Energy is one of the most critical international issues at the moment and most likely to be so for the years to come. As part of the energy debate, it is becoming gradually accepted that current energy systems, networks encompassing everything from primary energy sources to final energy services, are becoming unsustainable. Driven primarily by concerns over urban air quality, global warming caused by greenhouse gas emissions and dependence on depleting fossil fuel reserves, a transition to alternative energy systems is receiving serious attention. Such a tradition will certainly involve meeting the growing energy demand of the future with greater efficiency as well as using more renewable energy sources (such as wind, solar, biomass, etc). While many technical options exist for developing a future sustainable and less environmentally damaging energy supply, they are often treated separately driven by their own technical communities and political groups. (Liu, 2008)
The term ‘polygeneration’ means an energy supply system, which delivers more than one form of energy to the final user, for example: electricity, heating and cooling can be delivered from one polygeneration plant. Polygeneration can involve combined co-generation (power and heat) or tri-generation (power, heat and cold) plants and /or district heating, preferably by renewable energy sources. Such polygeneration systems should be designed and controlled with a view to optimizing all relevant interactions between supply and demand. Their main benefit is in maximizing the overall efficiency of the integrated system near to the point of use. Polygeneration combined with efficient district heating and cooling may provide added benefits to a larger community. Secondary benefits may include improved reliability of the supply and distribution networks, arising from better interaction between producers and distributors. (Yang, 2013)
Explore polygeneration is an unique umbrella project and at the same time a stepwise growing demonstration case covering, from a system perspective, both the production and use of energy and all the dynamic relations in between. The polygeneration and fuel flexibility perspective is necessary to have, since in a near future the user can sometimes be a producer and vice versa. Energy storage will be a key component in this, to be able to level out effect peaks related to a highly varying demand [Explore polygeneration].
2 OBJECTIVES
The main objective of the work is to establish a library of typical load data for a representative site and evaluating the potential of renewable energy source and further this energy source will be supply for polygeneration systems (because every renewable energy system should begin with load analysis). The output of this work package is to be the first entries in the library and will, together with a few variants, form the input to simulation models and to the demo system.
These data may be used to better estimate the size required for polygeneration equipment serving the selected site. The energy use data are used first to understand the annual electric energy consumption for a given home type in a particular climatic region. Secondly, using hourly and higher resolution data, a better understanding of electrical demand may be obtained. Both annual consumption and peak demand are necessary for designing and optimizing distributed polygeneration equipment for residences.
The decision on the size and design of distributed generation equipment located in homes is influenced by numerous factors such as:
‘ The anticipated demand of the home at any point in time.
‘ The intended load(s) to be served by the generation equipment.
‘ The desired level of independence from utility sources of energy.
‘ The use of other fuel sources such as fuel gas to service some of the energy requirements.
‘ The capability of control systems to limit demand independent of generation.
3 METHOD OF ATTACK
To achieve the above objectives the following methodologies are adopted.
1. Literature review
2. Investigate the characteristics of each polygeneration subsystem.
3. Define the engineering units
4. Select a representative data source (real site)
5. Create data files. Starting with dummy data and refining stepwise.
6. Evaluating potential of renewable energy sources
7. Investigate the constraints between the subsystems
8. Store the files
9. Write a comprehensive ‘user’s manual’
10. Compiling report
4 BACKGROUND
4.1 Polygeneration concepts
Polygeneration describes an integrated process which has three or more outputs that include energy outputs, produced from one or more natural resources.
Trigeneration is a basic and most popular form of polygeneration. The term describes an energy conversion process with combined heat, cooling and power generation (CHCP). The system consists basically of a CHP (combined heat and power) module generating electricity and heat, and a thermally driven chiller generating cold. The chiller is driven with the heat delivered by the CHP. Depending on the demand, the generated heat is either used for heating or cooling purposes or both.
Trigeneration systems find application wherever the demand for heat, cold and power occurs. This means that the application area is very vast ranging from small residential, towards big commercial, office or other (tertiary, sports, entertainment centers, hospitals, schools, airports, hotels, etc.) buildings. Trigeneration can be beneficial in the food industry where often simultaneous need for cooling, heating and power exists. In buildings, the CHCP system produces heat for domestic hot water, space heating or dehumidification and cold for space cooling or air -conditioning, while in the food industry, industrial heating and cooling is usually needed (freezing, pasteurization etc.). Apart from the areas of application mentioned, Trigeneration may be an adequate solution in many other, various areas of economy.
