Increased consciousness of the environmental problems has aroused people’s interest of renewable energy systems, especially the application of green features in buildings. The demand for air conditioning / cooling in domestic and non-domestic buildings is rising throughout the world; this increases the reliance on conventional fuels and the global warming effect from greenhouse gas emissions. Passive cooling and energy efficient design can substantially reduce reliance on fuel based heating and cooling. Passive and Hybrid Downdraught Cooling, in different forms, is now technically viable in many parts of the world. This has been established through a combination of research projects. In some hot arid regions, a major part of the energy consumed consists of air-conditioning requirements. Alternative methods, using passive cooling techniques, can assist in reducing the conventional energy consumption in buildings. Evaporative cooling, which can be tracked back several hundreds of years in ancient Egypt and Persia [1–3], is one of the most effective strategies, because of the enormous latent heat needed for evaporation of water. Green features are architectural features used to mitigate migration of various air-borne pollutants and transmission of air from outside to indoor environment in an advantageous way [9]. The reduction of fossil fuel consumption and the associated decrease in greenhouse gas emissions are vital to combat global warming and this can be accomplished, in part, by the use of natural ventilation. To assess the performance of several innovative cooling systems devices and to develop improved models for more established technology, quantitative measurement of output was necessary. This was achieved in this study by the development of simply constructed low energy cooling systems which were calibrated by the innovative use of wind and water as a source. These devices were found to be consistent and accurate in measuring the temperature and cooling load from a number of devices. There were some problems in the original evaporative units. Therefore, a number of modifications have to be made to enhance the systems performance. The novel Windcatcher – PEC cooling system was assessed and different cooling loads were achieved.

The work presented in this thesis will explore the development of novel heat recovery systems coupled with low carbon technologies, and its integration to become one device with multifunction (building integrated heat recovery/cooling/air dehumidifier. In the first part of this thesis, an experimental performance of an individual heat recovery unit using Micro Heat and Mass Cycle Core (MHM3C) made of fibre papers with cross flow arrangement has been carried out. The unit was tested in an environmental control chamber to investigate the effects of various parameters on the performance of heat/energy recovery unit. The results showed that as the airflow rate and temperature change increase, the efficiency decreases whilst recovered energy increases. Integrating heat recovery system in energy-efficient system represents significant progress for building applications. As part of the research, the integration of heat recovery using a cross-flow fixed-plate with wind-catcher and cellulose fibre papers of evaporative cooling units have allowed part of the energy to be recovered with the efficiency of heat recovery unit ranged from 50 to 70%, cooling efficiency ranged from 31 to 54%. In another case, the integration of heat recovery system with building part so called building integrated heat recovery (BIHR) was explored using polycarbonate plate with counter-flow arrangement. It introduces a new approach to MVHR system, an established technology that uses a modified insulation panel, linking the inside and outside of a building, to recover heat while extracting waste air and supplying fresh air. In this configuration it is not only acts a heat recovery, but also as a contribution to building thermal insulation. From the experiments conducted, it was found that through an energy balance on the structure, the efficiency of BIHR prototype was found to be 50 to 61.1 % depending on the airflow rate. This efficiency increases to the highest value of 83.3% in a full-scale measurement on a real building in Ashford, Kent as the area of heat transfer surface increases. The increasing of heat surface area again proved a better performance in terms of efficiency as the results on another full scale measurement on a real house in Hastings, Sussex showed to be 86.2 to 91.7%. With the aiming to have a high performance system, a new improvement design of BIHR' corrugated polycarbonate channels with four airstreams has significant advantages over the previous prototype BIHR with two airstreams. The recovered heat is increased by more than 50%. With the issue of thermal comfort in hot region area and problems with conventional air conditioning system, a study of BIHR system with fibre wick structure for different hot (summer) air conditions using different working fluids was carried out. For the first case, water was used to give a direct evaporative cooling effect which is suitable to evaluate the system performance under hot and dry climatic conditions and the second case, potassium formate (HCOOK) solution was used as liquid desiccant for dehumidification under hot and humid climate conditions. By supplying the water over the fibre wick structure, with a constant airflow rate of 0.0157m3/s, the efficiency increased with increasing intake air temperature. The efficiency ranged from 20 to 42.4% corresponding to the minimum and maximum of intake air temperature of 25°C and 38.2°C, respectively. With the variation of airflow rate, the efficiency of the system was found to be 53.2 to 60%. In second case, the HCOOK solution with concentration of 68.6% has been selected as the desiccant and for a defined airflow rate of 0.0157m3/s, heat recovery efficiency of about 54%, a lower desiccant temperature of 20°C, with higher intake air temperature and relative humidity produces a better dehumidification performance with a good moisture absorption capacity. Therefore, this system is expected to be used efficiently in hot and humid regions. The research is novel in the following ways: • The development of multifunction device in one system; building integrated, heat recovery, cooling, desiccant dehumidification. • The design and development of BIHR is an advanced technology of building thermal insulation and heat recovery. The novel BIHR -fibre wick cooling/dehumidification system has the potential to compete with conventional air conditioning systems under conditions involving high temperature and high moisture load.

