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Offgrid Power
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System Design and Energy
Storage
Mini Grids:
Stephen Phillips
1
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
3 www.optimal-power-solutions.com
Global Operations
4
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
www.optimal-power-solutions.com
Global Operations
5
USA • Caribbean Mini Grids
• US Military
Philippines
• Utility Clients
• Large Mini Grids
Indonesia
• PLN Client
• Large Mini Grids
www.optimal-power-solutions.com
Sun Belt Electrification Ratios
The Investment Decision
www.optimal-power-solutions.com 7
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.
www.optimal-power-solutions.com 8
Why do Systems become Unstable ?
Intermittency with High Solar Penetration
www.optimal-power-solutions.com
Solar Radiation Profiles: Cloud Events
PV Ramp Rates under Cloud Effects
www.optimal-power-solutions.com
www.optimal-power-solutions.com
“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
18
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
20
PV Energy
To
Battery PV
Battery
Energy
Diesel
Stop
Diesel
Start
Diesel Load following Diesel Load
Following
Poor Solar Day
21
PV Energy
To
Battery
Diesel
Stop Diesel
Start
Diesel Load
following
Diesel Load
Following
Bunaken Island: Annual Operational Profile
22
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
23
-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
28
East Penn LA Temperature Tests
29
Li ion Battery Cycling Life
31
One Solution: Na Ion Battery
32
One Solution:
Na Ion Battery
48 Volt,
2 kWh Stack
33
> 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
www.optimal-power-solutions.com 34
www.optimal-power-solutions.com
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
38
Xp: High Power Advanced Lead Acid
Safety and Fire Issues: Storage
Hawaii 15 MWh Lead Acid
Safety and Fire Issues: Substations
Utility Substation Fires
41
Na-
Ion
Capital Cost per Cycle Comparison
42
Efficiency and Life Comparison
Na-Ion
Mini Grid Storage and Control
www.optimal-power-solutions.com
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
46
Project Examples: Indonesia
47
Project Examples: Malaysia
48
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
49
USA – Santa Cruz Island
• Essential services
• Navy barracks
• Radar facility
50
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
51
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
52
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 ??