Thermal performance of dwellings in Cyprus and approaches for energy conservation

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel UniversityEnergy has always been the dominant driving force for the socio-economic development of mankind. Nowadays, the global energy system is highly depended on fossil fuels. A great share of the final energy consumption, over 40%, in the EU-27 is consumed by the existing building stock whereas dwellings account for 66.62% of this. Thus, the need to increase the energy performance of dwellings is an important instrument in the efforts to lessen Europe’s energy dependency. In order to define measures to increase the energy performance of dwellings a deeper understanding of their characteristics should be gained. Unfortunately, in Cyprus there is a gap in knowledge on this aspect. In this thesis the characteristics of the dwellings in Cyprus are defined through a sample of 500 dwellings. The results revealed that more than 80% of dwellings in Cyprus do not have thermal insulation installed on their envelope. From this it is clear that the definition of the optimum thermal insulation material to be applied in dwellings is very important. Thus, the commercially available thermal insulation materials and topologies used in Cyprus were reviewed and defined through a market survey and the typical dwelling was modelled. The effect of the application of thermal insulation to its energy behaviour was simulated using TRNSYS. This resulted in the definition of the optimum thermal insulation materials and topologies to be applied in both new and existing dwellings. Accordingly, the application of advanced commercially available materials such as Phase Change Materials (PCM) to the envelope of the typical dwelling was investigated. The energy savings achieved by the addition of a PCM layer on the envelope of the typical dwelling was found to be 28.6%. The optimum PCM case was also combined with the optimum thermal insulation combination and an energy saving of 68% was predicted. The incorporation of Renewable Energy Sources (RES) to the typical dwelling was also simulated and studied. Specifically, two types of standalone RES systems were initially evaluated; a solely photovoltaic (PV) system and a hybrid PV-Wind system. The results showed that the solely PV system is a much better option due to the very high solar potential of Cyprus in comparison to the poor wind profile of the island. Subsequently, a grid-connected PV system was also evaluated and the results showed that when a RES system is grid-connected the cost of the system is reduced to half of that of the standalone cases. This research has revealed that the optimum topology combinations to be applied in both new and existing dwellings in Cyprus is thermal insulation plaster or thermal insulation bricks (only for new dwellings) on the external walls combined with expanded polystyrene on the roof. These results will provide valuable information that will assist both engineers and architects in the efficient design of dwellings in Cyprus. The investigation of the application of macroencapsulated PCM showed that these materials are not yet an economically viable solution for application in Cyprus The findings also show that a solely PV system is the optimum RES system to be applied in Cyprus especially when it is grid-connected. The findings of this project are useful for individuals, house builders and designers as well as policy makers for the design of energy saving subsidy schemes.Research Promotion Foundation (RPF) of Cypru

Experimental investigation of the thermosiphonic phenomenon in domestic solar water heaters

The deeper understanding of the ‘thermosiphonic phenomenon’ and the identification of the key parameters affecting it, is the main aim of a research project currently in process in Cyprus. In this work a review of the existing standards and scientific knowledge concerning domestic solar water heaters is presented. The first preliminary results of the experimental investigation of the ‘thermosiphonic phenomenon’ in domestic solar water heaters are also presented. For this purpose a special test rig was set up and equipped with all sensors necessary to measure all parameters that are most likely to affect the ‘thermosiphonic phenomenon’. All tests were conducted according to ISO 9459- 2:1995(E). At first, the solar collector was tested according to EN12975-2:2006 in order to determine the thermal performance characteristics at a flow and operation conditions specified by the standard. Consequently, the efficiency of the collector operating thermosiphonically was calculated based on quasi-dynamic approach. Finally, a series of correlations were attempted using the data acquired when the collector is operating themosiphonically which are the following: (i) the temperature difference of the water at the outlet and the inlet of the collector (ΔΤ) with the solar global radiation, (ii) the water mass flow with the solar global radiation, (iii) the water mass flow with the temperature difference of the water at the outlet and the inlet of the collector (ΔΤ). The results of the data analysis showed that these parameters are very well correlated between them since the coefficient of determination (R2) is over 0.91 in all cases

