Solar Power Facilities Research Articles

New Concentrating Solar Power Facility for Testing High Temperature Concrete Thermal Energy Storage

Abstract Several thermal energy storage (TES) systems have been developed and tested to be integrated in concentrating solar power (CSP) systems. Recent studies show that concrete as storage media has the potential to become an interesting solution due to its properties such as relatively high specific heat and thermal conductivity, good mechanical properties, a thermal expansion coefficient similar to that of steel pipe and low cost of a material that is easy to obtain and process. This article outlines a new 100 kW th solar beam-down facility for testing high temperature concrete storage at 393°C and the first project to use the facility for TES testing in collaboration with NEST. Initial concrete characterization and testing results which show promising thermal and mechanical performance, are also presented. The CSP hot oil-loop has been modified and instrumented to perform research and testing of TES systems in real solar radiation conditions. Experimental TES system testing at real scale with a total storage capacity of 1.0 MWh th is planned to begin operation early 2015.

Design of a Thermochemical Storage System for Air-operated Solar Tower Power Plants

Abstract The present study deals with the mechanical properties of structured reactors/heat exchangers, for high temperature heat storage via the cobalt oxide cyclic redox scheme. Two different structures (i.e. honeycomb and perforated block) and two different compositions (i.e. 100% cobalt oxide and 90 wt% cobalt oxide – 10 wt% aluminium oxide) were evaluated. During thermal cycling in the range of 800-1000 o C, different loads were applied to the sampleswhile monitoring their length variation. The integrity of the samples was assessed after every cycle. It was found that mechanical strength was substantially improvedupon addition of 10 wt% aluminium oxide. The cobalt oxide/alumina composite presented lower maximal expansion during cycling and exhibited higher integrity, already after one thermal cycle. Another important result is that, for both the honeycomb and the perforated block, the load decreases the over-all sample net expansion. Moreover, the perforated block exhibited lower expansion and better mechanical strength as compared to the honeycomb. Due to the better chemical performance expected to be achieved by the honeycomb structure, a compromise between these two structureshas to be chosen (e.g. honeycomb structure with thicker walls). The results are used for building a thermochemical storage system prototype, implemented for the first time in an existing concentrated solar power facility (STJ).

The water impacts of climate change mitigation measures

A variety of proposed activities to mitigate greenhouse gas emissions will impact on scarce water resources, which are coming under increasing pressure in many countries due to population growth and shifting weather patterns. However, the integrated analysis of water and carbon impacts has been given limited attention in greenhouse mitigation planning. In this Australian case study, we analyse a suite of 74 mitigation measures ranked as highest priority by one influential analysis, and we find that they have highly variable consequences for water quantity. We find: (1) The largest impacts result from land-based sequestration, which has the potential to intercept large quantities of water and reduce catchment yields, estimated to exceed 100 Mm3/MtCO2-e of carbon mitigated (100,000 l per tonne CO2-e). (2) Moderate impacts result from some renewable power options, including solar thermal power with a water cost estimated at nearly 4 Mm3/MtCO2-e. However, the water impacts of solar thermal power facilities could be reduced by designing them to use existing power-related water supplies or to use air or salt-water cooling. (3) Wind power, biogas, solar photovoltaics, energy efficiency and operational improvements to existing power sources can reduce water demand through offsetting the water used to cool thermal power generation, with minor savings estimated at 2 Mm3/MtCO2-e and amounting to nearly 100 Mm3 of water saved in Australia per annum in 2020. This integrated analysis significantly changes the attractiveness of some mitigation options, compared to the case where water impacts are not considered.

Optimal coupling of a biomass based polygeneration system with a concentrated solar power facility for the constant production of electricity over a year

In this paper we address the integration of a polygeneration system based on biomass with a concentrated solar power facility for the constant production of electricity over a year long. The process is modelled as a superstructure embedding two different gasification technologies, direct and indirect, and two reforming modes, partial oxidation or steam reforming followed by gas cleaning and three alternatives for the syngas use, water gas shift reactor (WGSR) to produce hydrogen, a furnace for thermal energy production and an open Brayton cycle. We couple this system with a concentrated solar plant that uses tower technology, molten salts and a regenerative Rankine cycle. The problem is formulated as a multi-period mixed-integer non linear programming problem (MINLP). The optimal integration involves the use of indirect gasification, steam reforming and a Brayton cycle to produce 340MW of electricity at 0.073€/kWh and 97kt/yr of hydrogen as a credit.

