Center for Sustainibility

Off-the-Grid Homestead Project

 

Ryan German

 

Executve Summary

The motivation for the Off-the-Grid Homestead project is Dave Lettero [1], a Penn State graduate student who will attempt to live for one year removed from the electrical grid in a yurt structure as part of his thesis. There are two main design focus areas for the Off-the-Grid Homestead project. The first objective is to design an electrical system consisting of a PV array, batteries, inverter, etc. to power the basic requirements of a person living in a yurt structure. The second goal is to design a heating system with solar hot water collectors that will satisfy thermal comfort of the occupant during the winter months.

There are four major tasks for the project group. The first will be to layout the components on the site in an optimal arrangement to maximize solar energy collection and minimize losses between the collectors and the yurt. The second task is to design the electrical system including photovoltaic panel layout on the portable trailer, battery banks, and the associated wiring. This system will contain a charge controller and inverter to distribute AC and DC power to the yurt. The third task is to provide preliminary heat load calculations for the yurt structure. From preliminary heat load calculations, 7500 BTUs/hour will be required to maintain the yurt at 65 °F with an outside temperature of -3 °F and 15 mi/hr wind. The fourth task is to design a solar hot water heating system for the yurt, including the provided solar heat collectors, and storage tank, and a structure to support the components. The collectors provided were tested for pressure drop at given flow rates. After repairing Collectors #1 and #2, a flow of 0.8 gpm through each collector in parallel was achieved with a minimal pressure drop. Collector #3 had a badly cracked tube sheet that is likely not repairable, rendering it unusable. Collector #4 is also unusable. The design budget for the project is currently $600, though additional funding will be needed to purchase the components needed to build the proposed structures. Prices have been estimated for several of the major components. If new solar heat collectors are needed to replace the damaged ones, each will cost $800. [2] To put new covers on the usable collectors, $128 per collector is needed for polycarbonate twin wall glazing and aluminum framing. [3] The circulating water pump will cost around $200. [2] PEX tubing to carry water between the collectors, barrels, and yurt will cost $133. [4] Additional plumbing supplies such as fittings, valves, copper tubing, etc. will account for $80.