2010 Envisci Paper Gshp

8/6/2019 2010 Envisci Paper Gshp

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GROUND SOURCE HEAT PUMP AS AN ALTERNATIVE IN HVAC SYSTEMS FOR

BUILDINGS IN NUEVO LEON, MEXICO

Hctor Miguel Hernndez TurrubiatesCenter for Environmental and Research Education, Duquesne University.

600 Forbes Avenue, Pittsburgh, Pennsylvania, 15420, U.S.A.

(412) [email protected]

ABSTRACT

The energy consumed in buildings represents an important part in generation of greenhouses gasesaround the world. The major part of energy consumption in buildings is due to Heating, Ventilation,and Air Conditioning (HVAC) systems.

The use of renewable energies as an alternative for reduction of fossil fuels consumption is more oftenin the race for stop climate change. Geothermal energy has been gaining terrain the last years in HVACsystems through Ground Source Heat Pump (GSHP). However, in Mexico there is still muchuncertainty with this application because there is no much information or background on these issues,making it difficult to decisions makers, in building projects, to give an opportunity to GSHP systems.

This paper aims is to analyze GSHP systems and its applications versus conventional HVAC systems.For this case of study, a typical building located in Monterrey, Nuevo Leon, Mexico, will be studied;taking into account variables that have an influence in the process, using computer's simulation tools.

INTRODUCTION

CURRENT AND FUTURE ENERGY SCENARIO IN MEXICODay after day not only growing demand for electricity use around the world but also the need to meetthose needs in a reliable, efficient and taking into account the care of the environment. Each countrydevelops its own strategies of power supply based on their economic development.

The annual growth rate (AGR) of global electricity consumption for the period 1994 to 2003 was 3%.In North America the AGR has been 2%, below the world average; taking to Canada, United States andMexico an AGR of 1.4%, 1.9% and 5.7% respectively. The forecasts for world consumption areexpected that developing countries are those who achieve the highest growth in electricity capacity inthe coming years.

In Mexico, electric service is in charge of the company Comision Federal de Electricidad(CFE) and itis this institution that regulates, through the Public Service Act Electricity (LSPEE) and EnergyRegulatory Commission (CRE ) all matters concerning the generation, transmission and distribution ofelectricity in the country. The power supply is classified into five areas: Agricultural, Industrial,Residential, Commercial and Services. The Industrial sector is the most AGR presented with a 4.5%during the period 1994 to 2004, and accounted for 59.1% of total domestic supply for the past year.However, this sector is divided into two sub sectors, Big Industry and Medium Enterprises, which


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accounted for 38.8% and 61.2% respectively of the total industrial sector. The residential sector is insecond place, accounting for 24.9% of total consumption of generation in the country.

Although only one institution is responsible for the electricity service in Mexico (CFE), it is dividedinto regions to better control. The Northeast Region has the highest growth has been in recent years interms of power consumption, with 5.2% AGR. This is mainly due to the number of new industries andhigh temperatures in this region, increasing the use of air conditioning and refrigeration.Nuevo Leon is one of the states that belong to this region and is the largest consumer of electricity with35% of the total energy supplied. The Projected growth in power in Mexico for 2015 is 5.2% AGR,with the Industrial Sector the fastest growing today.

Unfortunately, the use of renewable energy technologies have a major development in our country inthe coming years, compared with natural gas which is estimated to cover 51.8% of the source ofelectrical energy production by 2014. This national strategy and concern about the current problems inthe environment, including climate change, makes us think of new ways to optimize the efficiency ofenergy end use. Buildings consume most of the energy industry and that is where we can find a goodarea of opportunity. The energy consumption in the operation of buildings is mainly due to heat gain bythe low level of thermal insulation envelope, causing a greater demand for cooling. The work on theoptimization of the thermal insulation of buildings is nothing new. But the use of alternative energytechnologies for cooling them is becoming increasingly common around the world. In this paper, weanalyze the potential of geothermal heat pumps (GSHP) as an alternative to the buildings in NuevoLeon.

GSHP Ground Source Heat Pumps.

FIGURE 1.- Schematic Draw of a GSHP system for a house.

Ground Source Heat Pumps are electrically powered systems that tap the stored energy of the greatestsolar collector in existence: the earth. These systems use the earths relatively constant temperature toprovide heating, cooling, and hot water for homes and commercial buildings.


