The document explores the design and implementation of renewable energy systems in small island grids, focusing on Tuvalu. It presents various grid types, motivations for integrating solar power, and specific renewable energy projects aimed to improve energy reliability and reduce diesel dependency in underserved areas. Case studies highlight ongoing programs intended to increase renewable energy penetration and address logistical and reliability challenges associated with energy supply in remote island communities.

1. Renewable Energy in Small Island Grids
Design and Case study - Tuvalu

2. Overview
1. About ITP
2. Types of grid
3. Solar and storage integration
4. Case Study – Tuvalu northern islands
5. Long term operation

3. About ITP
•Specialist renewable energy consulting firm
•Over 30 years international experience and 1,500 projects
•Founded in the UK in 1981
•Major regional offices in UK, India, China and Australia

4. About ITP - Australia
• Head office in Canberra, offices in South Australia, NSW
and Auckland
• Active in Australia and the Pacific region for over 10
years
• Involved in RE projects of all scales (1 kW to 50+ MW)
• Services
• Engineering Consultancy
• Project Engineering
• Energy Markets and Advisory
• International Aid and Development

5. Types of island grid
5 of xx slides
• Generally speaking, a micro-grid is self-contained and
limited by geography
• Loads can vary from being very small (e.g. a few houses)
to very large (e.g. a remote town with a large energy
user)
• Smallest form is individual home energy systems (1
house)
• Mini-grids (100 – 1,000 kWh/day) – eg remote islands
• Small grids (1,000 – 30,000 kWh/day) – eg larger rural
town centre or “main” island
• Medium grids (30,000 kWh/day – 100,000 kWh/day)
• Large grids (100,000 kWh/day +)

6. Mini-grids
6 of xx slides
• Small, remote islands in the Pacific (pop. 200 – 2000)
• Typically one or two villages
• Mostly residential/rural energy use
• Small power station operated by trained staff
• In the past, typically diesel generators

7. Why renewable energy?
7 of xx slides
• Reduce reliance on
imported diesel
• Reduce running costs
• Cleaner
• Quieter
• Improve reliability
• But:
• Upfront cost can be high
• Only works during day
• Storage required
• Can have integration
problems with generator

8. Integrating renewable energy
8 of xx slides
Three broad diesel/PV hybrid design options:
• PV fuel-save (no battery storage, providing
~10% annual load contribution),
• PV fuel-save plus (sometimes utilising a small
amount of battery storage, providing up to 30%
annual load contribution), or
• PV primary (utilising a large amount battery
storage, providing >50% annual load
contribution).

9. PV fuel save
9 of xx slides
•Sized to supply about 30% of the average midday load.
•Diesel generators run continuously. PV reduces their loading during
the day.
•No batteries or specialist integration equipment.
•Lowest initial capital cost.
•Reduce annual fuel bills by around 10%.

10. PV fuel save plus
10 of xx slides
• Intelligent control system that occasionally spills some PV output
to ensure that the generators are kept sufficiently loaded.
• Diesel generators still run continuously, but over the year, the PV
makes a much larger contribution (~30% total, 60% in the middle
of the day).
• Sometimes include a small battery bank to optimise loadings.

11. PV primary
11 of xx slides
• Large battery bank able to meet load with all generators off.
• Relatively high integration costs
• Highest annual contribution from renewable energy sources (can go to 100%)
• Economically viable for smaller loads or where diesel costs are unusually
high or supply is uncertain.

12. Economics of renewable energy in mini-grids
12 of xx slides
Grid size Diesel Efficiency Cost of generation Economic level of RE
Mini 1-2 kWh/L $0.70 - $2.00 / kWh 90% +
Small 2-3 kWh/L $0.50- $0.70 / kWh 30% - 70%
Medium 3-4 kWh/L $0.20- $0.50 / kWh 20% - 50%
Large 4+ kWh/L $0.20- $0.30 / kWh 10% – 30%

13. Case study 1: Tuvalu Energy Sector
Development Program (TESDP)
13 of xx slides

14. TESDP – Tuvalu
14 of xx slides

15. TESDP – Tuvalu
15 of xx slides

16. TESDP – Overview
16 of xx slides
• Four-year program funded by the World Bank, started in
2015
• Provides assistance in energy efficiency, prepayment
metering, and renewable energy
• Will push renewable energy penetration on main island of
Funafuti well beyond 100% to increase RE contribution

17. TESDP – Generation on Funafuti
17 of xx slides
• Population is around 7,000 people
• Midday load is 800 kW on weekdays, 500 kW on
Sundays
• 3 x 600 kW diesel generators
• 750 kWp PV capacity
• PV curtailment device installed on 410 kWp
0
100
200
300
400
500
600
700
800
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
Sat
Sun
Weekdays

18. TESDP – Current PV generation
18 of xx slides

19. TESDP – Increasing penetration
19 of xx slides
• Project will add up to another 900 kWp of capacity
• Goal will be to turn generators off during the day  grid-
forming inverter required
• ~1 MW inverter capacity, 1-2 MWh electricity storage
• Expect >40% RE contribution

20. TESDP – Challenges
20 of xx slides
• Very little space for large amounts of PV
• Requires good communication between PV field and
controller at power station
• Retraining of staff necessary. Dispatching done manually,
but an inverter-based system will need to be
automatically controlled.

