Thermal Energy Storage Experiments Leaflet

0830-C

Thermal Energy Storage Experiments

COMPLEX AUTONOMOUS PAYLOAD

STS-69 ENDEAVOR CAPL-2/GVA 1995

Thermal energy storage (TES) payload.

iDEPOStTORY UMR\M\

I Sponsored By Office of Space Access and Technology National Aeronautics and Space Administration Lewis Research Center Space Flight Systems Directorate Space Experiments Division

the salt is melted, it expands approximately 30 percent in v o l u m e . The stored thermal

INTRODUCTION

energy is released w h e n the salt shrinks or freezes during the shade p o r t i o n of the orbit. The repeated melting and freezing of the salt creates voids in the salt during

The Thermal Energy Storage (TES) experiments are designed to provide data for understanding the long-duration microgravity behavior of thermal energy storage fluoride

salts that u n d e r g o

melting and freezing.

repeated

solidification. V o i d f o r m a t i o n w i t h i n the salt impacts the heat transfer rate to the salt and the design of the heat receiver containers holding the TES salt.

Consequently,

understanding and predicting the melt-and-freeze behavior of the c o n t a i n e d TES fluoride salt in the on-orbit microgravity e n v i r o n m e n t is essential for achieving an i m p r o v e d design for heat receivers of solar dynamic p o w e r systems.

Such data have

never been o b t a i n e d before and have direct application to using on-orbit solar dynamic p o w e r systems.

These p o w e r

systems will store solar energy in a thermal energy salt such as lithium fluoride calcium difluoride (LiF-CaF ). The energy is stored

Dr. David Jacqmin of the NASA Lewis Research Center has d e v e l o p e d and is refining a c o m p u t e r c o d e TESSIM (Thermal Energy Storage Simulation). TESSIM can predict the behavior and migration of voids in the receiver canisters. It is currently useful as a qualitative design t o o l but requires further experimental validation. O n c e t h o r o u g h l y validated, the c o d e will be invaluable in the detailed design of lighter, m o r e efficient solar dynamic receivers.

2

as the latent heat of fusion w h e n the salt is m e l t e d by a b s o r b i n g solar

thermal

energy. The stored energy is extracted during the shade p o r t i o n of the orbit. This enables the solar dynamic p o w e r system to provide constant electrical p o w e r over

The first Thermal Energy Storage experiment (TES-1) was successfully f l o w n o n STS62 in M a r c h 1994. The results of TES-1 test data are preliminary but agree in general w i t h the TESSIM predictions. The TES-1 canister was examined nondestructively by using a technique called "tomography/'computer-assisted radiographic images. Images of the phase change material inside the annular v o l u m e w e r e d e v e l o p e d . The images s h o w e d that melting and freezing of the phase change material (PCM) caused

the entire orbit.

significant shifting of the mass during a cycle. In general, TESSIM appears to have The principal investigator of the TES experiments was Carol Tolbert of the Power Technology

D i v i s i o n at N A S A

Lewis

Research Center, Cleveland, O h i o . Project management

for the e x p e r i m e n t was

p e r f o r m e d by Frank Robinson, Jr. of the Space Experiments Division. Task w o r k was a c c o m p l i s h e d by an in-house dedi-

predicted v o i d behavior accurately as is evidenced by c o m p a r i n g the t o m o g r a p h i c images w i t h the TESSIM images. These initial results from TES-1 of high-temperature TES melting and freezing under microgravity do not absolutely validate TESSIM, but the c o m p a r i s o n of the predictions w i t h data establishes a basic confidence in the c o d e . Future experiments such as TES-2, 3 and 4 will contribute to further validation of TESSIM.

PROJECT OBJECTIVE

cated project team consisting of NASA Lewis and N Y M A Technology, Inc., engineers and technicians. The project was supported by the NASA

Headquarters

Office of Space Access and Technology.

BACKGROUND

The objective of this flight project w o r k is to develop and flight-test long-duration microgravity experiments for obtaining data that characterize the v o i d behavior in TES fluoride salts. This project is the first in w h i c h TES materials will be subjected to an extended microgravity duration w h i l e changing phase.

