Heliostat-based concentrating solar-thermal power (CSP) systems can offer immense potential to provide low-cost, dispatchable renewable thermal and electrical energy to help achieve 100% decarbonized energy infrastructure in the United States. Heliostats are a major determinant of both capital cost and performance of state-of-the-art commercial molten salt towers and Generation 3 CSP systems. In 2021, the U.S. Department of Energy (DOE) Solar Energy Technologies Office (SETO) launched the Heliostat Consortium (HelioCon), a five-year initiative to advance heliostat technologies. The HelioCon mission is threefold: (1) establish strategic core testing and modeling capabilities and infrastructure at national labs; (2) support heliostat technology development in relevant industries; and (3) serve as a central repository to integrate industry, academia, and other stakeholders for heliostat technology research, development, validation, and deployment. In the past years, HelioCon has conducted a roadmapping study on advancing heliostat technologies, intended as a central reference for the entire CSP community; also a RFP process to issue a number of projects to engage a wider RD community.
Heliostat calibration is crucial for efficient solar tower power plant operation. Geometry-based models are reliable but yield moderate accuracy, while neural networks promise higher accuracy but need high amounts of data. We introduce a hybrid model that combines a reliable geometric model with a neural network disturbance model over a regularization sweep. Using real measurement data from the Jülich solar tower, we achieve higher accuracies than rigid body models starting from the first measurement, with a top performance below 0.7 milliradians. Our approach reduces data requirements of deep learning models, making them promising for heliostat calibration in solar tower power plants.
Heliostats with active adjustment of surface shape and provision for highly accurate orientation are being prototyped for use with receivers with secondary reflectors, to focus sunlight at concentrations as high as 4,000 suns and at high power, > 1 MW. One application is making green hydrogen from water. Heliostats in a field will each form a disc image of the sun, all centered on a compound paraboloidal concentrator (CPC). A mechanical linkage to the cross axis drive of target-axis mount drive continuously adjusts the shape of each reflector through the day, as needed for the changing angle of incidence.
NREL is presenting an indoor optical measurement system for large heliostat mirrors. This is a target-based deflectometry system, which uses a thin printed patterned targets and a moving camera to scan large mirrors, measuring the surface slope. This system is compared to existing fringe deflectometry and photogrammetry measurement systems, and the computer vision techniques that make it possible are described. While it cannot achieve the resolution of a fringe deflectometry system, the simplicity and low cost of setup make it well suited for the CSP industry.
The development of renewable energy sources is of vital importance, not only in the fight against climate change but also in securing the energy supply. In this context, solar technologies are already playing an essential role in the shift towards carbon-neutral economies, while ensuring a reliable and competitive energy supply. The durability and performance of solar components are crucial to increase the reliability and output of solar power plants and ultimately reducing the cost of electricity. Both the glass used as the front cover of photovoltaic modules and the absorber tubes of parabolic trough collectors currently include anti-reflective (AR) coatings; however, these coatings have not yet convincingly demonstrated their durability in the field, and there are reasonable doubts about their resistance against abrasion. Also, coatings with anti-soiling (AS) functionality are now being explored and laboratory-scale developments are being carried out on coatings with passive cooling functionality that bring higher efficiency and longer service lifetime to PV modules by reducing their operating temperature. Unfortunately, these developments are still far from demonstrating relevant improvements and even further away from demonstrating the required durability. In this work, this issue has been addressed through an innovative approach, developing a process that is not a conventional coating at all, but is based on a combination of micro and nano-structuring of the glass surface itself, which provides the three functionalities mentioned above, far exceeding the characteristics of any of the current solutions: anti-reflective (AR) with an improvement of more than 2.3%, anti-soiling (AS) with a reduction in the rate of soiling of 48% and passive cooling, with cooling peaks of up to 2.5 ºC. In addition to these significant improvements over the current state of the art, the most relevant aspect of the development is the quantitative improvement in its durability, thanks to the innovative technique of structuring the glass surface itself, which does not involve any added material and maintains the mechanical properties of the surface. Thus, this structured glass applied to solar technology will result in a reduction of the LCOE, favouring the transition towards a sustainable energy model and displacing the use of fossil fuels.
