Autonomous building

From Academic Kids

An autonomous building is a building designed to have very little to no networked services. Most modern buildings use electric power, telephone, water, sewerage, storm drain and road services. Functionally, autonomous buildings use native resources to replace all of these except the road and telephone. In addition many consider the use of green building techniques and sustainable trades practices to be central to the idea of an autonomous building, as the materials and skills required to maintain it must also be within the occupant's community or sphere of influence.

Many autonomous buildings are designed as sustainable housing. They aim to provide a comfortable living environment with modern conveniences that are less harmful to the environment than standard housing systems. Autonomous buildings are intended to reduce network costs and transport wastes and distribute their benign environmental impacts more widely and over cityscapes and suburbs, rather than the rural and wild landscapes more usually impacted by industrial resource collection and transportation. Autonomous buildings promise to reduce the impact of centralized industrial solutions. Finally, they are designed to be optimizible to local conditions.

Autonomous buildings have several groups of advocates. Members of the Green movement approve because the buildings usually minimize environmental impact by reducing transportation energy use, networks and associated wastes. Investors sometimes install them to increase profit. Advocates of emergency preparedness also favor them, because they make civil society less fragile. Most real autonomous systems are used in areas far from networked systems. Autonomous buildings can aid self-sufficiency.

The usual argument in favor of autonomous buildings attempts to show that the distribution networks have larger inefficiencies (i.e. a cost of continuing waste) and capital expenses than simply providing the service with the building. The usual counter argument is that those inefficiencies and capital expenses are easily borne in urban concentrations.

Contents

Food

Food production is a part of many autonomous homes, though not of many commercial buildings. Most such enthusiasts desire only the security of potential independence from the world food production network. They usually use high intensity vegetable gardening. A few advanced projects (see below) have included hydroponics and fish farms.

Pebble-bedded container-based hydroponics produces vegetables as intensively as any other method, often with far less work than dirt farming, because weeds are efficiently suppressed, and no bed preparation is required.

Another high-density, low-work approach is forest gardening, in which perennial, compatible edible species are planted in 'canopies': tree, shrub, ground cover, climbing vine, and rhizome (root). The density of food plants is said to be so high that wild plants have trouble invading.

Most food production experiments have used vegetable farming because it can support an adult from as little as 15 m² (160 ft²) of land.

Water

Water is the most important utility, and is fast becoming a scarce resource. There are many methods of collecting and conserving water, and use reduction is usually quite cost-effective.

Greywater systems reuse wash water to flush toilets, and water lawns and gardens. Greywater systems can halve the water use of most residential buildings; however, they require the purchase of a sump, greywater pressurization pump and secondary plumbing. Some builders are installing waterless urinals and even composting toilets that completely eliminate water usage in sewage disposal.

Most desert and temperate climates get at least 250 mm (10 in) of rain per year. This means that a typical one story house with a greywater system can supply its year-round water needs from its roof alone. In the most extremely dry areas, it will require a cistern of 30 m³ (8400 US gallons). Many areas average 13 mm (0.5 in) of rain per week, and these can use a cistern as small as 10 m³. It can be convenient to use the cistern as a heat sink or trap for a heat pump or air conditioning system; however this can make cold drinking water warm, and in drier years the efficiency of the HVAC system may decrease.

Cistern design can reduce costs and inconvenience. Gravity tanks on short towers are reliable, so pump repairs are less urgent. The least expensive bulk cistern is a fenced pond or pool at ground level.

The size and expense of a cistern can be reduced substantially when supplemented with water deliveries. In a drought, monthly deliveries of water are not expensive for a houshold. Fabric water-tanks can be purchased that fit inside the bed of a pick up truck.

In some areas, it is difficult to keep a roof clean enough to assure that the water collection is sanitary for drinking. Commercial reverse osmosis systems provide good quality drinking water, and some people attach devices to remineralize drinking water afterwards, or simply buy bottled water for drinking. Water makers are available for yachts that convert seawater and electricity into potable water and brine.

New technologies, like Reverse Osmosis Water Processors and Vapaires can create unlimited amounts of pure water from polluted water, ocean water, and even from air.