EXPERIMENTAL APPROACH The first t w o separate flight experiments, TES-1 and TES-2, have been d e v e l o p e d to

Future space application of an advanced

obtain data on salt behavior in cylindrical canisters.

p o w e r system in sun-shade operating con-

successfully f l o w n as part of the O A S T - 2 Hitchhiker payload on the Columbia

ditions requires the system to have high

STS-62 in early 1994. Experiment TES-2 will be part of the C A P L - 2 / G V A payload o n

efficiency, reliability, l o w specific weight,

the Endeavor Shuttle STS-69 mission in July 1995. The TES-1 and TES-2 experiments

and l o w life-cycle cost. A d v a n c e d tech-

are identical except for the fluoride salts to be characterized. Both experiments use

nology w o r k is helping to establish a solar

a sealed cylindrical Haynes-188 canister to hold the salts. The first experiment, TES-

The TES-1 e x p e r i m e n t was Shuttle

d y n a m i c p o w e r system for use in Earth-

1, p r o v i d e d data on lithium fluoride (LiF) w h i c h melts at 1121 K.

o r b i t i n g spacecraft. This system continu-

experiment, TES-2, will provide data o n a fluoride eutectic (LiF/CaF ) w h i c h melts at

The second

2

ously provides electrical p o w e r by col-

1042 K. Each experiment is a c o m p l e x a u t o n o m o u s payload in a Get-Away-Special

lecting and storing solar thermal energy

(GAS) payload canister. Hence, no p o w e r is required from the shuttle. Flight data are

that is later c o n v e r t e d to electrical p o w e r

stored in the r a n d o m access m e m o r y of each payload. A postflight CAT scan of each

w h i l e in the Earth's shadow. The collected

TES salt container will provide data on v o i d sizes and distribution. Later, t w o additional

solar thermal energy is stored in a heat

experiments, TES-3 and TES-4, will be developed for obtaining data on salt behavior

receiver that consists of many canisters.

in wedge-shaped canisters.

Each canister holds a fluoride salt (LiFCaF ) w h i c h is melted by absorbing the 2

solar thermal energy f r o m the Sun. W h e n

FLIGHT HARDWARE

MLI a n d M L I shutter. The primary c o m ponents of the canister assembly are

PROGRAM HIGHLIGHTS

the Haynes-188 canister and the therThe TES-2 experiment is m o u n t e d along

mal radiator disc. Each canister has an

• First long-term (10 hr) microgravity

w i t h other experiments o n a gas bridge

annular cross section created by a solid

thermal energy storage experiments

w h i c h is placed w i t h i n the payload bay of

c o n d u c t o r rod along the axis of each

p e r f o r m e d in space.

the shuttle.

canister.

Each TES experiment occu-

3

The annular cylindrical vol• First high-temperature (1042 K) ex-

pies 5 f t and weighs a b o u t 245 lb prior to

ume contains the TES salt. The canisters

placement in the GAS payload container.

are w e l d e d closed in a v a c u u m after the

periments that cyclically melt and

salt is loaded into the canister.

freeze Li-based salts.

Each experiment payload consists of the same three hardware subsystems (fig.1).

The middle section is o c c u p i e d by the

The t o p section or the experiment section

data acquisition and c o n t r o l

(fig. 2) is made up of a cylindrical canister

(DACS). Also, i n d e p e n d e n t high-tem-

assembly, a t w o - z o n e radiant heater, high-

perature control units are located in the

system

• Software

control

logic and

data

acquisition designed for operational contingencies to help assure mission success. • Autonomous

o p e r a t i o n of experi-

temperature multilayer insulation (MLI),

middle section.

and an MLI shutter and drive mechanism

control for maintaining a safe m a x i m u m

ments achieved by self-contained bat-

as well as temperature measurement in-

temperature level associated w i t h these

tery cells.

strumentation. Temperature is measured

1200-K temperature level experiments.

They provide added

at many different locations w i t h swaged 20-mil, type K t h e r m o c o u p l e s . The entire

Finally, the b o t t o m section consists of a

canister assembly is enclosed w i t h i n the

battery box that contains 23 silver-zinc

POINTS OF CONTACT Principal Investigator Carol M.

Tolbert

NASA Lewis Research Center Power T e c h n o l o g y Division Cleveland, O H 4 4 1 3 5 (216) 4 3 3 - 6 1 6 7 Flight Project Manager Frank Robinson,

jr.

NASA Lewis Research Center Space Experiments Division Cleveland, O H 4 4 1 3 5 (216) 4 3 3 - 2 3 4 0 Program Manager Richard

Gualdoni

NASA Headquarters Office of Space Access and T e c h n o l o g y Washington, DC

20546

(202)358-4669 CAPL-2/GVA Mission Manager Christopher

Dunker

G o d d a r d Space Flight Center Greenbelt, M D 2 0 7 7 1 (301) 2 8 6 - 4 2 7 1

Figure l.—TES payload.

