FIELD OF THE INVENTION

The present invention relates to a sensor network or system, e.g. for the purpose of monitoring and/or detecting physical parameters at storage sites.

BACKGROUND OF THE INVENTION

There is in many situations a need for monitoring physical parameters such as temperature over a long distance. Some examples are fire detection in tunnels, pipelines or high power electrical cables. Other applications are large area monitoring of recycling materials, waste storage and/or biofuel storage.

Fire is a frequently occurring problem in bio fuel processes and at storage sites. Such fires are difficult to predict and notice in an early stage, and they can go on for weeks or even months before it is noticed. They may spread out of control and generally imply high cost for firefighting as well as the loss of the fuel itself. The surroundings are typically affected by odor and harmful smoke.

Cable sensors have been in use for more than 40 years, wherein the first applications were fire detection in tunnels. Other applications are fire detection in petrochemical plants and pipelines. Early adoptions of the technique utilized for example a polymer material that would melt and short circuit cables at a specific temperature. The short circuit point could be localized thus providing the position of the area of elevated temperature. Furthermore, high sensitivity calorimeters are used as well as opto-cables based on laser sensing technologies, whereas digital electronic

communications have been introduced later. However, in general, more than two parallel wires are needed in the cable. Separate wires may be provided for power supply, data transmission and addressing which sensor to collect data from. Manually handled systems are available on the market today, but it will be appreciated that that there is a need for an installation of a robust and automatic system with a long lifetime, which furthermore does not disturb the daily work going on at the plant.

SUMMARY OF THE INVENTION

The prior art has drawbacks regarding its ability to provide robustness, reliability, long life time, combined wired and wireless sensors and being an easy-to-install solution for sensor system.

The object of the present invention is to overcome the drawbacks of the prior art. This is achieved by providing a sensor system having the features in the independent claim, and wherein preferred embodiments are defined in the dependent claims.

According to the present invention, there is provided a sensor system for a storage. The sensor system comprises at least one cable with at least one integrated sensor node, i.e. at least one sensor node is integrated in the cable. The at least one integrated sensor node is configured (is able) to detect, localize and/or communicate with at least one sensor node provided outside the at least one cable. It will be appreciated that the drawbacks of the prior art may further be overcome e.g. by a communication arrangement in each sensor node, a low power consumption and the positioning of the sensor cable in combination with the capability to include wireless sensors. Thanks to the invention it is possible to obtain a permanent installation with a long life time, and which is suitable for a storage of recycling materials, solid waste and/or solid bio fuel.

It will be appreciated that a suitable technology for a monitoring of recycling materials, waste storage and/or biofuel storage is the cable sensor. At many positions along the cable there are embedded sensor elements which measure the temperature or other physical parameters. The sensor elements may transmit the data on the cable to a master unit located at one or both ends of the cable. The typical length of the cable is from a few meters up to many kilometers. The number sensor elements are up to several hundreds. In a network of multiple temperature sensors, they are with advantage placed both in the ground and embedded in the waste fuel in the form of wireless sensor nodes. These provide early information about increased fire hazard as well as information on how the fire spreads.

Thanks to the invention it is possible to monitor e.g. smouldering, fire ignitions, self heating, micro biological activities and/or gases.

It is a further advantage of the invention to provide a solution to detect and monitor e.g. pollution from landfill sites, analysis of leachate water as well as concentrations of greenhouse gases and dust.

It is a yet further advantage that the same main unit can talk

(communicate) with both the cable sensors (i.e. the integrated sensor nodes) as well as the (wireless) sensors, e.g. being distributed in a pile. It also enables a simple way to localize the wireless sensors as well as it helps overcoming the damping of wireless signals caused by the solid materials being stored.

In a second aspect, the two or three wire cable enables a cost effective manufacturing of cable with integrated sensor nodes.

In addition, the invention helps overcome difficulties with sensor integration for users coming from areas such as agriculture, landfill, wood chip plies, pellets storage, solid waste storage, conveyor belts, cable tunnels, silos, traffic tunnels, and the oil and off-shore industry.

According to an embodiment, the at least one integrated sensor node comprises a communication arrangement for the communication with the at least one sensor node.

According to an embodiment, the sensor system is connected to a main unit and a mobile modem, and the sensor system is configured (able) to communicate with one or more mobile phone(s) and/or with the Internet.

According to an embodiment, the sensor system is configured to read signals from sensor nodes (provided outside the cable) connected to solar cells.