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FIGURE 2.- Measurement of temperatures for different depths.

GSHP can be categorized as having closed or open loops and those loops can be installed in threeways: horizontally, vertically, or in a pond/lake. The type chosen depends on the available land areasand the soil and rock type at the installation site. These factors will help determine the most economical

choice for installation of the ground loop.For closed loop systems, water or antifreeze solution is circulated through plastic pipes buried beneaththe earth's surface. During the winter, the fluid collects heat from the earth and carries it through thesystem and into the building. During the summer, the system reverses itself to cool the building bypulling heat from the building, carrying it through the system and placing it in the ground. This processcreates free hot water in the summer and delivers substantial hot water savings in the winter.

FIGURE 3.- Closed loop system.

Open loop systems operate on the same principle as closed loop systems and can be installed where anadequate supply of suitable water is available and open discharge is feasible. Benefits similar to theclosed loop system are obtained.


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FIGURE 4.- Open loop system.

APPLICATIONS

GSHP systems can be applied for both heating and cooling for buildings, pools, to melt snow and ice,and also for industrial process.

Residential

A GSHP system can be installed in a residential structure of any size, anywhere, whether it is single-family or multi-family. GSHPs can be installed on almost any size lot: under lawns, landscaped areas,driveways, or the house itself. An existing house can be retrofitted with a GSHP using the ductworkthat is already there. Your dealer/installer will be able to determine ductwork requirements and if anyminor modifications are needed. Home builders and homeowners can both take advantage of thespecial financing that is offered in many locations on a GSHP either through the utility or manufacturer.The Department of Energy (DOE) and the Environmental Protection Agency (EPA) have both endorsedground source heat pump systems as among the most energy efficient and environmentally friendly

heating, cooling, and water heating systems available. In a 1993 report, the EPA concluded thatgeothermal technologies represent a major opportunity for reducing national energy use and pollution,while delivering comfort, reliability and savings to homeowners.

HOPE CROSSING, Oklahoma.

Hope Crossing is a 217 home development by Central Oklahoma's Habitat for Humanity (COHFH) inOklahoma city. This is a showcase large-scale demonstration of affordable low-energy housing and allthe houses will be certified in LEED by USGBC. The project utilizes ground source heat pumps, low-energy building construction techniques and solar energy consumption by 60 to 80 percent from currentpractice.

GSHP systems provide homeowners with year-round comfort in a mixed-humid climate area of thecountry that presents substantial humidity throughout the year and requires significant heating andcooling. GHSP systems also provide high-efficiency performance and much lower utility bills,increasing the affordability of the homes.

GSHP Benefits: Lower utility costs: The GSHP system is projected to save 50 to 75 percent of the traditional

heating and cooling costs. Improved comfort: Residents have the benefit of heating and cooling from the quit and clean


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geothermal system. Reduced maintenance: Since there is no outdoor equipment, damage from weather is

eliminated. All routine maintenance performed inside. Vandalism: All equipment is located inside, minimizing the risk of vandalism and theft.

Commercial

GSHPs are a cost effective, energy efficient, and environmentally friendly way of heating and coolingbuildings. Both the DOE and the EPA have endorsed the technology. GSHPs reliably deliver qualityair-conditioning and heating, on demand, in every season. GSHPs are appropriate for new constructionas well as retrofits of older buildings. Their flexible design requirements make them a good choice forschools, high-rises, government buildings, apartments, and restaurants--almost any commercialproperty. Lower operating and maintenance costs, durability, and energy conservation make GroundSource Heat Pumps the smart choice for commercial applications.


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SOILS CLASSIFICATION IN MEXICO.

According to the National Institute of Geography and Statistics (INEGI) in Mexico the systems ofclassification and description of soils that are based on the 1988 version of the soil classificationFAO/UNESCO/ISRIC.The soil classes considered and the corresponding areas that are reported were calculated based on themost recent estimate of the land area of the country (INEGI, 1999). Thus, relevant information ispresented on the surface of the dominant soils at national level and also by state, in addition to the mainfeatures thereof.

The following chart shows the dominant soil classification in the country.

FIGURE 5.- Soil classification in Mexico.


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NUEVO LEON

Nuevo Len is a state located in northeastern Mexico. It borders the states of Tamaulipas to the northand east and San Luis Potos to the south, and Coahuila to the west. To the north, Nuevo Len accountsfor a 15 kilometer (9 mi) stretch of the U.S.-Mexico border adjacent to the U.S. state of Texas.

