Kitabı oku: «Water and Energy Engineering for Sustainable Buildings Mihouse Project»
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© Universidad Autónoma de Occidente
Autores
© Javier Ernesto Holguín González - Yuri Ulianov López Castrillón
Alejandro Beltrán Márquez, Ana María Ramírez Tovar, Andrea María Quintero Osorio, Andrés Felipe Ramírez Vélez, Daniel Mauricio González Naranjo, Diego Fernando Gómez Etayo, Eliana Melissa Morales Rivera, Fabián Andrés Gaviria Cataño, Hugo Andrés Macías Ferro, Isabella Tello Gómez, Javier Eduardo López Giraldo, Jeffer Steven Mosquera Castillo, Juan Manuel Luna Rodríguez, Juan Pablo Aguir, Juan Pablo Trujillo Chaparro, Juliana Alexandra Muñoz Lombo, María Camila Calle Mena, Mariana González Zuluaga, Nicolás Noreña Leal, Wilson Eduardo Pabón Álvarez.
Water and Energy Engineering for Sustainable Buildings Mihouse Project
Primera edición, 2020
ISBN impreso: 978-958-619-040-4
ISBN Epub: 978-958-619-041-0
ISBN pdf: 978-958-619-042-8
Cali, Valle del Cauca, Colombia
Km. 2 vía Cali-Jamundí, A.A. 2790,
Elaborado en Colombia
Made in Colombia
Gestión Editorial Director de Investigaciones y Desarrollo Tecnológico
Alexander García Dávalos
Jefe Programa Editorial
José Julián Serrano Q.
Coordinación Editorial
Pamela Montealegre Londoño
Corrección de estilo
Fernando Alviar
Diseño y diagramación
CMYK Diseño e Impresos S.A.S.
Water and energy engineering for sustainable buildings: mihouse project / editores académicos Javier Ernesto Holguín González Yuri Ulianov López Castrillón.-- Primera edición.-- Cali: Programa Editorial Universidad Autónoma de Occidente, 2020. 121 páginas, ilustraciones.—(Colección investigación)
Contiene referencias bibliográficas.
ISBN: 978-958-619-040-4
1. Arquitectura sostenible. 2. Construcción sostenible. 3. Casas ecológicas. 4. Energía solar. I. Holguín González, Javier Ernesto, editor. II. López Castrillón, Yuri Ulianov. III. Universidad Autónoma de Occidente.
720.47- dc23
El contenido de esta publicación no compromete el pensamiento de la Institución, es responsabilidad absoluta de sus autores. Este libro no podrá ser reproducido por ningún medio impreso o de reproducción sin permiso escrito de las titulares del copyright.
Personería jurídica, Res. No. 0618, de la Gobernación del Valle del Cauca, del 20 de febrero de 1970. Universidad Autónoma de Occidente, Res. No. 2766, del Ministerio de Educación Nacional, del 13 de noviembre de 2003. Acreditación Institucional de Alta Calidad, Res. No. 16740, del 24 de agosto de 2017, con vigencia hasta el 2021. Vigilada MinEducación.
Diseño epub: Hipertexto – Netizen Digital Solutions
Credits and Acknowledgments
The MIHOUSE team wants to thank the Faculties of Engineering, Economic Sciences and Social Communication at the Universidad Autónoma de Occidente (UAO) and Architecture at the Universidad de San Buenaventura (USB) that supported the development of the project:
The Energetic and Mechanics Department at UAO, which provided the electrical, environmental, and waste and water management solutions.
The Architecture Program at USB, which leaded the project, developed the design strategy and managed MIHOUSES´s research and building processes.
The Faculty of Engineering at USB, which helped with industrial and agro industrial solutions and in the preparation of most of the multimedia content used in social networks, website, and public releases.
The Communications Departments, which contributed to the team’s communications project.
The Research & Technological Development Departments.