MLI andMLI shutter. The primary c o m -

cells w h i c h provide all the electrical en-

ponents of the canister assembly are

ergy required for the t w o - z o n e radiant

the Haynes-188 canister and the ther-

heater and the DACS. Each cell contains

mal radiator disc. Each canister has an

a potassium hydroxide electrolyte.

The

annular cross section created by a solid

initial electrical energy level p r o v i d e d by

conductor rod along the axis of each

the battery box for each payload prior to

canister.

The annular cylindrical vol-

placement in the shuttle is a b o u t 6 3 0 0

ume contains the TES salt. The canisters

W h , w h i c h accounts for any battery deg-

are w e l d e d closed in a v a c u u m after the

radation over time. The energy expected

salt is loaded into the canister.

to be used on-orbit by each experiment is about 3400 W h .

The middle section is o c c u p i e d by the data acquisition and control

system

Thermal energy needed to melt the TES

(DACS). Also, independent high-tem-

salt in each canister is p r o v i d e d by a t w o -

perature control units are located in the

z o n e radiant heater. The cylindrical heater

middle section.

They provide added

COMPLEX AUTONOMOUS PAYLOAD

material consists of b o r o n nitride w i t h a

control for maintaining a safe m a x i m u m

graphite c o n d u c t i v e path. T w o

temperature level associated w i t h these

heater zones create a temperature differ-

1200-K temperature level experiments.

ence in the salt w h i c h causes v o i d move-

radiant

m e n t in the TES salt. The v o i d m o v e m e n t Finally, the b o t t o m section consists of a

is f r o m its initial location t o w a r d the high-

battery box that contains 23 silver-zinc

temperature z o n e of the heater.

STS-69 ENDEAVOR CAPL-2/GVA 1995

FLIGHT HARDWARE

MLI a n d M L I shutter. The primary c o m -

cells w h i c h provide all the electrical en-

ponents of the canister assembly are

ergy required for the t w o - z o n e radiant

the Haynes-188 canister and the ther-

heater and the DACS. Each cell contains

The TES-2 experiment is m o u n t e d along

mal radiator disc. Each canister has an

a potassium hydroxide electrolyte.

with other experiments on a gas bridge

annular cross section created by a solid

initial electrical energy level p r o v i d e d by

which is placed w i t h i n the payload bay of

c o n d u c t o r rod along the axis of each

the battery box for each payload prior to

the shuttle.

canister.

The

The annular cylindrical vol-

placement in the shuttle is a b o u t 6 3 0 0

pies 5 f t and weighs a b o u t 245 lb prior to

ume contains theTES salt. The canisters

W h , w h i c h accounts for any battery deg-

placement in the GAS payload container.

are w e l d e d closed in a v a c u u m after the

radation over time. The energy e x p e c t e d

salt is loaded into the canister.

to be used on-orbit by each e x p e r i m e n t is

Each TES experiment occu-

3

about 3400 W h .

Each experiment payload consists of the same three hardware subsystems (fig.1).

The middle section is o c c u p i e d by the

The t o p section or the experiment section

data acquisition and c o n t r o l

(fig. 2) is made up of a cylindrical canister

(DACS). Also, independent high-tem-

salt in each canister is p r o v i d e d by a t w o -

assembly, a t w o - z o n e radiant heater, high-

perature control units are located in the

z o n e radiant heater. The cylindrical heater

temperature multilayer insulation (MLI),

middle section.

material consists of b o r o n nitride w i t h a

and an MLI shutter and drive mechanism

control for maintaining a safe m a x i m u m

graphite c o n d u c t i v e path. T w o

as well as temperature measurement in-

temperature level associated w i t h these

heater zones create a t e m p e r a t u r e differ-

strumentation. Temperature is measured

1200-K temperature level experiments.

ence in the salt w h i c h causes v o i d m o v e -

system

They provide added

Thermal energy needed to melt the TES

radiant

m e n t in the TES salt. The v o i d m o v e m e n t

at many different locations w i t h swaged 20-mil, type K t h e r m o c o u p l e s . The entire

Finally, the b o t t o m section consists of a

is f r o m its initial location t o w a r d the high-

canister assembly is enclosed w i t h i n the

battery box that contains 23 silver-zinc

temperature z o n e of the heater.