The aim of this thesis is to study the energy performance of a building integrated heating and cooling system. The research objectives are to investigate the system operating characters, to develop mathematical models for the heating and cooling systems, to demonstrate the technologies experimentally, to identify the best designs for a combined system and to investigate the cost effectiveness of the system. The main components of the systems are the aluminium plate façade and the building wall behind it, these form a plenum between them and the air is then heated or cooled as it flows through this plenum. Mathematical models were developed based on the energy balance equations and solved by matrix inversion method. These models were then validated with experimental results. The experiments were carried out in the laboratory with a facade area of 2m2. Two designs of facade were tested, i.e. flat and transpired plates. Results showed that the transpired design gave better thermal performance; the system efficiency for the flat plate was only about 30%, whereas it was about 85% for the transpired plate. On the other hand, a cooling system with double plenums was found to be better than a single plenum. Thus, a transpired plate with two plenums was identified as the best design for space heating and cooling. The cooling efficiency was nearly 2.0 even at low solar radiation intensity. A simulation study was carried out by assuming a 40m2 of façade was installed on an office building in London. The yearly energy saving was estimated as 10,877kWh, which is equivalent to 5,874kgCO2/year of emission avoidance. The system is calculated to cost about £70/m2, and for a discount rate of 5% and 30 years of lifetime, the payback period for this system would be less than a years.

The global air temperature has increased by 0.74± 0.18 °C since 1905 and scientists have shown that CO2 accounts for 55 percentages of the greenhouse gases. Global atmospheric CO2 has been sharply increased since 1751, however the trend has slowed down in last fifty years in the Western Europe. UK and EU countries have singed the Kyoto agreement to reduce their greenhouse gas emissions by a collective average of 12.5% below their 1990 levels by 2020. In the EU, 40% of CO2 emission comes from the residential energy consumption, in which the HVAC system accounts for 50%, lighting accounts for 15% and appliances 10%. Hence, reducing the fossil-fuel consumption in residential energy by utilizing renewable energy is an effective method to achieve the Kyoto target. However, in the UK renewable energy only accounts for 2% of the total energy consumption in 2005. A novel heat recovery/desiccant cooling system is driven by the solar collector and cooling tower to achieve low energy cooling with low CO2 emission. This system is novel in the following ways: • Uses cheap fibre materials as the air-to-air heat exchanger, dehumidifier and regenerator core • Heat/mass fibre exchanger saves both sensible and latent heat from the exhaust air • The dehumidifier core with hexagonal surface could be integrated with windcowls/catchers draught • Utilises low electrical energy and therefore low CO2 is released to the environment The cooling system consists of three main parts: heat/mass transfer exchanger, desiccant dehumidifier and regenerator. The fibre exchanger, dehumidifier and regenerator cores are the key parts of the technology. Owing to its proper pore size and porosity, fibre is selected out as the exchanger membrane to execute the heat/mass transfer process. Although the fibre is soft and difficult to keep the shape for long term running, its low price makes its frequent replacement feasible, which can counteract its disadvantages. A counter-flow air-to-air heat /mass exchanger was investigated and simulation and experimental results indicated that the fibre membranes soaked by desiccant solution showed the best heat and mass recovery effectiveness at about 89.59% and 78.09%, respectively. LiCl solution was selected as the working fluid in the dehumidifier and regenerator due to its advisable absorption capacity and low regeneration temperature. Numerical simulations and experimental testing were carried out to work out the optimal dehumidifier/regenerator structure, size and running conditions. Furthermore, the simulation results proved that the cooling tower was capable to service the required low temperature cooling water and the solar collector had the ability to offer the heating energy no lower than the regeneration temperature 60℃. The coefficient-of-performance of this novel heat recovery/desiccant cooling system is proved to be as high as 13.0, with a cooling capacity of 5.6kW when the system is powered by renewable energy. This case is under the pre-set conditions that the environment air temperature is 36℃ and relative humidity is 50% (cities such as Hong Kong, Taiwan, Spain and Thailand, etc). Hence, this system