The Essence in Thermal Energy Storage

8/9/2019 The Essence in Thermal Energy Storage

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THERMODYNAMICSTHERMODYNAMICS

The Essence inThe Essence in

Thermal Energy StorageThermal Energy Storage

Maria Natalia R. Dimaano, D. Eng.Maria Natalia R. Dimaano, D. Eng.

Research Center for the Natural Sciences /Research Center for the Natural Sciences /

Faculty of EngineeringFaculty of Engineering

University of Santo TomasUniversity of Santo Tomas


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How to Store Energy ?m Electrical Energy


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How to Store Energy ?m Chem ical Energy

Power Storage Batteries


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FlywheelEnergy Storage Gravitational

Potential Energy

How to Store Energy ?

m Mechanical Energy

Energy inCompressed Spring


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Thermal Energy Storage


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Air conditioning24%

42%2%

18%

14%

Lighting

Motors

Others

Ventilation

Commercial and industrial electricity use in the Philippines


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Energy Storage Methods

Storage of free energy

the stored energy can be converted

without any loss into some other form

of energy.

Storage of thermal or heat energy

efficiency of conversion depends on the

temperature at which thermal energy isavailable


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Exergy = Workrev. Workambient surroundings

Exergy not an intrinsic material property It depends on the temperature of the

surroundings.

Traditional Thermodynamic Functions Energy Enthalpy

Entropy

Free Energy

Intrinsic Properties


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Facts about

Thermal Energy Storage (TES) An electrical load management and building

equipment utilization strategy, that reduces utilityelectricity demand and equipment first-costs.

Utilized as a demand-side management strategyby several utilities to shift electricity useassociated with cooling from on-peak periods tooff-peak periods.

designed to avoid high utility demand and energycharges from cooling during on-peak periodsassociated with time-of-use rates or real-timepricing rates


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Qi,Ti Qo,ToStorage

Box

To


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Cooler

Insulatedreservoir

Reservoir

Evaporator


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Full storage

discharging or complete solidification

is generated during off peak periods.

Partial storage discharging during off peak periods

based on the immediate thermal needs

on a specific peak time on the

following day.

Storage Strategies


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Thermal Energy Storage MechanismsThermal Energy Storage Mechanisms

Sensible Heat Storage - Thermal energy stored bytemperature change.

Latent Heat Storage - Thermal energy storedand released by areversible change of statein an isothermal process.

Thermochemical Heat Storage

- Thermal energy absorbedin chemical reactions.

Solid gas

Liguid gas

Solid liquid

Solid solid


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Sensible Heat Storage Materials

rocks

earth

water

ceramic bricks

Relatively cheap

safe

Universally available transportable

Mercedez Benz

American Airlines

Mc Donalds JC Penney Corporate

Headquarters

Sapporo Kousei

Hospital

Itabashi Ecopolis Center Osaka Municipal

Central Gym

Recognized Users


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Water

Ice

Heat

Exchanger

Heat

Exchanger

Types of Ice Storage Tanks

Ice on coil type Slurry type

Encapsulated type


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LatentH

eat Storage Materials inorganic compounds of

salt and water

paraffins and fatty

acids solutions of organic and

inorganic components

a fluid crystalline compound

formed when water is mixedwith a small quantity of an

organic medium or coolant

1. Salt Hydrates

2. Organic Materials

3. Eutectic Mixtures

4. Clathrates


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Phase change materials havehigh energy densities

Nearly isothermal charge anddischarge

Compactness of the storage unit

Less insulation required

Characteristics


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Concept of cool storage for possible

industrial application

Distribution

SystemHeat

Exchanger

Unit

Idletime

Electricity

Refrigeration

Thermal

Energy

Storage Cooled

water

Pump

Load

Cooledwater

Room or

Space UnitEnd-Use

(25 27rC)

Pump

Discharging4C

Warm water Cold

waterWater

Air

Cooledair

12 Ls1


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Thermochemical Storage Materials

Reversible chemical reaction

Adsorption

Direct hydration process

Metal hydrides in chemical heat pumps using

hydrogen as the working fluid

Metallic salts with ammonia

Thermochemical storage can also be useful in

energy transport applications where the

components can be transferred separately and

combined where thermal energy is needed.


