The technical performance of commercially available thermal energy storage (TES) residential heating units under severe weather conditions is discussed. The benefits and costs of TES to the user and utility companies were assessed. The TES issues, research and development needs, and barriers to commercialization were identified. The field tests which determined the performance characteristics for the TES are described and the TES systems, which included both ceramic and hydronic systems, are compared

Asbury, J. G.

Hersh, H. N.

English

NASA Technical Reports Server

EXPERIMENTAL EVALUATION OF THERMAL ENERGY STORAGE 
J. G. Asbury and H. N. Hersh 
Argonne National Laboratory 
PROJECT OUTLINE 
Project Ti t le :  Demonstrati on of Storage Heater Systems for  Resi denti a1 
Appl i cati  ons 
Principal Investigator: J. Asbury 
Organizati on: Argonne National Laboratory 
9700 South Cass Avenue 
Argonne, IL 60439 
Telephone: (312) 972-3779 
Project Goals: Demonstrate the thermal performance, u t i l i t y  impact, and 
customer acceptance of resi  dent i a1 TES systems usi ng 
off-peak e lec t r ic i ty .  Identify and define after-the-meter 
TES R&D needs. 
Two separate demonstrations are included. The University 
of Vermont and Central Vermont Public Service Company are 
coll ect i  ng and analyzing data over two heating seasons for  
17 ceramic TES systems, 6 hydronic TES systems, and 19 
control systems. The University of Maine and Central Maine 
Power Company are collecting and analyzing data from 10 
ceramic TES systems and 8 control systems. 
Project Status: Data were coJ7ected from the f i r s t  winter season. A survey 
of customer at t i tudes was completed. 
Contract Number: ANL 189 #49897 
Contract Period: FY 79 continuing 
Funding Level : $590,000 
Funding Source: U.S. Department of Energy 
Divisi on of Energy Storage Systems 
https://ntrs.nasa.gov/search.jsp?R=19800014329 2020-03-21T18:14:18+00:00Z
PROJECT SUMMARY 
P r o j e c t  T i t l e :  - Experimental Evaluat ion of Thermal Energy Storage 
P r i n c i p a l  I n v e s t i g a t o r s :  J.G. Asbury and H.N.  Hersh 
Organization: Spec ia l  P r o j e c t s  Group, Energy and Environmental Systems Divis ion  
Argonne National  Laboratory 
Argonne, IL 60439 
Pro j e c t  Goals : 
Experimentally v a l i d a t e  t h e  t e c h n i c a l  performance of commercially 
a v a i l a b l e  TES r e s i d e n t i a l  hea t ing  u n i t s  under severe  U.S. weather 
condi t ions .  
Assess t h e  b e n e f i t s  and c o s t s  of TES t o  t h e  customer, t h e  u t i l i t y  
and s o c i e t y .  
Determine use r  acceptance of TES. 
I d e n t i f y  and d e f i n e  TES i s s u e s ,  R&D needs and b a r r i e r s  t o  commerciali- 
za t ion .  
E s t a b l i s h  uniform TES t e s t i n g  s t anda rds .  
P r o j e c t  S t a t u s :  
I n s t a l l a t i o n s  have been completed i n  45 t e s t  and 30 c o n t r o l  s i t e s  
and da t a  c o l l e c t e d ;  based on r e s u l t s  f o r  one hea t ing  season, and 
comparison wi th  e l e c t r i c  baseboard systems, t h e  t echn ica l  performance 
of TES ceramic and hydronic systems i s  good. 
A pre l iminary  assessment of t h e  b e n e f i t s  and c o s t s  of customer-owned 
TES f o r  r e s i d e n t i a l  and commercial a p p l i c a t i o n s  i n d i c a t e s  t h a t  t h e  
n e t  r e t u r n s  t o  s o c i e t y  of such investments  exceed t h e i r  c o s t s  by a 
s u b s t a n t i a l  margin. 
a A u s e r  survey by an  independent o rgan iza t ion  i n d i c a t e s  a high degree 
of customer acceptance.  
