Many do-it-yourself homeowners are interested in
trying out solar power to leam about the technology and
perhaps to provide energy for limited-use applications．
There are a variety of ways to find cheap solar panels
（板）, including buying used and building your own
with factory seconds．Both methods will save money
while forcing you to learn the ins-and-outs of a solar
power array （阵列）．  
We've all seen solar-powered street signs or PV
panels being used for various purposes at remote locations．
When those units become cracked or chipped and are considered "unsafe", companies are forced to replace them, generally to avoid responsibility issues．Because it's difficult to get rid of PV panels, many companies, if approached, are willing to give them away or to sell them for modest prices．Depending on the degree of damage present, expect to see performance degradation （降级） in the range of 10% to 60%．A multimeter （万用表） can be used to test the panel before buying．If the panel's free, take it anyway．It could still be useful in a home solar project．
A solar panel is really nothing but a box serving as a container for a large group of solar cells．Factory second solar cells are usually sold on eBay at a small part of their regular cost．The cells come in a variety of sizes．You will need to figure out how much power a single cell produces to determine how many will need to be wired together to form an array．
A simple search of the Internet will show numerous sites detailing home solar panel projects．Do-it-yourself lovers are generally quite generous in supply photographs of their work and description of what went wrong and right with the project．
Getting cheap solar panels with slight imperfections, either used or through sales of factory seconds, is a perfect solution for home-built renewable energy projects．The high number of solar lovers online provide a wealth of useful information．Only limited skills are required, plus an understanding of the basic wiring involved．All are well within the talents of almost any home handyman．Beyond the satisfaction of having completed the project, you'll come away with a functional solar panel that will be a source of power for use around the house or at remote locations．
Solar energy systems are quickly becoming more popular with homeowners as prices continue to decline．
72．The author writes the passage to introduce ____．
A．ways of finding cheap solar panels B．ways of saving energy
C．a way of making a solar panel     D．a home-built energy system
73．What does the phrase "factory seconds" in the passage refer to?
A．Second-hand factory products．  B．Cheap but perfect factory products
C．Faulty factory solar cells．        D．The second best factory solar cells
74．From Paragraph 5, we can learn about home-built energy projects that ____．
A．none of them are beyond home handymen
B．a lot of useful information is available on the Internet
C．a perfect solution is to get cheap and perfect solar panels
D．understanding electrical wiring is not necessarily needed
75．What is the author's attitude towards the future of solar energy systems?
A．Optimistic．  B．Pessimistic.      C．Indifferent．         D．Doubtful