The capital of Nuevo Len is Monterrey; other important cities include Guadalupe, Santa Catarina, SanNicols de los Garza, and San Pedro Garza Garca, all of which are part of the Monterrey Metropolitanarea.

FIGURE 6.- Location of Nuevo Leon State in Mexico.

ECONOMY

Highly industrialized, Nuevo Len possesses a standard of living similar to that of countries such asCroatia, Slovakia or Poland. In 2007, the per capita GDP of the state was similar to that of the AsianTiger of South Korea and even higher than that of some European Union states such as Slovakia andHungary. At $26,658, it was the highest GDP per capita (PPP) of any Mexican state (not counting theFederal District), and was therefore higher than the Mexican national average (2007 GDP per capita(PPP) national average was $14,119).

One of its municipalities, San Pedro Garza Garca, has the highest income per capita in Mexico. It isalso home of powerful conglomerates, such as Cemex (third largest cement company in the world, afterLafarge and Holcim), Bimbo (bakery and pastry), Maseca (food and grains), Banorte (the only high-street bank in Mexico wholly owned by Mexicans), ALFA (Sigma, Alestra, Nemak, Alpek and Hylsa(recently bought by Ternium), i-service (HelpDesk), Vitro SA (glass), FEMSA (Coca-Cola in LatinAmerica), and Cervecera Cuauhtmoc Moctezuma (brewers ofSol, Tecate, XX, Bohemia, Indio andNochebuena).

Nuevo Len also boasts a rich agricultural core, called the "orange belt", which comprises themunicipalities of Allende, Montemorelos, Hualahuises, General Tern and Linares. Small butproductive investments have been transforming traditional harvests (mainly based on orange andcereals) into agroindustrial developments that are producing increasing revenues for the local economy.

In contrast with the relative wealth of industrial Nuevo Len and the orange belt, the Southern part ofthe state (municipalities of Galeana, Aramberri, Zaragoza, Doctor Arroyo and Mier y Noriega) remainsrural and less productive. Most of The South of the state is at the mercy of a very dry weather thatrepresents a major hurdle for agriculture and livestock.


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As of 2007, Nuevo Lens economy represents 11.4% of Mexicos total gross domestic product or 105billion USD. Nuevo Len's economy has a strong focus on export oriented manufacturing (i.e.maquiladora / INMEX). As of 2005, 431,551 people are employed in the manufacturing sector. Foreigndirect investment in Nuevo Len was 1,213.1 million USD for 2005. In recent years, the stategovernment has been making efforts in attracting significant investments in aeronautics, biotechnology,

mechatronics, information and communication technologies fields with the creation of the Researchand Technology Innovation Park PIIT (Parque de Investigacin e Innovacin Tecnolgica), atechnology park oriented in the development, innovation and research of sciences. The project is one ofthe key strategies within the Monterrey, international City of Knowledge program. The park is locatedin the municipality of Apodaca, part of Greater Monterrey at the 10 km of the highway to MonterreysInternational Airport. It consists of a total surface area of 70 Ha (172 acres), half of it alreadycommitted to R&D centers. The other 35 Ha (86 acres) are available for research and developmentcenters, and for businesses that meet the Parks objectives.

CLIMATE

Nuevo Len has many biomes, which is why it has different climates. Some areas in the mountains arevery cold in winter and temperate in summer. In the northern part of the state the climate is arid as aresult of the proximity to the Chihuahuan desert. Extreme high temperatures of 47 C or more occur onthe desert areas while winters are short and mild. In Monterrey the climate is semi-arid with extremehot summers and mild winters. There is very little rainfall throughout the year, usually about 500 mmor less.

According to this information, the classification of soils in the state of Nuevo Len is:

TYPE OF SOIL SURFACE (km) STATE PERCENT

CALCISOLES 32708 50.52

LEPTOSOLES 21067 32.54

VERTISOLES 7691 11.88

KASTAOZEMS 1923 2.97

REGOSOLES 1353 2.09

TABLE 1.- Most common type of soil in Nuevo Leon.

Based on this information, we can obtain the thermal conductivity of these soils using tables toimplement a simulation of the case studies.


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CASE OF STUDY

Medium House type in Nuevo Leon.

