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Autonomous building

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An autonomous building is a building designed to be operated independently from infrastructural support services such as the electric power grid, municipal water systems, sewage treatment systems, storm drains, communication services, and in some cases public roads.

Advocates of autonomous building describe advantages that include reduced environmental impacts, increased security, and cost efficiencies. Some cited advantages satisfy tenets of green building, not independence per se (see below). Off-grid buildings often rely very little on civil services and are therefore safer and more comfortable during civil disaster or military attacks. (Off-grid buildings would not lose power or water if public supplies were compromised for some reason.)

Most of the research and published articles concerning autonomous building focus on residential homes. In the 1990s architects such as William McDonough and Ken Yeang applied environmentally responsible building design to large commercial buildings, such as office buildings, making them largely self-sufficient in energy production. One major bank building (ING's Amsterdam headquarters) in the Netherlands was constructed to be autonomous and artistic as well.

British architects Brenda and Robert Vale have said that, as of 2002, "It is quite possible in all parts of Australia to construct a 'house with no bills', which would be comfortable without heating and cooling, which would make its own electricity, collect its own water and deal with its own waste...These houses can be built now, using off-the-shelf techniques. It is possible to build a "house with no bills" for the same price as a conventional house, but it would be (25%) smaller."

Theory

As an architect or engineer becomes more concerned with the disadvantages of transportation networks, and dependence on distant resources, their designs tend to include more autonomous elements. The historic path to autonomy was a concern for secure sources of heat, power, water and food. A nearly parallel path toward autonomy has been to start with a concern for environmental impacts, which cause disadvantages.

Autonomous buildings can increase security and reduce environmental impacts by using on-site resources (such as sunlight and rain) that would otherwise be wasted. Autonomy often dramatically reduces the costs and impacts of networks that serve the building, because autonomy short-circuits the multiplying inefficiencies of collecting and transporting resources. Other impacted resources, such as oil reserves and the retention of the local watershed, can often be cheaply conserved by thoughtful designs.

Autonomous buildings are usually energy-efficient in operation, and therefore cost-efficient, for the obvious reason that smaller energy needs are easier to satisfy off-grid. But they may substitute energy production or other techniques to avoid diminishing returns in extreme conservation.

An autonomous structure is not always environmentally friendly. The goal of independence from support systems is associated with, but not identical to, other goals of environmentally responsible green building. However, autonomous buildings also usually include some degree of sustainability through the use of renewable resources, producing no more greenhouse gases than they consume, and other measures.

History

Autonomous building is an idea of western civilization in the 20th century. Inhabitants of cabins, huts and yurts through most of history were off-grid whether they liked it or not.

In the 1930s through the 1950s, Buckminster Fuller's three prototype Dymaxion houses adopted many techniques 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 and efficient design is congruent with the goal of autonomy, and showed that it was theoretically possible. One of the three prototype Dymaxion houses that Fuller produced was made part of the conventional Graham family residence in Wichita, Kansas, and has now been reconstructed at the Henry Ford Museum.

In the 1970s, a group of activists and engineers calling 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. Using conventional construction techniques, they designed a series of "bioshelter" projects, the most famous of which was the Ark Bioshelter community for Prince Edward Island. They published the plans for all of these, with detailed design calculations and blueprints. 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. As of 2004, the successor organization to the New Alchemists still had a web page up as the Green Center. The PEI Ark has been abandoned and partially renovated several times.

The 1990s saw the development of Earthships, similar in intent to the Ark project, but organized as a for-profit venture, with construction details kept 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.

Practicality

First and fundamentally, independence is a matter of degree. Complete independence is very hard or impossible to attain. For example, eliminating dependence on the electrical grid is one thing, and growing all of your own food is a more demanding and time-consuming proposition.

Living in an autonomous shelter can require one to make sacrifices in one's lifestyle choices, personal behavior, and social expectations. Even the most comfortable and technologically advanced autonomous houses may require some differences in behavior. Some persons adjust easily. Others describe the experience as inconvenient, irritating, isolating, or even as an unwanted full-time job. A well-designed building can reduce this issue, but usually at the expense of reduced autonomy.

An autonomous house must be custom-built (or extensively retrofitted) to suit the climate and location. Passive solar techniques, alternative toilet and sewage systems, thermal massing designs, basement battery systems, efficient windowing, and the array of other design tactics require some degree of non-standard construction, added expense, ongoing experimentation and maintenance, and also have an effect on the psychology of the space.

The Vales, among others, have shown that living off-grid can be a practical, logical lifestyle choice—under certain conditions.

Maintenance systems

This section includes some minimal descriptions of methods, to give some feel for such a building's practicality, provide indexes to further information, and give a sense of modern trends.

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.

The classic solution with minimal life-style changes is a proven well. However drilling a well is an uncertain activity, and can be expensive. Well water can be contaminated in some areas, and is depleted in others. Also, once drilled, a well-foot requires substantial power. However, advanced well-foots can reduce power usage by two-fold or more from older models.

It is often more economical to design a building to use rain, with supplementary water deliveries in a drought.

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. Many autonomous homes can reduce water use below ten gallons per person per day. In a drought, water can be delivered to the house inexpensively via truck. Self delivery is possible by installing fabric water-tanks that can 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.

