A geothermal heat pump or ground source heat pump (GSHP) is a central heating and/or cooling system that transfers heat to or from the ground.
It uses the earth as a source of heat (in winter) or heat sink (in summer). These designs utilize moderate temperatures in the soil to improve efficiency and reduce operating costs of heating and cooling systems, and can be combined with solar heating to form geosolar systems with higher efficiency. They are also known by other names, including the geoexchange, earth-coupled, earth energy system. The engineering and scientific societies prefer the term "geoexchange" or "ground source heat pumps" to avoid confusion with traditional geothermal power, which uses high-temperature heat sources to generate electricity. Heat pumps heat sources harvest heat absorbed in the Earth's surface from solar energy. The temperature in the soil below 6 meters (20 feet) is approximately equal to the average annual air temperature at that latitude on the surface.
Depending on the latitude, temperatures below 6 meters (20 feet) of the earth's surface maintain an almost constant temperature between 10 and 16 Â ° C (50 and 60 Â ° F), if the temperature is not interrupted by the presence of pump heat. Like a refrigerator or air conditioner, the system uses a heat pump to force heat transfer from the ground. The heat pump can transfer heat from the cold room to the warm room, against the direction of the natural flow, or they can increase the flow of natural heat from the warm area to the cold. The core of a heat pump is a loop of refrigerant that is pumped through a vapor compression refrigeration cycle that drives heat. Air source heat pumps are typically more efficient in heating than pure electric heaters, even when extracting heat from winter air, although efficiency begins to drop significantly when outdoor air temperature falls below 5 Â ° C (41 Â ° F). Heat pumps heat sources exchange heat with soil. This is much more energy efficient because the underground temperature is more stable than the air temperature throughout the year. Seasonal variations fall with depth and disappear below 7 meters (23 feet) to 12 meters (39 feet) due to thermal inertia. Like a cave, shallow ground temperatures are warmer than the air above during the winter and colder than the summer air. Heat source heat pump extracts soil heat in winter (for heating) and transfers heat back to the ground in summer (for cooling). Some systems are designed to operate in one mode only, heating or cooling, depending on the climate.
The geothermal pump system achieves a high performance coefficient (CoP), 3 to 6, on the coldest night of winter, compared to 1.75-2.5 for air source heat pumps on cold days. The ground source heat pump (GSHPs) is one of the most energy-efficient technologies to provide HVAC and water heaters.
Installation costs are higher than conventional systems, but the difference is usually returned in energy savings in 3 to 10 years, and even shorter periods with federal and state tax credits and incentives and incentives. Geothermal heat pump systems are reasonably guaranteed by the manufacturer, and their service life is estimated to be 25 years for inner components and 50 years for ground loops. In 2004, there were more than one million worldwide installed units providing 12 GW of thermal capacity, with an annual growth rate of 10%.
Video Geothermal heat pump
Different terms and definitions
Some confusion exists with the terminology of the heat pump and the use of the term "geothermal ". "Geothermal " comes from Greek and means "Geothermal " - which geologists and many laypeople understand as describing hot rocks, volcanic activity or heat coming from within the earth. Although some confusion arises when the term " geothermal " is also used to apply to temperatures within the first 100 meters of the surface, this is " Geothermal " all the same, though largely influenced by energy stored from the sun.
Maps Geothermal heat pump
History
The heat pump was described by Lord Kelvin in 1853 and was developed by Peter Ritter von Rittinger in 1855. After experimenting with freezers, Robert C. Webber built the first direct source heat pump in the late 1940s. The first successful commercial project was installed at the Commonwealth Building (Portland, Oregon) in 1948, and has been designated as the Landmark of the National Machine Engineering History by ASME. This technology became popular in Sweden in the 1970s, and has grown slowly in the reception of the world ever since. The open-loop system dominated the market until the development of polybutylene pipes in 1979 made the closed loop system economical. In 2004, there were more than one million units installed worldwide that provided 12 GW of thermal capacity. Every year, about 80,000 units are installed in the US (geothermal energy is used in all 50 US states today, with huge potential for growth and short-term market savings) and 27,000 in Sweden. In Finland, geothermal heat pumps are the most common heating system choice for new detached houses between 2006 and 2011 with market share exceeding 40%.
