Evaluation of the Potential for Photovoltaic Power Generation in Illinois (2006)

Solar power production was estimated from hourly solar insolation data collected at 19 sites across Illinois from 1991-2004 by the Illinois State Water Survey (ISWS).Values were compared with more limited, experimental data and a solar radiation model reported in the literature.All prior data sources are in good agreement with the ISWS values with discrepancies noted.Based on analyses of the current Illinois data, an estimate was made of potential power production from small to medium-sized photovoltaic modules and systems in Illinois.ISWS insolation data were converted from observed values using flat-plate pyramometers oriented horizontally, to expected values from south-facing sensors tilted from horizontal by the latitude of each station, a typical orientation of photovoltaic systems.Champaign, Illinois, centrally located in the state, was chosen as a hypothetical solar power array site.A large operational array in Arizona was used as a model of photovoltaic system performance.Expected differences in power production due to technologies chosen for the hypothetical array and climatological conditions in Illinois as compared to the model array were considered.The use of concentrated solar collectors was not explored.The expected power output based on two array designs was calculated to be 134-180 kilowatt hours per square meter of array per year.Considering the unsubsidized cost of a photovoltaic array necessary to provide power for an individual dwelling, the system cannot expect to match grid power on a cost basis at this time.However, the comparison becomes more favorable in relatively remote locations where transmission lines for grid connection must be established.That is, photovoltaics may be cost effective for small remote applications such as powering billboards, but generally not for homes or businesses.Cost effectiveness of photovoltaics increases significantly when major subsidies and economy-of-scale discounts in both module and balance-of-system costs are available to reduce the initial system price and with designs of large-scale array systems.Photovoltaics also may be worth considering to offset the most expensive power produced by utilities, peak power, and for distributed power generation providing grid support.collected using Eppley model 8-48 black and white pyranometers mounted on 2.7 meter (m) arms, extending south from each monitoring tower at a height of approximately 2 m above the ground (Hollinger et al. 1994).The pyranometers were factory calibrated from 295 to 2,800 nanometers to a National Institute for Standards and Technology traceable blackbody.Pyranometer output is 9 to 10 microvolts per watt per meter squared with a temperature dependence of 1.5 percent over a temperature range of -20 to 40C, with a linear response within 1 percent over its rated intensity range and a response time of 4 seconds.Cosine response exceeds 5 percent from normalization at zenith angles of 70 to 80 degrees and exceeds 2 percent for zenith angles of 0 to 70 degrees.Assuming the sun is between zenith angles of 0 to 70 degrees 67 percent of the day, the accuracy would be within 5.5 percent.All results fall outside the expected worst-case errors of the pyranometers and, therefore, should not be due to pyranometer measurement errors.Pyranometer output is "global" solar radiation data, collected from all parts of the sky simultaneously.This is similar to collection of energy by a flat-plate solar array oriented horizontally.These data are not directly relevant to a concentrating solar collector, which uses reflectors to concentrate solar