Abstract
Ground-source heat pumps (GHSP) are perhaps the most used green cooling and heating systems. With increasing concerns over environmental damage created by fossil fuels and other sources of energy, GHSP is an attractive option for heating and cooling buildings. This paper reviews different articles on the subject to understand the concept and different opinions on the applicability of GHSP. The paper then relates the technology to the triple bottom line of sustainability. Various costs involved are highlighted. The paper concludes that GHSP technology is cost effective, has tremendous societal benefits and is one of the most environmentally friendly energy exchange technologies.
Introduction
Ground-source heat pumps (GHSP) are perhaps the most used green cooling and heating systems. Their operation is based on a renewable energy technology utilized in heating or cooling spaces. “This technology is dependent on the fact that the earth has the most stable temperatures, warmer than the air during winter and cooler than the air during the hot temperatures in summer” (Omer 367). The earth can therefore serve as an exchange environment by using a geothermal heat pump to transfer heat from the earth to a building during winter and transfer heat from the building to the earth during summer. There are no special geological conditions required for this technology making its application easy.
Ground-source heat pumps are today attracting a lot of attention due to their environmental advantages. They have potential to reduce heat energy consumption which would in turn reduce greenhouse gasses emissions (Eicker and Christoph 1126). This technology is today well established in North America and is also picking up pace in some parts of Europe. In the United Kingdom, the technology is still at its demonstrative stages and is well received in the neighboring countries too.
Ground-source heat pumps uses pipes buried in the ground to transfer heat from the ground to a building and the other way round. During cold seasons, heat from the ground is converted to warm air and is distributed in a building using air ducts. During hot seasons, heat in the room is cooled by using the cooler ground as its heat sink (Milenic, Petar, and Ana 650). The process does not involve any combustion processes. It is simply transfer of heat from one place to the other. Transfer is done through open loop where surface or well water is circulated or through closed loop systems where water or another a fluid mixture is transferred through pipes.
Literature review
Omer is his article clearly states that heat pumps significantly reduce the amount of energy used for cooling or heating buildings (367). According to the author, GSHPs reduce the need for primary fuels by more than 65% which would have increased the amount of emissions to the atmosphere. The article’s analysis is intended at estimating and comparing the warming effect of a GSHP and that of other cooling and heating systems. The paper studies the effects of heating on both commercial and residential buildings.
Analysis of data from the study reveals that conventional methods of heating and cooling emit up to 36% more greenhouse gasses than does GSHPs. The report also reveals that this technology is most effective in places such as Europe and other regions across the globe which suffer extreme temperatures in different seasons. It concludes that it is unlikely the world is going to have a heating and cooling technology as friendly to the environment as the GSHP technology.
Phetteplace studies the technology behind GSHPs and explains how the technology operates by heat transfer from the earth to a building when it is cold and the reverse is true when it is hot (34). The journal is a simple explanation of the basic process which the readers would easily understand. It is also a comparison of the technology with other thermal technologies. The various types of geothermal heat together with their benefits are reviewed. A big part of the paper is the vertical borehole heat exchanger which is the most commonly used method of ground coupling (Phetteplace 34). The author discusses issues regarding sizing of heat exchangers and the various reasons for using each of the technologies.
Spittler argues that GSHPs can and are being used as seasonal energy storage schemes (165). The paper gives a general overview of ground-source heating technology. The paper gives a detailed overview of the technology since it was first mentioned in 1912. It is a discussion of how the technology has evolved and its current applicability in different parts of the world. The author also gives a highlight of what is expected of the technology in the few years to come. In regard to the current environmental concerns, the technology appears to be the most favorable in minimizing environmental damages caused by conventional heating and cooling systems. The paper is also a brief research into how the GSHPs can be optimized to improve the technology’s thermal conductivity.
Milenic, Petar, and Ana argue that environmental protection are conducted by use of renewable energy sources (649). Their article is a discussion of how GSHPs is being used in developed regions today such as Europe as a substitute for fossil fuels and as a measure to reduce greenhouse gas emissions. The authors argue that use of geothermal energy sources give higher economical growth rates in a country due to minimized costs and negative effects. Considering the number of homes put up in Europe each year, the article argues that there is need for reduced energy consumption levels by utilizing such technologies. Finally, Eicker and Christoph propose that geothermal heat exchangers would be the best technology as heat sinks for buildings energy produced during the hot seasons (1126). An experiment carried out in this study is used to study how soil parameters, inlet and exit temperatures would influence the operation and effectiveness of GSHPs.
Triple bottom line of sustainability
Environmental benefits
Other than wind, solar, water and biomass, ground-source heat pumps have proved to be very environmentally clean methods of providing heat and light. They are easily applicable without major environmental distraction such as clearance of large portions of land. It is also notable that their application does not require distraction or interference with water bodies. Use of GSHP eliminates the need for furnaces or even air-conditioners which use too much energy to run. The technology can be used to heat water in buildings at no added costs and at zero risk of polluting the environment as is the case with use of conventional heaters.
Since the process requires no combustion, the technology has been proven to reduce green house emissions by 66% or even more. This helps protect the environment from the biggest concern today which is emissions. There are reduced carbon dioxide, nitrate and sulphate gases being emitted to the atmosphere, thus protecting the ozone layer. The piping does not take a lot of space and is underground meaning that land can still be utilized for other purposes especially in the case where the technology is used in residential areas where people practice farming.
Societal benefits
GSHPs offers consumers a more pocket and environmentally friendly option to warm or cool their houses as desired. The technology is reliable since earth temperatures are not likely to fluctuate. It is efficient and once installed correctly, consumers are not likely to suffer interruptions like it is with electricity and other energy sources. It is cost saving it has no production costs. The only costs incurred operation and maintenance costs, approximated to be 60% less than those of conventional energy technologies (Spitler 166).
