Energy ≠ Power
The term “power generation” is widely used to refer to the production of electricity, either in large “power plants” or by way of smaller generators such as solar panels. The electricity system is often described as the “power system”; and the industry around it as “the power industry”. Yet we also think of electricity as part of the “energy mix”, along with other applications which consume energy: in particular transport and heat.
So which is it – power or energy?
The fact is that both terms are applicable to electricity.
So you’ll see “energy” and “power” (and the units used to represent them) thrown around quite widely; but not always correctly. Both have distinct meanings and significance, in a physical sense and a business sense.
Perhaps it would be easier if everyone talked about the “electricity business” and “electricity generation plants” instead; but they don’t, they talk about the “power business” and “power plants”. So I’m going to stick to that too!
That being the case, if you’re in the “power” business, it’s crucial to be comfortable with what the terms “power” and “energy” actually mean, how they are distinct and – most importantly – how they are connected.
That’ll be the subject of the first of the video presentations, in the next lesson.
A Confusion of Units!
Whichever sector of the energy business you are involved in, another confusing aspect is how the same quantities are often expressed using very different measures (units).
In discussions around electricity, you’ll most often see units such as kW, MW and GW used for power and kWh, MWh and GWh used for energy.
But bear in mind that there are lots of other units for these two quantities too. They are used either when talking about different applications (e.g. fuels, heat, food) and/or for convenience at different scales (e.g. from individual electrical components to country-scale amounts of electricity consumption).
So in the electricity business, for energy you may hear units like MJ or GJ used too. You’ll also hear energy units like MMBtu or Therms used for natural gas fuel, calories or kJ for food, and boe (barrels of oil equivalent) for large-scale measures of a variety of sources. And many, many more!
You’ll hear the same units used for different sources and the same sources described with different units – which is potentially very confusing!
The same is true for power. While in electricity we tend to focus on multiples of Watts (W, kW, MW etc.), other units exist for other applications. Horsepower or its metric equivalent PS is commonly applied to cars. But other power units include ergs per second, ft-lb per minute and more… (depending what is under discussion).
The key thing to remember is that these are simply different ways of scaling an amount of energy or power. In the same way, we can use any of inches, metres, miles or light years to measure the same distance, depending on what makes most sense in terms of scale, or simply which is the convention in the context of its use.
So, particularly when comparing different studies, datasets or charts, make sure you know which unit is being used, before drawing conclusions!
The best way to reduce the potential confusion of different units is to familiarise yourself with them and become comfortable converting between them. And the best way to do the latter is not by any fancy maths, but to use one of the many online unit converters (or mobile apps) that exist.
Personally, I use this one online: http://www.digitaldutch.com/unitconverter/energy.htm and an app called “ConvertPad” on my phone. But search around and you’ll find there are plenty more.