Concentrated Solar Power Collectors for District Heat in Northern Europe

Compared to steam turbines based on a water circuit, ORC installations make it possible to recover heat from low-temperature sources available in small-capacity plants. An ORC system can work well in concert with biomass combustion and solar concentrating units. The system was named for its use of an organic fluid characterised by high molecular mass and a liquid-vapour phase change at temperatures below water-steam transformation.
The ORC unit in Brønderslev will come from Italian-based Turboden. Turboden has implemented around 300 ORC units all over Europe in recent years, according to a document by DTU, the Technical University of Denmark (see the document attached).
The parabolic trough field was delivered and installed by Danish-based Aalborg CSP. It came online in spring 2017 and has since been feeding into the town’s district heating network. Once the ORC system is put into operation, as is planned for April 2018, solar energy – collected via thermal oil at around 300 °C – is said to be used for fuelling it. “By the end of this July, the collector field will have produced 6,500 MWh, and we expect 16,000 MWh from year-round operation,” said Thorkil Neergaard, Managing Director of Brønderslev Forsyning. This would translate into a specific yield of 594 kWh/m²a. Both biomass systems are said to start producing heat late this year. Neergaard expects gas to be used only during very cold periods and perhaps the units could be stopped during some years completely.
More information in the following link:

Concentrated Solar Power Collectors for District Heat in Northern Europe

 

 

 

 

La termosolar genera el 4,1% de la electricidad en España en julio

En el mes de julio, con la información estimada a 31 de julio, la generación procedente de energías renovables ha representado el 31% de la producción.

Según la fuente de generación de la energía, el 20,6% fue nuclear, el 18,8% del carbón, el 17,8% de ciclo combinado, el 15,5% fue eólica, el 10,8% procedió de la cogeneración, un 5,3% hidráulica, un 4,2% solar fotovoltaica, un 4,1% termosolar, un 1,3% de residuos, y un 1,6% de otras energías renovables.

La demanda peninsular de energía eléctrica en julio se estima en 22.423 GWh, un 0,9 % superior a la registrada en el mismo mes del año anterior. Si se tienen en cuenta los efectos del calendario y las temperaturas, la demanda peninsular de energía eléctrica ha aumentado un 0,9% con respecto a julio del 2016.

En los primeros siete meses del año, la demanda peninsular de energía eléctrica se estima en 147.417 GWh, un 1% más que en el 2016. Una vez corregida la influencia del calendario y las temperaturas, la demanda de energía eléctrica ha aumentado un 1,4% respecto a la registrada en el año anterior.

Fuente: Notas de Prensa REE

¿Cómo puede acceder una pyme a los fondos europeos?

El Gobierno de Navarra acaba de darle una respuesta «rápida» a esa pregunta. Lo ha hecho a través de una obra -«Guía Rápida de Fondos Europeos para pymes»- que el Ejecutivo foral acaba de publicar en colaboración con la Red Enterprise Europe Network de la Asociación de la Industria de Navarra (AIN). ¿Objetivo de la guía? «Ofrecer una visión general de las oportunidades de financiación ofrecidas desde la Unión Europea».

 

El delegado del Gobierno en Bruselas, Mikel Irujo, presentó ayer en Aribe (Aezkoa, Navarra) la «Guía Rápida de Fondos Europeos para pymes», documento que ha elaborado «con el objetivo –informa el Ejecutivo navarro– de ofrecer una visión general de las oportunidades de financiación ofrecidas desde la Unión Europea». La guía, que el Gobierno asegura estará muy pronto disponible en la página oficial de la Delegación, será presentada durante los meses de julio y septiembre en diversas localidades del territorio foral, para lo que cuenta con la colaboración de los consorcios de desarrollo territorial.

La Unión Europea -informa el Gobierno de Navarra- ofrece actualmente apoyo a las pymes (pequeñas y medianas empresas) a través de varias líneas de ayuda, como son las subvenciones, los préstamos y las garantías, a las que las pymes pueden acceder a través de ayudas directas, de programas gestionados a nivel regional o nacional o también a través de una serie de instrumentos de asistencia de carácter no financiero, en forma de programas y servicios de apoyo a las empresas.

