Off-Grid Photovoltaic System in a Temperate Climate Greenhouse in Virginia

Most buildings require power produced by fossil fuels, the extraction and consumption of which contaminate our environment. The Virginia Center of Basic and Applied Science (CBAS, INC) constructed a building in a remote forested area as a plant and fish nursery (and living space for staff) to be operated by solar electrical power. Comfortable summer interior temperature is facilitated by an open design, 15,000 cubic foot interior, ceiling fans, many large windows and doors, with a large sun-screen eave off the 1000 square foot south-facing roof. Comfortable winter temperature is possible because the building has no tree-shade, thick well-insulated walls and roof, a low number of air changes per hour, and when necessary the surrounding forest provides wood stove heat. The energy challenge of the research was to develop a system facilitating 24-hour and year-round use (primarily for lights, fans, pumps, heaters and staff living requirements) that did not need to be connected to the local electrical utility company. On average, the facility uses 3-4 kilowatt hours per day. The solar power is captured by 8 solar panels which charge a bank of deep-cycle batteries, which in turn generate the power for the facility. The complete system (solar panels, charge controller, batteries, DC-to-AC inverter, 110-to220 transformer) cost about $10,000, about 5% of the total facility cost.