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102-827: The organization was founded to help address the evidence gap in off-grid water systems. Safe Water Network works with the private and public sectors to overcome obstacles to local sustainability and scale in providing clean and safe drinking water. It oversees field initiatives to develop and refine models for providing safe water that can be taken to scale. The network empowers communities by working with national, regional, and local government authorities in India and Ghana , as well as partnering with NGOs and private sector foundations and companies. Some of its partners include: The network has offices in Accra , New Delhi and New York . Off-the-grid Off-the-grid or off-grid

204-467: A composting toilet . Automatic leak detectors and tap closures can reduce amounts of wasted water. Greywater recycling can further save on water by reusing water from faucets, showers, dishwashers, and clothes washers. This is done through storing and treating the greywater, which can then be reused as a non-potable water source. If an off-grid home is not connected to a sewer system, a wastewater system must also be included. On-site wastewater management

306-428: A multi-mission radioisotope thermoelectric generator (MMRTG) in which the thermocouples would be made of skutterudite , a cobalt arsenide (CoAs 3 ), which can function with a smaller temperature difference than the current tellurium -based designs. This would mean that an otherwise similar RTG would generate 25% more power at the beginning of a mission and at least 50% more after seventeen years. NASA hopes to use

408-433: A "foreign object". A common route of production (whether accidental or deliberate) is neutron irradiation of Bi , the only naturally occurring isotope of bismuth . It is this accidental production that is cited as an argument against the use of lead-bismuth eutectic as a coolant in liquid metal reactors. However, if a sufficient demand for polonium-210 exists, its extraction could be worthwhile similar to how tritium

510-646: A current to water that has a small salt solution added to disinfect biological contaminants. Combined with filtration, this is a means to provide safe drinking water. Some groundwater may have high salinity levels and can be non-potable, which is fixed through distillation. Coastal communities may benefit by getting water from the ocean through the use of desalination plants that remove salt. The presence of certain minerals in water creates hard water which can clog pipes over time, interfere with soap and detergents, and can leave scum on glasses and dishes. Water softening systems introduce sodium and potassium ions which make

612-568: A factor of 1 – (1/2) , which is 0.787%, per year. One example is the MHW-RTG used by the Voyager probes . In the year 2000, 23 years after production, the radioactive material inside the RTG had decreased in power by 16.6%, i.e. providing 83.4% of its initial output; starting with a capacity of 470 W, after this length of time it would have a capacity of only 392 W. A related loss of power in

714-456: A further shielding against neutron radiation . As lead, which is an excellent shielding material against gamma rays and beta ray induced Bremsstrahlung , is not a good neutron shield (instead reflecting most of them), a different shielding material would have to be added in applications where neutrons are a concern. Most RTGs use Pu, which decays with a half-life of 87.7 years. RTGs using this material will therefore diminish in power output by

816-425: A half-life of 87.7 years, reasonable power density of 0.57 watts per gram, and exceptionally low gamma and neutron radiation levels. Pu has the lowest shielding requirements. Only three candidate isotopes meet the last criterion (not all are listed above) and need less than 25 mm of lead shielding to block the radiation. Pu (the best of these three) needs less than 2.5 mm, and in many cases, no shielding

918-603: A higher voltage. RTGs and fission reactors use very different nuclear reactions. Nuclear power reactors (including the miniaturized ones used in space) perform controlled nuclear fission in a chain reaction . The rate of the reaction can be controlled with neutron absorbing control rods , so power can be varied with demand or shut off (almost) entirely for maintenance. However, care is needed to avoid uncontrolled operation at dangerously high power levels, or even explosion or nuclear meltdown . Chain reactions do not occur in RTGs. Heat

1020-615: A land lab, students can learn about permaculture, photovoltaics, rainwater catchment, animal husbandry, composting, market gardening, biochar systems, methane digesters, rocket mass heaters, horticulture, ecology, and countless other off-grid concepts. Public schools, charter schools, private schools and homeschools can all benefit from using a land lab environment to teach students about sustainability, independence, and ecological systems. </ref>==External links== Radioisotope thermoelectric generator A radioisotope thermoelectric generator ( RTG , RITEG ), sometimes referred to as

1122-491: A larger number of such units have been deployed both on the ground and on the ocean floor than have been used on spacecraft, with public regulatory documents suggesting that the US had deployed at least 100–150 during the 1970s and 1980s. In the past, small "plutonium cells" (very small Pu-powered RTGs) were used in implanted heart pacemakers to ensure a very long "battery life". As of 2004 , about ninety were still in use. By

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1224-426: A much lower neutron emission rate for the oxide; this can be accomplished by a gas phase O 2 exchange method. Regular production batches of PuO 2 particles precipitated as a hydroxide were used to show that large production batches could be effectively O 2 -exchanged on a routine basis. High-fired PuO 2 microspheres were successfully O 2 -exchanged showing that an exchange will take place regardless of

1326-481: A radioisotope power system (RPS), is a type of nuclear battery that uses an array of thermocouples to convert the heat released by the decay of a suitable radioactive material into electricity by the Seebeck effect . This type of generator has no moving parts and is ideal for deployment in remote and harsh environments for extended periods with no risk of parts wearing out or malfunctioning. RTGs are usually

