Concentrated solar thermal power (CSP) offers a clean renewable source of energy. Combined with energy storage, CSP can be dispatchable, on-demand power, decoupling solar energy supply with consumer energy demand, which is currently difficult with other renewables. Current thermal energy storage methods such as sensible or latent heat are currently cost-prohibitive due to low energy density. Thermochemical energy storage offers a potentially game-changing approach to storage thermal energy in the form of chemical bonds for later release. Thermochemical storage can be orders of magnitude more energy dense than previously explored energy storage methods. Here we explore a reversible decomposition-carbonation reaction involving SrCO3/SrO and CO2.

HPR-20 QIC R&D

The Hiden HPR-20 QIC R&D specialist gas analysis system is a bench-top mass spectrometer for the monitoring of evolved gases and vapors.

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Solar Thermochemical Energy Storage

SEM image of porous SrO/SrCO3 sample 8

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A NA L YTICA L

Abstract: Thermochemical energy storage is the next step in creating a self-sustaining society because it allows for energy supply to meet the electricity demand. Chemical bonds provide much higher storage capacities than the conventional energy storage methods; renewable storage schemes with greater energy storage density will potentially have a faster path to economic viability. A potential thermochemical storage cycle lies in the carbonation/decomposition of SrO/SrCO3. It offers the prospect of capturing thermal energy and releasing it at temperatures above 1200°C. One of the fundamental aspects of the project depends on the amount of surface area of the physical structure. To obtain an optimal amount of surface area, the current project involves creating a matrix through the mixing of heat treated SrO and decomposition of sacrificial carbon. The temperatures at which the SrO is being heat treated varied along with the size of the particles being used; also the ratio and size of the carbon particles are being varied to find the optimal structure with the most surface area.

SrCO3 ↔ SrO + CO2(g)

Reversible No catalysis High temperature (~1200°C)Safe

Joanna Julien, Jeremy Grunewald, Kelvin Randhir, Nathan Rhodes, Conrad Cole, Nick AuYeung, Like Li, Renwei Mei, David Hahn

AcknowledgementsWe are very appreciative of funding from Hiden Analytical for participation in this poster session. This work was funded by the U.S. Department of Energy Sunshot Initiative as part of the ELEMENTS program, award DE-EE0006534.

Future Work

Parameter Level Selected Values

A Heat treatment temperature (TH)- 1235 °C+ 1400 °C

B SrO particle size (S) - 25 µm -38 µm+ 106 µm -125 µm

C Graphite particle size (Sg)- 25 µm -38 µm

+ 106 µm – 125 µm

D Mass ratio of graphite to SrO (r) - 0.2+ 0.7

E Structure formation temperature (Ts)- 1100°C+ 1300°C

Preliminary data showing dynamic cycling between 1100 and 1300°C at 10°C/min. pCO2 = 0.33 bar

Ar

Heat Exchanger

Mass Flow Meter

Mass Flow Controllers

High Temperature Furnace

He

CO2

Bed

Pressure transducer

Hiden HPR-20 MS BPR

Investigation into carbonation at elevated pressure

*SEM image of porous SrO/SrCO3 sample 8.

Objective: To find the variable/s that most affects the energy density. It is hypothesized that an optimized amount of surface area will maximize the energy density.

0

500

1000

1500

2000

2500

3000

3500

4000

0 1 2 3 4 5

Ener

gy D

ensi

ty, [

MJ/

m3 ]

Cycle

123456789101112131415-115-21625-38 HT powder106-125 powder20% Polymorphic

Energy Density of Samples

Z-value of the Parameters

*A baseline of 95 percent.