Thermochemical hydrogen production via redox reactions with the input of concentrated solar thermal energy has been well recognized as an advanced green hydrogen generation technology. Creating a high enough temperature in the solar receiver relies on very high solar concentration ratio. Through the development of special heliostats and solar concentration technology, high heat flux of over 3000 suns could be achieved. Each specially designed heliostat creates a solar disc image of small area, and overlapping images make possible temperatures of up to 1500 oC in the solar receiver. In this work, special solar receiving chambers are configured to accommodate reduction reaction and oxidation reaction reciprocally to satisfy the demand of temperatures and gas environments for the different reactions. Analysis of the redox material temperature variation in transient processes of reaction is carried out to understand the dynamics of temperature control for thermochemical reactions.
Concentrated solar power with a field of heliostats has the potential to reach temperatures as high as 1500C, as required for industrial processes. We plan to accomplish this using heliostats on target-oriented mounts, with a mirror surfaces whose toroidal shape is changed throughout the day to maintain a focused disc images of the sun on a receiver. We have built a simple mechanism that deforms a rectangular mirror without the expense of dedicated motors or computer control. The heliostat’s slewbearing has a dual function of orienting the reflector to direct sunlight to the tower and also twisting the mirror shape.
After a brief historical outline of architecture embracing solar issues and the emergence of PLEA (Passive and Low Energy Architecture) International, the most recent three annual conferences of this group are reviewed: 1999 in Brisbane (Aus), 2000 in Cambridge (UK) and 2001 in Florianopolis (Brazil). The most significant change appears to be the broadening of the area of discourse: from the narrow topic of solar energy applications in buildings to environmental sustainability. Four major issues arise from these conferences and most of the chapter is devoted to the discussion of these: the definition and interpretation of sustainability, including resources, social and economic aspects, information and educational questions, the development and use of design tools, finally the stick-and-carrot' tactics of regulations versus persuasion.
Dessicant cooling has the ability to provide efficient indoor humidity and temperature control, while at the same time reducing the electrical energy requirement as compared to conventional vapor compression systems. Unlike other surveys on dessicant cooling, this review focuses on a more detailed coverage of liquid dessicant systems. Physical properties are compared for commonly used liquid dessicants (salt solutions and triethylene glycol). Findings from studies considering dessicant/air contact equipement such as packed towers, finned coils, and solar collector regenerators have been summarized in tables for easy comparison. Key features of these tables include the dessicant material, the influence of design variables on the dehumidifier/regenerator performance, and whether experiments were performed. Finally, system configurations are presented schematically, with additional information listed in tabular form
Solar thermal power is produced by three types of concentrating systems, which utilize parabolic troughs, dishes, and heliostats as the solar concentrators. These systems are at various levels of development and commercialization in the United States and in Europe. The U.S. Industry is currently developing these systems for export at the end of this century and at the beginning of the next one for remote power, village electrification, and grid-connected power. U.S. utilities are not forecasting to need power generation capacity until the middle of the first decade of the 21{sup st} century. At that time, solar thermal electric power systems should be cost competitive with conventional power generation in some unique U.S. markets. In this paper, the authors describe the current status of the development of trough electric, dish/engine, and power tower solar generation systems. 46 refs., 20 figs., 8 tabs.
Using the principles and techniques of non-imaging optics, solar concentrations that approach the theoretical maximum can be achieved. In this paper, the authors review recent progress in attaining, measuring, and using such ultrahigh solar fluxes. In particular, they review the design principles for optimized two-stage concentrators and solar furnaces and discuss the characteristics and properties of a variety of non-imaging secondaries which have been employed. These include Compound Parabolic Concentrators (CPC) type secondaries, Dielectric Totally Internally Reflecting Concentrators (DTIRC), and flow-line or {open_quotes}trumpet{close_quotes} concentrators. The usual design is a configuration where {phi}, the rim angle of the primary, is small, that is, corresponding to a system with a relatively large focal length to diameter (F/D) ratio. All three types of secondary are characterized by a design acceptance angle {phi}{sub a} which must be greater than or equal to {phi}. The design parameters and trade-offs for each of these systems including strategies for choice of particular secondary and degree of truncation, are presented. The authors review the calorimetric techniques used to measure these high intensities and describe a newly developed technique for {open_quotes}extracting{close_quotes} light from inside a high index medium. Finally they review a number of potential applications for highly concentratedmore » solar energy and the current status of the associated technology. By making possible new and unique applications for intense solar flux, these techniques have opened a whole new frontier for research and development of potential economic uses of solar energy. 63 refs., 34 figs., 3 tabs.« less
This paper presents the findings of the first of a periodic survey of photovoltaic power systems and applications in the electric utility sector in selected member countries of the International Energy Agency (IEA). The paper is a modification of a report prepared by the author for the IEA Photovoltaic Power Systems Program. It presents the market and business situation as of 1993, summarizes the commercial and prototype photovoltaic power systems installed at that time, describes the demonstration and field test systems as of the end of 1993 and describes the non-technical factors that affect the use of photovoltaic power systems in the utility sector. This paper covered 1992 and 1993, using data that became available in 1994. A second paper has been requested that will cover the period 1994 and 1995 and will be published in the next Volume. 34 figs., 21 tabs.
