Offgrid Power

System Design and Energy

Storage

Mini Grids:

Stephen Phillips

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www.optimal-power-solutions.com

Presentation Overview

1. Company and Markets: A Balanced Approach

2. Mini Grids Issues: Why Systems become unstable

3. System Control: Integrating the Old and New

4. Energy Storage: Getting the Data

5. High Power Systems: Are they really Safe?

6. Project Implementation: Making it Happen

7. Summary

2 www.optimal-power-solutions.com

The Company and Markets

A Balanced Approach

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Global Operations

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Australia

• Headquarters

• Innovation and R&D

• Marketing and

Corporate Activities

India

• Kolkata HQ

• Administration

• Bangalore Office

• Product Manufacturing

• Project focus on MW scale

Malaysia

• Kuala Lumpur HQ

• Project Activities

• Implementation Team

• Major Utility Clients


Global Operations

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USA • Caribbean Mini Grids

• US Military

Philippines

• Utility Clients

• Large Mini Grids

Indonesia

• PLN Client

• Large Mini Grids


Sun Belt Electrification Ratios

The Investment Decision

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With a) high diesel costs and b) good solar resources – Mini

Grids can be a good investment:

With diesel @ $0.90

per litre, a solar-

diesel hybrid would

have a 5% IRR

With diesel @ $1.10

per litre, a solar-

diesel hybrid would

have a 15% IRR

Mini Grid System Costs (LCOE)

• “On-grid renewable energy is becoming viable…. – Medium-scale (100 kW – 500 kW) PV = 15 to 19 USD cents/kWh

• “Diesel Gen costs are increasing in sun belt markets: – In Indonesia and Malaysia the DG costs are over $1.2 / kWh for small

sites

• “What is the cost of Storage ?”: – Lead Acid is around USD 35 cents per kWh (LCOE) and needs to be

much lower, around 15 cents.


Why do Systems become Unstable ?

Intermittency with High Solar Penetration


Solar Radiation Profiles: Cloud Events

PV Ramp Rates under Cloud Effects



“System Firming” Use of Suitable Storage to reduce Intermittency

Integrating the Old and the New

Solar PV Diesel Hybrid System

System Control Module

Battery Bank

Solar Array

Genset

Site Load

Renewable

Charge

Control

Module

DC BUSBidirectional

Inverter/Charger

Module

CO1

CO2CB11

CB12

Hydro Generator

Power System Control Scheme

PV Energy

Source

DC Interface

Filter

Power

Electronic

Devices

High Speed DSP

AC Interface

Filter

Mini Grid

Interface

Imbedded

Controls

Input/Output

Controls

External

Controls

SCADA

u-secs

m-secs

secs, min, hrs

Energy Storage

Mini Grid Control Innovations

Our control system developments have focused on mini-grid power quality management issues.

High penetration systems impact on the existing conventional plant and ramp rates dictate that means that Fast Control is needed, typically Voltage swells, sags and transients require correction in 100 milliseconds (IEC standard).

“Smart Grid” concepts around “two way” communication is needed, advanced metering, load control, DM initiatives.

Appropriate energy storage and power inverter capacity is increasingly needed for power transient and energy requirements.

Typical OPS Mini Grid System

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Significant Debate over DC versus AC Coupling

Pure DC coupling utilizes all the solar PV power on the

storage side

AC coupling connects the solar PV across the AC grid

usually with multiple inverters

Studies show for a typical load profile;

that the AC coupled system is best for day time loads but

adds to the LCOE

the DC coupled system improves efficiency for evening

loads with a reduction in solar PV capacity.

Comments on AC versus DC Coupling

Medium Penetration: Good Solar Day

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PV Energy

To

Battery PV

Battery

Energy

Diesel

Stop

Diesel

Start

Diesel Load following Diesel Load

Following

Poor Solar Day

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PV Energy

To

Battery

Diesel

Stop Diesel

Start

Diesel Load

following

Diesel Load

Following

Bunaken Island: Annual Operational Profile

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0

10000

20000

30000

40000

50000

60000

70000

80000

kW

h

Bunaken Solar vs. Genset Contribution

Solar

Genset

Site Load

Firming Cycles over 15 minute period

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-40

-20

0

20

40

60

80

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

PV Fluctuation on System Voltage, one minute Data

Battery Voltage

Battery current

Firming Power / Micro cycles

GETTING THE DATA TOGETHER

Lead Acid ZD+16h Test

Li ion ZD+16h Test

Severe impact on LA battery capacity

when High Power is needed

LA Battery life vs. Temperature

Arrhenius Effect

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East Penn LA Temperature Tests