Correlation of results: Lenth’s Method

Procedure:1. A matrix was created

2. Heat treat the SrO

3. Crush and sieve the materials to the appropriate sizes

4. Mix the SrO and graphite to the appropriate ratios

5. Evaluate the reactivity of the samples using a thermo gravimetric analyzer (TGA)

Conclusion: With 5 cycles done with the TGA, the assumption is that the energy density will be stable with continued cycles for each sample. The sample that showed the most promise was sample 15 in terms of energy density. The energy density of 15 started off around 3500 MJ/m^3 in the first cycle and tapered off to just above 1500 MJ/m^3, about 7% higher than the base powder. When comparing the effects of the parameters alone and together, the data shows that both the size of the SrO particles and the graphite particles create a large effect on the energy density. Surface area appears to have an affect on energy density. The next question should be what stabilizes the energy density ?

Solar Thermochemical Energy Storage

Abst

ract

:The

rmoc

hem

ical

ene

rgy

stor

age

is th

e ne

xt st

ep in

cr

eatin

g a

self-

sust

aini

ng so

ciet

y be

caus

e it

allo

ws f

or e

nerg

y su

pply

to m

eet t

he e

lect

ricity

dem

and.

Che

mic

al b

onds

pro

vide

m

uch

high

er st

orag

e ca

paci

ties t

han

the

conv

entio

nal e

nerg

y st

orag

e m

etho

ds; r

enew

able

stor

age

sche

mes

with

gre

ater

ene

rgy

stor

age

dens

ity w

ill p

oten

tially

hav

e a

fast

er p

ath

to e

cono

mic

vi

abili

ty.

A po

tent

ial t

herm

oche

mic

al st

orag

e cy

cle

lies i

n th

e ca

rbon

atio

n/de

com

posit

ion

of S

rO/S

rCO

3. It

offe

rs th

e pr

ospe

ct o

f ca

ptur

ing

ther

mal

ene

rgy

and

rele

asin

g it

at te

mpe

ratu

res a

bove

12

00°C

. O

ne o

f the

fund

amen

tal a

spec

ts o

f the

pro

ject

dep

ends

on

the

amou

nt o

f sur

face

are

a of

the

phys

ical

stru

ctur

e. T

o ob

tain

an

opt

imal

am

ount

of s

urfa

ce a

rea,

the

curr

ent p

roje

ct in

volv

es

crea

ting

a m

atrix

thro

ugh

the

mix

ing

of h

eat t

reat

ed Sr

Oan

d de

com

posit

ion

of sa

crifi

cial

car

bon.

The

tem

pera

ture

s at w

hich

th

e Sr

Ois

bein

g he

at tr

eate

d va

ried

alon

g w

ith th

e siz

e of

the

part

icle

s bei

ng u

sed;

also

the

ratio

and

size

of t

he c

arbo

n pa

rtic

les

are

bein

g va

ried

to fi

nd th

e op

timal

stru

ctur

e w

ith th

e m

ost

surf

ace

area

.

SrCO

3 ↔ S

rO+

CO2(

g)

Re

vers

ible

N

o ca

taly

sis

High

tem

pera

ture

(~12

00°C

)Sa

fe

Joan

na Ju

lien,

Jere

my

Grun

ewal

d, K

elvi

n Ra

ndhi

r, N

atha

n Rh

odes

, Con

rad

Cole

, Nic

k Au

Yeun

g, L

ike

Li, R

enw

ei M

ei, D

avid

Hah

n

Ackn

owle

dgem

ents

We

are

very

app

reci

ativ

e of

fund

ing

from

Hid

en A

naly

tical

for p

artic

ipat

ion

in th

is po

ster

se

ssio

n.

This

wor

k w

as fu

nded

by

the

U.S.

Dep

artm

ent o

f Ene

rgy

Suns

hot I

nitia

tive

as p

art o

f the

EL

EMEN

TS p

rogr

am, a

war

d DE

-EE0

0065

34.

