Dynamic Modelling and Advanced Process Control of Power Block for a Parabolic Trough Solar Power Plant

A fundamental task in the dynamic simulation of parabolic trough power plants (PTPP) is to understand the behavior of the system physics and control loops in the presence of weather variations. This study provides a detailed description of the advanced controllers used in the power block (PB) of a 50 MWel parabolic trough power plant (PTPP). The PB model is achieved using APROS software based on the actual specifications of the existing power plant. To verify the behaviour of the PB model, a comparison between the simulated results and given real data is documented depending on a previous study, and the results indicate a reasonable degree of correspondence. The purpose of this study is to create reference models for the PB. Thereby, developers and engineers will have a better understanding of the state of the art of advanced control loops in these power plants. Moreover, these types of models can be used to specify the most suitable mode of operation for the power plant. In addition, this study gives an overview of dynamic simulation for the design, optimisation and development of power blocks in parabolic trough power plants.

Evaluating Small vs. Large Power Blocks for Pipeline Compression Stations

This paper discusses how the application of large, gas turbine-based power blocks (>50,000-hp) in pipeline compression stations can contribute to lower capital costs, improved lifecycle performance, and reduced carbon emissions. For illustrative purposes, two compression facility power block configurations (nine 30,0000-hp trains vs. five 55,000-hp trains) are compared on the basis of capital expenditures (CapEx), operating expenditures (OpEx), availability, efficiency, and operating flexibility. A summary of the study's results are as follows: – Net present value (NPV) analyses show that 5x55,000-hp ISO trains can result in up to $50 million reduction in CAPEX vs 9x30,000-hp ISO trains – By having fewer trains, operations & maintenance (O&M) costs can be reduced by as much as 20% – Lifetime fuel savings with a 5x55,000-hp train configuration vs. 9x30,000-hp trains are estimated at $40 million, owing to the increased operating flexibility of modern gas turbines, even at partial loads. The paper will also present considerations for digitalization, modular construction, and package integration – with a particular focus on how these measures can be leveraged to lower execution risk and enhance the lifecycle performance of gas turbine-driven compression trains.

Simulation of a CSP Solar Steam Generator, Using Machine Learning

Developing an accurate concentrated solar power (CSP) performance model requires significant effort and time. The power block (PB) is the most complex system, and its modeling is clearly the most complicated and time-demanding part. Nonetheless, PB layouts are quite similar throughout CSP plants, meaning that there are enough historical process data available from commercial plants to use machine learning techniques. These algorithms allowed the development of a very accurate black-box PB model in a very short amount of time. This PB model could be easily integrated as a block into the PM. The machine learning technique selected was SVR (support vector regression). The PB model was trained using a complete year of data from a commercial CSP plant situated in southern Spain. With a very limited set of inputs, the PB model results were very accurate, according to their validation against a new complete year of data. The model not only fit well on an aggregate basis, but also in the transients between operation modes. To validate applicability, the same model methodology is used with a data from a very different CSP Plant, located in the MENA region and with more than double nominal electric power, obtaining an excellent fitting in the validation.

Impact of Dry Cooler Air-Side Performance on a sCO2 Power Cycle for a CSP Application

Uncertainty around the design and control of the supercritical CO2 power cycle must be reduced before this technology can be implemented for large-scale grid support. To better understand the day-to-day performance of an sCO2 cycle, off-design performance calculations must be included for all power block components, and performance assumptions must be removed. This study has expanded the modeled scope to include the air-side performance for the dry cooler and has incorporated discretized heat transfer calculations for both streams through the pre-cooler to better predict off-design performance. This study considered a recompression Brayton cycle in a concentrating solar power application. The cycle model utilized fixed sCO2 turbomachinery maps for the main compressor, recompressor, and expander operating to supply approximately 10 MW gross at the design point. Fixed vendor-supplied fan curves were used to calculate the air-side performance of the dry cooler. The primary heater was modeled considering both the sCO2 and heat transfer fluid streams. Off-design performance was predicted for an ambient temperature range of 0–55°C, a HTF temperature range of 705–735°C, and a HTF mass flow range of 50–105% of the design point value. To understand the importance of modeling the air-side performance, the cycle off-design performance was also calculated using a constant CO2 outlet temperature assumption and a constant approach temperature assumption for the dry cooler. Results show that using these assumptions can significantly alter the power output and cycle efficiency predictions.

