NRCC passive solar test facility performance of direct-gain units

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NRCC passive solar test facility performance of direct-gain units

Ser

m

392 LSSA 0701-5232

NRCC PASSIVE SOLAR TEST FACILITY

PERFORMANCE

OF

S.A. Barakat

D i v i s i o n of B u i l d i n g Research, National Research CouncFl of Canada

NATIONAL RESEARCH COUNCIL CANADA D I V I S I O N OF

BUILDING RESEARCH

NRCC PASSIVE

SOLAR TEST

S . A . Barakat:

Ottawa May 1984

NRCC PASSIVE SOLAR TEST FACILITY PERFORMANCE OF DIRECT-GAIN UNITS

SUMMARY

Experimental data collected for t w o heating s e a s o n s at the p a s s i v e

s o l a r t e s t f a c i l i t y o f the D t v i s i o n o f Building Research are presented f o r

three two-zone and four single-zone direct-gafn u n i t s . The e f f e c t s of solar gaFn, thermal storage mass and b u i l d t n g thermal load o n t h e utilization of solar galns to satisfy the space heating requirement are examined. The use o f t h e experimental d a t a f o r verifying energy-related c a l c u l a t i o n s

for

In

normally found i n a woo&£ rame house) produces only

a

in

1.

The passive solar t e s t

f a c i l i t y

direct

u n i t s ( U n i t s 1 to 31, each consisting of a s o u ~ h and a n o r t h room

( e . g . , room IS and

1N

I ) ,

(R1 t o R4). The construction d e t a i l s o f

all

Reference 1 also describes the data acquisition s y s t e m , presents the methad used to a n a l y s e the data to o b t a i n varTous performance factors a n d discusses

t h e uncertainties associa~ed with these f a c t o r s .

The b a s i c d i f f e r e n c e h e t w e e n t h e two-reorn u n i t s is their i n t e r n a l

storage mass, as given in Table 1. The four s l n g l r r o o m units each have the

same mass h u t each has a window f a c i n g one of the four cardinal d i r e c t i o n s . Each of t h e two-zone units w a s operated in two modes a l t e r n a t e l y for

t w w w e e k p e r i o d s . 51 Mode 1 , the unit is monf rored as t w o _{separate rooms}

while

t w o r o a m , using a small f a n above t h e door. Data gathered between

October land A p r i l 30 in 1980/81

and

described in Reference

1

3.

s i n g l e room UnZts R I to

R4

e l i m i n a t e d f o r any i n t e r v a l i f t h e y are i n c o m p l e t e due to equipment f a i l u r e .

The data in Tables 2 and 3 are examined in t h e fallowkng s e c t i o n s to assess t h e effects of various f a c t o r s on t h e performance of d i r e c ~ g a i n p a s s i v e

solar systems. The data are also used t o check energy calculation methods

f o r d i r e c t - g a i n p a s s i v e s o l a r houses.

2. PERFORMANCE FACTORS

The fallowing are the main factars used to describe the performance o f

the units. Details en these and other parameter c a l c a l a r i o n s a r e given in

Reference I. A l l factors are calculated over the heating season f o r each of the two modes o f o p e r a t i o n separately.

(1) Useful solar gain

This is the p o r t i o n of t h e s o l a r g a t n that contributes to the

reduction in t h e purchased heating requirement. Tt i n c l u d e s t h e solar g a i n u s e d t o o f Eset heat l o s s e s ,

plus

t h e

thermal

losses

a l a t e r

must

_be

room temperature from exceedtng

a

u t i l i z e d to o f f s e t additional losses caused by a rise in room

temperature above t h e thermostat s e t t i n g .

(2) Reference heat l o s s

This is the heat loss calculated at thermostat s e t t i n g (20°C).

( 3 ) Gain-load ratio

,

This i s t h e ratio of solar gain t o the net h e a t i n g load

( 4 ) Mass-gain r a t i o , MGR

T h i s is t h e ratio of the thermal capacity of the unit t o t h e

average hourly solar gain.

It

characterlstlics o f each u n l t . ( 5 ) Solar utilization f a c t o r , Q

T h i s is t h e f r a c t i o n of tf;e t o t a l s o l a r g a i n t h a t c o n t r i b u t e s to a reduction of the heating requirement.

It i s , therefore, t h e

( 6 ) Purchased heating Eraction, F h

This

-

Fs,

.

