Showing papers on "Solar power published in 2009"

Organic tandem solar cells: A review

Abstract: In this article some brief theoretical considerations addressing the potential of single and tandem solar cells, the main experimental achievements reported in the literature so far and finally some design rules for efficient material combinations in bulk-heterojunction organic tandem solar cells are presented.

Irradiance Forecasting for the Power Prediction of Grid-Connected Photovoltaic Systems

Abstract: The contribution of power production by photovoltaic (PV) systems to the electricity supply is constantly increasing. An efficient use of the fluctuating solar power production will highly benefit from forecast information on the expected power production. This forecast information is necessary for the management of the electricity grids and for solar energy trading. This paper presents an approach to predict regional PV power output based on forecasts up to three days ahead provided by the European Centre for Medium-Range Weather Forecasts (ECMWF). Focus of the paper is the description and evaluation of the approach of irradiance forecasting, which is the basis for PV power prediction. One day-ahead irradiance forecasts for single stations in Germany show a rRMSE of 36%. For regional forecasts, forecast accuracy is increasing in dependency on the size of the region. For the complete area of Germany, the rRMSE amounts to 13%. Besides the forecast accuracy, also the specification of the forecast uncertainty is an important issue for an effective application. We present and evaluate an approach to derive weather specific prediction intervals for irradiance forecasts. The accuracy of PV power prediction is investigated in a case study.

Prediction and management in energy harvested wireless sensor nodes

Abstract: Solar panels are frequently used in wireless sensor nodes because they can theoretically provide quite a bit of harvested energy. However, they are not a reliable, consistent source of energy because of the Sun's cycles and the everchanging weather conditions. Thus, in this paper we present a fast, efficient and reliable solar prediction algorithm, namely, Weather-Conditioned Moving Average (WCMA) that is capable of exploiting the solar energy more efficiently than state-of-the-art energy prediction algorithms (e.g. Exponential Weighted Moving Average EWMA). In particular, WCMA is able to effectively take into account both the current and past-days weather conditions, obtaining a relative mean error of only 10%. When coupled with energy management algorithm, it can achieve gains of more than 90% in energy utilization with respect to EWMA under the real working conditions of the Shimmer node, an active sensing platform for structural health monitoring.

Efficiency Enhancement of GaAs Photovoltaics Employing Antireflective Indium Tin Oxide Nanocolumns

Abstract: Global-warming issues coupled with high oil prices have become a major driving force for the use of advanced solar power technology, where a key component lies in the development of high-efficiency and low-cost photovoltaic cells. Next generation photovoltaics, hence, demand an efficiency-boosting mechanism in order to render solar energy cost competitive with conventional sources of electricity. Fundamentally, the conversion efficiency of a solar cell depends on the photon absorption, carrier separation, and carrier collection. Therefore, an effective antireflection (AR) coating, minimized recombination loss, and good Ohmic contacts are particularly important. Metal grids that inevitably block the transmission of solar energy also require optimization in order to reduce the series resistance. The trade-off between the electrode and the AR coating areas is one of the efficiency-limiting factors in a conventional solar cell. The conventional AR coating is usually composed of a quarter wavelength stack of dielectrics with different refractive indices. Broad angular and spectral AR is achievable at the price of multiple layers. Over the past few years, versatile subwavelength structures (SWS) have emerged as promising candidates for AR coatings, due to the characteristics of zero-order gratings, or the so-called moth-eye effects. However, the fabrication costs, which involve either electron-beam (e-beam) lithography or various etching processes, can be significant. In addition, the resulting surface-recombination loss due to dry or wet etching could further hinder the applications of SWS in commercial solar cells. Recently, multiple studies have been carried out on indium tin oxide (ITO), titanium dioxide (TiO2), and silicon dioxide (SiO2) nanostructures employing oblique-angle deposition methods, where the refractive indices of the nanoporous materials can be engineered by adjusting the air volume ratio. Still, thematerials requiremultiple layers to effectively suppress the Fresnel reflection.

