• Energy Research

In this paper the enhancement of temperature sensitive product conditions when the product is placed in chilly bins is studied. The aim is to develop a numerical model for a bin used to store cold or hot food. Phase change materials (PCM) were used to allow longer time for transport and storage without affecting the quality of perishable products. The mathematical model is validated with the measured experimental data which proved the usefulness of using PCM in cold storage. The benefit of using PCM was demonstrated since it maintained product temperature constant for longer periods. The numerical model may be used for effective design of new chilly bins for use in storage of food.

Abstract A desalination unit based on humidifying air by direct contact with hot water obtained from a flat plate solar collector was designed and constructed. The air was circulated in a closed loop using a blower. The humid air was partially condensed in a large surface condenser where most of the latent heat from water condensation was used to preheat the saline water. Daily production of 12 l/m 2 was achieved, which is much higher than that of any single basin still.

Biodiesel is considered a promising replacement to petroleum-derived diesel. Using oils extracted from agricultural crops competes with their use as food and cannot realistically satisfy the global demand of diesel-fuel requirements. On the other hand, microalgae, which have a much higher oil yield per hectare, compared to oil crops, appear to be a source that has the potential to completely replace fossil diesel. Microalgae oil extraction is a major step in the overall biodiesel production process. Recently, supercritical carbon dioxide (SC-CO2) has been proposed to replace conventional solvent extraction techniques because it is nontoxic, nonhazardous, chemically stable, and inexpensive. It uses environmentally acceptable solvent, which can easily be separated from the products. In addition, the use of SC-CO2as a reaction media has also been proposed to eliminate the inhibition limitations that encounter biodiesel production reaction using immobilized enzyme as a catalyst. Furthermore, using SC-CO2allows easy separation of the product. In this paper, conventional biodiesel production with first generation feedstock, using chemical catalysts and solvent-extraction, is compared to new technologies with an emphasis on using microalgae, immobilized lipase, and SC-CO2as an extraction solvent and reaction media.

Abstract This paper investigates the importance of the design parameters when looking at possible energy savings and comfort enhancement in a building using Phase Change Materials (PCMs). Computer based simulations are performed using a simulation software for modelling a house and its thermal behaviour over a year. It is found that by varying the heating set point and the phase change (melting) temperature range of the PCM, significant changes can be observed. Some poor scenarios show that the integration of PCM can increase both the discomfort (up to 6% more discomfort hours) and the energy requirements (up to 25% more energy needed). On the other hand, appropriate scenarios bring significant energy savings (up to 33% less energy needed) and comfort enhancement (up to 31% less discomfort hours). This highlights the strong need for a clever design when integrating PCM into buildings. The goal is to find a trade-off between energy savings and comfort enhancement. The PCM with a phase change temperature range between 21 °C and 26 °C shows the best results. The study is based on climate conditions for Auckland City in New Zealand but most of the conclusions drawn can be applied to any climate.

Public universities face the challenge of retrofitting the actual campus buildings into nearly zero-energy buildings (NZEB). In this study, a novel methodology for evaluating historical energy use and renewable energy production for all the buildings of a university, including hourly, daily and monthly data assessments is presented. This analysis is useful as a baseline for comparisons with future energy retrofits and enables determining the current gap between actual energy indicators at building and campus levels and the established limits for NZEB non-residential buildings in the European Union. The methodology is applied to a case study at the University of Lleida, a typical average-size university in Spain. Results show a wide variation in energy use among campus buildings, ranging between 50 and 470 kWh/m2 year. Constant or slightly increasing energy use and decreasing trends in renewable energy generation are observed. The daily electricity profiles have shown similar patterns among buildings and substantial potential energy savings during unoccupied periods. In the NZEB analysis, the average non-renewable primary energy use is about 4 times higher than the maximum estimated Spanish threshold range of 45-55 kWh/m2 year. Deep energy renovation strategies are, thus, needed for universities to meet EU NZEB targets. The research leading to these results has received funding from the European Union’s Seventh Framework Programme (FP7/2007-2013) under grant agreement no. PIRSES-GA-2013-610692 (INNOSTORAGE).

Abstract Solar desalination is gradually emerging as a successful renewable energy source of producing fresh water. Solar Multi-Effect Humidification (MEH) units based on the humidification-dehumidification principle are considered as the most viable among solar desalination units. A simulation study of these units leads to a better understanding of the performance of such type of desalination units. This study therefore focuses on studying and analysing the effects and performance of various components involved in the process along with the study of the effect of water feed flow rate on the desalination production. To our knowledge, there is no such comprehensive model available in the literature. This study could lead a step further in the commercialisation of solar desalination units based on the humidification-dehumidification principle.

Abstract The purpose of this paper is to assess, through experiment and Matlab modelling, whether the use of phase change material (PCM) infused graphite with an external finned heat sink is viable as a method of PV thermal regulation. The effect four different thermal regulation techniques (cases A, B, C and D) on the thermal performance, point-based efficiency and overall efficiency of a PV panel have been studied. These four cases are case A, the PV panel with no thermal regulation, case B, the PV panel with 30 mm thick PCM infused graphite attached to the rear, case C, the PV with a finned heat sink attached to the rear and case D, the PV panel with a combination of PCM infused graphite and finned heat sink. Special attention has been paid to the effect that the infusion of PCM into graphite has on the thermal regulation effects of the PCM itself. The experimental setup consisted of two mono-crystalline silicon solar panels linked independently to a computer, which recorded the power generated from each solar panel, as well as the temperature at the front and rear of each panel. The insolation was supplied by two 500 W halogen lamps positioned 0.15 m away from the centre of each solar panel, with a peak insolation of 920 W/m 2 . The intensity of the insolation was measured with an incident-light photometer. The power supplied to the halogen lamps was controlled by the computer and a simple voltage control device. Out of the four thermal regulation techniques, case D was the most effective at increasing overall efficiency of the PV panel, with the greatest overall efficiency increase of 12.97. The thermal regulation effects of PCM and heat sinks are additive since the PCM creates a shift in temperature rise, whilst heat sink reduces the peak temperature. The increase in thermal conductivity of the PCM from 0.25 W m −1 K −1 to 16.6 W m −1 K −1 provided by the infusion of PCM into graphite has significant added benefits over pure PCM. Further analysis based on overall efficiency demonstrates that combining PCM with heat sinks is in fact essential.

Abstract Application of phase change materials (PCMs) in lightweight building is growing due to the high latent heat of fusion of PCMs and their ability to control temperature by absorbing and releasing heat efficiently. Wood-plastic composites (WPC) are materials used in the interior parts of buildings that have improved properties compared to conventional materials. However, these materials have low energy storage capacity, which can be improved by incorporating PCM in them. Leakage of PCM is a major obstacle to the industrial applications, which can be solved through the use of microencapsulated PCM (MEPCM). This paper presents the performance tests conducted for a composite of wood-plastic-MEPCM for using in buildings for thermal storage. The wood-plastic-MEPCM composites were produced in this project using compression molding and their thermal and mechanical properties were investigated using DSC analysis, cycling test, leakage test, and three point bending analysis. The results showed that there is no leakage of PCM during phase change. The results also indicated that the composite has reasonable thermal properties, but its mechanical properties need to be improved by increasing the pressure during the molding process or by using extrusion method. The produced composites can be used as a building material for thermal energy management of building.