Novatec Solar and a group of partners from research and industry are cooperating to develop a guideline for determining the power yield of solar thermal power plants as part of the CSPBankability project, an initiative funded by the German Ministry of Economics and Energy (BMWi). The first edition of this guideline is to be published in English in summer 2015.

A solar thermal power plant uses mirrors to focus the incident solar radiation onto a receiver. The heat thus generated is absorbed by a fluid which is transferred to a conventionally operated power plant process, using the heat to generate electricity.

An accurate definition of the expected electricity yield is an essential criterion in the financing of a power plant project. Besides a description of technical system features, a yield model also requires a realistic assessment of the expected amount of solar irradiation, while at the same time taking into account the influence of varying irradiation levels as well as different feed-in tariff structures for the energy produced. Uncertainties may emerge both in the description of technical components and in solar resource assessment. These, too, must be considered by the calculation method.

The benefits of standardisation
Currently, the global capacity of solar thermal power stations reaches over 3 GW, with plants in size from 1 to 370 MW. So far, however, no common criteria are available for calculating specific electricity yields. In developing the guideline, project partners are hoping to produce electricity yield forecasts of greater quality, transparency and reliability. These improvements will be helpful in reducing risk premiums imposed on project financing, which are still excessively high. At the planning stage of a plant, project developers but also numerous other stakeholders have to reach a consensus concerning the yield calculation approach and its reliability. Stakeholders involved are suppliers, clients, consulting companies, investors, funding agencies as well as insurers. A common approach will lead to greater efficiency and fewer lapses in communication.

On the engineering side, newly designed equipment must continuously be checked against the current state of technology to be able to identify any pros and cons as accurately as possible and to adjust engineering activities at an early stage. Introducing a standard for the underlying predictive analyses will increase their relevance and make studies by different providers comparable with each other.

German CSP technology and standards for international markets
German industry traditionally has a strong position in the solar thermal power plant business even though most plants are not operated in Germany but in sunnier regions of the world. The aim of this initiative is to create a common regime of electricity yield calculation, sharing the methods initially developed in Germany on a global basis. Following consultations with one of the International Energy Agency’s expert working groups, SolarPACES, it has been proposed that an international standard be developed based on these guidelines.

The product of these efforts will be an electronically accessible manual which documents the various methods for estimating electricity yields. The manual will provide a concise outline of existing concepts. In an extensive appendix, the various calculation methods will be described in detail. The manual will be complemented by a selection of case studies involving various CSP technologies. Besides helping with the prediction of energy yields the manual will also offer advice concerning cost and financing structures as well as the choice of pertinent data sources for solar resource assessment.

The first edition of the manual covers parabolic trough systems with oil as a heat transfer medium. Further chapters will be added by 2016. These will extend the specifications to include solartower and linear Fresnel technologies as well as systems using alternative heat transfer media such as salt, air and steam.

BMWi funding
Work carried out under the CSPBankability project is grant-funded by the Federal Ministry of Economics and Energy (BMWi) based on a parliamentary resolution of the Deutsche Bundestag.

Project partners

DLR Institute of Solar Research (www.dlr.de/sf)
The Institute of Solar Research of the German Aerospace Center (DLR) is one of the leading research institutions worldwide in the area of Concentrated Solar Power (CSP). The Institute’s 140 workplaces are spread across three DLR sites in Germany and Europe’s largest test facility for concentrating solar technology run by DLR’s Spanish research partners CIEMAT, the Plataforma Solar de Almería. In Jülich the Institute operates the experimental solar thermal power plant “Solar Tower Jülich”. The Institute of Solar Research seeks to build bridges between basic research, large-scale projects and industrial applications.

Fraunhofer ISE (www.ise.fraunhofer.de)
The Fraunhofer Institute for Solar Energy Systems ISE with its headcount of 1,300 is the largest solar energy research institute in Europe. The Institute develops materials, components, systems and processes for energy efficiency, energy generation, energy distribution and energy storage. Fraunhofer ISE also offers its clients a range of relevant testing and certification services. The Institute is a member of the Fraunhofer Society, Europe’s largest application-oriented research organisation.

Fichtner (www.fichtner.de)
Fichtner is Germany‘s largest independent consulting firm in the energy sector. It handles more than 1,200 ongoing projects every year. Currently, some 50 of them are CSP projects. Fichtner acts as an experienced planner and consultant, assisting clients throughout all project stages from initial feasibility studies to commissioning to final acceptance, covering all project sizes from pilots to large-scale plants of several hundred MW of installed capacity.

Suntrace GmbH (www.suntrace.de)
Suntrace is an internationally operating consulting firm for large-scale solar projects. It focuses on emerging markets with high growth potential in solar energy, mainly in Latin America, Africa and Asia. Suntrace typically supports the entire project development process from site identification, project qualification, site-specific and technology-independent conceptual design to financing aspects.

Novatec Solar (www.novatecsolar.com)
Novatec Solar is a leading technology supplier for concentrating solar power, specialising in the production, supply, and turnkey delivery of solar fields based on Fresnel collector technology. These are suitable for a wide range of applications such as power generation in solar thermal power plants and the production of process steam for industrial processes, for example to enhance cost efficiency in oil production. Solar technology from Novatec Solar generates steam at temperatures of up to 550°C. Novatec Solar constructed the world's largest Fresnel solar power plant, PE2, in Spain.

IATech (www.iatech.de)
As a spin-off company of Solar Institut Jülich, IA Tech GmbH provides consultancy, engineering and project development services for the finance and energy sectors. Looking back on more than 20 years in the concentrated solar power business, IATech’s employees can serve clients with a wealth of expertise. Their work is cost-effective thanks to a set of advanced simulation tools developed in-house and years of hands-on experience with the development and operation of Solar Tower Jülich.

Solar Tower Technologies AG (www.solartowertechnologies.com)
Solar Tower Technologies AG (STT) is a technology provider offering systems and solutions for the solar thermal (CSP) sector, and particularly for solar-tower plants. The ‘solar islands’ built with STT’s patented technologies and solutions – especially heliostat arrays and receivers – are significantly more efficient than current reference systems on the market.

DNV GL (www.dnv.de)
DNV GL-Energy is a part of the DNV GL Group whose business objective it is to help protect lives, property and the environment in important industrial sectors. The firm’s main activities are to provide independent business and engineering services such as risk management, classification, certification and testing of installations in the marine, oil and gas industries as well as in the energy sector. We also provide certification services for customers from many other sectors. The company was established in 1864 and operates in more than 100 countries with a workforce of 16,000 employees. Its corporate motto is ‘safer, smarter, greener’.

Professor Olaf Goebel
Prof. Dr.-Ing. Olaf Goebel has been actively involved in the CSP sector for 24 years. After nine years at DLR’s Stuttgart site he took a position in industry. He has participated in numerous CSP projects in a variety of roles and project stages, from feasibility to commissioning. Before taking a professorship at the Hamm-Lippstadt University of Applied Sciences, he worked as Head of Engineering at Masdar, Abu Dhabi, where he managed – among other projects – the 100 MW CSP project Shams 1.

Power plant yield forecasting at different project stages

Parabolic trough power plant