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Introduction to subsySf6mS - cu nu HH HH ng Hi nh ni Hi Bi Ki Ki Ki BH 14
An electrification system qualifies as a subsystem when it meets specific criteria: it must ensure a reliable power supply (production subsystem), facilitate electric power distribution (distribution subsystem), and deliver services to users (demand subsystem), all while adhering to various constraints that impact all subsystems.
1) individual Electrification Systems (IES) for single users/loads incorporate two subsystems: e an electrical power production subsystem, e ademand subsystem for utilizing this electrical power
2) collective Electrification Systems (CES) for multiple users incorporate three subsystems: e an electrical power production subsystem (rural micro-power plant); e a distribution grid for sharing this power to individual users (rural micro-grid); e ademand subsystem including home wiring and user’s electrical appliances for all individual users
Subsystems can be managed by various individuals or organizations, while in some instances, a single entity may own, operate, and utilize the entire system.
Functional description of a production subsysfem - con nen 15
A production subsystem is designed to provide electric power and energy to individual or multiple permanent customers This generating subsystem must effectively fulfill its role, even in the face of uncertainties regarding the availability of renewable and fossil energy sources, while also managing the consumption patterns of its customers.
The primary technical objectives of the installation are to efficiently produce and store energy in a cost-effective way, particularly when utilizing renewable energy (REN) sources.
— to give precedence to use of REN where they are locally available,
— to store energy from the REN sources whenever they are available,
— to use the back-up energy sources (generator sets) to meet the specified level of service when REN are not available or sufficient
4.4.2 Detailed functions to be achieved by a production subsystem
From a functional view point, a production subsystem is a system capable of:
Ensuring a power supply service consisting of: a) Generating electric power
The different sources and architectures are described in IEC TS 62257-2
This function encompasses all essential elements for generating electric power that meets the required specifications of voltage, frequency, harmonics, power, and customer consumption, in line with the quality of service standards outlined in IEC TS 62257-2.
This function covers: e energy conversion from primary energies; e energy storage (when applicable); e electric conversion from d.c to a.c (if necessary); e energy measurement
With adequate supply and maintenance, the system can be effectively designed to fulfill the community's electrical demands affordably Additionally, it is essential to ensure the provision of electric power to the distribution subsystem.
This function guarantees that energy produced is delivered to the interface with either the collective or individual distribution system, adhering to contractual obligations Additionally, it involves the management of energy resources effectively.
The amount of energy available for consumption by users is inherently limited due to the availability of primary energy sources, such as solar radiation and fuel, as well as the constraints of energy storage capacities.
Effective resource management is crucial for optimizing energy use, minimizing losses, and ensuring that energy flows meet both customer needs and equipment longevity Additionally, it is essential to reduce reliance on fossil resources whenever possible.
Effective energy management involves overseeing energy production, storage, and distribution, as well as controlling genset operations when applicable Additionally, it is crucial to provide information regarding the operating conditions of the installation.
The installation is essential for equipping users and operators with the necessary information to manage energy production and consumption effectively, benefiting both individual interests and the wider community.
4.4.3 Detailed performances criteria to be achieved by a production subsystem
Each criterion shall be developed in order to express the quantitative objectives to be obtained for the sites studied
The information should be presented in accordance with the general model given in Annex A.
Functional description of a distribution subsysfem .- cu nen sex 16
4.5.1 Detailed functions to be achieved by a distribution subsystem
(or rural micro-grid) Providing an electric power distribution service consisting of: a) Connecting the rural micro-power plant to the application points
This function consolidates all necessary elements to provide terminal application points from rural micro-power plants, while also adjusting to the diverse energy needs of various customers, including individuals, businesses, local authorities, and public lighting.
Methods should be put in place to account for and monitor rural micro-grid distribution losses b) Not degrading the level of quality
When designing a rural micro-grid, it is essential to consider the availability and quality of supply objectives Additionally, incorporating necessary protection measures for the micro-power plant is crucial to ensure safe operation.
To ensure the safety and efficiency of the micro-power plant, it is essential to implement protective measures against harmful short circuits and electrical impacts Additionally, localizing the effects of short circuits or system overloads is crucial to prevent disruptions to the entire micro-power plant and its clients Furthermore, it is important to execute the load-shedding decisions made by the rural micro-grid manager effectively.
The rural micro-grid function is designed to adhere to management rules, incorporating an automatic system to ensure reliable energy delivery to users while maintaining the longevity of the production subsystem equipment.
