by Ken Torino
This is the first in a series of articles about human energy.
Human energy has been around for hundreds of thousands of years and human energy converted to electrical energy for a hundred years. Most of us can recall a WWII movie where a hand crank or pedal powered generator is being used in the jungles of Indochina or an island in the Pacific to run a military radio.
So, what are the pluses and minuses, compared to other forms of energy?
When you think of emergency or off-the-grid power must people think of solar or gas generators. Let’s talk about the alternatives first and then look at human powered energy.
Gasoline generators work, of course, and come in various sizes for different power requirements. The plus is you can get power with no effort. You start it up and you get power. So what are the downsides? For one, it is heavy. You will be using a gas generator at home or someplace you can drive to but you will not be carrying it to areas that far from a road. It needs gas, of course, and you don’t want to store large quantities of gas, so you need a supply. In an emergency, gas is usually hard to get. It is pumped from the ground with electricity. Gas generators are also noisy and give off exhaust. So it needs to be operated some distance from a residence. In Puerto Rico after hurricane Maria the gas generators had to be chained to utility poles so that they did not disappear. So the very situation you get a gas generator for, a loss of power in an emergency is exactly the situation when they are hard to keep running. So they work but you have pluses and minuses.
Solar converts sunlight to electrical energy via solar panels. Since they are powered by sunlight, they work best in bright sunlight. The chart below from the Dept. of Energy gives you the number of Watt-hours of energy you can get in a day on average per square foot of solar panel.
So the good news with solar is you can scale it to get the power you need. The solar panels have to be out in the open as shade or clouds reduce the power significantly. Also it does most of its work between 10am and 2pm and this energy is stored in a battery pack. This battery pack needs to be large enough story the energy to be used during the other 20 hours. You may ask why only four hours a day. Think about how much the sun warms you on a sunny day. In the first hour or two it does not warm you much, same for the last couple of hours. Around noon you get the most warmth. The reason for this is the energy of the Sun is dissipated as it goes through the atmosphere. If it is straight as in noon it goes through the least atmosphere. At a sharp angle it goes through a lot more atmosphere. If you ever drilled through a piece of wood, straight through, at 90 degrees, or at a 45-degree angle, you had a lot further to go at 45 degrees. In Saudi Arabia you get a lot of energy from the sun and in Finland not much. So, where you live will determine if Solar will work for you.
Then there is the battery pack to store the energy. This battery pack will need to scale with the size of the solar array and will need to be replaced on a regular basis. Solar panels are popular in the Caribbean. There is a lot of Sun energy there and electrical power distribution is unreliable. But In Hurricane Maria, the solar panels were on the roofs and were all trashed by the wind.
Last let’s get back to human power energy. The good news is it is small portable and can be used indoors at any time. The down side is it takes effort and the amount of energy is limited by the human being, about 75 Watts on a sustained basis.
So what is the answer? The answer is first start with what you are trying to do. What are you trying to power? And then which of these is the best solution? Or, which two or three in partnership are the best solution?
As is aptly said two is one and one is none.
In the next issue, we will examine in more depth what you can do with human power and what solutions are available.