Futu

re W

ork

Para

met

erLe

vel

Sele

cted

Valu

es

AHe

attr

eatm

ent t

empe

ratu

re(T

H)-

1235

°C+

1400

°C

BSr

O p

artic

lesiz

e(S

) -

25 µ

m -3

8 µm

+10

6 µm

-125

µm

CGr

aphi

tepa

rtic

lesiz

e (S

g)-

25 µ

m -3

8 µm

+10

6 µm

–12

5 µm

DM

assr

atio

ofgr

aphi

teto

SrO

(r)

-0.

2+

0.7

ESt

ruct

ure

form

atio

nte

mpe

ratu

re(T

s)-

1100

°C+

1300

°C

Prel

imin

ary

data

show

ing

dyna

mic

cycl

ing

betw

een

1100

and

13

00°C

at 1

0°C/

min

. pC

O2

= 0.

33 b

ar

Ar

Heat

Ex

chan

ger

Mas

s Flo

w

Met

er Mas

s Flo

w C

ontr

olle

rs

High

Te

mpe

ratu

re

Furn

ace

He

CO2

Bed

Pres

sure

tran

sduc

er

Hide

n HP

R-20

MS

BPR

Inve

stig

atio

n in

to c

arbo

natio

n at

ele

vate

d pr

essu

re

*SEM

imag

e of

por

ous S

rO/S

rCO

3 sa

mpl

e 8.

Obj

ectiv

e:To

find

the

varia

ble/

s tha

t mos

t affe

cts t

he

ener

gy d

ensit

y. It

is h

ypot

hesiz

ed th

at a

n op

timize

d am

ount

of

surf

ace

area

will

max

imize

the

ener

gy d

ensit

y.

0

500

1000

1500

2000

2500

3000

3500

4000

01

23

45

Energy Density, [MJ/m3]

Cyc

le

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15-1

15-2

16 25-3

8 H

T po

wde

r

106-

125

pow

der

20%

Pol

ymor

phic

Ener

gy D

ensi

ty o

f Sam

ples

Z-va

lue

of th

e Pa

ram

eter

s

*A b

asel

ine

of 9

5 pe

rcen

t.

Corr

elat

ion

of re

sults

: Len

th’s

Met

hod

Proc

edur

e:1.

A m

atrix

was

cre

ated

2. H

eat t

reat

the

SrO

3. C

rush

and

siev

e th

e m

ater

ials

to th

e ap

prop

riate

size

s

4. M

ix th

e Sr

Oan

d gr

aphi

teto

the

appr

opria

te ra

tios

5. E

valu

ate

the

reac

tivity

of t

he sa

mpl

es u

sing

a th

erm

o gr

avim

etric

ana

lyze

r (TG

A)

Conc

lusi

on:

With

5 c

ycle

s don

e w

ith th

e TG

A, th

e as

sum

ptio

n is

that

the

ener

gy

dens

ity w

ill b

e st

able

with

con

tinue

d cy

cles

for e

ach

sam

ple.

The

sam

ple

that

show

ed th

e m

ost p

rom

ise w

as sa

mpl

e 15

in te

rms o

fen

ergy

de

nsity

. The

ene

rgy

dens

ity o

f 15

star

ted

off a

roun

d 35

00 M

J/m

^3 in

the

first

cyc

le a

nd ta

pere

d of

f to

just

abo

ve 1

500

MJ/

m^3

, abo

ut 7

% h

ighe

r th

an th

e ba

se p

owde

r. W

hen

com

parin

g th

e ef

fect

s of t

he p

aram

eter

s al

one

and

toge

ther

, the

dat

a sh

ows t

hat b

oth

the

size

of th

e Sr

Opa

rtic

les

and

the

grap

hite

par

ticle

s cre

ate

a la

rge

effe

ct o

n th

e en

ergy

den

sity.

Su

rfac

e ar

ea a

ppea

rs to

hav

e an

affe

ct o

n en

ergy

den

sity.

The

nex

t qu

estio

n sh

ould

be

wha

t sta

biliz

es th

e en

ergy

den

sity

?

So

lar

The

rmo

che

mic

al En

erg

y S

tora

ge