21. Case study 2: Tuvalu Renewable
Energy Program (TERP)
21 of xx slides

22. Case study – Tuvalu northern islands
22 of xx slides
• Nine small atoll islands
• Total population approx. 10,000
• 6,000 on the capital, Funafuti
• Other islands populations 100-1,500
• Outer islands only accessible by boat, typically 24hrs by
boat to each island
• Irregular shipping (every 3-6 weeks)
• Shipping often disrupted by weather or boat unavailability

23. Case study – Tuvalu northern islands
23 of xx slides
• Existing low voltage AC
electricity grids (diesel)
since 2001
• Grids operated by
electricity utility (Tuvalu
Electricity Corporation)
• Local operators (TEC
employees) deal with day
to day running
• Technicians from the
capital visit periodically or
for repairs when required

24. Nanumea power station
24 of xx slides

25. Generators
25 of xx slides

26. Tuvalu northern islands- key issues
26 of xx slides
• Reliability
• Only 12-18 hours of power per day normally (down to 2-4 hrs
sometimes)
• Frequent diesel shortages due to shipping unreliability
• Generator breakdowns
• Long delays for repairs (can take weeks to send a technician from
Funafuti)
• Cost
• Estimated ~$1.20 to $1.50/kWh cost of supplying energy (possibly
more)
• Vulnerable to diesel price changes
• Vulnerable to utility cash flow issues
• Tariffs ~25c/kWh – outer islands subsidised by main island and by
government
• Remote diesel grids were built as a service to the community,
but are very expensive for the government

27. Transportation
27 of xx slides

28. Transportation
28 of xx slides

29. Vulnerability to weather
29 of xx slides

30. Aims of outer islands solar project
30 of xx slides
• Outer islands 100% renewable energy
• 24hr power
• System to last 20 years without need for major
modification
• Reduce operating costs of outer islands power systems
• Improve power reliability (and availability during
disasters)
• Grant-funded (NZ Govt)
• Eliminate need for aid fuel subsidies

31. Load curve – Nanumea island
31 of xx slides
0.0
5.0
10.0
15.0
20.0
25.0
30.0
35.0
00:00 03:00 06:00 09:00 12:00 15:00 18:00 21:00 00:00
Load(kW)
After load growth
Assumed loads
From data logger

32. Load estimate - Nanumea
32 of xx slides
• Average 550 kWh per day
• Little seasonal variation, but some “busy” times of year.
• Highest demand around Christmas and special events
• 40% of demand during “solar” hours
• 60% evening/night time
• Allowance for extra days with poor sun – 2 days
• Use this to size battery bank
• Then size solar PV array to meet day time load plus
enough extra energy to fully charge the batteries.

33. System sizing overview
33 of xx slides
• 33,000 Ah battery bank (sealed lead acid batteries)
• 200 kW solar PV array
• SMA modular inverter/charger units
• Diesel generator to be switched off normally.

34. Design schematic
34 of xx slides

35. Design features
35 of xx slides
• Modular
• if one unit fails, most of the system can be kept online
• Spares kept on island, easy to swap out
• Off-the-shelf inverter/controller, easy to order a new one
• Robust and corrosion resistant
• Cyclone proof structure
• No air conditioning required
• Because the air conditioner is often a failure point
• Low maintenance

36. Completed system
36 of xx slides

37. Display
37 of xx slides

38. Modular inverter/chargers
38 of xx slides

39. Sealed batteries
39 of xx slides

40. Passive cooling
40 of xx slides

41. Performance so far
41 of xx slides
• System is very large for current loads
• Batteries drop to 80% overnight, are fully charged before
midday if sunny
• Can go for 5 days of cloudy weather without generator
• 1 inverter failure – local operator successfully replaced it
and sent it back for warranty claim
• Effective cost of energy supply reduced to about
$0.55/kWh (from over $1)
• However this is still higher than the tariff ($0.25/kWh)

42. Training and operation
42 of xx slides
• Local operators involved from beginning of construction
• Training throughout construction and troubleshooting
• Other staff in Funafuti (capital) have been doing solar
training over a longer period
• Very challenging for the outer island operators to adapt to
the new technology

43. Community
43 of xx slides

44. Lessons/challenges
44 of xx slides
Less well-known challenges ITP has seen over the years:
• Systems becoming too reliable (operators stop maintaining
generators totally/ get lazy)
• Social problems with 24hr power (eg loud music at night)
• Logistics can be very complicated
• Getting accurate data and information is difficult (eg
powerhouse data, shipping schedules)
• Limited market for companies with experience in designing
and building renewable energy systems on island
environments

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6/9 McKay St, Turner, ACT
PO Box 6127 O’Connor, ACT 2602
info@itpau.com.au
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IT Power Renewable Energy Consulting
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