Mark Mehos

Enabling Greater Penetration of Solar Power via the Use of CSP with Thermal Energy Storage

At high penetration of solar generation there are a number of challenges to economically integrating this variable and uncertain resource. These include the limited coincidence between the solar resource and normal demand patterns and limited flexibility of conventional generators to accommodate variable generation resources. Of the large number of technologies that can be used to enable greater penetration of variable generators, concentrating solar power (CSP) with thermal energy storage (TES) presents a number of advantages. The use of storage enables this technology to shift energy production to periods of high demand or reduced solar output. In addition, CSP can provide substantial grid flexibility by rapidly changing output in response to the highly variable net load created by high penetration of solar (and wind) generation. In this work we examine the degree to which CSP may be complementary to PV by performing a set of simulations in the U.S. Southwest to demonstrate the general potential of CSP with TES to enable greater use of solar generation, including additional PV.

Solar Advisor Model User Guide for Version 2.0

The Solar Advisor Model (SAM) provides a consistent framework for analyzing and comparing power system costs and performance across the range of solar technologies and markets, from photovoltaic systems for residential and commercial markets to concentrating solar power and large photovoltaic systems for utility markets. This manual describes Version 2.0 of the software, which can model photovoltaic and concentrating solar power technologies for electric applications for several markets. The current version of the Solar Advisor Model does not model solar heating and lighting technologies.

Estimating the Performance and Economic Value of Multiple Concentrating Solar Power Technologies in a Production Cost Model

NOTICE This report was prepared as an account of work sponsored by an agency of the United States government. Neither the United States government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States government or any agency thereof. Any errors or omissions are solely the responsibility of the authors.

Solar destruction of hazardous chemicals

Abstract The objective of this work was to demonstrate that concentrated solar energy can be used to effectively destroy hazardous chemicals. The study involved the design and construction of a photochemical reactor that was used in a unique solar experiment that utilized concentrated sunlight to destroy a dioxin. Temperatures from 750 to 1000 °C were achieved along with solar flux levels from 500 to 1000 times normal sunlight (50–100 W/cm2). Field testing demonstrated that concentrated sunlight can effectively destroy a hazardous chemical (1,2,3,4‐tetrachlorodibenzo‐p‐dioxin). Significant enhancements were also shown to exist due to the presence of solar photons of wavelength 300–400 nm.

Planting the seed

In the United States and around the world, interest in concentrating solar power (CSP) is growing rapidly and its use is increasing. This solar thermal technology can meet a significant share of our electricity demand. Yet, while CSPs market share rises, concerns about the potential impact of CSP-generated electricity on the stability and operation of the U.S. power grid might create barriers to its future expansion in America.

Solar Energy: The Largest Energy Resource

This chapter discusses the solar energy as the largest energy resource. The fraction of electricity generated by solar technologies is small but growing rapidly, with enormous potential to generate a large fraction of the worlds electricity needs while significantly reducing global carbon emissions. Realizing this potential, however, will require overcoming both technical and economic barriers. In the short term, it will be important to decrease costs, improve solar conversion efficiency, and implement electricity rate structures that capture the time-varying value of solar-generated electricity. In the long term, challenges will include using material resources more efficiently, integrating intermittent photovoltaic electricity into the grid, and building transmission capacity for utility-scale solar generation systems linking areas with good solar resources to population centers.

Design and Cost of Solar Photocatalytic Systems for Groundwater Remediation

Laboratory and small-scale field experiments have shown that sunlight in conjunction with a simple catalyst can be used to detoxify water contaminated with a variety of hazardous chemicals. This study builds on previous analyses and recent field test data to predict the cost and performance of a representative commercial water detoxification system. Three different solar operating configurations are explored for the treatment of 100,000 gal/day of groundwater contaminated with trichloroethylene. Current costs for solar water detoxification systems are projected to be comparable to those for conventional treatment technologies such as carbon adsorption and electric lamp-powered, ultraviolet light/hydrogen peroxide systems.