Trigeneration systems can operate in a range of configurations. The most common and flexible system is a decentralized Trigeneration. In this case the heat and cold is generated and consumed onsite, while power is either consumed onsite or fed to grid. This principal advantage of the configuration is that the heat and cold need not to be transported, which means reduced distribution costs and losses.
Figure 1.Decentralized Trigeneration system
4.2 Investigating the characteristics of each polygeneration subsystems
The Trigeneration systems consist basically of a CHP module and a thermally driven chiller. A CHP module is a power generating unit that harnesses the waste heat. The module is composed of a generator, a prime mover and a heat recovery system.
Heat may be recovered from exhaust gases, engine cooling circuit, generator cooling circuit or lubricant circuit. Various CHP modules may find application in Trigeneration systems. Their basic characteristic is presented below.
1.3.1. Prime movers
Steam turbine
A steam turbine is a machine for generating mechanical power in rotary motion from the energy of steam at temperature and pressure above that of an available sink. The system operates on the Rankine cycle, either in its basic form or improved versions.
Steam turbine can operate in a closed cycle using water condensable vapor as the working fluid. First water is pumped into the boiler be the feed pump. The water is then heated to produce dry saturated steam. The steam is next expanded through the turbine. This process produces work along the turbine shaft. Finally the wet steam issuing from the turbine gives up heat in the condenser and returns to water to complete the cycle. The heat from expanded steam condensation is recovered.
Gas turbine
Gas turbine is a heat engine that converts some of the energy of fuel into work by using gas as the working medium and that commonly delivers its mechanical output through a rotating shaft. Typically, the gas turbine operates in the open cycle, described by Brayton cycle. Compressed air is mixed with fuel and ignited in the combustor. The resulting gases are expanded to atmospheric pressure on the turbine wheel producing shaft power connected to generator axis. Turbine elements are cooled by a cooling circuit. Heat exchangers are often used to recover heat from expanded combustion gases to pass it towards compressed air and increase efficiency of the process.
The electric efficiency ranges from 28% to 35%. Compared to the common engines, gas turbines have lower emissions. In addition to the advantage for the environment it offers easier waste heat utilization for some applications, e.g. in the drying of animal food and CO2 fertilization of plants in green houses. The investment costs are higher than for common engines.
Reciprocating internal combustion engine
The reciprocating internal combustion engine is an engine in which the combustion, or rapid oxidation, of gas and air occurs in a confined space called a combustion chamber. This exothermic reaction of a fuel with an oxidizer creates gases of high temperature and pressure, which are permitted to expand. The defining feature of an internal combustion engine is that useful work is performed by the expanding hot gases acting directly to cause pressure, further causing movement of the piston inside the cylinder. The heat is recovered from engine cooling circuit, exhaust gases and lubricant circuit.
Combined cycle generators
The term combined cycle implies any heat producing process where the prime movers employ more than one working fluid in a combination of turbines or other heat engines. The most common and practical form of such plant is the combination of one or more gas turbines with steam turbines. Heat engines are only able to use a portion of the energy their fuel generates. Combining two or more cycles such as Brayton and Rankine cycle, results in improved overall efficiency. In a combined cycle gas turbine plant, a gas turbine generator generates electricity and the waste heat from the gas turbine exhaust gases is used to produce steam to generate additional electricity via a steam turbine (Brayton -Rankine cycle).
Stirling engine
The Stirling engine is a closed- cycle piston heat engine. The Stirling engine is traditionally classified as an external combustion engine, despite the fact that heat can be supplied by non -combusting sources such as solar and waste heat. A Stirling engine operates through the use of an external heat source and an external heat sink, each maintained within a limited temperature range, and having a sufficiently large temperature difference between them. The heat waste is harnessed at heat sink. Due to the concept of an external combustion; Stirling engines have low requirements regarding the quality of the fuel.
Fuel cells
A fuel cell is an electrochemical energy conversion device. It produces electricity from external supplies of fuel (on the anode side) and oxidant (on the cathode side).