The design of the rural micro-grid shall permit modification of its configuration according to decisions based on information given by the energy management system
We permit any mutually agreed modifications, control the activation and deactivation of circuits linked to the generator set when necessary, prioritize the shutdown of circuits based on established rules, and supply relevant information to the operator while ensuring adherence to the user's contract.
It shall be possible to apply commercial rules in conjunction with the technical service of making electricity available (connect/disconnect the users under contractual rules)
The use of advanced monitoring and accounting devices can greatly assist in forcing the compliance of contract
4.5.2 Detailed performances criteria to be achieved by a distribution subsystem
It is impossible here to recommend any general quantitative objectives (performance levels)
The essential task will hence be to define qualitative objectives (performance criteria) in a functional specification before determining the technical dimensions of the system
Each criterion shall be developed to express the results to be obtained for the system type studied
A standard method for outlining the functional features of a rural micro-grid is presented in Annex B, which includes a performance sheet detailing the connection of the rural micro-power plant to various application points.
Each rural micro-grid entails aspects specific to the site concerned
The architecture of a rural micro-grid will be designed based on specific criteria, including the number of energy delivery points required to meet the identified needs.
The determination of principal and secondary trunk feeders is based on user distribution, maximum line dimensions, and system losses Additionally, it is essential to have multiple opening points available, allowing for the isolation of all or part of the rural micro-power plant's micro-grid.
Dimensioning is determined by several key factors, including the quality level of energy distribution as per IEC TS 62257-2, the peak power requirements of the receivers at each delivery point, the agreed service quality with users—particularly the maximum allowable voltage drop between the rural micro-power plant and customers—and the mechanical constraints of the surrounding environment.
Figure 2 is a functional diagram of a radial structure for a rural micro-grid
Interface micro-power plant/micro-grid
Figure 2 — Functional diagram of a radial structure for rural micro-grid
Functional description of a demand subsysfem - nen 18
Detailed functions to be achieved by a demand subsystem (or rural micro-grid):
Providing an electric power to applications consisting of: a) Interfacing with the distribution system
This function consolidates all necessary components to guarantee that user installations are provided through the distribution system, encompassing functions related to contractual obligations like payment and metering systems Additionally, it facilitates the distribution of energy to various appliances.
Here are included all the electric functions able to provide, switch on/off electricity from the distribution system interface to the final user’s application
NOTE In some projects, this function could include the supply of the appliances (such as lamps for example).
Constraints to be complied with by production distribution and demand
subsystems a) Matching the characteristics of the site
This function encompasses all constraints, including geographical, technical, economic, and sociological factors, along with site-specific human elements that must be addressed in the design and performance of the facilities Additionally, it is crucial to ensure the protection of individuals and assets.
The equipment shall be designed to control risks to individuals, operators or third parties
In addition, they shall be protected from the faults that may occur on the different parts of the installation c) Minimizing special maintenance to make energy available
That means: e making easy installation; e facilitating operating conditions; e facilitating maintenance; e facilitating dismantling; e facilitating expansion
For reasons of cost, it is imperative that the installation can continue to operate without requiring frequent intervention by specialists d) Complying with regulations
This function groups together all the technical and legal constraints to which the installation shall comply to be usable e) Complying with the operator and user duties
This specification stipulates the rights and obligations of the operator and users It is generally drawn up by the national and/or regional institutional authority
In REN powered systems, resource availability can fluctuate significantly Effective energy management is crucial to ensure that users receive the promised service under optimal conditions while preserving the equipment's operational lifespan.
This Clause 5 describes the impact of energy management assumptions and the technical choices that they imply on system sizing
Figure 3 illustrates the role of energy management and safety as transverse functions in the operation of the system
REN Energy energy Energy Electricity User supply
Other energy - resources Energy production |
A system in accordance with the site characteristics
Figure 3 — Functional impact of energy management and safety
5.2 Functional description for an energy management of an isolated system
To manage energy in REN systems, a number of functions shall be considered, as described below: a) Adequate management of resources and needs
Effective energy management in isolated systems requires balancing renewable energy production with consumption to meet demand This approach ensures compliance with the commitments of service providers, such as project developers and operators, while prioritizing the best interests of users Emphasizing the use of renewable energy sources is essential for sustainable management.
Effective energy management in isolated systems prioritizes renewable energy generation to minimize fossil fuel consumption and reduce operational costs, while also enhancing the service life and performance of equipment.
Effective energy management in an isolated system requires prioritizing equipment protection to ensure a long service life This approach maximizes the value of capital investments by aligning them with the intended operational lifespan of the equipment Additionally, it is crucial to manage the storage system efficiently.