The deans of the Faculties of Engineering and Architecture, Arts & Design for their constant support and encouragement.
The heads of each of the study programs involved in the project who facilitated the participation of an interdisciplinary group of students and professors.
The Language Center and Language Institute for their constant support with translations used in every delivery during the SDLAC2015 contest.
The FabLab at UAO, which facilitated the construction of urban and architectural models.
The Broadcasting Coordination at USB that helped with the preparation of all audiovisuals.
Costume Design students who designed the uniforms of MIHOUSE decathletes.
Arch. Liliana Carvajal for helping with the financial aspects of the project and for her unconditional support.
Professors José Salazar and Jerfenzon Vidarte for their advice on the project´s economic feasibility.
Professor Luis Alberto Buitrago for his advice on urban orchards and home gardens.
Arch. Lucas Arango and his team; Eng. Carlos Castang and his group of students; and Arch. Carlos Giraldo for their contributions with the bioclimatic aspects and calculations.
Teacher Carlos Ortega for his support with translations.
The Maestría en Bioclimática at Universidad de San Buenaventura Medellín.
The MIHOUSE team also recognizes the enormous support from its sponsoring companies and hopes that the established relations can continue being fruitful over the next years and in future projects:
It is also important to thank USB and UAO for their valuable efforts that made possible the disassembly of the MIHOUSE prototype constructed at the Solar Villa and its reassembly at USB campus, where it is being turn into a Sustainable Housing Laboratory. In the next years, the MIHOUSE Laboratory will serve as a place for research and experimentation with solar panels, furniture and other innovative technologies related to energy efficiency, indoor air quality, humidity, water management and sustainability. Undoubtedly, this laboratory will be a milestone that will allow the training of architecture and engineering students in future Solar Decathlons.
Last but not least, the MIHOUSE team wants to thank the Solar Decathlon organizers for making possible this event, and the people of Cali that kindly selected our housing prototype as the second favorite house in the Solar Villa.
List of the Mihouse Team
Contents
List of Figures
List of Tables
Introduction
Chapter 1 - Construction Design
Urban Scale
Prototype Scale
Chapter 2 - Water Management System
System Design
Design Criteria
Storage
Rainwater Volume Calculation
Ground Water System
Drinking Water Tanks
Plumbing System
Water Budget
Chapter 3 - Energy Management System
Electrical System Design
Solar Energy Resource
Energy Efficiency Design Narrative
Technical Project Manual
Project Dimensions:
AC Systems
Domestic Hot Water
Electrical Energy production
Energy Consumption
Energy Balance
List of singular and innovative materials and systems
Chapter 4 - Innovation
Innovation in Engineering and Construction
Lightweight Concrete
Thermal Conductivity
Water Use Reduction
Innovation in Energy Efficiency
Innovation Through Energy Efficiency.
Benefits of efficient selection of components of the electrical and photovoltaic system equipment.
Benefits of deployment of control sensors step.
Use of Natural Light
Use of Led Lighting
Chapter 5 - Sustainability
Introduction
Water Strategies
Water Cycle
Catchment
Distribution and use
Reuse
Outputs
Solid Waste Management
Rainwater
Greywater
Solid waste
Materials
Lightweight Concrete with Addition of Stone Coal (PC)
Calculation of Ecological Footprint
Life Cycle Stage Analysis
Making of materials
Solar Facilities
References
Footnotes
List of Figures
Figure 1.1. Mihouse urban proposal
Figure 1.2. Prototype Scale
Figure 1.3. Main Table and Central Table
Figure 1.4. Mihouse Prototype design
Figure 1.5. Assembly of the modules up to the completed building
Figure 2.1. Sloping Slabs
Figure 2.2. Prototype rainwater tank
Figure 2.3. System components groundwater
Figure 2.4. Technical data of low consumption toilet
Figure 2.5. Greywater storage for apartment blocks (zone 1)
Figure 2.6. Greywater storage for apartment blocks (zone 2)
Figure 2.7. Flowchart for greywater treatment system
Figure 2.8. Prototype greywater storage.
