Lecture 8: Energy Hubs Flashcards
Define the concept of the energy hub?
Energy hub can be defined as the place where the generation, conversion, storage and consumption of diffrent energy carriers takes place.
The main purpose of introducing the Energy Hub Concept?
the main purpose has been moving to an MES in order to benefot from the synergy of various energy carriers, non-hierachial structure and integrated managemennt off diff. energy infrastructures
The main aspects of an MES and use of an EH in it?
- the move towords MES to benefit from the synergy of different energy carriers
- the move towrods non hierachical structures
- the move towords integrated and interconnected systems
EH for reaching these goals with an conversion and storage of energy carriers in an integrated unit
If the EH has more than one energy carrier in the input or ouput then it is an …. EH
Hybrid EH can be defined as the place where the production, the conversion the storage and consumption from diffrent energy carriers takes place.
INFO
EH models must use generation systems which can use an energy carrier, to meet more than one demand
Evaluate the EH in terms of the Ressources.
The low efficiency of the conventional PPT leads to an decrease in overall system efficiency. For Example the tpycal Coal Thermal PPT has an overall efficiency of 28% of its primary energy resoruce reaching the end customer.
These can be reduced by combination with energy hubs. Because the main advantage of an EH is the efficient use of CoGeneration in order to make the optimal use of energy carriers.
What are the 4 major EH features?
Input, Conversion, Storage, Output
DERs as power generation systems near the consumption site, result in lower energy costs, reduced transmission and distribution losses and higher energy efficiency.
How about the hydrogen as a ressource in a energy hub in input?
Production of hydrogen in EH with an optimal interaction between coordinated EHs, results in minimum cost and emmisions in the urban energy system. Problems related to hydrogen production from fossil fuels include
CO 2 generation and requirement of carbon capture & storage (CSS) systems
High costs of produced hydrogen from RES
INFO
Despite the diffrent energy carriers the realization of EH relies on diffrent energy carriers being connected
The electricity and gas grids with the highest share in EH inputs
Reflecting the dependence of the EH models to the electricity network
The main grids in the EH models for distributing electricity and gas
Natural gas grid as the second largest share in EH inputs after the electric grid
Main fuel for high efficiency CHP technologies
Less pollution than other fossil fuels such as coal
Two main possible types of input to output connections in EH models:
Direct connections: typically used to convey an energy carrier to the output without conversion or change in its quality.
Conversions: converters are used to convert energy carriers to other types for use in the output.
INFO
Many converters, such as transformers, pumps, gas turbines are used only to covert one type of energy carriers. Energy Hubs are made in the use of various energz carriers to meet diffrent demands. Therefore
EH must systems which can use an energy carrier to meet more than one demand. Give an Example?
CHP uses one Energy Carrier to produce Elerctricty AND Heat.
Option to Peak Shave or DR in an SEH.
INFO
Fuel Cells
One of the most importent and pomising renewable systems that can be used in polygeneration system is fuel cell. The Fuel cell use a variaty of fuels such as hydrogen use a variety of fuels such as hydrogen, biogas, methanol, natural gas, etc
In a hydrogen based fuel cell, electricity, heat and water can be produced from hydrogen and oxygen as inputs.
Advantages of the fuel cell over other conventional energy converters:
Lower emissions and environmental pollution
Higher efficiency, easy installation, reliable operation
Decentralized and distributed energy generation
BUT High cost, low power density, andquestionable durability
Electrochemical heat generated in an Fuel Cell can be used for heat applications
INFO
ESS
Thermal Energy Storage has been used most widely due its lower cost compared electrical storage.
Installation of ESS , either on the input or output side
Installation of gas storage usually on the input side.
Installation of electric and hydrogen storage on the input and the output side
Installation of thermal storage usually at the output side
Increasing Storage size results in lower system costs.
INFO
Consumption
Most EH Models uses on the supply of electricity and heat demands and have paid less attention to other demands.
DR refers to plans for changing the pattern of consumption through price changing over time.
The trend of current energy systems is towards demand side management (DSM) and control of it along with the use of technologies like DER.
DSM as an appropriate method for managing demand in different sectors,
especially the industrial and commercial sectors, including:
Load growth , energy savings, energy efficiency, and DR programs
Energy Hub applications Residential
Residential sector, consuming a significant part of the produced energy in each country
E.g., 22 % of the total energy consumption in the U.S.
Considerable energy losses in the residential sector due to:
Extensive distribution and long transmission networks
Poor management of consumption by consumers
Raising energy prices due to the resource constraints, increasing energy demand,
and markets deregulation need for increasing energy efficiency
Home energy management system (HEMS) as a solution for raising energy efficiency
Using parameters such as energy market conditions , weather conditions,
temperature , etc. to produce an optimal scheduling of energy production and
consumption.
Energy Hub applications Commercial
Optimal planning and size selection of multi generation systems in commercial
buildings
Operational optimization of CHP units in the commercial buildings
Efficiency increasing such as successful participation in the DSM programs
critical for efficient energy consumption and environmental impact reduction
Energy Hub applications Industrial
The industrial sector, with a 52 % share, is the largest primary energy consumer
Growth of energy consumption by an average of 1.4% per year from 2010 to 2040
Methods for efficiency enhancement in the industrial sector:
Technical and technological improvements: energy audits, use of technological
methods such as variable speed control for motors, waste heat recovery, CHP,
use of higher efficiency equipment
Policy making and behavioral training: government policies to encouraging industry
owners to improve their efficiency, subsidizing the integration of RES, rules and
deterrent penalties such as carbon taxes, employee training, and developing a culture of
productivity
Industry Energy Management System (IEMS): integrating management to determine
the energy consumption when and where needed, and minimizing the energy costs and
environmental impacts without affecting the quality and quantity of the provided goods
and services
What does an aggregator do?
An aggregator pools distributed units and markets their generation capacity (generation plants) or demand-side flexibility (electricity consumers) on the spot market, balancing power market and possibly further markets. For this
purpose, the aggregator provides recommendations (or control signals) for the units’ generation or load profile.
Demand response aggregators are aggregators that (also) market demand-side flexibility.
With utilization of optimization models he tries to make a optimal management of flexible energy ressources to aim diffrent objektives.
Participation of aggregators in the electricity market, contributing to …… and ….. from a market perspective
Participation of aggregators in the electricity market, contributing to increased competition and liquidity from a market perspective
Several definitions of aggregators including:
……. : negotiate more advantageous contracts with retailers on behalf of a large set of consumers by making the most of the scale effect
…… : gather the load flexibility of consumers of different types, namely residential sector
…… : group small generators as virtual power plants (VPPs)
Several definitions of aggregators including:
Demand aggregators : negotiate more advantageous contracts with retailers on behalf of a large set of consumers by making the most of the scale effect
Load aggregators : gather the load flexibility of consumers of different types, namely residential sector
Production aggregators : group small generators as virtual power plants (VPPs)
Aggregators are:
companies acting as intermediaries between electricity end users, DER providers and power system players , aiming to exploit the services associated with flexibility management .
They enhance system flexibility with the ability to exploit the potential of flexible resources
Distinguishing between …. and …. demand side flexibility
Distinguishing between implicit and explicit demand side flexibility
Implicit demand side flexibility , or price based, referring to prosumers ….
choosing to be exposed to time varying electricity prices or time varying network access tariffs that reflect the value and cost of electricity in different time periods.
