# Defining Hydrogen: P for Power

June 16, 2022 Defining Hydrogen from A-Z: P is for Power

Continuing in our Defining the Hydrogen Economy series, today we will focus on the letter P and will be discussing Power, and how it relates to the Hydrogen economy.

What is Power? When thinking of power, several definitions come to mind, many of which extend beyond its scientific meaning. However, rather than discussing power as related to presidents, countries, leaders, kings, and queens, today we will be discussing power in science and physics and how it relates to Hydrogen.

Revisiting the physics definition, power is the amount of energy transferred or converted per unit of time. Power is defined as the rate of doing work.   Power is a time-based quantity, which is related to how fast work is done. The more power in a system, the farther the distance it can move an object, and the more energy it expels over time. For example, think of a bicycle versus a motorcycle. One uses more energy in the same amount of time and thus has more power. You can get from point A to point B much more quickly on a motorcycle than on a bicycle.

The unit for standard metric work is the Joule and the standard metric unit for time is the second, so the standard metric unit for power is a Joule/second, defined as a Watt and abbreviated W. The Watt is named after the man responsible for first attempting to measure the rate at which work is done and the power needed to do the work in the 1700s, Scottish engineer James Watt. The power output of electrical equipment such as light bulbs or stereos is typically advertised in watts.

Mathematically, power is computed using the following equation:

Power = Work / time or P = W / t

Watt is also responsible for the concept of horsepower (hp), which is often used to measure the power of motor vehicles and other machines. Power in mechanical systems is the combination of forces and movement and the product of a force on an object and the object’s velocity.  Mechanical power is also described as the time derivative of work.

Power can be addressed in different ways. When discussing power, people are usually referring to average power (Pavg). As mentioned previously, it is the amount of work done in a period or the amount of energy transferred in a period of time. There is also instantaneous power (Pi) which is the power measured at a given instant in time and peak power (Ppk) which is the maximum value the instantaneous power can have in a particular system over a long period.

We mentioned the concept of horsepower. There are different definitions of “horsepower” because of the imperial system and the metric system. The U.S., Liberia and Myanmar still use the imperial system, which uses distances, weight, height and other area measurements that can ultimately be traced back to body parts or everyday items. The rest of the world uses the metric system, which uses measuring units such as meters and grams, and adds prefixes like kilo, milli, and centi to count orders of magnitude. The value of imperial horsepower is 1hp = 745.7 W while the value of metric horsepower is 1hp = 735.5 W. “Horsepower” is sometimes used loosely so it is important to under the context.

Now that we discussed what power means, how does it relate to Hydrogen and the clean energy economy. Hydrogen and specifically Liquid Hydrogen, Liquid Electricityas an energy carrier is a source for power generation. In power generation, hydrogen is one of the leading options for storing renewable energy.  Hydrogen power plants and hubs are expected to be the future for clean energy power generation.

Please look for next week’s blog as we go back to the letter O and talk about Ortho Hydrogen.

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