I s s u e s  of proper  r a t e  des ign  and c o r r e c t  s i z i n g  of TES capac i ty  by 
vendors and c o n t r a c t o r s  have emerged and a r e  c u r r e n t l y  being examined. 
A ca lo r ime te r  chamber has  been b u i l t  and s tandard ized  procedures f o r  
t e s t i n g  TES modular u n i t s  a r e  being developed as an a i d  t o  commercial- 
i z a t  ion .  
Contract  Period - FY80 
Contract  Funding - S150K 
EXPERIMENTAL EVALUATION OF THERMAL ENERGY STORAGE: AN INTERIM REPORT 
H.N. Elersh 
Argonne, IL 60439 
1. BACKGROUND 
Early r e s u l t s  from t h e  ANL assessment of energy s t o r a g e  technologies  
i nd ica t ed  t h a t  customer-owned TES u n i t s '  of t h e  type  used in Europe could 
provide a  c o s t - e f f e c t i v e  means f o r  u t i l i t y  load  management i n  t h e  U.S. (1) .  
It was necessary,  t h e r e f o r e ,  t h a t  t h e  t echn ica l  and economic v i a b i l i t y  of 
t h i s  technology be examined under U.S. condi t ions .  These cond i t i ons  now 
inc lude  a changing r egu la to ry  atmosphere encouraging r a t e  reform and, of 
course,  c l i m a t i c  cond i t i ons  more extreme than i n  Europe. The reg ion  s e l e c t e d  
f o r  t h i s  f i e l d  s tudy  was New England, w i th  i ts  s t r o n g  dependence on o i l  and 
s c a r c i t y  of n a t u r a l  gas.  E l e c t r i c  baseboard hea t ing  i s  a  major hea t ing  a l -  
t e r n a t i v e  i n  t h i s  a r e a .  In  Vermont, u t i l i t i e s  had a l r eady  begun t o  i n v e s t i -  
g a t e  thermal energy s t o r a g e  and off-peak r a t e s  as one form of load management 
and had i n s t i t u t e d  programs t o  reduce loads  by d i r e c t  u t i l i t y  c o n t r o l  of s t o r -  
age hot  water hea t e r s .  
2.  SCOPE AND OBJECTIVES 
We r e p o r t  he re  some r e s u l t s  of t h e  f i r s t  y e a r ' s  t e s t s  involv ing  a  co l -  
l a b o r a t i v e  e f f o r t  among ANL, Purdue Univers i ty ,  t h e  U n i v e r s i t i e s  of Maine and 
of Vermont, and s e v e r a l  l o c a l  coopera t ing  e l e c t r i c  u t i l i t y  companies (Cent ra l  
Maine Power Co., Cen t r a l  Vermont Publ ic  Serv ice  Co., Green Mountain Power Co. 
and Vermont E l e c t r i c  Cooperat ive) .  
The p r i n c i p a l  o b j e c t i v e s  of t h e  study a r e  t o :  
Va l ida t e  t h e  t e c h n i c a l  performance of commercially a v a i l -  
a b l e  TES u n i t s  under s eve re  U.S. weather cond i t i ons .  
Assess t h e  b e n e f i t s  and c o s t s  of TES. 
Determine p o t e n t i a l  customer and u t i l i t y  acceptance  of 
customer-owned TES . 
a I d e n t i f y  and d e f i n e  TES i s s u e s ,  RLD needs and b a r r i e r s  t o  
commercialization. 
a E s t a b l i s h  uniform TES t e s t i n g  s tandards .  
The method adopted f o r  achiev ing  each o b j e c t i v e  i s  descr ibed  below. 
309 
3. FINDINGS 
Since work is  s t i l l  i n  progress  t h e  f i n d i n g s  r epo r t ed  h e r e  must be 
regarded as t e n t a t i v e .  