Estos programas de apoyo -informa el Gobierno- se pueden dividir en 4 grandes categorías

  1. Fondos estructurales

Son los fondos europeos que, gestionados a nivel nacional y regional, pretenden mejorar la cohesión económica y social europea. Las empresas pueden acceder a las diferentes convocatorias lanzadas por las regiones y las entidades intermediarias gestoras de dichos fondos.

  1. Oportunidades temáticas de financiación

Se trata de la financiación temática a las que las pymes pueden acceder directamente con la presentación de propuestas de proyectos en la que la ayuda se consolida a través de la cofinanciación de los gastos del proyecto (Cosme, Horizonte 2020, Europa Creativa…).

  1. Instrumentos financieros

Se trata de los préstamos, garantías, financiación de inversiones de capital riesgo y otras formas de financiación por participación que son ofrecidos por intermediarios financieros nacionales, muchos de ellos gestionados por el Fondo Europeo de Inversiones y el Banco Europeo de Inversiones.

  1. Ayuda a la innovación y a la internacionalización de las pymes

Se trata de programas e instrumentos de apoyo gratuitos para las pymes ofrecidos por entidades intermedias que cuentan con cofinanciación europea para su desarrollo.

Según el Gobierno de Navarra, «el acceso a financiación sigue siendo uno de sus principales problemas [de las pymes], de ahí que la Delegación del Gobierno en Bruselas haya tomado la iniciativa de ofrecer esta guía».

Fuente: Energías Renovables

https://www.energias-renovables.com/panorama/como-puede-acceder-una-pyme-a-20170704?utm_campaign=newsletterERSolar&utm_medium=boletinClick&utm_source=Bolet%C3%ADn+Solar+2017-07-04

LINEAR FRESNEL SYSTEMS AND THE FUTURE FOR CONCENTRATED SOLAR POWER

Concentrated solar power systems have until recently focused on bulk electricity production, with the main focus on solar towers and trough type collectors. Recent developments have focused on smaller units to supplement thermal power stations and to provide heat for industrial processes. Collectors based on the linear Fresnel reflector design are leading the pack.

There is a gap in the market between non-concentrating rooftop collectors used for solar heating and large scale systems used for bulk electricity generation. This gap is being filled by systems which use linear instead of circular focusing. Two main systems are the solar trough and the linear Fresnel (LFR) based collector. Although the trough based system has proven itself over many years of operation in different applications, the Fresnel system is emerging as an alternative with several advantages.

Fig. 1: Typical large scale LFR system [3].

LFR plant is highly modular, ranging from a few hundred kW to several MW in size, and offers the lowest land occupancy compared to other CSP technologies. Parabolic troughs represent the optimal solution for achievable concentration ratio and achievable energy yield per aperture area and, hence, the best overall plant efficiency in line-focussing mirror systems. For that reason CSP development efforts have concentrated on parabolic trough geometry.

Nevertheless, in the last decade LFR systems have aroused an increasing interest. The main reason for this is the search for cheaper solar field solutions. The considerable economic advantages of Fresnel collectors are principally related to their constructive simplicity. In addition, Fresnel solar fields permit higher land use efficiency than any other type of solar fields. These advantages can offset the lower solar-to-heat efficiency, and LFR power plants represent an interesting alternative to parabolic trough power plants [1].

Fig. 2: Principle of Fresnel mirror system [1].

The main advantage of LFR systems is that their simple design of flat or flexibly bent mirrors and fixed receivers requires lower investment costs and offers a wide range of configurations. Originally designed for low and medium power applications, LFRs are now being designed for higher temperatures which facilitate direct steam generation (DSG) which can be used efficiently in the industrial or power generation sector.

Fresnel systems can be configured to operate over a wide range of temperatures, from 200 to 500°C, although systems with temperatures as high as 550°C are under development. Applications range from industrial process heat, distributed power generation using the organic Rankin cycle to steam turbine systems.

