Economic possibilities of the heat pump

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Economic possibilities of the heat pump

Wirth, P. E.

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NATIONAL RESEARCH COUNCIL O F CANADA

TRAIJSLATIGN TT

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97

Tm

ECONOivTIC POSSIBILITIES OF THZ HEAT

PUIJiP

( ~ i e W i r t s c h a f t l i c h & n m g l i c h k e i t e n d e r WCirmepumpe) t r a n s l a t e d by D,A, S i n c l a i r T h i s i s t h e Eigllth o f t h e S e r i e s o f T r a n s l a t i o n s Prepared f o r t h e D i v i s i o n o f B u i l d i n g iiesearch. Ottawa 8 December 1949,

The N a t i o n a l Research Council t h r o u g h i t s D i v i s i o n o f B u i l d i n g Research h a s i n s t a l l e d a n e x p e r i m e n t a l h e a t pump on t h e grounds o f i t s i d o r t r e a l Road L a b o r a t o r i e s w i t h which it i s hoped t o i n v e s t i g a t e some o f t h e many problems connected w i t n h e a t pump o p e r a t i o n ,

Trle e x t e n s i v e l i t e r a t u r e i n c o n n e c t i o n w i t h h e a t pumps h a s been c a r e f u l l y s t u d i e s i n c o n n e c t i o n w i t h t h i s i n s t a l l a t i o n , T h i s t r a n s l a t i o n o f a Swiss a r t i c l e a p p e a r s t o be o f s p e c i a l v a l u e s i n c e it i s t h e econo~nic a s p e c t s o f n e a t pu1.1~ o p e r a t i o n which a r e s o q u e s t i o n a b l e i n E a s t e r n Canada. The Swiss have been p i o n e e r s i n c o n n e c t i o n ~ 4 t h h e a t pump work and it i s f h e r e f o r e a p l e a s u r e t o have t h i s t r a n s l a t i o n published i n c o n n e c t i o n w i t h Canadian work,

Robert F. Legget, D i r e c t o r ,

Page

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1

TT-97

THE

ECONOMIC POSSIBILITIES OF THE HEAT PUMP

The problem of using electricity economically in connection with the heat pump for domestic heating purposes is very much to the fore in this country, It has been dealt

with frequently in this publication ( e o g o , M o Egli, Die

Waermepumpenheizung des zflrcherischen Rathauses

-

The heat

pump of the Zurich City Hall: 1938, no, 21, p , 262; M, Egli,

Einiges ueber die Moeglichkeiten von Waermepumpenheizungen

-

Notes on the possibilities of heat pump heating systems: 1939,

no, 2, p, 42;

P o

Seehaus, Winterheizung durch Sommerenergie

-

Winter heating from summer energy: 1940, no, 15, p, 317;

A,

Spoerli, Speiclierung von Sommerueberschuasenergie fuer den

Waermebedarf im Winter

-

The storage of excess summer energy

for winter heating: 1940, no, 24, p, 564;'Ao Gasser, Weiterer

Vorschlag fuer Winterheizung durch Sornrnerwaerme

-

Another

suggestion for winter heating by means of summer heat: 1941,

noo 6, p o 9 3 ; O 0 Hasler, Die wirtschaftlichen Grundlagen der

Waermepumpenanlagen im neuen HaPlensehwiwnbad Zibich

-

The

economic principles of the heat pump plant in the new Zurich

indoor swimming pool: 1941, no, 15, p, 345)0 P o E , Wirth has

discussed the question of heat pumps generally in the Schwefz.

Bauzeftung of 7 June 1941, In the following the same author

gives a brief resume of his argument

I),

It is assumed that

professional circles dealing with these problems wi 11 be

interested

Although owing to the current fuel shortages the heat pump is once more very much in the foreground, little has been said thus far concerning its economic aspects. It

is not easy to make an accurate survey of these since the various costs are fluctuating eontfnuously, and long-term forecasts about their development are difficulto With a view to directing the utilization of aleetrfcal power, which is

not available in unlimited quantities, into the right channels, it may be usefil to review all the important applications of the heat pump.

