The Geothermal Heat Pumps Engineering Essay

The large image in the energy field has ever been a concern chiefly for authoritiess and for big administrations. Homeowners have normally followed the energy schemes imposed by the governments and non the other manner around. Now, energy independency is non limited to a province, but it is a end accomplishable for families besides.

One of the little participants in the field of renewable energy, the geothermic heat pumps had been around for more than four decennaries, but they were ne’er regarded with great involvement ( 7 ) . Over the past 10 old ages, the one-year addition was about of 10 % in more than 30 states around the universe ( 12 ) . Unlike other geothermic systems, this one can be used widely, independently of a heat beginning, a H2O reservoir or supply or a cap stone ( 4 ) . It can make so because in the procedure of warming or chilling, it uses the “ comparatively changeless temperature of the Earth ” ( 18 ) from under an mean residential batch, salvaging up to 70 % of the energy used. The chart presents the typical residential energy usage in the UK ( 6 ) . The nest eggs that can be achieved by utilizing GHP systems on big graduated table are of non to be overlooked.

Geothermal heat pumps merely move, with the aid of electricity, the “ free energy ” ( 9 ) from the land into the house. Practically, depending on the season, it uses the land as a heat beginning to pump heat out of it or it uses it like a heat sink for chilling. In add-on, besides being an economical energy beginning, the geo-exchange system besides reduces the air pollution. This type of clean energy is a really good replacing for warming and chilling with traditional methods and as long the surface of the Earth is heated by the Sun, it is a uninterrupted beginning. Compared with traditional air-source heat pumps ( 175-250 % ) , the GHP reaches reasonably high-efficiency ( 300-600 % ) ( 20 ) . Another advantages in comparing with the air-pumps is the decreased degree of noise, the longer life anticipation and the independency of the outside temperature. Besides residential finishs, this system is besides designated for big commercial and societal edifices.

Technology issues – how does it work?

As in most of the instances, the Sun is the beginning of energy. The figure from page 2, presents the diffraction of the Sun heat into the ambiance, demoing that the Earth ‘s surface benefits of about half of it ( 17 ) . So in most of the seasonal parts of the universe, the belowground temperatures remains between 7A°C and 21A°C ( 20 ) . Heat pump systems intending is to reap this heat. Fortunately, the system works both ways, utilizing “ the Earth as a beginning of heat in the winter and an efficient topographic point to reject heat in summer ” ( 17 ) . It is besides problematic if this is a geothermic beginning of energy, as it shops heat from the Sun and does n’t utilize the energy below ( 5 ) .

There are three types of GHPs that can be used in residential, commercial and societal edifices: closed cringle ( land coupled ) , unfastened cringle ( groundwater ) and lake or pool cringle ( surface H2O ) systems. When taking a GHP, it must be taken into consideration factors like the clime, the dirt conditions, the surface of land available and the local industry of GHP. Due to the easiness of installing, the horizontal cringles are the most used method, taking over more than half of the market. The perpendicular cringle systems are estimated at approximately 35 % , while the pool and other methods are of small impact because of their dependance of H2O beginnings ( 7 ) .

There are three chief parts that together organize a GHP system: a cringle ( earth connexion ) , the heat pump and the interior warming or chilling distribution system ( 9 ) . Basically, the system works like a modified icebox with a dual exchange fluid way that allows warming and besides chilling.

Heat Pump

The heat pump is “ the basic edifice block of the GSHP system ” ( 19 ) . Most of the GHP systems use a mixture of H2O and antifreeze for reassigning the heat between the Earth and the primary heat money changer ( evaporator ) . With the aid of the liquid cold refrigerant colder than the heat transportation fluid, the heat is transferred into the refrigerant. As the refrigerant evaporates its volume additions, but its temperature is lower than required. To decide this, a compressor is so able to supercharge the gaseous refrigerant and as a consequence the temperature increases. A 2nd heat money changer ( capacitor ) is taking the heated pressurized end product of the compressor ( 19 ) .