3. RESULTS

3.1 Effect of thermal s t o r a ~ e mass

Table 4 summarizes the performance of the south rooms of t h e t e s t units

(15,

the double-room u n i t s o p e r a t e d fn Mode 2, f o r both h e a r i n g seasons. The d a t a are a l s o presented in F i g u r e s I and 2 in terms of the solar utilization factor and t h e purchased heating f r a c t i o n as functions of mass-gain r a t i o

(MGR). Units

1,

2

heating load, as i n d i c a t e d by t h e value of t h e gafn-load r a t i o (GLR), For rhe same gain-load r a t i a , the s o l a r atlllzation factor (qs)

increases and t h e purchased h e a t i n g fraction

IF^)

mass (MGR). The increase in TI is, however, relatively small c o n s i d e r i n g t h e magnitude of the i n c r e a s e i n

rterraal

With an eight-fold increase in thermal mass, the s o l a r utilization f a c t o r increased from 0 . 5 6 to

0.89;

f r o m 0 . 6 6 to 0.47 under the best combination of conditions. T h f s amounts t o

a 29 % r e d u c t i o n compared with t h e light-mass u n l t .

The

25OC (No). While the light-mass units, operating in Mode 1, had

temperatures above

25OC

the heavy unit overheated (above 25°C) for l e s s than h a l f t h i s time in

1981/82 and almost never ( 0 . 2 % of the t %me)

in

3.2 E f f e c t of b u i l d i n g load

In comparing data for a given test unit over two heating seasons

{approximately the same MGR)

,

and 1981182 h e a t i n g seasons). T h i s difference in solar u t i l i z a t i o n is more

pronounced £ o r the u n i t s w i t h l o w thermal mass (low MGR). l k s p i t e the

r e d u c t i o n in solar u t i l i z a t l a n f a c t o r , t h e parchased heating f r a c t l o n also decreases because Lhe reduced useful solar gain satisfies a larger fraction o f the reduced h e a t i n g lead (i .e., higher solar heating f r a c t i o n ) . T h e

i s i n d i c a t e d by an increase I n the number of o v e r h e a t i n g hours i n 1981f82 f o r t h e heavy-mass unit i n Mode 1 and _{f o r a l l the units in Made 2 cornpared} t o the corresponding u n i t s in 1980/8l (when t h e i r GLR was lower).

3.3 Effect of Interzone A i r C i r c u l a t i o n

Air exchange with the north room p r o v i d e s t w o benefits: a larger heating l a a d Fs a v a i l a b l e t o u t i l i z e t h e solar gain ( l o w e r GLR); and more mass is a v a i l a b l e f o r storing the excess g a i n s (higher MGR). Bath effects

tend to increase solar utilization.

Table 5 gives t h e performance parameters

(ns,

overheating time (No) for U n i t s 1, 2 and 3 operating under both modes. The increase in

ns

t h e l i g h t e r units because t h e heavy unlts a l r e a d y have s i g n i f i c a n t thermal storage available in the south room. I n a l l units a i r circulation between rooms r e s u l t e d in a reduction in overhearing. For example, the percentage overheating t i m e decreased from 12% of t h e time to 4% f o r Unit 1 in

198018 1.

3 . 4

Effect

The effect of reduced s o l a r gain due to window o r i e n t a t i o n is shown in Table 6 , which compares data

for

thermal

the window orientation changes

from

south t o e a s t o r west increases the purchased heating by about 7 and 9%

respectively. T h i s effect is somewhat underestimated because af t h e l o w

performance of Unit

l

U

fi

small

will

purchased energy. This c o n f i r m s previous f i n d i n g s which showed that

4 0

degrees o f f south w o u l d r e s u l t i n less than

4%

3.5 Window Effectiveness

The net heat gain through a window, d e f i n e d a s s o l a r gain mlnus windaw reference lass*, is a measure of a window's p o t e n t i a l t o reduce the h e a t i n g requirement of a house. Over the heating season, south-oriented

d o u b l e g l a z e d windows p r o v i d e a n e t heat gain ta t h e apace if all t h e s o l a r

gain is used t o offset the heating requirement (1.e. q, = 1) ( 3 ) . For l a r g e

w i n d o w sizes, overheating nay occur and dumping of t h e excess solar g a i n

will reduce the n e t window contribution. Tn t h i s ; case a n e t e f f e c t i v e gain

can be d e f i n e d as the difference between t h e useful s o l a r galn and the

window reference loss. The net effective g a i n is a measure of the a c t u a l contribution of the window (or a passive system) t o t h e heating requirement of t h e space.

