1.2 Problem Statements
In order to cover buildings’ air-conditioning demand, both electrically and thermally operated cooling systems are available in the market. Conventional air conditioning technology is dominated by Vapor Compression Refrigeration (VCR) systems. Such a system relies on the phase change property of certain liquids called refrigerants to provide cooling on the evaporator side and heating on the condenser side (IEA, 2018). VCR systems have been in the market for a long time now, making these machines very economical and readily available in almost any size globally (IEA, 2018). Commonly used cooling technologies handle sensible and latent loads together. Dehumidification in these systems is achieved by cooling the air below its dew point, which results in condensing of the moisture and eventually providing the desired degree of dehumidification (Ahmed et al., 2005). However, this process of dehumidification often leaves the supply air cooled beyond the required room setpoint (Ahmed et al., 2005), making the system energy-intensive and inefficient when handling air with high moisture content (Fan et al., 2019)(Jani et al., 2016). The increase in summertime peak cooling demand of buildings also increases the peak load as well as total annual energy consumption because of the VCR system, placing additional stress on the electrical grid (Guo et al., 2017), and indirectly increasing the CO 2 and GHG emissions (IEA,
Khalid et al. (2009) conducted experimental study on solar powered pre-cooled hybrid desiccantcoolingsystem for comfort space cooling. The model was simulated by use of TRNSYS. Payback period and life cycle assessment were performed for evacuated tube solar thermal collectors. La et al. (2011) experimentally investigated the performance of a two-stage desiccantcoolingsystem combined with a traditional vapor compression air-conditioner. The solar collector was used for regeneration heat. Using TRNSYS simulation tool, the system performance was investigated under hot & humid weather conditions. The power consumption was reduced up to 36%. Sukamongkol et al. (2010) experimentally regenerated the desiccant wheel using the waste heat of heat and a Photo voltaic thermal air collector. It was found saving of 19% on the energy use of the coolingsystem. Solar powered soliddesiccant-basedcoolingsystem was simulated by La et al. (2011) using TRNSYS. Substantial energy savings can be achieved by use of solar heat for regenerating the desiccant wheel.
Due to the exibility of the application and eciency of desiccantcooling systems, studying their characteristics and performance and also investigating the potentiality of using them in dierent climates have engrossed a great deal of attention among researchers recently. Hatami et al.  presented a mathematical procedure to optimize the solar collector surface in solardesiccant wheel cycle. In their proposed cooling cycle, the thermal solar energy is used to provide the energy required for regeneration of air of desiccant wheel cycle. Tsujiguchi et al.  performed a feasibility study of simultaneous heating and dehumidication using an adsorbent desiccant wheel with humidity swing. Kabeel and Abdelgaied  investigated the eects of solar energy and Phase Change Material (PCM) on the energy saving of a desiccant air conditioner by means of a numerical approach. They proposed three congurations of a desiccant air conditioner and performed a comparative analysis between them in the same ambient conditions to understand which one of them is more ecient for energy-saving purposes. Das and Jain  investigated solar-assisted liquid desiccantcooling systems with indirect contact dehumidier experimentally. They assessed the overall performance in terms of its dehumidication eectiveness, moisture removal rate, cooling capacity, and thermal COP. Theoretical modeling and experimental study of the air thermal conditioning process of a heat pump-assistedsoliddesiccantcoolingsystem was presented by Nie et al. . Gadalla and Saghafar  proposed three novel two-stage desiccant air conditioning cooling systems and investigated them in hot and humidclimates. Kumar and Yadav  performed an experimental investigation of the solar-powered desiccantcoolingsystem by using composite desiccant \CaCl 2 /jute".
In designing the latent heat storage unit, selection of the PCM is an important factor which depends on the application. In the previous section, the absorption system was designed based on the cooling demand of the building. For the designed absorption systemhot water temperature in the range of 55 – 85 o C should be provided. Unfortunately, the thermo- physical properties of PCM’s in the melting temperature range of 80 -140 o C have not been studied sufficiently. Therefore, from the PCM ‘s which were given in Tables 1.7 and 1.6, in Chapter 1, Erythitol is selected as a latent heat storage material for which the thermo- physical properties are available in the literatures. Erythritol has a high heat of fusion and since the melting temperature is high the discharge time will be longer among the other PCM’s to apply for the absorption system.