Sewage

Sewage handling is not attractive, but it is essential for public health. Many diseases are transmitted by poorly functioning sewage systems.

The standard system is a tiled leach field combined with a septic tank. The basic idea is to provide small system with primary sewage treatment. Sludge settles to the bottom of the septic tank, is partially reduced by anaerobic digestion, and fluid is dispersed in the leach field. The leach field is usually under a yard growing grass. Septic tanks can operate entirely by gravity, and if well managed, are reasonably safe.

Septic tanks have to be pumped periodically by a "honey wagon" to eliminate non reducing solids. Failure to pump a septic tank can cause overflow that damages the leach field, and contaminates ground water. Septic tanks also require some lifestyle changes, such as not using garbage disposals, minimizing fluids flushed into the tank, and minimizing nondigestible solids flushed into the tank. For example, septic safe toilet paper is recommended.

However, septic tanks remain popular because they permit standard plumbing fixtures, and require few or no lifestyle sacrifices.

Composting or packaging toilets make it economical and sanitary to throw away sewage as part of the normal garbage collection service. They also reduce water use by half, and eliminate the difficulty and expense of septic tanks. However, they require the local landfill to use sanitary practices.

Incinerator systems are quite practical. The ashes are biologically safe, and less than 1/10 the volume of the original waste, but like all incinerator waste, are usually classified as hazardous waste.

State of the art home sewage treatment systems use biological treatment, usually beds of plants and aquaria, that eliminate nutrients and bacteria and convert greywater and sewage to clear water. This odor and color free reclaimed water can be used to flush toilets and water outside plants. When tested, it approaches standards for potable water. In climates that freeze, the plants and aquaria need to be kept in a small greenhouse space. Good systems need about as much care as a large aquarium.

A big disadvantage of living sewage treatment systems is that if the house is empty, the sewage system starves to death.

Storm drains

Paved areas and lawns or turf do not allow much precipitation to filter through the ground to recharge aquifers. This can cause flooding and damage in neighbourhoods, as the water flows over the surface towards a low point.

Typically, elaborate, capital intensive storm sewer networks are engineered to deal with storm water. In some cities, such as much of the old City of Toronto the storm water system is combined with the sanitary sewer system. In the event of heavy precipitation, the load on the sewage treatment plant at the end of the pipe becomes too great to handle and raw sewage is dumped into holding tanks, and sometimes into surface water.

Autonomous buildings can address precipitation in a number of ways:

If a water absorbing swale for each yard is combined with permeable concrete streets, storm drains can be omitted from the neighbourhood. This can save more than $500 per house by eliminating storm drains. One fine way to use the savings is to purchase larger lots, which permits more amenities at the same cost. Permeable concrete is an established product in warm climates, and in development for freezing climates. In freezing climates, eliminating storm drains can often still purchase enough land to construct swales (shallow water collecting ditches) or water impeding berms instead, which still provides more land for homeowners and can offer more interesting topography for landscaping.

A green roof captures precipitation and uses the water to grow plants. It can be built into a new building or used to replace an existing roof.

Electricity

Since electricity is an expensive utility, the first step towards conservation is to design a house and lifestyle to reduced demand. Fluorescent lights, laptop computers and gas-powered refrigerators save both electricity and money.

Using a solar roof, solar cells can currently (2004) provide electric power. Solar roofs are far more cost-effective than retrofitted solar power, because buildings need roofs anyway. Modern solar cells last about 40 years, which makes them a reasonable investment in some areas.

Most areas that lack sun have wind. To generate power, the average autonomous house needs only one small wind turbine, 5 m or less in diameter. On a 30 m tower, this turbine can provide enough power to supplement solar power on cloudy days. Commercially available wind turbines use sealed, one-moving-part AC generators and passive, self-feathering blades for years of operation without service.

The largest advantage of wind power is that larger wind turbines have a lower per-watt cost than solar cells, provided there is wind. However, location is critical. Just as some locations lack sun for solar cells, some locations lack sufficient wind for an economical turbine installation. Paul Gipe (a recognized authority, see below) says that in the Great Plains of the United States a 10 m turbine can supply enough energy to heat and cool a well-built all-electric house.

