In Japan, utilities are examining approaches to reduce temperature-sensitive loads (residential and commercial) that have been growing faster than utility average growth rates over the past decade. A number of utility-industry partnerships have formed to develop and market PV powered systems to help meet this growth. The first systems under development are PV-powered air conditioners for residential and commercial buildings. Significant national effort: are underway in Japan and in many European countries to advance the development and integration of commercial PV systems. In most cases, these systems will be interconnected with the utility distribution grid through inverters. The cost of these systems are being shared by the customers and various government agencies. Capacity and availability factors are key indicators of the operational efficacy of a PV system. Capacity factor is defined in the section on economic considerations that follows. The availability factor is the ratio of the number of
hours the plant operated to the number of hours insolation was high enough for the plant to operate. The data shown in Table 1 indicate a trend of steady progress in both during the recent past. Based on the documented experience of the larger PV plants, a number of conclusions can be drawn [43].
• Nameplate plant ratings, based on module peak power ratings, do not accurately reflect what PV plants produce under standard conditions of 1 kW/m2 and 20˚C ambient air temperatures.
• Capacity factors for plants with high availability range up to 35%.
• While failures have occurred in early systems, more recent plant designs show markedly better availability.