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A Review of the Advancements in Geothermal Heating and Cooling System

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The increasing demand for energy and the depleting fossil fuels have fuelled explorations in new frontiers of Renewable Energy Technology. Geothermal Heating and Cooling is a new advancement in HVAC industry of India. It uses earth’s heat for space heating and cooling with the use of Heat Pump systems, saving up to 51% electricity consumption in HVAC, and reduced CO2 emissions. The main prospects of Geothermal Energy are longer equipment life and lower operating costs. This paper reviews the recent advancements in Geothermal Heating and Cooling System.
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JoAEST (2017) 1-5 © STM Journals 2017. All Rights Reserved Page 1
Journal of Alternate Energy Sources and Technologies
ISSN: 2230-7982 (Online), ISSN: 2321-5186 (Print)
Volume 8, Issue 1
www.stmjournals.com
A Review of the Advancements in Geothermal Heating
and Cooling System
Nimish Dhepe, Raahul Krishna*
Department of Mechanical Engineering, Vidyavardhini’s College of Engineering and Technology,
K.T. Marg, Vasai (W), Dist. Palghar, Maharashtra, India
Abstract
The increasing demand for energy and the depleting fossil fuels have fuelled explorations in
new frontiers of renewable energy technology. Geothermal heating and cooling is a new
advancement in HVAC industry of India. It uses earth’s heat for space heating and cooling
with the use of heat pump systems, saving up to 51% electricity consumption in HVAC, and
reduced CO2 emissions. The main prospects of geothermal energy are longer equipment life
and lower operating costs. This paper reviews the recent advancements in geothermal heating
and cooling system.
Keywords: Geothermal, heat pump, ground loop, air handling unit (AHU), heating, cooling,
ground sources heat pump system (GSPH’s)
*Author for Correspondence E-mail: nimishdhepe23@gmail.com; raahul.krishna@vcet.edu.in
INTRODUCTION
Previously the air conditioning system was
considered as the symbol of luxury. Now as
the world is growing faster, it has become a
necessity of the day. Residential and
commercial sector contributes to over 30% of
total electricity consumption [1]. Out of this,
HVAC system consumes 64% of electricity.
As the need for HVAC increases, so does the
demand for energy. Hence fossil fuels are used
on large scale to meet this requirement,
increasing CO2 and particulate matter
emissions, resulting in global warming. This
has paved the way for renewable energy
sources and the feasibility of “Geothermal
heating and cooling” [2].
Fig. 1: Schematic Diagram of Geothermal Heating and Cooling System.
Advancements in Geothermal Heating and Cooling System Dhepe and Krishna
JoAEST (2017) 1-5 © STM Journals 2017. All Rights Reserved Page 2
The name geothermal is derived from the
words ‘Geo’ means earth and ‘Thermal’ means
heat. The earth’s heat is produced by
gravitational collapse and radioactive decay of
isotopes. The soil provides a stable
temperature at approximate 68 m in range of
1629°C all year round [1].
The geothermal system is also called
‘Geothermal heat pump system (GHP’s),
ground source heat pump system (GSPH’s) or
geo-exchange system, working on the basic
heat pump principle of stable earth
temperature to provide heating and cooling.
Ground loops are used to connect the ground
and the space for heating or cooling
applications (Figure 1).
COMPONENTS OF GSPH’S
Geothermal Earth Connection System
Geothermal earth connection system connects
the space to be cooled or heated with the earth
using copper (high thermal conductivity) or
high density polyethylene (HDPE) pipes. The
thermal conductivity of copper is 380 W/mK,
whereas the thermal conductivity of HDPE
pipes is 0.420.51 W/mK. The diameter of
pipe ranges from 29 to 38 mm [3].
As the length of the pipe increases, the overall
efficiency of the system also increases, with
the required length of pipe depending
primarily on geographical and building
character. There are two types GSPH’s
system:
Open Loop
There are two wells, one for taking the water
and another for leaning the water. The water is
injected from the 1st well to extract or reject
heat as per the requirement and then ejected
into 2nd well. The water requirement is 5.67
7.57 lpm per ton (Figure 2) [4]. The main
drawback of this system is the quality of
water, affecting the component life, and
escalating maintenance costs. Also, the local
environment regulation may be restrictive.