Global Potential of Concentrating Solar Power

Abstract: The paper presents an analysis of the technical potential of concentrating solar power (CSP) on a global scale elaborated within the European project REACCESS. The analysis is based on the annual direct normal irradiation data (DNI) provided by NASA Surface Meteorology and Solar Energy program (SSE) Version 6.0. The solar resource data has been uploaded to a geographic information system and processed together with spatial data on land use, topography, hydrology, geomorphology, infrastructure, protected areas etc. excluding sites that are not technically feasible for the construction of concentrating solar power plants. The result yields a global map of DNI on land area that is potentially suited for the placement of CSP plants. This map has been analyzed statistically using a simple CSP performance model that takes contemporary parabolic trough technology as reference to determine the potential of solar electricity generation for different classes of annual DNI intensity ranging from 2000 to 2800 kWh/m²/y. The paper describes the assessment methodology and the technical and economic CSP model, and shows the results of this analysis for the different world regions.

Air Emissions Due To Wind And Solar Power

Abstract: Renewables portfolio standards (RPS) encourage large-scale deployment of wind and solar electric power. Their power output varies rapidly, even when several sites are added together. In many locations, natural gas generators are the lowest cost resource available to compensate for this variability, and must ramp up and down quickly to keep the grid stable, affecting their emissions of NOx and CO2. We model a wind or solar photovoltaic plus gas system using measured 1-min time-resolved emissions and heat rate data from two types of natural gas generators, and power data from four wind plants and one solar plant. Over a wide range of renewable penetration, we find CO2 emissions achieve ∼80% of the emissions reductions expected if the power fluctuations caused no additional emissions. Using steam injection, gas generators achieve only 30−50% of expected NOx emissions reductions, and with dry control NOx emissions increase substantially. We quantify the interaction between state RPSs and NOx constraints, find...

Solar-driven desalination with reverse osmosis: the state of the art

Abstract: Solar-driven reverse osmosis desalination can potentially break the dependence of conventional desalination on fossil fuels, reduce operational costs, and improve environmental sustainability. The experience with solar desalination is investigated based on the analysis of 79 experimental and design systems worldwide. Our results show that photovoltaic-powered reverse osmosis is technically mature and — at unit costs as low as 2–3 US$ m –3 — economically cost-competitive with other water supply sources for small-scale systems in remote areas. Under favourable conditions, hybrid systems with additional renewable or conventional power sources perform as good as or better than photovoltaic-powered reverse osmosis. We suggest that in the short-term, solar RO desalination will gain shares in the market of small-scale desalination in remote areas. Concentrating solar power technologies have the highest potential in the medium-term for breakthrough developments in large-scale solar desalination.

Systems for highly efficient solar power conversion

Abstract: A high efficiency photovoltaic DC-DC converter achieves solar power conversion from high voltage, highly varying photovoltaic power sources to harvest maximum power from a solar source or strings of panels for DC or AC use, perhaps for transfer to a power grid at high power levels with coordinated control possible for various elements. Photovoltaic DC-DC converters can achieve efficiencies in conversion that are extraordinarily high compared to traditional through substantially power isomorphic photovoltaic DC-DC power conversion capability that can achieve 97%, 98%, 99.2% efficiency, or even only wire transmission losses. Switchmode impedance or voltage conversion circuit embodiments may have pairs of photovoltaic power interrupt switch elements and pairs of photovoltaic power shunt switch elements to first increase voltage and then decrease voltage as part of the desired photovoltaic DC-DC power conversion.