If

loss.

If

same heating requirement, t h e thermal resistance of such a wall is defined

as t h e equivalent wall r e s i s t a n c e (R ). e

Tables 7 and

8

e q u t v a l e n t wall r e s l s t a n c e f o r windows o f a l l d i r e c p g a i n units. For t h e

operating conditions studied

in

1

( 2 and 3) in Mode 2, the windows were net energy losers. For the 1980181 s e a s o n , a greater reduction

in

windows of U n i t s IS, R1, R 2 ,

R3

(RSI

3) would have heen outperEssmed by a w a l l s e c t i o n ( R S L 4.2). This is due to t h e lower utilization of solar energy as a result of increasing t h e GLR

(seducing r h e load).

VERIFICATION

CALCULATION

One of the majar o b j e c t i v e s of the test f a c t l i t y is t o check the energy

consumpti on p r e d i c t i o n s of computer programs or s i m p l i f i e d procedures which take i n t o account solar gain and thermal storage.

A simpliEied calculation method ( 4 , 5 ) is a v a i l a b l e to p r e d i c t t h e s o l a r

u t i l i z a t i o n f a c t o r and h e a t i n g energy requfrement 0 E houses.

In

method, values f o r

ns

s i m u l a t i o n and p r e s e n t e d as a f u n c t i o n of GLR and MGR f o r different:

allowable rises i n roam temperature.

Table 9 compares values of TI,, F h and energy consumption measured d u r i n g t h e 1980J8L season f o r d i r e c t - g a i n u n i t s with calculated v a l u e s at t h e same values of GLR and MGR. The agreement I s good, w i t h a maximum

difference between the calculated and measured purchased heating of less Ehan 5%.

Figures 3 to 5 p r e s e n t a preliminary comparison between experimental

horlrly values o f room a i r r e v e r a t a r e and energy consumption w i t h values

c a l c u l a t e d u s i n g t h e ENCORE-CANADA Program (65 €or the s o u t h room o f U n i t 1. T h e ptel%m.lnary r e s u l t s indicate very good agreement between measured and c a l c u l a t e d values.

D e t a i l e d comparisons f o r ether units will b e presented in a future

report. In addition, hourly d a t a f r o m r h e t e s t f a c i l i t y were supplied t o

t h e _{participating countrfes of the International Energy Agency T a s k V111,}

P a s s i v e and H y b r i d Lon Energy B u i l d i n g , t o be compared w i t h r e s u l t s produced

by several hourly computer simulation programs a s a p a r t of an Fnternarlonal

"validation" e f f o r t . Results oE t h i s work w i l l be p u b l f s h e d in an LEA report

.

5. _CONCLUSIONS

Performance d a t a f o r seven direct-gain t e s t u n i t s have been p r e s e n t e d f o r two h e a t i n g seasons. The f o l l o w i n g conclusions can be i n f e r r e d f ram

(1)

In

passive

thermal

main benefit of the increased thermal mass is a reduction in room overheating.

( 2 3

Air

leads

reduction in both purchased enerm and overheatbg.

(3) Reduction in solar g a i n due to o f f - s o o t h ( S E or

SW)

u t i l i z a t t o n .

is

window to be a net energy loser.

( 4 ) Unless a south windew is p r o p e r l y s i z e d to achieve maximum utilization

of solar gain, t h e w i n d o w h e a t l o s s may exceed t h e u s e f u l solar g a i n and the window may be a net energy loser. If large window areas rmrstl be used, the window should have a h i g h thermal resistance, and provision

s h o u l d also be made f o r interzone air c i r c u l a t i o n or extra mass in t h e

building to increase s o l a r

u

that obtained from t h e NRC p a s s i v e s o l a r t e s t f a c i l i t y , can be used

REFERENCES

1. Barakat, S.A* NRCC Passive Solar T e s t F a c i i t y : Description and D a t a

Reduction,

Building

1984.

2. BaZcamb, J.D., D. Barley, R. McFarLand, J . Perry

Jr., W.

S . N o l l . P a s s i v e Solar D e s i g n Handbook - V o l u m e 11, Passive S o l a r

Design A n a l y s i s , U . S . Department of Energy, DOEiCS -0127i2, Washington,

J a n u a r y 19 80.

