Thomas E. Hoff

Distributed generation: An alternative to electric utility investments in system capacity

Distributed generation technologies offer electric utilities an alternative to large system capacity investments. This paper presents a simplified method to determine the value of deferring electric utility capacity investments using distributed generation. Consideration is given to both economic and technical factors, including uncertainty in the price of distributed generation. The technical evaluation is based on measured data from a 500 kW distributed generation PV plant in Kerman, California. Results indicate that the cost savings associated with deferring capacity investments can be accurately estimated using only seven economic parameters and one days worth of distributed generation output and utility system data.

Spatial and temporal variability of solar energy

This article summarizes and analyzes recent research by the authors and others to understand, characterize and model solar resource variability. This research shows that understanding solar energy variability requires a definition of the temporal and spatial context for which variability is assessed; and describes a predictable, quantifiable variability-smoothing space-time continuum from a single point to 1000’s of km and from seconds to days. Implications for solar penetration on the power grid and variability mitigation strategies are discussed.

Solar Resource Variability

In this chapter, we describe a methodology to quantify variability of the solar resource. We describe how the considered temporal scales, from seconds to hours, and geographical scales, from a single point to a subcontinent, are interrelated and lead to a quantifiable smoothing effect. We discuss implications of the temporal/spatial nature of solar-resource variability for the solutions needed to absorb a growing proportion of solar-generated energy on power grids. Variability is a general term that applies to many aspects of solar radiation. For example, it is used to refer to change in the solar resource from one year or one season to the next, as well as change from one site to another ( Gueymard and Wilcox 2011, Vignola 2001).

Managing Risk Using Renewable Energy Technologies

This paper investigates the potential of owning renewable energy technologies to mitigate risk faced by the electric utility industry. It considers the effect of market structure on the plant ownership decision and how the attributes of renewable energy technologies can help to manage risk. Explicit consideration is given to the renewable energy technology’s attributes of fuel costs, environmental costs, modularity, lead time, location flexibility, availability, initial capital costs, and investment reversibility. It concludes that renewable energy technologies, particularly the modular technologies such as photovoltaics and wind, have the potential to provide decision makers with physical risk-management investments.

Economic determination of optimal plant design for photovoltaics in the utility distribution system

A simplified value analysis tool which is to be used in optimizing the design of a distributed grid-connected photovoltaic (PV) plant is presented. The resulting distributed value information may be combined with cost information to determine the most optimal plant design. The methodology and the data necessary to apply this methodology to a specific case are presented.<<ETX>>

Reduce, reuse and renew: one possible approach to cut carbon emissions

Global climate change has become an increasingly important issue over the last several years. This issue reached a climax at the Kyoto Conference in December, 1997 where the US agreed to reduce its greenhouse gas emissions to 7% under its 1990 levels by 2010. This paper describes how distributed resources could be part of an overall solution towards achieving these reductions. It illustrates how a system composed of energy efficiency, distributed cogeneration, and distributed photovoltaics could reduce fuel consumption by 70% in the residential and commercial sectors. This could be a solution that makes economic sense independent of the climate change debate if implemented over the next 30 to 50 years, a timeframe which is not much worse for the climate system than achieving them in ten years, according to most analyses.