(613c) The “Green Latrine”: Deployable Latrine with Off-Grid Photovoltaic/Thermal Energy

The US Air Force has a goal of reducing field consumption of fossils fuels in order to improve energy efficiency and operational resiliency. One cost-effective solution is to provide field assets that can operate independent of the power grid by harnessing renewable energy. This paper details the design, construction, and assessment of a proof of concept deployable latrine powered exclusively with Photovoltaic/Thermal (PVT) energy technology that allows operation completely “off-grid”. PVT arrays are traditionally used for parallel production of solar electrical power and water heating in residential recreational pools. The attachment of a heat exchanger to the back of a traditional PV panel allows for cooling of the panels, resulting in higher electrical output while simultaneously heating the water.

A standard military portable (containerized) latrine unit was retrofitted with PVT hybrid panels that generate hot water and electricity. Potable water is the only required input. The installed electrical production capacity totaled 2.475 kW with an associated battery bank (44 kWh). The PVT added 6.0 kW of additional potential thermal energy depending upon variation in the panel flow rates and PVT configuration.

The capabilities, operating characteristics, and overall power gain of the configuration was examined during studies at Tyndall Air Force Base, Florida, and results will be presented. The system’s performance is examined under varying operating scenarios to assess electrical and thermal performance. Overall energy efficiency was determined in respect to electrical capacity, electrical storage, and operating utility.