These react in the presence of an electrolyte. Generally, the reactants flow in and reaction products flow out while the electrolyte remains in the cell. Many combinations of fuel and oxidant are possible. In Trigeneration applications, mostly proton exchange membrane (PEM) and solid oxide (SO) fuel cells are used.
1.3.2. Chillers
In residential applications thermally driven chillers produce cold for space conditioning. This implies the temperature level of generated cold. For air -conditioning systems, the cold water of 6-16??C is usually required. Here, absorption and adsorption chillers are adequate.
In case of food industry application, often low temperature needs to be attained e.g. for refrigeration purposes (0 down to -30??C), therefore ammonia- water absorption machines are used.
Absorption chillers
Absorption chillers use generator/absorber heat driven circuit, instead of a compressor. Heat is supplied to the tubes of the generator causing dilute absorbent solution on the outside of the tubes to boil. Refrigerant vapor now flows through eliminators to the condenser. Hear the refrigerant is condensed on the outside of tubes cooled by a flow of water. Both processes take place in a vessel with a common vapor space at a pressure o f about 6 kPa.
The condensed refrigerant is now transported to evaporator. The liquid refrigerant boils as it contacts the outside surface of the tubes that contain water releasing the heat required to boil refrigerant. The refrigerant that does not boiled is collected at the bottom of the evaporator, pumped and prayed over the evaporator tubes again.
The dilute absorbent solution that enters the generator increases in concentration as it is boiled and releases water vapor. The resulting strong absorbent solution leaves the generator and flows through a solution exchanger where it cools down as it heats a dilute absorbent solution on its way to generator.
The cooled strong absorbent solution then flows to a solution distribution system and is sprayed over the absorber tubes. The absorber and evaporator share a common vapor space at a pressure of about 0.7 kPa. This allows refrigerant vapor from the evaporator to be absorbed over the absorber tubes. This absorption process releases heat of condensation and heat of dilution which are removed by cooling water flowing through the absorber tubes. The resulting dilute absorbent solution flows off to the absorber sump and solution pump. The dilute absorbent solution is pumped into the generator via heat exchanger where it accepts heat from the strong absorbent solution returning from the generator.
4.3 Advantages of Trigeneration
The major advantage of Trigeneration is the efficient fuel usage. In comparison with conventional power generation systems, the Trigeneration systems can be 60% more efficient. This brings a lot of benefits:
‘ More efficient fuel usage means saving fuels and money (economical benefits),
‘ Combusting less fuel less greenhouse gases is produced (climate change mitigation) and less pollution emitted to the atmosphere (environmental benefits of Trigeneration apply to the countries with fossil fuels based energy systems).
‘ consuming less fuel raises energy security of the country/region (less fuel needs to be delivered),
‘ If less fuel needs to be imported the positive impact on economy appears,
‘ Avoiding peaks / problems on the grid in summertime.
Trigeneration systems offer a significant relief to electricity networks during hot summer months when the demand for electricity reaches extreme values. Cooling loads are transferred from electricity to fossil fuel. In result stability of electricity networks is increased and the system efficiency improved since summer peaks need not to be served by electric companies through inefficient stand -by units and overloaded transmission lines. Trigeneration induces employment and enhances development of many areas of local economy like e.g. local fuel industry, agriculture (biomass), engineering, commerce, fitting, and plumbing. Apart from these mentioned above, the Trigeneration systems contribute to distributed generation development which allows:
‘ Possible usage of local energy sources like biomass, biofuels, biogas etc.
‘ Higher quality power supply at the site: a CHP station connected to the grid, where it provides or absorbs electricity, guarantees uninterrupted operation of the site, in case of the station’s breakdown or grid electricity supply interruption. On a country level, it reduces the need of installation of large electric power stations, increases the stability and facilitates balancing of the electric network of the country.
‘ Reducing environmental impact of energy systems (small energy systems have insignificant impact in comparison with large – scale, industrial power plants).
‘ Reducing transmission loses: neither electricity, nor heat, nor cold need to be transported on large distances, since they are mostly used locally.
