Jet Propulsion Laboratory

ABSTRACT:
The use of reversible chemical reactions for energy transport and storage for parabolic dish networks is considered. Performance and cost characteristics are estimated for systems using three reactions (sulfur-trioxide decomposition, steam reforming of methane, and carbon-dioxide reforming of methane). Systems are considered with and without storage, and in several energy-delivery configurations that give different profiles of energy delivered versus temperature. Cost estimates are show more derived assuming the use of metal components and of advanced ceramics. (The latter reduces the costs by three- to five-fold.) The process that led to the selection of the three reactions is described, and the effects of varying temperatures, pressures, and heat exchanger sizes are addressed.

A state-of-the-art survey was performed as part of this study. As a result of this survey, it appears that formidable technical risks exist for any attempt to implement the systems analyzed in this study, especially in the area of reactor design and performance. The behavior of all components and complete systems under thermal energy transients is very poorly understood. This study indicates that thermochemical storage systems that store reactants as liquids have efficiencies below 60%, which is in agreement with the findings of earlier investigators. The cost estimates for transport systems have been compared with estimates reported elsewhere for steam and molten-salt thermal energy transport. Based on this comparison, it appears unlikely that reversible-reaction transport will have a compelling advantage in the 427 to 510°C range. This study includes a reactor/heat-exchanger configuration that may, at increased cost, increase the delivery temperature to 790°C or above. In this temperature range, little data exist on thermal (sensible or latent heat) energy transport. show less

ABSTRACT:
This report establishes standard descriptions for solar thermal power plants and develops uniform costing methodologies for nondevelopmental balance-of-plant (BOP) items. The descriptions and methodologies developed are applicable to the major systems under development within the U.S. Department of Energy (DOE) Solar Thermal Program. These systems include the central receiver, parabolic dish, parabolic trough, hemispherical bowl, and solar pond. The standard plant is defined in show more terms of four categories comprising (1) solar energy collection, (2) power conversion, (3) energy storage, and (4) balance-of-plant (BOP). Each of these categories is described in terms of the type and function of components and/or subsystems within the category.

A detailed description is given for the BOP category. BOP contains a number of nondevelopmental items that are common to all solar thermal systems. A standard methodology for determining the costs of these nondevelopmental BOP items is given. The methodology is presented in the form of cost equations involving cost factors such as unit costs. A set of baseline values for the normalized cost factors is also given. These baseline values were selected for use in making comparative assessments of different solar options. For determining the BOP costs for a particular plant at a specified site, the various cost factors must be chosen to meet site-specific requirements. The basis for the derivation of the cost equations and the rationale used in selecting values for cost factors involved in these equations are discussed. An example using the derived BOP methodology is also presented.

Future evolution of the BOP methodology is suggested. The development of scaling techniques for use with certain BOP items, establishment of BOP cost differences among different technologies, and implementation of probabilistic costing methods for an entire power plant are some of the recommendations made for future work. show less

ABSTRACT:
Sixty-seven firms that had received Department of Energy (DOE) funding for development of solar thermal energy systems (STES) were surveyed by telephone in 1981. The primary goal of the survey was to assess the effect of the DOE Solar Thermal Technology Systems program in accelerating STES development.

The 54 firms still developing STES were grouped into a production typology comparing the three major technologies with three basic functions. It was discovered that large and small show more firms were developing primarily central receiver systems, but also typically worked on more than one technology. Most medium-sized firms worked only on distributed systems.

Federal support of STES was perceived as necessary to allow producers to take otherwise unacceptable risks. Approximately half of the respondents would drop out of STES if DOE support were terminated, including a disproportionate number of medium-sized firms. A differentiated view of the technology - taking into account differing firm sizes and the various stages of technology development - was suggested for policy and planning purposes. show less

ABSTRACT:
A preliminary assessment of three conceptual point-focusing distributed solar modules is presented in this report. The basic power conversion units consist of small Brayton or Rankine engines individually coupled to two-axis, tracking, point-focusing solar collectors. An array of such modules can be linked together, via electric transport, to form a small power station. Each module also can be utilized, on a stand-alone basis, as an individual power source.

In the present study the show more technical evaluation and economic analysis were treated separately. Each system concept was optimized by maximizing the thermal output per unit of concentrator area. System performance was then simulated based on the insolation data recorded at Barstow, California (in 1976). Parametric studies concerning concentrator quality and power conversion efficiency were conducted to provide relevant sensitivity relationships and trade-off information. Hardware cost targets were assessed according to the system energy production rate (kWe-hr/yr), and a range of projected energy cost levels (mills/kWe-hr). The trade-off relationship can be utilized as a realistic guideline for establishing concentrator manufacturing requirements and power conversion development targets.

The objective of this investigation is to provide a method of screening candidates for Point-Focusing Distributed Receiver Solar Thermal Systems. Reliable hardware cost estimates are not available at the present time. It is expected that system cost projections will have large uncertainties because they are strongly affected by technology advancement and market penetration situations. The approach adopted in the present study is to calculate the capital investment that would be justified to supply energy at a range of energy costs, assuming a range of performance factors. These relationships can be used whenever updated hardware costs are obtained or whenever proven component performance data are obtained (e.g., improvements in concentrator quality and power conversion efficiency). The strategy is to screen out the least cost effective options that occur within the specified time frame, considering the technological maturity of different power conversion schemes and the degree of readiness of the concentrator manufacturing industry.

The justified capital cost of small (15 kWe output) gas Brayton systems at 816°c (1S00°F) and steam Rankine systems at 538°c (1000°F) has been compared for a range of energy cost values. Accurate values for the efficiency of small power conversion subsystems are not available. However, the current assessment is approximately 35% for Brayton power conversion efficiency, and 25 to 30% for steam Rankine. The results obtained indicate that the Brayton system merits a higher capital cost than the Rankine system for an energy cost target of SO mills/kWe-hr, if the concentrator quality is in the range of 1 to 4 mrad. It is expected that the cost of Brayton concentrators will be greater than the Rankine concentrators. show less