3. Rarakat, S.A. Solar H e a t Gains Through Windows in Canada, DBR P a p e r No. 9 4 4 , NRCC 1 8 5 7 4 , Biv5sFon of B u i l d i n g Research, National Research

Council Canada, Ottawa, 1980.

4 . Barakat, S . A . , and B.M. Sander. A S i m p l e Method for k c e r m i n l n g t h e H e a t i n g Requirements of D i r e c t - G a i n P a s s i v e Solar H Q U S ~ S , Building

Research Note 195, Division of B u f l d i n g Research, National Research

Council Canada, Ot tawa, 1982.

5. Rarakat, S . A . , and D.M. Sander. Utilization of Solar Gains Through Windows f o r Heating Houses, Building Research N o t e 1 8 4 , D i v i s i o n of

Building Research, National Research Council Canada, Ottawa,

1982.

Study of Energy Consumption of R e s i d e n t i a l Buildings in Canada,

DBR

Table 1 T h e r m a l Storage Characteristics of Test U n i t s

South Ther ma1

Test window c a p a c i t y

u n i t area, m 2 (MJ/K) Construct i o n

1 2 . 6 1.53 L i g h t

-

12.7 m m gypsum board f i n i s h on w a l l s and

c e i l i n g s , c a r p e t over wooden floor. 4 -13 Medium

-

50.8

board f i n i s h on w a l l s and 25.4 mrn on

c e i l i n g

.

3 2 . 6 11.55 Heavy

-

b r i c k , 12.7 m m g y p s m board f i n i s h on

rOmt-- m m e m b a

. T q d q * ? m q m <

d o d o d o d o d o

Table 3 S e a s o n a l Performance of Direct-Gain Unf tls f o r 19 81/82

Av

T o t a l

Solar Useful Over-

o u t d o o r indoor l o s s e s H e a t i n g C o o l i n g gain solar heating

MGR

~ m / U n i t Bays

'I:

k~

kw

GLR

Mode 1 1s 80

ZN

68

2N

3

S

ELI

169

l2

96

l~outh

Table 4 Overall Performance of D i r e c t G a i n U n i t s

MGR

Mode

~ m / ~ n i t

weight1

P ~ / F ~ ( L )

No

1980/8

1981192 Heating season

light, M medium and H heavy.

%ata presented are for monitoring p e r i o d common to all u n i t s . 3 ~ o u b l ~ room unfts

.

Table 5 E f f e c t o f I n t e r z o n e A i r C i r c u l a t i o n

Rm/Unit Weight Mode GLR

"23 Fh No(% ) 198018 1 Heating season 0.31 0.77 0.29 0.9 2 0.33 10.85 0.31 0 . 9 4 0 -31 0.95 0.30 0,97 1981182 Weatlng season 0.44 U - 5 5 0.37 10.82 0 . 4 6 0.69 0 . 3 9 0.92 0.42 0.9 0.38 0.95 Table 6 E f f e c t of Window O r i e n t a t i o n Unit Orientation MGR GLR _{'ls Fh F ~ / F ~ ( I U}

₁

0.33

r

T a b l e 7 Window N e t E f f e c t i v e Gain for 1980/81 season l

Window loss

Solar

kW

R m l T J n i t s R e f . Actual kWah kW oh kW -h kW *h m

2 * ~ / W

I Window

U A

WIK,

*

Table

Window lass S o l a r Net U s e f u l N e t ef f

.

h / U n i t Ref. Actual

k W * h

Mode 1

1s

2

UA

8.9

W/K,

2 b n s i d e r i n g s o u t h window o n l y of each unit ( a l l N. window g a i n c o n s i d e r e d useful).

MGR. h l K F I G U R E 1 V A R I A T I O N

OF

30 w 25 W fE 3 20 Q Q= W a 5 W M E A S U R E D 2 1 . 0 ' ~ A V E R A G E + 15 --- P R E D I C T E D 2 1 . 1 3 c A V E R A G E 10 16 17 18 19 20 2 1 22 2 3 2 4 25 26 27 2 8 D A T E , D E C E M B E R 1980 F I G U R E 3 C O M P A R I S O N O F M E A S U R E D AND C A L C U L A T E D ( E N C O R E 1 R O O M T E M P E R A T U R E

-

z

--- P R E D I C T E D 23.3 kWh T O T A L

DATE, D E C E M B E R

C O M P A R 1 S O N O F M E A S U R E D A N D C A L C U L A T E D ( E N C O R E 1 A U X I L I A R Y C O O L I N G P O W E R

-