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The domestic water can be heated using either the same heating system (ie gas or firewood can also be used to heat the domestic water, by using a heat exchanger). In addition, [[Solar hot water|solar water heating]] can be incorporated (often as a ''additional'' technology).   
The domestic water can be heated using either the same heating system (ie gas or firewood can also be used to heat the domestic water, by using a heat exchanger). In addition, [[Solar hot water|solar water heating]] can be incorporated (often as a ''additional'' technology).   
Some authorities advocate that [[bottled gas]] or [[natural gas]] be replaced by [[biogas]]. However, this is usually impractical unless live-stock are on-site.  The wastes of a single family are usually insufficient to produce enough [[methane]] for anything more than small amounts of cooking.





Revision as of 11:43, 8 October 2012

An autonomous house or off-the-grid (OTG) house is a family house designed to be operated independently from infrastructural support services such as the water supply system, sewage/excreta disposal system, centralised food production system, mains electricity grid, gas grid, and in some cases, storm drains, mains electricity grid-connected communication services and public roads.

An autonomous neighbourhood is a collection of houses which together work autonomously (as one unit). Some of the houses may be completely autonomous on one aspect (ie electricity production, ...) but not on other aspects (ie sewage disposal, ...)

Overview

One of the major drawbacks of centralised systems (ie municipal sewage systems, mains electricity grids, ...) is that they require long water pipin/cabling, towers, ... These components tend to increase the cost of the system, which is ultimately charged to the users of the system. In addition, besides increasing cost, it also decreases efficiency (ie a lot of energy is lost in the longer cabling, ...)

Autonomous houses however have very short piping/cabling. This has several advantages including reduced environmental impacts, increased security, and lower costs of ownership. Autonomous houses often rely very little on civil services and are therefore safer and more comfortable during civil disaster or military attacks. This, as the houses would not lose power or water if public supplies were compromised for some reason.

However, it would be very hard to impossible for every house to attain autonomous operation on each aspect (ie food production, water supply, sewage, energy production, ...) Even if it were possible, then systems in which autonomous operation is assured per neighbourhood (so say per 10 houses or per street -exact size depends on the region-) are still cheaper.

This is because, when we arrange autonomous operation per neighbourhood, 1 single (larger) unit (ie wind turbine, water treatment plant, ...) can serve much more people, hereby lowering the cost (ie when compared to each house requiring its own (smaller) unit). However, by nonetheless reducing the amount of people served compared to a municipal (or even nation-wide) system, we still increase self-sufficiency/security and also still increase the efficiency of the system.

Another major advantage of autonomous neighbourhood systems is that the tasks for maintaining the autonomy can be shared among much more people, hereby decreasing the effort required considerably. For example, food can be grown by one family and preserved by another. Sewage can be handled by yet another family, ...

Systems

In most aspects, autonomous houses/neighbourhoods tend to implement use reduction. This as it is a cost-effective approach (they limit the needed investments on the equipment, ...).

Water supply

There are many methods of collecting water. The most common methods are the use of a well or the use of rainwater harvesters.


Sewage/excreta disposal

Some of the oldest pre-system sewage types are pit toilets, latrines, and outhouses. These are still used in many developing countries but do not allow composting, incineration or any other method of destroying pathogens. As such, there is a serious risk of microbial and viral contamination and thus can cause the operator of becoming ill.

The standard system used today is a flush toilet with drain leach field and a septic tank. They however require huge amounts of water to operate and can be -relatively- complicated. Incinerator systems are also quite practical. The ashes are biologically safe, and take up less than 1/10 the volume of the original waste.

The approaches above however treat human excrement as a waste rather than a resource. Composted human excrement can be used to provide (or return, ie if the garden is used to grow food) nutrients to a garden. Recycling human excrement requires minimal life-style changes. In this context, Composting toilets are a better choice as they allow reuse of the human excrement, in a safe manner. They also reduce water use by half, and eliminate the difficulty and expense of septic tanks.

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 $800 per house (1970s) by eliminating storm drains.[1] 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 also captures some 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 electricity, although gas-powered refrigerators are not very efficient.[2] There are also superefficient electric refrigerators, such as those produced by the Sun Frost company, some of which use only about half as much electricity as a mass-market energy star-rated refrigerator.

PV-panels on the roof can also provide electric power. Solar tile roofs have the potential to be more cost-effective than retrofitted solar power, because buildings need roofs anyway. A downside however is that they can not rack the sun during the day, and are hard to access in case they need repairs/cleaning. Modern solar cells last about 40 years, which makes them a reasonable investment in some areas. Solar cells have only small life-style impacts: The cells must be cleaned a few times per year.

A number of areas that lack sun have wind. In these cases, wind turbines may be a solution.

During times of low demand, excess power can be stored in eletrochemical batteries for future use. However, batteries need to be replaced every few years. Microbial fuel cells allow the generation of electricity from biomass. Unlike direct incineration of biomass however, the method using a microbial fuel cell is completely emissionless. The plant can be chopped and converted as a whole, or it can be left alive so that waste saps from the plant can be converted by bacteria.

