Energy and man. A series of random comparisons
In physics, the semi-scientific “method of dimensions” is sometimes used to solve problems, when knowing the dimension of the desired quantity, we can guess what to divide, add, and multiply by what, in order to get the correct answer. I decided to take the dimension “energy” and compare “apples with bananas,” namely, man as an energy system with other systems.
What is energy measured in?
Disclaimer: all calculations may not be accurate and the main goal is to show the order of numbers.
A person consumes on average about 2,000 calories a day, which gives about 2 kWh or about 100 watts, of average power. One can imagine that a person eats like one big light bulb on 100 watts of incandescent light.
Human energy consumption is relatively small compared to the devices that surround us. We can say that man made a technical revolution. A person takes "less energy" into himself "than he uses" for himself "even only at home (the average calculation is more than 100 kWh per month).
It is widely estimated that the brain eats from 200 to 1000 Kcal (stressful situations), that is, from 20% -40% of energy, which gives an estimate of the average power of 30 watts.
The brain is an extremely effective system. Yes, modern laptops perform operations much better than us and the average power is about 30 watts, and phones in general are 0.5-1 watts. But modern video cards consume an average of 250 watts and still can not be compared with the brain in speed and accuracy of processing visual information. So, a person is a very good processor, but only for specific tasks.
They say that a person may not eat 3-7 days. It is clear that without eating, a person will begin to consume less energy for internal and external needs. We can assume that by eating a double daily rate, a person will be active for 2 days (in the presence of water), which gives a rough estimate of 10 kWh.
If we calculate the energy intensity of a person, then we can get very different numbers, the weight of people who can live the Nth number of days and do some useful work varies greatly from 50 kg - 150 kg. Most likely, the average energy intensity is 0.1 kW * h / kg, which is not so good and not so bad. We are located between gasoline (10 kW * h / kg) and Liion (0.1 kW * h / kg), closer to the batteries.
Today's solar panel gives about 300 watts at its peak, in moderate latitudes, the average KIUM is up to 20% (the sun shines only in the afternoon and weakly). We know that a person is short-lived, but still a battery, so on average 2 panels are enough for a person to eat only the sun.
If we discard conventions and make small breakthroughs in technology (the use of expensive elements allows us to achieve up to 40% efficiency in panels), it will be enough for a person to wear “solar clothing” in order to receive all the necessary energy.
I will quote an article about clothes : at rest, the human body generates 80 watts of heat, and loses 10 watts due to respiration, 30 watts of heat, 20 watts of heat conductivity and convection, and 20 watts of moisture evaporation.
It turns out people are extremely "weak" heater. Home heaters consume 1 kW each and they only partially cover the heating needs. Water heating and space heating are, in principle, the largest energy consumption of a household. I will give my annual alignment:
- Moving (transport, fuel): 8,000 kWh per year.
- Electricity: 2,500 kWh per year.
- Water heating and heating: 30,000 kWh per year.
It turns out that the average daily water heating and heating goes up to 100 kWh per day, which is 50 times more than a person basically consumes.
Man as an active living creature can move in space. Suppose a person can travel 30 km per day on foot and 120 km per day on a bicycle. These are not the maximum values, of course, athletes run up to 100 km and travel up to 1000 km per day.
Let's try to compare a person as an effective system of human movement.
- A car with an internal combustion engine spends an average of 5 liters per 100 km, 1 liter = 10 kWh, which gives 500 Wh per km
- Electric car - 150-200 Wh * per km
- Pedestrian - 2 kW * divided by 10-50 km, 50-200 W * h per km
- Slow / small electric car - 50-100 W * h per km
- Electric bike - 10 W * h / km (average speed 10-15 km / h )
- Cyclist - 2 kWh divided by 100-1000 km, 2-20 Wh * km.
You know more interesting coincidences - write in the comments.
Thanks for attention.
What is energy measured in?
Disclaimer: all calculations may not be accurate and the main goal is to show the order of numbers.
Man is a consumer of energy. 2 kWh, 100 W
A person consumes on average about 2,000 calories a day, which gives about 2 kWh or about 100 watts, of average power. One can imagine that a person eats like one big light bulb on 100 watts of incandescent light.
Human energy consumption is relatively small compared to the devices that surround us. We can say that man made a technical revolution. A person takes "less energy" into himself "than he uses" for himself "even only at home (the average calculation is more than 100 kWh per month).
Man is a computer. 30 watts
It is widely estimated that the brain eats from 200 to 1000 Kcal (stressful situations), that is, from 20% -40% of energy, which gives an estimate of the average power of 30 watts.
The brain is an extremely effective system. Yes, modern laptops perform operations much better than us and the average power is about 30 watts, and phones in general are 0.5-1 watts. But modern video cards consume an average of 250 watts and still can not be compared with the brain in speed and accuracy of processing visual information. So, a person is a very good processor, but only for specific tasks.
Man is a battery. 10 kWh
They say that a person may not eat 3-7 days. It is clear that without eating, a person will begin to consume less energy for internal and external needs. We can assume that by eating a double daily rate, a person will be active for 2 days (in the presence of water), which gives a rough estimate of 10 kWh.
If we calculate the energy intensity of a person, then we can get very different numbers, the weight of people who can live the Nth number of days and do some useful work varies greatly from 50 kg - 150 kg. Most likely, the average energy intensity is 0.1 kW * h / kg, which is not so good and not so bad. We are located between gasoline (10 kW * h / kg) and Liion (0.1 kW * h / kg), closer to the batteries.
Man is a consumer of solar energy. 1-2 solar panels
Today's solar panel gives about 300 watts at its peak, in moderate latitudes, the average KIUM is up to 20% (the sun shines only in the afternoon and weakly). We know that a person is short-lived, but still a battery, so on average 2 panels are enough for a person to eat only the sun.
If we discard conventions and make small breakthroughs in technology (the use of expensive elements allows us to achieve up to 40% efficiency in panels), it will be enough for a person to wear “solar clothing” in order to receive all the necessary energy.
Man is a heater
I will quote an article about clothes : at rest, the human body generates 80 watts of heat, and loses 10 watts due to respiration, 30 watts of heat, 20 watts of heat conductivity and convection, and 20 watts of moisture evaporation.
It turns out people are extremely "weak" heater. Home heaters consume 1 kW each and they only partially cover the heating needs. Water heating and space heating are, in principle, the largest energy consumption of a household. I will give my annual alignment:
- Moving (transport, fuel): 8,000 kWh per year.
- Electricity: 2,500 kWh per year.
- Water heating and heating: 30,000 kWh per year.
It turns out that the average daily water heating and heating goes up to 100 kWh per day, which is 50 times more than a person basically consumes.
Man is a means of transportation (car, pedestrian, bicycle)
Man as an active living creature can move in space. Suppose a person can travel 30 km per day on foot and 120 km per day on a bicycle. These are not the maximum values, of course, athletes run up to 100 km and travel up to 1000 km per day.
Let's try to compare a person as an effective system of human movement.
- A car with an internal combustion engine spends an average of 5 liters per 100 km, 1 liter = 10 kWh, which gives 500 Wh per km
- Electric car - 150-200 Wh * per km
- Pedestrian - 2 kW * divided by 10-50 km, 50-200 W * h per km
- Slow / small electric car - 50-100 W * h per km
- Electric bike - 10 W * h / km (average speed 10-15 km / h )
- Cyclist - 2 kWh divided by 100-1000 km, 2-20 Wh * km.
You know more interesting coincidences - write in the comments.
Thanks for attention.