1428-420: A similar effect of dispersion by physically grinding the inert matrix into a fine dust. RTGs pose a risk of radioactive contamination : if the container holding the fuel leaks, the radioactive material may contaminate the environment. For spacecraft, the main concern is that if an accident were to occur during launch or a subsequent passage of a spacecraft close to Earth, harmful material could be released into

1530-478: A steady source of power. Most have no protection, not even fences or warning signs, and the locations of some of these facilities are no longer known due to poor record keeping. In one instance, the radioactive compartments were opened by a thief. In another case , three woodsmen in Tsalendzhikha Region, Georgia found two ceramic RTG orphan sources that had been stripped of their shielding; two of

1632-436: A stepping stool to eventual grid access can accumulate energy efficient knowledge, behavior, and products that confer added resiliency while grid networks increase in reliability and carbon neutrality . However, providing off-grid electricity to rural users without also including training and education about its use and applications can result in under-utilization. To counteract this possibility, off-grid systems should reflect

1734-402: A sustainable off-grid community must take into consideration the basic needs of all who live in the community . To become truly self-sufficient , the community would need to provide all of its own electrical power , food, shelter and water . Using renewable energy , an on-site water source, sustainable agriculture and vertical farming techniques is paramount in taking a community off

1836-691: A variety of scenarios. The technology of these portable batteries has evolved much through the years. Most of the portable power stations use 2 types of Lithium-Ion batteries: Nickel Manganese Cobalt (NMC) batteries and Lithium Iron Phosphate (LFP or LiFePo4) batteries. In order to protect against intermittency issues and system failures, many off-grid communities create hybrid energy systems. These combine traditional renewables like solar PV, and wind, micro-hydro, batteries or even diesel generators. This can be cheaper and more effective than extending or maintaining grids to isolated communities. Historically remote applications such as lighthouses, weather stations and

1938-548: Is direct current and is stored in batteries as direct current and DC buildings would eliminate the need for conversions from AC to DC . One third of electricity in the home is used as DC for electronics , LED lights , and other appliances already. The market for DC home appliances is maturing, which is necessary to have a 100% DC powered home. The electrical panel , circuit breakers , and fuses would need to be replaced with DC compatible components if retrofitting an AC house to DC. For net metering , to sell back to

2040-413: Is a thermoelectric device that can convert thermal energy directly into electrical energy using the Seebeck effect . It is made of two kinds of metal or semiconductor material. If they are connected to each other in a closed loop and the two junctions are at different temperatures , an electric current will flow in the loop. Typically a large number of thermocouples are connected in series to generate

2142-442: Is a characteristic of buildings and a lifestyle designed in an independent manner without reliance on one or more public utilities . The term "off-the-grid" traditionally refers to not being connected to the electrical grid , but can also include other utilities like water, gas, and sewer systems, and can scale from residential homes to small communities. Off-the-grid living allows for buildings and people to be self-sufficient, which

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2244-402: Is a pure alpha-emitter and does not emit significant gamma or X-ray radiation, the shielding requirements are as low as those for Pu. While the short half-life also reduces the time during which accidental release to the environment is a concern, polonium-210 is extremely radiotoxic if ingested and can cause significant harm even in chemically inert forms, which pass through the digestive tract as

2346-614: Is advantageous in isolated locations where normal utilities cannot reach and is attractive to those who want to reduce environmental impact and cost of living. Generally, an off-grid building must be able to supply energy and potable water for itself, as well as manage food, waste and wastewater. Energy for electrical power and heating can be derived from burning hydrocarbons (e.g., diesel generators, propane heating), or generated on-site with renewable energy sources such as solar (particularly with photovoltaics ), wind , or micro hydro . Additional forms of energy include biomass, commonly in

2448-538: Is almost equal parts Cs-135 and Cs-137, plus significant amounts of stable Cs-133 and, in "young" spent fuel, short lived Cs-134. If isotope separation , a costly and time-consuming process, is to be avoided, this has to be factored in, too. While historically RTGs have been rather small, there is in theory nothing preventing RTGs from reaching into the Megawatt thermal range of power. However, for such applications actinides are less suitable than lighter radioisotopes as

2550-406: Is commonly used as strontium titanate in RTGs, which increases molar mass by about a factor of 2. Furthermore, depending on the source, isotopic purity may not be obtainable. Plutonium extracted from spent nuclear fuel has a low share of Pu-238, so plutonium-238 for use in RTGs is usually purpose-made by neutron irradiation of neptunium-237 , further raising costs. Caesium in fission products

2652-459: Is economically recovered from the heavy water moderator in CANDUs . Americium-241 is a candidate isotope with much greater availability than Pu. Although Am has a half-life of 432 years, which is about five times longer than that of Pu and could hypothetically power a device for centuries, missions with more than 10 years were not the subject of the research until 2019. The power density of Am

2754-491: Is funded, the goal would be to set up automation and scale-up processes in order to produce an average of 1.5 kg (3.3 lb) per year by 2025. Strontium-90 has been used by the Soviet Union in terrestrial RTGs. Sr decays by β emission, with minor γ emission. While its half life of 28.8 years is much shorter than that of Pu, it also has a lower decay energy with a power density of 0.46 watts per gram. Because