Investigation of the parameters affecting the thermosiphonic phenomenon in solar water heaters

Cyprus is currently the leading country in the world with respect to the application of solar water heaters for domestic applications, with more than 93% of the houses equipped with such a system. The great majority of these solar water heaters are of the thermosiphonic type. Thermosiphonic is a natural phenomenon where the flow of the solar heated water from the collector to the storage tank occurs from a small flow created due to the difference in density between hot and cold water. The main advantage of such systems is that they do not require a pump for circulating the water and circulation exists as long as there is sunshine. This reduces the maintenance requirements and the system is foolproof. In spite of the fact that extensive analyses of the performance of solar water heaters has been carried out by numerous researchers, almost all of them concerned forced circulation systems which use a circulating pump. Currently, the knowledge on the parameters affecting the ‘thermosiphonic phenomenon’ is rather poor while on an international level (ISO and CEN committees) there isn’t any standard to test thermosiphon solar collectors. The deeper understanding of the ‘thermosiphonic phenomenon’ and the identification of the key parameters affecting it, is the main aim of a research project currently in process in Cyprus. In this work the first preliminary results of the experimental procedure are presented. More specifically, a special test rig was set up and equipped with all sensors necessary to measure all parameters that are most likely to affect the ‘thermosiphonic phenomenon’. All tests were conducted according to ISO 9459- 2:1995(E). The system was able to operate in various weather and operating conditions and could accommodate the change of inclination of the collector. Initially, the solar collector was tested according to EN12975-2:2006 in order to determine the thermal performance at a flow and operation conditions specified by the standard. Subsequently, the efficiency of the collector operating thermosiphonically was calculated based on quasi-dynamic approach. Finally, a series of correlations were attempted using the data acquired when the collector is operating themosiphonically which are the following: (i) the temperature difference of the water at the outlet and the inlet of the collector (ΔΤ) with the solar global radiation, (ii) the water mass flow with the solar global radiation, (iii) the water mass flow with the temperature difference of the water at the outlet and the inlet of the collector (ΔΤ). The results of the data analysis showed that these parameters are very well correlated between them since the coefficient of determination (R2) is over 0.91 in all cases

Cyprus building energy performance methodology: A comparison of the calculated and measured energy consumption results

In order to fulfil article 4 of the 2002/91/EC Directive (EPBD) a national methodology for the energy performance of buildings was drafted and approved by the Government of Cyprus in 2009. This methodology is in line with the European standards prepared to facilitate EPBD implementation and follows the asset rating approach that is, it represents the intrinsic annual energy use of a building under standardised conditions. CEN standards leave an option, quite suitable for existing and complex buildings, for operational rating, which is an energy rating based on measured amounts of delivered and exported energy. The calculated and measured rating exhibit advantages and disadvantages and as expected the results of the two approaches vary, since the measured rating approach takes into account the effect of user behaviour, the actual weather conditions and the realized (actual) thermal comfort conditions inside the building. This paper presents the Cyprus legal framework for adopting the EPBD and exhibits the Cyprus methodology for the energy performance of buildings. Moreover the advantages and disadvantages of the asset and operational rating approaches are discussed and a comparison of the results of these two approaches for a selected number of dwellings is presented. One of these cases is also examined with respect to the climatic conditions, by changing the climatic zone in which the building is erected. The latter reveals the effect of climate on the calculated energy requirements of the building for both heating and cooling

PEM fuel cells for energy production in solar hydrogen systems

The main barrier for the widespread use of Renewable Energy Sources (RES) systems is their variability and dependence on environmental conditions. Due to this problem the aspect of energy storage becomes more and more important and the prospect of using hydrogen as an energy carrier in order to store energy is becoming more attractive. This can be achieved by using a solar hydrogen energy system (SoHyS) where the electricity produced by the PVs is stored in the form of hydrogen and can be recovered on demand by using a fuel cell. One of the most promising types of fuel cells to be used in such systems is that of Proton Exchange Membrane (PEM) fuel cells due to their numerous advantages such as high efficiency, low emissions, low operating temperature, low noise levels and high energy density. In this work a brief description of PEM fuel cells and their characteristics is presented along with recent patents on some of their main research areas. The future trends of research in this area would be on improving the design for more advanced fuel cell systems so as to compensate some of the most important aspects such as structural integrity, sealing and hydration leve

