Traditionally, geothermal plants have been located in areas where hot springs and other indicators of thermal activity can be seen at the surface. However, enhanced geothermal systems (EGS) may also be used in areas where hot rock is found at reasonable depths. To achieve geothermal energy, fluid is injected into the drilled wells, heated by contact with the hot rock, and removed to power turbines at the surface. The majority of EGS utilize steam turbines to convert geothermal energy into electricity.
Under the constant pressures to lower operational costs and raise the effectiveness of the EGS, a number of parameters need to be managed to ensure high efficiency and competitive electricity prices. The efficiency of a geothermal plant is entirely reliant on the amount of steam that can be retrieved from the well, therefore, the subsurface reservoir must be able to provide quality geothermal fluid in sufficient quantities over its service life.
In order to retain the needed pressure in the well and to extend its service life, geothermal fluid achieved by hydraulically fracturing the hot rock is re-injected. Consequently, it is crucial to understand where the fluid is going inside the well and where the fluids come from.
It is well known and documented that the use of distributed temperature sensing in geothermal energy applications has greatly improved the reliability and longevity of EGS. Distributed temperature sensing systems can also be combined with other sensors, like FBG pressure sensors, to provide a complete data set. The information – subsurface temperature and pressure – can be used in various ways, such as:
1. Estimation of the production potential in the new wells be measuring the temperature at the point of pressure
The rate at which the fluid pressure drops after the operator opens the tap at the surface allows the calculations of reservoir size, flow resistance between wells, well completion, etc.
2. Monitoring of the surface and subsurface scale buildup and chemical cleanup
The buildup of scale – a mineral residue precipitated from the geothermal fluid – can inhibit fluid flow and block a pipe. A better understanding of the severity of the scaling may improve the choice of mitigating options.
3. Integrity monitoring for casing and tubing leaks.
The compromised integrity of the casing and tubing may lead to contamination of ground and subsurface aquifers.
An installed DTS system provides many additional monitoring opportunities. The efficiency of the geothermal plants may be greatly improved by combining temperature data with subsurface point pressure data. Distributed temperature sensing channels may be added to monitor surface processes. Another geothermal energy application of DTS systems in localization of overheated areas that allows mitigating the hotspots.
If you would like to purchase DTS (Distributed Temperature System), please contact us: info@optromix.com or +1 617 558 98 58
Temperature sensors in energy systems
In the modern world, the increasing electricity consumption and high demand for energy lead to an increase in stress on the power cables that often reach their physical limits. This affects the safety of power lines and their efficiency. To combat these issues, real-time thermal ratings may be implemented to observe the thermal behavior of cables and calculate their operational limits. The knowledge of these parameters is key to control the safety and efficiency of power lines, as unforeseeable thermal conditions do, in fact, lead to system degradation and capacity reduction. Real-time thermal rating aid in saving maintenance time, optimization of resources, and improving the efficiency of power lines.
Real-time thermal ratings may not only assist in perfecting already existing energy systems but also to integrate alternative power sources, such as wind energy systems. To improve the wind energy infrastructure and to further integrate renewable energy sources into mainstream energy production, the reduction of restrictions placed on wind energy is necessary for elevating the efficiency of such systems. The following measurements are required in order to implement real-time thermal ratings into the network: wind speed, thermal state estimations, temperature, and voltage measurements. The combination of these variables creates real-time ratings for wind energy systems.
The evaluation of said measurements provides crucial information on the ways in which wind energy capacity may be increased. For example, an implementation of thermal ratings that was conducted in 2010 revealed that the cooling effect of wind significantly affects wind power lines and may potentially lead to an increase in their electrical capacity up to 30%.
These results proved to be significant to the field and provided valuable insight into the generation capacity and its potential increases. It is expected that real-time thermal readings will allow for increased integration of wind energy into the distribution network.
Fiber Bragg temperature sensors are insensitive to changes in the environment, which is important for wind energy generators, and have a long reliability period. If you would like to purchase Optromix FBG Temperature Sensors, please contact us: info@optromix.com or +1 617 558 98 58.
Distributed temperature sensors in experimental hydrology
Distributed temperature sensors are usually used in industrial applications, such as process control and infrastructure monitoring; however, in the past couple of years, fiber optic distributed sensors have been used in ecological monitoring. The ability to measure temperature in time and space simultaneously allows distributed temperature sensors to be used in groundwater detection, rainforest ambient temperature monitoring, stream temperature monitoring, and more.
Temperature sensing is one of the most significant methods of experimental hydrology as it provides valuable insight into the flow dynamics of different types of water bodies. The water temperature is determined by measuring the Stokes/anti-Stokes ratio of reflected light that was produced by sending a laser pulse through the cable. The cable is placed into the body of water to detect temperature fluctuations along the stream. The data density of distributed sensors allows to obtain high-resolution data and map temperature changes in the water with high accuracy, and the absence of electronic parts in monitoring zones makes distributed sensors safe to use underwater. High return speeds of such optic sensors are perfect for both fast-changing and subtle temperature changes that often occur in water. Moreover, distributed temperature sensors are extremely thin and are easy to use in shallow streams and wells, and resistance to corrosion determines their long life cycle even if used in harsh conditions.