Closed Loop
In closed loop system, water is re-circulated
through the coil forming a closed loop. The
quality of water can be regulated and
antifreeze mixture (eg. Methyl alcohol) can be
added to avoid freezing. Closed loop system is
further classified into:
Horizontal Loop: Horizontal loops are
normally at 12 m in depth [5]. If the available
land is more, then horizontal loop can be used.
After installation of this system, we can’t use
this land for other use; hence there is capital in
tie in this system (Figure 3). Also, the soil
temperature varies from the length to length
and there is no constant temperature.
Horizontal loop require approximately
232 m2/t of area, but are easy to be installed
and are less costly [6].
Fig. 2: Open Loop System-Schematic.
Fig. 3: Horizontal Loop.
Vertical Loop: Holes are drilled in the earth.
The space between two bore holes is at least
56 m (Figure 4). This type of system requires
2327 m2/t of area [6]. The cost of installation,
being a function of tube depth and geology of
the location, is more than the horizontal.
The advantages of vertical loop are; lesser
space requirement, lesser variations due of
temperature and thermal properties of soil and
greater efficiency [3].
Journal of Alternate Energy Sources and Technologies
Volume 8, Issue 1
ISSN: 2230-7982 (Online), ISSN: 2321-5186 (Print)
JoAEST (2017) 1-5 © STM Journals 2017. All Rights Reserved Page 3
Fig. 4: Vertical Loop System.
Geothermal Heat Pump System
The heat pump system consists of a
compressor, condenser, expansion valve and
evaporator and is governed by the second law
of thermodynamics. It raises the temperature
of vapour by isentropic compression [7].
Cooling effect is produced by expanding the
compressed vapour in the expansion valve and
lowering its temperature. In summer, it acts as
a refrigerator. The heat pump does not
generate heat but transfers heat from lower
temperature to higher temperature. Heat pump
converts 1 KW of electricity into 3 KW of
useful work [8]. Hence COP of a heat pump is
greater than a refrigerator. A heat pump has an
average life +20 years [9].
Geothermal Heat Distribution System
It consists of an air handling unit (AHU). This
supplies the required temperature air to the
space whose temperature is to be maintained.
Ducts are provided to supply the required
air [5].
Working of Geothermal Heat Pump System
Heating Mode
In winter when heating is required in the room,
the water in the ground loop absorbs the heat
of earth and thus the temperature of water in
the pipe increases. The expanded vapour
refrigerant is circulated within the heat
conductive copper pipes and because the
refrigerant absorbs the heat from ground loop
water, its temperature increases. This vapour
refrigerant is further sent to the compressor
where it is compressed to high pressure and
temperature.
The hot refrigerant vapour is passed from the
copper coil in air handling unit (AHU). The
cold air from the house is blown over this
copper coil using a fan or a blower, absorbing
heat from the hot vapour refrigerant and
heating the room.
Fig. 5: Energy Savings by GSHP’s.
Advancements in Geothermal Heating and Cooling System Dhepe and Krishna
JoAEST (2017) 1-5 © STM Journals 2017. All Rights Reserved Page 4
Cooling Mode
In cooling mode, the operational reversal of
heating mode occurs. The water in the loop
rejects its heat to the earth and temperature of
water decreases. The hot refrigerant from the
compressor rejects its heat to ground water and
the vapour refrigerant temperature decreases.
After this, the refrigerant vapour is expanded
in the expansion valve, further reducing its
temperature. This cold refrigerant then
circulates in copper coil of AHU [13-18].
The hot air from the room is passed over the
cold refrigerant coil, where the hot air rejects
heat. Now this cold air is supplied to the room.
The hot refrigerant is sent back to the
compressor, where it is compressed to high
temperature and pressure, and the whole cycle
repeats. Also, with heating and cooling of
space, we can get hot water by installing
desuperheater in the system.
