Lecture 8: Energy Hubs

Question 1

Define the concept of the energy hub?

Answer 1

Energy hub can be defined as the place where the generation, conversion, storage and consumption of diffrent energy carriers takes place.

Question 2

The main purpose of introducing the Energy Hub Concept?

Answer 2

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

Question 3

The main aspects of an MES and use of an EH in it?

Answer 3

• 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

Question 4

If the EH has more than one energy carrier in the input or ouput then it is an …. EH

Answer 4

Hybrid EH can be defined as the place where the production, the conversion the storage and consumption from diffrent energy carriers takes place.

Question 5

INFO

EH models must use generation systems which can use an energy carrier, to meet more than one demand

Question 6

Evaluate the EH in terms of the Ressources.

Answer 6

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.

Question 7

What are the 4 major EH features?

Answer 7

Input, Conversion, Storage, Output

Question 8

DERs as power generation systems near the consumption site, result in lower energy costs, reduced transmission and distribution losses and higher energy efficiency.

Question 9

How about the hydrogen as a ressource in a energy hub in input?

Answer 9

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

Question 10

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

Question 11

Two main possible types of input to output connections in EH models:

Answer 11

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.

Question 12

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?

Answer 12

CHP uses one Energy Carrier to produce Elerctricty AND Heat.
Option to Peak Shave or DR in an SEH.

Question 13

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

Question 14

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.

Question 15

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

Question 16

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.

Question 17

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

Question 18

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

Question 19

What does an aggregator do?

Answer 19

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.

Question 20

Participation of aggregators in the electricity market, contributing to …… and ….. from a market perspective

Answer 20

Participation of aggregators in the electricity market, contributing to increased competition and liquidity from a market perspective

Question 21

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)

Answer 21

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)

Question 22

Aggregators are:

Answer 22

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

Question 23

Distinguishing between …. and …. demand side flexibility

Answer 23

Distinguishing between implicit and explicit demand side flexibility

Question 24

Implicit demand side flexibility , or price based, referring to prosumers ….

Answer 24

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.

Question 25

**Explicit **, or incentive based demand side flexibility referring to prosumers ….

Answer 25

receiving direct payments to change their consumption or generation patterns upon request, which are triggered, e.g., by the activation of balancing energ requests, differences in electricity prices, or network constraints.

Question 26

which selected flexibility
value chain services are there for aggregation?

Answer 26

Congestion management:
Voltage control:
Spot market Day ahead trading:
Self balancing / Passive balancing:

Question 27

Explain the effect/use of aggregation on these selected Selected flexibility value chain services

Congestion management:
Voltage control:
Spot market Day ahead trading:
Self balancing / Passive balancing:
Primary and Secondary Control:

Answer 27

Congestion management:
Aims at avoiding thermal overload of system components, which may cause failure, by reducing peak loads.

Voltage control:
It occurs when DERs generate significant amounts
of energy increasing the voltage level in the grid.
The use of load flexibility can reduce the need for grid investments or mandatory generation curtailment

Spot market Day ahead trading:
Shifting loads or dispatching generation from a high
price to a low price period on a day ahead basis
Contributing to reducing the overall electricity purchase costs

Self balancing / Passive balancing:
Is the reduction of imbalances by the Balance Responsible Party (BRP) within its portfolio and within one imbalance settlement period to avoid imbalance charges.
In passive balancing , the aggregator’s BRP helps reducing the imbalance for the whole
control area by deviating from its own forecast concerning the energy load diagram.

Question 28

Which 4 Barriers are there and what are their main aspects ?

Answer 28

Regulatory barriers: Lack of the new policy frameworks.

Technical Barriers:

Market Barriers:The time period between bidding and activation of automatic secondary control is too long

Social Barriers:The low acceptance of smart meters by consumers as a social barrier
Lack of trust between the DR provider (company) and the buyer (e.g., demand response aggregator) which may be jeopardized in several dimensions:

Question 29

To overcome the identified barriers, a strategy prioritizing crucial aspects should be in place, namely:

Answer 29


Revision and adaption of the rules for the provision of operating reserves;

Support to the roll out of smart metering systems;

Development of standardized solutions for smart meter data access , including
solutions for sub metering;

Lowering the entry requirements in spot markets for relatively small market parties;

Development of a framework for the provision of services at the distribution level.

Question 30

How can be the buisness model of the aggregator be described?

Answer 30

*
The aggregator s business model consists of aggregating flexibility from the consumers and trading it with other actors through market mechanisms.

The aggregator may operate outside the conventional energy supply chain as a
third party aggregator or may be a balance responsible parties/retailer:

Enable to participate in frequency regulation services or help to solve grid congestions
by selling flexibility to the TSO or the DSO;

Enable to assist balancing the BRPs ’ and retailers ’ portfolio.

Question 31

Depending on the way the aggregator positions itself, its objectives may also change accordingly

Answer 31

The third party aggregator takes advantage of the consumer s flexibility by selling
the aggregated flexibility to different actors, though its customers can contract the
energy provision from different retailers.

The role of the third party aggregator as a frequency regulation service provider and
congestion management to the TSO/DSO by trading the shifted energy in intraday
markets.

The disadvantage of this model is the possible creation of new imbalances due to the
flexibility activation called by the aggregator.

Question 32

UE08

Energy hubs as a main part of future energy networks:

Can provide a …

Can be seen as local …

Can be implemented in different ….

Answer 32

great opportunity for energy production, conversion and storage in such coupled infrastructures for system planners, operators and prosumers to move towards more energy efficient and flexible systems

concentrated set of energy infrastructure

dimensional range from a single household
up to an entire city model

Question 33

UE08

Energy hubs as a main part of future energy networks

Integrating different energy carriers in an energy hub helps …

Can enable energy users to flexibly switch the energy sources with accordance ….

Converting different energy carriers to other forms provide accumulation of larger amount of renewable energy and …..

Total operational costs can be substantially ….

Answer 33

system operator to maximize social welfare in a greater optimization space

to different energy prices

reuse of them in the future

reduced and a large amount of investments costs could be saved

Question 34

UE08

Energy Hub Applications in Residential Sector because of:

Answer 34

Because the residential areas stand for the consumption of a large amount of the total energy consumption in a country and there is a huge energy losses due to the long transmission ways, poor management of the consumption of the consumers, the lack of controllable res. loads.

Raising energy prices due to the resource constraints, increasing energy demand, and markets deregulation need for increasing energy efficiency

Raising energy prices due to the resource constraints, increasing energy demand, and markets deregulation need for increasing energy efficiency

Question 35

Energy Hub Applications in Commercial Sector because of:

Answer 35

Becauese of the operation of CHP units in the commercial buildings with their high efficiecy and multiple energy carrier output.

Efficiency improvements such as successful participation in the DSM programs

Question 36

Energy Hub Applications in Indutrial Sector because of:

Answer 36

Largest primary energy consumer
Possible efficiency improvements such as Technical and technological improvements, Industry Energy Management System (IEMS): integrating management to determine the energy consumption when and where needed

Benefiting from energy saving methods such as CHP , waste heat recovery, DSM participation, and integration of RES