Compared to traditional buildings, SCs are considered relatively cheap due to upcycling [2, 16]. Reference  has pointed out that the cost of converting an SC into a building is less than that of constructing a conventional building, but increasing the interior space and the quality of interior finishes could lead to the same cost as a traditional building . However, according to [7, 27], numerous exiting CBBs are far worse than their conventional counterparts, being less cost effective and not secure for habitation. If cost savings are achieved, the reduction may be only about 20% compared to conventional buildings, and this comes at the expense of human habitation considerations in terms of thermal and acoustic performance [7, 27]. The need for insulation materials, transportation, and installation may considerably elevate the cost of construction [4, 17]. Nevertheless, factors affecting a comparison between the cost of a conventional building and a CBB vary between (1) the availability of old stock containers; (2) new, old, and refurbished container prices; (3) traditional housing prices; (4) transportation and delivery prices, including crane systems; and (5) design space and vertical expansion, such as by staggering containers to increase space while reducing cost. As well, the vertical expansion of CBBs causes cost savings according to a comparison study conducted by 
The drawn graph is semi symmetrical around the center point (0, 0, 0) .The maximum temperature recorded along this axis is about 327 K (53.85 ºC) at the outlet of the left and right solar casing. On the other side, the minimum temperature was recorded is about 313.5 K in the solar panel’s close to the fan at inlet 2.It can be noticed that the temperature at the extreme ends of the solar casings start with a temperature of around 327 K and then decreases sharply till it reach near to 314 K at a horizontal distance of 80 cm from the center. Starting from this distance, the temperature raises quickly until it reaches close to the outlet point of solar panel. Between the two outlet points of the solar or inside the chamber, the temperature is fluctuating increase and decrease. This chat proves the same results explained in the temperature profiles in Fig. 8 and Fig. 9 that the temperature at the middle of the chamber is lower than at the four edges. On the other hand, the temperature profile follows different manner along the Y axis from that along the X axis as it can be seen in Fig. 16.
comparable FBC site-built homes. Produced in one- fifth the time and at half the cost of site-built homes, manufactured housing assembled in a controlled, factory environment uses fewer materials and generates 35%-40% less waste than comparable site- built units. Using comparable materials and installation methods as 2002 FBC compliant homes, 1994 HUD wind zone III units are as energy efficient and survivable as site built construction in 180kmh (100mph) wind zones. In spite of this, media exposure was found to have a significant impact on the public perception of manufactured housing safety, quality and value. 66% of survey respondents exposed to positive media bias considered manufactured housing to be safe, compared to 69% who considered manufactured housing to be unsafe following negative media exposure. However, research indicates that post-1994 manufactured housing is a safe, sustainable and affordable option in hothumidclimates prone to natural disasters and resource constraints.
The most important concluding remarks in this study are: Some desiccantcooling cycles have been analyzed and suggested a most efficient desiccantcooling cycle for selected climatic conditions. Direct and indirect evaporative cooling methods can be used for different cycles of desiccantcoolingsystem. Many studies emphasized on the optimization of operating parameters and used exergetic manufacturing cost (EMC) method for deciding the minimum regeneration temperature and R/P ratio. The effect of different operating parameters on the performance of desiccantcoolingsystem analysed and presented minimum running cost. Optimum wheel speed of about 17.5 rpm for high moisture removal and maximum COP. The R/P ratio, regeneration temperature, desiccant material, rotation of desiccant wheel, outdoor conditions etc. are the important parameters which affect the performance of desiccant wheel. The operating cost of the desiccantsystem in summer Italian conditions, interesting saving up to 35% are obtained and reduced thermal cooling power up to 52% and pay back period obtained about 5-7 years. Among the Ventilation, Recirculation and Dunkle cycle, the Dunkle cycle is better for wide range of outdoor conditions. Many studies evaluated the performance of different desiccant material and found the material which has the higher moisture adsorption capacity. Hybrid desiccantcoolingsystem economies 37.5 % electricity power when the process air temperature and relative humidity are maintained at 30 ºC, and 55% respectively. Solar energy may be suitable option for regeneration of desiccantcoolingsystem and it saves the regeneration power. Some studies stressed the energy saving potential by solarassisteddesiccantcoolingsystem. Mathematical modeling and simulation study of solarbaseddesiccantcoolingsystem performed by some researchers. A composite wheel can be absorbs more moisture than conventional desiccant wheel with same operating conditions. Compounding of desiccant wheel obtained the greater moisture adsorption rate. Some researchers applied the system in different fields and proved the feasibility of the DCS.