COMPARISION
From Figure 5, it is observed that 51% of
energy is free and also the energy required for
heating and air conditioning, and water heating
has also reduced.
Advantages
The heat pump has higher efficiency and also
this system does not depend on outside
temperature, as in the case of traditional
HVAC system [10]. Lower maintenance and
operating costs; as heat pump system is
installed within the house, protecting it from
harsh weather and climate conditions [10].
Also it requires 50% lesser power The
ministry of new and renewable energy
(MNRE), New Delhi in a move to boost use of
renewable sources and reduce carbon
footprint, is providing loans, concessions in
tax credits and many more incentives. Water
conservation is 100% due to the replacement
of chiller with ground loops and also low cost
of water heating [11]. Geothermal heating and
cooling is eco-friendly as large amount of CO2
is saved.
FUTURE SCOPE
The growth of this technology is slower than
the other RES technologies due to high cost of
installation and limited knowledge of
geothermal technology and its means of
harvesting [12].
REFERENCES
1. Draft National Policy on Geothermal
Energy. Delhi: Government of India,
Ministry of New and Renewable Energy.
2. Rahul Vadhari, Hiren Prajapati.
Geothermal Air-conditioning.
International Journal of Engg. Science
and Research Technology (IJESRT).
3. ASHRAE Handbook-1999. HVAC
Application. Energy Related Application.
Chapter 31, Geothermal Energy.
4. Klaassen Curtis J. Geothermal Heat Pump
System. Lowa Energy Centre, Energy
Resource Station.
5. Domestic Ground Source Heat Pump.
Design and Installation of Closed Loop
System (2007 Edn., Introduction System
and Application).
6. Momin Gaffara G. Experimental
Investigation of Geothermal Air-
conditioning. American Journal of
Engineering Research (AJER). 2013.
7. Earth to Air System (ETA). ETA
Geothermal Technology: Basic Operating
Overview. www.earthtoair.com
8. Robin Curtis, Kapil JC, et al. A First for
India: 100 KW Borehole Based
Geothermal Heat Pump System for Space
Heating in Himalayas. Proceedings World
Geothermal Congress 2015. Melbourne,
Australia. 1925 Apr 2015.
9. US Dept. of Energy. Energy, Efficiency
and Renewable Energy.
www.energysavers.gov.
10. Geothermal India.
www.geothermalindia.com
11. Grant Morrison, Parwer Ahmed.
Geothermal HVAC Exceeding ASHRAE
Standards at Lowest Life Cycle Cost. Air
Conditioning and Refrigeration Journal.
JanMar 2011.
12. Belf ST, Reddy BV, Rosen MA.
Geothermal Pump System Status Review
& Comparison with Other Heating Option.
Appl Energy. 2013; 101: 341348p.
13. Silva Cocchi, Sonia Castellucci.
Modelling of an Air-conditioning System
with Geothermal Heat Pump for
Residential Building. Math Probl Eng.
2013.
14. Lund JW, Frestones DH, Boyd JL.
Direction Application Geothermal Energy:
Worldwide Review. Geothermal. 2005;
34(6): 691727p.
Journal of Alternate Energy Sources and Technologies
Volume 8, Issue 1
ISSN: 2230-7982 (Online), ISSN: 2321-5186 (Print)
JoAEST (2017) 1-5 © STM Journals 2017. All Rights Reserved Page 5
15. https://www.researchgate.net/figure/27629
8954_fig2_Fi g-2-A-schematic-of-the-
ground-source-heat-pump-system
16. http://www.advancedclimatehvac.com/geo
thermal/
17. http://www.geothermalmontana.com/what
-is-a-geothermal-heat-pump.html
18. http://www.cappyheating.com/benefits-of-
geothermal/#iLightbox[5f182660de63dc6a
a3a]
Cite this Article
Nimish Dhepe, Raahul Krishna. A
Review of the Advancements in
Geothermal Heating and Cooling
System. Journal of Alternate Energy
Sources and Technologies. 2017; 8(1):
15p.