Figure 2.9. Drinking water distribution system
Figure 3.1. The Solar Village location
Figure 3.2. Meteorological span figures from 10th November until 10th of December 2014
Figure 3.3. Solar radiation and temperature in an specific day
Figure 3.4. Components and energy flow on a solar PV grid connected system
Figure 3.5. Rooftop with the solar PV system
Figure 3.6. Solar grid-connected inverter
Figure 3.7. Panel technical information
Figure 3.8. System metrics
Figure 3.9. Monthly Production
Figure 3.10. Sources of loss
Figure 3.11. Condition Set
Figure 3.12. Components
Figure 3.13. Wring Zones and field segments
Figure 3.14. System Connection
Figure 3.15. Simulation results, cash flow summary
Figure 3.16. Simulation results, cash flow
Figure 3.17. Monthly Average Electric Production
Figure 3.18. PV Output
Figure 3.19. Primary Load
Figure 3.20. Grid sales
Figure 3.21. PV power
Figure 3.22. Frame for a flat roof
Figure 3.20. Heater components
Figure 3.23. Energy Balance Simulation
Figure 3.24. CO2 Emissions Simulation
Figure 4.1. Lifecycle analysis of materials
Figure 4.2. Lightweight concrete
Figure 4.3. Lightweight concrete production process
Figure 4.4. Energy Efficiency strategies for sustainable social housing in developing countries
Figure 4.5. Efficient selection of photovoltaic equipment
Figure 4.6. Energy rating label
Figure 4.7. Comparative between incandescent and LED lightning
Figure 4.8. Benefits of good lighting in each scene
Figure 5.1. Location of the TSU and waste use areas
List of Tables
Table 2.1. Type A apartment data
Table 2.2. Values of the necessary variables for the calculation of the catchment area, water demand and water supply
Table 2.3. Calculation of maximum flow that transports the gutters in the apartment
Table 2.4. Maximum permissible flows in downspouts
Table 2.5. Number of required drainpipes
Table 2.6. Results of the monthly average precipitation, monthly water demand and water supply, and calculation of the demand and accumulated supply and storage volume
Table 2.7. Greywater consumption
Table 2.8. Devices that generate greywater at home.
Table 2.9. Apartments Distribution by type
Table 2.10. Storage volume for the Drinking water tank
Table 2.11. Drinking Water Pre-dimensioning
Table 2.12. Activities related to the water consumption
Table 2.13. Daily Cycles
Table 2.14. Total generated volume of water
Table 3.1. One-year time series detailed analysis of Mihouse electrical load
Table 3.2. Monthly Averaged Insolation Incident on a Horizontal Surface (kWh/m2/day)
Table 3.3. Top manufacturers
Table 3.4. Available surfaces
Table 3.5. Estimation of area per living unit module
Table 3.6. Energy load requirements per living unit
Table 3.7. Energy consumption during a regular day
Table 3.8. Annual Production
Table 3.9. Electric and Photovoltaic – special chart
Table 3.10. Characterization of total energy consumption in the competition’s house
Table 4.1. Comparative table of lightweight concrete and structural concrete
Table 4.2. Different properties between conventional lightweight concrete
Table 4.3. Comparison of Consumption Among incandescent lighting and LED lighting
Table 5.1. Estimation of the amount of waste generated in the residential condo
Table 5.2. Cost savings Mihouse complex, using the rainwater and groundwater exploitation system
Table 5.3. Mihouse project viability on saving resources
Table 5.4. Savings in pesos of Housing and Urbanization
Table 5.5. Waste quantity generated by the residential unit
Table 5.6. Quantity and valorization of waste to be exploited
Table 5.7. Calculation of the ecological footprint generated in the construction phase
Table 5.8. Calculation of the ecological footprint generated by transporting supplies and raw materials
Table 5.9. Calculation of the ecological footprint generated by transporting construction waste
Table 5.10. Calculation of the ecological footprint generated using the prototype
Table 5.11. Calculation of the ecological footprint generated by the use of the demolition of prototype
Table 5.12. Calculation of the ecological footprint of building materials associated with the life cycle analysis
Table 5.13. CO2 Emission FACTOR per kWh
Table 5.14. Emission per Technology
Introduction