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Condenser

Evaporator

StorageReactor

QcR

QrR

QC

QE

Cooling phase

Heating phase

Base operation of a solid absorbent

solar cooling system.


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Integration of base-load chiller, TES chiller,

and TES system models within a Cooling Loop.


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t

QuQ TESice

(!

Operation Modes

Charge or Discharge Rate

dormant mode: u = 0;

charging mode: u > 0; and

discharging mode: u < 0.

int, setpoLoopinletwaterpice

ice c

m

!


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Dormant Mode u = 0

Tinlet = Texit No storage capacity to

handle building cooling

loads

Charging Mode

u > 0

int, setpooopinletaterp

iceice

TTc

Q

!

u < 0

If discharge cannot

be provided by the

TES system,

Discharging Mode

= the TES water mass flow rate (kg/s),= TES cooling load (W),

TLoop setpoint = the supply loop setpoint water

temperature (rC).

ice

iceQ


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enteredtyavailabiliTotal

destroyedtyavailabiliTotalMeritofFigure !

availability of entering gas streams due to T &P being

greater than ambient

entropy generation by transient heat conduction within the

storage element

entropy generation due to convection heat transfer between

the gas and storage material

entropy generation during the dwell period due to transient

heat conduction within the storage material

availability destroyed by heat transfer between the exiting

gas and the environment during the storage period.

As functions of:


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ApplicationsApplications Building cooling/heating systems

Power utilization in space missions

Electronics

Coal fired stations

energy storage

industrial waste heat recovery

greenhouse heating


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Heating/cooling

source

Thermal

Energy StorageSystem

Heating/cooling

load

Rate of

thermal

Energy in

Rate of

thermal

Energy out

Rate of

thermal

Energy

production

+ = 0

Rate of exergy storage = Transfer by heat + Transfer by

shaft/boundary work + Transfer

by flow Exergy destruction


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Performance of TES System load

water/transfer fluid circulation

temperature ambient temperatures

water/transfer fluid flow rates


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Studies have always been concerned with

the choice of or continuous development of

thermal energy storage materials and

schemes to further improve the thermal

energy storage system performance.

discoveries often come from people straying outside the

normal bounds of their specialties: (J. Gleick on Chaos:

Making a New Science)

This research will help improve a critical

component of renewable energy, solartechnology, in the future. Increasing the use

of renewable energy is a clear way to help

meet our growing energy needs using

environmentally-friendly power sources.


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Discoveries often come from

people straying outside the normal

bounds of their specialties

(J. Gleick on Chaos: Making a NewScience)


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PCM SelectionPCM Selection

SystemPerformance

MaterialsCharacteristics

Working temperature Fusion/transition temperature

Energy density

Density

Heat of fusion/transition

Response to loadHeat transfer characteristics

Heat of fusion/transition

Thermal Efficiency

Behavior of fusion/transitionHeat of fusion/transition

Thermal stability

Compatibility with working fluid

Reliability

Thermal stability


Explosive/ignition reactivity

Thermal degradation


Life Expectancy

Thermal stability


ToxicitySafety



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! ei

dt

d

etoteitoti

CVCVe

hmhm

Wdt

dm

dt

d

,,

!

gen

CV

eeii ST

Q

smsmdt

dms

dt

dS

!!

Continuity Equation

Rate of change of total

energy from the energy

equation

Rate of change of entropy from the entropy equation

Exergy, Jm!* J : no flow availability


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? A

!*

ei

genCV

eeii

etoteitotiCVCV

mmsTh

STT

QTsmTsmT

dtdVPhmhmWQ

dtd

)( 000

0000

0,,

!

*

CVQT

T

dt

d 01

dt

dVPWCV 0

Transfer by heat at T

Transfer by shaft/boundary work

Rate of exergy equation


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Transfer by floweeii mm ]]

Exergy destruction genST 0

Rate of exergy storage = Transfer by heat +

Transfer by

shaft/boundary work+ Transfer by flow

Exergy destruction

]: specific flow exergy;flow availability

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The Essence in Thermal Energy Storage