기후변화를 고려한 농촌지역 그린빌리지의 태양에너지 활용에 관한 경제성 분석

This study aims to perform the economic analysis to the use of solar power facilities in rural villages considering the climate change scenario. IPCC climate change scenarios in the recently adopted the RCP scenarios (RCP8.5, RCP6.5, RCP4.5, RCP2.6) was used. By RCP scenarios, solar radiation, depending on the scenario in 2100, respectively, 3.6%, 2.5%, 1.9%, 1.1% was assumed to increase. From the economic analysis(payback period is 25 year) on 8 points of each province, in all cases of normal data and four RCP scenarios, at all points analyzed were NPV indicate a negative, BC ratio less than 1.0, respectively. In the case of Mokpo, Chunnam RCP8.5, BC ratio were found to be up to a 0.92, followed by 0.89 in the case of RCP8.5 in Jinju, Kyungnam shows, while the minimum was in Jeju. BC ratio is 1.0 or bigger, in order for the normal solar radiation data in Mokpo, Chonnam was the minimum that it takes 37 years. Similarly, in the case of RCP scenarios, 30 years in Mokpo, Chonnam RCP8.5 and 31 years in the cases of Jinju, Kyungnam and Jeonju, Cheonbuk RCP8.5 were analyzed. It was analyzed that RCP8.5 has the highest value. BC analysis models for each of the factors, the results of the sensitivity analysis, the initial installation costs, electricity sales price, discount rate in the order of economy showed higher sensitivity, and the rest factors showed lower changes. Although there are some differences of solar radiation by region, but in Korea most facilities in rural areas, the use of solar power was considered to be economical enough, considering change of several factors with high sensitivity, such as increasing of government subsidies for the solar power installation of the facility, rising oil prices due to a rise in electricity sales price, and a change in discount rate. In particular, when considering climate change scenarios, the use of solar energy for rural areas of the judgment that there was more economical.

Optimal year-round operation of a concentrated solar energy plant in the south of Europe

We present the year-round optimization of the operation of a concentrated solar power facility evaluating the molten salts storage, the power block and cooling. We locate the plant in the south of Europe, Almería (Spain), where high solar radiation is available. The operation of the plant is a function of the solar incidence as well as the climate and atmospheric conditions. The optimization of the system is formulated as a multiperiod Non-linear Programming problem (NLP) that is solved for the optimal production of electricity over a year defining the main operating variables of the thermal and cooling cycles. For a maximum of 25 MW in summer and a minimum of 9.5 MW in winter the annual production cost of electricity is 0.15 €/kWh consuming an average of 2.1 Lwater/kWh. The investment for the plant is 260 M€. Scale-up studies reveal that the production cost can decrease by half while the investment per unit of power should become competitive with current coal based power plants if solar and coal facilities present similar production capacities.

Life Cycle Assessment of a Power Tower Concentrating Solar Plant and the Impacts of Key Design Alternatives

A hybrid life cycle assessment (LCA) is used to evaluate four sustainability metrics over the life cycle of a power tower concentrating solar power (CSP) facility: greenhouse gas (GHG) emissions, water consumption, cumulative energy demand (CED), and energy payback time (EPBT). The reference design is for a dry-cooled, 106 MW(net) power tower facility located near Tucson, AZ that uses a mixture of mined nitrate salts as the heat transfer fluid and storage medium, a two-tank thermal energy storage system designed for six hours of full load-equivalent storage, and receives auxiliary power from the local electric grid. A thermocline-based storage system, synthetically derived salts, and natural gas auxiliary power are evaluated as design alternatives. Over its life cycle, the reference plant is estimated to have GHG emissions of 37 g CO2eq/kWh, consume 1.4 L/kWh of water and 0.49 MJ/kWh of energy, and have an EPBT of 15 months. Using synthetic salts is estimated to increase GHG emissions by 12%, CED by 7%, and water consumption by 4% compared to mined salts. Natural gas auxiliary power results in greater than 10% decreases in GHG emissions, water consumption, and CED. The thermocline design is most advantageous when coupled with the use of synthetic salts.