2856-528: Is generally good for the environment with little negative impact. Hybrid energy systems also provide communities with a sustainable way to live without the dependence and cost of being connected to public infrastructure which can be unreliable in developing countries. Generally, isolated concerns of environmental impacts are the use diesel generators, which produce greenhouse gases, batteries, which use many resources to make and can be hazardous , and pollution in natural environments from solid waste and wastewater. It

2958-464: Is most likely that they melted through the glacier and were pulverized, whereupon the Pu–Zr alloy fuel oxidized soil particles that are moving in a plume under the glacier. Many Beta-M RTGs produced by the Soviet Union to power lighthouses and beacons have become orphaned sources of radiation. Several of these units have been illegally dismantled for scrap metal (resulting in the complete exposure of

3060-548: Is needed in a Pu RTG, as the casing itself is adequate. Pu has become the most widely used fuel for RTGs, in the form of plutonium(IV) oxide (PuO 2 ). However, plutonium(IV) oxide containing a natural abundance of oxygen emits neutrons at the rate of roughly 2.3 × 10  n/sec/g of plutonium-238. This emission rate is relatively high compared to the neutron emission rate of plutonium-238 metal. The metal containing no light element impurities emits roughly 2.8 × 10  n/sec/g of plutonium-238. These neutrons are produced by

3162-466: Is not currently needed, the electrical energy is usually directed to charge a battery. This solves intermittency issues caused by the non-constant production of renewables and allows for variations in building loads. Common batteries include the lead-acid battery and lithium-ion battery. There are portable batteries and non-portable batteries. These portable power stations are often used in remote areas, since they don't require installation and can be used in

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3264-433: Is only one-fourth that of Pu, and Am produces more penetrating radiation through decay chain products than Pu and needs more shielding. Its shielding requirements in a RTG are the third lowest: only Pu and Po require less. With a current global shortage of Pu, Am is being studied as RTG fuel by ESA and in 2019, UK's National Nuclear Laboratory announced the generation of usable electricity. An advantage over Pu

3366-447: Is present and abundant underground, usually to the water table or to an aquifer, and bringing it up for use, or collecting at springs where underground water comes to the surface. Systems for bringing underground water to buildings include wind and solar driven pumps or hand pumps. Well water should be tested on a regular basis and when changes in the water's taste, odor, or appearance occur to ensure its quality. This system relies on

3468-504: Is produced through spontaneous radioactive decay at a non-adjustable and steadily decreasing rate that depends only on the amount of fuel isotope and its half-life. In an RTG, heat generation cannot be varied with demand or shut off when not needed and it is not possible to save more energy for later by reducing the power consumption. Therefore, auxiliary power supplies (such as rechargeable batteries) may be needed to meet peak demand, and adequate cooling must be provided at all times including

3570-495: Is prudent to note that, while the concerns below address negative environmental impacts, going off-grid as a whole is a viable option to help reduce impacts on the environment when replacing grid-connected buildings that contribute global warming and climate change. Canada has about 175 aboriginal and northern off-grid communities, defined as "a community that is neither connected to the North American electrical grid nor to

3672-441: Is simple by the standards of nuclear technology : the main component is a sturdy container of a radioactive material (the fuel). Thermocouples are placed in the walls of the container, with the outer end of each thermocouple connected to a heat sink . Radioactive decay of the fuel produces heat. It is the temperature difference between the fuel and the heat sink that allows the thermocouples to generate electricity. A thermocouple

3774-418: Is that it is produced as nuclear waste and is nearly isotopically pure. Prototype designs of Am RTGs expect 2–2.2 W e /kg for 5–50 W e RTGs design but practical testing shows that only 1.3–1.9 W e can be achieved. Americium-241 is currently used in small quantities in household smoke detectors and thus its handling and properties are well-established. However, it decays to neptunium-237 ,

3876-796: Is the Lia radiological accident in Georgia , December 2001. Strontium-90 RTG cores were dumped behind, unlabeled and improperly dismanteled, near the Soviet-built Enguri Dam . Three villagers from the nearby village of Lia were unknowingly exposed to it and injured; one of them died in May 2004 from the injuries sustained. The International Atomic Energy Agency led recovery operations and organized medical care. Two remaining RTG cores are yet to be found as of 2022. There have been several known accidents involving RTG-powered spacecraft: One RTG,

3978-406: Is unlikely as SrTiO 3 passes through the digestive tract of humans or other animals unchanged, but the animal or human who ingested it would still receive a significant radiation dose to the sensitive intestinal lining during passage. Mechanical degradation of "pebbles" or larger objects into fine dust is more likely and could disperse the material over a wider area, however this would also reduce

4080-425: Is usually done through storage and leaching. This involves storing greywater and blackwater in a septic tank or aeration tank to be treated, which is connected to a leaching field that slowly allows the water to percolate out into the ground. While more and expensive waste water treatment options are also available, this is a common reliable means to dispose of waste water without polluting the environment. Going off

