ITALIAN TECHNOLOGIES ON RENEWABLE ENERGY Italian innovative and best practices HYBRID POWER SYSTEMS An efficient solution to provide sustainable energy supply in rural and isolated areas Sofitel So Hotel, Bangkok, 21 st -22 nd March 2012 Speaker:
CONTENT Definition and application of HPS The concept of complementarity Energy sources of HPS overview of renewable energy technologies, conventional generators and energy storage systems Types of HPS off-grid, on-grid and mini HPS HPS architectures HPS configuration and design the optimization problem HPS market restraints and challenges Conclusions 2
DEFINITION OF HYBRID POWER SYSTEMS Hybrid power systems (HPS) are any autonomous electricity generating systems, incorporating more than one type of power sources, operated together with associated supporting equipment (including storage) to provide electric power to the grid or on site. Hybridization through combining different energy sources in one supply system offers the best possibility to use the locally available renewable energy sources. stand-alone systems island grids of small and medium ranges. 3
APPLICATION OF HPS HPS are an emerging technology for supplying electric power in remote locations. Off grid renewable energy technologies satisfy energy demand directly and avoid the need for long distribution infrastructures. HPS can provide a steady community-level electricity service, such as village electrification, offering also the possibility to be upgraded through grid connection in the future. Due to their high levels of efficiency, reliability and long term performance, HPS can also be used as an effective backup solution: to the public grid in case of blackouts or weak grids; for professional energy solutions, such as telecommunication stations or emergency rooms at hospitals. 4
ADVANTAGES vs. DISADVANTAGES OF HPS Advantages: Shelter consumers from temporary energy price volatility created by supply and demand mismatches. Increase the reliability of energy, thereby avoiding significant costs with power outages. Provide a cost-effective means to minimize the impact of intermittent resources. Decrease environmental impacts of energy supply. Disadvantages: More complex design, therefore increased design effort and more complexity in operation. More complex control systems are required for handling: power generation storage transmission usage options... higher costs 5
COMPLEMENTARITY (1/3) Supply pattern of different renewable energy sources can be intermittent but with different patterns of intermittency. Possibility to achieve a better overall supply pattern by integrating two or more sources,(usually including also a form of energy storage). Energy supply can effectively be made less intermittent, or more constant. The objective of using two (or more) power sources must be to reduce costs below the best obtainable from one source only, for the same availability. The main condition which must be satisfied for this to be possible is that of COMPLEMENTARITY!. 6
COMPLEMENTARITY (2/3) The complementarity of two (or more) sources needs to be looked at on both: short-term basis - Short-term patterns affect the day to day operation of a system, and may have important effects on systems with small batteries (around 1 day s energy storage). Implications for: battery sizing. genset control (timing and other conditions associated with starting and stopping the genset). long-term basis - Long term patterns have an effect on the sizing of system components, regardless of the size of battery storage. poor compelementarity allows little reduction in renewable generator size. good complementarity may allow a reduction in generator size. 7
COMPLEMENTARITY (3/3) - EXAMPLE Clean Electricity 24/7 simulation for California: geothermal, wind, solar and hydro together provide a match to an average power demand curve for CA for a given month (July in this figure). 8
ENERGY SOURCES IN HPS Gen-sets, small wind and photovoltaic systems are the three core technologies in hybrid power systems and they can be utilized as combination of any two together or even all three. HPS with two sources is called bivalent, with many sources multivalent. Biomass fuelled small/modular power plants (up to 5MW), small hydropower plants and fuel cells can be utilized with photovoltaic and/or wind turbines to produce a hybrid system. 9
OVERVIEW RENEWABLE ENERGY TECHNOLOGIES Wind Turbines (WT) A device that generates electricity from the wind is referred to as a wind turbine (WT). WTs work by capturing the energy of the wind by use of a rotor. Rotor blades convert the wind energy into rotational force, which turns a generator to produce electricity. The fluctuating nature of wind speed results in a fluctuating power output from a WT, which has to be taken into account when designing a power system. 10
OVERVIEW RENEWABLE ENERGY TECHNOLOGIES Small-scale Hydropower Plants (SHP) SHP are mainly run of rivers. Unlike many other RES, SHP can generally produce some electricity at any time on demand (for example it needs no storage or backup system), at least when an adequate flow of water is available, and in many cases at a competitive cost with fossil fuel power stations. 11
OVERVIEW RENEWABLE ENERGY TECHNOLOGIES Solar Photovoltaic Modules (PV) Solar Photovoltaic Modules ( photovoltaics or PV ) convert sunlight into electrical energy via the photovoltaic effect. Conceptually, a PV device is a solar-powered battery whose only consumable is the light that fuels it. If electricity is required outside daylight hours, or if extended periods of bad weather are anticipated, some form of storage or back-up system is essential. 12
OVERVIEW RENEWABLE ENERGY TECHNOLOGIES Biomass Products derived from living organisms wood, harvested grasses, plant parts, animal wastes. Biomass energy is stored chemical energy: solid, liquid or gaseous fuel, or any other electric or useful chemical product derived from organic matter (from plants or from plant-derived industrial, commercial or urban wastes, agricultural and forestry residues. Bioenergy is produced in a cycle, during which most of the carbon released is removed from the atmosphere and later on (through combustion) returned back to it. 13
