Results are presented from a monitoring study of the performance of a sample of UK domestic PV systems. Five-minute average climatic and performance data was recorded for 27 PV systems at two sites for up to 2 years of operation. On average, the annual energy losses due to faults were 3.6% (Site A, first year of operation), 6.6% (Site A, second year of operation) and 18.9% (Site B, first year of operation). Simple empirical models are constructed to describe the performance of the PV systems under ‘normal operation’ (when no faults occur). New analysis techniques are developed which estimate the energy losses of four different fault categories: sustained zero efficiency faults; brief zero efficiency faults; shading; and non-zero efficiency non-shading faults. The results demonstrate that faults have the potential to cause significant energy losses in domestic PV systems. The benefits of applying the data analysis techniques described in this work to PV system clusters and other urban micro-generation technologies are discussed.

The application of hybrid or mixed-mode ventilation in severe arid climates and its integration with other passive cooling strategies is very challenging. This paper presents a systematic evaluation of the performance of various Mixed-Mode cooling strategies for office buildings with different levels of internal heat gain operated in four cities representative of arid climates. The results of simulations made with EnergyPlus are evaluated in terms of appropriate thermal comfort criteria and subsequently potential reductions in plant energy consumption so that the most effective strategies to mitigate the energy consumption associated with air-conditioning processes. The results show that hybrid approaches to maintaining indoor environmental conditions have the potential to save approximately half of the plant energy consumption compared to common active air-conditioning systems. Savings in plant energy due to the application of mixed-mode strategies that include low energy cooling technologies such as radiant, evaporative and ground-coupled cooling could exceed 80%. We conclude that mixed-mode cooling strategies should be able to provide satisfactory indoor environments and can result in highly efficient office building designs and so should be considered for application in arid climates