○Residential Basic Materials
Many Japanese homes lack insulation, causing heat to escape during winter despite continuous heating efforts and leading to condensation on windows. Continuing heating in this state becomes an unnecessary waste of electricity. To combat this, insulation materials are used to prevent heat from escaping. Additionally, incorporating double-glazed windows and 24-hour mechanical ventilation allows for the use of heating and cooling systems year-round while minimizing electricity consumption.
Concrete used in buildings, apartments, and homes emits a large amount of carbon dioxide during its production process, significantly contributing to global warming, thus necessitating a reduction in its usage.
Considering these issues, including poverty, the inability to live in adequate housing, and refugee problems that need immediate attention, if we think about sustainable housing that can be built starting now and globally, the basic materials would be fast-growing kiri (Paulownia), bamboo, straw, earth, clay, stone, lime, and water.
Straw is dried stems of plants like rice and wheat. Rice is cultivated across Asia, from Japan to India, while wheat is grown worldwide in Africa, Europe, Asia, Russia, Australia, Canada, Argentina, among other regions. Consequently, straw is widely available, and it's bundled into blocks approximately 50cm wide to serve as insulation. These blocks are stacked between the columns of a dwelling. The interior and exterior of these straw walls are covered with mud to create earthen walls. Such houses are known as "straw bale houses," and bales are created using an agricultural machine called a baler, which compresses dried grass or straw into block shapes.
The pillars use fast-growing kiri (Paulownia). This type of kiri grows faster than the common variety, reaching a height of 15 meters and a diameter of about 40 cm in five years. It is strong enough to be used for pillars and furniture. Once planted, new shoots will sprout after harvesting, allowing it to be harvested every five years, a process that can continue for 30 to 40 years. It can be cultivated in any warm climate with soil that is not too acidic or alkaline.
Additionally, methods of construction such as "cob" and "adobe" involve mixing water with materials like sand, clay, and straw to create earth or brick walls. These architectural methods have been observed across various continents since ancient times. Adding fibrous materials like straw helps elongate and bind the soil, increasing the tensile strength of cob.
As these earth walls are susceptible to weakening when exposed to the elements, they are further coated with materials like lime plaster mixed with oil on the exterior to enhance waterproofing and durability.
While straw bale walls are approximately 50cm thick and cob walls around 60cm thick, a method seen in traditional Japanese homes involves applying soil to bamboo lattices for thinner internal walls.
The following values represent thermal conductivity, where lower numbers indicate higher insulation performance. Straw has a high insulation performance.
- Glass wool: about 0.016 W/(m·K)
- Straw: approximately 0.05 - 0.09 W/(m·K)
- Earth walls: approximately 0.5 - 0.8 W/(m·K)
- Natural wood: about 0.1 - 0.2 W/(m·K)
- Concrete: roughly 1.7 - 2.3 W/(m·K)
In addition to straw, grasses such as cogongrass and hay can also be used. The thermal conductivity of cogongrass is 0.041 W/(m K), while that of hay from lawn grass is 0.037 W/(m K). There are various types of grasses, including cogongrass, sedge, miscanthus, reed, kariyasu, karkaya, and shimakaya, known in Japan for their use in thatched roofs.
In other words, straw is a resource that can be harvested annually worldwide, and as long as municipalities manage the amount of material they use, they will not face resource depletion. However, since it takes hundreds of years for soil to form, fast-growing kiri and straw, which can be harvested multiple times in a short period, make straw bale houses, which use less soil, a higher priority than cob houses.
Bamboo primarily thrives in warm, humid regions such as Eastern and Southern Asia, Africa, and countries near the equator in South America. In places where bamboo isn't prevalent, wood becomes the alternative, with local authorities making decisions while monitoring the quantity of trees. If the use of straw bale houses exhausts the wood resources needed for residential construction, cob houses become a viable alternative.
These dwellings employ reusable materials, emphasizing long-term use through repeated repairs and natural disposability post-use. Straw bale, cob, and adobe constructions are ancient techniques found across continents and are highly adaptable as fundamental sustainable housing methods worldwide.
In regions with high rainfall and humidity, like Japan, preventing straw decay due to mold becomes necessary. Considerations include:
- Employing roofs that effectively manage rainwater and ensuring the overhangs and window sills are of adequate length to protect walls from rainwater.
- Elevating the house's foundation to shield walls from splashing rainwater.
- Preventing moisture from the ground from entering the walls.
- Implementing ventilated exterior walls to release and dry moisture between the exterior wall material and insulation, preventing condensation.
Additionally, prioritizing stone-based construction directly on foundation stones (known as "ishibadate") over concrete foundations is preferred. This choice aims to reduce concrete usage and deflect seismic forces. With a concrete foundation, seismic tremors directly affect the residence. In contrast, in stone-based construction, columns rest on foundation stones, allowing them to slide on the stone's surface, reducing tremors. However, stone-based construction may not be universally applicable, so while it remains a primary choice, assessing concrete foundations or other methods on a case-by-case basis is crucial.
