9. Lexical Exercises

1. Put the correct words from the table into the text:

Photovoltaic (PV) 1)_______ produces electricity from sunlight, using solid-state materials with no moving parts. It’s a mature technology, first 2)_______ by Alexandre-Edmond Becquerel in 1839 and initially commercialized at Bell Labs in the 1950s. For residential application, PV falls into two main categories. First is 3)________ , where the home generates its own electricity but can also draw power from the utility company at night. The second is 4)________ , where the home is located too far from an electrical utility 5)________ and the home must generate its own power, storing energy in batteries for use at night. A basic 6)________ PV system consists of PV 7)________ connected and packaged together in weather-protected 8)________ , which are fastened side-by-side on a racking system to form an 9)_________. The PV modules produce direct current (DC), which in a grid-tied system flows to a grid-interactive 10)________ . An inverter 11)________ DC voltage to the alternating current (AC) for the household electric 12)_______ powering wall outlets and all AC appliances. Excess power from the inverter may 13)________ of the house through the utility company’s electric meter, into the city-wide grid. When this happens, the meter may run backward, and the utility will credit the outflowing electricity against electricity purchased from the 14)_________ at other times, like at night. This process is called 15)_________ . In an off-grid system, DC power flows from the modules through a charge controller (also called a regulator), which is an electronic 16)_______ that produces a smooth flow of current at the desired voltage. From the charge controller, the power can go to a set of storage batteries and then on to the inverter, as needed. Today’s commercially available PV 17)_______ come in three versions: 18)_______ (or monocrystalline) modules are currently the most efficient — that is, 1 square meter produces the most electric power. They must be 19)_________ in a rigid frame. Multicrystalline (or polycrystalline) modules are 20)________ cells cut from multiple crystals, grown together in an ingot. They are slightly less efficient than single-crystal.

1.	(a) table	(b) technology	(c) system
2.	(a) invented	(b) discovered	(c) found
3.	(a) on-grid	(b) grid-on	(c) grid-tied
4.	(a) off-grid	(b) grid-tied	(c) grid-on
5.	(a) lace	(b) wire	(c) cable
6.	(a) building	(b) home	(c) house
7.	(a) cells	(b) elements	(c) components
8.	(a) batteries	(b) modules	(c) cells
9.	(a) light	(b) warm	(c) array
10.	(a) inverter	(b) voltage	(c) transformer
11.	(a) causes	(b) alters	(c) changes
12.	(a) circuit	(b) diagram	(c) chart
13.	(a) flow in	(b) flow out	(c) flow out of
14.	(a) grid	(b) scheme	(c) net
15.	(a) conductivity	(b) headers	(c) net-metering
16.	(a) apparatus	(b) device	(c) instrument
17.	(a) plates	(b) batteries	(c) panels
18.	(a) single-crystal	(b) mono-diamond	(c) single-diamond
19.	(a) fixed	(b) mounted	(c) installed
20.	(a) put in	(b) consist of	(c) made of