Life Cycle Assessment of a Parabolic Trough Concentrating Solar Power Plant and the Impacts of Key Design Alternatives

Climate change and water scarcity are important issues for today's power sector. To inform capacity expansion decisions, hybrid life cycle assessment is used to evaluate a reference design of a parabolic trough concentrating solar power (CSP) facility located in Daggett, CA, along four sustainability metrics: life cycle (LC) greenhouse gas (GHG) emissions, water consumption, cumulative energy demand (CED), and energy payback time (EPBT). This wet-cooled, 103 MW plant utilizes mined nitrates salts in its two-tank, thermal energy storage (TES) system. Design alternatives of dry-cooling, a thermocline TES, and synthetically derived nitrate salt are evaluated. During its LC, the reference CSP plant is estimated to emit 26 g of CO(2eq) per kWh, consume 4.7 L/kWh of water, and demand 0.40 MJ(eq)/kWh of energy, resulting in an EPBT of approximately 1 year. The dry-cooled alternative is estimated to reduce LC water consumption by 77% but increase LC GHG emissions and CED by 8%. Synthetic nitrate salts may increase LC GHG emissions by 52% compared to mined. Switching from two-tank to thermocline TES configuration reduces LC GHG emissions, most significantly for plants using synthetically derived nitrate salts. CSP can significantly reduce GHG emissions compared to fossil-fueled generation; however, dry-cooling may be required in many locations to minimize water consumption.

Cloud Formation in the Plumes of Solar Chimney Power Generation Facilities: A Modeling Study

The solar chimney power facility has the potential to become a valuable technology for renewable energy production. Its financial viability depends on a thorough understanding of the processes affecting its performance, particularly because of the large startup costs associated with facility design and construction. This paper describes the potential impacts on plant capacity resulting from cloud formation within or downwind of the solar chimney. Several proposed modifications to the basic concept of the solar chimney power facility have the potential to cause significant additions of water vapor to the air passing through the collector. As the air continues up through and out of the chimney, this excess water can condense to form cloud. This possibility is explored using a cloud parcel model initialized to simulate the range of expected operating conditions for a proposed solar chimney facility in southwestern Australia. A range of temperatures and updraft velocities is simulated for each of four seasonal representations and three levels of water vapor enhancement. Both adiabatic environments and the effects of entrainment are considered. The results indicate that for very high levels of water vapor, enhancement cloud formation within the chimney is likely; at more moderate levels of water vapor enhancement, the likelihood of plume formation is difficult to fully assess as the results depend strongly on the choice of entrainment rate. Finally, the impacts of these outcomes on facility capacity are estimated.

The laser calibration system for the STACEE ground-based gamma ray detector

We describe the design and performance of the laser system used for calibration monitoring of components of the STACEE detector. STACEE is a ground based gamma ray detector which uses the heliostats of a solar power facility to collect and focus Cherenkov light onto a system of secondary optics and photomultiplier tubes. To monitor the gain and check the linearity and timing properties of the phototubes and associated electronics, a system based on a dye laser, neutral density filters and optical fibres has been developed. In this paper we describe the system and present some results from initial tests made with it.

Shadowing of Nonpolluted Locations by Urban Pollution

Abstract Areas of high concentrations of particulates in the urban atmosphere are hypothesized to strongly influence the solar receipt in nearby nonpolluted regions. Reductions of solar radiation in nonpolluted areas by upsun high aerosol regions are computed using a three-dimensional multi-scattering radiation model for specified solar-elevation classes. Numerical simulations from this model indicate that reductions exceeding 10 percent can occur several kilometers downsun of even moderately polluted regions in the early morning (i.e., periods of low solar-elevation angle). Although the reductions in global radiation are quite pronounced in the early day, they are generally overwhelmed in the daily total because of the relatively small amount of radiation associated with low-elevation angles. A series of simulations for three representative latitudes (33°N, 43°N and 53°N) demonstrate that the areal extent of the shadowing is highly dependent on latitude. Reductions in solar radiation exceeding 3 percent occur 15 km down range of the center of pollution for high-latitude (53°N) locations during early-morning, low-elevation angle periods. Such excessive solar attenuation in nonpolluted regions may affect the site selection of solar power facilities, the planning and siting of parks, golf courses and other recreational activities, the migration and tourism trends in areas experiencing seasonal population changes (i.e., the sunbelt states), and the temperature regime of the region.