Geothermal Water cooled Air Conditioner

Project Title

Geothermal Water cooled Air Conditioner

Project Area of Specialization Mechanical EngineeringProject Summary

Increasing power requirements have become the biggest problem in the world. If we talk about just a small part of the world let’s say PAKISTAN most of the people are unable to purchase an AC system just because of high electricity bills. As the electricity price increases day by day we should take an attempt to facilitate our people. A simple prototype air conditioning unit is to be proposed aiming at replacing the conventional vapor-compression air conditioning systems which are not affordable by a middle class Pakistani. The proposed model is supposed to be used in conditioning the Domestic purpose with the lowest possible running cost. By replacing the conventional air-cooled AC systems with our proposed water-cooled AC systems, the Coefficient of Performance of the system can be increased as water has the largest capacity to absorb heat which results in a decrease in power requirement. Water as cooling fluid from underground water tanks instead of cooling towers the system works even more efficiently in summer due to the geothermal effect. Cooling time, power requirement, and input work can be decreased by using water-cooled condensers in AC systems.

Project Objectives

The main objective of this project is to propose a simple design of geothermal heating and cooling system and test this design's feasibility. In this project, it was observed that this system was able to maintain a room temperature of 25°C. The novelty lies in the use of the concept of constant ground temperatures of the earth in an air conditioning system that uses water as a refrigerant with no use of a heat pump that can provide both heating and cooling. This system can be modified or upgraded according to the needs of a person. This system can be a replacement for air coolers in industries where air conditioners cannot be used.

Project Implementation Method

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. The residential and commercial sector contributes to over 30% of total electricity consumption. Out of this, the HVAC system consumes  64% of electricity. As the need for HVAC increases, so does the demand for energy. Hence fossil fuels are used on a 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".

The geothermal system is also called ‘Geothermal heat pump system (GHP’s), ground source heat pump system (GSHP) or geo-exchange system, working on the basic heat pump principle of stable earth temperature to provide heating and cooling.

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 the 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 the 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.

Cooling Mode:   In cooling mode, the operational reversal of heating mode occurs. The water in the loop rejects its heat to the earth and the temperature of water decreases. The hot refrigerant from the compressor rejects its heat to groundwater 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 a copper coil of AHU. 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 a desuperheater in the system.

Benefits of the Project

• A simple prototype air conditioning unit is to be proposed aiming at replacing the conventional vapor-compression air conditioning systems which are not affordable by a middle class Pakistani.

• The proposed model is supposed to be used in conditioning the Domestic purpose with the lowest possible running cost.

• By replacing air-cooled AC systems with water-cooled AC systems, the Coefficient of Performance of the system can be increased as water has the largest capacity to absorb heat which results in a decrease in power requirement.

• By using water as cooling fluid from underground water tanks instead of cooling towers the system works more efficiently in summer due to the geothermal effect.

• Cooling time, power requirement, and input work can be decreased by using water-cooled condensers in AC systems

Technical Details of Final Deliverable

The technical details of this Geothermal heating and cooling system project consist of all the components that are used in this project.

COMPONENTS OF GHPS:

• Geothermal Earth Connection System:     It 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 380W/mK, whereas the thermal conductivity of HDPE pipes is 0.42–0.51W/mK. The diameter of the pipe ranges from 29 to 38 mm. 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 of GHP systems.

• Open Loop: There are two wells, one for taking the water and another for leaning the water. The water is injected from the first well to extract or reject heat as per the requirement and then ejected into the second well. The water requirement is 5.67–7.57 lpm per ton.

• Closed Loop:  In this system, water is re-circulated through the coil forming a closed loop. The quality of water can be regulated and an antifreeze mixture (eg. Methyl alcohol) can be added to avoid freezing.

The closed-loop system is further classified into:

• Horizontal  Loops: are normally at 1–2 m in depth. If the available land is more, then a horizontal loop can be used. Horizontal loops require approximately 232 m2/t of area, but are easy to be installed and are less costly.

• Vertical Loops:  Holes are drilled in the earth. The space between two boreholes is at least 5–6m. This type of system requires 23–27m2/t of area. The cost of installation, being a function of tube depth and geology of the location, is more than the horizontal.

 

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 vapor by isentropic compression. The cooling effect is produced by expanding the compressed vapor 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. The heat pump converts 1 KW of electricity into 3 KW of useful work.

Geothermal Heat Distribution System: It consists of an air handling unit (AHU). This supplies the required temperature air to space whose temperature is to be maintained. Ducts are provided to supply the required air.

Final Deliverable of the Project Hardware SystemCore Industry Energy Other IndustriesCore Technology OthersOther TechnologiesSustainable Development Goals Affordable and Clean Energy, Responsible Consumption and ProductionRequired Resources

Item Name	Type	No. of Units	Per Unit Cost (in Rs)	Total (in Rs)
			Total in (Rs)	71000
Copper Tubes	Equipment	1	5000	5000
Motor	Equipment	1	7000	7000
Condensing Pipe , Valves	Miscellaneous	1	4000	4000
Complete Indoor AC unit	Equipment	1	55000	55000