Globally, the concern for climate change has led governments and the community in general to consider the affectations that we as humans have been doing to the planet. The production of electricity is a relevant factor due to the pollution produced by fossil fuels used for this purpose. The excessive industrial production to cover the growing demands of products and services, combined with the disproportionate use of transport systems that use internal combustion engines responsible for the thousands of tons of CO2 equivalent release to the atmosphere, and the deforestation without control, are also part of the driven forces for global warming and climate change. On the other hand, oil as a king fuel, which moves the world economy, are numbered as it has already been reported, due to the few world reserves. This is affecting the oil companies and the countries with economic support from these companies, like it can be seen in the cases of Ecopetrol in Colombia, PDVSA in Venezuela and Repsol in Spain.
All of the above, is creating a growing interest in the environmental sustainability of the planet, humanity and obviously the resources that are owned by. It is for all these factors that the use of renewable energy resources, such as the sun, for energy production, and the application of new and more efficient construction technologies, are altogether the basis for the integral design of sustainable urban projects. The design and implementation of Sustainable Housing, which is the result of this project, uses solar energy as a source of electricity and reduces the use of natural resources, by promoting the reuse of wastewater, the use of rainwater and the recycling and use of solid waste. This house has been built with constructive processes that are friendly to the environment using renewable and local construction materials with a long-life cycle and low ecological footprint, such as concrete and plastic wood. Additionally, the house works with passive lighting and ventilation systems, reducing the energy consumption and the environmental impact during the operation of the building.
In order to promote knowledge concerning technologies that could be used in the construction of houses that take advantage of solar energy, since 2002, the US government is supporting the international university competition Solar Decathlon, which was held for the first time in 2015 in Latin America and in which the authors participated with the Mihouse project.
The Mihouse project is the result of an interinstitutional and interdisciplinary work developed by professors and students from the faculties of engineering, economic sciences and social communication of the Universidad Autónoma de Occidente (UAO) and architecture at the Universidad de San Buenaventura (USB) both located in Cali, Colombia. Within the framework of this project, students from the UAO Renewable Energy and Integrated Water Resource Management research groups participated in this project, both in charge of the UAO professors. As a result of this project, two publications have been developed; the first one focused on sustainable architecture and bioclimatic architecture (Villalobos, Cobo, y Montoya 2018) and the second one focused on water and energy engineering for sustainable buildings (i.e. this document).
Chapter 1
Construction Design
Mariana González Zuluaga1
Juliana Alexandra Muñoz Lombo1
Juan Pablo Aguirre1
Diego Fernando Gómez Etayo2
Javier Ernesto Holguín González3
Yuri Ulianov López Castrillón3
Urban Scale
The Mihouse urban project consists of common areas with buildings with four to five stories formed by groups of apartments. These buildings can be replicated depending on the place, the density requirements and the types of urban blocks (Figure 1.1 right).
Figure 1.1. Mihouse urban proposal
Note: (left) Mihouse urban proposal, (right) Mihouse urban proposal in the neighborhood.
Source: The Authors.
The whole residential condominium would be composed by 30 buildings surrounded by eight parks destined for different uses like landscape contemplation, parks for recreational activities, among others (Figure 1.1 left). Also, the whole urban compound would be surrounded by 4 blocks.
Prototype Scale
Figure 1.2. Prototype Scale
Note: Process of post-war reconstruction
Source: The Autors.