Future of renewable energies in Iran

Abstract: The activities in field of renewable energy in Iran are focused on scientific and research aspects, and research part is aimed at reduction of capital required for exploitation of related resources. The second step is to work research results into scientific dimension of this field for practical means, i.e. establishing electricity power plants. Due to recent advancements in wind energy, many investors in the country have become interested in investing in this type of energy. At the moment, projects assuming 130 MW of wind power plants are underway, of which, 25 MW is operational. Based on the planning in the 4th Socioeconomic and Cultural Development Plan (2005–2010), private sector is expected to have a share of at least 270 MW in renewable energies. However, it is the government's duty to take the first step for investment in biomass and solar power plants; private sector may then play its part once the infrastructures to this end are laid out. At the moment, a 250 kW plant is under construction in Shiraz and two more geothermal units with 5 and 50 MW capacities will follow. Moreover, two biomass and solar energy plants, standing at 10 and 17 MW, respectively, are of other upcoming projects. The project of Iran's renewable energy, aims to accelerate the sustainable development of wind energy through investment and removal of barriers. This preparatory project is funded by the global environment facility (GEF) and will provide for a number of international and national consultant missions and studies. Once the studies are concluded, a project to develop 25 MW of wind energy in the Manjil region of Gilan will be prepared. It will be consistent with the national development frameworks and objectives and form part of 100 MW of wind-powered energy, which is expected to be developed under the government's third 5-year national development plan (started 21 March 2000).

Solar and wind opportunities for water desalination in the Arab regions

Abstract: Despite the abundance of renewable energy resources in the Arab region, the use of solar thermal, solar photovoltaics, and wind is still in its technological and economic infancy. Great potential exists, but economic constraints have impeded more rapid growth for many applications. These technologies have certainly advanced technically over the last quarter century to the point where they should now be considered clean-energy alternatives to fossil fuels. For the Arab countries and many other regions of the world, potable water is becoming as critical a commodity as electricity. As renewable energy technologies advance and environmental concerns rise, these technologies are becoming more interesting partners for powering water desalination projects. We evaluate the current potential and viability of solar and wind, emphasizing the strict mandate for accurate, reliable site-specific resource data. Water desalination can be achieved through either thermal energy (using phase-change processes) or electricity (driving membrane processes), and these sources are best matched to the particular desalination technology. Desalination using solar thermal can be accomplished by multistage flash distillation, multi-effect distillation, vapor compression, freeze separation, and solar still methods. Concentrating solar power offers the best match to large-scale plants that require both high-temperature fluids and electricity. Solar and wind electricity can be effective energy sources for reverse osmosis, electrodialysis, and ultra- and nano-filtration. All these water desalination processes have special operational and high energy requirements that put additional requisites on the use of solar and wind to power these applications. We summarize the characteristics of the various desalination technologies. The effective match of solar thermal, solar photovoltaics, and wind to each of these is discussed in detail. An economic analysis is provided that incorporates energy consumption, water production levels, and environmental benefits in its model. Finally, the expected evolution of the renewable technologies over the near- to mid-term is discussed with the implications for desalination applications over these timeframes.

Benchmarking of different approaches to forecast solar irradiance

Abstract: Power generation from photovoltaic systems is highly variable due to its dependence on meteorological conditions An efficient use of this fluctuating energy source requires reliable forecast information for management and operation strategies Due to the strong increase of solar power generation the prediction of solar yields becomes more and more important As a consequence, in the last years various research organisations and companies have developed different methods to forecast irradiance as a basis for respective power forecasts For the end-users of these forecasts it is important that standardized methodology is used when presenting results on the accuracy of a prediction model in order to get a clear idea on the advantages of a specific approach In this paper we introduce a benchmarking procedure to asses the accuracy of irradiance forecasts and compare different approaches of forecasting The evaluation shows a strong dependence of the forecast accuracy on the climatic conditions For Central European stations the relative rmse ranges from 40 % to 60 %, for Spanish stations relative rmse values are in the range of 20 % to 35 %

Development Trends and Economics of Innovative Solar Power Generation Technologies: A Comparative Analysis

Abstract: In this paper we compare development trends, economics and financial risks of alternative large-scale solar power generation technologies (parabolic trough, solar tower, and three different photovoltaic technologies). In particular, a number of European countries, Algeria and the US promote solar power generation. In oure study, we investigate the economic viability of the solar trough projects Andasol-I (Spain), Nevada Solar One (US), the solar tower projects PS-10 and Solar Tres (Spain), and the three PV projects Solarpark Waldpolenz (Germany), Parque Solar Beneixama (Spain) and Nellis Solar Power Plant (US). To this end, we employ a battery of economic indicators, such as net present value (NPV), return on investment (ROI), alternative discount rate (ADR), and amortization time (Ta), and also perform a detailed sensitivity analysis. We find that, in the absence of subsidization, current solar technologies cannot compete with conventional power plant technologies. Overall, we conclude that for realizing the Europe-Middle East-North Africa (EUMENA) Mediterranean ring connection, more research and development is needed on solar power generation technologies for making them sufficiently attractive on economic grounds.