4.4 Overview of Energy Resource and Consumption
Man’s survival has always depended upon his ability to derive adequate energy through the discovery of sources of energy to supplement the energy of his muscles. In fact, only man has been able to effectively alter his environment to suit for himself through use of energy sources (Lofteness, 1978:3). The type of energy we use and the type of fuel technology we apply can have a major impact on facilitating sustainable livelihood, improving health and education and significantly reducing poverty. Access to adequate levels of energy service is a crucial prerequisite for the development of any country (Karekezi, et.al, 1997:13). It is evidenced that, each major economic and social change in the world has been accompanied by the discovery, the availability or the technology of exploitation and social demand of new energy sources and considerable increase in the rate of energy consumption. Since the discovery of fire, energy has been a major factor in development (Colombo, 1996:53).
The first discovery and use of fire to scare away fierce animals, clear forest for use of land, cook food and keep from unfavorable cold weather condition began the long history of man’s use of energy. It enabled him to increase his food supply, improve his physical comfort, and expand the quality of his life (Lofteness, 1978:3). Exploitation of animal power about 5000BC was an essential component of the advent of agriculture and the ensuing of stable settlements, with all its social and cultural consequences (Colombo, 1996:53). During Renaissance the use of wind in sea transport and for churning mills had a profound influence and contribution to the expansion of culture and commerce. The windmill, which first appeared in Europe in the 12th century, was used primarily for pumping of water and the grinding of grain (Lofteness, 1978:5).
The major industrial development in Europe came after the invention of the steam engine that freed industry from the geographical limitations imposed by power resources and permitted location of industry either near the other primary resources or near convenient transportation (Lofteness, 1978:5). At the beginning of the 19th century, the European industrial revolution was made possible by the use of hydropower and coal as an energy source (Farinelli, 1997: 9).
The use of water as the source of energy to turn water wheels for the grinding of grain dates back in Roman times (Lofteness, 1978:102). The conversion of hydraulic energy to mechanical energy for the operation of factories reached its peak during the 17th century, at which time the steam engine came into use and permitted the location of factories elsewhere than on river banks. Hydraulic resources became important once again with the development of efficient electric generators and transmission technology that permitted location of hydroelectric plants several hundred miles from the points of energy consumption (Lofteness, 1978:102).
Electricity stimulated new forms of industry and changed the urban environment, while, especially after World War II the availability of an abundant, flexible, easy to transport and cheap energy sources, oil and natural gas, has fueled the great transformation of industrial society (Farinelli, 1997: 9).
Prior to the 17th century, the productivity of man was mainly determined by his own labor and that of domesticated animals (Lofteness, 1978:6). Since the first use of inanimate energy that provides man with a cost far below than that of animate energy sources, there has been, undoubtedly, some correlation between the use of energy and economic productivity (Lofteness, 1978:6). It is now more generally appreciated that inequalities in people’s access to resources and the resultant ways in which they use them constitute greater challenge for sustainable development (Elliott, 1999: 39). There is tremendous diversity in terms of peoples’ access to resources of all kinds. The case of energy use illustrates how inequalities in access to resources could be considered at a number of levels. The decline in the traditional use of biomass and the increased in modern energy use is viewed as an indication of socioeconomic development (Zandbergen and Moreira, 1993; Cited in Karekezi, 1997:13).
Out of the total primary energy demand in industrializing counties in 1980, 98 per cent supply was met from the modern energy sector and only the remaining 2 per cent from biomass, while the same pattern was 48 and 52 per cent respectively in the developing countries. Moreover, even within developing countries, there are extremes in which biomass serves as the major or exclusive energy source (Miller, 1986:6). On the other hand the per capita consumption of modern energy in the developing world is extremely low, relative to that in the industrial countries. For example, in the early 1990s per capita consumption of modern energy in the US was 8 tons of oil equivalent energy per year, which is 80 times more than that of Africa, 40 times more than of South Asia, 15 times more than that of East Asia and 8 times more than that of Latin America (WB, 1996: 16).
As countries grow richer, their pattern of energy consumption tends to change, and the household energy consumption share diminishes while industrial consumption grows. In the OECD countries, the two largest sectors of energy use are industry and ‘others’ (mainly residential), accounting for about 40 and 30 per cent respectively. Transportation comes next with about 20 per cent. In the poorest countries, the consumption for household purposes is dominant (Dunkerely, 1981: 38). This difference in the patterns of energy use reflects, on one hand, the inefficiency in the traditional use of biomass fuel and, on the other hand the much greater importance of the household sector, especially the dominance of the rural economy in the developing countries (Dunkerely, 1981: 39).