The advantage of both solar and wind power is that, during times of low demand, excess power can be stored in batteries for future use. However, batteries need to be replaced every few years. In many areas, battery expense can be eliminated by attaching the building to the electric power grid and operating the power system with net metering. Such a building is less autonomous, but more economical and sustainable. Some electrical utilities either pay or give electricity credits to homes that produce energy and put it back into the grid when it's not required for immediate household use. In areas that lack access to the grid, battery size can be reduced by including a generator to recharge the batteries in extended time of low power. Auxiliary generators are usually run from gas, or sometimes diesel. An hour of charging usually provides a day of operation.

Recent advances in passively stable magnetic bearings may someday permit inexpensive storage of power in a flywheel in a vacuum. Well-funded groups like Canada's Ballard Power are also working to develop a "regenerative fuel cell," a device that can generate hydrogen and oxygen when power is available, and combine these efficiently when power is needed.

Heating

Passive solar heating can heat most buildings in even the coldest climates.

Modern krypton- or argon-insulated windows permit otherwise normal looking windows to provide passive solar heat without compromising structural strength. The basic requirement for passive solar heating is that the windows must face the prevailing sunlight (south in the northern hemisphere, north in the southern hemisphere), and the building must incorporate thermal mass to keep it warm in the night.

Earth sheltering and windbreaks can also reduce the absolute amount of heat needed by a building. Several feet below the earth, in most temperate climates the temperature is 13C (55F). Wind breaks reduce the amount of heat carried away from a building.

Rounded, aerodynamic buildings also lose less heat.

If small amounts of gas, heating oil or wood heat are available for the coldest nights, a properly designed slab or basement cistern can inexpensively provide the required thermal mass. In colder climates, construction costs can be as little as 15% more than new, conventional buildings. In warm climates, having less than two weeks of frosty nights per year, there is no cost impact.

A small supplementary heater can substantially reduce the required amount, and expense, of thermal mass. A popular system for ultra-high-efficiency houses is a central hydronic air heater which recirculates hot water from a water heater throughout the house; whether the water heater is gas or electric depends on local prices.

A new system used in some commercial buildings is to provide heating, often water heating, from the output of a gas turbine or stirling electric generator.

Houses designed to cope with interruptions in civil services generally incorporate a wood stove, or heat from diesel fuel or bottled gas, regardless of their other heating mechanisms.

Water heating

Solar water heaters are widely useful because they can save large amounts of fuel. Also, small changes in lifestyle, such as doing laundry, dishes and bathing on sunny days, can greatly increase their efficiency.

The basic trick in a solar water heating system is to use a well-insulated holding tank. Some systems are vacuum insulated, acting something like large thermos bottles. The tank is filled with hot water on sunny days, and made available at all times. Unlike a conventional tank water heater, the tank is filled only when there is sunlight.

Good storage makes a smaller, higher-technology collector feasible. Such collectors can use relatively exotic technologies, such as vacuum insulation, and reflective concentration of sunlight.

Current practical, comfortable water-heating systems combine the solar heating system with a thermostatic gas-powered flow-through heater, so that the temperature of the water is consistent, and the amount is unlimited.

This compromise can easily save 50-75% of the gas otherwise used, and the resulting system is redundantly reliable. If either system fails, the other can continue to provide hot water until the equipment is repaired, fuel or sunlight becomes available, etc.

Cooling

The windows must be shaded in summer. Eaves can be overhung to provide the necessary shade. These also shade the walls of the house, reducing cooling costs.

The basic trick is to cool the building's thermal mass at night, and then cool the building from the thermal mass during the day. It helps to be able to route cold air from a sky facing radiator (perhaps an air heating solar collector with an alternate purpose) or evaporative cooler directly through the thermal mass. On clear nights, even in tropical areas, sky facing radiators can cool below freezing.

Earth sheltering reduces the absolute amount of cooling needed by a building. In temperate climates several feet below the earth the average temperature is 13C (55F).