... Various researchers addressed the problem seriously looking into the future of extreme cold and warm regions and also keeping in mind depleting conventional sources of energy. Dhepe and Krishna [13] reviewed geothermal systems for space conditioning as a potential alternative to conventional systems. They have reported that about 30% of the total electricity is consumed by the commercial and residential sector out of which about 64% of the electricity is utilized by heating, ventilation, and air conditioning (HVAC) systems. ...
... Dhepe and Krishna [13] have done a literature review on geothermal cooling and heating systems and the advancements in this field. The increasing demand for energy leads to more exploration of renewable energy technologies. ...
Article
Full-text available
This paper presents modern trends in geothermal energy utilization, mainly focusing on ground source heat (GSH) pumps for space conditioning in buildings. This paper focuses on India along with a general review of studies around the world. Space conditioning of a building contributes to about 40-50% of the total energy consumed in buildings and has an adverse impact on the environment and human health. The India Cooling Action Plan (ICAP) estimates that the demand for electricity for heating and cooling of buildings will increase by over 700% in India at current levels by 2047 with an additional 800 GW of power generation capacity needed just to meet heating and cooling needs by 2050, of which about 70% is required for the residential sector only. It further intensifies as the demand for peak electric load sharply increases in summer because of the extensive use of building air conditioning systems. Researchers across the globe have tried different cooling systems and found that some systems can offer a certain amount of energy-efficient performance, and also occupant comfort. Therefore, this article examines the geothermal potential in buildings for space conditioning by critically reviewing experimental and numerical studies along with the future prospects of GSH pumps.
... Various researchers addressed the problem seriously looking into the future of extreme cold and warm regions and also keeping in mind depleting conventional sources of energy. Dhepe and Krishna [13] reviewed geothermal systems for space conditioning as a potential alternative to conventional systems. They have reported that about 30% of the total electricity is consumed by the commercial and residential sector out of which about 64% of the electricity is utilized by heating, ventilation, and air conditioning (HVAC) systems. ...
... Dhepe and Krishna [13] have done a literature review on geothermal cooling and heating systems and the advancements in this field. The increasing demand for energy leads to more exploration of renewable energy technologies. ...
Article
Full-text available
This paper presents modern trends in geothermal energy utilization, mainly focusing on ground source heat (GSH) pumps for space conditioning in buildings. This paper focuses on India along with a general review of studies around the world. Space conditioning of a building contributes to about 40–50% of the total energy consumed in buildings and has an adverse impact on the environment and human health. The India Cooling Action Plan (ICAP) estimates that the demand for electricity for heating and cooling of buildings will increase by over 700% in India at current levels by 2047 with an additional 800 GW of power generation capacity needed just to meet heating and cooling needs by 2050, of which about 70% is required for the residential sector only. It further intensifies as the demand for peak electric load sharply increases in summer because of the extensive use of building air conditioning systems. Researchers across the globe have tried different cooling systems and found that some systems can over a certain amount of energy-efficient performance, and also occupant comfort. Therefore, this article examines the geothermal potential in buildings for space conditioning by critically reviewing experimental and numerical studies along with the future prospects of GSH pumps.
... 2) Distrubution subsystem The distribution system of geothermal heat contains a unit called air handling (AHU), and the function of this unit is to supplies the desired air temperature to the space where to be heated or cooled through ductwork [7]. A fan inside furnace units' heat pump is a forced sir system, where it blows air around a fan coil to cool or heat the air and distributed through the ductwork of the building. ...
... It can be done by either closed or open loop operation. [121][122][123] Desuperheaters A type of heat exchanger that captures heat waste from heat-generating sources such as air-conditioners and refrigerators. This heat waste can be captured and the energy can be transferred to heat up water. ...