Glasses for solar energy conversion systems

Abstract: Solar technologies are projected to increase tremendously over the next 10 years. Glasses are playing an important role as transparent materials of photovoltaic (PV) cells and concentrating solar power (CSP) systems. Glasses are materials of short energy payback time and environmental compatibility suitable for sustainable energy concepts. The paper reviews recent solar applications. Surface structuring and coating of glasses are shown to improve energy efficiency for solar conversion systems substantially. Encapsulated glass-to-glass PV modules and solar photocatalytic glass surfaces are identified as elements of a green architecture combining renewable power generating and destruction of air pollutants of urban environments. Emerging solar technologies for power generation, including transparent PV modules, solar chimney and thermoelectric systems may become significant areas of future solar glass applications.

Personalized Energy: The Home as a Solar Power Station and Solar Gas Station

Abstract: Point-of-use solar energy would generate the exact amount of energy any one individual needs, at the location where it is needed. Such a means of energy supply would create a revolution in society's approach to energy use, and allow a more level playing field for all. This Viewpoint considers some of the key enablers for this technology.

Design of a Solar Power Management System for an Experimental UAV

Abstract: The design of a solar power management system (SPMS) for an experimental unmanned aerial vehicle (UAV) is summarized. The system will provide power required for the on-board electronic systems on the UAV. The power management system mainly consists of the maximum power point tracking (MPPT), the battery management, and the power conversion stages. The MPPT stage attempts to obtain the maximum power available from the solar cell panels. The battery management stage monitors and controls the charge and discharge processes of the Li-ion polymer battery modules. The last stage is for power conversion that consists of dc/dc synchronous buck converters to generate +5 V and +12 V powers for the on-board computers and other electronic circuitries.

Economic analysis of power generation from floating solar chimney power plant

Abstract: Solar chimney thermal power technology that has a long life span is a promising large-scale solar power generating technology. This paper performs economic analysis of power generation from floating solar chimney power plant (FSCPP) by analyzing cash flows during the whole service period of a 100 MW plant. Cash flows are influenced by many factors including investment, operation and maintenance cost, life span, payback period, inflation rate, minimum attractive rate of return, non-returnable subsidy rate, interest rate of loans, sale price of electricity, income tax rate and whether additional revenue generated by carbon credits is included or not. Financial incentives and additional revenue generated by carbon credits can accelerate the development of the FSCPP. Sensitivity analysis to examine the effects of the factors on cash flows of a 100 MW FSCPP is performed in detail. The results show that the minimum price for obtaining minimum attractive rate of return (MARR) of 8% reaches 0.83 yuan (kWh)−1 under financial incentives including loans at a low interest rate of 2% and free income tax. Comparisons of economics of the FSCPP and reinforced concrete solar chimney power plant or solar photovoltaic plant are also performed by analyzing their cash flows. It is concluded that FSCPP is in reality more economical than reinforced concrete solar chimney power plant (RCSCPP) or solar photovoltaic plant (SPVP) with the same power capacity.