The manner of presentation here employed permits '

suitable assumptions to be made on whieh judgments in the individual cases may be based, These assumptions are con- cerned particularly with the price movements of coal and

electricity and they provide a dependable bas1 s for estimating

both capital and operating costso

By itself the term "heat pump" suggests that heat is not manufactured, but is pumped up from a temperature,level

The diagrams are reprinted by permission of the Schweiz, Bauzeitung,

Page

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2

TT-97

which permits of no practical utilization to one at which heat may once more be derived. The power consumption of the heat pump increases with the temperature above which the heat must be pumped. The so-called "output coefficient" forms part of the operating cost, It tells how much more heat, in the given application, is converted into useful form, compared with the direct conversion of electrical eneagy into heat, The output coefficient expresses both the level of temperature which

must be overcome and the efficiency of the process and machine. Since the cost of installing a heat pump is quite high, its time of operation also plays a considerable part. From this point of view, particularly, the room heating

applications are not very favourable. Figure 1 shows the

load diagram of a room heating plant relative to continuous operations of a more industrial character, Room heating is distinctly a peak operation, in which the load peaks often coincide with periods of power shortage due to recession of water levels. It is a clear inference that the highest load peak should not be charged to the expensive heat pump, but should be singled out and taken care of by means of fuel

heating, as indicated in Figure 1, Year-round industrial

operation may be o n either a daytime or twenty-four-hour basis. In the latter case, in contrast to room heating, the lightly shaded area would be extended, owing to the gkeater number of operating hours, and the contrast would be even more marked,

The most important fields of application will now be described briefly in the order of increasing output

coefficients

A

-

Aesatfon and Drying

This refers to processes in which the air circulates. The earliest form of refrigerator, the cold air machine, is again being considered in this connection owing to its sim- plicity (the heat carrier is identified with the circulating air). it was formerly abandoned because of its high power consumptfon, but this has since been improved<, The output coefficients and specific costs quoted in Table I are still in a stage of development.

The ssme applications are also possible with the cold-steam machine. These were alread a subject of inves-

8

1

tigation in the war period, 1314

-

18 =

B

and C

-

Room Heating with Normal and Low Water Temperatures.

In this application the set-up of the familiar refrigerator, i.e., the so-called cold-steam machine, is

employed, T h i s h a s a s p e c i a l h e a t c a r r i e r , and u s , s o u t s i d e h e a t tc! f e e d t h e e v a p o r a t o r , The o p e r a t i n g c o s t , t h e r e f o r e , i n c 1 u d : j s a p o r t i o n f o r w a t e r s u p p l y , and t h i s must n o t be n e g l e ~ t e d i n a n y w ' d e r e x t e n s i o n o f t h e h e a t pump f o r room h e a t i n g p u r p o s e s

3 3 .

The s p e c i f i c c o s t s a r e f o r a p l a n t o f s e v e r a l h u n d r e d s of t h o u s a n d k c a l . p e r h r . h e a t o u t p u t i n t h e c o n d e n s e r , and r e l a t e t o a machine d e s i g n which i s now f u l l y d e v e l o p e d .

The i d e a o f room h e a t i n g w i t h a h e a t pump i s n o t new. I t

wz7

s t u d i e d i n S w i t z e r l a n d e v e n b e f o r e t h e war of 1914

-

18

.

T a b l e I shows c l e a r l y how t h e o u t p u t c o e f f i c i e n t c a n be i n f l u e n c e d by t h e c h o i c e o f normal o r low t e m p e r a t u r e s . Low w a t e r t e m p e r a t u r e s r e q u i r e e i t h e r warm w a t e r h e a t i n g d e v i c e s w i t h v e r y l a r g e h e a t i n g e l e m e n t s , o r e l s e s p e c i a l h e a t i n g o f c e i l i n g s , e t c . I n calculating t h e o p e r a t i n g h o u r s , t h e c u t t i n g ' o f f of t h e h e a t i n g p e a k , a s i n F i g u r e 1, h a s a l r e a d y been t a k e n i n t o a c c o u n t .