According to the report of the Current Status of Housing in Mexico 2009, in the country more than26'180,793 houses which is estimated to Mexican cities are growing at a rate of 20,000 hectaresannually.The homes in Mexico are classified as follows:

TYPE OF HOME SINCE TO

Economic - $299,866.00

Popular $299,866.00 $363,171.00

Social $363,171.00 $583,072.00

Medium $583,072.00 $1,082,848.00

Residential $1,082,848.00 $2,598,835.00

Residential Plus $2,598,835.00 Further

TABLE 2.- Range of Mexican homes costs per type. (Values in Mexican Pesos).

For the case study of a typical household in the region of the state of Nuevo Leon, will take theconsiderations of a qualifying home Medium with typical materials of construction and related climaticdata according to the Kppen classification. The decision in taking this type of home for simulations isbecause it is one of the most common models in current construction and demand due to de economicalsituation of the country.

ELEMENT MATERIAL THICKNESS (m)

Walls

Mortar

Concrete blockPlaster

0.013

0.1500.013

CeilingsConcreteMud-blockPlaster

0.0500.1000.013

TABLE 3.- Characteristics of the parts and materials used in construction.

Material Density

(kg/m)

Cp

(J/kg-K)

Thermal Conductivity

(W/m-C)

Concrete block 2300 1000 1.63Mud-block 2225 960 0.5

Concrete 2000 1000 1.13

Mortar 2800 896 0.88

Plaster 900 1000 0.25

TABLE 4.- Properties of materials used in construction.


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FIGURE 7.- Distribution of climatic zones of Mexico according to the Kppen-Geiger classification.

For the analysis of this case study will examine the heat transfer. First you determine the heat load ofthe house by computer simulations with EnergyPlus software and graphic user interface Design Buildersoftware, taking into account all the heat gains due to closures and infiltration, and then propose adesign for a heat exchanger heat pump using the GLHEPRO software for data previously calculated.

DESIGN BUILDER

DesignBuilder features an easy-to-use OpenGL solid modeler, which allows building models to beassembled by positioning, stretching and cutting 'blocks' in 3-D space. Realistic 3-D elements providevisual feedback of actual element thickness and room areas and volumes and there are no limitations ongeometric form or surface shape.It is the first comprehensive user interface to the EnergyPlus dynamic thermal simulation engine.

ENERGY PLUS

Energy Plus is a whole building energy simulation program that engineers, architects, and researchersuse to model energy and water use in buildings. Modeling the performance of a building with

EnergyPlus enables building professionals to optimize the building design to use less energy and water.

GLHEPRO

GLHEPRO was developed as an aid in the design of vertical borehole-type ground loop heatexchangers used in geothermal heat pump systems. While GLHEPRO may be used for residential


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system design, it is aimed at commercial systems. The heat exchanger may be composed of any numberof boreholes arranged in various configurations. This software is based on the methodology developedby Eskilson at the University of Lund in Sweden.

The house model selected will be elaborated using the Design Builder tool according to the informationgathered. It has two levels described as follow:

1. Level 1: Living room, dining room, kitchen and restroom.2. Level 2: Three dorm rooms and one bathroom.

FIGURE 8.- Model of housing type medium for case of study (90 m).

For this simulation in particular was not considered the influence of other buildings for the heat transferanalysis, being the principal of these factors the shadow of neighbor houses on the studied house.The frontal face is located at east.

Data of a typical week in summer will be used for cooling design.


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OUTCOME OF ANALYSIS

The data of the simulation using for the heating and cooling design is showed in the follow chart. Also,the amount of CO produced in the operation of the house's HVAC system.

0

5

10

25303540

-100

-20

-10

0

100

200

0.0

2.5

5.0

0

2

4

6

28 DomJul 2002

29 Lun 30 Mar 31 Mie Ago 2 Vie 3 Sab

New Result Set - CASA MEDIA, Casa MediaEnergyPlus 27 Jul - 2 Ago, Horario Evaluacin

Hora/Fecha

Elec tric id ad d el Es pac io Ilumina ci n Bo mb as de l Si st ema E lec tric id ad Enf riad or a (El ec tr ic ida d) DHW ( Elec tric id ad )

Temperatura del Aire Temperatura Radiante Temperatura Operativa Temperatura de Bulbo Seco Exterior

Acristalamiento Muros Techos (int) Suelos (int) Suelos sobre terreno Particiones (int) Cubiertas Puertas y rejillasSuelos (ext) Vent Natural Int Aire exterior Bombas Iluminacin General Computadoras + Equipos OcupacinGanancias Solares por Ventanas Exteriores Calentamiento Sensible de Zona Enfriamiento Sensible de Zona

Enfriamiento sensible Enfriamiento Total

Direccin del Viento

CO2

Vent. Mec. + Vent. Nat. + Infiltracin

FIGURE 9.-Simulation of a typical week in summer.

