solar-dc and electric vehicles

Solar-DC and Electric VehiclesAn Opportunity for India

Ashok Jhunjhunwala, IITM

[email protected]

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 opportunity for 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

• 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 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 opportunity for India

And it gets Worse

• As one realises that home-load is moving towards DC

• 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%

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 possibly 150W 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 Remote Control for Fan &

Tube light• ON/OFF and for dimming

Cell phone Charger/Socket• DC charger with USB port

LED Tube light• 15W - dimmable to 4W, instead of 36W

fluorescent tube

Cost: ₹20000 for 125W SP +1 kWh Battery


Products in pipeline

8

DC-powered 19” 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-gridhomes with support fromMinistry of Power(Government of India), RuralElectrification Corporation(REC), and Jodhpur VidyutVitran Nigam Ltd (JDVVNL)

• Deployment started withBhoom Ji ka Gaon, December2015: tough terrain, no roadconnectivity, sandstorms, lackof local resources

Solar-DC and Electric Vehicles: An opportunity for India 9

A home at Bap, Rajasthan

• Monitoring performance through Blue-tooth– Paramount in design tuning


Users Response

• “Apne Vidyarthiyon ko ghar kakaam dene laga hu. Khush huki is baar garmiyon mein bhibachhe mann laga kar padhaikarenge.”

- Masterji

• “Sab ko utshah se apne gharka Solar system dikhata hu ji,hamare ghar mein bhi pankha,light aur remote hai”

- Dunga Ram• feedback:

https://youtu.be/NF6EgdRsBXk


Motivation for going Solar Inverterless

• It is a Solar + power back-up, but far moreefficient

– as 100 Watts DC

• Can support 3 lights + 2 fans + cell-phone charging

• Or 3 lights + 1 fan + TV (24” LED/LCD) + cell-phonecharging

– Solar Panel and Batteries have to be appropriatelysized

• Devices can be added as required


Small Home AC Home DC HomeEnergy/ 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 125off-grid + Battery + Solar 5.60 71.44 6.7 1375 1.28 15.85 1.78 375AC +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 + DCappliances can be huge savings

• Further, 500W solar power with DC appliances can takecare of most essential loads in middle class homes– Except washing machines, mixers / grinders, air-conditioners– Small power drawn from grid: reduces power-bill– 240M homes: 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? Instead of Push create a Market PULL

• UDC Innovation aimed to create such 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 feeders with 11kV Distribution Line

Distribution transformer steps down voltage to 230V in each of the three phases

UDPM at home allows using present AC line and a limited power DC line

DT Normal: 230V

TRA

NSF

OR

MER

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

TRA

NSF

OR

MER

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-outControl

UDPM

No change in DT or distribution lines


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 VEHICLESWhen Indian cities are talking about overcoming air-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

costIC-engine Drive-train

Electrical Drive-train

Recent

Battery should be treated as 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

costPetrol 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 significant off-peak hour shortage of electricity

• Electricity generation continuously increasing• Need to discourage EV charging during 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 significant off-

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 – Charge in 45 minutes– Need High Voltage DC

Chargers


What is Ready in India

• Use of Li-Ion Advanced battery– 3000 charge-discharge cycles

• 2-wheelers / 3-wheelers (several players)

• Make in India Push– 2 / 4-door e-Rewa: small car

– e-Verito: 110 kms per charge• About 10 kms range for 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

• Development of Motors: BLDC, SR-motors– Drive for motors– Can enhance 10 to 15% efficiency

• Batteries– Battery Cell: Chemistry– Cell to Pack Design: Physics, Mechanics, Electronics

• Innovative Cell-packaging: Plate Thickness, interconnections, thermal management

• BMS and Charging / discharging– Partial charge – discharge, precise SOC and SOH monitoring

• Second Use of Battery

• Light-weight Materials, 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


solar-dc and electric vehicles

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