D

-

H e a t i n g o f Water f o r Swimming P o o l s , I n d u s t r i a l Uses, E t c . I n t h i s a p p l i c a t i o n , t o o , t h e o r d i n a r y c o l d - s t e a m machi ne i s employed. Along w i t h t h e m a n u f a c t u r i n g c o s t s o f t h e h e a t pump i t s e l f , t h e o u t l a y s f o r c o l l e c t i o n and s t o r a g e o f warm d r a i n a g e w a t e r and h e a t e d f r e s h w a t e r have a n i m p o r t a n t i n f l u e n c e . I n t h i s c a s e t h e h e a t pump i s a s t e a m c o m p r e s s o r . T h i s a p p l i c a t i o n , e s p e c i a l l y was t h e o b j e c t o f i n t e n s i v e s t u d y d u r i n g t h e 1914

-

18 p e r i o d

6 ) .

The f i g u r e s i n T a b l e I were compiled a c c o r d i n g t o t h e above c o n s i d e r a t i o n s .

The d i a g r a m s a r e b a s e d o n t h e a s s u m p t i o n t h a t a l t h o u g h t h e r e i s i n d e e d a f u e l s h o r t a g e , h e a t pumps a r e n o t b e i n g

i n s t a l l e d m e r e l y a s a r e s p o n s e t o t h e c u r r e n t demand f o r h e a t i n g a t a n y p r i c e . E x p e n s i v e p l a n t s a r e i n v o l v e d which

3 , Grossmann, Schwei z, Bauzef t u n g , 1 9 4 0 , no. 1 4 , p . 954.

4 , See Swiss P a t e n t no. 5 9 , 350, 1 9 1 2 ,

Page

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4 TT--97 must c o n t i n u e t o f u n c t i o n e e o n o m f c a l l y even i n t h e f a c e o f an e v e n t u a l d r o p i n t h e p r i c e of c o a l . Should t h e l a t t e r con- d i t i o n n o t be f u l f i l l e d i t i s probable t h a t i n d u s t r i a l h e a t i n g p l a n t , i n p a r t i c u l a r , w i l l be d i s c a r d e d when s u c h a drop o c c u r s . I t w i l l be a more t h a n welcome development i f t h e money which i s now g o i n g abroad f o r e x p e n s i v e f u e l i m p o r t s can be a p p l i e d t o t h e e x p l o i t a t i o n of n a t i v e h y d r o - e l e c t r i o r e s o u r c e s ; how- e v e r , a c o n v e r s i o n o f t h i s k i n d w i l l a l s o havc t c be economical o v e r a l o n g p e r i o d . The Swiss e l e c t r i (el pro3 l e e r s , e s p e c i a l l y t h o s e w i t h r e c e n t l y b u i l t p l a n t s , woula g a ~ i n o t h l n g i f t h e y should r e t a i n t h e s e customers o n l y a s l o n g a s t h e h i g h c o a l p r i c e s l a s t and be f o r c e d t o w i t n e s s t h e r e t u r n t o t h e con- sumption of f u e l t h e r e a f t e r , w i t h t h e r e l e v a n t sums of money g o i n g abroad a g a i n ,

I n t h e diagrams t h e working c o s t s p e r m i l l i o n k c a l . c o n v e r t e d a r e p l o t t e d a g a i n s t f u e l p r i c e s and .compared w i t h

working c o s t s f o r h e a t pump o p e r a t i o o ,

Coke was assumed t o y i e l d a u s e f u l h e a t o f 5000 k c a l . p e r k g o Values which can o n l y be a t t a i n e d i n a modern and

w e l l a t t e n d e d b o i l e r p l a n t were p u r p o s e l y c h o s e n , S i n c e t h e a p p l i c a t i o n s i n which e l e c t r i c i t y can compete u s u a l l y form o n l y a f r a c t i o n of t h e t o t a l h e a t f n g economy, i t i s f i r s t of a l l e s s e n t i a l t o have t h e main h e a t i n g economy on a r a t i o n a l basf s

The power r a t e s used a r e 3 and 5 r p . t , p e r kwh., i U e , ~ a t e s which i n t h e a u t h o r i s o p i n i o n come w i t h i n t h e r a n g e of h e a p e r motor c u r r e n t r a t e s .

