Pre-/Post-Construction Solar Energy Forecasting: Methods, Measurements and Uncertainties
from V-Bar, LLC

Presenter: Gregory S. Poulos, PhD Atmospheric Sciences
Summary: Uncertainties in... solar energy resource assessment can be characterized as part of investment-grade analysis. These uncertainties can be minimized profitably with on-site measurements.

Reducing Uncertainty in Solar Energy Estimates:
A Case Study
from AWS Truepower, LLC March 2012

Presenter: Marie Schnitzer, Senior Director, Solar & Investment Services
Summary: As the solar industry matures, on-site data is becoming more and more important for the financial community. Reducing measurement uncertainties in the solar resource assessment will make the project more attractive and less risky to outside investors.

Rating Criteria for Solar Power Projects: Utility-Scale Photovoltaic and Concentrating Solar Power
Available at Fitch Ratings (Free with registration)

URL: http://www.fitchratings.com/creditdesk/reports/report_frame.cfm?rpt_id=701053

This criteria report evaluates debt issue for a broad range of utility-scale photovoltaic (PV), concentrating PV (CPV), and thermal concentrating solar power (CSP) plants.

Solar Resource Assessment and Why it Matters
from AWS Truepower

Authors: Bruce Bailey, Marie Schnitzer
Summary: Onsite monitoring provides significant value to assessing a project's potential, translating to higher confidence in energy estimates.

Improved Accuracy for Low-Cost Solar Irradiance Sensors
White Paper from Sandia National Laboratories:

Authors: D.L. King, W.E. Boyson, B.R. Hansen, and W.I. Bower
Abstract: Accurate measurements of broadband (full spectrum) solar irradiance are fundamental to the successful implementation of solar power systems, both photovoltaic and solar thermal. Historically, acceptable measurement accuracy has been achieved using expensive thermopile-based pyranometers and pyrheliometers. The measurement limitations and sensitivities of these expensive radiometers are a topic that has been addressed elsewhere. This paper demonstrates how to achieve acceptable accuracy (±3%) in irradiance measurements using sensors costing less than one-tenth that of typical thermopile devices. The low-cost devices use either silicon photodiodes or photovoltaic cells as sensors, and in addition to low-cost, have several operational advantages.

Solar Resource Assessment: Minimizing Project Uncertainty
Article from Solar Novus Today | 21 December 2010

Author: Anne Fischer
Summary: An integral step in getting any solar project up and running is the solar resource assessment. This involves characterizing the available solar resource and local meteorological attributes. When making assessments for large distributed generation projects of more than 500 kW and utility-scale projects of more than 5MW it is imperative to evaluate the risk associated with power purchase agreements (PPA) or off-taker requirements as well as to build a case for financial funding.

Li-Cor LI-200 Pyranometer Characteristics and Comparison to ISO/WMO Specifications
August 2011

LI-COR LI-200 Pyranometer: Characteristics and Comparison to ISO/WMO Specifications

Best Practices for Solar Assessment 3TIER
July 7, 2011

Developing a solar project requires a large upfront investment. A standard development roadmap conserves time and money and ensures that the most promising projects are constructed. Each stage of development asks different questions about the solar resource and each stage requires varying degrees of information and investment of financial resources.

Once a promising site is identified, a more in-depth analysis is required to design the project, secure funding, and better quantify the long-term availability of the solar resource.

The Risks of Using TMY Data 3TIER
July 7, 2011

Developing a solar project requires a large upfront investment. A standard development roadmap conserves time and money and ensures that the most promising projects are constructed. Each stage of development asks different questions about the solar resource and each stage requires varying degrees of information and investment of financial resources.Many people incorrectly assume that solar resources do not stray far from their long-term averages and that year-to-year variability is minimal. However, depending on the characteristics of a site, studies have shown that on average annual irradiance means can differ from the long-term mean by 5% for GHI and by as much as 20% for DNI. While TMY datasets provide a good estimate of the average solar irradiance at a site, they are not a good indicator of conditions over the next year, or even the next 5 years.