Geothermal
The heat pump provides winter heating by extracting heat from the source and transferring it into the building. Heat can be extracted from various sources, no matter how cool, but warmer sources allow for higher efficiency. Soil source heat pumps use the top layer of the earth's crust as a heat source, thus utilizing moderately seasonal temperatures.
In the summer, the process can be reversed so that the heat pump extracts heat from the building and transfers it to the ground. Transferring heat to colder spaces requires less energy, so the cooling efficiency of the heat pump benefits from lower ground temperatures.
The ground source heat pump uses a heat exchanger in contact with soil or groundwater to extract or dispose of heat. This component accounts for about one fifth to half of the total system cost, and will be the most complicated part to repair or replace. Correct measurement of these components is necessary to ensure long-term performance: the system's energy efficiency increases by about 4% for every degree Celsius is won through the correct size, and the balance of the underground temperature must be maintained through the proper design of the entire system.. Incorrect design can lead to system freeze after several years or very inefficient system performance; Such an accurate system design is essential for a successful system
The 3-8-foot (0.91-2.44 m) horizontal heat exchanger undergoes a seasonal temperature cycle due to the acquisition of the sun and the loss of transmission to ambient air at ground level. This temperature cycle lags behind the seasons due to thermal inertia, so the heat exchangers will harvest the heat stored by the sun a few months earlier, while weighed down in the late winter and spring, due to the accumulation of cold winters. Vertical systems within 100-500 feet (30-152 m) deep depend on heat migration from surrounding geology, unless they are replenished annually by solar recharge of soil or exhaust heat from the air conditioning system.
Some of the main design options are available for this, which are classified by fluid and layout. The direct exchange system circulates underground refrigerants, a closed loop system using an anti-freeze and water mixture, and an open-loop system using natural groundwater.
Direct exchange (DX)
Direct geothermal heat exchange pump (DX) is the oldest type of geothermal heat pump technology. The ground clutch is achieved through one loop, circulating refrigerant, in direct thermal contact with the ground (as opposed to a combination of the refrigerant loop and the water loop). The refrigerant leaves the heat pump cabinet, circulating through the loop of a copper tube buried underground, and swapping heat with the soil before returning to the pump. The name "direct exchange" refers to the heat transfer between the cooling loop and the ground without the use of an intermediate liquid. There is no direct interaction between liquid and earth; only heat transfer through the pipe wall. Direct heat exchange pumps are not to be confused with "water source heat pump" or "water heat pump" because there is no water in the ground loop. ASHRAE defines the term heat pump coupled with the ground to include closed loops and direct exchange systems, while excluding open loops.
Direct exchange systems are more efficient and have lower installation costs than closed-loop water systems. High copper thermal conductivity contributes to higher system efficiency, but the heat flow is predominantly limited by the thermal conductivity of the soil, not the pipes. The main reasons for higher efficiency are the removal of water pumps (which use electricity), the elimination of water-to-refrigerant heat exchanger (which is the source of heat loss), and most importantly, the latent heat-phase change of the coolant within the soil itself.
However, in case of leakage there is almost no risk of ground or groundwater contamination. Contrary to the geothermal system of water sources, the direct exchange system does not contain antifreeze. Thus, in the case of refrigerant leaks, the refrigerant currently used in most systems - R-410A - will soon evaporate and search for atmosphere. This is due to the low boiling point of R-410A: -51Ã, Â ° C (-60Ã, Â ° F). The R-410A refrigerant replaces the larger volume of antifreeze mixtures used in geothermal water source systems and presents no threat to the aquifer or the soil itself.
While they need more coolers and their tubes are more expensive per foot, the earth loop exchanges directly shorter than the closed water loop for a given capacity. Direct exchange systems require only 15 to 40% of pipe length and half of drilled hole diameter, and drilling or excavation costs are lower. Refrigerant loops are less tolerant of leaks than water spin because the gas can leak out through smaller imperfections. This determines the use of copper brazing pipes, although the pressure is similar to the rotation of water. Copper circles should be protected from corrosion in acid soils through the use of sacrificial anodes or other cathodic protection.
The US Environmental Protection Agency conducts field monitoring of a direct geoexchange heat pump water heater system in commercial applications. The EPA reports that the system saves 75% of the electrical energy that will be required by electrically resistant water heating units. According to the EPA, if the system is operated with capacity, it can avoid emissions of up to 7,100 pounds of CO 2 and 15 pounds NO x annually per ton of compressor capacity (or 42,600 pounds CO 2 and 90 Â £ from NO x for a typical 6 ton system).
In the Northern climate, although the temperature of the earth is cooler, so is the incoming water temperature, which allows a high-efficiency system to replace more energy than it should be required from electrical systems or fossil fuels. Any temperature above -40 ° C (-40 ° F) is sufficient to evaporate refrigerant, and direct exchange systems can harvest energy through ice.
In a very hot climate with dry soil, the addition of an additional cooling module as the second condenser in the line between the compressor and the earth loop increases efficiency and can further reduce the number of earth loops to be installed.
Closed circle
Most installed systems have two loops on the ground side: the main refrigerant loop is contained in a heat exchanger with a secondary water loop buried under the ground. Secondary loops are usually made of high density polyethylene pipes and contain a mixture of water and anti-freeze (propylene glycol, alcohol or denatured methanol). Monopropylene glycol has the most destructive potential when it may leak into the soil, and therefore the only anti-freeze allowed in soil sources in a number of European countries. After leaving the internal heat exchanger, water flows through a secondary loop outside the building to exchange heat with the soil before returning. The secondary loop is placed below the frost line where the temperature is more stable, or better submerged in water bodies if available. Systems in wet soil or in water are generally more efficient than drier soil rotation because water conducts and stores heat better than solids in sand or soil. If the soil is dry naturally, the rain hose can be buried with a ground loop to keep it wet.
The closed loop system requires a heat exchanger between the refrigerant loop and the water loop, and the pump in both loops. Some manufacturers have separate ground loop liquid pump packages, while others combine pumping and valving in heat pumps. Expansion tank and pressure relief valve can be mounted on the side of the heated liquid. Closed loop systems have lower efficiency than direct exchange systems, so they require longer and larger pipes to be placed on the ground, increasing the cost of excavation.
Closed loop tubing can be mounted horizontally as a loop field in a trench or vertical as a long U-shaped circuit in a well (see below). The size of the loop area depends on the soil type and moisture content, the average temperature of the soil and the heat loss and/or the conditioned building gain characteristics. The rough estimate of initial soil temperature is the average daily temperature for the region.
Vertical
A vertical closed-loop field consists of a pipe that runs vertically on the ground. A bore hole in the ground, usually a depth of 50 to 400 feet (15-122 m). The pipe in the hole is connected with a U-shaped cross connector at the bottom of the hole. The drill holes are generally filled with bentonite grouting that surrounds the pipe to provide a thermal connection to the ground or surrounding rock to increase heat transfer. Thermally enhanced grouts are available to enhance this heat transfer. Grout also protects ground water from contamination, and prevents artesian wells from flooding the property. Vertical circular fields are usually used when there is limited land available. The drill hole is at least 5-6 m apart and depth depending on the characteristics of the land and buildings. As an illustration, a separate house requiring a 10 kW (3 ton) heating capacity may require three 80 to 110 m (260 to 360 feet) deep drill holes. (One ton of heat is 12,000 British thermal units per hour (BTU/hour) or 3.5 kilowatts.) During the cooling season, the rise in local temperatures in the borefield is most affected by water travel on the ground. Reliable heat transfer models have been developed through drill hole samples as well as other tests.
Horizontal
The horizontal closed loop field consists of a pipe that runs horizontally on the ground. A long horizontal trench, deeper than the frost line, is dug and a U-shaped or slinky coil is placed horizontally inside the same trench. Excavations for shallow horizontal circle fields are about half the cost of vertical drilling, so this is the most commonly used layout wherever there is enough land available. As an illustration, a separate house requiring 10 kW (3 tons) of heating capacity may require three loops 120 to 180 m (390 to 590 ft) long NPS 3/4 (DN 20) or NPS = 1.25 (DN 32) polyethylene tubing at depths of 1 to 2 m (3.3 to 6.6 feet).
The depth at which the loop is placed significantly affects the energy consumption of the heat pump in two opposite ways: shallow loops tend to indirectly absorb more heat from the sun, which is helpful, especially when the soil is still cold after a long winter. On the other hand, shallow loops are also cooled much more easily by weather changes, especially during long winters, when heating peak demand. Often, the second effect is much larger than the first, leading to higher operating costs for shallower soil loops. This problem can be reduced by increasing the depth and length of piping, thereby significantly increasing installation costs. However, such expenditures may be considered feasible, as they may result in lower operating costs. Recent studies have shown that utilizing a non-homogeneous soil profile with a low conductive layer over a soil pipe can help reduce the adverse impact of shallow pipe funnel depths. An intermediate blanket with lower conductivity than the surrounding soil profile shows the potential for increasing the energy extraction rate from soil to as high as 17% for cold climates and about 5-6% for relatively moderate climates.
The closed loop field (also called a circle) is a horizontal closed-loop type in which the pipes overlap (not the recommended method). The easiest way to imagine the slinky plane is to imagine holding the slinky at the top and bottom with your hand and then moving your hand in the opposite direction. A plane of slinky circle is used if there is not enough space for the actual horizontal system, but still allows for easy installation. Instead of using a straight pipe, the slinky coil using an overlapping flat loop is arranged horizontally along the bottom of the wide trench. Depending on the soil, climates and the fraction of the heat pump run, the slinky coil trench can reach two-thirds shorter than the traditional horizontal loop ditch. The ground loop of the Slinky coil is essentially a more economical and space-saving version of the horizontal ground loop.
Radial or directional drilling
As an alternative to excavation, the loop can be placed by mini-horizontal drilling (mini-HDD). This technique can install pipes under the yard, driveway, garden or other buildings without disturbing them, at a cost of trenching and drilling vertical. This system is also different from horizontal & amp; vertical drilling as a loop mounted from one central space, further reducing the required ground space. Radial drilling is often retroactively installed (after the property is built) due to the nature of the equipment used and the ability to dig under existing construction.
Pond
Closed loop pools are not common because they depend on proximity to water bodies, where open loop systems are usually preferred. A pool loop may be advantageous where poor water quality blocks open loops, or where the system's heat load is small. The pool loop consists of a pipe roll similar to the slinky circle attached to the frame and located at the bottom of the pool or a proper sized water source.
Open loop
In open loop systems (also called ground water pumps), the secondary loop pumps natural water from a well or water body into a heat exchanger inside the heat pump. ASHRAE open loop system calls ground water heat pump or surface water heat pump , depending on the source. Heat is extracted or added by the primary cooling loop, and water is returned to a separate injection well, irrigation ditch, tile plane or water body. Supply and return lines should be placed far enough apart to ensure the filling of the heat source. Due to uncontrolled water chemistry, appliances may need to be protected from corrosion by using different metals in heat exchangers and pumps. Limescale may contaminate the system from time to time and require periodic acid cleaning. This is much more a problem with the cooling system than the heating system. Also, because fouling reduces the flow of natural water, it becomes difficult for heat pumps to exchange building heat with ground water. If water contains high levels of salt, minerals, iron or hydrogen sulfide bacteria, closed loop systems are usually preferred.
Cooling the lake water in using a process similar to an open loop for cooling and air conditioning. Open loop systems using groundwater are usually more efficient than closed systems because they are better combined with soil temperatures. The closed loop system, when compared, must transfer heat through an extra layer of pipe walls and impurities.
More and more jurisdictions have banned open-loop systems that flow to the surface because these can dry up the aquifer or contaminate the well. This forces the use of a more environmentally friendly injection well or closed-loop system.
The column stands well
A good standing column system is a special type of open-loop system. The water is drawn from the bottom of a deep stone well, passes through the heat pump, and returns to the top of the well, where the journey downwards exchanges heat with the surrounding bedrock. The choice of standing column well systems is often dictated where there is a bedrock near the surface and limited surface area is available. Standing columns are usually unsuitable in locations where the geology is mostly clay, silt, or sand. If the bedrock is deeper than 200 feet (61 m) from the surface, the cost of the casing to cover the cover layer may be a barrier.
A standing double column system can support large structures in urban or rural applications. The well-established column method is also popular in residential and small commercial applications. There are many successful applications of varying sizes and numbers in many areas of New York City, and it is also the most common application in the state of New England. This type of ground source system has several benefits of heat storage, where heat is rejected from the building and the temperature of the well is raised, for that reason, during the summer the cooling can then be harvested for heating in the winter, thereby increasing the efficiency of the heat pump system. As the closed-loop system, the size of the column system stands very important in reference to heat loss and the advantages of existing buildings. As an actual heat exchange with bedrock, using water as a transfer medium, a large amount of production capacity (flow of water from wells) is not required for standing column systems to work. However, if there is sufficient water production, then the thermal capacity of the well system can be increased by removing a small portion of the system flow during peak summer and winter.
Since this is basically a water pumping system, well-established column designs require critical consideration to obtain peak operating efficiency. Should the column design stand well abused, leaving a critical cover valve for example, the result could be an extreme loss in efficiency and thus cause the operational cost to be higher than anticipated.
Building distribution
Heat pumps are central units that become heating and cooling plants for buildings. Some models may include room heating, cooling chambers, (heating of air-conditioned spaces, hydronic systems and/or radiant heating systems), preheating of domestic water or swimming pools (via desuperheater function), hot water demand, and ice melting in all in one tool with various options with respect to controls, staging and zone controls. Heat can be brought to its final use by circulation of water or forced air. Almost all types of heat pumps are produced for commercial and residential applications.
Liquid-to-air pumps (also called air-to-air ) force air, and are most commonly used to replace forced air furnaces and central air-conditioning systems. There are variations that allow for split systems, high speed systems, and ductless systems. Heat pumps can not achieve high fluid temperatures like conventional furnaces, so they require higher air volume flow rates to compensate. When retrofit residence, existing channel work may have to be enlarged to reduce noise from higher airflow.
Liquid-to-water heat pump (also called water-to-water ) is a hydronic system that uses water to carry heating or cooling through buildings. Systems such as radiant under-floor heating, baseboard radiators, conventional cast iron radiators will use liquid-to-water heat pumps. This heat pump is preferred for heating the pool or pre-hot domestic hot water. The heat pump can only heat water up to about 50 ° C (122 ° F) efficiently, while the boiler typically reaches 65-95 ° C (149-203 ° F). Legacy radiators designed for this higher temperature may need to be doubled in the amount of retrofit at home. Hot water tanks will still be needed to raise the water temperature above the maximum heat pump, but pre-heating will save 25-50% of the cost of hot water.
The ground source heat pump is ideal for under floor heating and basal radiators that require only 40A, 104 ° F (104Ã, Â ° F) warm temperatures to work properly. So they are ideal for open plan offices. Using a large surface such as a floor, compared to a radiator, distributes heat more uniformly and allows for lower water temperatures. Wood floor or carpet coverings narrow this effect because the thermal transfer efficiency of these materials is lower than the stone floor (tile, concrete). Under floor piping, ceiling or radiator wall can also be used for cooling in dry climates, even though the temperature of the circulating water should be above the dew point to ensure that atmospheric moisture does not condense on the radiator.
Combined heat pumps are available that can produce forced air and water circulation simultaneously and individually. This system is mostly used for homes that have a combination of air conditioning and fluid requirements, such as central air conditioning and pool heating.
Seasonal thermal storage
The efficiency of the ground source heat pump can be greatly enhanced by the use of seasonal heat energy storage and intheral heat transfer. Heat captured and stored in summer thermal banks can be efficiently picked up in winter. The efficiency of thermal storage increases with scale, so this advantage is most significant in commercial or district heating systems.
Geosolar combisystems have been used to heat and cool greenhouses using aquifers for thermal storage. In summer, the greenhouse is cooled with cold ground water. It heats up water in aquifers that can be a warm source for warming in the winter. Combination of cold and hot storage with heat pump can be combined with water/humidity arrangement. These principles are used to provide renewable heat and renewable cooling for all types of buildings.
Also the efficiency of existing small heat pump installation can be improved by adding large, cheap, and water-filled solar collectors. These can be integrated into a parking lot that needs to be overhauled, or on a wall or roof construction by placing an inch of PE pipe to the outer layer.
