Passive Solar Greenhouse
with Mass Subsoil Heat Storage
A Concept in Search of a Prototype

Inspired by design concepts communicated to me by Don Stephens InA, Private Eco-shelter Design Consultant, Author, Teacher, Mentor and Alternative-construction Innovator
P.O.B. 1441 Spokane WA 99210-1441 USA www.greenershelter.org , don@greenershelter.com
Vice President and Founding Member, Inland Chapter, Northwest EcoBuilding Guild
Architectural Advisory Board, Spokane Falls Community College, Spokane WA USA

For a backgrounder on the conceptual framework for this design, please see this article by Don Stephens, InA "Annualized Geo-Solar Heating as a Sustainable Residential-Scale Solution for Temperate Climates With Less Than Ideal Daily Heating-season Solar Availability"

The greenhouse depicted here would be 17' high from ground to peak, 27' from the front of the solar collector to the back wall of the structure and any desired length.

The construction of the greenhouse itself would incorporate all the basic and well tested components of a passive solar greenhouse including double glazing, tromb wall, high R-value insulation on the northern side and roof and thermal blinds.

In addition, a solar hot air collector is incorporated. During the summer months, ducts leading from the collector and buried 8' deep within the subsoil beneath the greenhouse would heat the subsoil mass. Hot air from the collector would be drawn down and through the buried ductwork by means of convection (the air in the ducts embedded in the tromb wall being heated sufficiently to create an updraft in the solar chimneys).

An insulated 'cape' extends 15' in all directions around the greenhouse to prevent heat loss from the subsoil mass.
3D Rendering

Heat accumulates over a period of three to four years in the subsoil mass and ultimately results in interior greenhouse temperatures in mid-winter approaching 70ºF from the subsoil mass alone. This heat reservoir is augmented by winter insolation as well as the recirculation of interior greenhouse air through the solar collector during the winter months when the subsoil ductwork is closed off and the cold air return inlet is opened.
3D Rendering

The solar hot air collector operates in two modes:

In the summer, air from outside enters from the front. The air is heated between the top glass and black-painted sheet-metal and is drawn out of the collector by the suction of the subsoil ducts.

In winter, the cold air intake from the outside is closed off, as are the subsoil ducts. Cold air return intakes are opened in the lower back of the collector allowing cold air from inside the greenhouse to enter the collector, absorb solar energy and re-enter the greenhouse through openings in the upper back of the collector.
3D Rendering
 

*Chrys Ostrander, originator, thefutureisorganic.net
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