is very useful for a hot/humid climate with plenty of solar energy. The theoretical modelling consisted of four numerical models is proved by experiments to predict the performance of the system within acceptable errors. Economic analysis based on a case (200m2 working office in London) indicated that the novel heat recovery/desiccant cooling system could save 5134kWh energy as well as prevent 3123kg CO2 emission per year compared to the traditional HVAC system. Due to the flexible nature of the fibre, the capital and maintenance cost of the novel cooling system is higher than the traditional HVAC system, but its running cost are much lower than the latter. Hence, the novel heat recovery/desiccant cooling system is cost effective and environment friendly technology.

In the UK, there are about 26 million houses and the government’s future plan is to build 3 million more by 2020 (BBC, 2008, Jason, 2011). As the demand for housing increases, especially for single occupant homes, the rate of energy consumption and, in effect, the proportion of CO2 emissions is on the rise. Successful sustainable energy strategies for domestic buildings can thus be an effective tool for mitigating these effects and achieving healthy building conditions. The main aim of the research are obtaining comfortable building spaces by reducing any overheating and reduce energy demand by using passive method which also will reduce the emission of CO2. Also this work aims to raise attention on the influence of the domestic sector on the amount of CO2 emissions by using low thermal mass construction. Thus, the research’s objectives are divided into firstly, investigate the opportunity of improving the Micronal Phase Change Material (MPCM) thermal conductivity and secondly, studying the influence of using enhanced MPCM for reducing overheating in lightweight building construction. This research investigates means of improving the thermal performance of the UKs existing and new domestic buildings stock. In order to increase thermal resistance and hence reduce heat losses, a new panel comprised of outer coating and thin layer or aerogel to increase thermal resistance was developed which could be added to the exterior walls of existing houses. This research results have shown from the experimental work when MPCM coupled with construction materials that the percentage of MPCM should not be above 50% otherwise it will reduce the potential benefit of the mixture to enhance thermal conductivity of MPCM. The best thermal conductivity was obtained by mixing 20% PCM, 75% Gypsum and 5% Silica with honeycomb, which gave a value of 0.306 W/mK. On the other hand, the best thermal conductivity was obtained using the clay by mixing 40% MPCM, 20% Clay and 40% cement, which gave a value of 0.253 W/mK. The simulation results shown that natural night ventilation could help reduce the overheating period to about 50% with the use of MPCM. Finally, The results of the new external wall panel that has been developed to improve the thermal performance have shown that through application of these panels a substantial reduction between 3 ºC to 5 ºC in the internal temperature.

Ventilation stacks are becoming increasingly common in the design of naturally ventilated buildings. The overall aim of the work described is ultimately to improve design procedures for such buildings. This thesis presents the experimental and theoretical investigation of unsteady wind effects on natural ventilation of a single envelope with multiple openings for both wind alone, and wind and buoyancy combined cases. There are two types of openings: namely the sharp-edged orifice and the long opening (stacks being treated as long openings). Two methods are adopted: 1) direct wind tunnel measurements using the hot-wire technique; 2) theoretical analysis using steady and unsteady envelope flow models. For the wind alone experiments, the influences of wind speed, wind direction and opening configuration on flow patterns are studied. For the wind and buoyancy combined tests, the transitional process between wind dominated and buoyancy dominated states are investigated. The direct velocity measurements provide the criteria for testing the validity of the theoretical models, and ways to improve them. Additionally, improvements are made to the experimental techniques: e.g. a precise unsteady calibration method of the hot-wire is developed; improvements of pressure measurements are also investigated. The experimental technique works well with multiple stacks. Even though small openings are used, some dependence of the mean pressure coefficient on opening configuration is observed. The theoretical models also work reasonably well with multiple stacks, yet it is observed that the accuracy of the theoretical models decrease with the increasing number of openings, and is sensitive to the chosen discharge coefficient which defines the characteristics of ventilation openings.

