125Double Counting How Much Is Really Out There

Capacity resources are sold on a nonfirm (interruptible) basis and reported by purchasers as firm capacity. Power marketers frequently aggregate nonfirm

FIGURE 1.4

U.S. utility-owned generation capacity by fuel source (1998); sources are shown from top to bottom in order of the table at right. Solar, wind, and geothermal sources are too small to show at this scale (U.S. DOE Energy Information Administration).

FIGURE 1.4

U.S. utility-owned generation capacity by fuel source (1998); sources are shown from top to bottom in order of the table at right. Solar, wind, and geothermal sources are too small to show at this scale (U.S. DOE Energy Information Administration).

FIGURE 1.5

Non utility-owned power generation capacity by six market sectors; units are MW (U.S. DOE Energy Information Administration).

FIGURE 1.5

Non utility-owned power generation capacity by six market sectors; units are MW (U.S. DOE Energy Information Administration).

purchases in their portfolios to allow sales on a firm basis, similar to the way utilities use generation capacity margins to firm up supply. Under current reporting practices, the entity that sells nonfirm capacity to a power marketer would report this as its own installed capacity because, as a nonfirm contract, it really is available to serve the seller's own firm demand. The entity that purchases this illusory firm capacity from the marketer's portfolio also reports it as firm capacity, thus doubling the capacity reported as available. When this practice is combined with utilities' increasing reliance on "unknown" sources for future supply, the reliability implications are compounded.

Identifying the source of an energy supply can be difficult for the control area operator in an environment where transactions may change ownership several times and be subdivided and recombined before reaching a given customer. Without real-time metering, the operator lacks the necessary transparency to identify a supplier's portion of a system's load. It can become impossible to identify situations where energy demand exceeds reserved transmission capacity. System operators must be able to identify points of delivery, intermediary control areas, points of receipt, and levels of firmness so that supply interruptions respect the contractual priorities of each transaction.

A significant portion of all power sales are part of extended daisy chains, involving the repeated retrading of power by market participants who have no intention of ever physically delivering the power. These deals represent multiple resales of the same generation that used to flow directly from vertically integrated utilities to their ultimate customers or to other distribution utilities for resale. Up to 80% of power marketer transactions are financially firm, without any physical transfer of power. The entrance of new marketers, many of whom deal only in financial transactions, has helped to increase the capital size of power markets. But, like printed currency off the gold standard, many of these transactions are not backed by the ability to physically deliver power, exacerbating the volatility of prices under peak conditions.

Solar Stirling Engine Basics Explained

Solar Stirling Engine Basics Explained

The solar Stirling engine is progressively becoming a viable alternative to solar panels for its higher efficiency. Stirling engines might be the best way to harvest the power provided by the sun. This is an easy-to-understand explanation of how Stirling engines work, the different types, and why they are more efficient than steam engines.

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