Plate type heat exchanger was analysed by Tae Hyun Kim  for a liquid desiccant. In this experiment 40% liquid solution LiCl with fluorescent substance is used for wettability test also internal cooling is adopted. The results shows that as mass flow rate of desiccant increases, liquid desiccant wettability increases and the regeneration rate increases. And For 1mm groove pitch, wettability of heat exchanger surface was highest. Regenerator with CaCl2 is as a liquid desiccant was examined by A.S. Alosaimy and Ahmed M. Hamed  by using solar water heater coupled. The experimental results demonstrated that solar water heater can be used to regenerate CaCl2 from 30% to 50%. And it shows good agreement between the experimental outputs and theoretical outputs. Structured packed regenerator studied by Esam Elsarrag. using triethylene glycol as a liquid desiccant. For a minimum carryover of triethylene glycol cellulose rigid media pad with packaging arrangement was used. The study indicates that with increase in air flow rate evaporation rate increased and humidity effectiveness decreased. With increase in desiccant concentration, evaporation rate decreases, because increase in desiccant concentration reduces driving force of mass transfer. In humid climate regeneration requires higher solution temperature as compared to dry climates. Absorber and regenerator of packed type studied by Nelson Fumo and D. Y. Goswami. using aqueous lithium chloride desiccant. With increase in air humidity ratio, water condensation rate increases. Dehumidifier gives lower condensation rate for higher desiccant temperature. If the temperature of air greatly higher than desiccant temperature it resulting in reduction of mass transfer due to the desiccant temperature increases. With the air flow rate and air
220.127.116.11 Direct evaporative coolers
Direct evaporative cooling (DEC) is the oldest and simplest type of evaporative cooling and involves bringing the process air into direct contact with water. One of the main evaporative cooling strategies often encountered is the fan-pad system . The fan-pad arrangement includes a fan/blower and an evaporation pad (example include: metal pads, cellulose pad, organic pad, inorganic pad (GLASdek, PVC pad, etc.) which provides the needed large surface area over which the air and water are contacted for effective evaporation. Often these coolers have the fan, the pad and ancillary systems all enclosed in a box (Fig. 7), such that the pad is kept moist by continuously dripping water unto the upper edges of the pad, the water gets distributed further by gravity and capillary action. The falling water is collected in a water basin underneath the pad and recirculated by a water pump . The drip-type coolers are the cheapest and simplest evaporative coolers but have some problems including pad clogging, pad scaling. Alternatives, requiring less maintenance (though at a higher cost) are Slinger-type, sprayed-pad and rotary-pad evaporative coolers .
The absolute work plane illuminance (direct sunlight + sky light) were calculated for the correspondent horizontal overhangs. The results were obtained for four days (21 March, 22 June, 24 September and 21 December), at four times within general office working hours (9:00, 12:00, 15:00 and 17:00 hours) and for four main cardinal orientations (East, West, North and South). The two correspondent reference points were; reference point 01 (Ref.Pt 01) at 3.04m (10ft) and reference point 02 (Ref.Pt 02) at 5.7m (19ft), positioned along the center of the 6.08m (20ft) deep office room at a work plane height of 0.8m (2’-9”). The evaluation of daylight quantity is based on the target absolute work plane illuminance at 500lux. Mean work plane illuminance values were plotted against overhang ratio to determine a general distribution profile of illuminance level received at respective reference points for the tested overhang depths (figure 2, 3, 4 & 5).
J.K. Nayak, J.A. Prajapati in their book have mentioned that design criteria for buildings should aim at resisting heat gain by providing shading, reducing exposed area, controlling and scheduling ventilation, and use of passive cooling techniques to achieve energy conservation goal . Pablo La Roche in his research paper mentioned that one can build passive coolingsystem with materials and components which are locally available as long as physics of the system don’t get affected . In India, Old Havelis and Mahals had built most appropriately to local climate in terms of material selection, construction techniques and spatial orientation of the building . According to Barozzi et al. (1992) there is greatest need of passive cooling strategies in developing countries due to limited financial resources and poor building technologies . Researchers throughout the world are working on various passive cooling technologies appropriate to their climates with help of various materials and experimentation methods. Sudaporn Chunglo et al (2006) in their experiment cell observed that spraying water on the roof together with solar chimney can reduce indoor temperature by 2.0–6.2 o C compared with ambient air .
