Integration of Concentrating Solar Heat into Oil and Gas Operations for Increased Sustainability

According to Eni's mission to reach carbon neutrality in the countries where it operates, the development of renewable energy could be a key element in the company's strategy for evolving the business model towards a low carbon scenario. In this context, concentrating solar technology can provide a real solution in order to goal the carbon neutrality. Solar thermal energy could be an alternative source to the fossil fuel in industrial processes and also in the oil&gas sector, where the upstream operations (dewatering, stabilization, sweetening…) require substantial amounts of heat. Usually this heat is easily produced by combustion of natural gas available at the oil&gas site. Concentrating Solar Heat (CSH) technology allows to produce process heat by using specific collectors that concentrate the solar radiation onto a receiver where a heat transfer fluid is heated at medium/high temperature. A thermal energy storage can be added to the solar field to increase the solar fraction and reducing so the CO2 emissions. The fraction of thermal energy not covered by the CSH plant can be provided by a fossil source that acts as a back-up. With this in mind, a pre-feasibility study was carried out for the integration of a medium temperature(∼200-300°C) concentrating solar plant with or without a thermal storage system and a back-up gas heater in an oil&gas site located in North Africa. The solar heat partially replaces the duty necessary to the heat exchangers that heat the crude to guarantee the separation from water and best stabilization. Reflective areas of the solar field and total occupancy, thermal energy production during the year, solar multiple and preliminary evaluations of cost of investment are presented. Obviously, the reduction of CO2 emission increases with the solar fraction but the competitiveness and cost-effectiveness of the integration strongly depend on the local cost of natural gas, the presence of government incentives, CO2 credit tax, etc. In any case the proposed solution represents an important step towards energy transition.

Research on a Solar Hybrid Trigeneration System Based on Exergy and Exergoenvironmental Assessments

The environmental performance of a combined cooling, heating, and power system is analyzed in this study at a component-level using a SPECO-based exergoenvironmental analysis. The engine consumes natural gas and produces 168.6 kW net power. The waste heat is recovered by a LiBr-H2O absorption chiller and a heat exchanger, which are used for cooling and heating purposes. The energy system is assisted by a solar field. An environmental Life Cycle Assessment quantifies the environmental impacts of the system, and these data are combined with exergy evaluations. The highest total environmental impact rate, 23,740.16 mPt/h, is related to the internal combustion engine, of which pollutant formation is the primary source of environmental impact. Compared with a non-renewable energy system, the solar-assisted trigeneration system decreased the environmental impact per exergy unit of chilled water by 10.99%. Exergoenvironmental performance can be further improved by enhancing the exergy efficiency of the solution pump and high-pressure generator (HG), and by employing a treatment to remove nitrogen oxides in the reciprocating engine.

Modeling, Implementing and Evaluating of an Advanced Dual Axis Heliostat Drive System

Heliostat tracking is a critical component of the solar field of concentrating solar power tower (SPT) systems and can be the source of significant losses in power and profit when it lacks the necessary accuracy. This paper presents an advanced heliostat drive system for the SPT generation plant. An integrated model for the heliostat drive system based on dual axes tracking is proposed using an inexpensive angle sensor. The mathematical model of the integrated drive system is developed, including the solar, tower, and heliostat models. The MATLAB simulation model for the proposed integrated drive system is developed and evaluated. An experimental prototype for a dual-axis heliostat is built using Class-E DC choppers and an inexpensive Gyro angle sensor. The prototype is tested and considered in the Dhahran region in Saudi Arabia under different operating conditions. A comparative study between simulation and experimental results is conducted to assess the efficacy and accuracy of the proposed controller drive system and validate the developed integrated model. Both simulation and experimental results demonstrate the effectiveness of the proposed dual-axis trackers to follow the sunbeams throughout the year.