What matters to energy consumers is not the gross amount of energy used, but the energy services received (or ‘useful’ energy). Traditional fuels are typically used in ways that yield very low efficiencies, thus countries using primarily modern fuels yield higher efficiencies and receive more energy services for a given energy input than those, which depend largely on low efficiency traditional fuels (Dunkerely, 1981: 36). As a result, the industrial countries receive more energy services for a given input than those of the developing countries, which depend largely on traditional source of energy.
Though, it is used traditionally with low efficiency, biomass has numerous economic and environmental advantages, for the global as well as for local energy balances. Biomass fuels make no net concentration to atmospheric carbon dioxide if produced and used sustainably to allow re-growth of biomass (HABITAT, 1993:7). Globally biomass accounts for about 14 per cent of the world’s energy supply and is the most important source of energy for three quarter of the world’s population in developing countries (HABITAT, 1993:4). Developing nations obtain more than 40 per cent of their energy from biomass, more than half of this from wood fuel and even in some countries dependence on biomass fuel reaches up to 90 per cent (Miller, 1986: 5).
A number of developed countries also use biomass quite substantially. For example, the United States of America uses it nearly in equivalent amount to its nuclear power, deriving 4 per cent of the total energy from biomass. Sweden also gets 14 per cent and Austria 10 per cent energy from biomass (HABITAT, 1993:6).
The African continent is well endowed with diverse non-renewable and renewable energy resources. Despite its energy resource potential, however, Africa has, due to lack of investable capital, favorable political and economic environment, and due to lack of efficient modern technologies, these resources are not fully exploited (Farinelli, 1997: 23). Both the total and specifically modern energy use in Africa is the lowest in the world. Existing estimates of energy use in Africa indicates a significant and persistent dependence on traditional biomass energy and limited use of modern energy sources (Karekezi, 1997:1). The average per capita final modern energy consumption in Africa is less than 300 kg of petroleum equivalent, compared with 7905 kg in North America and the world average of 1434 kg (World Bank Index, 1996; Cited in Sokona, 1997:15).
In Sub-Saharan Africa traditional biomass, mainly fuel wood and charcoal, is by far the most significant fuel. With the exception of South Africa it accounts for over 70 per cent of total primary energy consumption throughout the continent, and even in some countries, such as Burundi, Burkina Faso and Ethiopia it reaches as high as 90 per cent (Farinelli, 1997:23).
In Africa the prospects of a major increase in modern energy supply are constrained by the unequal distribution of resources, which tend to be concentrated in a few countries. This spatial concentration entails large investments in distribution. On the contrary, renewable sources of energy including biomass resources are better distributed throughout the region (Karekezi, 1997:1). On aggregate, the biomass resource base in Sub-Saharan Africa is more than sufficient to cover the annual per capita demand for fuel. The potential of natural forest resources covers 22.2 per cent of the total land area and biomass resources are estimated at about 82 billion tones, which have the potential of 168.2 tons per capita (Sokona, 1997:3).
However, these aggregates conceal the considerable differences in terms of spatial resource distribution that exist within the African countries. According to FAO (1985), in 1980, 13 countries in Africa were in states of acute fuel wood scarcity, where their available supplies of fuel wood were insufficient to meet the minimum requirement. And only 6 countries were with surplus potential for wood based energy (Miller, 1986:8).
5 REPRESENTATIVE SITE SELECTION IN RESIDENTIAL SECTOR
Urbanization is defined as the shift from a rural to an urban society, involving an increase in number of population of urban areas and results a stressed environment. With the high rate of social and economic development and the resulting growth of city population, lack of infrastructure, congested traffic, environmental degradation and a housing shortage became the major issues faced by many cities in their sustainable development (WHO, 1987).
Africa also continually faces significant challenges such as rapid urbanization, declining agricultural production, political instability, etc., which have negative implications for sustainable development. Some of the implications of rapid urbanization include increasing unemployment, lack of urban services, overburdening of existing infrastructure, lack of access to land, lack of shelter, increasing violent crime, and environmental degradation (Brooke et al., 2009).