Under a p p l i c a t i o n s A , D and E t h e f a c t t h a t t h e o r i g i n a l h e a t i n p u t can be u t i l i z e d more t h a n once by s u i t - a b l e c o n d u c t i o n of t h e h e a t l n g p r o c e s s e s j whether by means o f hea r e c o v e r y d e v i c - s i n t h e c a s e of A o r D , o r by m u l t i p l e e v a p o r a t . r s ( m u l t i element d e v i c e s ) , i n t h e c a s e of E , h a s been t a k e n i n t o a c c o u q t ,

The main iagram ( F i g . 2 ) , r e l a t e s t o t h e c o s t of o p e r a t i o n w i t h o u t a t t e n d a n c e , b u t i n c l u d i n g m a i n t e n a n c e , which must be borne even i f f o r any r e a s o n t h e i n s t a l l a t i o n c o s t s c a n be w r i t t e n o f f i m m e d i a t e l y o The a d d i t i o n a l s c a l e t o t h e r i g h t of t h e main diagram e n a b l e s t h e i n t e r e s t y i e l d and a m o r t i z a t i o n of t h e p l a n t c a p i t a l t o be r e a d d i r e c t l y i n p e r c e n t . A p p l i c a t i o n s B ( F i g o 2 ) and C ( F i g , 3 ) a r e p l a c e d f i r s t b e c a u s e t h e y r e l a t e t o room h e a t i n g , of which t h e t y p i c a l

Page

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5 TT-97 l o a d p i c t u r e h a s a l r e a d y b e e n i l l u s b r a t e d i n F i g u r e 1. These a r e p l a n t s w i t h r e l a t i v e l y b r i e f o v e r a l l o p e r a t i n g p e r i o d s , i n which t h e r e a r e d i s t i n c t l o a d p e a k s ; power c o n s u m p t i o n o c c u r s m a i n l y i n w i n t e r * I t i s a l o g i c a l outcome of t h e d e s i r e i n v a r i o u s q u a r t e r s t o e x t e n d t h e u s e o f e l e c t r i c a l room h e a t i n g , t h a t t h e problem o f s t o r i n g summer h e a t f o r u s e

i n w i n t e r s h o u l d be i n v e s t i g a t e d p a r t l y i n c o n n e c t i o n w i t h t h e h e a t pump. The h i g h c o s t o f i n s t a l l i n g s u c h d e v i c e s d o e s n o t y e t a p p e a r t o have been e x p l a i n e d f u l l y . A p p l i c a t i o n s A,

D

and E r e l a t e m a i n l y o y e a r - r o u n d 6! i n d u s t r i a l p r o c e s s e s , e x c e p t f o r p u r e a e r a t i o n The r e l a t i v e l y h i g h m a n u f a c t u r i n g c o s t s and t h e s h o r t o p e r a t i n g p e r i o d s a l r e a d y l e a d t o a h i g h m a i n t e n a n c e q u o t a f o r

"B"

p l a n t s ( F i g . 2 ) o I n a d d i t i o n t h e r e a r e t h e c o s t s o f s u p p l y i n g w a t e r t o t h e e v a p o r a t o r , These two components b r i n g t h e h e a t i n g c o s t t o a f i g u r e c o r r e s p o n d l i l ~ r o u g h l y t o

50 f r o p e r t o n o f c o k e , The e l e c t r i c a : ( h y d r u ) power com- p o n e n t i s a l s o r e l a t i v e l y h i g h b e c a u s e o f t h e Low o u t p u t c o e f f i c i e n t , s o t h a t a t 5 r p . p e r kwh. up t o a p p r o x i m a t e l y 1 6 0 f r , p e r t o n of c o k e , and a t 3 r p . p e r kwh. u p t o a p p r o x - i m a t e l y 125 f r , p e r t o n of c o k e , n e i t h e r a n i n t e r e s t y i e l d n o r a m o r t i z a t i o n o f c a p i t a l i s p o s s i b l e . I f f u e l p r i c e s f a l l below t h e s e l i m i t s t h e power r a t e u s e d i n t h e a c c o u n t i n g c a n no l o n g e r be p a i d , A t 5 C f r , p e r t o n o f coke o n l y m a i n t e n a n c e and w a t e r s u p p l y a r e c o v e r e d . F i g u r e 3 , room h e a t i n g w i t h low w a t e r t e m p e r a t u r e s a s i n a p p l i c a t i o r l I=, i s somewhat more f a v o u r a b l e , s i n c e t h e h y d r o - e l e c t r i c c o s t , owing t o t h e h i g h e r o u t p u t c o e f f i c i e n t , r e p r e s e n t s a s m a l l e r s h a r e o f t h e t o t a l o Hence, w i t h p r e s e n t - d a y coke p r i c e s , a n i n t e r e s t y i e l d c n p l a n t c a p i t a l , b u t no a m o r t i z a t i o n , i s p o s s i b l e . S i n c e t h e s p e c i f i c i n s t a l l a t i o n c o s t and o u t p u t c o e f f i c i e n t s o f a p l a n t f o r d r y i n g by method A ( F i g , 4 ) , a r e s i m i l a r t o t h o s e o f