New technologies, like reverse osmosis water processors and Aquosus, can create unlimited amounts of pure water from polluted water, ocean water, and even from humid air. Water makers are available for yachts that convert seawater and electricity into potable water and brine.

Sewerage

Sewerage as a resource

The approaches above treat human excrement as a waste rather than a resource. Humanure is composted human excrement, and can return nutrients to a garden. Recycling human excrement requires minimal life-style changes.

In the case of composting toilets, units of varying size can be used to naturally decompose human faeces into a highly useful odourless and safe compost, though pending future research it is suggested that "humanure" be used only for growing food that does not grow directly in the compost eg tomatoes (See Humanure by the great Joseph Jenkins).

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.

NASA's bioreactor is an extremely advanced biological sewage system. It can turn sewage into air and water through microbial action. NASA plans to use it in the manned Mars mission.

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

Another method is NASA's urine-to-water distillation system.

Sewerage as a waste

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 a 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 may 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.

Some of the oldest pre-system sewage types are pit toilets, latrines, and outhouses. These are still used in many developing countries.

Storm drains

Drainage systems are a crucial compromise between human habitability and a secure, sustainable watershed. Paved areas and lawns or turf do not allow much precipitation to filter through the ground to recharge aquifers. They 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 stormwater. In some cities, such as the Victorian era London sewers or 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 (1995) by eliminating storm drains. One 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, the elimination of storm drains can often still pay for enough land to construct swales (shallow water collecting ditches) or water impeding berms instead. This plan 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 reduce demand. Fluorescent lights, laptop computers and gas-powered refrigerators save both electricity and money. There are also superefficient electric refrigerators, such as those produced by the SunFrost company, which use 85% less energy than normal. Using a solar roof, solar cells can 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.

A number of areas that lack sun have wind. To generate power, the average autonomous house needs only one small wind generator, 5 m or less in diameter. On a 30 m high 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. Economic use in other areas requires research, and possibly a site-survey.

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 with fewer lifestyle sacrifices. 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. The grid's cost and impacts can be reduced by using single wire earth return systems.

In areas that lack access to the grid, battery size can be reduced by including a generator to recharge the batteries during extended fogs or other low-power conditions. 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 Systems 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.

Earth batteries tap into the electric currents inside the earth called telluric current. They can be installed anywhere in the ground, but provide low levels of voltage and amperages (depending on the configuration). They were used to power telegraphs in the 19th century. Earth batteries may be used again in the future, if electric appliances become efficient enough that they require only low levels of electricity to function.

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, temperature ranges from 4°C (40 °F) in North Dakota to 26 °C (80 °F)[1], in Southern Florida. 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, those 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, and also reduce lifestyle impacts with a small reduction of autonomy. A popular system for ultra-high-efficiency houses is a central hydronic (radiator) air heater with water recirculating from the water heater.

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. [2]

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.

Electric heaters and electric stoves provide pollution-free heat, but they consume large amounts of electricity. If enough electricity is provided by solar panels, wind turbines, or other means, then electric heaters and stoves become a practical option.

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 again reduces life-style impacts at some cost in autonomy.

However, this compromise can still 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.

But can any building that uses fossil fuel be called "autonomous?" Natural gas can be replaced by methane digesters, fueled by composting human excrement and kitchen scraps, or a biodiesel "co-gen" can produce both electricity and hot water from oilseed crops grown on-site.

Cooling

Earth sheltering or annualized passive solar systems substantially reduce the cooling needed by a building. In temperate climates several feet below the earth the average temperature ranges from 4 °C (40 °F) in North Dakota to 26 °C (80 °F), in Southern Florida. Annualized passive solar buildings often have buried, sloped water-tight skirts of insulation that extend 6 m (20 ft) from the foundations, to prevent heat leakage between the earth used as thermal mass, and the surface.

Less dramatic improvements are possible. Windows can be shaded in summer. Eaves can be overhung to provide the necessary shade. These also shade the walls of the house, reducing cooling costs.

Another 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.

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 15 °F (8 °C) 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. 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.

Food

Food production has often been included in historic autonomous projects to provide security. Skilled, intensive gardening can support an adult from as little as 15 square meters of land. Some proven intensive, low-effort food-production systems include hydroponics, and forest gardening.

Communication

Telephone and network service will probably be purchased.

A increasing number of activists provide free or very inexpensive web and email services using cooperative computer networks that run wireless ad hoc networks. Network service is provided by a cooperative of neighbors, each operating a router as a household appliance. These minimize wired infrastructure, and its costs and vulnerabilities.

Rural electrical grids can be wired with "optical phase cable", in which one or more of the steel armor wires are replaced with steel tubes containing fiber optics. [3]

Satellite internet service also can provide high speed connectivity to remote locations, but as of 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.

Financing

If considering a system for the economics, 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 even the simplest 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 and is therefore a great bargain. A passive-solar house usually commands a 15-20% price premium.

In Southern California, new solar roofs already provide cheaper electricity than utilities, and the amortized cost of such electricity is cheaper than the utility prices. In most great plains areas, a 10-meter wind turbine on a hundred-foot (30 m) 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.

See also

Template:Energy Sustainability Template:Sustainability and energy development group

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