Having a history of 3000 years, Ethiopia is one of the ancient Sub Saharan African countries located strategically in the horn of Africa. It has a population of about 90,873,739 CIA estimate (2012) with an annual population growth rate of 2.73%. Its capital, Addis Ababa, is a fast growing urban center with a current estimated population of over 3 million inhabitants and area of 540 sq. km. Regarding the climatic condition of Addis Ababa; the lowest and the highest annual average temperature is about 13oc and 25oc, respectively (Nicolas et al., 2010).
The city is the dominant political, economic and cultural city of the country and melting pot of different nations, nationalities and several international organizations. It is among the least urbanized cities of the world. However, it is one of the cities where high urbanization, 8% per annum, is taking place. The demographic growth rate ranges between 2.1- 3% per year. The city was reached the status of a megacity with the assumption of 3.5 million inhabitants in year 2010 and 4% population growth after 2035 (Yewoineshet, 2007).
According to United Nations, a megacity is a metropolitan area with a total population of more than 10 million. Some definitions also set a minimum level for population density (at least 2,000 persons/square km). Megacities already face difficulties associated with high population number, uncontrolled urban spreading, high levels of traffic, insufficient infrastructure and insufficient housing (Nicolas et al., 2010).
Addis Ababa also face problems which afflict most cities in the developing world, including extensive poverty, unemployment, severe overcrowding, very poor housing condition, undeveloped physical infrastructure, pollution, inadequate water supply and sanitation, inadequate solid waste management, insufficient health care, low coverage electricity (Meheret, 1999).
5.1 Condominium Housing in Ethiopian Context
The idea of condominium housing is a new phenomenon in Ethiopia. It emerged as a strategic response to rapid urban population growth, high prevalence of urban poverty, and urban unemployment in major Ethiopian cities; because only 30% of the urban house was regarded to be in fair condition. It also solves housing shortage and the ever increasing gap between the demand and supply of housing in the country (Emaculate et al., 2010).
The Addis Ababa City Housing Development Project office has launched its activities by constructing 750 model houses in 1996 E.C. Two years later, the office has launched a five year Integrated Housing Development Program (IHDP) in line with the national program (AACHA, 2006).
The program has brought a remarkable change in the image of the city, improving the way of life of city dwellers. There has been a massive supply of housing units within small space, large number of job opportunities for a number of people. It has also strengthened the informal sector by providing adequate working place, training and credit facilities. Moreover, it has arranged affordable modalities for all groups and brings attitude changes such as saving culture (Emaculate et al., 2010).
The condominium houses are mainly G + 4 block structures. Each block contains between 125 and 130 housing units. The house typologies are studio, one bedroom, two bedrooms and three bedroom units. The condominium housing project design tried to consider provision of different service facilities within the various neighborhoods such as coffee ceremony spaces, children’s play ground, green field, car parking and communal kitchen used for animal slaughtering, coffee grinding, and spice drying ( Franziska et al.,2008).
5.2 Distribution of condominium house in the country
The following table shows that the distribution of condominium housing units in the country
Region Towns Transferred Units
Tigray 12 9,624
Afar 1 200
Amhara 12 20,314
Benshangul 1 42
Diredawa 1 2,838
Addis Ababa 1 78,000
Gambela – Planning stage
Harar 1 2,445
SNNPR 12 11,624
Oromiya 17 22,834
Somali – Planning stage
Source: (UN-HABITAT, 2010)
Table 1: National distribution of condominium projects in Ethiopia
5.3 Distribution of condominium housing in Addis Ababa
In 1998, the municipality constructed and transferred the first round condominium housing units to beneficiaries. The total number of sites and houses in the first round were 103 and 32,216, respectively (Emaculate et al., 2010). Also in 1999 the second round built and transferred to beneficiaries in 16 sites of 46,031 total housing units. Currently, a total of 77,430 housing units have built and transfer to the city population. The municipality also plans to build in the coming years in the selected sites where open spaces are available (AACHA, 2006). Below is a table that show total condominium houses transferred to beneficiaries, being built and will be built in the future.