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Published data or available literature on sustainable building plan-design, construction, performance, and renovation criteria have covered some stages or some parts of each stage. These data usually have been published partially in many different papers―there have not been any papers that published these data together. Hence, this paper aims to collectively review these data and publish them together. The collection and review of these data were carried out by our twenty-five team members who specialized in sustainable urban, architectural, and civil engineering and construction management. The gathered and reviewed outputs were combined and validated based on a general group consensus. This consensus decision-making proceeded through two major group meetings with several follow-up meetings. The first major meeting was to combine and improve the gathered reviewed sustainable building criteria for Cambodia. The second major meeting was to validate the improved reviewed sustainable building criteria for Cambodia. The several follow-up meetings were to discuss the relevance and importance of the validated data “criteria and their classifications and descriptions” in all stages and more focused on their importance and applicability to Cambodia. The collective reviewed data in this paper would be useful to researchers in the fields. They could also be useful collective knowledge and information for policymakers from governmental agencies and development partners, particularly for sustainable building and construction companies.
... It can be done by either closed or open loop operation. [121][122][123] Desuperheaters A type of heat exchanger that captures heat waste from heat-generating sources such as air-conditioners and refrigerators. This heat waste can be captured and the energy can be transferred to heat up water. ...
Preprint
Full-text available
Published data or available literature on planning, design, construction, performance, and renovation criteria for sustainable buildings have been focused on some stages, such as design and construction stages, or some parts of each stage due to a limited number of collaborative scholars or the scope of their research. These data usually have been published scattered or partially presented in many different papers―there have not been any papers published these data, all-stage ‘plan-design, construction, performance, and renovation’ criteria, together. Hence, this paper aims to collect and review these data and publish them together. The data collection and review were conducted by our team, 25 members, who specialized in sustainable urban, architectural, and civil engineering and construction management. The review outputs were combined and then validated based on a group consensus. This consensus-based validation proceeded through several times of meetings. These meetings extensively discussed the relevance and importance of the validated data (main criteria and sub-criteria, including their descriptions, of sustainable building in all stages) and more focused on their importance and applicability to the Cambodian context. The collective and review data demonstrated in this paper would be useful to researchers in the fields. They could also be useful collective knowledge and information for policymakers from the governments and development partners, as well as for architecture and building construction companies.
... It can be done by either closed or open loop operation. [121][122][123] Desuperheaters A type of heat exchanger that captures heat waste from heat-generating sources such as air-conditioners and refrigerators. This heat waste can be captured and the energy can be transferred to heat up water. ...
Preprint
Full-text available
Published data or available literature on planning, design, construction, performance, and renovation criteria for sustainable buildings have been focused on some stages, such as design and construction stages, or some parts of each stage due to a limited number of collaborative scholars or the scope of their research. These data usually have been published scattered or partially presented in many different papers―there have not been any papers published these data, all-stage ‘plan-design, construction, performance, and renovation’ criteria, together. Hence, this paper aims to collect and review these data and publish them together. The data collection and review were conducted by our team, 25 members, who specialized in sustainable urban, architectural, and civil engineering and construction management. The review outputs were combined and then validated based on a group consensus. This consensus-based validation proceeded through several times of meetings. These meetings extensively discussed the relevance and importance of the validated data (main criteria and sub-criteria, including their descriptions, of sustainable building in all stages) and more focused on their importance and applicability to the Cambodian context. The collective and review data demonstrated in this paper would be useful to researchers in the fields. They could also be useful collective knowledge and information for policymakers from the governments and development partners, as well as for architecture and building construction companies.
... A review of the recent advancements in geothermal heating and cooling system is presented by the work [19]. It uses earth's heat for space heating and cooling with the use of heat pump systems, saving up to 51% electricity consumption in HVAC, and reduced CO2 emissions. ...