The project Mihouse constructive system is based on the prefabrication of prestressed concrete structural elements, recognized advantages in the construction of mass housing at reduced costs and widely used in many experiences in our country. On the other hand, the seismic condition of Cali, located in the western region of Colombia, which is part of the so called “Ring of Fire”, known worldwide for its high probability of major earthquakes, requires the construction of buildings with high resistance to such natural events and precisely with material that provide the proposed structural safety system required in these cases (Figure 1.2).
This criteria, paired with the high sustainability of the chosen materials and the principles of constructive and structural efficiency, has hallowed to propose the Mihouse project as a building that can be shaped primarily by two prefabricated structural modules in prestressed concrete. These concrete modules can be conveniently repeated and assembled together and they define the spatiality of the housing units and the number of floors required for the technical feasibility of the proposal.
For identification, we have given the name “Main Table” and “Central Table” at Figure 1.3.
Figure 1.3. Main Table and Central Table
Main Table - Central Table
Source: The Authors.
Resting on a foundation of reinforced concrete plate, which must be designed according to the type of terrain that applies in each case, the main structure of the building is resolved as a stack of these basic structural modules, linked together by mechanical fasteners that provide and ensure its comprehensive action to support vertical loads and horizontal seismic forces. Along with a perfect assembly of the constituent parts, this new system excludes the need to dry joint, which is one of the most critical points in the traditional way as usually these structures are resolved.
The following Figure 1.4 shows the design of the prototype of the apartment located at the top floor of the building at the residential condominium, the process of assembly of this house would be first the junction of the modules shown in Figure 1.3 through high resistance mechanical anchors, then the installation of the ramp, steel orchard, Teak wood blinds, the green wall structure and the plastic wood deck, would be made forming the residence shown in the Figure 1.4.
Figure 1.4. Mihouse Prototype design
Source: The Authors.
In addition to the residence prototype, the following sequence shows the assembly of the modules up to the completed building, and conceptually illustrates high construction efficiency of the proposal.
Figure 1.5. Assembly of the modules up to the completed building.
Source: The Authors.
Wall lengths resulting in each orthogonal direction of structural plant generate a high regularity in response to earthquake resistant assembly being confluent in perfect symmetry and the center of mass and rigidity, thereby providing high reliability in evaluation of earthquake resistant building in the light of the rules required by the Colombian Earthquake Resistant Building Regulations NSR-10, mandatory in our country (Figure 1.5).
Chapter 2
Water Management System
Daniel Mauricio González Naranjo1
Alejandro Beltrán Márquez1
Javier Eduardo López Giraldo1
Jeffer Steven Mosquera Castillo1
Juan Pablo Trujillo Chaparro1
Nicolás Noreña Leal1
Javier Ernesto Holguín González2
System Design
In this project we considered the rational use of natural resources; therefore, our proposal is to have an integrated water management system that allows us to have sustainable solutions such us: (1) to reduce the consumption of drinking water; (2) to treat and to reuse the greywater for flushing the toilet; (3) rainwater exploitation. In the following section, the strategies for each element of the plumbing system design are described.
The plumbing system is composed by four main components:
• Water tanks: composed by 66 tanks (2 underground drinking water tanks, 2 underground greywater tanks, 60 elevated rainwater tanks and 2 underground rainwater tanks),
• Pumping system: composed by 6 pumps (2 for taking the water from the underground drinking water tanks to the utilities, 2 for taking the water from the underground rainwater tanks to the irrigation system and 2 for taking the water from the greywater tanks to the toilets),
• Conduction and discharge pipes (for hot and cold drinking water, rainwater, greywater and black water),
• Greywater treatment system and drinking water meters.
Design Criteria
The criteria considered for using and reusing water was developed based on an objective, which is the adoption of alternative sources of water. In the following paragraphs a detailed description of the water storage tanks, and the plumbing system considered in the technical proposal for Mihouse project is presented.