Aesthetic impact assessment of solar power plants : An objective and a subjective approach

Abstract: Solar energy for the production of electric energy is one source of renewable energy which is experiencing most development in recent years. In countries with high solar radiation indices, as is the case of Spain, expectations of installation of large solar power plants are increasing. Most solar power plants are located in rural environments, where the landscape has remained practically unaltered ever since extensive agriculture was introduced. Because of this, one of the most significant environmental impacts of this type of installation is the visual impact derived from the alteration of the landscape. In this work, an indicator is proposed for the quantification of the objective aesthetic impact, based on four criteria: visibility, colour, fractality and concurrence between fixed and mobile panels. The relative importance of each variable and the corresponding value functions are calculated using expert contribution. A study of the subjective aesthetic impact is then carried out using the semantic differential method, to obtain the perception of a sample of individuals of the initial landscapes and of the landscapes altered through the installation of a solar power plant. The indicator and the study of public perception are applied to five real solar power plants, to test their reliability. Subsequently, a different group of individuals is used to determine preferences between the five solar power plants. The study proves that the combined use of objective indicator and subjective study, faithfully explains user preferences corresponding to the combined comparisons of the five cases. It is concluded that the tools proposed for the evaluation of the aesthetic impact of solar power plants are useful for the selection of optimal plant location and most adequate use of panel technology, to minimise aesthetic impact.

Situation and outlook of solar energy utilization in Tibet, China

Abstract: The near-exponential rise in tourist numbers and accelerating economic growth have challenged Tibetan energy supply and threaten its peculiar environment and valuable ecosystem. Exploitation of pollution free solar power may medicate this demand for energy. Here we shall provide a review of solar power development in Tibet. This region has a near inexhaustible source of solar energy due to its average annual radiation intensity of 6000–8000 MJ/m2, ranking it first in China and second after the Sahara worldwide. Currently, Tibet has 400 photovoltaic power stations with a total capacity of nearly 9 MW. In addition, 260,000 solar energy stoves, passive solar house heating covering 3 million square meters, and 400,000 m2 of passive solar water heaters are currently in use in Tibet. Although Tibet places first in applying solar energy in China, solar energy faces big challenges from hydroelectric power and the absence of local know-how. The new power generation capacity in Tibet's “11th Five-Year (2006–2010)” Plan focuses primarily on hydropower, PV power stations being relegated to a secondary role as supplementary to hydropower. Here it will be argued that this emphasis is incorrect and that solar energy should take first place in Tibet's energy development, as it is crucial in striving for a balance between economic development, booming tourism, and environmental protection.

Portable devices having multiple power interfaces

Abstract: Portable devices having multiple power interfaces are described herein. According to one embodiment of the invention, a portable electronic device includes, but is not limited to, a processor, a memory coupled to the processor for storing instructions, when executed from the memory, cause the processor to perform one or more functions, a battery coupled to provide power to the processor and the memory, and a battery charging manager coupled to charge the battery using power derived from a plurality of power sources including a solar power source. Other methods and apparatuses are also described.

Algorithms for harvested energy prediction in batteryless wireless sensor networks

Abstract: Several wireless sensor network (WSN) applications leverage energy harvesting technologies such as small size photo-voltaic modules. The advantage of solar energy over other forms of environmental energy is that the available solar power can be predicted with reasonable accuracy allowing the implementation of efficient power management techniques. However accurate predictions of future energy profiles can be expensive in term of memory occupancy and complexity and a trade-off between accuracy and computational effort must be evaluated. In this paper we compare different solar energy prediction algorithms that give estimates future available energy over the time. They are computationally simple and have a small memory footprint to facilitate the implementation in resource limited solar harvesting sensor nodes. Simulation results show that the most effective predictors is possible achieve high accuracy, diverging from real energy profile by less than 10%.

Concentrating-Solar Biomass Gasification Process for a 3rd Generation Biofuel

Abstract: A new concept of producing synfuel from biomass using concentrating solar energy as its main energy source is proposed in this paper. The aim of the concept is to obtain an easy to handle fuel with near-zero CO2 emission and reduced land-use requirements compared to first and second generation biofuels. The concept’s key feature is the use of high-temperature heat from a solar concentrating tower to drive the chemical process of converting biomass to a biofuel, obtaining a near-complete utilization of carbon atoms in the biomass. H2 from water electrolysis with solar power is used for reverse water gas shift to avoid producing CO2 during the process. In a chemical process simulation, we compare the solar biofuel concept with two other advanced synfuel concepts: second generation biofuel and coal-to-liquid, both using gasification technology and capture and storage of CO2 generated in the fuel production. The solar-driven third generation biofuel requires only 33% of the biomass input and 38% of total land...

