Techno-economic performance evaluation of solar tower plants with integrated multilayered PCM thermocline thermal energy storage: a comparative study to conventional two-tank storage systems

Copyright 2016 AIP Publishing. This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing.Solar Tower Power Plants with thermal energy storage are a promising technology for dispatchable renewable energy in the near future. Storage integration makes possible to shift the electricity production to more profitable peak hours. Usually two tanks are used to store cold and hot fluids, but this means both higher investment costs and difficulties during the operation of the variable volume tanks. Instead, another solution can be a single tank thermocline storage in a multi-layered configuration. In such tank both latent and sensible fillers are employed to decrease the related cost up to 30% and maintain high efficiencies. This paper analyses a multi-layered solid PCM storage tank concept for solar tower applications, and describes a comprehensive methodology to determine under which market structures such devices can outperform the more conventional two tank storage systems. A detail model of the tank has been developed and introduced in an existing techno-economic tool developed by the authors (DYESOPT). The results show that under current cost estimates and technical limitations the multi-layered solid PCM storage concept is a better solution when peaking operating strategies are desired, as it is the case for the two-tier South African tariff scheme.Peer ReviewedPostprint (published version

Selection and implementation of aerosol data for the prediction of solar resource in United Arab Emirates

International audienceIn deserts, as the sky is often dusty and rarely cloudy, aerosols are the most critical atmospheric parameter for solar resource estimation. High differences between existing aerosol datasets, and low accuracies at solar irradiance estimates in Arabian Peninsula have been reported. This work is a part of a process of developing a tool for irradiance estimation accounting correctly for aerosols. As hourly irradiances are the focus, only intra-day resolved aerosol data are of interest. The paper validates the MACC (re-analysis model) derived aerosol optical depth in United Arab Emirates, discusses its accuracy compared with that of MATCH (chemical transport model), evaluates the potential error on global and direct normal irradiances due to the observed error on aerosol optical depth, and then proposes an algorithm for implementation of MACC partial aerosol optical depths in the libRadTran radiative transfer model

A methodology for determining optimum solar tower plant configurations and operating strategies to maximize profits based on hourly electricity market prices and tariffs

The present study analyzes the influence that market conditions have on determining optimum molten salt solar tower plants with storage that maximizes profits (in terms of plant configuration, sizing, and operation) for a location in South Africa. Three different scenarios based on incentive programs and local wholesale electricity prices are considered. A multi-objective optimization modeling approach was followed, showing the tradeoff curves between minimizing investment and maximizing profits when varying critical size-related parameters (such as nameplate capacity, solar multiple ISM), and storage capacity) together with power-cycle design and operating specifications including dynamic startup curves and different storage dispatchabiliry strategies. Results are shown by means of a comparative analysis between optimal plants found for each scenario, highlighting the value that storage has wider the current two-tier tariff scheme and the relevance of designing a suitable policy for technology development. Finally, a final analysis is performed with regard to the indicators used for economic evaluation of power plants, by comparing the differences between optimum designs found when using the levelized cost of electricity (LCoE) solely as performance indicator instead of cash-flows and profit-based indicators, such as the internal rate of return (IRR).Peer ReviewedPostprint (published version

Techno-economic performance evaluation of solar tower plants with integrated multilayered PCM thermocline thermal energy storage: a comparative study to conventional two-tank storage systems

Solar Tower Power Plants with thermal energy storage are a promising technology for dispatchable renewable energy in the near future. Storage integration makes possible to shift the electricity production to more profitable peak hours. Usually two tanks are used to store cold and hot fluids, but this means both higher investment costs and difficulties during the operation of the variable volume tanks. Instead, another solution can be a single tank thermocline storage in a multi-layered configuration. In such tank both latent and sensible fillers are employed to decrease the related cost up to 30% and maintain high efficiencies. This paper analyses a multi-layered solid PCM storage tank concept for solar tower applications, and describes a comprehensive methodology to determine under which market structures such devices can outperform the more conventional two tank storage systems. A detail model of the tank has been developed and introduced in an existing techno-economic tool developed by the authors (DYESOPT). The results show that under current cost estimates and technical limitations the multi-layered solid PCM storage concept is a better solution when peaking operating strategies are desired, as it is the case for the two-tier South African tariff scheme.Peer Reviewe

Techno-economic performance evaluation of solar tower plants with integrated multilayered PCM thermocline thermal energy storage: a comparative study to conventional two-tank storage systems

Copyright 2016 AIP Publishing. This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing.Solar Tower Power Plants with thermal energy storage are a promising technology for dispatchable renewable energy in the near future. Storage integration makes possible to shift the electricity production to more profitable peak hours. Usually two tanks are used to store cold and hot fluids, but this means both higher investment costs and difficulties during the operation of the variable volume tanks. Instead, another solution can be a single tank thermocline storage in a multi-layered configuration. In such tank both latent and sensible fillers are employed to decrease the related cost up to 30% and maintain high efficiencies. This paper analyses a multi-layered solid PCM storage tank concept for solar tower applications, and describes a comprehensive methodology to determine under which market structures such devices can outperform the more conventional two tank storage systems. A detail model of the tank has been developed and introduced in an existing techno-economic tool developed by the authors (DYESOPT). The results show that under current cost estimates and technical limitations the multi-layered solid PCM storage concept is a better solution when peaking operating strategies are desired, as it is the case for the two-tier South African tariff scheme.Peer Reviewe

On the improvement of MACC aerosol spatial resolution for irradiance estimation in the United Arab Emirates

International audienceIn desert regions, dust is the most critical atmospheric parameter for irradiance assessment and solar resource conversion. Nowadays, atmospheric communities – chemical transport and re-analysis models – provide aerosols information, including dust, but with a spatial resolution greater than 100 km. This low spatial resolution makes the prediction of aerosol loads in a small scale very difficult, considering the possible high spatial variability of this aerosol loads in such desert regions. It has been indeed established in the United Arab Emirates that the variation of aerosol optical depth (AOD) within 100 km can lead to 18% deviation on Direct Normal Irradiance (DNI) estimations. Therefore, the MACC AOD, which is provided at a spatial resolution of 125 km, has to be corrected before being used for DNI estimation, as well as any other publicly available AOD database. In this work, images from the High Resolution Visible channel data of the SEVIRI instrument on board Meteosat Second Generation satellite are used to downscale the MACC AOD. The first results of the downscaling approach are tested with one year datasets of AOD from two AERONET ground stations showing that this downscaling leads to a decrease of the mean absolute error on AOD and on the corresponding estimated DNIs

A methodology for determining optimum solar tower plant configurations and operating strategies to maximize profits based on hourly electricity market prices and tariffs

The present study analyzes the influence that market conditions have on determining optimum molten salt solar tower plants with storage that maximizes profits (in terms of plant configuration, sizing, and operation) for a location in South Africa. Three different scenarios based on incentive programs and local wholesale electricity prices are considered. A multi-objective optimization modeling approach was followed, showing the tradeoff curves between minimizing investment and maximizing profits when varying critical size-related parameters (such as nameplate capacity, solar multiple ISM), and storage capacity) together with power-cycle design and operating specifications including dynamic startup curves and different storage dispatchabiliry strategies. Results are shown by means of a comparative analysis between optimal plants found for each scenario, highlighting the value that storage has wider the current two-tier tariff scheme and the relevance of designing a suitable policy for technology development. Finally, a final analysis is performed with regard to the indicators used for economic evaluation of power plants, by comparing the differences between optimum designs found when using the levelized cost of electricity (LCoE) solely as performance indicator instead of cash-flows and profit-based indicators, such as the internal rate of return (IRR).Peer Reviewe