Innovative methods of capturing solar heat for earlier harvests

Innovative methods of capturing solar heat for earlier harvests

Summary

FNE06-578: “Innovative methods for capturing solar heat for earlier harvests.”

Interim Report, Jan ‘07

The goals of this project are:
1. To cheaply warm spring soil by covering blocks of beds with used greenhouse plastic, and to document the patterns of soil warming and resulting effects on germination and date of first harvest.

2. To prototype an inexpensive roller for a greenhouse night blanket, for use on early and late season salad crops in an unheated greenhouse.

Progress has been slow on this project, but all materials are now in place. Work on section 1 will begin in the early spring, approximately the first of April.

Section 2 has seen some progress. We are grateful to Tek Supply for the donation of three large rolls of their Tekfoil; the foil-faced bubble insulation that will serve as the night blanket. We are not yet rolling this blanket over salad crops, though the axle and hub arrangement for the roller has been through several iterations, moving always toward simplicity. The current design (which works well on sawhorses) employs an axle built of 2×6 stock, and cross-shaped in section. At each end of the16 foot long axle we have constructed a hub of simple plumbing parts. First, a mounting flange for 1.5” pipe is bolted into the end grain of the axle. A 6” length of 1.5” black iron pipe (threaded at one end) is then screwed into the flange. The projecting pipe stub rides in an old-time farm “bearing”- an oiled, greased, and slightly oversized hole drilled through a white oak 1×6. We moved toward this simple solution because of the careful alignment required by machine-made axle bearings; at misalignments greater than 3%, bearing life is shortened considerably. Under greenhouse conditions, this tight tolerance seemed both unrealistic and unnecessary.

The axle turns quite smoothly within its scrap-pile oak bearing, friction providing just enough resistance to assure a steady rotation as the cover is unwound. When the rig moves from sawhorses to the greenhouse, the white oak boards (and their holes) will be incorporated into removable wooden stands, one for each end of the roller assembly. The cover can then be rolled and unrolled onto wires stretched above an existing crop of winter greens. We hope to begin measuring effects on soil temperature in the early spring of ’07, and resume in greater depth next fall and winter.

Paul Lacinski
Sidehill Farm, Ashfield, MA
January 25, 2007

Collaborators: