30-09-2013, 02:52 PM
A Seminar Report On GEOTHERMAL HEAT PUMP
GEOTHERMAL HEAT .docx (Size: 1.15 MB / Downloads: 127)
ABSTRACT
To address energy problems in the very near future, especially in the area of heating and air-conditioning of building structures, it is proposed to design a geothermal energy system with emphasis on the residential application of heating and cooling. The proposed geothermal energy system is basically a ground heat pump intended to replace currently used piping systems buried in extension ground trenches.
System basically consist of 3 simple equipments that are a grounded connection loop, a liquid source heat pump and a conventional duct system. The system is equally efficient in both summer and winter seasons. In summer system becomes a refrigeration unit while the same becomes a heat pump unit. Ground source heat pump system can provide heating, cooling, hot water and sound permafrost foundations with decreased maintenance, decreased space needs and reduced operating cost however the cost of installation of the system is high. Ground-source heat pumps have unsurpassed thermal efficiencies and produce zero emissions locally, but their electricity supply almost always includes components with high greenhouse gas emissions.
INTRODUCTION
Geothermal heat pumps are also known by a variety of other names, including geoexchange, earth-coupled, earth energy or water-source heat pumps. Ground source heat pumps harvest a combination of geothermal power and heat from the sun when heating, but work against these heat sources when used for air conditioning.
Heat pumps can transfer heat from a cool space to a warm space, against the natural direction of flow, or they can enhance the natural flow of heat from a warm area to a cool one. Unlike an air source heat pump, which transfers heat to or from the outside air, a ground source heat pump exchanges heat with the ground. This is much more energy-efficient because underground temperatures are more stable than air temperatures through the year. Seasonal variations drop off with depth and disappear below seven meters due to thermal inertia. . A ground source heat pump extracts ground heat in the winter (for heating) and transfers heat back into the ground in the summer (for cooling). Some systems are designed to operate in one mode only, heating or cooling, depending on climate.
The setup costs are higher than for conventional systems, but the difference is usually returned in energy savings in 3 to 10 years. System life is estimated at 25 years for inside components and 50+ years for the ground loop.
HISTORY
The heat pump was described by Lord Kelvin in 1853 and developed by Peter Ritter von Rittinger in 1855. After experimenting with a freezer, Robert C. Webber built the first direct exchange ground-source heat pump in the late 1940s. The first successful commercial project was installed in the Commonwealth Building (Portland, Oregon) in 1946, and has been designated a National Historic Mechanical Engineering Landmark by ASME. The technology became popular in Sweden in the 1970s, and has been growing slowly in worldwide acceptance since then.
As of 2004, there are over a million units installed worldwide providing 12 GW of thermal capacity. Each year, about 80,000 units are installed in the USA.
SITE SELECTION FOR GHP
Following are the various factors on which site selection for GHP depends:
GEOLOGY:
Factors such as the composition and properties of your soil and rock (which can affect heat transfer rates) require consideration when designing a ground loop. For example, soil with good heat transfer properties requires less piping to gather a certain amount of heat than soil with poor heat transfer properties. The amount of soil available contributes to system design as well — system suppliers in areas with extensive hard rock or soil too shallow to trench may install vertical ground loops instead of horizontal loops.
HYDROLOGY:
Ground or surface water availability also plays a part in deciding what type of ground loop to use. Depending on factors such as depth, volume, and water quality, bodies of surface water can be used as a source of water for an open-loop system, or as a repository for coils of piping in a closed-loop system. Ground water can also be used as a source for open-loop systems, provided the water quality is suitable and all ground water discharge regulations are met.
Before you purchase an open-loop system, you will want to be sure your system supplier/installer has fully investigated your site's hydrology, so you can avoid potential problems such as aquifer depletion and groundwater contamination. Antifreeze fluids circulated through closed-loop systems generally pose little to no environmental hazard.
LAND AVAILABILITY:
The amount and layout of your land, your landscaping, and the location of underground utilities or sprinkler systems also contribute to your system design. Horizontal ground loops (generally the most economical) are typically used for newly constructed buildings with sufficient land. Vertical installations or more compact horizontal "Slinky™" installations are often used for existing buildings because they minimize the disturbance to the landscape.
ECONOMICS OF GEOTHERMAL HEAT PUMPS
Geothermal heat pumps save money in operating and maintenance costs. While the initial purchase price of a residential GHP system is often higher than that of a comparable gas-fired furnace and central air-conditioning system, it is more efficient, thereby saving money every month. For further savings, GHPs equipped with a device called a "desuperheater" can heat the household water.
CONCLUSION
Geothermal (ground-source) heat pumps are not a new technology ,developed by Lord Kelvin in 1852.GHP gained popularity in the 1960s and 70s and now growing atleast 20%/yr. Its great advantage is that it works by concentrating naturally existing heat, rather than by producing heat through combustion of fossil fuels thus proves highly economic in the areas of high alternate fuel cost. These are best suited for large building loads, such as schools, commercial buildings, etc. and for new construction, as retrofits are expensive. Also they can serve well in both the winter and summer seasons with a high efficiency but their cost of installation is very high however the running cost is low.