With a system total of 7.4 kilowatts, the Ripple Home is powered by one of the most highly efficient photovoltaic (PV) systems available on the market.

To achieve power and versatility no matter the weather, the SCU Solar Decathlon Electrical Engineering Team designed a competition-scale photovoltaic array supported by high-efficiency inverters and a large battery bank. Our battery reserve consists of eight 2,500 lb lead-acid batteries, and is capable of lasting for five days of no sunshine at normal power consumption. 34 SunPower SPR-215 photovoltaic panels, the highest-efficiency panels available on the market, convert energy from the sun into electrical energy for home consumption. Since our home will be disconnected from the power grid during its time on the National Mall in Washington, D.C., our electrical system is designed to elegantly handle life untethered.

Life Untethered

Photovoltaic energy is captured by panels as direct current (DC) and must be converted to alternating current (AC) before powering any household appliances. Two SunnyBoy inverters accomplish this at almost 96% efficiency, nearly eliminating energy waste. On sunny days, a PV system can easily generate excess power, which is passed though the SunnyBoy inverters to two SunnyIsland (or bi-directional) inverters which convert the electricity to DC for battery storage. Later at night or on a cloudy day, this energy is pulled from the batteries through the bi-directional inverters and into the home.

Some less-efficient PV systems take power directly from the panels for storage in the battery bank. From there, power goes through inverters and into home appliances. While this system may be easier and cheaper to wire, we chose to capitalize on the high-efficiency of immediate power usage - thus completely bypassing the battery bank when possible - allowing us to leave our batteries fully charged whenever possible.

Flexibility for Living

In addition, the SCU Solar Decathlon Electrical Engineering Team wanted to design a dwelling capable of operating while connected to the power grid (on-grid) or while standing independent (off-grid). Their solution to this solar conundrum and the lack of flexibility in traditional systems was to design a "modularized" electrical system, meaning various components - PV panels, electrical inverters, and batteries - can be increased or reduced in number, or altogether eliminated, without affecting the overall functionality of the system.

For example, say you would like to live on clean power from the sun, but would like to remain connected to the energy grid. You could eliminate half of our 34 PV panels, the entire battery bank, and both bi-directional SunnyIsland inverters without having to rewire or reconfigure the overall system. During the day/summer, you power yourself with sunshine. During the night/winter, you rely on the energy grid.

Whether you want to live miles from any power lines or on the corner in a suburban neighborhood...we built the system for you.

	click to watch a flash animation explaining how photovoltaics work (alternate flash-free image)

photos courtesy Mike Kahn www.greenstockmedia.com