**1. Introduction**

64 Modeling and Optimization of Renewable Energy Systems

improvement and load peak clipping. Also using DG's in systems has disadvantages such as

While a DG is inserted in distribution system, some parts of system lose their radial characteristics and protective devices coordination is lost. If the influence of DG be intensive, then coordination of protective devices with usual method is impossible. The proposed adaptive protection scheme does short circuit analysis online and whenever system configuration varies, this analysis execution is done and a look up table is conformed. The adaptive scheme diagnoses fault location, faulted bus and faulted zone by

If the fault is permanent, adaptive relay disconnected only the faulted zone and DG's in that zone and other zones continue their normal operation. If the fault is transient, adaptive relay sends trip command to faulted zone and its DG's circuit breakers and then does a reclosing operation in three time stage. If the fault be cleared in each stage, relay sends close command to zone circuit breaker and sends close command to DG circuit breaker after 2 s or 3 s for synchronization operation. Adaptive relay disconnects DG's in faulted zone wether

Barker P. and De Mello R. (2003). Determining the Impact of Distributed Generation on

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Brahma S. (2004). Development of Adaptive Protection Scheme for Distribution Systems

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interaction with protective systems, voltage control problems and DG islanding.

the discussed method.

**10. References** 

the fault is permanent or transient.

There is a growing demand for electricity in the developing countries. The conventional approaches to meet this need are through the construction of fossil-fuel power plants. The operation of these plants, however, releases carbon dioxide and contributes to the problem of climate change. Furthermore, many of these countries rely on imports for their energy needs and the purchase of fossil fuel weakens their financial potential. Unlike hydrocarbon energies, renewable energy can be developed from resources which are constantly replenished and will never run out. These energies include:


Many developing countries have an abundance of a natural energy source: solar radiation. Operation of solar thermal power plants (STPP) would reduce their reliance on fossil fuels. Regions that could make use of these systems include Southern Africa, Middle East and North Africa (MENA) India, Northern Mexico and parts of South America. The developed regions of Southwest U.S. and Australia could also benefit from this technology.

In this chapter attempt is made to have a brief introduction of solar thermal power plant (STPP) systems and cycles. To develop new approaches to exergoeconomic analysis of such plants, the main elements of exergy and economic analysis are explained. Various methods of optimization from single objective to multi objectives applicable to STPP are developed. Finally application of the developed optimization methods for a sample integrated solar

Exergoeconomic Analysis and Optimization of Solar Thermal Power Plants 67

The SEGS plants in California utilized a solar steam system to provide inlet steam for a conventional (Rankine) cycle steam turbine power plant. In addition to the standard SEGS configuration, Luz International Limited conceived a system configuration for a solar field integrated with a gas-fired combined cycle plant. This concept, known as the Integrated Solar Combined Cycle System (ISCCS), is derived from a conventional combined cycle design in which the exhaust heat from the combustion turbine generates steam in a heat recovery steam generator (HRSG) to drive a steam turbine connected to a generator, with supplemental heat input from the solar field to increase the steam to the steam turbine (Baghernejad & Yaghoubi, 2010). This approach offers a potentially more cost effective and thermodynamically efficient method to utilize solar thermal energy to produce electricity compared to the use of solar energy with a conventional boiler fired (Rankine) cycle plant. In comparison to existing Rankine cycle power plants with parabolic trough technology (SEGS), ISCCS plants offer three principal advantages: First, solar energy can be converted to electric energy at a higher efficiency. Second, the incremental costs for a larger steam turbine are less than the overall unit cost in a solar-only plant. Third, an integrated plant does not suffer from the thermal inefficiencies associated with the daily start-up and shutdown of the steam turbine. Crucial issues in the effective utilization of parabolic trough solar fields in combination with combined cycle plants are the ability to achieve a significant reduction in global emissions, the effective annual heat rate of the combined system, and the

Fig. 1. Schematic diagram of a Rankine- Cycle STTP

cost impact on the plant output (Baghernejad & Yaghoubi, 2011a).

combined cycle system (ISCCS) are illustrated. It has been shown that the new optimization schemes are strong tools which can be used to find optimum operating condition based on the main objectives of any thermal plant.