OVERVIEW CONVENTIONAL GENERATORS AND STORAGE SYSTEMS Internal Combustion Engine (ICE) ICE generators (reciprocating engines) were the first among Distributed Generation technologies (developed over 100 years ago). Available for power generation in sizes ranging from a few kilowatts to over 5 MW. Advantages: Start quickly. Follow the load well. Good part-load efficiency. High reliability in general. Disadvantages: Maintenance costs are generally higher than comparable gas turbines. Not environmental friendly. At reduced loads, the heat rate increases and efficiency decreases. 14
OVERVIEW CONVENTIONAL GENERATORS AND STORAGE SYSTEMS Microturbines Microturbines are small electricity generators that burn gaseous and liquid fuels to create high-speed rotation that turns and electric generator. Microturbines entered field-testing around 1997 and began initial commercial services in 2000. Well suited for distributed generation application: Flexibility in connection methods. Ability to be stacked in parallel to serve larger loads (scalability). Provide stable and reliable power. Low emission. Reliable unattended operation. 15
OVERVIEW CONVENTIONAL GENERATORS AND STORAGE SYSTEMS Energy Storage Systems (1/2) Reasons for which is necessary to store electrical energy: Increasing power demand in case of overproduction. Fast generation in case of rapid peak demand. Optimization of renewable sources utilization. 16
OVERVIEW CONVENTIONAL GENERATORS AND STORAGE SYSTEMS Energy Storage Systems (2/2) There is no possibility for direct storage of electricity. Conversion to other types of energy is necessary. Possible solutions of storage systems 17
HYBRID COMBINATIONS AVAILABLE Researchers, developers and manufacturers are looking for ways to combine technologies to improve performance and efficiency of distributed generation equipment. 18
TYPES OF HPS Pure renewable hybrids: Typical pure renewable HPS consist of solar, wind and hydro energy sources (and battery). Where remoteness and/or difficulty of access make fuelling or servicing a genset prohibitively expensive (e.g. Telecommunications repeaters). Usually most expensive systems because of the need to oversize the renewable generators and storage). Hybrids with fossil fuel backup: The inclusion of a fuel genset has several important effects: Battery capacity may be reduced; Availability may approach 100% with much smaller RE systems capacity; Running costs due to maintenance and fuel use will increase; Environmental impacts such as noise and pollution will increase; Capital costs will be reduced. 19
PURE RENEWABLE HYBRIDS Schematic diagram of a typical renewable hybrid energy system containing solar, wind and hydro sources. 20
ON-GRID HPS Utility connected systems: Utility connected HPS avoid the need for electricity storage in batteries, by essentially using the utility as a battery system smart grids (74.000 small gen. plants in Italy, 95%PH in 2009). Permanent access to standard AC power No cost of battery back-up system. Utility interconnection fee (both ways). Utility connected systems with battery back-up: Combination of the stand-alone and utility connected systems Advantages of both. The design and installation of these systems is more complicated and expensive. Most efficient in providing constant, reliable electricity. 21
OFF-GRID AND MINI HPS (1/3) The price of conventional energy resources (candles, paraffin, gas, coal, batteries, fossil fuels) in remote areas is more expensive than in urbanised areas. Off-grid electricity from hybrid systems: The provision of grid electricity in rural areas is often associated with higher costs than off-grid remote area power supply technology options would be. Grid electrification in rural areas in some cases is financially inefficient and particularly due to the low consumption take-up in the remote areas. Off-grid technology options, single sources and hybrid power options can be an economic alternative to remote grid extensions. Off-grid electricity can be generated by: Single-source systems using: solar PV panels wind turbines generators micro-hydro plants fuel-powered combustion engine generator sets Hybrid systems, combining two or more types of the electricity generating sources. 22
OFF-GRID AND MINI HPS (2/3) Off-grid electricity from hybrid systems - example: FIRST project EC project - Fuel cell Innovative Remote System for Telecom Advantages: High efficiency values of fuel cells low maintenance low noise level clean exhaust gases. Disadvantages: Costs low reliability and short lifetime of fuel cells. 23
OFF-GRID AND MINI HPS (3/3) Hybrid system with mini-grid example: island of Stromboli (ITALY) Ginostra is an isolated village on the island of Stromboli (volcanic island). Normally there is a population of about 50 people in the winter rising to approx. 600 during July and August. System characteristics - PVs: 100 kw; Diesel: 160 kw; Battery storage: C10=3000 Ah, V=400 V; three inverter and static switch in parallel). To better use the production capacity of the HPS, a desalination system has been installed as periodical load to store water during the low occupation period and cover the demand in the summer. 24
HPS ARCHITECTURES (a) Centralized AC-bus architecture Generators and the battery installed in one place All connected to a main (same) AC bus bar before being connected to the grid. All energy conversion systems and the battery is fed to the grid through a single point. In this case the power produced by the PV system and the battery is inverted into AC before being connected to the main AC bus. 25
HPS ARCHITECTURES (b) Distributed AC-bus architecture The power do not need to be installed close to each other No need to be connected to one main bus bar. Sources are distributed in different geographical locations as appropriate and each source is connected to the grid separately. The power produced by each source is conditioned separately to be identical with the form required by the grid. The main disadvantage of this architecture is the difficulty of controlling the system. 26
HPS ARCHITECTURES (c) Centralized DC-bus architecture Utilisation of a main DC bus bar. The energy conversion systems that produce AC power (wind energy converter and diesel generator), deliver their power to rectifiers to be converted into DC before it is being delivered to the main DC bus bar. A main inverter leads to the AC grid from this main DC bus. 27
