C. Craggs et al., Stochastic modelling of solar irradiance on horizontal and vertical planesat a northerly location, RENEW ENERG, 18(4), 1999, pp. 445-463
Sunshine levels incident in the plane of a photovoltaic panel are the overr
iding influence on electrical output, and modelling solar irradiance is the
refore an essential step in the design and performance prediction of solar
energy conversion systems. This study aims to assess the efficacy of SARIMA
models and their potential for short-term prediction at a northerly latitu
de. Data was collected from a monitoring site on the roof of a 5-storey bui
lding at a city centre location in Newcastle upon Tyne, UK (latitude 55 deg
rees N). Hourly and ten minute data relating to 13 and 15 day periods in tw
o winters (1993, 1994) and two summers (1994, 1995) were utilised. Univaria
te stochastic modelling, using SARIMA models, is carried out for horizontal
and south facing vertical solar irradiance. Results showed that these mode
ls provided a good fit for the ten minute averaged horizontal and vertical
irradiance, with, on average, 82% and 85% of total variation being accounte
d for respectively. Use of hourly averaged data in these models gave a subs
tantial reduction in the fit. Models for the winter data were a poorer fit
than for summer for both orientations. It is concluded that the SARIMA appr
oach can be used to develop prediction methods and to study rapid and large
changes in PV output from extensive areas of solar cladding. (C) 1999 Else
vier Science Ltd. All rights reserved.