Thermal efficiency
The heat efficiency of the heat pump should take into account the efficiency of power generation and transmission, usually about 30%. Because the heat pump drives three to five times more heat energy than the electricity it consumes, the total energy output is much larger than the electrical input. This results in a cleaner thermal efficiency greater than 300% compared to 100% efficient electrical heat radiation. Traditional burning stoves and electric heaters can never exceed 100% efficiency.
Geothermal heat pumps can reduce energy consumption - and emissions of air pollution accordingly - up to 44% compared to air source heat pumps and up to 72% compared to heating of electrical resistance with standard AC equipment.
The dependence of clean thermal efficiency on electrical infrastructure tends to be an unnecessary complication for the consumer and does not apply to hydroelectric power, so the heat pump performance is usually expressed as the ratio of heating output or heat transfer to the electrical input. Cooling performance is usually expressed in BTU/hour/watt units as the energy efficiency ratio (EER), while heating performance is usually reduced to a dimensionless unit as a performance coefficient (COP). The conversion factor is 3.41 BTU/hr/watt. Performance is affected by all installed system components, including soil conditions, ground-linked heat exchangers, heat pumps and building distribution, but is largely determined by "lifting" between the input temperature and the output temperature.
In order to compare the heat pump equipment to each other, regardless of other system components, some standard test conditions have been established by the American Refrigerant Institute (ARI) and recently by the International Organization for Standardization. Standard ARI 330 ranking is intended for source heat pump loop, and assuming the water temperature secondary loop 25 Ã, Â ° C (77A, Â ° F) for AC and 0 Ã, Â ° C (32A, Â ° F) for heating. This temperature is typical of installations in the northern US. Standard ARI 325 ranking is intended for open-loop ground-source heat pumps, and includes two sets of rankings for the temperature of the groundwater 10 Ã, Â ° C (50Ã, Â ° F) and 21A, Â ° C (70A, Â ° F). ARI 325 allocates more electricity to pump water than ARI 330. None of these standards are attempting to take into account seasonal variations. Standard ARI 870 ratings are intended for the direct exchange of heat pump heat pumps. ASHRAE switched to ISO 13256-1 in 2001, replacing ARI 320, 325 and 330. The new ISO standard yielded a slightly higher rating because it no longer budgeted electricity for water pumps.
Efficient compressors, variable speed compressors and larger heat exchangers all contribute to the efficiency of heat pumps. The residential ground source heat pump on the market today has a COP standard ranging from 2.4 to 5.0 and EER ranging from 10.6 to 30. To qualify for the Energy Star label, the heat pump must meet a certain minimum COP and EER rating on typed earth heat exchangers. For closed loop systems, COP heating ISO 13256-1 should be 3.3 or greater and EER cooler should be 14.1 or greater.
The actual installation conditions can produce better or worse efficiency than standard test conditions. COP increases with a lower temperature difference between the input and output of the heat pump, so that soil temperature stability is important. If the loop or water pump field is too small, the addition or heat dissipation can push the ground temperature beyond the standard test conditions, and the performance will decrease. Similarly, a small blower allows the plenum coil to overheat and degrade performance.
Soils without the addition or reduction of artificial heat and at a depth of several meters or more remain at a relatively constant temperature throughout the year. This temperature is approximately equal to the average annual air temperature of the selected site, usually 7-12 ° C (45-54 ° F) at a depth of 6 meters (20 feet) in the northern United States. As this temperature remains more constant than the air temperature throughout the season, the geothermal heat pump works with much greater efficiency during extreme temperatures than air conditioning and air source heat pumps.
ARI standards 210 and 240 define Seasonal Energy Efficiency Ratios (SEERs) and Seasonal Heating Performance Factors (HSPF) to account for the impact of seasonal variations on air source heat pumps. These numbers are usually not applicable and should not be compared to the rating of the ground source heat pump. However, the Canadian Natural Resources has adapted this approach to calculate seasonally tailored HSPF specifically for heat pumps sourced directly in Canada. NRC HSPF ranges from 8.7 to 12.8 BTU/hr/watt (2.6 to 3.8 in non-dimensional factors, or 255% to 375% efficiency of seasonal average use of electricity) for the most densely populated areas Canada. When combined with thermal electrical efficiency, this corresponds to the average net thermal efficiency of 100% to 150%.
