Solar energy has been one of the accessible and affordable renewable energy technologies for the last few decades. Photovoltaics and solar thermal collectors are mature technologies to harness solar energy. However, the efficiency of photovoltaics decays at increased operating temperatures, and solar thermal collectors suffer from low exergy. Furthermore, along with several financial, structural, technical and socio-cultural barriers, the limited shadow-free space on building rooftops has significantly affected the adoption of solar energy. Thus, Photovoltaic Thermal (PVT) collectors that combine the advantages of photovoltaic cells and solar thermal collector into a single system have been developed. This study gives an extensive review of different PVT systems for residential applications, their performance indicators, progress, limitations and research opportunities. The literature review indicated that PVT systems used air, water, bi-fluids, nanofluids, refrigerants and phase-change material as the cooling medium and are sometimes integrated with heat pumps and seasonal energy storage. The overall efficiency of a PVT system reached up to 81% depending upon the system design and environmental conditions, and there is generally a trade-off between thermal and electrical efficiency. The review also highlights future research prospects in areas such as materials for PVT collector design, long-term reliability experiments, multi-objective design optimisation, techno-exergo-economics and photovoltaic recycling.

Competing relationships and a lack of collaboration are common in the construction industry. Consequently, many reasons, such as lack of trust, unfair risk sharing and ineffective communication, are highlighted by actors as challenges in the construction sector. Collaboration has been demonstrated as a solution for these challenges for the construction industry. However, collaborative environments are still far from effective in emerging economies with a lack of research and information available for such countries. We have used the Kurdistan region of Iraq to investigate and explore these challenges using systematic enquiry, utilizing quantitative and qualitative methods. This article aims to explore these challenges, by reviewing past literature and investigating construction practices to better quantify those factors that underlie collaboration. A comprehensive review of the literature was conducted to identify the most critical factors. Then, a questionnaire was used to survey the opinions of practitioners, analysed through exploratory factor analysis. Six factors were identified: project vision, participant behaviour, communication, relationship definition, contractual agreements and systematic process. Additionally, the paper provides suggestions as to how industry might apply such factors. This article contributes to a scarce literature regarding construction projects in Kurdistan region and emerging economies in general.