The effect of inlet air cooling on the performance of a simple gas turbine plant is investigated. Systematic analysis of a GT cycle coupled to a coolingsystem is presented for an evaporative air cooling process. The performance improvement showed strong dependency on the climatic conditions, evaporative cooler effectiveness and to some degree on the gas turbine pressure ratio. The evaporative cooling is quite efficient for dry air, for 40°C and 10% RH ambient air, the maximum power gain and the thermal efficiency improvements are 9.102% and 0.39% respectively. The direct evaporative cooling process is limited by the wet bulb temperature at which additional water spray would not contribute any further cooling effects. The performance of the evaporative cooling is presented in a general dimensionless working graph that directly relates the maximum power gain and thermal efficiency variation to the ambient conditions. Finally, the performance of the air coolingsystem was examined for the hot and humid conditions of Jeddah Saudi Arabia. The actual climate on
Traditional HVAC and desiccantcooling air conditioning progresses diagrams are shown in Figure 1-1 and their thermal processes on the psychrometric chart are shown in Figure 1-2. In this two air conditioning system, the fresh air only take the latent heat load in the serving room. For the conventional refrigerant vapour compression system, the fresh air at point 1 has heat/mass exchanger to point 2, from here it is cooled until below its dew point to point 3, in this progress the superfluous moisture is condensed out, and then excess energy is required to reheat it to supply point 4, which mixes with the indoor air to point 5. In this process, overcooling and reheating energy is wasted and more by-product of CO2 is released. For the proposed effective heat recovery/desiccantcoolingsystem, fresh air from point 1’ releases heat/mass effectively to the releasing air until point 2’, from here it is further cooled and dehumidified by the cold desiccant to supply point 3’. The treated fresh air deals with the indoor cooling and dehumidification load to point 5’, where some air exits out and carries the redundant heat/mass from the entering fresh air until reaching point 6’. This is the novel air treatment circle using less energy to achieve the same air conditioning target. Additionally the special desiccant soaked fibre heat/mass exchanger is utilized in the desiccantcoolingsystem for high recovery effectiveness.
Strategic planting of trees, shrubs and vines about a building and on structures such as pergolas and beam overhangs can, along with urban form, help to modify the microclimate. When correctly applied, the need for internal and external shading devices can be greatly reduced. Selective planting can shade not only windows and other apertures but also whole facades and roofs, reducing conductive as well as radioactive heat gains. Also stated that by using deciduous trees and vines shading is provided only when needed. Through the use of evergreens, shading can be provided year-round. Vegetation can also be used to reduce ground reflection and, through evapotranspiration, the ambient air temperature. Evergreen shrubs and ground cover are useful for preventing or reducing reflection from roads, paved areas and buildings. Evergreens are also effectively used as wind barriers. Deciduous species are particularly suitable for temperate climates. The shading effect of vegetation depends heavily on the plant type (trees, shrubs or vines), species, and age. These factors define the leaf type and the density of the vegetation. In the case of deciduous plants, the density changes from season to season.
From Table 2-3, the general trend in using the CTES in solarcooling systems is that the chiller provides the chilled water to the building through the cold tank; Figure 2-11 illustrates a solar absorption system that uses a cold tank. The cold tank is continuously charging throughout the period of operation of the chiller and is not used when the chiller turns off (when the solar energy is not available to activate the chiller), where none of these studies have mentioned the mechanism of discharging the stored energy from the cold tank, especially at night, when the cold effects are still needed in residential buildings as in the Middle East. In other words, the chiller, beside its main job of providing the cold effects in the building, is used to maintain the temperature of the chilled water in the CTES as cold as possible (as if the cold tank has become an extra cooling load that has to be provided by the chiller). Hang & Qu (2010) found insignificant effects of increasing the size of the cold tank from 4m 3 to 20m 3 on the system performance. More recently, Abdullah (2016) has discovered that there is “no advantage” from changing the size of the cold tank in a solarcoolingsystem. As mentioned before, more energy may actually be consumed in the cooling systems with CTES compared to the non-storage cooling systems. Therefore, efficient control strategies for the cold tank are essential (as they are in conventional cooling systems) to make it capable of enhancing the performance of solarcooling systems rather than being a burden on the system.