B

i t i s u n n e c e s s a r y t o d i s c u s s t h e a e r a t i o n f i e l d o f a p p l i c a t i o n a n y f u r t h e r . Of g r e a t e r i n t e r e s t i s t h e a p p l i c a t i o n t o i n d u s t r i a l d r y i n g , where i t s h o u l d be n o t e d t h a t i n modern p l a n t s f r e s h h e a t c a n be c o n v e r t e d w i t h a u t i l i z a t i o n f a c t o r o f P 0 4 , Owing t o t h e g r e a t e r number o f o p e r a t f n g h o u r s t h e m a i n t e n a n c e q u o t a d r o p s s h a r p l y " The c o s t o f h e a t p r o d u c t i o n i s n i l , so t h a t a t p r e s e n t - d a y c o a l p r i c e s a n i n t e r e s t y i e l d F ' u r t h e r d e t a i l s c a n be f o u n d i n t h e o r i g i n a l p a p e r , S O B O Z O v, 117 (19421, n o , 2 3 , p o p o 265 f f . - --.*.*

Page

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6 TT.--97

and a s m a l l a m o r t i z a t i o n a p p e a r p o s s i b l e . I t s h o u l d be n o t e d , however, t h a t a t c o a l p r i c e s f r o m 1 2 5 f r . t o 75 f r o p e r t o n , and downwards t h e assumed power r a t e s c a n no l o n g e r be p a i d ,

For warm w a t e r h e a t i n g a s i n D ( F i g o 5 ) t h e l o w e r s p e c i f i c i n s t a l l a t i o n c o s t s , and t h e h i g h e r o u t p u t c o e f f i c i e n t p r e s e n t a much more f a v o u r a b l e p i c t u r e A ~ p r e c F a b l e amor- t i z a t i o n q u o t a s a p p e a r even f o r t h e ccaP p r i c e s o f t h e s p r i n g of 1 9 4 % . For pre-war p r i c e s , 1939, t h e assumed power r a t e s

c a n a l s o be p a i d ,

F i g u r e 6, e v a p o r a t i o n a s u n d e r E , i s s t i l l more f a v o u r a b l e , The s p e c i f i c i n s t a l l a t i o n c o s t s a r e t h e l o w e s t o f a l l , and t h e e l e c t r i c a l power u t i l i z a t i o n i s h i g h e s t , Even i n comparison w i t h a modern m u l t i - e l e m e n t e v a p o r a t i o n p l a n t t h e p o s s i b i l i t y o f a r a p i d r e t i r e m e n t o f t h e i n s t a l l a -

t i o n c o s t s r e m a i n s . Coal p r i c e s may r e c e d e t o w e l l below t h e 1939 l e v e l b e f o r e a power r a t e o f 3 r p , p e r kwh. c a n no l o n g e r be p a i d , T h i s i s p r o b a b l y due t o t h e f a c t t h a t t h e p l a n t s a r e l a r g e and o p e r a t e a l l y e a r r o u n d o

To sum u p , i t may be s a i d t h a t f o r c a t e g o r i e s A t o C , a t p r e s e n t c o a l p r i c e s , n o t much more c a n be a c h i e v e d t k a n t h e payment o f a r e a s o n a b l e motor power r a t e . For D and 2

t h e i n s t a l l a t i o n c o s t s , a s w e l l , may be w r i t t e n o f f a g a i n s t t h e prevailing h i g h p r i c e s o f c o a l . Under c a t e g o r y E s p e c i f i c i n s t a l l a t i o n c o s t s a r e 14 f r , p e r 106 k c a l . , compared w i t h 220 f r o p e r

l o 6

k c a l o i n c a s e s B and C o For e q u a l I n s t a l l a t i o n c o s t s a b o u t f i f t e e n t i m e s a s much h e a t c a n be c o n v e r t e d b y method E a s by B o r C . E f s a l s o much more a d v a n t a g e o u s w i t h r e s p e c t t o e l e c t r i c a l power consumption, s i n c e w i t h t h e same amount o f e l e c t r i c i t y a l m o s t f i v e t i m e s a s much h e a t c a n b e corlverted a s w i t h B .