In the past electric utilities consisted of generation plants, transmission and distribution networks, the supporting infrastructure, business, and sales operations. Power demanded at one end was met by electricity produced at large plants at the other end. The lowest cost service was generally provided by very large central power plants, or large hydroelectric facilities. Economies of scale in both had long since been reached, and environmental considerations preclude the development of further large scale hydroelectric facilities within the United States. Most of the emerging non-hydro renewable energy technologies used for electricity production today are now less costly than nuclear. However, they still appear to be more costly than the competing fossil fuel resources when evaluated in this central station model. According to conventional utility costs tests they are also less suited to large, central applications, because of their inherently diffuse and local nature. In the 1990s entirely different approaches to evaluating the benefits of renewable energy resources from both the societal and utility perspectives began to emerge, and to be tested in actual applications, spurred by the widespread adoption of integrated resource planning (IRP). Large scale utility applications of wind, solar, geothermal and biomass were also producing important historical cost data, and driving costs down. At the same time the emerging distributed utility model began to show the value of dispersed applications of smaller and more localized energy sources, closer and better adapted to their end uses. The results of these analyses now stimulate the acceleration of the commercialization of utility-scale renewables. But the remaining barriers which selectively disadvantage the renewables are still formidable. And, in the mid 90s, the national fervor to restructure the electric utilities swept the country, forcing utility economics to retreat from IRP-based long term value analysis to short term price, and to replace public service frameworks for decision making with competitive comparisons. This quickly brought the large scale renewable energy applications in the United States almost to a standstill, a situation that remains at the time of this writing (1996). This article provides a review of the economics of the sustained orderly development of renewables, and of distributed utility economics from the standpoint of renewable resource applications. Actual examples are presented and discussed. Also presented are examples of external economic returns, such as quantifying the important economic and job development attributes of the renewables, benefits which heretofore have been absent from energy resource decisions. Specific state valuations and actual both potential applications of the results of these kinds of analyses are discussed. The article concludes with policy recommendations of the necessary conditions to revitalize renewable energy resource commercialization, and to assume a permanent and important role in economic development, within the rapidly changing electricity industry.
The world is on a path that is not sustainable. Ahead is our rapidly expanding energy needs, a fundamental component of development; behind this follows environmental destruction a consequence of the very energy system that brought us to this point. The necessity for a transition from a $8 trillion fossil fuel-based infrastructure to a sustainable energy approach, the speed by which this transition can take place, and the strategies to accomplish this transition, are the topics of this paper. 54 refs., 4 figs., 9 tabs.
This paper provides an overview of the emerging technology of remote, stand-alone electrical power systems featuring a renewable source (wind or photovoltaics [PV]) as well as a diesel generator, with or without an energy storage device. Other stand-alone power systems are discussed briefly, mainly to emphasize the domain of hybrid systems. The history of hybrid systems is reviewed, beginning with the first wind/diesel system in the late 1970s. Other topics include issues arising from the characteristics of diesel engine/generator sets; simple vs. complex systems; the various energy storage technologies that have been used or proposed; control strategies; modeling; optimization; and some {open_quotes}nuts & bolts{close_quotes} details. The bibliography includes over 130 references which are cited throughout the topical discussions. It is concluded that the technical feasibility of hybrid systems has been demonstrated through many prototype installations, and that areas for further improvements include higher reliability and more economical energy storage devices. 139 refs., 7 figs., 1 tab.
