Hybrid Micro Grids for rural electrification: Developing Appropriate Technology Antoine Graillot, TTA TRAMA TECNOAMBIENTAL, S.L. Avda. Meridiana 153 08026 Barcelona Tel: + 34 934 463 234 Fax: + 34 934 566 948 tta@tramatecnoambiental.es AIE Event Maputo, June 10 th 2009
Relevant aspects in rural electrification Cost-effectiveness The needs: demand analysis and segmentation The technologies and design practice Ownership and operational scheme User and operator training/capacity building Monitoring and performance assessment Lessons learned in demonstration projects
What is a Hybrid Mini Grid with RE? A combination of different but complementary energy generation systems based on renewable energies or mixed (RES- genset) Hybrid powered mini-grids can provide steady community-level electricity service, such as village electrification, offering also the possibility to be upgraded through grid connection in the future Total installed power up to 100 kw (according to IEC) Distribution line in Low Voltage (up to 1.000V) (only distribution) Single or 3-phases PV Hybrid Mini Grid in West Bank, Palestine
Classification of Hybrid Mini Grids DC coupling All electricity generating components are connected to a DC bus line from which the battery is charged. Photovoltaics Wind Energy Genset Hydro Power AC generating components need an AC/DC converter. = ~ = ~ = ~ AC/DC Converters The battery, controlled and protected from over charge and discharge by a charge controller, then supplies power to the DC loads in response to the demand. DC bus linebar Charge Controllers Optional DC Loads AC loads can be optionally supplied by an inverter. Battery Inverter AC Loads
Classification of Hybrid Mini Grids AC coupling All electricity generating components are connected to an AC bus line. Photovoltaics Wind Energy Genset Hydro Power AC generating components may be directly connected to the AC bus line or may need a AC/AC converter to enable stable coupling of the components. = ~ = ~ AC/DC Converters Inverters In both options, a bidirectional master inverter controls the energy supply for the AC loads and the battery charging. AC bus line 230 or 400 V Master Inverter and Battery charger Optional AC Loads DC loads can be optionally supplied by the battery. Battery DC Loads
Classification of Hybrid Mini Grids DC and AC coupling DC and AC electricity generating components are connected at both sides of a master inverter, which controls the energy supply of the AC loads. Photovoltaics Wind Energy Genset Hydro Power DC loads can be optionally supplied by the battery. = ~ AC/DC Converter On the AC bus line, AC generating components may be directly connected to the AC bus line or may need a AC/AC converter to enable stable coupling of the components. DC bus linebar Charge Controllers AC bus line 230 or 400 V Master Inverter and Battery charger AC Loads DC Loads
MILES DE EUROS PV cheaper than grid extension for remote areas 100 90 80 70 Red Media Tensión 60 50 40 30 FV autónoma 6325 Wh/día (3,2-4,0 HSP) 20 FV autónoma 3300 Wh/día (3,2-4,0 HSP) 10 Red Baja Tensión FV autónoma 2200 Wh/día (3,2-4,0 HSP) 0 0 0,5 1 1,5 2 2,5 3 3,5 Kilómetros Comparison of investment costs between grid extension and off-grid PV in Spain
/kwh /mes usuario medio PV more sustainable than fossil fuelled Gensets 1,00 0,90 Combustible G&O&M Inversión microrred 20,0 0,80 0,70 16,0 0,60 0,50 12,0 0,40 0,30 8,0 0,20 0,10 4,0 0,00 Grupo electrógeno directo Grupo electrógeno + baterías FV híbrida (25% fracción solar) FV híbrida (80% fracción solar) FV (100% fracción solar) 0,0 Levelized costs for PV and Diesel technologies in microgrid for 340 users in Peru (D.R. 5%, Diesel: 0,57 /l) Source: http://www.esmap.org/filez/pubs/620200785630_peru_solar-diesel_amazon_111-07.pdf
/kwh /mes usuario medio PV more sustainable than fossil fuelled Gensets 1,00 Combustible G&O&M Inversión (microplanta + microrred) 0,90 20 0,80 0,70 16 0,60 0,50 12 0,40 0,30 8 0,20 0,10 4 0,00 0 Grupo electrógeno directo Grupo electrógeno + baterías FV híbrida (25% fracción solar) FV híbrida (80% fracción solar) FV (100% fracción solar) Levelized costs for PV and Diesel technologies in microgrid for 340 users in Peru (D.R. 5%, Diesel: 1 /l) Source: http://www.esmap.org/filez/pubs/620200785630_peru_solar-diesel_amazon_111-07.pdf
VISION: Universal electrification-individual plants and micro grids under one operational scheme MSG MSG Individual Micro-Power Plants
From individual PV autonomous power plants to microgrids Application types Types of uses Home applications Lighting Audio/video Refrigerator(s) Small household appliances Washing machine Irons Freezer(s) Odd jobs Individual PV micro plants in Europe Public areas applications (places of collective life: worship halls, community centre, health centre, etc.) Economic activities applications The same appliances as above are used, but more and more powerful. Multi-user Public lighting. microgrids in Developping Village water pumping. Countries Process equipment supply (mainly motors)
Comparison of PV Individual and Micro grids Individual Electrification Micro plants Advantages Consumption is user managed on a day to day basis. System black outs affect just one user. Systems can be easily moved to a new location. Disadvantages Limited surge power capacity. Monitoring individual systems can be expensive and difficult. Maintenance and repair service complex to organize in rural areas. Multiuser Solar Grids (MSG) Improved quality (surge power, load shedding, etc). Lower investment for compact villages. Energy saving can be practiced using improved management tools. Lower maintenance costs. Telemetry can be economic for monitoring system status. If the power plant fails, everybody is cut off. Social rules required to distribute energy availability. Local management required. Systems generally need to be serviced on site. Challenge: sharing the energy available without conflicts Energy distribution and metering problem!
