Engineering is the application of science-the knowledge of laws of nature-to the betterment of mankind. Through the engineering per spective on technology, we come to understand how technology trans fonns matter and energy into forms that are more readily usable, such as solar radiation into electric energy. We can describe any transformation process in terms of its inputs and its outputs.
The word technology refers to the process of transformation or, more
deeply, the knowledge of the laws of nature that underlie the transforma tion process. We may also use the word technology to refer to a class of devices that use the same transformation process. Devices that employ the same technology differ most noticeably in their size. The capacity of a. device is a measure of its size, and usually-but not always-we measure capacity by the output rate of the device. For exampl; power technolo gies produce energy, so their capacity is measured in energy output per unit of time, such as British thermal units (BTUs)/hour for a furnace or watts (W) for electric power.
In this chapter, we look at a variety of transformation processes to see the range of the concept of technology. We see how to describe the capac ity of devices for various technologies, and we also take a close look at power technologies and their associated measures of energy. This chapter addresses several fundamental questions:
• How do engineers describe the size of different devices?
• The output of a power technology can variously be measured in BTUs per hour, in kilowatts (kW), or in horsepower (HP). How do those units con1pare with each other, and in what
con texts are they used?
• Which units of tneasurement are used to describe energy, in which contexts, and how do they compare with each other?
• What does the capacity factor of a device tell about the operation of the device?
Technology Is a Transformation Process
Technology transforms inputs into outputs (and byproducts) under specific environmental conditions. Figure 2.1 reminds us of the basic relationships between inputs, process and outputs in the transformation process.
Examples of technologies described 1n this manner are shown in
Table 2.1.
In the following sections, we consider many examples of sustainable technologies, looking specifically at how to measure the inputs and out puts based on the science underlying the transformation process. We give