The energy pay-back time of crystalline silicon PV-modules varies from 2.58 (multi c-Si) and 2.66 (mono c-Si) years for the sunbelt region to 4.92 (multi c-Si) and 5.07 (mono c-Si) years for continental climate, high latitude regions in the state-of-the-art production technology. It varies from 1.40 (sunbelt) to 2.67 (continental climate, high latitude) years for a medium term projected scenario based on thinner wafers and better material yields, higher efficiencies and frameless modules. In the long term for efficiencies of 20%, pay-back times are reduced to 1.22 and 2.33 years for the corresponding regions. Pay-back times obtained in this study are rather conservative because the kWh-content of semiconductor grade silicon is accounted for in full. A sensitivity analysis shows that a reduction of the kWh-content of semiconductor grade Si with nearly 50%, results in a 30-40% reduction in pay-back times in all scenarios: for the actual scenario, energy payback time would go down to 1.63 (multi c-Si) or 1.74 (mono c-Si) years for the sunbelt region and 3.12 (multi c-Si) or 3.33 (mono c-Si) years for continental climate, high latitude regions. For the medium term projection, these figures would even go down further to about 0.9 years for the sunbeltmore » region and about 1.7 years for continental climate, high latitude regions. Considering semiconductor grade as waste material from the electronic industry (as is currently utilized) with no accountable kWh-content even reduces the pay-back times by 70-85%: for the actual scenario, the energy payback time would decrease to 0.51 (multi c-Si) or 0.65 (mono c-Si) years for continential climate, high latitude regions. For the medium term these figures would decrease further to around 0.3 years (4 months) for the sunbelt region and around 0.5-0.6 years (6-7 months) for continental climate, high latitude regions. 25 refs., 8 figs., 13 tabs.« less
The electric utility industry is in a period of dynamic change. Many forces are impacting this change that utility companies and regulators have little control over. One of the key forces is that of technological development. The authors have seen the dramatic changes that technology has brought to the telecommunications industry. These developments were beyond the control of the existing industries and drove the changes in regulation and provided opportunities for economic development. Renewable energy technologies are a fundamental element to the changing utility framework. Since the characteristics of these new technologies have different attributes than traditional technologies, this necessitates new analytical approaches so that these new technologies can be fully utilized. 48 refs., 19 figs., 1 tab.
Utility planning models evaluate alternative resource options using engineering oriented, discounted-cash-flow (DCF) methodologies to find least-cost options. Although DCF has been widely used for decades, recent capital budgeting experience in manufacturing suggests that more sophisticated procedures are required for comparing passive, capital intensive solar technologies to expense-intensive fossil generation. DCF techniques, which ignore financial risk, have a dismal record for correctly valuing new manufacturing process technologies such as robotics and computer-integrated manufacturing, in part because the benefits cannot be easily measured using traditional accounting concepts. This paper illustrates the application of capital-market theory to the valuation of conventional fossil resources as well as photovoltaics (PV). The paper also explores the importance of technological progress and critically examines the widespread practice of evaluating energy technologies on the basis of their levelized costs. 73 refs., 16 figs., 18 tabs.
Hawaii`s extensive renewable resources, limited access to conventional fuels, and its isolated electrical grids all combine to provide an opportunity to clearly observe the development and implementation of renewable energy processes, technologies, and materials. Hawaii is distinctive in its electrical power usage since it is an island chain with isolated grid systems that range in size from less than 5 Megawatts to over 1.5 Gigawatts and also has many off grid dwellings and at least one isolated village system. However, it has been noted that lessons learned from Hawaii`s early experiences in trying to utilize renewable energy have a great deal in common with problems encountered by mainland utilities trying to do the same thing. Furthermore, conditions in Hawaii are very similar to those in many tropical and semitropical locations in the Pacific and Southeast Asia. Hence, Hawaii`s renewable energy experience is shared here in the hope that it may prove useful to others. This review is the second part of a two part series that describes the progress of renewable energy in the state of Hawaii. The steps taken in Hawaii with regards to ocean thermal energy conversion (OTEC), wave energy, photovoltaics (PV), solar thermal water heating, hydroelectric, andmore » geothermal technologies over the past 20 years are reviewed. Conclusions drawn from Hawaii`s renewable energy experience are summarized in a list of lessons learned that are provided for the interest of those who may be carrying out similar efforts in other locations. 64 refs., 3 figs., 7 tabs.« less
