The lower floors of the human powered student building are reserved for communal energy production. How long the students need to exercise on these floors depends on their demand for power. Because the energy users are also the energy producers, there’s a strong incentive to reduce energy demand.

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For each energy using activity, we calculated the amount of student-hours that's required to produce the energy. We assume that every student can produce 100 watt-hour (Wh) of power per hour.

If an activity (such as refrigeration) requires 40 kilowatt-hours (kWh) per day, this corresponds to 400 student-hours of power production per day, or one hundred people exercising for four hours.

We can then calculate the total amount of hours per day that each student needs to produce power for the community. We also take into account 50% energy losses.

**How Many Hours per Day?**

The communal power producing floors supply energy for fridges, hot showers, toilets, dishwasher, hair dryers, communal lighting and electricity, water pumps, and Internet.

The working schedules are negotiated and set up by the students themselves, who are in total control of their human powered community. For now, we calculated three different scenario's, based on three hypothetical levels of energy demand.

The most energy efficient scenario requires each student to produce power for 1.5 hour per day. In this scenario, the showers are cold, there are no hair dryers, the dishes are done by hand with cold water, and the clothes are drying outside in the rain.

A second scenario adds a 1-minute hot shower every day, as well as limited hair drying. This doubles the daily work duty to 3 hours per student per day. The third scenario doubles the hot shower length to 2 minutes per day, and introduces a dishwasher and (limited) clothes drying. It requires every student to produce power for 6 hours per per day.

**How Many People?**

Energy demand varies throughout the day and the night. To avoid night shifts and to spread out the workforce more evenly over time, the human powered student building is equipped with a gravity battery in one of the former elevator shafts.

Assuming 10 hours of continuous energy production per day, how many people would be producing power simultaneously? In the most energy conscious scenario, the answer is 110 people. That's roughly 1 in 7 students.

In the moderate scenario, it's 220 people (more than 1 in 4 students) and in the 'energy-intensive' scenario, it's 440 people (more than 1 in 2 students). The last scenario surpasses the maximum power capacity of the human power plant, which is 400 people producing power simultaneously.

Communal energy use in the student building is 112 kWh per day in the first scenario (150 watt-hour per person per day), 224 kWh in the second scenario (300 Wh per person per day), and 448 kWh in the third scenario (450 Wh per person per day).

**Other Duties**

Note that this only concerns the communal energy use of the building. Students also need to produce energy in their own rooms. In this case, timing and duration are entirely up to the student, not to the community as a whole.

We have estimated a maximum of 1-2 hours of personal power production per day (100-200 Wh), which is sufficient for lighting, computing and music if energy efficient devices are used.

Communal and private work duties combined are thus 2,5 to 3,5 hours per day in the first scenario, 4-5 hours per day in the second scenario, and 7-8 hours per day in the third scenario.

Furthermore, there are work duties for clothes washing, biogas plant operation, and kitchen work. Clothes washing is estimated to be 1 to 2 hours per student per week, and is not powered by communal energy production.

There is a two-weekly work shift for shopping, cooking and dish washing (if this happens by hand). Finally, once per month, every student needs to work an 8-hour shift in the biogas power plant.

**Detailed Calculations**

[1] Energy Losses

We assume that half of the energy produced is lost in the process. There are energy losses in the exercise machines, the distribution of energy, and the conversion between different forms of energy. These energy losses are included in the figures below.

[2] Refrigeration

The refrigerators need to be operated day and night and use roughly 40 kWh of electricity per day. It would take 17 students exercising around the clock to power them. Required: 408 student-hours, or 60 min per student per day.

[3] Showering

To provide each student with a 3-minute hot shower per 3 days (or a 1-minute hot shower per day), we need 125 students exercising 8 hours per day, or a total of 400 student-hours (or 60 min per student per day).

[4] Toilet Flushing

Shared toilet facilities are distributed throughout the building. A vacuum toilet requires very little water but it needs roughly 2 watt-hour of energy per flush.

Assuming 5 flushes per day per person, this comes down to 10 watt-hour per person per day, or 7,5 kWh per day for 750 students. This means we need 7.5 people exercising for 10 hours to power the toilet flushing system, or 75 student-hours (12 min per student per day).

[5] Water Pumping

Assuming a water use of only 50 litres per person per day -- less than half of the average -- it would require around 3.6 kWh per day to pump this water to the higher floors of the building. This comes down to 36 student-hours per day, or 6 minutes per student per day.

[6] Internet

A Wifi-router on every floor of the building would require 5.2 kWh per day, or 52 student-hours per day (24 hour internet). This comes down to 8 minutes per student per day.

[7] Lighting in the Communal Rooms

All floors of the human powered student community have communal spaces where students can come together. These spaces need lighting and possibly energy for other devices, such as computers.

When they are in their room, students need to power their computers themselves. When they are in a communal space, the energy is taken from the communal power producing floors.

It's hard to predict how this dynamic will play out, for now we estimate a need for 100 student-hours, less than 20 minutes of power production per student per day. More energy use in communal spaces would raise the communal working duty and decrease the individual efforts.

[8] Dish washing

An industrial dishwasher machine, used twice per day, requires a total of 360 student-hours (50 min per student per day). Most energy used is for heating the water.

[8] Hair Dryers

Ten students can power roughly 10 hair dryers during the showering period. Four hours of hair drying then requires 40 student-hours or 6 minutes per student per day.

[9] Cooling of Power Producing Students

Overheating is a serious risk for power producing people. Using fans, it takes 10 watts of energy to cool one student. Assuming an average amount of 250 energy generating students, an additional 25 students would be needed to cool them in summer, while these 25 students would need another 2 to 3 students to do the same to them.

However, to keep energy use in check, cooling is limited to 200 student-hours. During very hot days, we lower energy demand and have a siesta.

Wow, amazing! So, basically some 20-40 hours a week are occupied by communal duties alone, of them the most productive hours of the day. I have a vague feeling something's missing here. As far as I remember, students were also supposed to study at the university. Or not any more?

Posted by: Nikolay Ivankov | 16 January 2018 at 12:21 PM