According to an embodiment, the at least one cable has a maximum of three wires being connected in parallel to a multiple of integrated sensor nodes. According to an embodiment, the integrated sensor nodes comprises a multiple of sensor types in the same at least one cable.

According to an embodiment, the at least one integrated sensor node comprises a multiple of chemical sensors for chemical substance detection.

According to an embodiment, the chemical sensors are configured to detect concentrations of gases such as oxygen and/or carbon oxides.

According to an embodiment, the at least one integrated sensor node has a multiple of moisture level detectors.

According to an embodiment, the at least one integrated sensor node comprises one or more transient hot strip sensors.

According to an embodiment, the at least one cable does not comprise any transformers nor inductive components needed for the data

communication to the master unit.

According to an embodiment, the at least one cable has more than one integrated sensor node being protected with at least, but not limited to, a polymer and a metal.

According to an embodiment, the at least one cable is embedded in the ground under a pile of recycling material, solid bio fuels and/or waste material.

According to an embodiment, there is provided a sensor system arrangement, comprising a sensor system according to any of the preceding embodiments, and at least one sensor node provided outside the at least one cable, wherein the at least one integrated sensor node is able to detect, localize and/or communicate with the at least one sensor node provided outside the at least one cable.

According to an embodiment, a plurality of sensor nodes are positioned in a material to be stored.

According to an alternative embodiment, the at least one cable has at least one sensor element module comprising a microprocessor with a current consumption of 1 -100 μΑ.

Other objects, advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings and claims. DETAILED DESCRIPTION OF THE DRAWINGS Preferred embodiments of the invention will now be described with reference to the accompanying drawings, wherein:

Fig 1 is a schematic illustration of a sensor cable (of a sensor system) comprising a main unit, a cable and (integrated) sensor nodes according to an embodiment of the invention;

Fig 2 is a schematic illustration of the wired sensor node according to an embodiment of the invention; and

Fig 3 is a schematic illustration of a sensor system arrangement comprising an embedded sensor cable and wireless sensor nodes according to an embodiment of the invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The cable 1 is a two-wired or three-wired cable, and in most cases it is a ruggedized cable for employment in harsh environmental conditions. Each sensor node 2 in the present invention may consist of a small sized electronics module 3 being integrated in the cable. The cable 1 further comprises an outer jacket 4. The sensor node includes a (relatively) small microprocessor, an analog-to-digital conversion and a sensing element. In the case of temperature measurement the sensing element is typically a temperature sensitive resistor. The system has a two-way data

communication between the master unit 6 and the sensor elements in the cable, by means of voltage shift of the voltage between the wires.

Each sensor element module is powered by a current drawn from the cable. Since the number of sensor elements can be in the order of many hundreds, the current drawn by each of the sensor element modules is low.

The sensor node 2 typically contains a FET transistor 7, a resistor 8 together with an electrical circuit 9 of a micro-processor, an analog-digital converter, a sensor element, wired communication, an antenna and wireless communication. It will be appreciated that the communication arrangement of the (integrated) sensor node may comprise one or more of these

elements/devices. The FET transistor 7 senses incoming data triggered by a voltage change between the cable wires 5. The load resistor 8 is used for transmitting wired data onto the cable by pulling down the voltage between the cable wires.

Sensor elements are built on different technologies and are often commercially available. The same type or a multiple type of sensors are integrated in the one or more cables. The so called transient hot strip method is used to measure thermal properties of surrounded materials. A temperature dependent resistor is used to measure changes in temperature other than what is normal.

The sensor cable can interact with the wireless sensor nodes 9 and localize them individually, as they are positioned inside a storage pile of easily ignitable material 10 which can be - but is not limited to - recycling materials, waste materials, bio fuel and/or dust. The sensor cable is typically embedded on the ground 12 under the storage pile 10 in a foundation material 1 1 . The foundation material can be - but is not limited to - asphalt, gravel, concrete, cement, soil or grass.

The cable sensors nodes 2 and/or the wireless sensor nodes 9 which may be located at distances from 0.1 to 10 meter from the cable, can detect temperature, moisture, chemicals and/or thermal properties in the

surroundings. The chemicals are typically methane, carbon oxides, nitrogen oxides, oxygen, smoke and water. The sensor element include sensors to measure chemical concentrations, gas concentrations of for example oxygen, carbon oxides and methane and/or moisture levels.

In one embodiment, the system is connected to a main unit and a mobile modem, and is able to communicate to one or more mobile phone(s) and/or to the Internet.