In addition, recent advances in passively stable magnetic bearings may someday permit inexpensive storage of power in a flywheel in a vacuum, and some other types of fuel cells may also be useful for storing power. Other possible options are Earth batteries.

In many areas, battery expenses can be eliminated by attaching the building to the electric power grid and operating the power system with net metering. Utility permission is required, but such cooperative generation is legally mandated in some areas (for example, California).[3]

A (semi-)grid-based building is less autonomous, but more economical and sustainable with fewer lifestyle sacrifices. In rural areas the grid's cost and impacts can be reduced by using single wire earth return systems (for example, the MALT-system).

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 on biofuel or petrofuel. An hour of charging usually provides a day of operation. Modern residential chargers permit the user to set the charging times, so the generator is quiet at night. Some generators automatically test themselves once per week.[4][5]

Heating and cooling

Most autonomous buildings are designed to use insulation, thermal mass and passive solar heating and cooling. Examples of these are trombe walls and other technologies as skylights.

Passive solar heating can heat most buildings in even the coldest climates. In colder climates, extra 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.

Earth sheltering and windbreaks can also reduce the absolute amount of heat needed by a building. Rounded, aerodynamic buildings also lose less heat.

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

Electric heaters and electric stoves may provide pollution-free heat (depending on the power source), but use 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 autonomous design.

An increasing number of commercial buildings use a combined cycle with cogeneration to provide heating, often water heating, from the output of a natural gas reciprocating engine, gas turbine or stirling electric generator.[6]

The domestic water can be heated using either the same heating system (ie gas or firewood can also be used to heat the domestic water, by using a heat exchanger). In addition, solar water heating can be incorporated (often as a additional technology).

Some authorities advocate that bottled gas or natural gas be replaced by biogas. However, this is usually impractical unless live-stock are on-site. The wastes of a single family are usually insufficient to produce enough methane for anything more than small amounts of cooking.


Annualized geo solar buildings often have buried, sloped water-tight skirts of insulation that extend Template:Convert 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 people have reported a temperature differential as high as Template:Nowrap (Template:Nowrap) 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.

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 Template:Convert, 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 production

Food production has often been included in historic autonomous projects to provide security.[7] Skilled, intensive gardening can support an adult from as little as 100 square meters of land per person,[8][9] possibly requiring the use of organic farming and aeroponics. Some proven intensive, low-effort food-production systems include urban gardening (indoors and outdoors). Indoor cultivation may be set up using hydroponics, while outdoor cultivation may be done using permaculture, forest gardening, no-till farming, and do nothing farming.

Greenhouses are also sometimes included (see Earthship Biotecture). Sometimes they are also outfitted with irrigation systems or heat sink-systems which can respectively irrigate the plants or help to store energy from the sun and redistribute it at night (when the greenhouses starts to cool down).[citation needed]

Communication

An 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. Private Internet protocol networks set up in this way can operate without the use of a commercial provider.

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.[10]

Satellite Internet access can provide high speed connectivity to remote locations, however these are significantly more expensive than wire-based or terrestrial wireless systems. Wimax and forms of packet radio can also be used. Depending on the speed and latency of these networks they may be capable of relaying VoIP traffic, negating the need for separate telephony services. Finally, the Internet Radio Linking Project provides potential for blending older (cheap) local radio broadcasting with the increased range of the internet.

Depending on the location a mobile phone network may be available which can provide voice and data services. satellite-based telephone systems can also be used, as either fixed installations or portable handsets and can be integrated into a PABX or local IP-based network.

Gallery

Notes and references

Template:Reflist

See also

External links

  1. Swales replacing drains: Paul Hawken, Amory Lovins and Hunter Lovins, "Natural Capitalism," ch. 5, pp83. The cited development is Village Homes, Davis, California, built in the 1970s by Michael and Judy Corbett
  2. Sunfrost rates 15 cu. ft. refrigerators at 0.27 kWh/day (2007-12-27), while Dometic (formerly Servel) gas refrigerators cool only 8cuft for 325 W continuous (i.e. 7.8 kWh/day) ALternatively, they use about 8 US gal of LP gas per month, which in most places is more expensive than the equivalent electricity.(2007-12-27)
  3. Gipe, ibid.
  4. Eaton power; see the specifications and manuals. Referenced 2007-12-27
  5. Kohler Generators; see the specifications and manuals. Referenced 2007-12-27
  6. Capstone Microturbine White-Paper (PDF) Retrieved on 2007-12-28.
  7. Publications list of the New Alchemy Institute. Retrieved 2010-02-05.
  8. "Urban Homestead at a Glance" Path of Freedom
  9. How to Grow a Complete Diet in Less Than 1000 Square Feet Dave Duhon & Cindy Gebhard, 1984, 200 pp. Ecology Action GROW BIOINTENSIVE(R) Publications
  10. Northern Economics Inc. and Electric Power Systems Inc. April 2001. "Screening Report for Alaska Rural Energy Plan." (Report published on government website). Alaska Department of Commerce, Community, and Economic Development, via dced.state.ak.us. Retrieved on 2007-09-16.
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