Moreover, setting these foundations at a height that prevents rainwater from splashing onto the earth walls from the ground is essential.
○Electricity Generation and Storage
Power generation and storage should be sustainable and simple in structure. Prout Village prioritizes the following combination of power equipment.
The primary power source is a magnesium battery developed by Professor Yabe Takashi of Tokyo Tech. This battery uses thin magnesium plates, which can be stored and carried. By immersing carbon-based material on the positive side in saltwater and using magnesium on the negative side, electricity is generated. This has over 8.5 times the energy density of lithium-ion batteries and is safer than hydrogen fuel, with less risk of ignition.
Magnesium is abundant, with approximately 1800 trillion tons in seawater, equivalent to 100,000 years' worth of the annual 10 billion tons of oil used. The risk of depletion is very low, and it can be used globally. The magnesium oxide left after use can be reheated to over 1000°C and reused as a magnesium battery. Professor Yabe also developed a device that gathers sunlight with mirrors and converts it into laser light to reuse magnesium by separating oxygen from magnesium oxide, as well as a desalination device that extracts magnesium and salt from seawater.
The experimental magnesium battery is 16.3cm wide, 23.7cm deep, 9.7cm high, and weighs about 2kg after water is added, with a maximum output of 250W, enough to power a 450L refrigerator for an hour. Connecting 5 or 10 of these batteries can power larger devices. A car equipped with a 16kg magnesium battery can travel 500km.
During desalination, salt and bittern (magnesium chloride) remain, which, when exposed to laser light, produces magnesium. Magnesium is also abundant in desert sand. 10 tons of seawater yield 13kg of magnesium, equivalent to a month's electricity for a standard household. By making magnesium batteries a foundation of life, magnesium batteries can be created from seawater worldwide, reducing the risk of depletion, enabling storage and transport, and allowing electricity use even in remote areas with poor conditions.
This desalination device that produces magnesium requires electricity. Therefore, small hydropower plants will be set up in rivers and streams worldwide. The power generated depends on the drop and water flow. In Japan's Itoshirobanba Seiryu power station, one turbine generates 125kW for about 150 households with a 111m drop.
In addition to small hydropower, tidal power from oceans and rivers will also be used. Tidal power provides stable electricity day and night, and its simple structure requires no large facilities.
Adding small to medium-scale wind power generation to these, the power output increases when the wind blows. Various types of wind power generation have been developed, and vertical axis wind turbines can rotate horizontally, allowing them to capture wind from all directions. In Prout Village, the priority is to create small to medium-scale energy facilities distributed across municipalities so that each can manufacture and manage them, making large-scale wind power generation not a top priority.
The magnesium batteries, small hydropower, tidal power, and wind power mentioned so far do not emit carbon dioxide during power generation, contributing to global warming countermeasures and becoming stable and sustainable power generation methods. Additionally, other energy sources are used simultaneously to aim for diversification of natural energy.
One such method uses vacuum tube solar water heaters to produce hot water from solar heat for baths and kitchens. This device integrates a heat collector that gathers the sun's heat and a water storage unit. In Japan, temperatures reach 60-90°C in summer and around 40°C in winter. The use of solar heat collection panels is also considered. Heated air inside the panel, around 50°C, travels through ducts to warm the entire house.
Since these devices use solar heat, the installation direction and angle of the water heater and heat collection panel are important. In Japan, true south is most effective, achieving 100% efficiency, while true east and west achieve around 80%. The ideal roof angle is 20-30 degrees. These devices can be placed on roofs or the ground. If placed on roofs, the roof shape will need to accommodate the collector surface, increasing the heat collection area. These solar water heaters and solar heat collection panels use heat directly, making their structure simple.
For lighting in areas without power lines, plant power generation or ultra-small hydropower are considered. Plant power generation uses two electrodes inserted into the ground to obtain weak power. However, this power is minimal, with around 1.5 volts per unit. An experiment successfully connected 100 units to exceed 100 volts of household power. The first choice for electrodes was magnesium and binchotan charcoal, avoiding the use of rare metals or buried resources.
Additionally, a portable ultra-small hydropower generator, one meter long, has been developed. It can generate power in a stream with a one-meter height difference, producing 5W with a flow rate of 10 liters per second.
In Finland, sand batteries are also in use. These store electricity generated from solar and wind power as heat in sand. The insulated tank is 4 meters wide and 7 meters high, containing 100 tons of sand. This heat is supplied to the surrounding area for building heating and warm swimming pools. Sand heated to over 500°C can store energy for several months. The lifespan is several decades. Any dry sand without flammable waste can be used, making this feasible in Japan.
In Finland, it is calculated that to supply heat to a district of 35,000 people, a storage tank 25 meters high and 40 meters in diameter filled with sand would be required. The sand battery's structure is simple, consisting of pipes, valves, fans, and electric heating elements, and the construction costs are low.