Environmental impact
The US Environmental Protection Agency (EPA) has referred to the ground source heat pump as an energy-efficient, environmentally friendly, and cost-effective space-conditioning system available. The heat pumps offer significant emission reduction potential, especially where they are used for heating and cooling and where electricity is generated from renewable resources.
Soil pumps from ground sources have unmatched thermal efficiency and generate zero emissions locally, but their electricity supply includes components with high greenhouse gas emissions, unless the owners have opted for 100% renewable energy supply. Therefore their environmental impact depends on the characteristics of available power supplies and alternatives.
GHG emission savings from conventional conventional heating pump heat can be calculated based on the following formula:
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- HL = beban panas musiman? 80 GJ/tahun untuk rumah terpisah modern di AS bagian utara
- FI = intensitas emisi dari bahan bakar = 50A kg (CO 2 )/GJ untuk gas alam, 73 untuk minyak pemanas, 0 sampai 100% terbarukan som energi angin, air, fotovoltaik atau panas matahari
- AFUE = efisiensi toggle? 95% untuk token of condensate modern
- COP = koefisien atau kinerja panas pump? 3,2 disesuaikan musiman untuk pump pan AS bagian utara
- EI = intensitas emisi listrik? 200-800 tons (CO 2 )/GWh, tergantung falls wilayah
Hot-heat heat pumps always produce less greenhouse gas than air-conditioning, oil furnaces, and electric heaters, but natural gas furnaces can compete depending on the intensity of greenhouse gases from local power supplies. In countries such as Canada and Russia with low emitting electrical infrastructure, housing heat pumps can save 5 tons of carbon dioxide per year relative to an oil furnace, or about as much as taking an average passenger car off the road. But in cities like Beijing or Pittsburgh that rely heavily on coal for electricity production, heat pumps can produce 1 or 2 tons more carbon dioxide emissions than natural gas furnaces. For areas not served by utility natural gas infrastructure, however, there is no better alternative.
The liquid used in closed loops may be designed to be biodegradable and non-toxic, but the refrigerant used in heat pump cabinets and in the direct exchange loop, to date, chlorodifluoromethane, which is an ozone-depleting substance. Although not harmful when contained, leakage and improper end-of-life waste contribute to enlarging the ozone hole. For new construction, this refrigerant is being removed for the sake of environmentally friendly but powerful greenhouse gas R410A. EcoCute water heater is an air-fed calorie pump that uses carbon dioxide as its working fluid instead of chlorofluorocarbons. Open loop systems (ie those that attract groundwater as opposed to closed-loop systems using drill-hole heat exchangers) need to be balanced by re-input of the spent water. This prevents aquifer depletion and contamination of soil or surface water with salt water or other compounds from underground.
Prior to drilling, underground geology needs to be understood, and drillers need to be prepared to close drill holes, including preventing water penetration between layers. An unfortunate example is the geothermal heating project in Staufen im Breisgau, Germany which seems to be the cause of major damage to the historic buildings there. In 2008, the city center was reported to have increased 12 cm, after initially sinking a few millimeters. The boring knocks the natural pressurized aquifer, and through this water drill hole enters the anhydrite layer, which expands when wet as it forms gypsum. The swelling will stop when the anhydrite fully reacts, and urban center reconstruction "is unwise until the appointment stops." In 2010 the drill hole closure has not been completed. In 2010, some parts of the city have climbed 30 cm.
Heavy ground-based pumping technology, such as building orientation, is a natural building technique (bioclimate building).
Economy
The ground source heat pump is characterized by high capital costs and low operational costs compared to other HVAC systems. Their overall economic benefits are heavily dependent on the relative costs of electricity and fuel, which vary greatly over time and around the world. Based on recent prices, heat pumps directly sourced currently have lower operating costs than any other conventional heating source in almost anywhere in the world. Natural gas is the only fuel with competitive operating costs, and only in a handful of countries where the price is very cheap, or where electricity is very expensive. In general, homeowners can save from 20% to 60% every year on utilities by switching from a regular system to a ground-source system.
