It's 2030 and the 14,000 residents of the first carbon neutral neighbourhood in the Netherlands gather at the communal fires, where they cook and eat together.
Lees dit artikel in het Nederlands. Collages by Golnar Abbasi & Arvand Pourabbasi.
Cooking Without Fossil Fuels
Energy use is power use multiplied by time. A refrigerator has relatively low power use but high energy use, because it's used for 24 hours per day. If a refrigerator needs 100 watts of power, its energy use per day is 2,400 watt-hours. For a cooking stove, it's the other way around. It's only used for one or two hours per day, but cooking a meal requires 2,000 to 3,000 watts of power, depending on how many heating elements are used and at what temperature.
Although the daily energy use of refrigerator and cooking stove can be similar, it's much more challenging to power the cooking stove with renewable energy, for example by using solar panels. To provide 3,000 watts of power requires a solar array of at least 12 solar panels of 250 watt each. The refrigerator only needs five of these solar panels, because its energy use is spread out over a longer time period.
Cooking also needs a reliable energy source, which is not dependent on the weather. Human power is reliable, but it's not an attractive option either. Operating an electric cooking stove to feed one household would require at least 20 people exercising simultaneously.
The Communal Fire
Confronted with these challenges, the neighbourhood decided to revert to the oldest renewable source of thermal energy: biomass. If the old-fashioned windmill is the predecessor of today's wind turbines, the biomass fire is the predecessor of today's solar panels. Like solar panels, trees and other plants convert sunlight into a useful source of energy for humans. Throughout history, the burning of wood and other biomass provided households with a reliable energy source that could produce the high temperature heat for cooking.
To decrease the energy use of the cooking process, the residents decided to demolish kitchens in individual living spaces, and to build communal kitchens on the main squares instead. Communal cooking is more fuel efficient than individual household cooking: the energy use per portion decreases with the number of portions cooked. Scientific research about the energy use in very large kitchens does not seem to exist, but cooking for groups of up to 25 people has proven to be four to five times more energy efficient compared to cooking for one, and twice as efficient compared to cooking for four.
The communal fires burn three times per day: for breakfast, lunch, and dinner. On the ground floor, stokers add wood to the fire, while human powered bellows rekindle the fire and increase its temperature if necessary. Food preparation -- baking bread, cooking dishes, roasting and grilling food -- happens on the higher floors. High in the chimney of the ovens, meat and fish are preserved in the smoke of the fire.
The floors are connected by stairs and the outside of each oven is equipped with a human powered crane -- used for raising and lowering ingredients, prepared foods, or dirty dishes. Food and firewood are grown and harvested in the former neighbourhood park.
The Versatility of Fire
If these days a fire is considered to be inefficient, it's because we only measure the efficiency of one of its functions (usually space heating). However, fire is extremely versatile and our ancestors used it not only for cooking and space heating. At the same time, it offered them light, it preserved their food, it produced hot water, it dried clothes, and it kept insect and predators away.
The versatility of the fire is fully utilized on the squares in the neighbourhood. Whenever the cooking fire burns, it also heats the water for the bathing house, which is built right next to the oven and receives hot water from heat-exchanging pipes that pass through the hot chamber of the oven. The hot water is also used for the washing of clothes and for doing the dishes, while the heat that radiates from the outer surface of the oven is used to dry cloths. When the cooking is done, residents collect glowing coals that can be used for personal heating systems at home.
The communal fire brings more energy savings than one might think. Unlike modern alternatives, it needs no central infrastructure to make it work, and it can be built locally from readily available materials. Furthermore, there's no need for a whole catalog of electric appliances, such as ovens and cooking hobs, microwave ovens, toasters, hot water kettles, tumble dryers, hot water boilers and heating systems. It takes a lot of energy to manufacture all these items for individual households -- an energy cost that the neighbourhood has eliminated.
Next episode: firewood and food production.