Concentrating Solar Power

Concentrating Solar Power (CSP) has the potential to contribute significantly to the generation of electricity by renewable energy resources in the U.S.. Thermal storage can extend the duty cycle of CSP beyond daytime hours to early evening where the value of electricity is often the highest. The potential solar resource for the southwest U.S. is identified, along with the need to add power lines to bring the power to consumers. CSP plants in the U.S. and abroad are described. The CSP cost of electricity at the busbar is discussed. With current incentives, CSP is approaching competiveness with conventional gas‐fired systems during peak‐demand hours when the price of electricity is the highest. It is projected that a mature CSP industry of over 4 GWe will be able to reduce the energy cost by about 50%, and that U.S. capacity could be 120 GW by 2050.

Dish/Stirling hybrid-heat-pipe-receiver design and test results

A 75-kW/sub t/ hybrid receiver, intended for dish/Stirling application, has been designed, fabricated, and tested. The receiver is a 6-x scale-up of our earlier successful bench-scale hybrid concept. It is a major extension of the bench-scale concept to a compact package comprising a fully-integrated solar absorber, gas-fired surface, heat pipe, combustor, and recuperator. The device is built around a sodium heat pipe having a spherical-dome solar absorber and a pin-fin-studded, cylindrical-sidewall, gas-fired surface. The combustion system uses a metal-matrix burner, with premixed air and natural gas. The recuperator is a folded-membrane design. The receiver is designed for simultaneous solar and gas-fired heating, with a nominal throughput of 75 kW/sub t/. The nominal operating (sodium vapor) temperature is 750 C. The receiver has been ground tested (gas only) at throughput power levels from 18 to 75 kW/sub t/and output temperatures up to 750 C. It was tested in four different orientations, corresponding to sun elevations of 12, 22, 45 and 80 degrees. The tests have established several landmarks at the 75 kW/sub t/ power level, including: (1) preheat of fuel/air mixtures above 600 C without preignition, (2) internal wall temperatures over 800 C with minimal warping, particularly at critical internal seals, and (3) 68% thermal efficiency including parasitics. We believe the efficiency could be boosted to 75% by the addition of an external insulation package. Our tests also verified smooth ignition, as well as the absence thermocouples, differential pressure gauges on all major flow elements, and calorimetry. Some nonfatal problems occurred during the tests, including occasional transient leakage at an internal seal, and warping of the burner matrix. Late in the scheduled tests, a hot spot developed on the heat-pipe gas-fired surface. This behavior is believed to be the result of a wick flaw; it has been seen in other heat pipes, and has been the subject of an ongoing separate effort. Design details and rationale will be presented, along with test data illustrating the behavior of the receiver, and demonstrating its efficiency.

Cost and Performance Solar Analysis Model for All Solar Technologies

A comprehensive solar technology systems analysis model is being developed at NREL to support program planning for the U.S. Department of Energy’s Solar Energy Technologies Program (SETP). This new model will calculate the costs, finances and performance of current solar technologies including solar heat (typically solar domestic hot water), concentrating solar power, photovoltaics (PV) and solar hybrid lighting. The primary function of the model is to allow users to investigate the impact of variations in physical, cost, and financial parameters to better understand their impact on key figures of merit. Although a variety of models already exist to examine various issues with each individual technology, this model, when fully implemented in the future, will have the capability to analyze and compare different solar technologies (utility-scale PV vs. CSP for example) within the same interface while making use of similar cost and financing assumptions. A central idea for this model is to have a user-friendly interface while at the same time having a detailed, accurate analysis for each of the technologies. The underlying performance engine, which is hidden from the user, is TRNSYS, which already contains an extensive library of solar technology models. There are built-in cost models or the user can access their own spreadsheet-based cost model. The financial model is an extension of an existing validated finance model. This paper will discuss the goals and implementation of the model and present several sample results for interesting sensitivities.Copyright