Developments in energy efficiency in both industry and power generation have focused attention on medium and high temperature solar thermal systems. LFRs have great potential in southern Africa due to the low cost and high percentage of local manufacture inherent in the technology.

Principle

The linear Fresnel reflector technology receives its name from the Fresnel lens, which was developed by the French physicist Augustin-Jean Fresnel for lighthouses in the 18th century. The principle of this lens is the breaking of the continuous surface of a standard lens into a set of surfaces with discontinuities between them. This allows a substantial reduction in thickness (and thus weight and volume) of the lens, at the expense of reducing the imaging quality of the lens. Where the purpose is to focus a source of light this impact on the image quality is not of major importance [1].

The principle of dividing an optical element into segments which have the same (or a very similar) optical effect as the original optical element can also be applied to mirrors. It is possible to divide a parabolic mirror into annular segments, forming a circular Fresnel mirror which focuses the light that arrives in rays parallel to the optical axis onto the focal point of the paraboloid mirror.

In an analogous way, a linear Fresnel mirror can be constructed substituting a parabolic trough by linear segments that focus the radiation that arrives in a plane parallel to the symmetry plane of the parabolic trough onto the focal line of the parabolic trough. A LFR has a similar effect to a parabolic trough, when considering the concentration of the radiation in a focal line i.e. a LFR behaves like a parabolic trough with the same focal length and the same aperture [1].

Fresnel mirror system

The mirrors focus the sun onto a receiver which contains the heat transfer medium which could be water, oil or even molten salt in some designs. The heat transfer medium used will depend on the operating temperature of the system. The main difference between the two systems lies in the way that the sun’s rays are tracked, and this is what gives rise to the cheaper cost of Fresnel.

In the trough system the whole structure rotates about an axis coincident with the focal point of the trough. This means that the mirrors and the collector are connected mechanically, requiring bearings through which the collector tube must pass. In the Fresnel system the individual mirrors rotate to track the sun. There is no mechanical connection between the mirrors and the collector.

Separation of the mirrors and the receiver allows high temperature heat transfer mediums to be used, and also a much wider scope in the design of the receiver. The Fresnel system also allows individual control of each mirror, effectively changing the configuration of the reflector to optimise its function.

Fig. 3: Mirror tracking with Fresnel system [1].

LFR construction

Aperture

The mirror aperture is the area of the reflector mirrors in the horizontal position, and defines the amount of solar radiation collected by the LFR. Aperture is usually quoted on a module or single mirror length basis. Increasing the mirror aperture increases the amount of solar radiation reflected to the receiver module. Typical aperture widths for large systems are of the order of 15 m.

The receiver aperture is the area of the receiver per mirror or module length, and varies according to the design of the system. Receiver width is close to the mirror width, but may be less if curved mirrors are used, or wider if other focusing methods are used.

Mirror construction

Mirrors may be flat or elastically curved and are generally constructed of glass with a composite/metal backing, although other materials are finding their way into the sector. Adding curvature to the mirror increases the concentration ratio and makes the design of the receiver simpler. Mirror width and length will depend on the design. The mirrors are mounted in the tracking system in several different ways. A typical mounting would be a circular loop driven by a tracking motor (Fig. 4).

Receiver construction

The receiver generally consists of a secondary reflector mounted above the receiver tube which contains the heat transfer fluid. The receiver may consist of a single tube or several tubes, which may be contained in a vacuum glass tube enclosure. Typical designs are shown in Fig. 5.

Fig. 4: Mounting and tracking system [1].

The LFR system alone cannot reach the same radiation concentration as a parabolic trough. The sun changes its position in relation to the optical axis plane of the system. It is theoretically impossible to design the curvature of the individual mirror strips in such a way that there is always a sharp focal line for parallel radiation, and it is necessary to mitigate the unavoidable optical inaccuracy of the Fresnel collector. This can be done by a secondary concentrator that is located above the receiver tubes.

Concentration ratio

The collector concentration ratio is the ratio of mirror aperture to receiver aperture. The low-profile setting of LFR collectors maximises the concentration ratio, which enables high temperature output.