“ The Refrigeration Cycle ( Heating Mode ) of a Typical Packaged Heat Pump Unit. “ ( 19 )

There are two types of pump: “ water-to-air ” and “ water-to-water ” . In the first instance, a fan blows cold air which is heated with the aid of the capacitor and so pushed into the edifice as hot air. For “ water-to-water ” heat pumps the lone difference is that het H2O flows through the capacitor alternatively of air. The refrigerant so condenses because of the loss of heat. With the aid of the enlargement valve, the refrigerant flows through the same rhythm, as described above, over and over once more ( 21 ) . In order for the procedure to go on, the fluid in the cringle which has transferred the heat to the above system goes back into the Earth to absorb more energy ( 16 ) .

Because heat will ever flux from hot to cold, for the chilling procedure the flow will happen of course and the pump is merely used to guarantee “ the rate of the heat flow ” ( 19 ) . With the aid of a valve, the contrary flow is enabled. The flow rate is correlated with the difference of temperature. As this difference between the belowground piping and the edifice is higher, the flow transportation rate is besides higher ( 19 ) . From proficient point of position, when the contrary procedure occurs, the functions of the capacitor and of the evaporator are switched. “ The Earth connection-to-refrigerant money changer becomes the capacitor ” and “ the refrigerant-to-air money changer becomes the evaporator ” ( 19 ) .

The “ desuperheater ” presented in the figure from page 4, when nowadays, is used to supply domestic hot H2O. In order to salvage some heat that would hold been lost at the capacitor, the extra heat generated by the tight gas is used to heat H2O which is pumped through a spiral. This is done more expeditiously in summertime, when the pump is on chilling manner, but some GHP can supply domestic het H2O all twelvemonth long.

The Loop

The unfastened or closed cringle is besides known as the “ the liquid heat exchange medium ” ( 21 ) . Its dimensions are of import as it needs to replenish itself with a proper sum of energy in order to be able to fulfill the heat/cooling demand. The lone manner to reload it is by a longer contact of the mix fluid with the dirt and the lone manner to maximise this is by put ining a larger cringle for your estimated demand. When taking a type of system, the contractor/owner must take into consideration a series of factors as: the type of dirt, the deepness of the cringle, the clime, the snow bed in winter clip and the size of the pipes. The mixture of antifreeze and H2O circulated through the high denseness polythene canals ( cringle ) and through the heat pump must ne’er come in direct contact with the dirt. As there are many types of cringles as presented before, the followers will be discussed: horizontally, vertically, unfastened cringles and pond/lake system.

Because of the easiness to put in it, the horizontal cringle system is the cheapest of them all. It normally requires a big country, but is really good suited for residential edifices. The cringles are placed horizontally, in trenches from 1.5 to 3m broad and with a deepness between 2 and 3m. In order for the system to supply 1KW of warming or chilling capacity, approximately 35 to 55m of grapevines is needed. For an mean house of 150sqm, the demand for grapevine country is in between 300 to 700sqm. In order for this to be possible, different pipe layouts, that concentrate pipes in the trench country, have been developed. These are chosen depending on the warming and chilling demand, on the deepness of the cringle, on the dirt, on the efficiency of the heat pump and once more, of the clime ( 9 ) ( 16 ) ( 19 ) ( 21 ) ( 11 ) .

Vertical cringles are more hard to put in than the old 1s, but because they require a comparative little surface, they are suited for residential and commercial applications larger than in the first class. Two high denseness polythene canals are inserted into each drilled hole and so grouted to forestall any infiltration from the surface and to guarantee a proper contact between the pipe and the dirt. They are connected at the terminal by a U shaped pipe to guarantee the uninterrupted flow of the fluid and at the top are linked by horizontal pipes. Vertical cringles can be placed down to 150m in deepness and the canal needed is up to 32mm in diameter, but the design is custom made for each single edifice depending merely by the dirt type. For the same mean lodging surface of 150sqm, an country of merely 9sqm is used to supply the necessary heat. However, the monetary value of this system is 4 times more than of horizontal cringle ( 9 ) ( 16 ) ( 19 ) ( 21 ) ( 11 ) .

Lake or pool cringles are reliable on a nearby beginning of unfastened H2O ( lake or pool ) . Besides, a minimal deepness of 2-2.5m of the H2O is required to protect the cringle from ice during winter and the pool has to be big plenty. This system is really efficient and economical because it implies H2O to H2O heat transportation and because no or minimal boring is needed. With particular steps taken to protect from tidal and moving ridge, the ocean H2O can besides be used with this method ( 9 ) ( 16 ) ( 19 ) ( 21 ) ( 11 ) .