Fuel and vehicle technology choices for passenger vehicles in achieving stringent CO2 targets: connections between transportation and other energy sectors.

Abstract: The regionalized Global Energy Transition (GET-R 6.0) model has been modified to include a detailed description of light-duty vehicle options and used to investigate the potential impact of carbon capture and storage (CCS) and concentrating solar power (CSP) on cost-effective fuel/vehicle technologies in a carbon-constrained world. Total CO2 emissions were constrained to achieve stabilization at 400-550 ppm, by 2100, at lowest total system cost. The dominant fuel/vehicle technologies varied significantly depending on CO2 constraint, future cost of vehicle technologies, and availability of CCS and CSP. For many cases, no one technology dominated on a global scale. CCS provides relatively inexpensive low-CO2 electricity and heat which prolongs the use of traditional ICEVs. CSP displaces fossil fuel derived electricity, prolongs the use of traditional ICEVs, and promotes electrification of passenger vehicles. In all cases considered, CCS and CSP availability had a major impact on the lowest cost fuel/vehicle technologies, and alternative fuels are needed in response to expected dwindling oil and natural gas supply potential by the end of the century.

Optimal Design of a Molten Salt Thermal Storage Tank for Parabolic Trough Solar Power Plants

Abstract: This paper presents an optimal design procedure for internally insulated, carbon steel, molten salt thermal storage tanks for parabolic trough solar power plants. The exact size of the vessel and insulation layers and the shape of the roof are optimized by minimizing the total investment cost of the storage system under three technical constraints: remaining within the maximum allowable values of both temperature and stress in the steel structure, and avoiding excessive cooling and consequent solidification of the molten salt during long periods of no solar input. The thermal, mechanical and economic aspects have been integrated into an iterative step-by-step optimization procedure, which is shown to be effective through application to the case study of a 600 MW h thermal storage system. The optimal design turns out to be an internally insulated, carbon steel storage tank characterized by a maximum allowable height of 11 m and a diameter of 22.4 m. The total investment cost is about 20% lower than that of a corresponding AISI 321H stainless steel storage tank without internal protection or insulation.

