Geothermal Heatpump

 

By the solar radiation, the heat underground keeps 10~20°C one-year round which helps to obtain the heat that can be used for heating, cooling and hot water if we drill a hole about 150~200m underground to input soil heat exchanger and circulate water through the geothermal heat pump.

 

By using this system, we can obtain the stable, high efficiency heat rather than using LNG gas which used for heating during the winter, as well as the free air temperature (summer 35°C, winter -10°C). This system has the highest energy efficiency ratio and usable for the long period.

 

Introduction of Geothermal heatpump system and air conditioning

1. Definition and characteristics of alternative energy
Alternative energy is energy, not oil, coal, nuclear energy, or natural gas, which is designated as 11 sectors. In broad terms, it refers to renewable energy in a narrow sense.

○ New Energy
– energy that liquefies and gasifies hydrogen, fuel cells and coal
○ Renewable Energy
– Geothermal, solar, solar, bio, wind, hydro, marine, waste energy
○ Characteristics of alternative energy
– Technical resources: secured by research and development
– Environmentally friendly resources
– Remarkable resource: permanently renewable energy
○ Characteristics of geothermal energy
– The temperature increases as it goes down from the bottom of 20m underground due to the collapse of radioactive elements (about 83%) and the release of internal heat of the earth (about 17%).
– Deep geothermal resources using geothermal resources of several kilometers underground and geothermal resources using normal temperature resources within 300m

2. Concept of geothermal heating and cooling system
○ The geothermal heating and cooling system is a highly efficient and environmentally friendly system that buries pipes (HDPE) in the ground and solves the cooling, heating, and hot water simultaneously by using the underground heat source (15 ± 5 ℃)
○ This system absorbs the warm underground heat in the winter and heats it. In summer, it uses the principle of throwing away hot heat in the cold underground.
– The underground temperature below 5m is not affected by changes in atmospheric temperature of the four seasons.
– Figure 1 and Figure 2 show the change of temperature according to the depth of the ground.

 

Geothermal Heatpump

 

○ Heat pump (heat pump) is used to increase the desired temperature and efficiency by not using fossil fuel at all,

○ Heating cycle (see Figure 3)
– The low temperature liquid refrigerant passing through the heat exchanger (evaporator) inside the heat pump absorbs heat from the antifreeze (circulating fluid in the underground heat exchanger) and changes phase to vapor refrigerant
– After the evaporation process, the antifreeze whose temperature has decreased is circulated in the geothermal heat exchanger,
– The EWT of the antifreeze (the circulating fluid temperature entering the heat pump) is generally about 9 ° C and the heat pump outlet temperature is about 5 ° C
– The amount of heat absorbed by the antifreeze from the ground is calculated considering the heat capacity of the underground, and based on this, the size of the geothermal loop is determined

Heating principle of geothermal heat pump

 

Geothermal Heat pump key map

 

geothermal_summer

geothermal_winter

 

heat

 

 

Advantages and disadvantages of geothermal heatpump system and air conditioning

○ Advantages
– Reduced area dedicated to machine room
– Excellent life cycle cost.
– 25 ~ 50% less power consumption than noise reduction and existing air conditioning system
– Flexibility to simultaneously heat and cool
– It is safe because there is no risk of fire than petroleum system.
– Reduced maintenance cost by 40 ~ 60% without additional energy
– Environmentally friendly and applicable to renovation buildings
– Reduction of machine room size and cooling towers and ceiling devices are unnecessary.

○ Disadvantages
– Increase in initial investment (20 ~ 100% increase in existing heating and heating facilities)
– Design and construction according to site characteristics
– Increase of required site for underground heat exchanger construction

○ Construction Order
– Building heating / heating load calculation
– Ground and field survey for installation of underground heat exchanger
– Economical analysis and determination of geothermal exchanger type
– Underground heat exchanger size and heat pump capacity determination
– PE pipe embedding and grouting work after drilling
– Underground heat exchanger head and piping connection
– Flushing operation
– System test operation and optimization

○ Installation
– Consider various parameters such as the heating and cooling load of the applied building, the soil properties of the construction site, the thermal properties of the grout material, and the spacing of the boring holes.
– Design method is performed by numerical analysis.
– The program for designing the optimum geothermal system is GchpCalc, GLHEPRO, etc.
– Building heating / heating load calculation program is TRNSYS, Energy Plus, etc.
○ Initial installation cost
– Initial installation costs consist of heat pump equipment cost, underground heat exchanger pipe, indoor side distributor (duct or floor coil), boring hole boring boiler, etc.
– Underground heat exchanger cost 30 ~ 50% of installation cost
– No standard data on construction cost in Korea
– In the US, total underground heat exchanger installation cost is analyzed as 45 ~ 70 dollars / m.
○ Driving and maintenance costs
– There is no data on annual driving and maintenance costs in Korea
– According to the US Environmental Protection Agency, energy consumption is reduced by 44% compared to air heat source heat pumps and by 72% compared to using air conditioners and heaters

 

Domestic and overseas application

□ Global Geothermal Heating and Cooling System Installation Status
○ United States
– As of the end of 2004, more than 600,000 installations
– There is plenty of construction of horizontal type heat exchanger because the country is vast.
– GEICO Office Building, The Empire State Building (Remodeling),
Pennsylvania’s Paragon Center, office buildings, residential complexes, hotels, single-family homes, etc.
– A total of 15 heat pumps, including Econar, Carrier, and ClimateMaster, as well as researchers from Oklahoma State University, and over 500 design, construction and diagnostic companies,
– 1,400,000 heat pumps expected to be delivered in 2010
○ China
– Use in geothermal heating and greenhouse farming near Tianjin, Shaanxi and Beijing
– Beijing Olympic Games will be provided by geothermal heating and cooling of the athletes under the goal of being Green Olympic
○ Other
– Japan uses geothermal resources centered on hot springs and development, and is applied to 60 locations such as hospitals and libraries.
– Germany, Denmark, Switzerland, Austria, etc. use geothermal heating and cooling system in many parts of commercial buildings and houses.
– As of 1998, about 120,000 units were installed in Europe
– Over 10% of installations worldwide are growing annually