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1947-48 Theatre Catalog, 6th Edition, Page 425 (411)

1947-48 Theatre Catalog, 6th Edition
1947-48 Theatre Catalog
1947-48 Theatre Catalog, 6th Edition, Page 425
Page 425

1947-48 Theatre Catalog, 6th Edition, Page 425

FIGURE Fin the house unit it was found desirable to prevent breakage

a galvanized iron screen with 5-inch openings. other hand, that no protection from snow was necessary. since the tilt

which it would be uneconomical to attempt solar heating. It is, therefore, felt that, in locations north of the fortieth parallel, the cost of heating houses by solar radiation would generally be too high for economical application of this principle. Collector and storage units would have to be unduly large and their cost would be a considerable drawback. It is possible, however, in a few northern localities, where considerable winter sunshine is obtained and where temperatures are not extremely low, economical use might extend considerably above the fortieth parallel. This would be particularly true where fuel is expensive. As further explained below, the greatest application of this solar energy collector should be in the southern portion of the United States.

Certain considerations of the other uses of the collected solar energy have also been made.

The first of these involves the possibility of using the heated air to operate an absorption type of refrigeration air conditioner. Such a unit is available commercially, and the application of solar energy to its operation is considered to have excellent possibilities. It is apparent that the period in which the greatest energy is received corresponds exactly to that period in which the greatest cooling is required. The apparatus would, therefore, be able to provide the most cooling at the time it is needed.

it is felt that, perhaps, the region of greatest applicability of this equipment is in the southern half of the United States, where winter heating loads are not too severe and where summer cooling is greatly desired.

The heating of water for household uses has also been considered, and equipment for this purpose has been installed in the house unit. No complete results of its operation are available, beiause of its late installation, but a few observations show that, particularly in


It was found, on the

the summer, it should be possible by using solar-heated air to heat sufficient water to the temperature required for household use.

Other possible uses for solar energy might be to provide a continuous supply of clean, heated air or other gas to certain industrial processesesuch as drying or crystallizing.

Numerous factors have not as yet been investigated because of certain limitations. The most important of these problems is that of heat storage. M0st of the envisioned uses for the solar energy recoverable by this process are predicated on the assumption that storage of the heat for at least 24 hours can be successfully and economically provided. This problem has not yet been investigated experimentally, because it was considered beyond the scope of the study covered by this report. It is expected, however, that studies now being planned will show that storage of heat can be accomplished satisfactorily. On this assumption, result of heat storage calculations have been included in this report. They indicate that storage of heat only overnight in a bed of crushed solid, will more than double the heating load carryable by the solar unit, and will not require a storage unit too large for practical use. An additional benefit, not yet determined quantitatively, is the higher storage temperatures which can undoubtedly be obtained when the hot air is recirculated between the collector and the storage unit. Recently a fully automatic system, involving a storage bed, was installed in the house of Doctor Liif, with promising results.

An important practical problem, not early solved because of the lack of time, is the discovery of the fundamental cause of, and the method of eliminating, the excessive breakage of glass in the collecting unit. The frequent breakage of plates exposed to sunlight is no doubt caused by thermal stresses set up in

of the root and the smoothness of the glass allowed the snow to slide off during the hail season by covering the solar heat collecting unit with readily. The results indicate that solar energy can be used to heat air

temperatures in excess of 200 degrees and that over-all heat recovery efficiencies of at least 35 percent of total can be secured without difficulty.

the glass, but the way in which these stresses cause breakage is not definitely known. Tests conducted, which have practically eliminated the trouble, indicate that small edge cracks grow into large ones, rather than the lack of proper annealing or some other cause.

Although considerable progress has been made toward designing a collector entirely practical for the average home, more work needs to be done to make possible the large scale production of units which then can be easily installed in the house. Certain simplification and standardization in design is a necessity before wide usage can be realized.

Another subject ineriting study is the possible use of glass which has been surface-treated to reduce reflection. It would, perhaps, be possible, at comparatively low cost, to reduce materially the amount of energy reflected back to the sky from the unit, and thereby increase the efficiency.

The black coating on plates in all the tests was very satisfactory, and a special black glass surface has recently been developed. It had a high absorbtivity for solar radiation and reasonably good adherence. Future work, howeVer, will be directed toward the developinent of a coating with extremely permanent characteristics and one which could be easily applied at the glass factory.

Weather resistance of the equipment was generally very good. The use of putty for sealing the cover glasses on the house unit proved very satisfactory, c:'('91)t when it was necessary to replace broken glass. In such instances, the hardened putty prevented easy removal of the cover plates. The use of a rubber or felt scaling strip is being contemplated and will be investigated. The house unit was found to withstand a high wind very satisfactorily, but the frames holding the cover glasses on the laboratory unit were blown off and demolished
1947-48 Theatre Catalog, 6th Edition, Page 425