Within a closed environment, (e.g. building, car, aircraft) that is thermally and hygrically isolated from the exterior climate, one approach that can help reduce the energy required for indoor mechanical climate control whilst increasing comfort levels for occupants is to use hygrothermal coatings on top of existing materials. Hygrothermal coatings can re-introduce both thermal and hygric buffering within the isolated envelope. Understanding of the behaviour of these coatings allows them to be optimized for different environments. The overall aim of the research is to design the functional properties of inorganic, nano structured surface coatings i.e. mesoporous silica (MS) to produce desired hygrothermal behavioural responses to climatic variables in a controlled environment. This can be achieved through correlation of the hygrothermal properties of desiccant materials with their microstructural characteristics and understanding the hygrothermal behaviour of the materials under representative psychrometric conditions. Stage 1 was to characterise the hygrothermal properties of the MS and other conventional desiccant materials i.e. Silica Gel, Molecular Sieve, Clinoptilolite and Bentonite to produce a ‘Template of functional properties’ and provide material input data for the numerical models. These tests included dynamic vapour sorption (DVS) techniques for moisture absorption including cyclic adsorption/desorption and sorption isotherms, wet-cup tests for vapour permeability, partial immersion tests for liquid water absorption, modified transient plane source (MTPS) tests for thermal conductivity and differential scanning calorimetry (DSC) for heat capacity. Stage 2 utilised techniques to classify the pore geometry of the desiccants, including helium pycnometry for solid density, gravimetric testing for bulk density, N2 physisorption for specific surface area, mesopore volume and mean pore diameter with small angle X-ray scattering and transmission electron microscopy used to corroborate the N2 results. Scanning electron microscopy (SEM) was used to confirm material composition and purity and to indicate macropore distribution. A correlation between the hygrothermal properties from Stage 1 with their microstructural characteristics was then sought. Stage 3 was a parametric analysis of the candidate materials hygrothermal behaviour using the validated 1D numerical simulation software WUFI Pro v5.1. Further analysis was carried out to assess how the numerical model could be used to tune the functional properties of the MS materials to suit differing psychrometric conditions in closed environments. A series of simulations using a representative climate (Nottingham) were also run to compare the hygrothermal behaviour of the MS materials to the conventional desiccants A series of energetic 3D physical and numerical models (WUFI Plus v 2.1) were designed to study the resultant relative humidity levels in both occupied and unoccupied spaces and under different air exchange rates due to the presence of the hygrothermal materials in a closed environment. The 3D model was also used to compare the operational energy usage of different retrofitting cases under the same representative climate used in Stage 3 with three different heating, cooling humidification and dehumidification (HCHD) control scenarios. The MS materials displayed significantly higher Moisture Buffer Values (MBV), equilibrium moisture contents (EMC) and faster response rates when compared to the conventional desiccants. It was shown that WUFI Pro can be used as a design tool for material functional properties, with the sorption isotherm, and in particular adjustment of the w50 – w80 gradient of the absorption branch isotherm being by far the most sensitive parameter. In the MS samples, the dynamic vapour sorption (DVS) response time has a significant and positive logarithmic relationship with both the mesopore diameter and the mesopore volume implying that mesopore geometry can be tuned in order to give the desired dynamic vapour sorption/ desorption response rate and storage capacity to suit a given set of interior psychrometric conditions. It is therefore possible to tune an MS material to suit a particular set of psychrometric conditions using WUFI Pro. The MS materials displayed outstanding passive buffering performance across a range of exterior climate conditions combined with numerous internal moisture and ventilation overloading scenarios, providing constant humidity buffering within the American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE) comfort limits. When compared against a retro-fitted gypsum-lined indoor environment there was a potential reduction in humidification/ dehumidification energy demand of up to 100% when using an MS material coating.