3.1 Technical Performance 
F ie ld  t e s t s  i n  Vermont and Maine a r e  being c a r r i e d  ou t  t o  eva lua t e  t h e  
performance of TES systems. TES systems a r e  ope ra t ing  i n  45 t e s t  homes, and 
monitor ing equipment r eco rds  t h e  e l e c t r i c  hea t ing  demand and t h e  i n s i d e  and 
o u t s i d e  temperatures  every 15  minutes i n  t h e s e  t e s t  homes and i n  30 c o n t r o l  
homes. A l l  of t h e  p a r t i c i p a t i n g  homes have been energy-audited by an e l e c t r i c  
u t i l i t y .  Most of t h e  TES u n i t s  i n  t h e  t e s t  homes a r e  room-type ceramic s t o r a g e  
h e a t e r s ,  bu t  s i x  hydronic s t o r a g e  h e a t e r s  and one c e n t r a l  ceramic s t o r a g e  fu r -  
nace a r e  a l s o  being t e s t e d .  The c o n t r o l  s i t e s  a r e  heated wi th  convent ional  
r e s i s t a n c e  baseboard u n i t s .  A l l  u n i t s  were s i z e d  by t h e  vendor t o  meet t h e  
f u l l  design-day hea t ing  load and were commercially i n s t a l l e d .  
During the  f i r s t  hea t ing  season, d a t a  were c o l l e c t e d  from 34 t e s t  and 
26 c o n t r o l  s i t e s ,  w i th  some l o s s  of d a t a  and u n c e r t a i n t i e s  due t o  malfunct ions 
i n  monitoring equipment and problems i n  magnetic t a p e  handl ing.  Funct ional  
performance of t h e  TES systems has gene ra l ly  been good, and i t  has been con- 
cluded t h a t  TES u n i t s ,  i f  p roper ly  s i zed  f o r  t h e  home, perform wel l .  This  
pre l iminary  conclusion a p p l i e s  equa l ly  t o  d i spe r sed  and c e n t r a l  ceramic u n i t s  
and t o  hydronic c e n t r a l  u n i t s .  
The major c r i t e r i o n  f o r  t h i s  assessment was t h e  maintenance of e s s e n t i a l l y  
i d e n t i c a l  i n s i d e  temperatures  i n  thermally matched t e s t  and c o n t r o l  homes 
throughout t h e  hea t ing  season,  e.g. ,  on t y p i c a l  win t ry  January days, on 
October days (which have more v o l a t i l e  temperature f l u c t u a t i o n s ) ,  and on 
t h e  c o l d e s t  day of t h e  year .  I n  Vermont t h e  lowest  temperature recorded 
a t  t h e  sites w a s  - 2 8 ' ~  on February 12,  1979; i n  Maine 70 degree-days were 
accumulated on February 14 ,  providing o p p o r t u n i t i e s  t o  observe heating-system 
performance under "design" cond i t i ons  and t o  eva lua t e  shortcomings i n  s i z i n g  
formulas. Graphical r eco rds  of d a i l y  e l e c t r i c a l  demand and i n s i d e  temperatures  
of test homes c l e a r l y  d i s t i n g u i s h  adequately s i z e d  s t o r a g e  h e a t i n g  systems 
t h a t  u se  only off-peak e l e c t r i c i t y  from those  that a d d i t i o n a l l y  r e q u i r e  t h e  
u s e  of e l e c t r i c i t y  generated dur ing  high-use times. 
3.2 Socia l  Bene f i t s  and Costs  
S tud ie s  of t h e  economics of TES i n  Maine and Vermont us ing  a s o c i a l  
we l f a re  approach i n d i c a t e  t h a t  t h e r e  a r e  n e t  s o c i a l  b e n e f i t s  and t h a t  
b e n e f i t s  can accrue  t o  both use r  and u t i l i t y  (2 ,3) .  This  conclusion i s  
based upon a comparison of t h e  est imated c o s t s  and consequent savings.  
