Active Solar Rock-bed Heat Storage Design Details: Active Solar Energy Systems
ROCK-BED SOLAR HEAT STORAGE DESIGN - CONTENTS: Rock bed solar heat systems provide active storage of heat energy. Proper rock sizes and rock size consistency for heat storage systems. Relationship of rock or stone size to heat storage system operation. Air resistance and rock size in heat storage systems. Air inlets and outlets design for rock-bed heat storage systems. Avoid Air Flow Short Circuits in Rock Bed Heat Storage Systems. Solar Age Magazine Articles on Renewable Energy, Energy Savings, Construction Practices.
Active Solar Heat Storage Using Rock Bed Storage Systems
Accompanying text is reprinted/adapted/excerpted with permission from Solar Age Magazine - editor Steven Bliss. Our page top photograph shows a ceramic tile floor installed in Buenos Aires. Using ceramic tile finish flooring over a rock bed heat storage system is one method of design for a solar-heated radiant heat floor system.
The question-and-answer article below paraphrases, quotes-from, updates, and comments an original article from Solar Age Magazine and written by Steven Bliss.
Rock-bed or Stone-Bed Design for Solar Heat Storage and Radiant Heated Solar Floors
Question: Where can I find information on rock-bed or stone-bed heat storage system design?
I'm curious about rock-bed heat storage systems such as those used with active or even passive solar heating systems for homes. Have any tests been done to determine the optimum size of the rocks (or stones) for these heat storage systems? How can I assure good circulation of the air through the heat-storing stone?
Where can I find information on rock-bed heat storage design? - Kenneth Leifheit, Batavia IL
Answer: rock sizes, rock size consistency, air inlet and outlet specifications for rock bed heat storage systems:
Proper rock sizes and rock size consistency for heat storage systems
Rocks used in a rock-bed heat storage system can be anywhere from 1/2 to 6-inches in diameter. The standard stone size seem sto be 3/4" to 1 1/2" in size.
It is not a good idea to mix widely divergent rock sizes. The largest rocks (or stones) should be no more than twice the smallest rocks. Holding to this rule may require some screening after the rocks are delivered.
Relationship of rock or stone size to heat storage system operation
Large rocks in a heat storage system heat up slowly and cool off slowly.
Small rocks both heat up and cool off more rapidly.
Air resistance and rock size in heat storage systems
The smaller the rocks in your heat storage system design, the greater will be the resistance to the flow of air, meaning that a larger, more powerful fan is required unless the air path is very short.
Air inlets and outlets design for rock-bed heat storage systems
Air inlets and outlets for a stone-bed heat storage system must be designed to channel the air so that it wends its way through the rocks. This can be done by placing the air inlet to the rock bed heat storage system higher than the air outlet, forcing the warm air to "drop".
Alternatively you can build vertical baffles within the rock bed.
Avoid Air Flow Short Circuits in Rock Bed Heat Storage Systems
A sand-covered sheet of polyethylene plastic on top of the rocks will prevent an air gap from forming should any rock settling occur. This detail is important because an air gap over the rocks will "short circuit" the airflow that should be moving through the rock-bed and thus reduce its ability to both store and return heat to the building.
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Q&A on solar heating systems that use use rock or stone beds for storing solar heat .
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Solar Age Magazine was the official publication of the American Solar Energy Society. The contemporary solar energy magazine associated with the Society is Solar Today. "Established in 1954, the nonprofit American Solar Energy Society (ASES) is the nation's leading association of solar professionals & advocates. Our mission is to inspire an era of energy innovation and speed the transition to a sustainable energy economy. We advance education, research and policy. Leading for more than 50 years.
ASES leads national efforts to increase the use of solar energy, energy efficiency and other sustainable technologies in the U.S. We publish the award-winning SOLAR TODAY magazine, organize and present the ASES National Solar Conference and lead the ASES National Solar Tour – the largest grassroots solar event in the world."
"Passive Principles: Rockbeds", Solar Age Magazine, March 1982 - sizing and design of rock bed heat storage systems
"Building it Right", Solar Age Magazine, June 1982, practical design guidelines for rock bed heat storage systems
Steve Bliss's Building Advisor at buildingadvisor.com helps homeowners & contractors plan & complete successful building & remodeling projects: buying land, site work, building design, cost estimating, materials & components, & project management through complete construction. Email: email@example.com
Steven Bliss served as editorial director and co-publisher of The Journal of Light Construction for 16 years and previously as building technology editor for Progressive Builder and Solar Age magazines. He worked in the building trades as a carpenter and design/build contractor for more than ten years and holds a masters degree from the Harvard Graduate School of Education.
Excerpts from his recent book, Best Practices Guide to Residential Construction, Wiley (November 18, 2005) ISBN-10: 0471648361, ISBN-13: 978-0471648369, appear throughout this website, with permission and courtesy of Wiley & Sons. Best Practices Guide is available from the publisher, J. Wiley & Sons, and also at Amazon.com
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Passive Solar Design Handbook Volume I, the Passive Solar Handbook Introduction to Passive Solar Concepts, in a version used by the U.S. Air Force - online version available at this link and from the USAF also at wbdg.org/ccb/AF/AFH/pshbk_v1.pdf
Passive Solar Design Handbook Volume II, the Passive Solar Handbook Comprehensive Planning Guide, in a version used by the U.S. Air Force - online version available at this link and from the USAF also at wbdg.org/ccb/AF/AFH/pshbk_v2.pdf [This is a large PDF file that can take a while to load]
Passive Solar Handbook Volume III, the Passive Solar Handbook Programming Guide, in a version used by the U.S. Air Force - online version available at this link and from the USAF also at wbdg.org/ccb/AF/AFH/pshbk_v3.pdf
"Passive Solar Home Design", U.S. Department of Energy, describes using a home's windows, walls, and floors to collect and store solar energy for winter heating and also rejecting solar heat in warm weather.
"Solar Water Heaters", U.S. Department of Energy article on solar domestic water heaters to generate domestic hot water in buildings, explains how solar water heaters work. Solar heat for swimming pools is also discussed.
"Heat-Transfer Fluids for Solar Water Heating Systems", U.S. DOE, describes the types of fluids selected to transfer heat between the solar collector and the hot water in storage tanks in a building. These include air, water, water with glycol antifreeze mixtures (needed when using solar hot water systems in freezing climates), hydrocarbon oils, and refrigerants or silicones for heat transfer.
"Solar Water Heating System Freeze Protection", U.S. DOE,using antifreeze mixture in solar water heaters (or other freeze-resistant heat transfer fluids), as well as piping to permit draining the solar collector and piping system.
"Solar Air Heating" U.S. DOE also referred to as "Ventilation Preheating" in which solar systems use air for absorbing and transferring solar energy or heat to a building
"Solar Liquid Heating" U.S. DOE, systems using liquid (typically water) in flat plate solar collectors to collect solar energy in the form of heat for transfer into a building for space heating or hot water heating. The term "solar liquid" is used for accuracy, rather than "solar water" because the water may contain an antifreeze or other chemicals.
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