In the United States, sand batteries are also being developed. In this case, silica sand is heated to 1200°C and stored in an insulated concrete storage facility. When converting this heat into electricity, water is heated to produce steam, which turns a turbine with many blades. This turbine is connected to a generator, which produces electricity. When generating electricity from heat, this equipment is necessary.
These are the methods of power generation and storage in Prout Village. Next, I will look at existing power generation methods and the reasons for not using them.
One of these is hydrogen. While hydrogen does not emit carbon dioxide when used as fuel, it is released during the production process. For example, producing hydrogen from fossil fuels like natural gas, oil, and coal emits large amounts of carbon dioxide and will eventually lead to resource depletion, making it an unsuitable option.
There is also a method of obtaining hydrogen by electrolyzing water using electricity from natural energy sources like solar and wind power. Although this method has low carbon dioxide emissions, it requires a large amount of water, which could exacerbate water shortages already accelerated by global warming.
Furthermore, water electrolysis uses rare metals like iridium. If the current rate of use continues, it is predicted that the usage will exceed twice the reserves by 2050, making it an unsustainable option.
Additionally, there are methods to produce gas, electricity, and hydrogen from biomass power generation. Biomass includes human and livestock waste, agricultural residues like straw and rice husks, food scraps, and wood. For example, in a household biogas toilet, cow dung is added. Cow dung contains methane-producing bacteria, and when human waste, food, and weeds are added, these bacteria ferment them, producing biogas. The main components of this gas are 60% methane and 40% carbon dioxide. Methane gas is a major cause of global warming, making its widespread use difficult globally.
Storing hydrogen involves high-pressure compression, liquid hydrogen cooled to minus 253°C, and hydrogen storage alloys, which require additional equipment for transport. In this case, the equipment becomes large-scale and complex, making it unsuitable.
Furthermore, solar panels used in solar power generation contain harmful substances and must be disposed of by burying them underground, making this an unsustainable method.
Geothermal power generation is excluded due to the long time required for exploration, drilling, and pipeline construction, as well as the limited locations where it can be used.
Nuclear power plants are excluded because they can lead to catastrophic disasters, and their fuel, uranium, is finite and will eventually deplete. Thermal power generation is also excluded as fossil fuels will eventually run out, and it emits large amounts of carbon dioxide.
Additionally, lithium batteries used in electric vehicles, electric bicycles, and smartphones are unsustainable as they use buried resources like lithium and cobalt, so they will also not be used.
To summarize, magnesium batteries, small-scale hydroelectric power, tidal power, and small to medium-sized wind power will be the main sources of energy, with solar thermal water heaters, solar thermal panels, plant-based power generation, ultra-small hydroelectric power, and sand batteries being considered according to the situation.
In this way, electricity will be generated from the sea, rivers, and land as much as possible and shared. By adding insulation to homes, energy consumption will also be reduced. In this manner, life will be sustained solely by natural energy without the use of depletable resources. In a monetary society, economic activities are carried out, consuming enormous amounts of electricity daily due to competition. When these economic activities are eliminated, the required amount of electricity is drastically reduced, significantly lowering carbon dioxide emissions, and providing a powerful countermeasure against global warming.
○Household Drainage
To construct a self-sufficient residence in harmony with nature, addressing household drainage concerns is crucial. The primary sources of household drainage include the washing machine, kitchen, bathroom sink, bath, and toilet. Initially, drainage is fundamentally managed through a natural infiltration system, allowing wastewater to percolate into the ground from a pit dug near the residence. In simple terms, this involves laying gravel or sand in the pit, allowing the wastewater to seep into the ground.
Clay pipes (ceramic pipes) are used for drainage. These pipes are crafted by firing clay at temperatures exceeding 1000°C. They possess excellent strength, corrosion resistance, chemical resistance, and have a long functional lifespan, making them materials that can naturally return to the environment.
Using eco-friendly detergents, soaps, and toothpaste is imperative. Soaps and shampoos made from essential oils avoid the use of petroleum-based ingredients or chemicals, ensuring complete decomposition of residues post-drainage. Additionally, ethanol-based disinfectants are viable options. They contain antibacterial elements that help control the proliferation of surface bacteria on the skin. Ethanol is a natural resource made from plants like sugarcane and can be directly reintegrated into the ground while being cultivable as part of a planned approach. Water hotter than 70°C can be used for dishes and clothing. Hot water has properties for sterilization and grease removal, effectively eliminating both dirt and odor. Subsequently, natural-based detergents can be used.
Regarding toothpaste, commercially available ones primarily comprise chemical substances that do not completely decompose; therefore, these should not be used. Consideration should be given to using substances like xylitol and fluoride in toothpaste. Additionally, brushing with a toothbrush and using dental floss is recommended. Toothbrushes alone clean only about 50% of the teeth, and dental floss is used to clean food particles and dirt between teeth by passing through them. At the very least, performing these two actions after every meal is essential; otherwise, many individuals are prone to cavities.
In this way, refraining from using any chemical substances and allowing wastewater to infiltrate into the ground prevents soil contamination.
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