Fac tors  taken i n t o  account  inc lude :  
(1) a d d i t i o n a l  customer c o s t s ,  compared t o  d i r e c t  baseboard 
systems, of i n s t a l l e d  TES systems (room u n i t s  and 
c e n t r a l  fu rnaces )  i n  homes having a wide range of hea t  
l o s s ;  
(2) u t i l i t y  c o s t s  of s p e c i a l  c o n t r o l s ,  meters  and t ransformers ;  
(3) u t i l i t y  r e t u r n s  due t o  est imated f u t u r e  sav ings  i n  foregone 
gene ra t ion ,  t ransmiss ion  and d i s t r i b u t i o n  needs (discounted 
t o  p re sen t  va lue .  
In  Vermont, bene f i t - cos t  r a t i o s  a r e  est imated t o  be g r e a t e r  than 3 . 4  f o r  room 
u n i t s  and g r e a t e r  than 5.6 f o r  c e n t r a l  u n i t s  (3) .  The higher  r a t i o  f o r  
c e n t r a l  u n i t s  i s  due t o  t h e i r  lower c a p i t a l  c o s t  per  k i lowa t t  of hea t  l o s s .  
I n  Maine, t h e  t o t a l  sav ings  a r e  est imated t o  be about $344 per k i lowat t  
of hea t  l o s s ,  and t h e  a d d i t i o n a l  c a p i t a l  c o s t  wi th  r e spec t  t o  e l e c t r i c  base- 
board h e a t e r s  is  about $225 per k i lowa t t  of hea t  l o s s .  (The c o s t  of e l e c t r i c  
baseboard h e a t e r s  is about $150/kW.) 
3 . 3  P o t e n t i a l  - -.- Customer .~ - - and U t i l i t y  Acceptance 
A survey of u s e r s  by an  independent r e sea rch  o rgan iza t ion  revea led  
equal  s a t i s f a c t i o n  w i t h  s t o r a g e  h e a t e r s  and w i t h  i n s t a n t  h e a t e r s  (baseboard) .  
The survey was based on 156 households,  of which 1 3 1  a r e  heated v i a  thermal 
s t o r a g e  and 25  by d i r e c t  e l e c t r i c  h e a t i n g  (4) .  Over 95% of t h e  owners of 
homes wi th  TES u n i t s  would recommend TES t o  a f r i e n d  ( t h e  same a s  f o r  u s e r s  
of baseboard h e a t e r s ) .  The improvements most f r equen t ly  suggested were 
decreas ing  t h e  phys i ca l  s i z e  of t h e  room u n i t s  and improving t h e i r  appearance. 
Many u t i l i t i e s  t h a t  have had exposure t o ,  o r  i n t e r e s t  in ,  TES a s  a  load 
management t o o l  f e e l  i t  can have a p o s i t i v e  impact. However, public  concern 
about the  environmental degradation due t o  t h e  use  of nuc lea r  and coal  base- 
load f u e l s  negat ive ly  a f f e c t s  u t i l i t y  planning and i n i t i a t i v e ,  c rea t ing  
uncer t a in t i e s  i n  t h e  s i z e  and s t a b i l i t y  of the  cos t  d i f f e r e n t i a l  of baseload 
and non-baseload e l e c t r i c i t y .  
3.4 I ssues  
Many i s sues  must be i d e n t i f i e d  and resolved before  the re  can be any 
extensive adoption of TES. Among them a r e  c a p i t a l  c o s t  of TES equipment, 
co r rec t  s i z i n g  of the  TES systems and proper r a t e  s t r u c t u r e .  