SYSTEM CONFIGURATION The way in which different electrical energy sources are connected will have an impact on the complexity of the HPS, the overall efficiency and the reliability of the electricity supply. HPS can be categorised into two main configurations: DC bus AC bus Many variations exist, including combinations of the two types or have both. Some issues to consider when choosing a configuration are: The size of system components. Generator set & power control requirements. Overall system efficiency. AC power quality. Redundancy and reliability issues. 28
HPS DESIGN PRINCIPLES Review of current practice The engineering practice for the design of HPS is based on two approaches: Site specific solution: tailor made approach where the system configuration, type of controls and control strategy are defined for each particular object. The site-specific solution incorporates an extremely high (unacceptable) engineering cost (only specialized design teams can perform this work) for designing and implementing a system. Changes in system characteristics, e.g. load growth or upgrade of components, if not predicted initially, will require an entire redesign of the system. System package solution: the expert knowledge of HPS specialists is used to design a package solution where the same combination of components and controls (system configuration) is operated according to a pre-defined set of rules (control strategy). Proper sizing of components is important to guarantee efficient operation in different applications. 29
HPS OPTIMISATION PROBLEM Given an electricity demand profile for a certain location with estimated weather conditions, together with the components, labour, transport and maintenance costs, find the system consisting of one or more electricity generation sources that covers the demand in a reliable way and has the lowest overall life cycle costs. The design and operation control problem is non-linear due to the non-linear component characteristics and the complexity of the HPS component interaction. (Translation: VERY DIFFICULT PROLEM!). Simulation programs are often necessary because of the interaction of the different electricity generation sources, storage and conversion elements, the switches and the consumer actions. This requires a computer based evaluation of a large number of combinations of system configurations, system operation strategies and their associated costs. 30
HPS MARKET Developed countries: Availability of technologies. Already very high levels of electrification. Opportunities generally limited to applications such as remote equipment power supply and off-grid homes and holiday homes. Developing countries: Limited availability of technologies. Scarce electrification. Opportunities fall mainly in village electrification category and the associated electricity needs such as public lighting, domestic electricity, rural telecommunications and water pumping. 31
HPS MARKET RESTRAINTS Relative complexity of HPS makes them more expensive to manufacture and install, leading to high capital costs. More standardised, modular systems help reduce capital costs and continued fall in the costs of system components. Decision makers are often unaware of the opportunities and benefits of HPS as a viable electrification option. The establishment of pilot projects and lobby groups will help to diminish this restraints. Many initial hybrid power systems project failed because of the install and forget about it attitude among the system providers. Although HPS require less maintenance than a genset there is now a growing realisation that post-installation services must be provided. Commissioning of test plants can be a step to restore confidence in HPS. 32
HPS MARKET CHALLANGES Increased sales volumes will reduce HPS costs, compared to direct competitors: grid extensions and stand alone gen-sets. Working with government and decision making bodies is vital to provide rural electrification solutions. HPS benefits must be presented at an early stage of the decision making process in order for them to be considered. In many cases, renewable components of HPS are complementary power sources, therefore joint agreements between companies can allow HPS to be developed, designed and constructed more efficiently. 33
CONCLUSIONS Governments in developing countries are looking for methods to electrify their country in a quick, cheap and reliable way. Electricity grid to remote villages and communities, stand alone gensets and renewable power sources have their own advantages and disadvantages. The electrification option that can combine all of the advantages of the alternatives and, at least partially, nullify their disadvantages is hybrid power systems. HPS taken into consideration by decision and policy makers in medium to long term climate change innovation and development strategies. Collaboration with developed countries, who have the technologies but don t have large local markets. Focus on R&D and human capital: the design problem of HPS is not only a technological problem, but principally an optimization problem that requires knowledge, expertise and... creativity! 34
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REFERENCES AND FURTHER READING Hybrid Power System Distance Learning Training HYPOS DILETR HYPOS-DILETR was a project funded in 2005 by the Leonardo da Vinci Community Action Programme on Vocational Training. It developed a European wide distance learning program on the design, operation and supervision of Hybrid Power Systems. Energy planners, decision makers, engineers working in power production and distribution, and the technical staff of local and regional energy agencies are now able to follow recognized courses throughout Europe in the design and operation of high quality and functional Hybrid Power Systems involving one or more Renewable Energy Technologies (RETs). www.cres.gr/hypos/ A path to sustainable energy by 2030 - Scientific American, November 2009 www.orizzontenergia.com Contact details: E-mail: carloft@gmail.com Telephone: +855 978159256 36