Phase change materials (PCMs) offer great potential as a latent heat energy storage technique to provide energy efficient systems in new and existing residential buildings. Due to their unique characteristic of high storage densities and latent heat properties, PCMs provide opportunities for greater energy storage in many applications for residential buildings. These applications include, but are not limited to, solar water heating, space heating/cooling, and waste heat recovery. This study reviews PCM systems in residential building applications, with a focus on their major disadvantages and concludes with proposals for future development. Several disadvantages of PCM use in the given application have been identified and include; super cooling, low thermal conductivity, phase segregation, fire safety, and cost. The issues caused by super cooling and phase segregation lead to thermal cycling degradation, limiting the useful lifecycle of the material. These issues could limit their potential in building applications, which require systems of a long lifespan. Low thermal conductivities can slow down the rate at which heat is distributed or absorbed from the building, which affect the occupants comfort and as well as the efficiency of the system. Ideas based on the current research on ways to limit these disadvantages are included in the study. This study also identifies that further research is required on novel maintenance ways for the PCM systems after they have been installed.

This work investigates life cycle costing analysis as a tool to estimate the cost of hydrogen to be used as fuel for Hydrogen Fuel Cell vehicles (HFCVs). The method of life cycle costing and economic data are considered to estimate the cost of hydrogen for centralised and decentralised production processes. In the current study, two major hydrogen production methods are considered, methane reforming and water electrolysis. The costing frameworks are defined for hydrogen production, transportation and final application. The results show that hydrogen production via centralised methane reforming is financially viable for future transport applications. The ownership cost of HFCVs shows the highest cost among other costs of life cycle analysis.