E l e c t r i c i t y  P r i c i n g  - The problem of inc reas ing  the  use of 
TES i s  that of t r a n s f e r r i n g  some of the  a n t i c i p a t e d  u t i l i t y  
savings t o  t h e  customer so t h a t  TES w i l l  be an a t t r a c t i v e  
investment. The problem is  complex. A t  t h i s  time, based 
on an on-going comparative analys is ,  a  load management 
agreement between customer and u t i l i t y  seems b e t t e r  than 
e i t h e r  a  time-of-use r a t e  format o r  a  time-of-use p lus  
demand-charge r a t e .  Load management agreements insure  
more con t ro l  of u t i l i t y  capacity growth and l e s s  customer 
r i s k  of r a t e  i n s t a b i l i t y .  
How Much Storage? - The adoption of TES w i l l  be very 
s e n s i t i v e  t o  c a l c u l a t i n g  and i n s t a l l i n g  the  proper 
amount of s to rage  heat ing capacity.  Prel iminary energy- 
use s t u d i e s  of TES i n  Maine i n d i c a t e  t h a t  t h e  s i z i n g  
method f o r  an 8-hour charge period i s  marginal f o r  ex- 
treme weather condit ions.  Simulation s t u d i e s  have under- 
scored t h e  p o t e n t i a l  problem of developing a shoulder 
peak of demand of supplemental heat  whish is  required toward 
the  end of t h e  on-peak period. The problem of supplying 
a bui ld ing wi th  optimal thermal s to rage  capaci ty  is  one 
of s k i r t i n g  t h e  Charybdis of inadequate s to rage  capaci ty  
(which may n e i t h e r  cu t  o i l  demand nor s u f f i c i e n t l y  de- 
crease  t h e  need f o r  investments i n  new genera t ing  capaci ty)  
and t h e  Scy l l a  of t oo  much i n s t a l l e d  s t o r a g e  capac i ty  (which 
may be so expensive t h a t  t h e  customer w i l l  n o t  buy t h e  TES 
system). This  s i z i n g  problem has  s e v e r a l  i n t e r r e l a t e d  
elements : 
(1)  t h e  i n c e n t i v e  of t h e  vendor t o  make a s a l e  by 
lowering t h e  c a p i t a l  c o s t  (i.e., recommending 
smal le r  capac i ty  than may be  r equ i r ed ) ,  
(2)  t h e  goal  of t h e  customer o r  real e s t a t e  developer  
who wants TES but  wants t o  minimize i n i t i a l  c o s t  
( thereby  impacting t h e  u t i l i t y  on i ts  peak demand 
days) ,  
(2; d i f f e r e n t  s i z i n g  methods used by d i f f e r e n t  vendors,  
and 
(4)  t h e  i n t r i n s i c  unce r t a in ty  i n  t he  hea t ing  capac i ty  
margin requi red  by d i f f e r e n t  u s e r s  and types  of 
use. 
C a p i t a l  - - . - - . Costs - of - TES - - -  and Control Equipment - Sens ib le  hea t  
s to rage  devices  and c o n t r o l  u n i t s  a r e  e s s e n t i a l l y  simple 
products .  Xeducing the  c a p i t a l  c o s t s  of TES systems by 
cheaper manufacturing methods and more vendor competi t ion 
can amel iora te ,  t o  some e x t e n t ,  some of t h e  above problems 
and provide customer incen t ive  t o  buy TES equipment. 