If a circular building is aerodynamically smooth, and cooler than the ground, it can be passively cooled by the "dome effect." Many installations have reported that a reflective or light colored dome induces a local vertical heat driven vortex that sucks cooler overhead air downward into a dome if the dome is vented properly (a single overhead vent, and peripheral vents). Some persons have reported a temperature differential as high as 15F between the inside of the dome and the outside. Buckminster Fuller discovered this effect with a simple house design adapted from a grain silo, and adapted his Dymaxion house and geodesic domes to use it.

Refrigerators and air conditioners operating from the waste heat of a diesel engine exhaust, heater flue or solar collector are entering use. These use the same principles as a gas refrigerator. Normally, the heat from a flue powers an "absorptive chiller." The cold water or brine from the chiller is used to cool air or a refrigerated space.

Cogeneration is popular in new commercial buildings. In current cogeneration systems small gas turbines or stirling engines powered from natural gas produce electricity and their exhaust drives an absorptive chiller, heats water.

A truck trailer refrigerator operating from the waste heat of a tractor's diesel exhaust was demonstrated by NRG Solutions, Inc. 11385 Shipley Road Johnstown, OH 43031, for EPA contract No. 68D98131. NRG developed a hydronic ammonia gas heat exchanger and vaporizer, the two essential new, not commercially available components of a waste heat driven refrigerator.

A similar scheme (multiphase cooling) can be by a multistage evaporative cooler. The air is passed through a spray of salt solution to dehumidify it, then through a spray of water solution to cool it, then another salt solution to dehumidify it again. The brine has to be regenerated, and that can be done economically with a low temperature solar still. Multiphase evaporative coolers can lower the air's temperature by 50F, and still control humidity. If the brine regenerator uses high heat, they also partially sterilise the air.

If enough electric power is available, cooling can be provided by conventional air conditioning using a heat pump.

Information

Telephone and network service will probably be purchased.

Network service could be provided by a cooperative of neighbors, each operating a router as a household appliance.

Wireless routers operating a radio based protocol such as IEEE 802.11b can commoditize information services into products that can be purchased, and minimize long distance infrastructure, and its costs and vulnerabilities.

Simple simulations show that even quite high density developments can still provide web and email services using open source radio based protocols. This is already being done to some extent (much to the chagrin of some commercial network service providers.)

Satellite internet service also can provide high speed connectivity to remote locations, but as of early 2002, most of these services are limited in which types of network hardware and operating systems they support. They are also not yet on par with the costs of cable modem or DSL service providers.

Other services

Modern office buildings are largely self sufficient in heat, and could be self sufficient in water and sewage. A major bank building (ING's Amsterdam headquarters) in the Netherlands was constructed to be autonomous, and artistic as well.

Food refrigeration, water heating and cooking can be electric, if perfect autonomy is needed. The battery costs are very high.

A small source of auxiliary heat and power permits all the storage systems to be less expensive and provides a backup option (for comfort) when something breaks. Often the water heater will be attached to a central hydronic radiator to provide auxiliary heat. In most areas, bottled gas is convenient for these services, and can provide auxiliary heat, refrigeration and (with a generator) power for exceptional conditions (extended foggy conditions, etc.) A wood stove or an efficient fireplace could provide homey heating in wooded areas.

Some persons concerned about emergency preparedness advocate diesel fuel based systems, because then the building's auxiliary services and vehicles can be operated from a single fuel, usually No. 2 fuel oil. Diesel stoves, heaters, water heaters and generators are commercially available.

Refrigerators and water heaters operating from waste heat may soon be commercially available. A refrigerator similar to a gas refrigerator could theoretically be operated from many sources of waste heat. See the section above, about air cooling.

Financing

If considering a system, run the numbers with real utility prices. Most utilities have prices 5-10% below the amortized price of the mass-produced rural systems they replace (e.g., electricity will be just below the fuel costs and amortization of a generator powered from natural gas). However, many people pay for utilities from after-tax income, so the home-based utilities can be 15-45% more efficient by creating untaxed value. Clever purchasing (e.g. in internet co-ops) can cut capital costs.

Unless the area has local nuclear or hydroelectric power, new construction can often afford to make its own heat and light.