Article
Geothermal residential heating and cooling systems have undeniable potential savings. The possibilities of the energy savings with a geothermal heat pump system is well-established in the commercial and residential sectors. Building location has a critical impact on the performance of geothermal heat pump systems and magnitude of savings. An important contribution of this paper takes the step past technological optimization to investigate 12 climate zones across the contiguous United States. Residential homes within common neighborhoods are thoroughly analyzed by considering soil characteristics and home construction features. Within these climate zones, federal and all local incentive programs are quantified to determine an accurate expectation for capital investment payback period, a critical factor for system attractability. Ultimately, a climate zone is classified as either a promising or poor candidate for residential geothermal technology based on data from previously conducted human interest polls regarding payback period on energy savings investments. With such lasting potential delivered to the hands of consumers, geothermal energy use still experiences slow implementation. This paper conducts a study integrating data on technology, finances, and human nature to identify the prevailing barrier to widespread geothermal execution. Solid evidence on energy and monetary savings reveals the dominant barriers are initial capital investment and long payback period. This paper highlights the immense positive impact that local incentives have on affecting these two prevailing deterrents.
Chapter
Recently, the world’s biggest issue is climate change due to the greenhouse gas emissions of several conventional technological applications and exhaustion of fossil fuels. Thus, the importance has been given on the research of renewable energy. Geothermal energy is a such renewable energy source of the earth. Geothermal energy is the infinite source of energy, maintained to the nearly invariable level of temperature into the earth at a certain depth, almost throughout the year. This concept is being used as a sink for the geothermal heat pump coupled with a geothermal heat exchanger. This research paper assesses the recent projects and the advancement of the geothermal heat pump using for cooling and heating purposes or other business purposes in India. By using geothermal energy, power consumption can be reduced up to 50–60%.
Article
Full-text available
This paper presents a review of the worldwide applications of geothermal energy for direct utilization, and updates the previous survey carried out in 2010. We also compare data from 1995, 2000 and 2005 presented at World Geothermal Congresses in Italy, Japan and Turkey, respectively (WGC95, WGC2000, and WGC2005). As in previous reports, an effort is made to quantify ground-source (geothermal) heat pump data. The present report is based on country update papers received from 70 countries and regions of which 65 reported some direct utilization of geothermal energy. Seventeen additional countries were added to the list based on other sources of information. Thus, direct utilization of geothermal energy in a total of 82 countries is an increase from the 78 reported in 2010, 72 reported in 2005, 58 reported in 2000, and 28 reported in 1995. An estimation of the installed thermal power for direct utilization at the end of 2014 is used in this paper and equals 70,885 MWt, 46.2% increase over the 2010 data, growing at a compound rate of 7.9% annually with a capacity factor of 0.265. The thermal energy used is 592,638TJ/year (164,635 GWh/year), about a 39.8% increase over 2010, growing at a compound rate of 6.9% annually. The distribution of thermal energy used by category is approximately 55.2% for ground-source heat pumps, 20.2% for bathing and swimming (including balneology), 15.0% for space heating (of which 89% is for district heating), 4.9% for greenhouses and open ground heating, 2.0% for aquaculture pond and raceway heating, 1.8% for industrial process heating, 0.4% for snow melting and cooling, 0.3% for agricultural drying, and 0.2% for other uses. Energy savings amounted to 352 million barrels (52.8 million tonnes) of equivalent oil annually, preventing 46.1 million tonnes of carbon and 149.1 million tonnes of CO2 being released to the atmosphere, this includes savings for geothermal heat pumps in the cooling mode (compared to using fuel oil to generate electricity). Since it was almost impossible to separate direct-use from electric power generation for the following, they are combined:approximately 2218 well were drilled in 42 countries, 34,000 person-years of effort were allocated in 52 countries, and US $20 billion invested in projects by 49 countries.
Article
Full-text available
The need to address climate change caused by greenhouse gas emissions attaches great importance to research aimed at using renewable energy. Geothermal energy is an interesting alternative concerning the production of energy for air conditioning of buildings (heating and cooling), through the use of geothermal heat pumps. In this work a model has been developed in order to simulate an air conditioning system with geothermal heat pump. A ground source heat pump (GSHP) uses the shallow ground as a source of heat, thus taking advantage of its seasonally moderate temperatures. GSHP must be coupled with geothermal exchangers. The model leads to design optimization of geothermal heat exchangers and to verify the operation of the geothermal plant.
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