The measurements obtained by utilizing distributed temperature sensors are then used to construct 3D temperature maps of water streams or to validate and refine existing models of water temperature fluctuations. This data assists in finding locations of groundwater sources and their contribution to the stream helps to better understand river ecosystems, determine the distribution of studied species and their migration paths.
Other fields that utilize distributed temperature sensors include healthcare and biomedicine fields, fire detection, oil and gas production, detection of leakages, pipelines integrity surveillance, and others.
Optromix company manufactures stainless-steel housed optic sensors that are tensile and impact resistant. If you would like to purchase Optromix FBG Temperature Sensors, please contact us: info@optromix.com or +1 617 558 98 58.
Fiber Optic Temperature Monitoring of Belt Conveyors
Major conveyor belt–related mining incidents are now relatively infrequent as a result of recent improvements in engineering standards and the use of fire-resistant materials. However, conveyor belts are still a potential cause of personal and structural damage. In addition, any unexpected breakdown of rolling components or failure of belts creates a significant interruption to production, which is a major concern for operators, who are responsible for achieving optimum mining production. This project aimed to develop a fiber optic-based distributed temperature sensing (DTS) system to monitor the temperature change of malfunction idlers for heavy-duty conveyor belts in underground coal mines.
Conveyor belts have been widely used for centuries to transport general goods, bulk materials, and passengers. Conveyor belts have attained a dominant position in the continuous conveying of bulk materials ranging from very fine, dusty chemicals to bulk materials, such as raw ore and coal, as well as for overburden, including stones, soil, and logs of wood. In comparison to other transportation methods for bulk solids, such as trains or trucks, conveyor belts are an extremely favorable choice in instances where suitable infrastructures for other modes of transport do not exist.
The main fire risks associated with belt type conveyors are as follows:
› Friction due to loss of belt traction and slipping on the drive roller;
› Welding activities can generate hot molten material;
› Overheated materials placed on the belt;
› Build up of materials that have fallen off the belt and dust cloud generation;
› Static electricity.Continue reading
Distributed fiber optic sensing (DFOS equipment) for oil & gas industry
Distributed fiber optic sensing (DFOS) presents a good ability for the oil and gas industry to operate and optimize its resources more effectively going forward. Expenses on DFOS by the oil and gas industry worldwide was $341.2m in 2015. The rise of expensive multilateral hydraulic fracturing, an ever-greater focus on improving oil recovery and the continued strength of capital expenditure on thermally enhanced oil recovery techniques provide the main markets for the uptake of DFOS over the next 10 years.
During the past five years distributed acoustic sensing (DAS) – one type of DFOS – has approved itself as a pipeline in-service surveillance and monitoring system. Moreover, distributed acoustic sensing as technology looks set to add value to DFOS monitoring solutions of wells and reservoirs. DTS (distributed temperature sensing) is already established as a well-monitoring technique and the complementary application of a DAS interrogation enhances the future business case. The last main type of DFOS equipment – distributed temperature and strain sensing (DTSS) – is competing for market share as well as being able to market itself as a solution that can anticipate structural problems with the oil and gas industry before they occur.
The application opportunities within the oil and gas industry for DFOS are poised to enable a substantive growth in spending on DFOS equipment. After well monitoring, permanent reservoir monitoring and seismic acquisition is an especially exciting venture market for DFOS, as is the use of fiber optics for monitoring offshore infrastructure and downstream process integrity. The use of DFOS as part of a 4D solution and vertical seismic profiling is the most deserving attention market space growth ability for DFOS equipment expenditure over the coming 10 years.
For emphasis: an oil price of $100 per barrel continues to enable exploration and production expenditure on unconventional oil and gas development, thermal enhanced oil recovery (EOR), and ever more IOR (Improved Oil Recovery) activity. Distributed fiber optic sensing is a part of this story: a tool to better the industry’s understanding of how to optimize recovery and improve development techniques.
Medical fiber optic sensing products and technologies
The range of medical devices incorporating optical fibers has taken a slow technological growth, with the bulk of the industry focused on endoscopy and various methods of optical power delivery for cutting, dissecting, and ablating. These technologies utilize an optical fiber’s mechanism—the ability to guide light from one location to another.
Fiber sensing technologies offer significantly advanced functionality by utilizing their inherent sensitivity to temperature, strain, and pressure. During the last five years, the medical industry has taken significant steps to adapt historic fiber-optic sensing methods to enable them to be used within in vivo environments.
The main area for recent technological developments driving fiber sensors into the medical industry has focused on minimally invasive surgery (MIS). The benefits of MIS are now well-founded, encouraging surgical-tool manufacturers to invest their money in new technology developments to pioneer new MIS procedures or to further improve existing procedures. Three exciting recently developed fiber optic sensing technologies for MIS are focused on here: haptic feedback, 3D shape sensing, and pressure sensing.