Energy Availability General scheme for tariff: users pay for consumed kwh In stand-alone electrification with RE, Key aspect is the available energy and not the installed power Tariffs must reflect this idea Tariff based on the Energy Availability (similar to fee for service prepayment) Clearer and easier financial planning and vision
BACKGROUND: Typical Design approach Experience in Design and Project management of PV-hybrid micropower plants in rural areas of southern Europe, Africa, Latin America, Pacific Technical specification for PV-hybrid micro-power plants (<100 kw, LV) partially adapted from IEC 62257 TS series Demand analysis and segmentation Standardized technical solutions with high PV penetration 10 yr. Service horizon with local operator and local capacity building Monitoring of systems to validate technology and the service
BACKGROUND: Typical Technical Specification DC coupled topology, high fraction of Renewable Energy generation System bus-bar voltage: < 75V DC (SELV) Battery: Pb-tubular, vented, DOD max =75%, A>3 days, 48V PV Charge controller: MPPT Inverter: sinusoidal > 85% +25W pilot inverter PV modules: crystalline CEI 61215-2 Data logging: based on CEI 61724 (JRC guidelines) Load electrical supply: Mainly standard AC quality single phase Load Management: user interface, automatic load disconnect Etc.
From single user to villages: MSG (Multi user Solar Grid) up to 150 kw.h/day Typical layout (DC bus-bar micro power plant+ac single phase grid )
AVOIDABLE DEFERABLE INTERRUPT. MODULABLE Profile 1- Daily Cycle rigid slim loads Typical load profiles Profile 2- Base Load 2a-Base Load 2b- Base Load Interruptible 2c- Base Load- Stand-by PROFILE LOAD TYPICAL DAILY RANGE (Wh/da y) 2a 275 275 A NO NO NO NO 550 1100 2b A NO NO YES NO 550 1100 2c YES NO YES YES 0 1100
Profile 3- Daily Deferrable load Typical load profiles Profile 4- Periodical Deferrable load Profile 5- Dump or ballast load
Two key points The main actor for load management is the user Training needed Load management requires measurement and broadcast of information on system status Power and Energy generation Power and Energy consumption Energy availability Battery status
Load management tools User information interface + training Automatic total load disconnect Automatic selective load switching Individual Energy limitation (multi user system)
User interface Active display Remote display Data logging
RESULTS OF INDIVIDUAL LOAD SENSITIVITY ANALYSIS (careful user: good operator) Wh/d 2600 2400 2200 2000 1800 1600 1400 1200 SL05028 1000 0 1 2 3 4 5 6 7 8 Hp Spring Summer Autum Winter DD (Wh) Spring-06 Summer-06 Autum-06 Winter-07
Electricity Dispenser / meter Metering and invoicing interface Energy and power limitation and guidance according to tariff contracted and generation status User pays for availability of energy, not for the consumed energy
Tariff variable charge ( /kwh) Sharing of energy among users Application and control of new tariff systems (progressive tariffs, EDA,...) Energy limitation according to tariff contracted Low consumption energy meters Incentives for active load management Flexibility in energy use sharing of energy between neighbours 1 0,8 0,6 0,4 0,2 0 Progressive tariff scheme 17 33 66 134 >134 Consumption blocks (kwh/month)
Sharing of energy among users
Monitoring Combination of user questionnaires and data logger User records: Satisfaction?? Electrolyte level in battery Black outs? Data logger: built-in device in power conditioner Hourly Data Storage (1 year): Average and total hourly values Parameters: all relevant energy flows solar irradiance information on battery (voltage, SOC, etc.) others
Typical monitoring data
Akkan, Morocco Examples MSG