Quality of battery management has a very high impact on battery life, on the system’s level of performance, and life cycle cost e) Managing the available quantity of energy
Effective management of energy in an isolated Renewable Energy (REN) system involves maximizing the utilization of limited renewable resources and optimizing the distribution of the generated electrical energy among various users and appliances.
In a single-user system, over-consumption will interrupt supply The user quickly learns how to use the energy of the system correctly
In a multi-user system, such as a rural micro-power plant linked to a micro-grid, it is essential to manage energy storage effectively to benefit the largest number of users while safeguarding the common installation Various strategies can be employed, including limiting grid availability to specific time periods, which restricts the amount of energy distributed based on the network's operational hours Alternatively, maintaining the grid's operation for extended periods can enhance service quality, but it necessitates capping both the power available to each user and their energy consumption during certain times, potentially managing energy distribution over one or several days Additionally, implementing a suitable tariff structure can help regulate energy use, allowing for system expansion funded by larger consumers, with a recommended step or graduated tariff to provide affordable power to customers while charging higher rates to those consuming more energy.
In electrochemical storage systems, effective energy management involves replenishing stored energy In systems utilizing renewable energy sources, often called direct drive devices, storage typically takes the form of water in pumping applications or ice in ice production systems Additionally, it is crucial to manage the quality of the electricity generated.
Controlling the quality of electricity delivered to users is a crucial aspect of energy management, defined by several criteria: voltage level and its variation range, d.c voltage ripple, a.c frequency and its voltage variation range, and the harmonic ratio of a.c voltage, which is influenced by the inverter or generator quality System designers must ensure these conditions are met Additionally, Clause 6 addresses how energy management assumptions affect system sizing, highlighting the importance of demand-side management.
To optimize the limited energy output of micro-power systems utilizing renewable energy sources (REN), it is essential to employ high-efficiency, low-consumption appliances and leverage all available energy demand control resources.
6 Expected results from the sizing process
Clause 6 presents recommendations relative to the information to be provided in a sizing data report
Designers have the flexibility to select their preferred sizing methods, but the primary goal is to establish a framework of assumptions that outlines the sizing process This framework should also specify the documentation that needs to be provided to the project developer.
Common rules for the presentation of results should be applied by plant designers, so that any project developer can objectively compare the various offers related to this specification
Clause 6 gives transparent technical and economic criteria for "suitable" sizing, thus making it possible for the offers to be easily compared
6.2 Participants in the sizing process
A plant sizing process requires a number of active participants, see Table 5
Special attention shall be exercised in order to request these participants to provide the project with information/decisions they hold or are responsible for
Table 5 — Participants in the sizing process
Nature of participants Liabilities of the participants along the sizing process
User Expresses electricity demand needs
Project developer Defines the requirements to be fulfilled
Engineering consultant Assists the project developer in specifying the project and reviewing design proposals Project implementer Establishes proper design and sizing
6.3 Elements for comparing various design proposals
All design proposals should be based on the same general specifications
When comparing different design proposals, it is crucial to evaluate several key factors: the assumptions underlying each design, the technical specifications and energy predictions derived from the sizing process, and the measures implemented to mitigate the risk of system outages Additionally, the discounted costs of the proposed equipment, the designer's credibility through evidence of accurate design calculations, and the identification of the system class should be considered Furthermore, the designer's experience in the field and any project-specific criteria relevant to the developer are also important aspects to assess.
Subclause 6.4.2 provides an outline for the types and quality of information that should be provided as part of the project development documentation
The proposal must include a commitment to supply the necessary energy to meet user demands, along with assumptions regarding demand and renewable resource data It should describe any severe weather events and the measures taken to mitigate outage risks Additionally, the proposal must provide technical specifications, energy outputs, and a detailed breakdown of costs, including all economic assumptions Finally, documentation of the design warranty is essential.
These commitments are presented in IEC TS 62257-2, but can be summarized as major points in Table 7
To size the production subsystems, the project implementer should consult with the project owner to determine a set of relevant indicators
Some examples of these indicators are: e users’ power “satisfaction factor"
Plant sizing focuses on balancing production probabilities with available energy resources Users can expect a defined power supply and energy duration at any chosen time, adhering to established power requirement assumptions This approach ensures a reliable forecast coverage for renewable energy investments.
This rate of coverage is as follows:
Probable quantity of energy this plant can produce through RENs |
Quantity of energy desired to be consumed °
(month by month) e Other criteria could also be considered, depending of the perspective of the different participants involved in the project, as suggested in Table 6
Table 6 — Perspectives to be considered
Project developer Owner Operator User
The Technical System is designed for easy operation and maintenance, ensuring that power is available as needed It operates at the requested service level and adheres to the equipment life specified in the contract.