The analysis of calculation shows a high load for both, heating and cooling. This is over the averageloads in a typical house but the explanation is due to the influence of neighbor houses is not considerfor this case.

25

30

35

40

0

50

-20

-15

-10

-5

0

3035

40

45

1

2

3

Temperatura y Ganancias de Calor - CASA MEDIA, Casa MediaEnergyPlus 30 Jul, Sub-horario Evaluacin

Tiempo1:0 0 2 :0 0 3:0 0 4 :00 5:00 6 :00 7 :00 8 :00 9 :00 1 0: 00 1 1: 00 1 2:00 13 :00 14 :0 0 15 :0 0 16 :0 0 17 :0 0 18 :0 0 1 9:0 0 2 0: 00 2 1:0 0 2 2: 00 2 3:0 0

Temperatura del A ire Temperatura Radiante Temperatura Operat iva Temperatura de Bulbo Seco Exterior

Acristalamiento Mur os Techos (int) Suelos (int) Suelos sobre terreno Par ticiones ( int) Cubiertas Puer tas y rejillasSuelos (ext ) Vent Nat ural I nt Inf iltracin Ext Vent Exter ior I luminac in G ener al Comput adoras + Equi pos OcupacinGanancias Solares por Ventanas Exteriores Enfriamiento Sensible de Zona

Enfriamiento sensible Enfriamiento Total

Humedad Relativa

Vent. Mec. + Vent. Nat. + Infiltracin

FIGURE 10.- Temperatures and heat for a typical summer week.


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OUTCOME OF LOADS CALCULATIONS

Heating Design = 15.620 kWCooling Design = 27.920 kW

Based on these values obtained, we use the library of GLHEPRO to select a heat pump and calculatethe values of GSHP system design. The heat pump selected was the ClimateMasterRE08@17GPM_3200CFM.

The soil average temperature it is not available for Monterrey but according to researchers, normallythis temperature can be considered adding 1.4 C to the average temperature from the location.The array selected for this heat exchanger in particular is a 3x2 with 3m of spacing between eachborehole taking into account the the average space in a typical house for garden.

FIGURE 11.- Temperature profiles for a typical array of 3x 2 heat exchanger.

Once the information needed for the GLHEPRO is gathered, the simulation is run expecting to have thedepth suggested for each borehole and also the electrical consumption.

GLHEPRO -- Output file

-----------------------------------Active borehole length, m = 82.04Borehole diameter, m = 0.11Borehole spacing, m = 3Borehole Geometry : RECTANGULAR CONFIGURATION: 6 : 2 x 3, rectangleSoil Type currently used :Thermal conductivity of the ground, W/(m*K) = 2.8

Volumetric heat capacity of Ground, kJ/(K*m^3) = 2400Volumetric heat capacity of fluid, kJ/(K*m^3) = 4173.36246853979Undisturbed ground temperature, C = 24Borehole thermal resistance, K/(W/m) = 0.175Fluid type currently entered : 0% Pure WaterMass flow rate of the fluid, m^3/s = 1.99600175346264Density of the fluid, Kg/m^3 = 998.1006868Heat Pump Selected : ClimateMaster RE08@17GPM_3200CFM*************************************************************************Results*************************************************************************Borehole Information


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---------------------Each Borehole Depth, m = 120.01Total Borehole Depth, m = 720.07Distance between borehole centers, m = 003.00Average Temperature--------------------Maximum Average Temperature, C = 028.11 at month 236Minimum Average Temperature, C = 020.46 at month 01Peak temperature

-----------------Maximum Peak Temperature, C = 032.23 at month 235Minimum Peak Temperature, C = 014.44 at month 01

TABLE 5.- Report of the GLHEPRO simulation.

ECONOMICAL ANALYSIS OF GSHP SYSTEMS.