Open cringle system uses land H2O as a replacing for the antifreeze H2O mixture. Using H2O from a good as a supply, this is pumped straight through the heat money changer. Typically, after the heat is transferred, the H2O is pumped back into the land utilizing an injection good ( return good ) . Bing the simplest GHP systems it was the fist one to be commercially used. There are, of class, many issues refering the groundwater handiness, the deepness from which this can be taken economically or the influence of a well on another close one. Normally, local ordinances are in topographic point to react to these inquiries. Taking into history the same mean lodging surface of 150sqm, this will necessitate between 20.000 and 30.000 cubic decimeter of H2O per twelvemonth, so a dependable clean aquifer H2O supply is needed ( 9 ) ( 16 ) ( 19 ) ( 21 ) ( 11 ) .

The Distribution System

There is no difference between the distribution system used with a GHP and a conventional warming system. Its intent is to present the heat to the edifice or to take away the heat from it. However, this system must be designed to be compatible with the heat pump, otherwise the pump may be overloaded or parts of the edifice may be unequal heated or cooled. To avoid any jobs there must be a proper design made sing the sizes of the canal, the equal air flow, the cost of the distribution system, the noise comfort and the care cost ( 9 ) .

Economicss – how much?

There are different systems available on the market and the monetary value depends on single fortunes. However a approximately estimate for the international market places the merchandise up to 15.000? ( 23.000 $ ) . The monetary value is rather high compared with traditional methods like electric furnace or high-efficiency propane furnace with air conditioning, but the comfort is increased and the care cost reduced. The ratio of heat – electricity used in the procedure is 4 to 1 ( 18 ) and the overall energy nest eggs are between 30 % and 60 % . The economic sciences of the system comes chiefly from the deficiency of fuel used. Without taking into consideration any authorities subsidies, the payback period ranges between & lt ; 10 to 20 old ages. Factors like clime, dirt conditions, the type of cringle, available inducements make this economic recovery hard to established ( 20 ) . In order to acquire the image right, a life rhythm analysis would helpful, but this is non an easy undertaking. To finish the treatment on economic sciences other things must besides be taken into history: the estimated life anticipation of the heat pump ( up to 23 old ages ) , the Earth loop replacing ( 50-75 old ages ) and the rising prices of the fuel monetary value ( 9 ) ( 20 ) . In the graph from page 7, Earth Energy ( a GHP company ) compares the monetary value of warming ( kWh ) for all the systems presently used in UK ( 6 ) .

Environmental concerns – why is it renewable?

As stated before, the geothermic heat pump does non bring forth heat ; it uses electricity to transports it from the dirt into the edifice. The heat is really “ renewable solar heat stored in the land ” ( 9 ) . To be cognizant of the impact on the environment with concern on the efficiency, the GHP system must be compared with other beginnings of heating/cooling like oil and gas warming systems.

The figure above ( 8 ) presents the GHG emanations decreases of GHP system for a warming burden of 80GJ. The first two graphs refer to natural gas and warming oil and to the GHG emanations in comparing with a GHP system. The addition in the efficiency of the heat pump has ever a positive consequence for the environment. As this system operates at approximately 300 % -600 % efficiency, it is obvious that it is more preferable. In the instance of electric warming, it depends really much on how the electricity is produced and if it implies C02 emanations or non. In decision of this comparing, in all scenarios the decrease of the GHG is higher by utilizing a heat pump and the larger the demand of heat, the larger the possible decrease. Therefore, it has a really low negative impact on the environment ( 8 ) .


It is proper that in the terminal, the benefits of this engineering should be summarized: on site renewable energy for residential and commercial applications, low operation and care cost, low GHG emanations, aesthetically pleasant location ( no visibleness ) , no noise, no burning gases, no fuel and fuel storage necessity, no fire jeopardy, no demand for be aftering permission for closed cringles, available 24 hours, 7 yearss a hebdomad and long-run dependability. The lone negative facet is the trouble and monetary value of initial installing, but every bit presented before, on long term it becomes a executable investing ( 6 ) ( 11 ) .