The European standard EN15450 states that the Coefficient of Performance (COP) target range for a Ground Source Heat Pump (GSHP) installation should lie within the range of 3.5 to 4.5; when used for heating a building, and a typical Air-Source Heat Pump (ASHP) has a COP of 2.0 to 3.0 at the beginning of the heating season and then decrease gradually as the ambient air becomes cooler, whereas a typical GSHP is in the range of 3.5 –4.0, also at the beginning of the heating season and then decrease gradually as heat is drawn from the ground. For these reasons, in the middle of winter, when the COP drop, the heat pumps can generally only be considered as a ‘pre-heating’ method for producing higher temperature heat such as domestic hot water. In addition soil presents certain difficulties, due to the high cost of drilling to position coils in the ground compare to air source, although frost formation on the evaporator in winter limits also limit the use of air source. Though technology advances or are needed to overcome those issues. The aims of this project, therefore, were firstly to reduce the drilling length of the ground heat exchanger of the ground source heat pumps and to maintain high COPs of the air and ground source heat pumps from beginning to the end of the heating season; and secondly to develop a viable alternative evaporator for air source heat pumps to reduce frost formation during winter. These were achieved; the first aim through the combination of ground loops with solar-air panels or solar roof/collectors roof to ground heat exchangers loops to reduce the length of the boreholes, and to reduce the freezing effects around the boreholes, hence increase or maintain a constant temperature during heating season. The second aim was also achieved through development and validation of novel air source heat pump evaporator, using Direct Expansion (DX) black flat plate absorber or/and vacuum tubes for frost reduction. In this thesis, in order to achieve the above aims; four aspects of investigations have been independently investigated as following: 1- Preliminary investigation on Direct Expansion (DX) Solar Source Heat Pump system. 2- Investigation on the performance of the DX- PV/heat pipe heat pump system to reduce frost and enhance the COP of the air source heat pumps, 3- A small scale testing on the heat injection on energy piles for residential buildings for earth charging by means of solar roof/collectors 4- A field trial testing of the performance of the combination of solar-air thermal collectors with conventional GSHP with shorter ground heat exchangers (48m deep) to charge the ground and reduce freezing effects around the piles after heating cycle. From the simulation results, the novel PV/hp-HP system has a COP ranging from 4.65 to 6.16 with an average of 5.35. The condenser capacity ranging from 33 to 174 W would provide the heat source for space heating and domestic hot water. The energy performance of the novel PV/hp-heat pump was not as good as expected due to the low solar radiation. It should be much better in some low latitude locations with better solar radiation. The results of this thesis have shown that the length of ground source boreholes could be considerably reduce by about 60% compare to conventional boreholes using a combination of solar-air collectors with the GSHP and the average COP of 3.7 was achieved.