Ground-source heat pumps have a level of flexibility that is not easily achievable in other energy technologies. It can be used in big commercial buildings and can be used in homes and other small structures. Its applicability in residential building is now applicable in Japan, the U.S, Canada and other European countries. China is now using the technology and testing it in smaller structures such as homes. As a result of reduced green house emissions, GSHP gives its consumers a confidence of knowing they are protected from the negative effects which may arise. Consumers can comfortably benefit from the technology without having to worry about the side effects.
GSHP causes no carbon, nitrate, sulphate and other poisonous gases emissions to the atmosphere. This means that consumers are protected from health complications resulting from such emissions. Their plants, vegetation and animals are further protected from such concerns. All these advantages convert to more economic benefits from minimized health bills and time wasted during treatment. Psychologically, it is very assuring and peaceful to use an environmentally friendly product. The technology is not noisy compared to other technologies such as generators.
Economical benefits
It is also proven that a building could use up to 70% less electricity by using GSHP technology. Its maintenance costs are half that of conventional systems while the cost of installing it can go as low as a quarter that of conventional systems (Kavanaugh 67). The pipes are installed in such a way that they utilize the energy near the surface of the earth. This minimizes the time taken to transfer energy from and to a building. By tapping heat energy nearer to the surface, the length of piping is reduced which significantly saves on cost.
Omer estimates that an open-loop water source system for an average residential house would cost not more than $ 10,000 while the price may double for a closed-open loop system (367). The annual operating costs and maintenance costs amount to far much less figures compared to other conventional heat exchange systems. The total cost of running a GSHP system average to $850, while a conventional system would amount to three time this. Even though the savings may be dependent on different factors such as climatic patterns of a place, lifestyle and size of a building, they cannot add up to the costs incurred when using conventional systems of cooling and heating buildings. Economical benefits also arise from the fact that the technology does not incur any space for storage like in the case of boilers, cooling towers and generators. All the money saved can then go to savings and other economic developments in a society.
Saving energy using GSHP
Since GSHPs use ducts to heat and cool, it is able to maintain comfortable temperatures in a room without losing it out the environment. Since it is stored inside and its lines are buried under the earth, it is not possible for the process to lose energy to the external environments. It therefore operates under minimum loses and makes it possible to save a lot of energy. It is not dependent on climatic changes and is a good source when other sources of fuel are in shortage. Compared to fossil plants, electricity and other sources of energy, the underground heat energy is renewable, minimizing fear of shortages. The process requires no combustion or processing and thus utilizes no energy to produce heat or cool a building. As a result, it is the most energy saving process of heating or cooling in existence right now. According to research “ground source heat pump condenses inlet temperatures at 300C, has a 25% less demand of primary energy and has a 50% more overall efficiency than other heating and cooling systems” (Phetteplace 38).
Calculations
The installation process for a GSHP system is the most costly in the whole process. Costs incurred include cost of pumps, cost of coils and other earth connections, and cost of the heat distribution system. Heat pumps and pipes have to be purchased. The current market prize show that a geothermal heat pump would cost $ 2,500 per ton of capacity. An average residential home can run on a three tonnes pump capacity. A 10,000 m2 sized commercial building can effectively run using a pump with a 15 tonne capacity.
- Cost of pumps: For a 10,000 m2 size commercial building: $ 37,000
- Installation and labor costs are approximated at $10,000.
- Coil or earth connection costs: The costs of connection are dependent on the depth of the piping and type of design. For this design, a horizontal closed loop is used and incorporated in a 1500m2 field.
- Cost of drilling and coils installation is approximated to be $ 20,000.
- Heating and distribution system costs:The heat distribution system is the most important and determines how effective the project is going to be. Larger installations may be needed in big buildings where multiple heat pumps are required. The cost of distribution includes that of air ducts. This cost is approximated to be $ 27, 500.
Total cost of installation = $ (37,000 + 10,000 + 20,000 + 27,500)
=$ 94,500.
Conclusion
“The GSHPs technology is dependent on the fact that the earth has the most stable temperatures, warmer than the air during winter and cooler than the air during the hot temperatures in summer” (Phetteplace 36). It is perhaps the most “green” cooling and heating technology today. The technology has minimum greenhouse emissions, require little space for operation and is cheaper to install and maintain. It is not noisy compared to other technologies. In conclusion, it is an environmentally friendly technology with many economical and societal benefits for any country willing to explore it. Since there are no special geological conditions required, it is an easily applicable technology.
References
Eicker, Ursula and Christoph Vorschulze. “Potential of Geothermal heat exchangers of office building climatization.” Renewable Energy 34 (2009): 1126-1133. Print.
Kavanaugh, Stephen. Ground-source Heat Pumps: Design of Geothermal Systems for Commercial and Institutional Buildings. Atlanta: American Society of Heating, Refrigerating and Air-Conditioning Engineers, 2000. Print.
Milenic, Dejan, Petar Vasiljevic, and Ana Vranjes. “Criteria for use of groundwater as renewable energy source in geothermal heat pump systems for building heating/cooling purposes.” Energy and Buildings 42 (2010): 649-657. Print.
Omer, Abdeen Mustafa. “Ground-source heat pumps systems and applications.” Renewable and Sustainable Energy Reviews 12 (2008): 344-371. Print.
Phetteplace, Gary. “Geothermal heat pumps.” Journal of Energy Engineering 32 (2007): 32-38. Print.
Spitler, Jeffrey. “Ground-source heat pump system research: Past, present and future.”HVAC&R Research 11.2 (2005): 165-167. Print.