4182-784: The Dragonfly mission to Titan . RTGs were also used instead of solar panels to power the two Viking landers, and for the scientific experiments left on the Moon by the crews of Apollo 12 through 17 (SNAP 27s). Because the Apollo 13 Moon landing was aborted, its RTG rests in the South Pacific Ocean , in the vicinity of the Tonga Trench . The Curiosity and Perseverance Mars rover designs selected RTGs to allow greater flexibility in landing sites and longer lifespan than

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4284-757: The Arctic Circle . Safe use of RTGs requires containment of the radioisotopes long after the productive life of the unit. The expense of RTGs tends to limit their use to niche applications in rare or special situations. The RTG was invented in 1954 by Mound Laboratories scientists Kenneth (Ken) C. Jordan (1921–2008) and John Birden (1918–2011). They were inducted into the National Inventors Hall of Fame in 2013. Jordan and Birden worked on an Army Signal Corps contract (R-65-8- 998 11-SC-03-91) beginning on 1 January 1957, to conduct research on radioactive materials and thermocouples suitable for

4386-574: The SNAP-19C , was lost near the top of Nanda Devi mountain in India in 1965 when it was stored in a rock formation near the top of the mountain in the face of a snowstorm before it could be installed to power a CIA remote automated station collecting telemetry from the Chinese rocket testing facility. The seven capsules were carried down the mountain onto a glacier by an avalanche and never recovered. It

4488-464: The Soviet Arctic coast by the late 1980s. Many different types of RTGs (including Beta-M type) were built in the Soviet Union for a wide variety of purposes. The lighthouses were not maintained for many years after the dissolution of the Soviet Union in 1991 . Some of the RTG units disappeared during this time—either by looting or by the natural forces of ice/storm/sea. In 1996, a project

4590-626: The Sr-90 source), fallen into the ocean, or have defective shielding due to poor design or physical damage. The US Department of Defense cooperative threat reduction program has expressed concern that material from the Beta-M RTGs can be used by terrorists to construct a dirty bomb . However, the Strontium titanate perovskite used is resistant to all likely forms of environmental degradation and cannot melt or dissolve in water. Bioaccumulation

4692-500: The critical mass is orders of magnitude below the mass needed to produce such amounts of power. As Sr-90, Cs-137 and other lighter radionuclides cannot maintain a nuclear chain reaction under any circumstances, RTGs of arbitrary size and power could be assembled from them if enough material can be produced. In general, however, potential applications for such large-scale RTGs are more the domain of small modular reactors , microreactors or non-nuclear power sources. Plutonium-238 has

4794-456: The ASRG uses a Stirling power device that runs on radioisotope (see Stirling radioisotope generator ) The radioactive material used in RTGs must have several characteristics: The first two criteria limit the number of possible fuels to fewer than thirty atomic isotopes within the entire table of nuclides . Plutonium-238 , curium-244 , strontium-90 , and most recently americium-241 are

4896-561: The BES-5 Buk ( БЭС-5 ) reactor was a fast reactor which used thermocouples based on semiconductors to convert heat directly into electricity *** not really an RTG, the SNAP-10A used enriched uranium fuel, zirconium hydride as a moderator, liquid sodium potassium alloy coolant, and was activated or deactivated with beryllium reflectors Reactor heat fed a thermoelectric conversion system for electrical production. **** not really an RTG,

4998-587: The Center for Space Nuclear Research (CSNR) in 2013 for studies of feasibility. However the essentials are unmodified. RTG have been proposed for use on realistic interstellar precursor missions and interstellar probes . An example of this is the Innovative Interstellar Explorer (2003–current) proposal from NASA. An RTG using Am was proposed for this type of mission in 2002. This could support mission extensions up to 1000 years on

5100-750: The Navy Transit 4A spacecraft . One of the first terrestrial uses of RTGs was in 1966 by the US Navy at uninhabited Fairway Rock in Alaska. RTGs were used at that site until 1995. A common RTG application is spacecraft power supply. Several generations of RTG design have been used for probes that traveled far from the Sun, rendering solar panels impractical. As such, they have been used for Pioneer 10 and 11 ; Voyager 1 and 2 ; Galileo ; Ulysses ; Cassini ; New Horizons ; and are planned for

5202-411: The RTGs was estimated at 1 in 10. The launch was successful and Cassini–Huygens reached Saturn . To minimize the risk of the radioactive material being released, the fuel is stored in individual modular units with their own heat shielding. They are surrounded by a layer of iridium metal and encased in high-strength graphite blocks. These two materials are corrosion- and heat-resistant. Surrounding

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5304-519: The Voyager RTGs is the degrading properties of the bi-metallic thermocouples used to convert thermal energy into electrical energy ; the RTGs were working at about 67% of their total original capacity instead of the expected 83.4%. By the beginning of 2001, the power generated by the Voyager RTGs had dropped to 315 W for Voyager 1 and to 319 W for Voyager 2 . By 2022, these numbers had dropped to around 220 W. NASA has developed

5406-454: The advantages of central power generation and distribution are receding in the face of climatic degradation due to fossil fuel powered generation, vulnerabilities to extreme weather events and electronic manipulation, and increasingly complex design and regulatory processes. Decentralized, off-grid energy systems can constitute a sustainable interim alternative to extending national grids to rural customers. Those using limited off-grid power as

