The passive solar energy book

The passive solar energy book

SolarEnergy,Vol.23. pp. 563-564 PergamonPressLtd., 1979. Printedin GreatBritain BOOK REVIEWS T h e Passive Solar Energy B o o k t For several years...

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SolarEnergy,Vol.23. pp. 563-564 PergamonPressLtd., 1979. Printedin GreatBritain

BOOK REVIEWS T h e Passive

Solar Energy B o o k t

For several years the solar, space-heating design community has awaited the publication of Mazria's passive design book. It was expected that this book would help to close the gap between active and passive design tool availability for the architect and engineer. This expectation has been fulfilled, but only to a point in the solar design process which falls short of final building design. Briefly, the book consists of five sections--an introduction, a short description of "natural" processes, an overview of the generic types of passive systems, a lengthy section on design rules of thumb called "patterns", and solar angle charts and shading calculators. The excellent collection of original graphics is the book's most striking feature. They illustrate each idea well either by the use of photographs or perspective drawings prepared by Russel Ball over a period of 4 yr. The appendices contain the usual data for a solar book--weather data, solar flux data, conversion tables along with a set of new sun path diagrams. A brief summary of a performance prediction method developed at Los Alamos Scientific Laboratory (LASL) is also in an appendix. The hard-cover, professional edition contains extra detail on performance calculations and solar mapping along with a set of sun path transparencies. Since the core of the book deals with a collection of 27 new rules of thumb (patterns) for design of various types of passive solar systems, this section deserves careful scrutiny. A typical rule of thumb (21) is that one regarding the combination of direct gain, thermal storage wall (TSW) and greenhouse passive systems: "When sizing a combination of systems, adjust the procedures given in previous patterns according to the following ratios; for the same amount of heating each one square foot of direct gain glazing equals two square feet of thermal storage wall or equals three square feet of greenhouse common wall area." Such a statement, given in bold-face type in the book is likely to be accepted at face value. However, it is based on assumptions not entirely clear and unpublished results of computer studies. The designer would use such a pattern with more confidence if its bases were available and referenced in the peer-reviewed literature. Part of another pattern (14) regarding TSW vent size states "make the total area of each row of vents equal to approximately one square foot for each 100 square feet of wall area." This boldface statement reduces the design of vents to a very simple level. However, the design of vents is not simple. What is involved is the free convection heat transfer in accelerating flow in a duct with non-isothermal walls and 90° flow entry and exit

conditions. This problem has never been examined in detail by anyone to this reviewer's knowledge. But even without a solution to this fluid mechanics problem, it is still clear that a fixed vent size independent of solar heating fraction is not ideal. For small annual solar fractions the vent needs to be relatively larger than for large solar fractions, where a relatively small vent is needed to prevent daytime overheating of the space. The one per cent rule is valid for annual solar fractions of the order of 50%. Under close scrutiny other patterns show weaknesses similar to those noted above. A consistent problem throughout the book is the author's relating of passive systems sizing characteristics to building floor area. Although widely used in the architectural community, this sizing index is simply wrong. There is no inherent relationship between floor area and heat load, the proper sizing index. Wall area would be a somewhat better basis than floor area, but still not entirely correct. The question arises: what is the source of the patterns? Some are apparently based on computer simulations using the MATRIX computer model which calculates the hourly performance of systems for one day per month (the 21st) for a year using average climatic data. It is generally recognized in the solar systems analysis community that this approach is inadequate to properly predict the performance of highly non-linear solar systems. Other patterns are based on LASL computer studies and the personal experience of the author. The technical basis for the patterns is not documented in any significant way in the book or in the published literature. The design professional will be concerned about the lack of economic analysis detail in the book. The ultimate system size must be based on economic criteria if solar heating is ever to be wide spread. Economics are treated in 3½ pages in the appendix. This is entirely inadequate for a solar design manual which claims to have "most of the information you will need to successfully design a passive solar building." Where then will this book be useful in the design process? Most of the patterns seem valid at the schematic design level. However, the two succeeding building design process steps--design development and final design (working drawings)-are not substantially assisted by this book. This may represent the state of the art of passive solar design today. If so, the less than complex technical basis for the book vividly points out where further design-tool-development dollars should be spent. Until new tools are developed, this book is the best passive design manual extant. JAN F. KREIDER JFK and Associates 1929 Walnut St. Boulder, CO 80302 U.S.A.

rE. Mazria, 436 + xii pp. Rodale Press, 1979 (Paperback Edition).

Photovoltaic generators in space, Proceedings of a European symposium, ESTEC, Noordwijk, 1 1 - 1 3 S e p t e m b e r , 1978 tions, and finally a round table discussion of the prospects for space power generation for Europe. Unfortunately, the quality of the papers varies almost as widely as their authors' treatments of their material. In this respect the book is no exception to most other conference proceedings which generally reach only a very small audience of workers in the field. Engineers intimately involved in the problems of designing and building components or integrated systems for producing electric

This book provides a fascinating overview of the technology of generating electric power in space using solar cells. Nevertheless, the book is seriously flawed by the uneven treatment of material, ranging from detailed accounts of technical work to very broad summaries of national governmental programs in the U.S. and Europe. Between these extremes the papers range over such topics as array technology, interface problems, testing, specific power supplies for particular projects, satellite solar power sta563