Sub-city Number of sites and housing units in 1st round Number of sites and housing units in 2nd round Number of sites and housing units being built currently (in 2003) Sub-city in which the house will be built in the future(2004)
Total sites Total housing units Total sites Total houses Total sites Total houses ‘
Arada 19 2,253 – – – – *
Addis Ketema 9 1,550 – – – – *
Lideta 9 1,676 – – 1 2,000 *
Kirkos 14 1,965 1 2,433 – – ‘
Yeka 12 3,050 4 1,134 1 8,712 *
Gulele 7 1,464 – – – – ‘
Kolfe 9 8,619 – – – – ‘
Nifas silk 10 5,286 6 22,443 – – ‘
Bole 9 4,234 3 15,476 – – ‘
Akaki 5 1,302 2 4,545 1 6,280 ‘
Total 103 31,399 16 46,031 3 16,992
Source: Addis Ababa Housing Agency (AACHA, 2006)
‘ Sub-city built in the future and * sub-city not built in the future
Table 2. Distribution of condominium houses in Addis Ababa city
Conclusion
Based on the above points the representative site at this time and for the future will be condominium housing, because it will cover 70% of the city population. For the study Jemo condominium site is selected the site has around 30,000 housing units, Some Blocks will be randomly selected.
5.4 Detail information of the selected site
5.4.1 Construction materials of houses
The condominium blocks are constructed from a frame of reinforced concrete (a mix of in-situ and pre-cast) with masonry infill walls, plastered both inside and out.
Units are handed to beneficiaries with skim concrete floors to reduce costs for the government. Windows and doors are made from metal frames with single glazing.
The modular design reduces construction times and allows for the repetition and adaptation of designs across projects. The design utilizes standard sizes of materials therefore reducing costs further (for instance standard hollow brick dimensions are kept to remove the need for cutting them to size). (UN-HABITAT,2010)
The housing programme was the first in Ethiopia to employ pre-cast concrete for beams, floor-slabs and in some designs, internal staircases. The blocks have a predicted lifespan of 100 years. The seismic capacity of the designs are tested and verified using a computerized earthquake simulation tool.
Figure 2.Jemo condominium house
5.4.2 Break down of housing units in each block and floor plans
The condomium houses in Ethiopia are manily G+ 4 structures. Each block contains between 125 and 130 housing units. The house typologies range from studio, one bedroom, two bedroom and three bedroom units; which have the dimensions shown in the table below.
Unit type Floor area(mm2) Percentage in each block
Studio <20 20
1-bed 20-30 40
2-bed 30-45 20
3-bed >45 20
Table 3 : Size of condominium house typology (Source: Addis Ababa Housing Agency (AACHA, 2006))
Figure 3. Condominium Block Typical Floor Plan, SNNPR. MH Engineering
5.5 Methods of Data Collection
Both quantitative and qualitative data from primary and secondary sources will be gathered and analyzed. A combination of the following data collection methods will be employed for the study.
4.5.1 Household Sample Survey
Conventional household survey will adopt for the study as the main method designed to gather quantitative information from sample households. Three enumerators is assigned to conduct the household survey using the structured questioner.
4.5.2 Focus Group Discussion
Focus group discussions with senior, knowledgeable and well-experienced residents of Jemo site is one of the qualitative data collection method employed for the study. The discussion will be undertaken with two groups that comprise both adult and elderly men and women, within the range of 6 to 10 individuals for each focus group.
4.5.3 Key Informant Interview
Individuals who are considered knowledgeable and rich in experiences about household energy and socioeconomic condition of the residents in Jemo site will be identified and interviewed. The key informants interviewed will include professionals from different governmental and non-governmental organization, Zonal and Municipal officials’. In addition to the formal interviews, personal experiences and observations of the researcher facilitated the understanding of the overall conditions related to domestic energy use and related significant factors and constraints in the area.
4.5.4 Secondary Data Collection
By reviewing relevant books and journals, published and unpublished documents the researcher collected secondary data and use the information primarily to set the research context and also to relate the research findings with other empirical studies on the subject of the study.
4.5.5 Methods of Data Analysis
The data collected through various methods will be presented and analyzed using appropriate descriptive and quantitative methods, such as mean, range, percentage