Water storage tanks – Rainwater. In general, a rainwater exploitation system for domestic use should have three main sub-systems, a rainwater collection sub-system, an interceptor sub-system and a storage sub-system. These three main sub-systems are composed by several elements such as: a) roof’s catchment, b) collection by gutters and downspouts, c) a first flush rainwater interceptor, d) storage tanks, e) a physical treatment unit and, f) a distribution system.
The use of rainwater in this project aims to satisfy the basic needs of the people living in these apartments related to the use of non-potable water (washing floors, watering of plants and so on). Our proposal consists of two elevated storage tanks which are located on top of the roofs and that will be fed by a system of gutters. The rainwater collected in these tanks is afterwards conducted to each apartment. Additionally, the water which is not collected in the storage tanks is drained to the 2 underground rainwater tanks.
The capacity of the two elevated storage tanks is 216 liters. Each of these tanks has the following dimensions: 0,30 cm high, 0,60 cm wide and 0,60 cm long. It should be emphasized that the storage capacity varies because part of the water can be stored along the pipeline or it can decrease due to evaporation of the water. The rainwater collected in these tanks is conducted by gravity to each apartment through a pipe of ½ inches and it may be supplied by a tap located 30 cm above the floor just below the sink and next to the laundry machine.
Each of the buildings has this exploitation system for the rainwater. This system will allow people to reduce water consumption. The total storage capacity associated with elevated tanks is about 6480 liters, distributed in 60 tanks, 2 tanks in each of the 30 buildings of the residential complex.
Technical and Economic Factors. From the technical perspective, it should be considered the water demand and the water availability, which is closely related to rainfall during the year and the seasonal variations of it. So, it is essential to work with the rainfall information provided by the competent authorities at the time of designing the catchment system. Moreover, due to the water demand and water availability by rainfall there is a direct relationship between supply and demand for water, which defines the size of the catchment area and the storage volume. Both considerations are intimately connected with the economic aspects, which may preclude access to a collection system of this type.
The implementation of a groundwater system involves knowledge about the type of soil, nearby sources of pollution, large machinery and infrastructure cost. Moreover, it is necessary a rational use of groundwater because an excess of demand could affect the natural ability of the system to recharge.
System components
• Rainwater Catchment: The area where the project is located has a direct relation with the possible rainwater harvesting. The catchment system is implemented in the roofs of the buildings, by using gutters, tiles, etc.
• Interceptor and rainwater driver: It is a fundamental part of the system collecting rainwater, they are responsible for driving the collected water to the storage tank.
• Collection and conduction gutters: Gutters are accessories to collect and to conduct storm water runoff to a storage system; its dimensions are a function of the duration of precipitation (short and homogeneous), the water concentration time, the length of the passage area and its slope.
In a catchment area, the water concentration time is a fundamental parameter in the hydrological study of a watershed and runoff areas with slope. This time is described by mathematical expressions which, considering physical characteristics of the catchment area or basin, can provide a resultant hydrograph.
Below, are shown the equations for determining the gutter flow transported, depending on the precipitation time, draining and other factors:
1. In order to calculate the concentration time (tc), we used the Kirpich’s formula:
where: S: is the average slope; L: is the length of the catchment area in meters; tc: concentration time in hours.
2. Time in which the maximum runoff is reached in the basin or catchment area (tp):
where: D is the duration of effective rainfall in hours.
If the duration of daily maximum precipitation is unknown, the following equation is used:
3. Concentration Time of the maximum flow (tb). It is estimated for draining all the surface runoff from impervious catchment area, it is estimated by the following equation:
4. The maximum Flow (Qp). The maximum flow expected to net precipitation in the draining area is estimated by the following expression:
where: P is the effective precipitation (mm); A: catchment area (km); 0278: conversion factor (m3/s).