5508-408: The alpha decay from the radioisotope is also used in alpha-neutron reactions with a suitable element such as beryllium . This way a long-lived neutron source is produced. Because the system is working with a criticality close to but less than 1, i.e. K eff < 1, a subcritical multiplication is achieved which increases the neutron background and produces energy from fission reactions. Although

5610-569: The atmosphere; therefore their use in spacecraft and elsewhere has attracted controversy. However, this event is not considered likely with current RTG cask designs. For instance, the environmental impact study for the Cassini–Huygens probe launched in 1997 estimated the probability of contamination accidents at various stages in the mission. The probability of an accident occurring which caused radioactive release from one or more of its three RTGs (or from its 129 radioisotope heater units ) during

5712-522: The bones it can significantly damage the bone marrow , a rapidly dividing tissue), it is usually not employed in pure form in RTGs. The most common form is the perovskite strontium titanate (SrTiO 3 ) which is chemically nigh-inert and has a high melting point. While its Mohs hardness of 5.5 has made it ill-suited as a diamond simulant , it is of sufficient hardness to withstand some forms of accidental release from its shielding without too fine dispersal of dust. The downside to using SrTiO 3 instead of

5814-646: The case of devices for water generation and permanent piped water supply networks . Furthermore, grids may often be substantially more efficient and effective or necessary – such as in the case of smart grids and super grids for sustainable energy – and hence may often only be useful on large scales for autonomous community development of alternatives, as fallback, for disaster response , for other humanitarian aid during temporary relocation, and for initial support of long-term infrastructure development. Land labs provide an outdoor classroom environment for students to learn about off-grid technology and methods. Within

5916-590: The cost of outside utilities is prohibitive, or such a distance away as to be impractical. In his book How to live off-grid Nick Rosen lists seven reasons for going off-grid. The top two are saving money, and reducing the carbon footprint. Others include survivalists , preparing for the collapse of the oil economy and bringing life back to the countryside. Reliable centralized electricity systems have provided supply constancy which has bolstered societies and their economies. Electricity provides opportunities for improved productivity, learning, and hygienic end-uses in

6018-1175: The cultural structures, values, and mores of host communities. Off-grid electrical systems can power individual residences or a community linked in a shared arrangement known as a micro-grid . In addition, they may be powered by renewable energy sources or by conventional fossil fuels. In Kenya, Mpeketoni township began a community-based, diesel-powered micro-grid project (the Mpeketoni Electricity Project [MEP]) in 1994 with an outlay of approximately US$ 40,000, and eventually grew to serve 105 residences and 116 commercial, educational, government, and healthcare buildings. The MEP demonstrated unanticipated supply and demand effects when artisans using tools powered by MEP electricity increased their productivity enough to cause depreciation of their wares, necessitating lowering of their prices; however, higher volumes of sales eventually offset these losses. MEP electricity facilitated cold storage of agricultural products, in addition to well pumping, which allowed students who previously spent several hours per day fetching water to spend that time studying in

6120-401: The design on the next New Frontiers mission. Radioactive materials contained in RTGs are dangerous and can even be used for malicious purposes. They are not useful for a genuine nuclear weapon , but still can serve in a " dirty bomb ". The Soviet Union constructed many uncrewed lighthouses and navigation beacons powered by RTGs using strontium-90 ( Sr). They are very reliable and provide

6222-620: The desired strontium titanate plus carbon dioxide . If desired, the strontium titanate product can then be formed into a ceramic-like aggregate via sintering . Some prototype RTGs, first built in 1958 by the US Atomic Energy Commission, have used polonium-210 . This isotope provides phenomenal power density (pure Po emits 140 W /g) because of its high decay rate , but has limited use because of its very short half-life of 138 days. A half-gram sample of Po reaches temperatures of over 500 °C (900 °F). As Po

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6324-651: The direct conversion of heat to electrical energy using polonium-210 as the heat source. RTGs were developed in the US during the late 1950s by Mound Laboratories in Miamisburg, Ohio , under contract with the United States Atomic Energy Commission . The project was led by Dr. Bertram C. Blanke. The first RTG launched into space by the United States was SNAP 3B in 1961 powered by 96 grams of plutonium-238 metal, aboard

6426-415: The end of 2007, the number was reported to be down to just nine. The Mound Laboratory Cardiac Pacemaker program began on 1 June 1966, in conjunction with NUMEC. When it was recognized that the heat source would not remain intact during cremation, the program was cancelled in 1972 because there was no way to completely ensure that the units would not be cremated with their users' bodies. The design of an RTG

6528-476: The energy output is lower it reaches lower temperatures than Pu, which results in lower RTG efficiency. Sr has a high fission product yield in the fission of both U and Pu and is thus available in large quantities at a relatively low price if extracted from spent nuclear fuel . As Sr is a very reactive alkaline earth metal and a so-called "bone seeker" that accumulates in bone-tissue due to its chemical similarity to calcium (once in