Published: 8 November 2018
Abstract: Desiccant enhanced evaporative coolingsystem is a sustainable air-conditioning (A/C) system which deals the latent load and sensible load separately by a dehumidifier and an evaporative cooler. A LDD-RIEC system consists of a liquid desiccant dehumidifier (LDD) and a regenerative indirect evaporative cooler (RIEC) were investigated. The LDD-RIEC system is characterized by low energy consumption compared with conventional mechanical coolingsystem, but the main shortcoming is the high dependency on ambient air conditions. To maintain stable indoor temperature, a control scheme is essential. However, very limited research work regarding control strategy can be found in open literatures. In this paper, a novel controller named high-low (H-L) control is proposed. Multi-speed technology is utilized for primary air fan and secondary air fan operating either at high speed or at low speed. The annual performance of a LDD-RIEC system is simulated in Hong Kong, a typical hot and humid region. The results indicate that H-L control is effective in maintaining stable indoor thermal comfort with temperature fluctuation from 24 °C to 27 °C for 99% of time.
Straw-bales have a monolithic layer of straw that is usually covered with plaster on the inside and stucco on the outside unless straw is placed between posts and beams where sheathing is then applied. When designed and detailed properly, a monolithic bale wall will result in little air leakage. This is due to the cellulose form in the straw that has high-quality insulating qualities that makes the straw- bale wall thermally resistant. Based on ASTM Testing by the Department of Energy (1995), R-values for these bales come between R-2.4 and R-3.0 per inch. Between the bottom of the bale wall and the foundation, an adequate waterproof barrier is necessary to stop any unwanted moisture. Moisture control can be a concern and must be accounted for. To help stop water from leaking through at the foundations, the building should have a layer of pea gravel between wood plates along the inside and outside faces (Goodhew et al. 2004). Dry rot fungus in a straw-bale wall system will cause significant damage when they sustain high levels of moisture, usually with humidity of 70- 80 % or having 20 % of dry weight as compared to moisture that comes and goes at different intervals. From experience and tests, the best way to control the moisture content, is to make sure the bales can transpire the moisture back into the atmosphere. An air barrier such as building paper applied on the exterior wall sheathing can help transpire the moisture content outside and create a surface where the moisture can be inhibited. However, this solution may not be applicable to straw bale (e.g. the plaster sheathed type); rather breathable sealers are usually the best because they do not allow the moisture to get in through the stucco and permits to transpire moisture out. A mistake that the building permit reviewers commonly make is on requiring barriers such as plastic or tar-impregnated paper cover the bales. This will not allow the straw bales to breathe, i.e. to release water vapor. Instead, it will be trapped against the straw-plaster interface, damaging it because the structure system depends on a thorough attachment of plaster and straw (King 2006).
The environmental regulatory bodies have come up with more specific guidelines so that the projects will not lead to an overall excessive increase in outdoor temperatures (Tso, 1996). However, most of current policies, strategies, and regulations are barriers to “green” design and green management practices so they should be removed or updated to encourage creativity and the implementation of sustainable practices (Hostetler et al. 2011). In this case, graphics are used to present practical information to show the outcome and so increase the chance of fostering mutual understanding among communities and planners (Kleerekoper et al. 2011).
An architect does not need to know the graph and tables showing the analysis but use the guidelines and strategies instead to get an optimized form from the research. Such strategies and elements that could improve by optimizing building form such as width and length geometrical manipulation, orientation, shading devices, window to wall ratio, width to length ratio, surface to volume ratio, and insulation material. These ideas can be easily applied in the early design process to achieve better building performance. Actually, a building life cycle cost and electricity bills can be cut down to a few percent as certain building forms or shapes contribute in reducing cooling load. Building forms, spatial layouts, and arrangement configurations that are planned towards energy efficiency and based on climatic data are considered as passive response. Improvisation of energy used is not only on building orientation but influenced by the form of the building and the ratio of volume to surface (Yeang, 2006). Basically, the size and orientation of exterior envelope are exposed directly to outdoor environment. These elements are determined specifically by the building form which in turn affects the thermal performance of a building. The building form also influences the cost and aesthetics. Undeniably, the selection of optimum form, orientation, and envelope configuration can reduced energy consumption by 40% (Mohammed Hussein Abed, 2012; Wang et al., 2006).