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Li ion Battery Cycling Life

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One Solution: Na Ion Battery

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One Solution:

Na Ion Battery

48 Volt,

2 kWh Stack

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> 1 year of ~6 hour rate cycling

• Chemistry stable over broad voltage

range

• Symmetric charge/discharge profile

• >5000 Cycles shown, (80% DoD)

• Near perfect coulombic efficiency

5000 Rapid Cycles on Indicative Test Cell

Na Ion Technology: Cycle Life

Mini Grid Battery LCOE



Lead Acid Battery Issues

While Lead Acid (LA) is the “status quo” technology it has a

number of undesirable characteristics;

• Arrhenius Effect means the lifetime is reduced by higher

temperatures. The reaction rate doubles every 10 C.

• Depth of Discharge is limited so CAPEX is higher than

usually understood.

• Low Energy to Weight & Volume but good Power to Weight

• Good discharge rate but low charge rates (under high sun)

• Limited Cycle Life (Cyclic energy is fixed).

• Toxic materials means disposal can be a problem.

Are these systems safe ?

Advanced Lead Acid: Power Stack

Power Cell Performance

• 12 V DC

• Power: 25kW, instantaneous

• Energy: 1.0 kWh @ 3 h Rate;

1.5 kWh @ 20 h Rate

• 2,500 Amps for 30 Seconds

• 120 mm * 150 mm *380 mm

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Xp: High Power Advanced Lead Acid

Safety and Fire Issues: Storage

Hawaii 15 MWh Lead Acid

Safety and Fire Issues: Substations

Utility Substation Fires

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Na-

Ion

Capital Cost per Cycle Comparison

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Efficiency and Life Comparison

Na-Ion

Mini Grid Storage and Control


Storage can be used to achieve useful system benefits

1.Viability depends on diesel costs and storage LCOE considerations

2.A range of key factors include discharge duration, PSOC,DOD, Energy

Efficiency, life cycles, Ambient temperature, safe disposal.

3. With suitable control a number of systems benefits can be achieved

4. Communications and reliable data management is crucial.

Project Implementation and Delivery:

Making it Happen

OPS Project Background

Current Status:

Completed nearly 600 systems in India since 2009

About 60 projects in Malaysia and Indonesia

Size from 25 kW to 5 MW

Various sites in USA, Australia, and S E Asia

Working on new technologies in power conversion and control optimisation

Project Examples

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Project Examples: Indonesia

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Project Examples: Malaysia

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Indonesia – Morotai Island

• Island Power Supply

• State Utility Client

System:

– 3 x 250kVA OPS GEC Inverter

– 2 x 300 kVA OPS PIM Inverter

– 600 kWp of PV (pictured)

– OPS Customized Control

– OPS Remote Communications

– 360V DC, 2.7 MWh battery

bank

– 1.75 MW total gensets

– Maximum AC Output: 3 MW

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USA – Santa Cruz Island

• Essential services

• Navy barracks

• Radar facility

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Solar Hybrid: Caribbean Island

• Private Island

• Essential Power, Yacht Charging

System:

– 2 x 300kVA OPS Hybrid Inverters

– OPS AC Switching Cabinet, rated

at 1.5MW

– 360V battery bank, 4.15MWh

rated at 14400 Ah

– 3 x 100 kW Wind Turbines

– 3 x 312kVA Diesel Generators

– 410 kWp Solar PV

– OPS Dual Channel MPPT Solar

Charge Controllers

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Indonesia – Bunaken Island

System 1.2 MW:

– 400kVA Hybrid Inverter

– 150kVA OPS Inverter

– 550 kWp of PV (pictured)

– 360V DC, 900 kWh battery bank

– 2 x 300 kVA gensets

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Sandakan Sabah: 1 MW Hybrid

Sandakan Sabah: 1 MW Hybrid

Market Potential 3.1 GigaWatt

Recent Systems Include:

Thank you for your attention today

and happy to discuss any points.

Least Cost, Fit

for Purpose and

Sustainable ??

Documents

Offgrid Power