6630-634: The evening by electric light. Electricity provided by the MEP also expanded teaching hours and sanitation at local schools through electric lighting and pumped water. The MEP off-grid project had numerous direct and indirect benefits for community members, and because the MEP emphasized promotion of the uses for electricity and the community had the ability to pay nominal rates for its use, the project achieved 94 percent cost recovery in its first ten years of operation. Off-the-grid generation may sometimes inhibit efforts to develop permanent infrastructure – such as in

6732-439: The first 3.5 minutes following launch was estimated at 1 in 1,400; the chances of a release later in the ascent into orbit were 1 in 476; after that the likelihood of an accidental release fell off sharply to less than 1 in a million. If an accident which had the potential to cause contamination occurred during the launch phases (such as the spacecraft failing to reach orbit), the probability of contamination actually being caused by

6834-705: The form of wood, waste, and alcohol fuels and geothermal energy, which uses differences in the underground temperature to regular indoor air environments in buildings. It is possible to simply eliminate energy shortage (e.g., via solar and wind tech such as in Old Order Amish - while used and sanctioned, not all agree) and Old Order Mennonite communities, and many Amish people still use steam engines . Grid-connected buildings receive electricity from power plants, which mainly use natural resources such as coal and natural gas as energy to convert into electrical power. 2017's breakdown of world energy sources shows that

6936-501: The globe, mainly dependent on grid power, uses a majority of non-renewables, while popular renewables such as solar PV and wind power are a small portion. When off the grid, such as in Africa where 55% people of do not have access to electricity, buildings and homes must take advantage of the renewable energy sources around them, because it is the most abundant and allows for self-sufficiency. Solar photovoltaics (PV), which use energy from

7038-549: The graphite blocks is an aeroshell, designed to protect the entire assembly against the heat of reentering the Earth's atmosphere. The plutonium fuel is also stored in a ceramic form that is heat-resistant, minimising the risk of vaporization and aerosolization. The ceramic is also highly insoluble . The plutonium-238 used in these RTGs has a half-life of 87.74 years, in contrast to the 24,110 year half-life of plutonium-239 used in nuclear weapons and reactors . A consequence of

7140-445: The grid financially could be done by using cash , cash cards , cryptocurrencies , alternative community currencies , off grid peer-to-peer lending , and bullion coins . It could be useful to protect financial assets from bank failures , bank fraud , asset freezing , electromagnetic pulse , and from creditors or debt collectors . Because off-grid buildings and communities mainly rely on upon renewable energy, off-grid living

7242-1082: The grid, an inverter would still be needed, and also to use the grid-as-a-backup, if still using a grid-tied electrical system . DC electricity doesn't transmit over power lines efficiently over long distances, but if it is generated and stored in batteries on site, it is more efficient by 10-20 percent to keep it as DC and run appliances that way without inverting . Types of solar-energy passive off-grid cooling systems could be used for cooling houses and/or refrigeration – including some that do not require electrical components and are allowing for chemically stored on-demand energy. Such may be useful for climate change mitigation and adaptation . Meshnets such as B.A.T.M.A.N. could be used to sustain or establish communications without conventional infrastructure. Moreover, off-grid communications technologies could be used for environmental, security and agricultural monitoring as well as for emergency communications and coordination – such as for work assignation. Drones have been used for off-grid healthcare, especially in

7344-503: The grid. A recent concept design by Eric Wichman shows a multi-family community, which combines all of these technologies into one self-sufficient neighborhood. To grow the community you simply add neighborhoods using the same model as the first. A self-sustained community reduces its impact on the environment by controlling its waste and carbon footprint . In situations where grid parity has been reached, it becomes cheaper to generate one's own electricity rather than purchasing it from

7446-469: The grid. This depends on equipment costs, the availability of renewable energy sources, and the cost of a grid connection. For example, in certain remote areas a grid connection would be prohibitively expensive, resulting in grid parity being reached immediately. It is often done to residential buildings only occasionally occupied, such as vacation cabins, to avoid high initial costs of traditional utility connections. Other people choose to live in houses where

7548-407: The hard minerals precipitate. For off-grid buildings, efficient use of water is needed to prevent water supplies from running out. While this is ultimately habit-dependent, measures involve low-flow fixtures for faucets, shower heads, and toilets which decreases the flow rate of faucets or the volume of water per flush to reduce total water used. Water can be eliminated in toilets through the uses of

7650-520: The home, such as cooking without the use of polluting biomass fuel sources, yet as of 2016, 20 percent of people worldwide lived without it. Bridging the gap from the current under-provision of grid electricity to universal access has been projected to require US$ 17 trillion and 30 years even on a rigorous timetable. Researchers have argued that a lack of centralized energy infrastructure can result in low resilience to damage to productivity and property from changing climates and severe weather. In addition,

7752-441: The interstellar probe, because the power output would decline more slowly over the long term than plutonium. Other isotopes for RTG were also examined in the study, looking at traits such as watt/gram, half-life, and decay products. An interstellar probe proposal from 1999 suggested using three advanced radioisotope power sources (ARPS). The RTG electricity can be used for powering scientific instruments and communication to Earth on