This study aims to improve the performance of existing indirect evaporative coolers. A new dew point indirect evaporative cooler with counter-current heat/mass exchanger was developed in this research by optimal design, material selection, numerical simulation, experimental investigations and economic, environmental, regional acceptance analysis. A new dew point heat/mass exchanger using a counter-current flow pattern was designed by numerical simulation in terms of material, structure, geometrical sizes and operating conditions. The numerical results indicate that under a typical cooling design condition, i.e., 35oC dry-bulb/24oC wet-bulb temperatures, the heat exchanger could achieve a wet-bulb effectiveness of approximately 1.4. The results of numerical simulation are consistent with some published test data. Based on the numeric results and the material selection determined from a set of related tests, a prototype dew point heat/mass exchanger and the associated air cooler was designed and constructed in laboratory. Testing was carried out to evaluate the performance of the experiment prototype. The results indicate that the wet-bulb effectiveness of the prototype ranged from 55% to 110% for all test conditions. The power consumption of the prototype ranged from 10 to 50 W with energy efficiency (or COP) rated from 3 to 12. It is also found that the water consumption of the prototype was very small which ranged from 0.2-1.3 litre/h. A comparison between the numerical and experimental results was carried out and the reasons for the discrepancy were analysed. This research also investigates the feasibility, economic and environmental potential of using a dew point cooler in buildings in Europe and China. From the related studies in this thesis, it is concluded that the dew point cooler can achieve a higher performance (in terms of effectiveness and energy efficiency) than the typical indirect evaporative coolers without adding too much cost. It is found that the effectiveness and energy efficiency of the heat/mass exchanger in the cooler are largely dependent upon channel geometries, the intake air velocity, temperature, humidity and the working-to-intake air ratio but less on the feed water temperature. To maximise effectiveness and energy efficiency, it is suggested that 1) the channel height and the length of exchanger should be set below 6 mm and 1-1.2 m respectively; 2) the intake channel air velocity should be controlled to 0.5-1 m/s; and 3) the working-to-intake air ratio should be adjusted to 0.4-0.5. It is also concluded that the dew point system is suitable for most regions with dry, mild and hot climate. It is, however, unsuitable for humid regions where the system is used as a stand-alone unit. Compared to the conventional mechanical compression cooling system, the dew point system has a significantly higher potential in saving energy bills and reducing carbon emission. A project to construct an 8 kW commercial dew point cooler is currently under development with the assistance of a Chinese company. By the optimisation of material, structure and geometries, the cooler is expected to achieve a cooling output of 8 kW at the inlet air of 38oC dry-bulb/ 21oC wet-bulb temperatures, with a wet-bulb effectiveness of 1.02 at 1530 m3/h of supply air flow and 1200 m3/h of discharge air flow, whereas the power input of the unit is about 450 W and the energy efficiency (or COP) at 18.5.

The wide uses of solar energy technology (solar thermal collector, photovoltaic and heat pump systems) have been known for centuries. These technologies are intended to supply domestic hot water and electricity. However, these technologies still face some barriers along with fast development. In this regards, the hybrid energy system combines two or more alternative technologies to help to increase the total efficiency of the system. Solar assisted heat pump systems (SAHP) and photovoltaic/thermal collector heat pump systems (PV/T-HP) are hybrid systems that convert solar radiation to thermal energy and electricity, respectively. Furthermore, they absorb heat first, and then release heat in the condenser for domestic heating and cooling. The research initially investigates the thermal performance of novel solar collector panels. The experimental results indicate an average daily efficiency ranging from 0.75 to 0.96 with an average of 0.83. Compared with other types of solar collectors, the average daily efficiency of novel solar thermal collectors is the highest. The research work further focuses on the integrated system which combines solar collector and air source heat pump (ASHP). The individual components, configurations and layout of the system are illustrated. Theoretical analysis is conducted to investigate thermodynamic cycle and heat transfer contained in the hybrid system. Laboratory tests are used to gauge the thermal performance of the novel SAHP. A comparison is made between the modelling and testing results, and the reasons for error formation are analysed. The research then considers the specially designed PV/T collector that employs the refrigerant R134a for cooling of PV modules and utilizes the glass vacuum tubes for reducing the heat loss to the ambient air. The PV/T collector consists of 6 glass vacuum tube-PV module-aluminium sheet-copper tube (GPAC) sandwiches which are connected in series. The theoretical analysis and experimental tests all give the satisfactory results of up to 2.9% improvement of electrical efficiency compared with those without cooling. The research finally focuses on the integrated heat pump system where the PV/T collector acts as evaporator. Based on the energy balance of the four main components of the heat pump system, a mathematical model of the heat pump system is presented. When the instantaneous ambient temperature and solar radiation are provided, results are obtained for the spatial distributions of refrigerant conditions, which include temperature, pressure, vapour quality and enthalpy. Detailed experimental studies are carried out in a laboratory. Three testing modes are proposed to investigate the effect of solar radiation, condenser water flow rate and condenser water supply temperature on energy performance. The testing results show that an average coefficient of performance (COP) reached 3.8,4.3 and 4.0 under the three testing modes with variable radiation, condenser water supply water temperature and water flow rate, respectively. However, this could be much higher for a large capacity heat pump system using large PV panels on building roofs. The COP increases with the increasing solar radiation, but decreases as the condenser water supply temperature and water flow rate increases.