7 - Powering Alcatraz

WAYSIDE LAYOUT: Cream colored, horizontally oriented panel with a dark banner running across the top. The banner reads “Golden Gate National Recreation Area” on the left and the National Park Service logo on the right. The top half of the wayside has two columns of text. The bottom half has a visual depiction of how the power system works on Alcatraz.  

TEXT: Powering Alcatraz: What do you hear? If you hear seagulls but not the roar of diesel generators, then Alcatraz is being powered by a system of photovoltaic cells and batteries.  

Golden Gate National Recreation Area is reducing its carbon footprint and demonstrating the use of renewable resources here at Alcatraz Island. Before the park installed photovoltaic cells on the cell house roof, diesel generators produced all of the island’s electricity. The new photovoltaic and battery system reduces diesel CO2 emissions by about 700,0000 lbs. (318,000 kg) per year; equivalent to electricity-related CO2 emissions from about 200 San Francisco area homes.  

VISUAL LAYOUT: Starting at the top left and moving counter-clockwise 

DESCRIPTION: Photograph of the photovoltaic panels on the roof of the cell house. There is an arrow coming from the right side of the image with a blue dotted line, directing towards a controller in the center of the wayside.  

CAPTION: When sunny, 959 photovoltaic (PV) panels power the island. Any surplus electricity charges a bank of batteries storing it for later use.  

DESCRIPTION: Colored image of a battery bank that is holding 12 batteries in 2 columns. An arrow is coming from the right side with a blue dotted line, directing towards a controller in the center of the wayside. 

CAPTION: lead Acid Battery Bank. If photovoltaic power cannot meet the island’s electrical needs (about 70-80 kilowatts), batteries will supply the remaining demand with stored electricity.  

DESCRIPTION: Colored image of an inverter. It is a box shaped device that has two inputs on the side. Above the image is a double-sided arrow with a blue dotted line, connecting the inverter to a controller in the center of the wayside.  

CAPTION: Inverters. The inverters convert DC power from the PV system or batteries to AC power used by the island’s electrical system.  

DESCRIPTION: A black and white image of a diesel engine, with pipes and wires showing. From the top of the image, are three lines, a blue dotted line leads to the controller at the center of the wayside. The two other lines are green double lines. One of the lines directs left towards the inverter. The other double green line leads above towards a battery. Above the image is another green double line that directs back to the right from the inverter to a battery.  

CAPTION: Diesel Generators. If PV and battery power is insufficient, diesel generators will start to meet the island’s electricity demands. Any excess power generated is used to recharge the battery bank.  

DESCRIPTION: A legend describing the line types used in this diagram. A blue dotted line represents Data transfer. A green double line represents converting DC to AC power. Next to this legend, to the left, is a picture of a battery.  

DESCRIPTION: In the center of a wayside, and where all the blue dotted lines direct, is a black box controller.  

CAPTION: Controller. The controller maximizes renewable energy use. It directs the inverters to meet the island’s power demand first with PV output, then with stored power from the batteries, and finally will start the diesel generators if PV and batter power is too low.  

DESCRIPTION: On the bottom right of the wayside is a QR Code to scan to learn more.