In one embodiment, a sensor system for storage, based on cables with integrated sensor nodes, is also able to communicate with wireless sensor nodes. The sensor cable is localized close to the material to be stored, typically embedded in the ground surface, on a sidewall and/or in the roof. It contains several integrated sensor nodes with the advantage of having the capability to also act as the link to further detect, localize and to communicate with wireless sensors to be included in the system. This forms a (relatively) large sensor network with sensors both integrated in the cable and which are placed or randomly positioned in the larger surroundings to the cable. The wireless sensor nodes are automatically detected and localized.

In one embodiment, the sensor cable has a large number of parallel connected integrated sensor nodes. It uses a two-way data communication between the master unit and the integrated sensor nodes by means of voltage shift of the voltage between the wires. The power consumption, the data rate and the update frequency are all very low.

According to embodiments, the sensor cable has the advantage of a dual use and can also act to detect, monitor and to localize wireless sensors in the surroundings.

According to embodiments, the sensor cable has one or more sensor nodes molded in polymer or reinforced polymer.

According to embodiments, the sensor cable is installed such that it is embedded in solid ignitable material.

According to embodiments, the sensor cable has only three electrical wires to the main unit.

According to embodiments, the sensor cable is used to monitor fire ignitions.

According to embodiments, the sensor cable is used to monitor micro biological activities or exoterm reactions.

According to embodiments, the sensor cable is used to monitor gases.

According to embodiments, the sensor cable is used to monitor concentrations of greenhouse gases.

According to embodiments, the sensor cable is used to detect and to monitor pollution from landfill sites.

According to embodiments, the sensor cable is used for chemical analysis of leachate water.

According to embodiments, the sensor cable is powered by solar cells. According to embodiments, a (relatively) large number of wireless sensor nodes are positioned and left/kept in stored material during its life time. The sensors will actually be stored at different locations and the sensors follow the material all the way to final destination that typically is combustion.

ITEMIZED LIST OF EMBODIMENTS

Item 1 . A sensor system for storage, based on cables with integrated sensor nodes also able to communicate with wireless sensor nodes. The sensor cable is localized close to the material to be stored, typically embedded in the ground surface, on a sidewall and/or in the roof. It contains several integrated sensor nodes with the advantage of having capability to also act as the link to further detect, localize and communicate with wireless sensors, to be included in the system. This forms a large sensor network with sensors both integrated in cable and randomly positioned in the larger surroundings to the cable. The wireless sensor nodes are automatically detected and localized.

The sensor cable has a large number of parallel connected integrated sensor nodes. Besides sensors and intelligence, each sensor node has its own communication arrangements, everything being integrated in the cables. It uses two-way data communication between the master unit and the integrated sensor nodes by means of voltage shift of the voltage between the two wires. To enable a large number of sensors and a long length of cable, the power consumption, the data rate and the update frequency are all very low.

Item 2. A sensor system according to item 1 , where large number of wireless sensor nodes are positioned and left/kept in stored material during its life time, it will actually to be stored at different locations and the sensors follow the material all the way to final destination that typically is combustion.

Item 3. A sensor cable according to item 1 , with only 2 wires connected to a multiple of sensors Item 4. A sensor system according to any of items 1 -3, connected to main unit and mobile modem, and communicating to mobile phone and/or internet.

Item 5. A sensor cable according to item 2, reading signals from wireless sensor nodes connected to solar cells

Item 6. A sensor cable according to item 1 , with maximum 3 wires, being parallel connected to a multiple of sensors

Item 7. A sensor cable according to any of items 1 -3, with multiple of sensor types in same cable

Item 8. A sensor cable according to any of the preceding items, with a multiple of chemical sensors

Item 9. A sensor cable according to any of the preceding items, with chemical sensors for concentrations of oxygen and carbon oxides

Item 10. A sensor cable according to any of the preceding items, with a multiple of moisture level detectors.

Item 1 1 . A sensor cable according to any of the preceding items, with one or more transient hot strip sensors.

Item 12. A sensor cable according to any of the preceding items, with sensor element module comprising a microprocessor with current

consumption 1 -100 μΑ.

Item 13. A sensor cable according to any of the preceding items, with no transformers or inductive components needed for the data communication to master unit.

Item 14. A sensor cable according to any of the preceding items, with typical data transmission rate between 10 to 1000 bit/s.

Item 15. A sensor cable according to any of the preceding items, with length from 10 to 10000 meters.

Item 16. A sensor cable according to any of the preceding items, with more than one sensor node being protected with at least, but not limited to, polymer and metal.

Item 17. A sensor cable according to any of the preceding items, embedded in ground under pile of solid bio fuels or waste material.