These c o n c l u s i o n s emphasize t h e i m p o r t a n c e o f t h e problem s t a t e d i n t h e e d i t o r i a l I n t r o d u c t i o n , namely t h a t o f u t i l i z i n g e l e c t r i c i t y f o r t h e c o u n t r y Y s h e a t i n g n e e d s econ- o m i c a l l y w l t h t h e a i d o f t h e h e a t pump. The v a r i o u s p o s s i b -

i l i t i e s must be examined i n d e t a i l so t h a t b o t h c a p i t a l and e l e c t r i c a l power, n e i t h e r o f which i s i n e x h a u s t i b l e , may be e c o n o m i c a l l y e x p l o i t e d , i . e , m a y be d i r e c t e d i n t o c h a n n e l s where t h e y c a n b e s t be u t i l i z e d .

Page

-

7

TT-97

TABLE I

SUMMARY OF MOST IMPORTANT

FACTORS INFLUENC

ING

CAPITAL AND OPERATING COSTS

Heat Pump

Application

-

A

-

Aeration and

B

-

Room heating

(with normal

water temp-

C

-

Room heating

D

-

Warm water for

industrial

water), swfm-

and Lyes, salt

extraction,

F'u'el

Operating

time per

year

hr.

1500 and up

Main-

tenance

Output

Coefficient

1

Installa-

tion costs

per kcal.

per hr.

Condenser

output

fr.per kwh.

quota

k

F i g . 1, 2. TT-97 No. o r o p o r a t l n e d a y s I n t h e ysmr

a

y a a r s s o p e r a t l o n n S h a r s o f room h e a t l n e by n l e c t r l c l t y ( h y d r o - e l e c t . r l c powerl S h a r e o r room h e a t l n g by f u e l ( c o a l ) F i g . 1: Load diagram

h e 1 p r l c e s I n f r . ner t o n o r coke fsn ) b e 1 p r l c o s I n Vr. p e r t o n o f coke

F11. 2 r Fig. 2 b. F x p e n d l t u r e I n b?'r.ncs nmlntenanca

=

w a t e r aupplg f o r e v a p o r a t o r p e r m l l l l o n k c a l . c o n v e r t e d 0 e l e c t r i c a l FOWer e a p l t a l e a r n l n g s ( a u x l l l a r y s c a l e I n :) r n n g e o r h e 1 p r l c e s b e f o r e o u t h r e a A o r war. 1939

i

i n C r s n c s p e r t o n r i n g s o r r u e 1 p r l c s a I n 1 9 4 1 F i g . 2: Room h e a t i n g a t normal w a t e r t e m p e r a t u r e s a s i n a p p l i c a t i o n B. 1550 f u l l o p e r a t i n g h o u r s p e r y e a r . ( a ) pcwer r a t e 3 rp./kwh. ( b ) power r a t e 5 rp./kwh.

Fig. 3

-

6. TT-97

Em h e 1 p r i e e r Ln Tr. p e r ton o f coke

0 50 IW 1 9 ma

&el p r l c e a I n rr. p e r ton o r e m 1

~ h . 3 : Room heating at low Fig. 4: Drying, as in app-

water temperatures lication

A.

as in application C.

1550 full operating

hours per,year. Power

rates, 3 and

5

rpe/

kwh.

For legend see

Fig.2.

sm Fuel a r l c s s In f r . p e r t o n .'f c o a l

Fig. 5: Water heating as in

application

D.

3000 full operating

hours per year. Power

rates, 3 and 5 rp./

kwh.

7200 full operating

hours per year. Power

rates, 3 and 5 rp./ kwh. rn P l e l p r l c e s I n Tr. p e r t o n o f coml Fig. 6: Evaporation as in application

D.

7200 full operating

hours per year. Power

rates, 3 and 5 rp./