7854-571: The likes which draw a small but continuous amount of power were powered by Radioisotope thermoelectric generators (RTGs) with the needed radioisotopes either extracted from spent nuclear fuel or produced in dedicated facilities. Both the Soviet Union and the United States employed numerous such devices on earth and every deep space probe reaching beyond the orbit of Mars (and even some in the inner solar system) has had an RTG to provide power where solar panels no longer deliver sufficient electricity per unit of mass. Electricity produced by photovoltaics

7956-472: The most chemically mobile among the actinides. Curium-250 is the isotope with the lowest atomic number that primarily decays by spontaneous fission, a process that releases many times more energy than alpha decay. Compared to plutonium-238, curium-250 provides about a quarter of the power density, but 95 times the half-life (~8300 years vs. ~87 years). As it is a neutron emitter (weaker than californium-252 but not entirely negligible) some applications require

8058-482: The most desirable power source for unmaintained situations that need a few hundred watts (or less) of power for durations too long for fuel cells , batteries, or generators to provide economically, and in places where solar cells are not practical. RTGs have been used as power sources in satellites , space probes , and uncrewed remote facilities such as a series of lighthouses built by the Soviet Union inside

8160-595: The most often cited candidate isotopes, but 43 more isotopes out of approximately 1,300 were considered at the beginning in the 1950s. The table below does not necessarily give power densities for the pure material but for a chemically inert form. For actinides this is of little concern as their oxides are usually inert enough (and can be transformed into ceramics further increasing their stability), but for alkali metals and alkaline earth metals like caesium or strontium respectively, relatively complex (and heavy) chemical compounds have to be used. For example, strontium

8262-480: The most remote regions of the world. With communications enabled, they deliver test samples, medicine, vaccines, food, water and anti-venoms. Small-scale waste management techniques in Western Europe, often for specific or standardized waste, were reported to mostly use one of two main strategies: aerobic (with plants) and anaerobic treatment (with biogas production). Water is a crucial consideration in

8364-527: The native metal is that its production requires energy. It also reduces power density, as the TiO 3 part of the material does not produce any decay heat. Starting from the oxide or the native metal, one pathway to obtaining SrTiO 3 is to let it transform to strontium hydroxide in aqueous solution, which absorbs carbon dioxide from air to become less soluble strontium carbonate . Reaction of strontium carbonate with titanium dioxide at high temperature produces

8466-505: The number of fissions produced in the RTG is very small (making their gamma radiation negligible), because each fission reaction releases over 30 times more energy than each alpha decay (200  MeV compared to 6 MeV), up to a 10% energy gain is attainable, which translates into a reduction of the Pu needed per mission. The idea was proposed to NASA in 2012 for the yearly NASA NSPIRE competition, which translated to Idaho National Laboratory at

8568-428: The off-grid environment, which must be collected, used, and disposed of efficiently to make use of the environment. There are many ways to supply water for indoor domestic use, which vary based on local access and preference. Nearby streams, ponds, rivers, and lakes are easy access points for fresh water. Oceans can also be considered with proper desalination. This traditional method involves digging down to where water

8670-741: The off-grid site. Atmospheric water generators have a large potential for off-the-grid water generation. Wherever the water does come from, it must be safe to drink and use indoors. For various issues with water quality, different water treatment strategies are available. A physical barrier allows water to pass through and blocks impurities in the water and, if the filter is fine enough, can filter out biological contaminants. In order to disinfect water, such as chlorine, chlorine dioxide, and ozone are introduced which kill microorganisms. A UV system uses bulbs that emit ultraviolet light into filtered water to kill all types of viruses, bacteria, and protozoa. A less typical approach, this involves applying

8772-443: The other three isotopes discussed in this section, Pu must be specifically synthesized and is not abundant as a nuclear waste product. At present only Russia has maintained high-volume production, while in the US, no more than 50 g (1.8 oz) were produced in total between 2013 and 2018. The US agencies involved desire to begin the production of the material at a rate of 300 to 400 grams (11 to 14 oz) per year. If this plan

8874-581: The piped natural gas network; it is permanent or long-term (5 years or more), and the settlements have at least 10 permanent buildings." Aboriginal Affairs and Northern Development Canada lists the following environmental concerns for these off-grid communities: The environmental impacts of the systems used in off-grid buildings must also be considered due to embodied energy , embodied carbon , choice and source of materials, which can contribute to world issues such as climate change, air, water, and soil pollution , resource depletion and more. The concept of

8976-487: The pre-launch and early flight phases of a space mission. While spectacular failures like a nuclear meltdown or explosion are impossible with an RTG, there is still a risk of radioactive contamination if the rocket explodes, the device reenters the atmosphere and disintegrates, terrestrial RTGs are damaged by storms or seasonal ice, or are vandalized. Due to the shortage of plutonium-238, a new kind of RTG assisted by subcritical reactions has been proposed. In this kind of RTG,

9078-578: The previous heat treatment history of the PuO 2 . This lowering of the neutron emission rate of PuO 2 containing normal oxygen by a factor of five was discovered during the cardiac pacemaker research at Mound Laboratory in 1966, due in part to the Mound Laboratory's experience with production of stable isotopes beginning in 1960. For production of the large heat sources the shielding required would have been prohibitive without this process. Unlike