5. Estimation of the gutter area. The water that flows in the conduction gutters behaves as a spatially varied flow, because this water is gradually collected over of the gutter. In order to determine the required conducting area, we used the continuity equation, in which only the area is unknown and average speeds of 0,9 m/s on slopes 2-4 % and 1,2 m/s on slopes 4-6 % are assumed.
where: Qp: channel flow (m3 s); V: Gutter flow velocity (m s); A: cross sectional area (m2).
6. Storage volume (VA). The required volume for storing rainwater (VA), is given by the difference between the accumulated rainwater available (OA) and the accumulated water demand per month (DAM’) (Eq. 7). The highest value of (VA) is the value adopted for the tank volume. If (VA) has a negative value; it means that catchment areas are not enough to satisfy the rainwater demand.
where: VA: storage volume for the “i” month (m3); OA: accumulated rainwater offered for the “i” month (m3); DAM’: accumulated rainwater demand for the “i” month (m3).
7. Accumulated Offer (OA). It is given by the following equation:
where: OA: accumulated offer for the “i” month (m3); OA’: previous month accumulated offer “i-1” (m3); OAMP: accumulated offer for the “i” month considering losses (m3).
The accumulated offer per month (OA) will be included in the equation 7 and thus we can determine the storage volume for the rainwater collection system.
8. Water offer in a month (OAM). Considering the average monthly rainfall during the evaluated years, we proceed to determine the quantity of rainwater collected per month.
where: OAM: rainwater offer in the month “i” (m3); P: average monthly precipitation (l/m2); C: runoff coefficient (0,9); A: catchment area (m2).
In order to find the rainwater offered of the month considering the losses (OAMP), it is necessary to estimate the rainwater available during the month (OAM), both terms are used in Equation 10. It is noteworthy that the runoff coefficient in the Mihouse project takes the value of 0,9, because it is associated with metallic surfaces, which do not resist the flow direction. This feature matches the characteristics of solar panels on the roof of the buildings and the prototype house, moreover, it is important to note that the catchment area is function of the roof surface of the buildings, which in the urban complex consists of three different models.
9. Month Offer “i”, considering losses (OAMP). According to Abdulla and Al-Shareef (2006), one can assume a value of 20 % of annually rainwater losses because of evaporation, the storage and an inefficient collection system. For this reason, the volume of the available supply is affected for that percentage. This will prevent oversize the system and include in the design related losses.
where: OAM: rainwater offer in month “i” (m3); OAMP: Accumulated offer of the month “i” considering losses (m3).
10. Pluviometric information. In order to design the rainwater exploitation system, we should have the rainfall information in the study area, and it should be at least from ten consecutive years. With the obtained daily data, the monthly average precipitation is estimated, in accordance with Equation 5. With these results, we can analyze if the available rainwater is enough to implement a system to capture rainwater to fulfill the necessities of the project. Furthermore, the equation 11 is employed for obtaining Ppi which will be necessary to develop Equation 9.
where: P: monthly precipitation average (l/m2) of the “i” month evaluated every year (mm/month); n: number of evaluated years; Pi: Monthly precipitation value “i” (mm).
11. Water catchment coefficient. The efficiency of the rainwater catchment depends on the runoff coefficient of the materials used for the catchment area, which varies from 0,0 to 0,9.
12. Monthly Water Demand (DAM). The water demand can be estimated in several ways, the most common is by using the water endowment assumed by a person or the used for irrigation. This method calculates the amount of water needed to meet needs in each month.
Where: DAM: Monthly demand (m3); Dot: water endowment (l/irrigation/day) (2l/m2); N: total irrigation area; N: number of days in the analyzed month u d.
13. Accumulated demand per month (DAM’). It is determined by the expression proposed by Abdulla and Al-Shareef (2006). The (DAM’), is introduced in Equation 7 in order to determine the volume of the storage tank for rainwater.
Where: DAM’: accumulated demand per month “i” (m3); DAM: Month water demand (m3); DAM (i-1): accumulated demand from the previous month (m3).
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