Design Performance Analysis of Supercritical CO2 Cycle for CSP Application With Sensible Heat Thermal Storage

Supercritical CO2 (sCO2) cycles can achieve higher efficiencies than steam Rankine cycles at a higher temperature with a compact plant footprint. Concentrated solar power plants are capital intensive, as there is no fuel-related operating cost, the capital cost must be reduced to realise a reduction in the levelised cost of electricity. Power cycle efficiency and the temperature difference between the hot and cold storage tanks are the critical thermodynamic parameters to reduce the size and the cost of solar field and two-tank storage system whilst the power cycle specific power has also to be maximised to lower the power block cost. With these objectives, three potential cycle configurations were selected for detail assessment; a recompression cycle, partial cooling cycle and a partial heating cycle. A set of performance maps are presented using multi-objective optimisation, which maximises the efficiency and the specific power is explored for five different compressor inlet temperature of 35°C, 40°C, 45°C, 50°C, 55°C and two turbine inlet temperatures of 600°C and 700°C. The overnight capital cost across the Pareto front are estimated and the economic performance map is presented, which guides in selecting an optimal design for different boundary conditions.

An Update on the Status of a Reduced Flow Test of a 10mw 700°C sCO2 Integrally Geared Compander

In order to maintain viability as a future power-generating technology, concentrating solar power (CSP) must reduce its levelized cost of electricity (LCOE). One component of solving this problem is reducing the cost of the power block while simultaneously increasing the efficiency of the thermodynamic cycle. One disruptive technology that has the promise to accomplish this is supercritical CO2 based power cycles. These cycles are conceptually similar to steam cycles; however, they have substantially smaller turbomachinery at equivalent power while also delivering more efficiency at turbine inlet temperatures of 500–700°C. This paper will summarize the current status of a US Department of Energy project to develop machinery to support a 10 MW sCO2 power cycle. The team of Southwest Research Institute® (SwRI®) and Hanwha Power Systems America, proposed to develop an integrally-geared (IG) compressor-expander (compander) for use in a nominal 10 MW-scale CSP supercritical carbon dioxide (sCO2) plant application. This integrally-geared compander (IGC) comprises multiple pinion shafts interconnected on a single bull gear to create a compact package, and utilizes a low-cost, low-speed driver. In addition, the integrally-geared architecture allows each pinion to operate at different rotational speeds to optimize performance and easily allow for inter-stage cooling and turbine re-heat to further enhance both stage and cycle efficiency. The close integration of all turbomachinery elements into a single integrally-geared (IG) machine creates a design that lends itself to power block modularization, which makes it suitable for waste heat recovery, fossil fuel power plants, and especially CSP applications. As part of the commercialization of this technology, it is necessary to reduce risk by validation testing of key components. In the current work, the focus is developing a test loop to enable safe testing of the main compressor stage across a wide range of operating conditions, and to validate the mechanical integrity of the turbine at full pressure, temperature, and speed. Developing a test loop for sCO2 requires balancing a number of design alternatives that impact cost, lead time, safety, and performance. The current work discusses the design process for the reduced flow test loop for the compander.

Cost Effective Options of Closed CO2 Cycles for CSP Applications

Electrical power production from CSP is worldwide still limited in its diffusion by a higher LCOE with respect to other renewable sources, nevertheless it offers some unique features such as the possibility of a reliable energy storage capability. Among the most interesting, emerging-to-industrial ready technologies, CO2 power cycles seem to have the potential to provide a major step toward the average plant efficiency and equipment cost levels needed to achieve the marketability. Today, in most cases, supercritical CO2 power loops are seen as an opportunity to achieve a major step in thermodynamic efficiencies if applied in supercritical condition and with a quite complicated cycle configurations (e.g. Recompressed and ReHeated, or other combined solutions), with cycle maximum temperature above 650°C. Current cycle configurations are affected by a relative complexity of the power block, including non-negligible technological uncertainties with respect to simpler Brayton cycle solutions, possibly causing delay in the commercial application of the CO2 power block, at least for CSP applications. The aim of this article is to present some possible CO2 power closed cycle solutions, including supercritical as well as transcritical options, in order to propose cost-effective alternatives to current state-of-the-art steam power block of CSPs, highlighting that relatively simple CO2 cycle arrangements can enhance CSP competitiveness, representing a valid intermediate step towards next more advanced sCO2 cycles.