Fundamentally, increasing the mirror aperture allows more sunlight to be reflected onto the receiver. Because the low-profile architecture provides for great flexibility in the selection of length and concentration ratio, linear Fresnel collectors can be readily tailored for different target temperatures to meet varying application needs, thus providing practical versatility of usage. As an example, the Fresdemo system has a primary mirror field width of 21 m and a receiver width of 0,5 m, giving a concentration ratio of 42 [8].

Heat transfer fluids

The fixed design of the receiver gives a wide choice of heat transfer fluids. Water is used as the transfer fluid at low temperatures, oil as temperatures increase, steam for much higher temperatures and molten salt for the highest ranges. In addition, pressurised CO2 or air are being considered for higher temperature operation [7].

Conversion efficiency

LFR exhibit optical conversion efficiency in the region of 65%. Conversion efficiency depends on the angle of incidence of the sun, and thus average efficiency will vary with latitude. Thermal peak output of 562 W/m2 in terms of primary reflector aperture area, and 375 W/m2 in terms of installation area usage, is claimed for a typical commercially available system [8].

Fig. 5a: Secondary concentrator on receiver [3].

Applications

Medium heat generation

Medium heat systems for industrial applications or supplementary power systems operate in the temperature range 100 to 250°C and may use water or oil as the heat transfer medium. There are numerous systems of this type in operation.

Direct steam generation

Thanks to the fixed absorber tubes, direct steam generation (DSG) is easier in LFR power plants than in parabolic trough power plants. DSG has several advantages over oil heat transfer:

  • Steam as heat transfer fluid allows higher temperatures because there is no danger of thermo oil cracking. Novatec Solar is planning a new Fresnel power plant generation that operates at 450°C [3].
  • The number of construction components can be reduced because no heat exchange has to be realised between a solar field heat transfer fluid/thermo oil) and Rankine cycle working fluid (water/steam).
  • The thermo oil itself is an expensive component of CSP plants, so the lack of thermo oil is a direct advantage.
  • As there is no heat transfer between two heat transfer fluids, there is one thermal loss factor less.
  • The use of steam as a heat transfer fluid may reduce the mean heat transfer fluid temperature in the absorber tube (even at higher final temperatures) and reduce thermal losses. This reduction is possible because in a large part of the receivers the boiling process is realised, which takes place at a reduced temperature. Only in the small part, where the superheating of the steam is realised (if there is superheating), high temperatures are reached.
  • Water has further advantages in comparison to other HTFs: It is environmentally friendlier than thermo oil so that leakages in a steam generating plant do not produce environmental dangers.

Fig. 5b: Secondary reflector multiple tube technology (Ausral).

Water is less corrosive than salt. Its freezing temperature is much lower than the freezing temperature of salt and even slightly lower than of thermo oil. The effort required to ensure adequate anti-freeze protection is reduced significantly.

There are several systems on the market that use DSG. In this system water is fed through pipes in the receiver where it is converted to steam and then to superheated steam. Steam is used to drive turbines directly or as supplementary heating for thermal power plants. Steam is also used for industrial purposes.

Molten salt systems

High temperature systems (≈550°C) using molten salt as the heat transfer medium have been developed. Such systems incorporate heat storage systems for prolonged operation. Fig. 6 shows a high temperature plant using salt as the heat transfer medium [3].

Because of the simplicity of design and the high operating temperatures now possible, LFR are being considered as alternatives to tower and heliostat based CSP systems. In addition, the short optical path between mirror and receiver eliminates many of the tracking problems as well as environmental objections associated with tower/heliostat based systems. In addition LFR salt based systems are able to recover from “salt freezing”.

Supplementary heat or steam generation for power plants

Fresnel mirrors are being considered as a means to supplement heat in thermal power stations. Parts of the cycle such as preheating of the boiler feed water use low to medium temperature heat sources, and solar thermal systems can provide this heat. Typical applications are to substitute the bleed steam used for preheating boiler feedwater as shown in Fig. 7.

Fig. 6: High temperature CLF system using molten salt [3].