The cost of capital and system life has received fewer studies to date, and return on investment varies considerably. The latest data from the 2011-2012 incentive payment analysis in the state of Maryland shows the average cost of a housing system of $ 1.90 per watt, or about $ 26,700 for a typical home system (4 tons). An older study found total installed costs for systems with a 10 kW (3 ton) thermal capacity for separate rural settlements in the US averaging $ 8,000- $ 9000 in 1995 US dollars. The more recent study found the average cost of $ 14,000 in 2008 US dollars for the same size system. The US Department of Energy estimates the $ 7500 price on its website, last updated in 2008. One Canadian source puts prices in the $ 30,000- $ 34,000 Canadian dollar range. Rapid escalation in system pricing has been accompanied by a rapid increase in efficiency and reliability. Capital costs are found to be useful from economies of scale, especially for open loop systems, making them more cost effective for larger commercial buildings and harsher climates. The initial cost could be two to five times that of conventional heating systems in most residential, new or existing construction applications. In retrofits, installation costs are influenced by the size of the living room, the age of the house, the insulation characteristics, the geology of the area, and the location of the property. Appropriate channel system design and mechanical air exchange should be considered in the initial system cost.
The cost of capital can be offset by government subsidies; for example, Ontario offers $ 7000 for a housing system installed in fiscal 2009. Some power companies offer special rates for customers who install heat-sourced heat pumps to heat or cool their buildings. Where power plants have bigger loads during the summer and idle capacity in the winter, this increases electricity sales during the winter months. The heat pump also lowers the peak load during the summer due to increased heat pump efficiency, thus avoiding the construction of expensive new power plants. For the same reason, other utility companies have begun paying for the installation of heat-pump heat pumps at customers' homes. They lease the system to their customers for a monthly fee, with overall net savings to customers.
System life is longer than conventional heating and cooling systems. Good data on system age is not yet available because the technology is too new, but many early systems are still operating today after 25-30 years with regular maintenance. Most areas of the loop have a guarantee for 25 to 50 years and are expected to last at least 50 to 200 years. Heat pumps are sourced from the ground using electricity to heat the house. Higher investments over conventional oil, propane or electric systems can be restored in energy savings within 2-10 years for residential systems in the US. When compared to natural gas systems, the payback period may be much longer or nonexistent. The payback period for larger commercial systems in the US is 1-5 years, even when compared to natural gas. In addition, since geothermal heat pumps usually do not have an outer compressor or cooling tower, the risk of vandalism is reduced or eliminated, potentially extending the system life.
The ground source heat pump is recognized as one of the most efficient heating and cooling systems on the market. They are often the second most cost-effective solution in extreme climates (after co-generation), despite a reduction in thermal efficiency due to soil temperatures. (The soil sources are warmer in climates that require strong air conditioning, and are cooler in climates requiring strong heating.)
The cost of maintaining a commercial system in the US historically between $ 0.11 to $ 0.22 per m 2 per year in dollars in 1996, is much smaller than the average $ 0.54 per m 2 per year for conventional HVAC Systems.
Governments that promote renewable energy are likely to offer incentives to consumers (housing), or industrial markets. For example, in the United States, incentives are offered at both state and federal government levels. In the UK the Renewable Heat Incentives provide a financial incentive to generate renewable heat based on meter readings every year for 20 years for commercial buildings. Domestic renewable hot incentives will be introduced in Spring 2014 for seven years and based on the heat considered.
Installation
Due to the technical knowledge and equipment required to properly design and measure the system (and install piping if hot fusion is required), the installation of the GSHP system requires professional service. Some installers have published a real-time view of system performance in the online community of recent residential installations. The International Geothermal Heat Pump Association (IGSHPA), Geothermal Exchange Organization (GEO), GeoExchange Canada Coalition and the Soil Source Heat Pump Association maintain a list of qualified installers in the US, Canada and the UK. Furthermore, a detailed analysis of the thermal conductivity of Soil for horizontal systems and the formation of thermal conductivity for vertical systems will generally result in more accurate design systems with higher efficiency.
See also
- Ingestion heat pump
- The combined geothermal heat exchanger
- Thermal cooling of the sun
- Termosiphon
- Heat that can be updated
- International Soil Source Pump Association
- Geothermal heating and cooling list
References
External links
- Geothermal Heat Pump (EERE/USDOE).
- Cost calculation
- Thermal Heat Pump Consortium
- International Soil Source Pump Association
- Association of Heat Pump Source of Land (GSHPA)
Source of the article : Wikipedia
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