Experimental investigation of the performance of a Parabolic Trough Collector (PTC) installed in Cyprus

In this paper the performance of a Parabolic Trough Collector located at the Archimedes Solar Energy Laboratory is evaluated. It has an aperture area of 14.4 m2, a concentration ratio of 13.7 and can be operated up to 200°C. The collector aperture is 1208 mm and the receiver pipe is stainless steel 304 L with a diameter of 28mm, coated with selective coating (absorptance: 0.93, emitance: 0.18). The collector in orientated with its axis in the E-W direction tracking the sun in the N-S direction. The advantages of this tracking mode are that very little collector adjustment is required during the day and the full aperture always faces the sun at noon. A programmable tracking system is responsible for keeping the collector focused at all times. The collector is connected to a 300 liters hot water storage tank. The water is pressurized to avoid boiling in the receiver. The performance obtained is very satisfactory and agrees with the performance curve given by the manufacturer

Evaluation of a parabolic trough collector performance

In this paper the collector erected at the Archimedes Solar Energy Laboratory is initially presented followed by the performance evaluation of the collector. The collector is made by Nep Solar from Australia. It has an aperture area of 14.4 m2, a concentration ratio of 13.7 and can be operated up to 200°C. The collector aperture is 1208 mm and the receiver pipe is stainless steel 304 L with a diameter of 28mm, coated with selective coating having an absorptance of 0.93 and an emitance of 0.18. The collector is orientated with its axis in the East-West direction. The advantages of this tracking mode are that very little collector adjustment is required during the day and the full aperture always faces the sun at noon. A dedicated computer-operated tracking system is responsible for keeping the collector focused at all times. The collector is connected to a hot water storage tank which has a capacity of 300 liters. The collector fluid used in the tests is water, which is pressurized to avoid boiling in the receiver. The performance obtained is very satisfactory and agrees with the performance curve given by the manufacture

The introduction of Hydrogen Economy in Cyprus

In this paper the introduction of hydrogen to the current energy system of Cyprus is examined. Drivers and barriers towards hydrogen economy are identified and possible solutions are proposed in terms of both policy planning and infrastructure. The introduction of hydrogen to the current energy system of Cyprus will have numerous advantages in all sectors with the main ones being the reduction of the dependency on imported oil, reduction of carbon dioxide emissions, improvement on the local air quality and the environment in general. The only sustainable and renewable path to produce hydrogen in Cyprus is by exploiting the solar potential of the island which is more than enough to cover its energy needs. This can be achieved by either water electrolysis or solar-thermolytic splitting of water

Use of phase change materials (PCM) for the improvement of energy storage in solar water heating systems

In this paper the use of Phase Change Materials (PCM) in solar storage tanks is considered in an attempt to improve the solar system operation without changing the production line of solar water heater manufacturers. Hot water storage tank is one of the main components of any solar water heating system. It is important to increase the storage capacity and to keep the stratification in these systems, as this affects the effectiveness of the solar system operation. In general, PCMs present high latent heat of evaporation and they offer more storage capacity than water. The experimental investigations of the operation of the storage tank were carried out both during heating up and draw off. In all experiments carried at different initial storage temperatures, number of PCM canisters (1-3) and drawoff rates (1, 3 and 6 l/min), the tanks with PCM show superior performance than the same tank operating in similar conditions without PCM. For the 50 l tank used, two PCM canisters showed the best performance and a draw off profile up to 3 l/min. The flow of 6 l/min seems to be excessive for small storage volume as the high flow rate does not allow the PCM to give its heat to the flowing water. Another experiment performed is the intermitted withdrawal of water from the storage tank so as to simulate the actual use. The results were also positive. Therefore, from this work it is concluded that the use of PCM gives improved storage capacity of the system and improved system behavior during draw-off