The solar heat source is connected in parallel with the bled steam source and when available provides the heat normally used from the steam. The increased steam output then enables additional power generation from the turbine (solar boosting mode) or fuel consumption can be reduced (fuel saver mode).

More complex systems use several stages of regeneration with heat substitution at each stage. Heat may be stored for periods when the solar resource is low, or the plant may be operated in a two shift mode. Using solar power may have two effects:

  • Increase in the power generation capacity of the plant during periods when solar power is available.
  • Decrease in coal consumption with no increase in power generation.

The integration of solar thermal collectors into conventional fossil plants, or solar aided power generation (SAPG), has proven a viable solution to address the intermittency of power generation and combines the environmental benefits of solar power plants with the efficiency and reliability of fossil power plants. In SAPG technology, thermal oil can be used as solar heat carrier and no solar steam needs to be generated, therefore the pressure of solar system can be much lower than that of the solar collector using water/steam as the heat carrier. Newer developments make use of the higher heat content of solar steam directly, provided from DSG plants.

The temperature of the heat source is one of the major defining factors of a power plant – higher temperature results in higher overall power plant efficiency. With SAPG, the heat source temperature is not limited by the solar input temperature and is therefore an effective means of utilising low or medium solar heat (250°C) for power generation. However, internationally the adoption of the technology has been slow, despite it being a viable and quick means of CO2 emission reduction.

A study was conducted on a simulated SAPG power plant at Lephalale, which was based on a generic 600 MW subcritical fossil power plant with a reheater and regenerative Rankine cycle with two low pressure feedwater heaters (FWH) downstream of the deaerator and three high-pressure FWHs upstream [5].

Fig. 7: Single-stage regenerative Rankine cycle with open feedwater heater [4].

This study showed that integrating solar thermal with steam plant is approximately 1,5 times as efficient at converting solar energy to electricity as a CSP stand-alone generating plant. Therefore, a solar assisted high pressure feedwater heater system at an existing coal-fired power station is 1,8 times more cost-effective than a stand-alone CSP plant. The conversion efficiency is claimed to be of the same order as solar PV [5].

Conclusion

The Fresnel mirror solution is gaining popularity because of cost and simplicity advantages over the parabolic trough solution for SAPG systems. Costs of the Fresnel based system are estimated to be approximately 70% of the equivalent parabolic trough system [5].

References

[1] M Gunter: “Linear Fresnel Technology”, DLR, www.energy-science.org/bibliotheque/cours/1361468614Chapter%2006%20Fresnel.pdf[2] M J Montes, et al: “A comparative analysis of configurations of linear Fresnel collectors for concentrating solar power”, Energy, 2014.[3] Novatec: “Concentrated solar power by Novatec solar”, Brochure.[4] E Hu, et al: “Solar Aided Power Generation: Generating Green Power from Conventional Fossil Fuelled Power Stations”, Intech open science.[5] W Pierce, et al: “A comparison of solar aided power generation (SAPG) and stand-alone concentrating solar power (CSP): A South African case study”, Applied Thermal Engineering, 2013.[6] Areva: “Areva integrates energy storage in solar CFLR design at Sandia national labs”, http://us.areva.com/EN/home-1977/areva-solar-power-salt-storage.html[7] S Benmarraz: “Linear Fresnel Reflectors Concentrated Solar Power: cost reduction and performance improvement trends”, IRENA Workshop, March 2015.[8] Industrial solar: “Industrial Solar linear Fresnel collector LF-11”, Technical brochure.

Mike Rycroft, features editor, EE Publishers

ee.co.za

EL CALOR SOLAR INDUSTRIAL COMPENSA

Más de 500 plantas industriales en todo el mundo confían en el calor solar. SHIP significa «Solar Heat for Industrial Processes» (calor solar para procesos industriales) y describe aquellos sistemas que proporcionan calor solar en una fábrica. El campo de colectores calienta un fluido de proceso mediante la radiación solar y un intercambiador de calor transfiere este calor a un sistema de suministro o proceso de producción en la fábrica en forma de agua caliente, flujo de aire o vapor. Las unidades de almacenamiento hacen posible utilizar el calor generado durante la noche.