Design and performance analysis of solar-coal-fired complementary power system based on the S-CO2 Brayton cycle

To make solar energy conversion more effective and enable effective complementary utilization of multiple energy sources, two types of solar-coal-fired complementary power (SCCP) systems, which use the supercritical CO2 (S-CO2) Brayton cycle, are investigated and their layouts improved. In addition, a thermodynamic performance analysis is carried out. The results show that, as the amount of work done by the solar energy module increases, the coal saving rate increases linearly and proportionally in both SCCP systems. Also, the supplementary electric power generated by the solar field increases. The two improved layouts increase the net efficiency of the SCCP systems significantly (SCCP1: from 43.60% to 47.65, SCCP2: from 43.60% to 47.67%). More specifically, the net efficiency of the improved layout for SCCP2 increases faster than that for SCCP1 (with its improved layout), when the second split ratio (SR2) exceeds 0.031. When the net efficiency remains unchanged, the SR2 for SCCP2 improved layout has a wide range. Furthermore, both the operation performance and operating-mode conversion of the basic system are studied for varying sunlight-conditions. The simulation results are consistent with the expectations, which underlines the development potential of the system to a certain extent.

NUMERICAL INVESTIGATION OF A SOLAR-DRIVEN ORGANIC RANKINE CYCLE COUPLED TO A GEOTHERMAL FIELD

The objective of this work is to investigate a solar-driven Organic Rankine Cycle (ORC) for power production with a geothermal well as the heat sink for the ORC condenser. The examined unit combines the exploitation of two renewable energy sources. Solar irradiation is exploited by using solar dish concentrators with spiral absorbers, while the geothermal field includes vertical boreholes with U-tubes. The system is investigated parametrically with a developed model in Engineering Equation Solver, and the examined parameters are the solar beam irradiation level, the total thermal conductivity of the ORC condenser, the borehole length, the number of the boreholes and the mean ground temperature. For the default scenario, it is found that system electrical efficiency is 21.45%, the ORC’s thermodynamic efficiency is 35.99%, and the solar field efficiency is 61.30%. Moreover, it is found that the examined system is 5.7% more efficient than a conventional air-cooled condenser system.

State-of-the-Art Measurement Instrumentation and Most Recent Measurement Techniques for Parabolic Trough Collector Fields

The presented review gives reliable information about the currently used measurement instrumentation in parabolic trough fields and recent monitoring approaches. The usually built-in measurement equipment in the solar field, clamp-on systems for flexible measurements of temperature and flow, solar irradiance measurements, standard meteorological equipment, laboratory devices for heat transfer fluid analyses and instruments related to the tracking of solar collector assemblies are presented in detail. The measurement systems are reported with their measurement uncertainty, approximate costs and usual installation location for the built-in instrumentation. Specific findings related to the installation and operation of the measurement devices are presented. The usually installed instrumentation delivers a lot of measurements all over the field at the expense of measurement accuracy, compared to special test facility equipment. Recently introduced measurement approaches can improve the standard instrumentation in terms of accuracy, frequency, spatial distribution or can even extend the amount of measurands. The information about available measurands is the basis for future operation and maintenance solutions based on data-driven approaches.

Solar Energy as an alternative source in boiler economizers

This study sought to analyze the viability of the use of solar energy, for the operation in boiler economizers, in the replacement of the thermal energy of the exhaust gases. The experiment was divided in two steps: analysis of the boiler yield with different feed water temperatures and addition of the solar field to the initial set. For the modeling of the economizer-boiler set, the software used was Engineering Equation Solver (Software F-Chart, Wisconsin, USA). The technology chosen for the second stage was the high-pressure vacuum solar collector, installed at the inlet of the feed water heater. The thermal power of 2014W (per plate) and the solar radiation peak of 1000W / m² were standardized, taking into account the calculations for a steady state system at noon. The variable was the number of solar panels to be used at the plant. After analyzing the data, it was verified that the efficiency varied by approximately 7.4%, when the feed water temperature was increased by 20 ° C, close to 48 ° C. In order for this variation to occur, it was necessary to use 50 plates.