Renewable Energy in Small Island Grids Design and Case study - Tuvalu
Overview 1. About ITP 2. Types of grid 3. Solar and storage integration 4. Case Study Tuvalu northern islands 5. Long term operation
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
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
Types of island grid 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 +) 5 of xx slides
Mini-grids 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 6 of xx slides
Why renewable energy? 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 7 of xx slides
Integrating renewable energy 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). 8 of xx slides
PV fuel save 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%. 9 of xx slides
PV fuel save plus 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. 10 of xx slides
PV primary 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. 11 of xx slides
Economics of renewable energy in mini-grids 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% 12 of xx slides
13 of xx slides Case study 1: Tuvalu Energy Sector Development Program (TESDP)
14 of xx slides TESDP Tuvalu
15 of xx slides TESDP Tuvalu
TESDP Overview 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 16 of xx slides
TESDP Generation on Funafuti 800 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 700 600 500 400 300 Sat Sun Weekdays 200 100 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 17 of xx slides
18 of xx slides TESDP Current PV generation
TESDP Increasing penetration Project will add up to another 900 kwp of capacity Goal will be to turn generators off during the day gridforming inverter required ~1 MW inverter capacity, 1-2 MWh electricity storage Expect >40% RE contribution 19 of xx slides
TESDP Challenges 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. 20 of xx slides
21 of xx slides Case study 2: Tuvalu Renewable Energy Program (TERP)
Case study Tuvalu northern islands 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 22 of xx slides
Case study Tuvalu northern islands 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 23 of xx slides
24 of xx slides Nanumea power station
25 of xx slides Generators
Tuvalu northern islands- key issues 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 26 of xx slides
27 of xx slides Transportation
28 of xx slides Transportation
29 of xx slides Vulnerability to weather
Aims of outer islands solar project 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 30 of xx slides
Load (kw) Load curve Nanumea island 35.0 30.0 25.0 20.0 15.0 10.0 5.0 After load growth Assumed loads From data logger 0.0 00:00 03:00 06:00 09:00 12:00 15:00 18:00 21:00 00:00 31 of xx slides
Load estimate - Nanumea 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. 32 of xx slides
System sizing overview 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. 33 of xx slides
34 of xx slides Design schematic
Design features 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 35 of xx slides
36 of xx slides Completed system
37 of xx slides Display
38 of xx slides Modular inverter/chargers
39 of xx slides Sealed batteries
40 of xx slides Passive cooling
Performance so far 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) 41 of xx slides
Training and operation 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 42 of xx slides
43 of xx slides Community
Lessons/challenges 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 44 of xx slides
Questions IT Power Renewable Energy Consulting Southern Cross House, 6/9 McKay St, Turner, ACT PO Box 6127 O Connor, ACT 2602 info@itpau.com.au p +61 (0) 2 6257 3511 f +61 (0) 2 6257 3611 itpau.com.au