The mainly economical factors to consider for a GSHP project are: High cost of installation. Significant energy savings. Incentives for energy savings. Special funding schemes. Payback period.

According to a study realized by Alabama University, the cost of excavation is the highest factor in aGSHP system.

Average cost of GSHP: Horizontal: US$675/kW Vertical: US$680/kW

The difference against a conventional HVAC system is around 350-450 US$/kW.

FIGURE12.- Comparison of total cost between conventional and GSHP systems.


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CONCLUSION

It is evident the difference between conventional and GSHP systems initial costs. But the 30 60%savings in maintenance and operations makes the payback of this invest shorter. In some cases thispayback period can be 2 years.

The proposed use of GSHP systems in buildings Mexican is definitely a viable alternative not onlybecause it reduces power consumption but also because it contributes to reducing global warming byusing a renewable energy source. It is necessary to validate the results obtained through simulations,measurements and field trials to have a smaller margin of error.The greatest barrier, undoubtedly, that these systems have to overcome before being used in a mannercommon in Mexican society is the cost of investment. If there is evidence that the investment isrecovered in a few years depending on the type of project, the initial investment is what is hindering thedevelopment of these methodologies.To overcome these barriers, we must work to amortize financing mechanisms such investment costs ofthese technologies.

In Mexico there are just a few federal programs that begin to stimulate the use of these means offinancing. One is the Green Mortgage (Hipoteca Verde) and the other is the Integrated UrbanDevelopment (DUIS).

A recently developed another system that will soon begin work on this type of technology: HOUSINGPROGRAM SPECIFIC SUSTAINABLE DEVELOPMENT AND CLIMATE CHANGE.

CONAVI in 2008 introduced the Specific Program Sustainable Housing Development on ClimateChange as part of the activities of the Clean Development Mechanism (CDM) of Kyoto Protocol. Thisprogram, unique in its kind worldwide, will benefit not only of Certified Emission Reductions of CO2or carbon credits, but actively incorporate the country's housing sector in international efforts tomitigate climate change.

The objectives of this program include, among others: establishing guidelines for sustainable energyand environmental policies and actions promoted, financed or implemented by government agenciesand private entities planning guidelines to promote the sustainability of housing development, andgenerate additional funding housing through the Certificate of CO Emissions Reduction.

In April 2009 was developed a methodology that will allow the calculation of the baseline, themonitoring procedure and conditions of additionality. This methodology is oriented housingdevelopments that incorporate various combinations of technology for energy efficiency and finally hasbeen approved by the UN (CDM Executive Board).

If it would be possible taking advantage of this program considering the high CO GHG reductions dueto the better insulation and use of GSHP systems in Mexican houses, making more efficient buildingsin Mexico would be both, possible and profitable.

Finally, much depends on all of us that we continue to not only develop but also as a society callingthese technological alternatives that can meet our current needs without compromising those of futuregenerations.


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BIBLIOGRAPHY

Tcnicas Energticas Avanzadas, Dr. Javier Uchuengua, Universidad Politcnica de Valencia,2006.

Bombas de Calor Geotrmicas, Jos Miguel Corbern, Universidad Politcnica de Valencia,2008.

Estado Actual de la Vivienda en Mxico 2009, Primera Edicin, Gobierno Federal, 2009. Prospectiva del Sector Elctrico 2005-2014, Secretara de Energa, 2006. Gua de la Energa Geotrmica, G. Llopis y V. Rodrigo, Universidad Politcnica de Madrid,

2008.

Spitler, J.D. 2000. GLHEPRO -- A Design Tool For Commercial Building Ground LoopHeat Exchangers. Proceedings of the Fourth International Heat Pumps in Cold Climates,

Conference, Aylmer, Qubec. August 17-18, 2000.

Programa Especfico Para El Desarrollo Habitacional Sustentable Ante El CambioClimpatico, Primera Edicin, CONAVI, 2008.

Metodologa para la aplicacin adecuada de aislamiento trmico para viviendas mexicanas,Benjamn Zamudio, Universidad Autnoma de Nuevo Len, 2010.

WEBSITES

http://en.wikipedia.org/wiki/Nuevo_Len www.semarnat.gob.mx www.igshpa.okstate.edu www.designbuilder.co.uk http://apps1.eere.energy.gov/buildings/energyplus/ www.hvac.okstate.edu/glhepro/ www.javer.com.mx/

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2010 Envisci Paper Gshp