Page 20 , RAIN May 1978 SOLAR CANADA: A Technology Summary 4(1 l--- t---l-'--t------1-----1- ----1HO t--- t---t-----,1---------1D In a developing field like renewable energy there is no single technology ½'.hich is superior to the others; rather there is a spectrum to be considen;d. Of the 60 or so solar space-heating systems documented in The Sun Builders, no two are alike in their design, materials, operation and integration with the house. It is still too early to assess the relative merits of each system; there are too many variables to consider. In addition, most systems have yet to go through the true test; a ~anadian winter. What we can do, however,·is identify some of the trends which have evolved. The following graphs ·summarize many of the solar houses in Canada. Graph 1 compares the storage volume for air and water systems as a function of collector area, The two bars represent equivalent heat storage capacity. Five gallons of water stores an amount of heat equivalent to 2.0 cu. ft. of rock stoq1ge. • 4.0 3.6 3.2 2.8 2_.4 2.0 1.h 1.2 0.8 0.4 Graph 1 AIR-ROCK Cubic feet per square foot of collector IK-1)..;. 127) - ,2~, - 1~2)- (17) - 11~)- }Q 9 6 WATER Gallons per square foot of collector Graph 2 compares the ratio of the collector area to the floor area with the per~entage of the house heat load carried by the solar system. The accepted rule of thumb is that the collector area should be one-half of the heated floor area. Few houses foll(?W this guideline, most having only 10 to 40 percent of the floor area as collectors. As would_be expected, it generally holds true that the greater the collector area, the greater the percentage of h~at the system is able to provide. The houses which deviate from this correlation generally do so for a reason. For example, seven houses appear to be more efficient than _would be ex- , pected; that is they supply a large percentage of heat for a , relatively small area of collector. Two of these houses have long-term storage, two have a large reflect9r (effectivelyincreasing the insolation on the collectors), two systems incorporate heat pumps and one house is insulated to R-60. ~ ~ ill - -1-----D-n~-----+----+----< >+---------1 ~~ - D ;;., (I) a: Ml - ------ - ::::: C r-. ;:; < ..l 0 • ~ 'itl -----i:JCD•D----OOJl:tt---~::::1: -+- -+- ~ C 0 Cl ~11 t-------10-=--.. ,...~.vf-----r-■.nOr-+----+----+----+- DD i.i !-- < D ~ - 111 0 0 20 - ---- - ---------+- Ill l---t---t------1-----1- ---1----110 2() )(l 40 _50 I,() % COLLECTOR AREA/FLOOR AREA Graph 2 o commtn:w O do-it-yourself Graph 3 indicates that costs vary tremendously from one system to another. They range from a low of about $1.70 per square foot to a high of $96 per square foot. The do-it-yourself systems, where the cost includes materials and not labor, are generally less expensive than the commercial units. Air systems (denoted by the grey marks) are generally cheaper. The lowest cost do-it-yourself water systems are generally of the trickle-type. Most of the inexpensive.commercial systems are air systems that have been integrated with the house during construction. Generally speaking, a cost of $20-$2 5 a square foot or less can be considered an economically justified investment. This will vary substantially from system to system, house.to·hou~e and r_egion to region-. Over half of the homes listed are economical by that standard. 0 4.~I \\&.llibl 12 "'. &7) (.-, Ul • • • • ,... .01 ■ • • )5 • = = - I H ~ -' J ■ • ,,;- ~:, ■ I ' (11,1 h,1 ■ • • 10 ■ • •• = ., • t • 1 ~ - • 0.5 1.0 1.5 2.0 2.5 3.0 % HEATED IIY SOLAR SYSTEM ~ COLLECTOR AREA/FLOOR AREA ■ ■ commercial ' • • clo-il-yo,unelf Graph 3 Editor's Note: The Sun Builders, from which this note was adapted, is available from bookstore_s or directly from the publishers, Renewable Energy in Canada, 415 Parkside Drive, Toronto, Canada, M6R 227. Price: $8.00 including postage. (Courtesy Solar Energy Society of Canada)
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