Akkan, Morocco PV HYBRID POWER PLANT PV GENERATOR Installed PV capacity 5.760 Wp Module type 80 Wp 36 cell mono crystalline Number of modules 72 Inclination / orientation 43º / +5º S PV CHARGE CONTROLLER Rated power 6.000 Wp Control algorithm MPPT - Boost BACK UP GENSET Rated power 8,2 kva single phase Fuel Diesel BATTERY Number of elements (voltage) 24 (48V) Model Hawker 2AT1500 Capacity (C100) 1.500 Ah Autonomy 4 days INVERTER Voltage input / output 48 V DC / 230 V AC Rated power 7.200 W Harmonic distortion < 2,5% DATA LOGGER Memory / log frequency 300 kbyte / hourly Type of data Energy, voltage, radiation, etc. ELECTRICITY DISPENSER METER Input 230 V AC 50 Hz Maximum current 10 A Algorithm Configurable Daily Energy Deliverability STREET LIGHTING Number of lamps 13 Type 70 W hp sodium / 2 level electronic ballast Total power - high 910 W Total power - low 683 W INDIVIDUAL LOADS Households 275 Wh/day 23 Households 550 Wh/day 3 School 550 Wh/day 1 Mosque 550 Wh/day 1
Technology-PV hybrid power plant San Lorenzo, Ecuador (LA)
Technology-distribution microgrid Typical household San Lorenzo, Ecuador (LA)
User interface and loads San Lorenzo, Ecuador (LA)
Diakha Madina, Senegal
Diakha Madina, Senegal PV ARRAY PV installed power 3.150 Wp PV Module model PW750 75 Wp 12V Nº PV modules 42 Orientation/Inclination 0º S / 10º S PV Area 46 m 2 AVAILABLE ENERGY Available Energy (Wh/day) 4.803 Irradiation (ḠpHp) 5 HPS Month of design December BATTERY Nº elements 24 Battery type Tudor 6 OPzS 420 Capacity (C100) 672 Ah Day of autonomy 4 days CHARGE CONTROLLER Regulation capacity 4.000 Wp Mode of charge control MPP Tracker INVERTER Input / Output voltage 48 V DC / 230 V AC Nominal Power 3.600 W DC/DC Converter (12 V) 10A máxima de corriente Harmonic distorsion < 2% DATA LOGGING Memory / freq. of logging 300 kbyte / hourly PUBLIC LIGHTING Number 2 Type of lamp 70 W / electronic ballast PUMPING SYSTEM Power of the pump 1.100 W Flow 5m 3 /h Deep 49 m Height of the tank 7 m Tank capacity 20 m 3 BACK-UP GENSET Nominal power 4,2 kw single phase Fuel Diesel
Current situation in SSA
Current situation in SSA Low population density Remoteness from the public grid Low demand in electricity High energy losses on the transmission lines High costs of grid extension and connection High Operation and Maintenance costs
Current situation in SSA Many villages and households and villages not connected to the grid Existing mini grids running with Genset (many are not working) But essential to bring electricity, even basic needs (high value for the first kwh)
Short-term (0-2 years) Present and future potential Villages not connected to the grid, where the grid extension is too expensive and not cost effective: micro-grid for basic needs (health, school, water, etc) Villages with obsolete diesel generator because of the high running costs (Operation and Maintenance): refurbishing distribution grid, electrical installations, etc Medium-term (5-6 years) Villages not connected to the grid: extension of the mini-grid to private applications and productive uses Long-term (10 years onwards) Villages not connected to the grid: interconnection of several mini-grids between them or/and the national grid
Constraints and limitations Training and capacity building High costs of investment Critical number for maintenance Management of accumulated money Social organization may be a critical issue depending of the management model Unfair regulation (unfair regulations that discriminate against technologies that are especially suited to rural areas)
LESSONS LEARNED in 15 years of practice PV-hybrid micro grids are an acceptable long term option and expanding market Public subsidies in rural electrification must be technology neutral Typical average energy consumption is low but very valuable to users Demand limitation not a problem if EE appliances available Generation technology more and more reliable and adequate but... Load management is an important issue Stand-by loads in appliances dramatically increasing!! Operator recommended for long term security. Fixed user fees better User interface is critical!
antoine.graillot@tta.com.es