Latest Scientific Papers

Tailoring HYSOL: Solar Energy Contribution to Reach Full Dispatchability and Firmness in Target Markets (2016)

Renewable energies for electricity generation are traditionally considered a risk for the electricity system due to their lack of dispatchability and firmness. Renewable energies penetration is constrained to strong grids or else its production must be limited to ensure grid stability, which is kept by the usage of hydropower energy or fossil-fueled power plants. CSP technology has an opportunity to arise not only as a dispatchable and firm technology, but also as an alternative that improves grid stability. To achieve that objective, solar hybrid configurations are being developed, HYSOL being the most recent solution. Three reference scenarios have been defined: Kingdom of Saudi Arabia (KSA), Northern Chile (CHL) and Baja California in Mexico (MEX), considering their respective weather conditions and market demand profile. These scenarios have been modelled, simulated and evaluated in terms of dispatchability and firmness defined by the authors. The results show that HYSOL technology has potential to become a reference in providing firm and renewable power, although a detailed design and control system are required.


Full environmental life cycle cost analysis of concentrating solar power technology: Contribution of externalities to overall energy costs (2016)

The aim of this work is to investigate the use of Full Environmental Life Cycle Costing (FeLCC) methodology to evaluate the economic performance of a 50 MW parabolic trough Concentrated Solar Power (CSP) plant operating in hybrid mode with different natural gas inputs (between 0% and 30%). The analysis is based on a plant located in Southern Spain and includes current financial incentives for the promotion of renewable energies. The analysis also incorporates an estimation of external costs associated with atmospheric emissions on six categories: Human Health, Loss of Biodiversity, Local and Global Damage to Crops, Damage to Materials and Climate Change. In a scenario where the project is funded through equity, the life cycle internal costs of the plant operating with solar energy only represent 82.8 €/MW h, while revenues from electricity sales amount to 85.7 €/MW h, resulting in a net present value of 2.95 €/MW h. Internal costs are attributable primarily to the purchase of materials and equipment incurred mainly during the Extraction and Manufacturing life cycle phase. In this scenario, external costs (calculated using CASES damage costs methodology) represent less than 2.6% of all the internal costs considered.

Hybridizing CSP with natural gas allows higher overall power outputs due to extended operating hours. However, this strategy involves higher internal costs, resulting in a significant reduction in the revenues (per unit of power generated) and in the net present value of the project. Thus, the existing regulatory system in Spain makes CSP hybridization with natural gas economically unattractive. In addition, the use of natural gas in CSP installations results in a rapid increase in environmental damage as evidenced by higher external costs. For instance, external unit costs of CSP with 30% natural gas were up to 8.6 times higher than in solar-only operation, due primarily to increased greenhouse gas emissions. When the analysis is extended to consider financing through bank loan under common market conditions, the same project shows economic viability for percentages of natural gas hybridization up to 14%. However, solar-only operation remains as the best option.


Operation and Training Tool for a Gas - Molten Salt Heat Recovery Demonstrator Facility (2016)

The supply of stable and reliable power is the main challenge that renewable power plants must tackle. Concentrating Solar Power (CSP), among renewable energies, is one of the most appropriate for large-scale energy production since it can efficiently store heat by means of Thermal Energy Storage (TES) systems. However, under unfavorable meteorological conditions, they may not be enough to satisfy the thermal demand of the power plant. With this aim emerges the HYSOL project, which presents an innovative hybridization configuration of CSP and biogas for a 100% renewable power plant. The demonstrator of this technology includes a gas - molten salt Heat Recovery System (HRS), a virtual gas turbine, a molten salt tank and an air cooler. The design of an operation and training tool for the HYSOL project, which includes a dynamic model of the demonstrator, is essential to evaluate the transient response, to test control schemes and to train plant operators. The design of such tool is described in this paper.


Feasibility Study on HYSOL CSP (2016)

Concentrating Solar Power (CSP) plants utilize thermal conversion of direct solar irradiation. A trough or tower configuration focuses solar radiation and heats up oil or molten salt that subsequently in high temperature heat exchangers generate steam for power generation. High temperature molten salt can be stored and the stored heat can thus increase the load factor and the usability for a CSP plant, e.g. to cover evening peak demand. In the HYSOL concept (HYbrid SOLar) such configuration is extended further to include a gas turbine fuelled by upgraded biogas or natural gas. The optimised integrated HYSOL concept, therefore, becomes a fully dispatchable (offering firm power) and fully renewable energy source (RES) based power supply alternative, offering CO2-free electricity in regions with sufficient solar resources.

The economic feasibility of HYSOL configurations is addressed in this paper. The CO2 free HYSOL alternative is discussed relative to conventional reference firm power generation technologies. In particular the HYSOL performance relative to new power plants based on natural gas (NG) such as open cycle or combined cycle gas turbines (OCGT or CCGT) are in focus. The feasibility of renewable based HYSOL power plant configurations attuned to specific electricity consumption patterns in selected regions with promising solar energy potentials are discussed.


Base Case Analysis of a HYSOL Power Plant (2015)

Concentrating solar power (CSP) plants are regarded as an alternative solution for electricity generation. The main drawback of this technology is related to the intermittent and seasonal nature of the solar irradiation. As a consequence, most CSP plants have a reduced capacity factor and difficulties to supply electricity on demand to the grid.

The integration of energy back-up systems may contribute to increasing power generation capacity and stability. Several options are being developed at present which are based on the incorporation of Thermal Energy Storage (TES) and also the use of auxiliary fuels. HYSOL is a new concept in CSP technology that relies on the integration of a molten salt TES system operating in hybrid mode with a biogas turbine with a Heat Recovery System (HRS). This paper illustrates the methodology and first results obtained during the development of the static model, considering a Base Case of HYSOL configuration. The study of this Base Case allows evaluating the impact of HYSOL technology, providing preliminary plant information and defining the required tools to be used in the project.


Numerical Analysis for the Characterization of Non-ordinary Heat Exchangers (2016)

Heat exchangers are an essential component of any energy production system. Obtaining a detailed characterization of them is a must for the design and operation of an energy plant. This article presents a characterization process of a finned tube heat exchanger with an unusual configuration. Throughout the article, the proceedings to study the influence of two unusual features that make unsuitable the use of reference models for heat exchangers are explained. One is the inclination of the tubes in the direction transverse to the flow velocity, which causes variable spacing between finned tubes. The other feature that prevents the application of the reference models is the importance of bypass flow, not negligible due to the small distance between walls compared with the width of the flow path near to the walls. A computational fluid dynamics (CFD) steady-state analysis has been completed in order to study this problem. The results show that although the inclination of the tubes does not affect considerably the overall performance of the exchanger, the influence of bypass flow close to the wall causes a significant reduction in pressure drop and a substantially lower heat transfer capacity than calculated with analytical models. This study was conducted within the Seventh Framework Programmes FP7, for the HYSOL project. HYSOL plant has been proposed as an alternative to deliver dispatchable and firm energy regardless the climate conditions throughout the whole year while it uses 100% renewable energy sources for electricity production through is innovative hybrid system.