Electrical Heat Tracing (EHT) is required in CSP plants to prevent freezing/solidification of molten salts (from 260 °C), Heat Transfer Fluid, synthetic oil (15 °C) and water or condensates (0 °C) when fluids remain static in pipes or equipment, or for pipe and equipment pre-heating. Its main function is to pre-heat empty pipes and equipment, to maintain the right temperature throughout the process and to avoid solidification of the fluids. According an accurate and optimized design, heating cables turn electrical energy into heat in order to compensate the heat losses flow from the pipe to a colder ambient. EHT becomes critical in CSP plants for the thermal energy system (TES) and balance of plant (HTF&BOP). A thoroughly planned EHT solution makes the process smoother and avoids costly blockages in piping. Its failure can lead to major losses which could affect the overall profitability ratio of the plant. Therefore, it is important to choose a reliable and experienced partner who offers the whole system for your CSP plant, including engineering, commissioning and design. With less than 1 % total project budget, EHT is a small but key investment and nevertheless a critical part in the project. Lack of EHT performance experience lead to major and costly problems and can risk the whole project.
eltherm offers a flexible and cost-effective turn-key solution, from the reception of customer data to commissioning, optimizing design and user-friendly operation and maintenance.
Schematic Overview of a CSP Plant Heat Tracing System:
The right Heating Cable for the Process
The choice of the appropriate heating cable for each kind of process is very important. For frost prevention applications of water pipelines, we offer an extensive range of self-regulating, constant wattage or series resistance heating cables from our own production. Most common technologies, like parabolic trough, compact linear fresnel reflector or stirling solar dish, rely on Heat Transfer Fluid (HTF) to operate the steam turbine which generates the power. This fluid has to be mainained at a certain temperature. Another key point is the heating up and temperature maintenance of molten salt. Solar Power Towers, i. e., use molten salt as a heat transfer fluid to improve the system performance. The maintenance and/or operation temperature at these application are very high: Up to 400° or 565°C operation temperature, depending on the plant type. This is where our highly resistant mineral insulated heating cables (ELK-MI) are used. ELK-MI cables have a high power output at high operating temperatures and are the preferred solution for high-temperature applications in aggressive enviroment. They are extremely resistant, moisture proof and mechanically stable.
A critical point is the assembly of these cables. Only high precision laser welding technology ensures a safe and reliable connection with a consistent quality. eltherm offer this advanced technology as a standard for mineral insulated heating cables. The connections are absolutely steam proof, no hazardous fluxing agents remain. Unsoldered joints provide more connection flexibility. Even Laser welding of Stainless steel, Alloy 825 and Inconel is possible.The laser welded assembly for MI-cables reduced both maintenance works as well as service and installation costs.
Temperature Monitoring and Supervision
A particular challenge for an electrical heat tracing system in a CSP plant, especially at molten salt applications, is the measurement, supervision and safety control of the heating circuits. With TraceVision®, the eltherm engineers have created a new standard in control and monitoring that is safe, reliable, highly flexible and adaptable according to the customer‘s requirements. At applications with extremely high throughput rates it performs a wide range of processing tasks with powerful arithmetic operations ability, high processing speed, precision and flexibility combined with simple configuration and commissioning. The temperature, measured by one or more temperature probes, is transmitted via a CAN-open I/O module and processed by the EL-HTC/22 Heat Tracing Controller. The self-consumption of the system is constantly measured. If it exceeds or drops below certain values, an alarm is activated, allowing to identify the possible failures.
eltherm TraceVision® System
The compact EL-HTC/22 heat tracing controller is an allrounder which allows to control and monitor industrial control tasks. In combination with our innovative TraceVision® software, it is the perfect solution for easy to handle and cost-effective supervision and control of the entire EHT system.
TraceVision® MANAGER: the server application, installed in one machine for every project. This is the software core of the system
TraceVision® VIEWER: the client application. Every device with this software installed is able to connect to the TraceVision®MANAGER for access to the system. Several devices can get an access to the MANAGER simultaneously.
North-east the scenic city of Ouarzazate, known for its picturesque kashbahs and location of several Hollywood movies, there is one of the most state-of-the-art solar power plant worldwide located. The hot sun in the moroccan desert provides enough solar energy to run a 160 MW power plant - one of the biggest parabolic through CSP plant in the world. The leading spanish consortium TSK-Acciona-Sener, contracted by ACWA Power Ouarzazate, which has been contracted by the Moroccan Agency for Solar Energy (MASEN), commissioned eltherm with the responsibility for electrical heat tracing of the molten salt circuits. Molten salt is used to store the heat (up to 3 hours in this case) so that energy will be produced, even when the sun is not shining.
The eltherm engineers met this challenge and accomplished the whole engineering of the EHT system in just a three month period. Also the production, assembly and in-time delivery of the heating cables took place in a very short time frame. 315 heating circiuts in molten salt and 30 circiuts in HTF, with over 18 km of mineral insulated heating cable (single and twin core) in total had been installed. That means: 800 laser welded joints, over 500 junction boxes and over 600 Pt100 temperature sensors. A particular task was the design of the supervision and control system for these circiuts. eltherm developed a new standard with the TraceVision® System, consistent of a PLC, several I/O modules, completed by the TraceVision® MANAGER and TraceVision® VIEWER software to ensure a smooth and easy handling.
On site, there were 30 installers working on the assembly of the heating cables, temperature sensors and accessories. After completion, the NOOR 1 plant has a reliable EHT system with a reduced rate of failures, sophisticated measurement and control technology and high-end supervision options.
But NOOR 1 is just the beginning: Morocco is already planning NOOR 2, NOOR 3 und NOOR 4. On a 3,000 ha site, the whole complex will produce 500 MW, energy for approx. 1.23 million people. This means an environmental CO2-saving of 600,000 tons! The Ouazarzarte project is a reference object for a climate friendly and lowcarbon technology - and eltherm adds its part with state-of-the-art products.
eltherm lands Xina Solar Contract
eltherm South Africa has been awarded the contract for the heat tracing system design and installation for the Xina Solar One power plant near Pofadder in the Northern Cape. It is eltherm’s first major project in South Africa since establishing its operations in Johannesburg a year ago. The contract, awarded to eltherm South Africa by Abengoa, will include the customised development, engineering and construction of Xina Solar One’s heat tracing system.
Kilometres of mineral insulated heating cable will be used for the heat tracing system of the solar project designed as a parabolic trough plant. These cables will feature laser welded termination points that prevent water ingress and therefore avoid any moisture issues that might arise. Furthermore, the heating system will be managed by eltherm’s customised TraceVision® software and controllers that enable efficient and uninterrupted operations at the plant.
The heat tracing phase of the Xina Solar One project is scheduled to start in June 2016 and will take approximately six to eight months to complete. Giles Maynard, general manager of eltherm South Africa commented: “We’re extremely excited to form part of this significant solar plant project which sets the tone for our growth trajectory in the local CSP (concentrated solar power) market. The project also puts us on course to become one of the country’s leading heat tracing system providers and also reconfirms our commitment to contribute to the country’s local economic development.”
The 100 MW Xina Solar One plant’s parabolic trough technology will provide a five-hour thermal energy storage capacity using molten salts which will assist in meeting peak demand, after sunset. The heat tracing system therefore forms an integral part in storing and harnessing solar energy. This plant will produce clean energy to serve more than 95,000 households and will prevent the emission of 348,000 tons of CO2 per year.