-savings and reliability
• Will add more and more appliances
– When Limited power provided by UDC gets
exhausted, will be willing to add solar-DC

ELECTRIC VEHICLES
When Indian cities are talking about overcomingair-pollution

Rational for going Electric
• India does not have much oil
– Our oil imports are rising continuously and hurting
Indian economy very badly
– No solution in sight in short, medium or long-term
• Our cities and towns are highly congested
– As middle class increases, vehicle population
continuously grow
– Highly polluting urban India

How ready are we with EV?
• For any vehicle, compare the
cost of mechanical (IC Engine)
drive-train (MDT) with electrical
drive-train without batteries
(EDT)
– Along with associated
subsystems
• MDT cost goes up year after
year (inflation)
• EDT cost goes down year after
year (R&D, Moore’s law and SW)
– Sometime in recent times it
crosses each other
– Gap is to only increase year
after year
21
Year
cost
IC-engine
Drive-train
Electrical
Drive-train
Recent
Battery should be treatedas fuel

Cost of Fuel
• Petrol cost per Km increases year
after year (at least till last year)
– Though enhanced fuel-efficiency
through R&D helps slow this
• Total cost of battery per Km (life-
time depreciation, interest,
maintenance and charging of
battery) keeps coming down
– Battery R&D enhancing charge-
discharge cycles and reducing costs
continuously
– Likely to only accelerate
• Crossover took place sometime
back
22
Year
cost
Petrol cost
per Km
Battery plus
charging cost
per Km
Li-Ion Battery costs are falling 8% per annum

The nay-sayers
• But do we not have shortage of electricity?
– No significantoff-peak hour shortage of electricity
• Electricity generation continuously increasing
• Need to discourage EV chargingduring peak hours
– India has huge solar potential to charge EV in day time
• Do electric-generation plants not pollute?
– Power generator pollutes much less than a vehicle for every Km even today
– Much easier to manage reduced pollution in large electric plants as compared
to in every vehicle
• Technology can be further improved to reduce emissions
– Power pollution is not in most congested areas
• Disposal of battery
– Technologies fast evolving for battery-reuse and end of life safe disposal

Benefits Power Industry
• Introduce Time of day
Metering for Vehicles
– Can enable significantoff-
take of power during night
time and off-peak hours
– Helps in Load Balancing and
reduce peaking
• Tariff for day time charging at
commercial rates
• Use Solar Chargers during
day time or pay high day
time costs
• Slow-chargers at home
– AC chargers: typically
from 15A single phase
– Takes 7 hours for full
battery life
• Fast Chargers at Public
Places
– Chargein 45 minutes
– Need High VoltageDC
Chargers

What is Ready in India
• Use of Li-Ion Advanced
battery
– 3000 charge-dischargecycles
• 2-wheelers / 3-wheelers
(several players)
• Make in India Push
– 2 / 4-door e-Rewa: small car
– e-Verito: 110 kms per charge
• About10 kms rangefor 1 kW
– e-Maximo: 8-seater shared-
taxi / goods vehicle
• Need push for
– Small buses
– Large Buses (may have to be
hybrid to begin with)

R&D Required
• Developmentof Motors: BLDC, SR-motors
– Drive for motors
– Can enhance 10 to 15% efficiency
• Batteries
– Battery Cell: Chemistry
– Cell to Pack Design: Physics, Mechanics, Electronics
• InnovativeCell-packaging: Plate Thickness, interconnections,
thermal management
• BMS and Charging/ discharging
– Partial charge – discharge, precise SOC and SOH monitoring
• Second Use of Battery
• Light-weightMaterials, Integration

Why did all this become possible today?
• Cost Point: But why did the cost point become
comparable to AC now?
• Clues
– Power Electronics Integrated Circuits
– Digitisation of signal processing in power
– Coupling / transformers break the bound of 50 Hz
• Can now operate at 5000 Hz as easily
• Potential to impact all kinds of Industries
tomorrow?

What Can we Achieve
• 50% of Power produced using Solar by 2030
– Decentralised solar and DC micro-grids to play important
role
• Most Transport using Electric Power by 2030
• Climate Change debate will be turned up-side down
– Huge opportunity for Make in India

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