— Experiment section

Data acquisition and control system (DACS)

Battery box

Payload Battery vent

vent

Figure h—TES payload.

I

MLI andMLI shutter. The primary c o m -

cells w h i c h provide all the electrical en-

ponents of the canister assembly are

ergy required for the t w o - z o n e radiant

the Haynes-188 canister and the ther-

heater and the DACS. Each cell contains

mal radiator disc. Each canister has an

a potassium hydroxide electrolyte.

annular cross section created by a solid

initial electrical energy level p r o v i d e d by

conductor rod along the axis of each

the battery box for each payload prior to

canister.

The

The annular cylindrical vol-

placement in the shuttle is a b o u t 6 3 0 0

ume contains the TES salt. The canisters

W h , w h i c h accounts for any battery deg-

are w e l d e d closed in a v a c u u m after the

radation over time. The energy expected

salt is loaded into the canister.

to be used on-orbit by each experiment is about 3400 W h .

The middle section is o c c u p i e d by the data acquisition and control

system

Thermal energy needed to melt the TES

(DACS). Also, independent high-tem-

salt in each canister is p r o v i d e d by a t w o -

perature control units are located in the

z o n e radiant heater. The cylindrical heater

middle section.

They provide added

COMPLEX AUTONOMOUS PAYLOAD

material consists of b o r o n nitride w i t h a

control for maintaining a safe m a x i m u m

graphite c o n d u c t i v e path. T w o

temperature level associated w i t h these

heater zones create a temperature differ-

1200-K temperature level experiments.

ence in the salt w h i c h causes v o i d move-

radiant

ment in the TES salt. The v o i d m o v e m e n t Finally, the b o t t o m section consists of a

is f r o m its initial location t o w a r d the high-

battery box that contains 23 silver-zinc

temperature z o n e of the heater.

-—Experiment section

- Battery box

- Payload vent

Figure l.—TES payload.

STS-69 ENDEAVOR CAPL-2/GVA 1995

Heater p o w e r levels and MLI shutter opening and closing are controlled by the Conductor rod^

DACS located in the m i d d l e section of the payload. The DACS not only controls the thermal cycling of the experiment, but also periodically records the instrumentation o u t p u t signals. A n 80386SX central processing unit is used in the DACS to

TES material

Danister

provide the needed data collection speed and processing.

OPERATION SEQUENCE

Conductor rod

The TES experiments are activated by an astronaut w h o begins a 5-hr heatup phase Radiator

for each experiment. A v a c u u m environm e n t exists in the GAS payload contain-

MLI shutter door (one of two) V

ers. After the heatup phase to a TES salt

Canister

N

melt is c o m p l e t e d , the on-orbit melt-andfreeze thermal cycles begin.

A total of

four thermal cycles over a 10-hr period are planned for characterizing the behav3

ior of theTES salts in a 1 0 " - g e n v i r o n m e n t . O n e thermal cycle consists of a melt phase and a freeze phase each of w h i c h

MLI

Heater -

takes a b o u t 60 m i n . The freeze or solidification phase of a thermal cycle is initiated w h e n

heater

p o w e r is turned off and the MLI shutter is opened.

Thermal energy

Support-

dissipation

n e e d e d to cause the salt to freeze is achieved by c o n d u c t i n g the thermal en-

Figure 2—TES experiment section.

ergy o u t of the salt into the solid rod in the center of the canister, and f r o m the rod to the thermal radiator disc. The disc radi-

Flight data are recorded at 5-min intervals and primarily consist of the time variation

ates the stored thermal energy (latent

of temperatures and heater p o w e r during the heatup, melt-and-freeze, and c o o l - d o w n

heat of fusion for the salt) to the GAS

phases of the experiment. O t h e r data include the time elapsed from the startup of

payload container upper end-plate. This

the experiment, time of each data sample, p o w e r level, and estimated electrical

plate in turn radiates the thermal energy

energy remaining in the battery cells. After the thermal cycles are c o m p l e t e d and the

o u t to space. A t the end of the freeze

experiment section cools d o w n to approximately 750 K, the experiments are de-

phase, the MLI shutter is then closed and

activated by an astronaut. A t this point, a vent valve in each of the GAS payload

the next melt cycle begins.

containers is closed to seal off the GAS containers prior to a shuttle de-orbit.

B-0686-A April 95