9180-428: The previous quarter and publish a list of Tier 1 Solar Module (panel) Manufacturers. Wind energy can be harnessed by wind turbines. Wind turbines components consist of blades that get pushed by wind, gearboxes, controllers, generators, brakes, and a tower. The amount of mechanical power captured from a wind turbine is a factor of the wind speed, air density, blade rotational area, and the aerodynamic power coefficient of

9282-458: The probes. One mission proposed using the electricity to power ion engines , calling this method radioisotope electric propulsion (REP). A power enhancement for radioisotope heat sources based on a self-induced electrostatic field has been proposed. According to the authors, enhancements of 5-10% could be attainable using beta sources. A typical RTG is powered by radioactive decay and features electricity from thermoelectric conversion, but for

9384-502: The risk of radioactive contamination. Transforming the radioactive material into an inert form reduces the danger of theft by people unaware of the radiation hazard (such as happened in the Goiânia accident in an abandoned Cs-137 source where the caesium was present in easily water-soluble caesium chloride form). However, a sufficiently chemically skilled malicious actor could extract a volatile species from inert material and/or achieve

9486-597: The sake of knowledge, some systems with some variations on that concept are included here. Known spacecraft/nuclear power systems and their fate. Systems face a variety of fates, for example, Apollo's SNAP-27 were left on the Moon. Some other spacecraft also have small radioisotope heaters, for example each of the Mars Exploration Rovers have a 1 watt radioisotope heater. Spacecraft use different amounts of material, for example MSL Curiosity has 4.8 kg of plutonium-238 dioxide . ** not really an RTG,

9588-439: The same, plutonium-238 is around 275 times more toxic by weight than plutonium-239. The alpha radiation emitted by either isotope will not penetrate the skin, but it can irradiate internal organs if plutonium is inhaled or ingested. Particularly at risk is the skeleton , the surface of which is likely to absorb the isotope, and the liver , where the isotope will collect and become concentrated. A case of RTG-related irradiation

9690-410: The shorter half-life is that plutonium-238 is about 275 times more radioactive than plutonium-239 (i.e. 17.3 curies (640  GBq )/ g compared to 0.063 curies (2.3 GBq)/g ). For instance, 3.6  kg of plutonium-238 undergoes the same number of radioactive decays per second as 1 tonne of plutonium-239. Since the morbidity of the two isotopes in terms of absorbed radioactivity is almost exactly

9792-599: The solar-powered option, as used in prior generations of rovers . RTGs were also used for the Nimbus , Transit and LES satellites. By comparison, only a few space vehicles have been launched using full-fledged nuclear reactors : the Soviet RORSAT series and the American SNAP-10A . In addition to spacecraft, the Soviet Union built 1,007 RTGs to power uncrewed lighthouses and navigation beacons on

9894-406: The spontaneous fission of plutonium-238. The difference in the emission rates of the metal and the oxide is due mainly to the alpha, neutron reaction with the oxygen-18 and oxygen-17 present in the oxide. The normal amount of oxygen-18 present in the natural form is 0.204% while that of oxygen-17 is 0.037%. The reduction of the oxygen-17 and oxygen-18 present in the plutonium dioxide will result in

9996-530: The sun, are one of the most popular energy solutions for off-grid buildings. PV arrays (solar panels) allow for energy from the sun to be converted into electrical energy. PV is dependent upon solar radiation and ambient temperature. Other components needed in a PV system include charge controllers, inverters, and rapid shutdown controls. These systems give off-grid sites the ability to generate energy without grid connection. Every quarter, Bloomberg New Energy Finance evaluates manufacturers on their actual projects over

10098-496: The turbine. Where water is abundant, hydropower is a promising energy solution. Large scale hydropower involves a dam and reservoir, and small scale micro-hydro can use turbines in rivers with constant levels of water. The amount of mechanical power generated is a factor of the flow of the stream, turbine size, water density, and power coefficient, similar to wind turbines. The energy from waves and tides can also provide power to coastal areas. When renewables produce energy that

10200-455: The weather to provide water. Catchment systems are designed based on the water demand of the users and local rainfall characteristics. Rain water is typically funneled from the roof of a building to water tanks where the water is stored until needed. Another, less self-sufficient method involves bringing large amounts of clean water to the site where it is stored. This system relies on access to clean drinking water elsewhere and transportation to

10302-497: The woodsmen were later hospitalized with severe radiation burns after carrying the sources on their backs. The units were eventually recovered and isolated. There are approximately 1,000 such RTGs in Russia, all of which have long since exceeded their designed operational lives of ten years. Most of these RTGs likely no longer function, and may need to be dismantled. Some of their metal casings have been stripped by metal hunters, despite

10404-601: Was begun by Russian and international supporters to decommission the RTGs in the lighthouses, and by 2021, all RTGs had been removed. As of 1992, the United States Air Force also used RTGs to power remotely-located Arctic equipment, and the US government has used hundreds of such units to power remote stations globally. Sensing stations for Top-ROCC and SEEK IGLOO radar systems, predominantly located in Alaska , use RTGs. The units use strontium-90 , and

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