3.5 T e s t i n g  
TES u n i t s  of d i f f e r e n t  manufacture can have d i f f e r e n t  c h a r a c t e r i s t i c s  
and s to rage  c a p a c i t i e s .  Depending on d e t a i l s  of des ign ,  u n i t s  having the  same 
nominal r a t i n g  and t o t a l  s t o r a g e  capac i ty  may have d i f f e r e n t  r a t e s  of spon- 
taneous r a d i a t i v e  emission, r a t e s  of forced d ischarge ,  hot  a i r  temperatures ,  
s t o r a g e  medium temperatures ,  e t c .  Since t h e  u n i t s  a r e  modular, i t  w i l l  be 
poss ib l e  t o  measure and compare t h e i r  thermal performance by appropr i a t e  
c a l o r i m e t r i c  techniques.  Simple e l e c t r i c - i n p u t  thermal-output r a t i n g s  can 
then be used by customers i n  making buying dec i s ions  and t o t a l  performance 
c h a r a c t e r i s t i c s  can be used by a r c h i t e c t s  and o t h e r s  f o r  heating-system 
design;  such a v a i l a b l e  informat ion  should a c c e l e r a t e  t h e  rate of commerciali- 
za t ion .  For this reason,developing and promulgating s tandard  c a l o r i m e t r i c  
procedures  t h a t  can b e  dup l i ca t ed  i n  o t h e r  l a b o r a t o r i e s  i s  a component of 
t h e  ANL program. A t  Purdue Univers i ty  a ca lo r ime te r  has been b u i l t  fol lowing 
31 3 
t h e  German s tandard  as descr ibed  i n  D I N  44572. I n i t i a l  a t t e m p t s  t o  c a l i b r a t e  
and use  t h i s  ca lo r ime te r  i nd i ca t ed  t h e  n e c e s s i t y  f o r  a redes ign .  Severa l  
des ign  mod i f i ca t i ons  were made and i n v e s t i g a t e d  exper imenta l ly .  The p re sen t  
des ign  has  g r e a t l y  improved uni formi ty  i n  t h e  c ros s - sec t iona l  temperature  
d i s t r i b u t i o n  of t h e  o u t l e t  duc t  where t h e  temperature  of  t h e  e x i t i n g a i r  is 
measured. A 2-klJ roon-size TES u n i t  is  soon t o  be i n s t a l l e d  i n  t h e  c a l o r i -  
meter chamber f o r  t e s t i n g .  A t  t h e  same time a 30-kW c e n t r a l  u n i t  is being 
read ied  f o r  i r ~ s t a l l a t i o n  and i n i t i a l  c a l o r i m e t r i c  measurements i n  a l a r g e ,  
environmental ly  c o n t r o l l e d  room. 
4 .  COMMENTS 
The f i n d i n g s  so  f a r  support  t h e  expec ta t ion  of e a r l i e r  s t u d i e s :  
TES i s  t e c h n i c a l l y  and economically v i a b l e  i n  winter-peaking e l e c t r i c  
s e r v i c e  a r e a s  of t h e  U.S. t h a t  r e l y  on e l e c t r i c i t y  f o r  space hea t ing ,  
where t h e  u n d e r u t i l i z e d  baseload energy i s  suppl ied  by c o a l  o r  o t h e r  
cheaper baseload f u e l s .  It i s  probably no t  too  e a r l y  f o r  i n d u s t r y  and 
t h e  government t o  s t a r t  t hose  s t u d i e s  and a c t i v i t i e s  necessary  t o  
a c c e l e r a t e  t h e  i n t r o d u c t i o n  of sens ib le -hea t  thermal  energy s t o r a g e  where 
i t  i s  deemed p o s s i b l e  and d e s i r a b l e .  While f u r t h e r  s t u d i e s  a r e  necessary  
f o r  s o l i d  documentation, t h e r e  is  p r e s e n t l y  a need f o r  TES handbooks, 
seminary f o r  p o t e n t i a l  s u p p l i e r s ,  i n s t a l l e r s  and c o n t r a c t o r s ,  and t h e  d i s -  
seminat ion of t e c h n i c a l  and f i n a n c i a l  information t o  pub l i c  u t i l i t i e s ,  
r egu la to ry  commissions, consumer groups, f i n a n c i a l  i n s t i t u t i o n s ,  e t c .  
REFERENCES 
1. Asbury, J . G . ,  e t  a l . ,  "Assessment of Energy Storage Technologies and 
Systemst', ANL/ES-54 (August 1976). 
2. Mirchandani, G . ,  et  a l . ,  "Investments i n  Storage ~ e a t i n g " ,  UVM/EE-3 
(May 1979). 
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Experimental evaluation of thermal energy storage

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