Gentle reader,
In the course of your readings in the blogosphere, your academic research, or your energy-related activism, you will likely see a number of similar and often confusing terms bandied about to describe how much power a power plant can produce (MW vs MWa), how much it generates (KWh vs MWh), how much an appliance consumes (watts vs amps), etc., etc. etc. Furthermore, these units and terms apply to two related but very different concepts - energy and power - which while often used interchangeably in common parlance, have very different technical meanings.
The end result is that all this can all be very confusing as you can often find yourself accidentally comparing apples and oranges, kilowatt-hours and horse power or nameplate capacity and average capacity, etc. Confusing these terms is easy and common and mix-ups can have major consequences for your conclusions (this post was prompted by this one, for example, which confuses energy and capacity, leading to very different conclusions…)
The following is an primer on some of the different units of power and energy and descriptions of power plant generation you may encounter and what they mean. There is a lot here and you may not encounter a need for all of it immediately. However, if you don’t have a strong physics background (and that means most of us!), or you (like me) get your kilo-whats-its and mega-whos-its confused sometimes, you may find what follows a useful summary of many of the concepts and units you need to know (and some you probably don’t). Use this as reference if you want, for times when you get confused later (and you probably will):
Power vs. Energy - What’s the Big Diff?
When trying to explain electricity, power and energy, I invariable fall back on analogies to water flows. You see, electricity flows a lot like water, following a path of least resistance, from source to sink, spring to sea. So to understand the difference between power and energy, let’s start by taking a bath. Ok, you don’t really need to get into the tub (although you can if you want… just keep that laptop dry!), but I think we can all visualize one…
Power, is a measure of the rate at which work can be done, or in our bathtub analogy, the rate at which water can flow out of your faucet. To visualize what power means, think about the size of your faucet. How high can you turn up the water? Bigger faucet = more water flow is possible = more power.
Energy is a measure of the amount of work actually done. In our bathtub analogy, energy is a measure of the water actually in the tub. How many gallons are in their after five minutes?
Continue reading ‘Kilo-who’s-its and Mega-what’s-its: A Primer on Energy, Power and Capacity’