Lesson 1

1. What’s the most important step to ensuring that a PV system provides the highest fraction of total energy used in a home?

Answer: Performing energy efficiency measures.

2. What is a “phantom” load?

Answer: Phantom loads are caused by 120VAC to DC chargers such as cell phone chargers, and by appliances that still use power even though they are turned off, such as televisions, computers and audio equipment.

3. What building characteristics must be present in a home in order to be a good candidate for a solar energy system?

Answer: 1) maximum southern exposure without any substantial shading from 9 a.m. to 3 p.m.;
2) roof slope between 20 and 60 degrees;
3) a roof that can support the added weight of the PV system; and
4) access to the home’s wiring and/or plumbing.

4. What is direct gain passive design?

Answer: Home design that allows the sunlight to enter the living space directly. Concrete walls and floor, along with tile, and sometimes water storage features are used to absorb the solar heat gain in the daytime, and these building elements re-radiate the warmth at night.

5. Describe a Trombe wall.

Answer: A Trombe wall is the most common indirect-gain approach. The wall consists of an 8– to 16- inch-thick masonry wall on the south side of a house. A single or double layer of glass is mounted about 1 inch or less in front of the wall's surface. Solar heat is absorbed by the wall's dark-colored outside surface and stored in the wall's mass, where it radiates into the living space.

6. What is a grid-connected PV system?

Answer: A grid-connected—or net-metered—PV system is connected to the utility grid through a special meter than turns backwards when the house produces more electricity than it needs. The utility grid serves as storage, eliminating the need for batteries.