Why do steam power plants have to be very large?

Abstract

AcknowledgementsThere are a few people who I would like to thank for assisting me throughout the completion of this thesis. Bachelor of Engineering Thesis iii AbstractWith a lack of investment and limited technological advances, CST power generation has been unable to benefit from industry expertise and consequently failed to appreciate potential cost reductions. Present cost estimates dictate that the minimum economical size for CST plantations is 50MWe. Coincidently, almost 90% of concentrating solar thermal electricity generation is produced by plantations operating with capacities in excess of 50MWe [1].Currently, Australian pre-existing energy markets are penetrable for smaller capacity CST designs with outputs ranging from 1MWe to 30MWe [2]. The aim of this study is to investigate the motives underpinning the lack of market drive and integration of downscaled CST power generation in Australia. Research underpinning this investigation focuses primarily on Parabolic Trough and SolarTower CST plant configurations due to the commercial maturity of each system. As a result, specific process efficiencies were investigated in order to establish prevalent loss mechanisms associated with capacity variations. Examination of the solar field components revealed distinct trends supporting downscaling, notably the collector efficiency of a heliostat field (Solar Tower configuration) shows likely improvement with smaller field size. However, the efficiency of integrated steam turbines was found to be largely dependent on the power block design capacity. Typical turbine efficiency can range between a low of 40% for small capacity, single-stage turbines to a high of up to 90% for large capacity, multi-stage, multivalve condensing turbine [3]. This led to the conclusion that the major contributor to the deterrence of downscaling CST electricity generation is the reduction in the operating efficiency of the power block with plant size. The impact of this is a relative size increase in the thermal energy input into the system in order to compensate for conversion losses. To achieve a greater thermal input, a larger relative solar field is required; this additional cost presents a less attractive investment option.Furthermore, a review of cost trends highlighted further economic constraints imposed by the economies of scale effect in determining relative plant costs. Identification of these key limitations on downscaling CST power generation may subsequently drive further increases into solar investment within Australia and promote sustainable energy production. Bachelor of Engineering Thesis iv

UQ eSpace

“…While this expression was derived for a specific site altitude, authors such as Wagner (2008) and Venus (2016) note that the trend is expected to hold for other sites also, due to the dependence on elevation being minimal compared to the dependence on visibility. This is also evidenced by the use of a similar third order approximation in DELSOL, a reputable program used to model CST plants (Kistler, 1986).…”