Photovoltaics Power Up

Abstract: The global photovoltaic (PV) power industry is experiencing dramatic technology advances and market growth. Over the past 20 years, manufacturing output has grown by a factor of 200, reaching 5 gigawatts (GW) in 2008. The total accumulated installed capacity is now around 15 GW. This is quite small relative to the world's 4000 GW of installed electric generation capacity—just 0.375% to be precise. However, industry leaders expect similar rapid growth over the coming years, with PV generation a major contributor to power generation 20 years hence ([ 1 ][1]). In this quickly evolving environment, investors must assess which technologies and companies are best positioned, policy-makers must assess what role PV generation should play in our energy mix, utility planners must assess the impacts this will have on the electric grid, government and industry must decide how to allocate research and development (R&D) funds, and citizens must sort through a barrage of conflicting messages. For example, a recent Wall Street Journal opinion editorial article states, “There's an unavoidable problem with renewable-energy technologies: From an economic standpoint, they're big losers” ([ 2 ][2]). Perhaps this was once true when the industry was so small that it didn't matter anyway. But in many cases it is no longer true today. ![Figure][3] Measuring up. Levelized cost of energy by resource for new generation constructed in the 2009 to 2012 time frame. Prices include the 30% U.S. federal investment tax credit for renewables. PV is a viable utility option, with its competitiveness only expected to increase as PV costs decrease and gas prices rise. [Source: Lazard Capital Markets, 1/9/09] Driven by advances in technology and increases in manufacturing scale and sophistication, the cost of PV has declined at a steady rate since the first solar cells were manufactured ([ 3 ][4]). For example, in 2000, solar cells typically used 15 g of expensive, highly refined silicon to generate 1 W of power. By comparison, SunPower Corporation's modules currently use only 5.6 g/W. Today, the manufacturing cost of standard crystalline silicon modules produced in a state-of-the-art facility is around $1.40/W ([ 4 ][5]). This cost includes the cost of refining silicon but not the added gross margin in sales price. Manufacturers foresee manufacturing cost to fall to $1/W within 5 years. An upshot of these cost reductions is that the levelized cost of energy (LCOE) for PV plants (see the figure) is now in the range of conventional generation options when taking into account the impact of the U.S. federal 30% investment tax credit, and will be fully competitive without that incentive in 5 years. Perhaps surprisingly, PV electricity today costs less than that from a new natural gas peaking plant, and is rapidly encroaching on combined cycle base-load generation costs. From the perspective of an electric utility, what counts in making new generation decisions is the cost of electricity from the new plant. That their customers might pay a lower cost due to older, lower-cost generation in the mix (such as from hydroelectric or coal plants) is irrelevant when more capacity is needed. This fact has contributed to the recent increase in interest in PV on the part of electric utilities. For example, the California utility Pacific Gas and Electric (PGE for example, the PV industry installed more than 2 GW of PV power plants in Spain during 2008. Construction times for 2 GW of conventional generation would be 10 to 15 years. PV will thus not be insignificant much longer. Conventional crystalline silicon modules compete with emerging thin-film technologies. Leading thin-film producers have lower cost, but at lower module energy conversion efficiency. The lower efficiency results in higher installation cost, with the result that there is near cost parity at the installed-system level. Indeed, there is a spectrum of technologies—from higher-performance, higher-cost modules to lower-performance, roll-on thin films—all competing successfully. Crystalline silicon modules are capable of attaining the long-term cost targets. Therefore, one should not think of thin-film technologies as somehow disruptive or uniquely enabling for the emergence of large-scale PV. Thin films are rather new technologies that may, if successful, help drive costs lower over time. The competition from crystalline silicon, however, will remain formidable because of the vast R&D resources being deployed. New entrants to the PV industry need to be cognizant of this fact as they allocate their own capital to the field. Our energy future is becoming clearer. PV will not be a panacea, but it will take its place as a major source of energy alongside energy efficiency, other renewables, nuclear, and improved conventional generation, perhaps with carbon sequestration, as we transition to a carbon-free electric grid over the next half century. 1. [↵][7] 1. P. Mints , “Sunny outlook: Predictions for growth in the PV industry,” Renewable Energy World, September 2007 ([www.renewableenergyworld.com/rea/news/article/2007/09/sunny-outlook-predictions-for-growth-in-the-pv-industry-51464][8]). 2. [↵][9] 1. M. Schulz , “Don't count on 'countless' green jobs,” Wall Street Journal, 20 February 2009, p. A15. 3. [↵][10] 1. R. M. Swanson , Prog. Photovolt. Res. Appl. 14, 43 (2006). [OpenUrl][11] 4. [↵][12] Photon International, December 2008, pp. 84–92. 5. [↵][13] PG&E press release, “PG&E signs historic 800 MW photovoltaic solar power agreements with Optisolar and SunPower,” August 2008 ([www.pge.com/about/news/mediarelations/newsreleases/q3_2008/080814.shtml][14]). [1]: #ref-1 [2]: #ref-2 [3]: pending:yes [4]: #ref-3 [5]: #ref-4 [6]: #ref-5 [7]: #xref-ref-1-1 "View reference 1 in text" [8]: http://www.renewableenergyworld.com/rea/news/article/2007/09/sunny-outlook-predictions-for-growth-in-the-pv-industry-51464 [9]: #xref-ref-2-1 "View reference 2 in text" [10]: #xref-ref-3-1 "View reference 3 in text" [11]: {openurl}?query=rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [12]: #xref-ref-4-1 "View reference 4 in text" [13]: #xref-ref-5-1 "View reference 5 in text" [14]: http://www.pge.com/about/news/mediarelations/newsreleases/q3_2008/080814.shtml