In the coldest areas of the U.S. passive solar heat in new construction costs only 15% more than normal construction. In milder areas, it costs nothing. A passive-solar house usually commands a 15-20% price premium.

In Southern California, new solar roofs already provide cheaper electricity than utilities, because they keep the rain out, and the amortized cost of such electricity is cheaper than the power prices. In most great plains areas, a 10-meter wind turbine on a hundred-foot tower will run an all-electric house, for 10% or less of a new house's cost.

Sewage and water are more marginal. Local health regulations can be problematic, and bulk water and sewage services are usually cheap. Water and sewage systems also have unattractive costs, lifestyle and mechanical reliability issues. Groundwater poisoning, deep green beliefs and high utility prices can motivate installations.

In all rural and most suburban areas buying land for swales instead of digging storm-drains creates a more valuable and more pleasant building.

History

In ancient Roman houses, the center of the rich man's atrium house was a cistern, fed from the roof during rain, and purified by water lilies. Sewage services were the street, obviously unacceptable in a modern city. Heat was by braziers, and a central fire.

Dymaxion house

In the 1950s, Buckminster Fuller's proposed Dymaxion houses adopted many techniques meant to reduce resource use, such as a "fogger" shower head to reduce water use, a packaging toilet, and a vacuum turbine for electric power. While not designed as autonomous per se, Fuller's concern with sustainable design is congruent with the goal of autonomy. None of the Dymaxion house prototypes were ever actually used as a residence.

New Alchemists

In the 1970s, a group of activists and engineers that called themselves the "New Alchemists" believed the warnings of imminent resource depletion and starvation. The New Alchemists were famous for the depth of research effort placed in their projects. Their dedication, and the depth of their work is still impressive.

They designed a series of "bioshelter" projects, the most famous of which was the "Ark Bioshelter" for Prince Edward Island. They published the plans for all of these, with detailed design calculations and blueprints. Later research reports followed up on the results.

The Ark used wind based water pumping and electricity, and was self contained in food production. It had living quarters for people, fish tanks raising Tilapia for protein, a greenhouse watered with fish water and a closed loop sewage reclamation system that recycled human waste into sanitized fertilizer for the fish tanks.

The Ark used quite conventional construction techniques. This may be an advantage, because these techniques are very refined.

As of 2004 the successor organization to the New Alchemists still had a web page up as the Green Center (http://www.fuzzylu.com/greencenter/index.htm). The Ark has been abandoned and partially renovated several times.

Earthships

This is a more recent effort, very similar in intent to the Ark project. All the details are different; in particular, the Earthships (http://www.earthship.org) are clearly a "for profit" effort. The depth of research is harder to evaluate, because most of it is held as proprietary information.

The building material is tires filled with earth. This makes a wall that has large amounts of thermal mass (see earth sheltering). Berms are placed on exposed surfaces to further increase the house's temperature stability.

The water system starts with rain water, processed for drinking, then washing, then plant watering, then toilet flushing, and finally black water is recycled again for more plant watering. The cisterns are placed and used as thermal masses.

Power, including electricity, heat and water heating, is from solar power.

The emphasis on gardening is to provide some degree of autonomy in food.

Bottled propane is used to round out energy needs. This is a sensible choice because it is clean, and saves a lot of construction that would otherwise be needed to chase diminishing returns in electricity and heating.

References and resources

  • "Natural Capitalism" by Amory Lovins and the Rocky Mountain Institute. The section about the banana plant in the Rocky Mountains is especially amusing.
  • Also see "A Fuller Explanation" by Amy Edmondson, one of B. Fuller's later adjutants
  • The Buckminster Fuller Institute (http://www.bfi.org) is still in existence. B. Fuller left thousands of pages of notes to the university where he last taught.
  • There is a section on Autonomous Houses (http://reality.sculptors.com/cgi-bin/wiki?Autonomous_Houses) in the Reality Sculptors (http://reality.sculptors.com/cgi-bin/wiki) wiki, including links to a mailing list which frequently discusses autonomous design considerations.
  • Designs for a geodesic dome version of an Autonomous House can be found at http://reality.sculptors.com/~salsbury/House/
  • "Wind Power for Home and Business" by Paul Gipe

See also

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