By utilizing multiple FBGs or manipulating the FBG structure, it is possible to obtain a spatially distributed strain profile. Such FBGs can be applied along the length of a surgical tool to enable haptic feedback at the regions of most concern. A prime example of this is to add haptic sensing to a grasping tool, where both the grasping and spreading forces can be measured and fed back to the surgeon to indicate how tightly they are grasping or how much force they are applying to pry tissues apart.
Fiber optic 3D shape sensing has been developed by several commercial groups to enable a dramatic reduction in the need for prolonged exposure to the visualization methods, as the optical fiber can track itself in three dimensions and thus if laid within a catheter, can recreate the shape of the catheter. This technique relies on a mixture of FBG and fiber technology, where a very special fiber has been developed specifically for this application. Optical fibers also can be optimized to be sensitive to the hydrostatic pressures experienced within the body. These new applications are being opened up by a mixture of economic desire and technology development. Specialty optical-fiber manufacturers continue to pioneer new fiber designs that medical-device manufacturers can exploit. This enables a greater diversification of medical-device product ranges and opens up new procedures that were not previously possible with minimally invasive surgery.
Distributed Temperature Sensing (DTS) system resolution
The main idea of the Distributed Temperature Sensing is Raman-based temperature measurement joined with Optical Time-domain Reflectometry (OTDR). A short pulse of light is enabled into the fiber. The propagating light creates Raman backscattered light at two wavelengths, from all points along with the fiber. The wavelengths of the Raman backscattered light are different from that of the forward propagating light and are named “Stokes” or “anti-Stokes”.The amplitude of the Stokes light is not very dependent on temperature, while the amplitude of the anti-Stokes light is strongly dependent on temperature.
A typically distributed sensing system is described by the spatial and temperature resolution. The spatial resolution is the minimum distance of the sensor to measure a step change in temperature along with the optical fiber. The temperature resolution is a measure of the precision to distinguish the absolute temperature. The temperature resolution depends on the measurement time and the launch pulse-recurrence rate. The laser pulse energy and duration are accurately controlled and optimized at the measurement maximum length to provide the best available temperature resolution within acceptable accuracy limits. As the sampling time is increased, the temperature resolution is improved and resolved temperatures become more accurate.
The report “Distributed Temperature Sensing (DTS) Market 2016 – 2023,” points out the key factors impacting the growth of this market and assesses its growth during the period between 2016 and 2023. Fiber optic sensing is challenging because the physical properties of light into the fiber are affected by strain, temperature, or sound. Several technologies enable local measurement – using sensors at chosen points along with the fiber (eg, fiber Bragg grating (FBG) technology for measuring localized pressure, strain, temperature, and flow) – or distributed sensing – with sensing occurring all along with the fiber.
Distributed sensing systems have been developed for the oil and gas industry to assist reservoir engineers in optimizing the well lifetime. Nowadays they find a wide variety of applications as integrity monitoring tools in process vessels, storage tanks, and piping systems offering the operator tools to schedule maintenance programs and maximize service life.
Optromix Company offers a Distributed fiber optic sensing system with high spatial and temporal profiling over large surfaces, long lengths, and at locations where conventional point sensing is not applicable or costs effective.
What is DTS?
A distributed temperature sensing system (DTS) is a device made to monitor power cable with fiber optic temperature sensors. DTS measures temperature on the large distances, greater than 30 km. It records the temperature along the cable as a continuous profile. DTS spatial resolution is 1 m with accuracy within ±1°C at a resolution of 0.01°C.
Adding RTTR to distributed temperature sensors allows achieving more precision when measuring high-temperature wire. DTS has some level of uncertainty when it detects the temperature, and its level increases when the conductor operates in an emergency situation. This happens because the conductor heating is detected with the time lag. Also, the temperature differs depending on the loading level. The higher the loading level is, the less precise are the measurements.
What is DTS measuring principle?
Certain factors, such as temperature or pressure, affect the optic cable and change the light transmission characteristics in the fiber. Optical fibers operate as linear temperature sensors when the light is projected in it through scattering to determine the location of the physical effect on the outside.
Optical fiber is made of doped quartz glass, silicon dioxide and has an amorphous solid structure. Its molecules interact with the photons when light falls on the thermally excited molecular oscillations. This process leads to light scattering, also called Raman scattering. The difference between the incident light and scattered light is that the later experiences a spectral shift that is equivalent to the lattice oscillation resonance frequency. The scattered light has three spectral shares, namely the Rayleigh (laser source wavelength scattering), the Stokes line components (lower frequency), and the anti-Stokes line components (higher frequency). Anti-stokes depend on the temperature, hence it is possible to calculate the fiber temperature as a ratio between anti-Stokes and Stokes line components.
What is DTS used for?
Distributed temperature sensing has multiple applications in different industrial segments to monitor power cables, tunnels, and industrial buildings, to detect leakages, and to control high-temperature wires. Recently DTS has been applied in monitoring ecological factors, such as groundwater, rainforests, river streams, etc.