Dubái marca el precio más bajo de la termosolar: 8,40 c€ / kWh

  • Supone un descenso de casi el 40% del precio mundial más bajo hasta el momento
  • Los recortes pasados y los recelos actuales del Gobierno hacia esta tecnología constituyen un error histórico

Madrid, 6 de junio de 2017.- La Autoridad de Electricidad y Agua de Dubái (Dewa) ha anunciado los precios de licitación de los cuatro consorcios que optan al desarrollo de la cuarta fase de 200 megavatios del parque solar Mohammed bin Rashid Al Maktoum. La oferta más baja presentada para el proyecto de energía solar concentrada (CSP) es de 9,45 centavos de dólar (8,40 céntimos de euro) por kWh, lo que supone un descenso de casi el 40% del precio mundial más bajo ofertado hasta el momento. Otras dos ofertas también presentaron precios inferiores a los 10 céntimos de euro por kWh.

La licitación para esta cuarta fase del parque solar de una planta termosolar con tecnología de torre incluye el almacenamiento de energía de hasta 12 horas, lo que significa que la planta podrá seguir suministrando electricidad durante toda la noche, y es la primera fase de un desarrollo que tiene previsto contar con 1.000 MW de energía termosolar con tecnología de torre.

Desgraciadamente, como consecuencia de los recortes realizados a las centrales termosolares en nuestro país, ya no hay empresas españolas entre los promotores principales, aunque Protermosolar espera que puedan participar como EPCistas en el proyecto que resulte finalmente adjudicado.

Estos niveles de precios, en un país con recurso solar de peor calidad que en España, animarán a otros muchos países a planificar la incorporación de centrales termosolares, necesarias para incorporar nueva capacidad que aporte gestionabilidad y estabilidad de red que otras tecnologías fluyentes, aparentemente más baratas, no son capaces de dar.

Para Luis Crespo, presidente de Protermosolar, “la termosolar es la única tecnología gestionable con ventajas para la estabilidad de la red con recursos más que suficientes para cubrir las necesidades eléctricas de cualquier país del cinturón solar. Y, ahora, estamos demostrando que, tras la curva de aprendizaje, podemos competir en precio con cualquier tecnología”.

El presidente de Protemosolar considera que en la actualidad “los costes de generación del kWh de las centrales termosolares con seis horas de almacenamiento son bastante más baratos que los de las centrales fotovoltaicas. Pero, además, la termosolar todavía tiene un gran margen de reducción de costes si se compara sus 5 GW instalados en todo el mundo, con los 500 GW de eólica o los 300 GW de fotovoltaica. ¿Alguien recuerda los precios de la fotovoltaica cuándo solo tenía instalados 5 GW a nivel mundial? La presente licitación en Dubái es buena prueba de que año tras año la termosolar reduce su precio”.

Para Paddy Padmanathan, director ejecutivo de Acwa Power, “es emocionante ver como la tecnología termosolar con almacenamiento ofrece energía solar despachable día y noche compitiendo con alternativas basadas en combustibles fósiles”.
Sin embargo, el presidente de Protermosolar se lamenta de “la miopía de los actuales responsables energéticos de nuestro país que sólo consideran los costes de generación de las tecnologías en lugar de analizar el valor que cada una aporta al sistema ante un escenario de cierre progresivo de las centrales térmicas y nucleares y de las repercusiones que tendría para nuestra industria el disponer de las referencias tecnológicas más avanzadas ante el enorme mercado mundial que se está empezando a abrir”.

Acerca de Protermosolar
Protermosolar es la asociación que representa al sector español de la industria solar termoeléctrica y está integrada por 50 miembros. La tecnología termosolar, en la que España es líder internacional, ha irrumpido recientemente con fuerza en el panorama de las energías renovables a nivel mundial y actualmente cuenta con un gran potencial de crecimiento por su gestionabilidad y capacidad de almacenamiento, por su elevada creación de empleo local y por su potencial de reducción de costes. La potencia instalada en España es de 2.300 MW y la contribución de las empresas españolas en los mercados internacionales es de alrededor del 75%.