FIELD OF INVENTION

The present invention relates to a wireless sensor network that is capable of harvesting ambient energy.

BACKGROUND OF INVENTION

In the agriculture and plantation industries, one of the main factors that affects yield is the environment - conditions of the surrounding soil and air. Humidity, temperature, soil type and fertilizer quantity, acidity and moisture level are all important for optimum plant well-being. Therefore, these environmental parameters need to be monitored and controlled to achieve plant health and high productivity. The ability to monitor accurately the environmental conditions on a plantation will drastically reduce crop failure and downtime, thus increasing yield.

One problem when seeking to monitor environmental conditions in agriculture arises due to the sheer size of the plantation area that needs to be covered. A great number of sensors are needed to evaluate environmental conditions to an adequate resolution. Because of this, connecting all these sensors to a central control becomes quite impractical. Hitt (US 2004100394) describes a system whereby all the individual sensors communicate to the central control wirelessly, thus eliminating the need for hundreds of miles of wiring. However, the spread and distance between the sensors make it difficult to supply power to each and every one of them, and in a wireless system there is no means of drawing power from a central source. The traditional solution of using batteries is time consuming and involves a great deal of downtime when having to replace a dead battery. If the batteries are replaced on a regular basis to prevent this downtime, this causes wastage of battery life. There is therefore a need for a solution that does not involve the need for regular changing of batteries, and in effect allowing the sensor network to be autonomously powered.

Bocko (US 6,747,572 B2) describes a method of harvesting available thermal energy from the system for conversion into electrical energy for use in a wireless network. The method described in this patent requires heat to be available from the system. Should there be no heat available for any reason, there will be no energy generated and the wireless sensor network will not operate.

What is needed in the art is a system that is completely autonomous, and capable of continuous operation without the need for a dedicated power supply.

Yet another problem faced by these large sensor networks is the scalability of the power supply. The system consists of several layers, with the components in each layer requiring a different amount of power. This may be difficult to achieve if all the power was coming from one or even a few main sources. What is needed is a system that is able to supply microwatts of power to the smallest component as well as miliwatts and watts of power to the bigger components.

SUMMARY OF INVENTION

The present invention relates to a wireless sensor system that is predominantly powered by the harvesting of ambient or environmental energy such as wind, solar, thermal, vibration or radio frequency (RF). The energy harvesters generate electrical power for use in sensor motes that are spread out at large distances, thus eliminating the need to deliver power to each individual sensor mote from a central source. The sensor motes comprise of sensors that generate data signals based on various environmental parameters measured, as well as wireless transmitters that send the data signals containing the sensor measurements to a router located in the vicinity. The routers are also powered by energy harvesters, albeit with a larger power output to match the higher requirement. The routers act as wireless relays and further transmit the data signals to a collector. This collector is typically located in a central location such as a farmhouse where it can draw power from available sources and hence does not require energy harvesting.

The present invention also relates to a compact sensor powered by an ambient energy source, wherein measured environmental data is transmitted to a collector via an optional router, without requiring a wired interconnection. This allows increased spatial distribution of sensors, a great advantage in the agriculture industry, while reducing installation costs. The autonomous sensor system can be customized to measure any of a variety of environmental parameters, including but not limited to air humidity and temperature, and soil acidity, fertilizer profile, and moisture levels. The system includes a plurality of energy harvesters for converting ambient energy from the environment into electricity. The generated electricity is used to power a sensor and transmit a corresponding signal via a transmitter.

This invention also relates to a wireless sensor mote comprising: an energy harvester that harvests energy from any one of: a) wind; b) solar; c) vibration; d) radio frequency; and e) thermal; a sensor for sensing an environmental parameter and generating a signal based on said sensing, said sensor powered by energy from said energy harvester; a rechargeable battery for providing storage of energy received from the energy harvester and for the powering of said sensor; and a wireless data transmitter for transmitting said signal over a wireless network, said wireless data transmitter powered by energy from said energy harvester characterized in that said energy harvester is capable of generating electrical energy by harvesting ambient energy from the environment.

This invention also relates to a sensor network comprising: a cloud having a plurality of autonomous wireless sensor motes, and a router adapted to receive wireless data transmission from each of said wireless sensors motes and to transmit wireless data; an energy harvester for providing power to the said routers; and a collector adapted to receive wireless data transmission from each of said routers.

This invention also relates to a method for providing environmental monitoring, comprising the steps of: a) providing a plurality of wireless sensor motes, each of said wireless sensor motes comprising: a sensor for sensing an environmental parameter and generating a data signal based on said sensing; a wireless data transmitter for transmitting data signal over a wireless network; an energy harvester adapted for generating electrical energy by harvesting ambient energy from the environment, said electrical energy used to power the said sensor and said wireless data transmitter; and a rechargeable battery for providing storage of energy received from the energy harvester and for powering of said sensor; b) transmitting said data signals from each wireless sensor to a router, said router having an energy harvester for power generation; and c) transmitting said data signals from each router to a collector.

Other objects and advantages will be more fully apparent from the following disclosure and appended claims. BRIEF DESCRIPTION OF DRAWINGS

Figure 1 shows a view of a wireless sensor mote in an embodiment of this invention.

Figure 2 shows an exploded view of a wireless sensor mote in an embodiment of this invention.

Figure 3 shows an overall view of a wireless sensor network in an embodiment of this invention.

Figure 4 shows a flow chart of an embodiment of this invention.

DETAILED DESCRIPTION OF INVENTION

It should be noted that the following detailed description is directed to a wireless sensor network and is not limited to any particular size or configuration of the network but in fact a multitude of sizes and configurations within the general scope of the following description.

Referring to Figure 1 , there is shown a wireless sensor mote (1) in an embodiment of this invention having a sensor (10) at one end. This sensor can be any of several types, and in this way the mote (1) can be customized individually to measure a variety of environmental parameters including, but not limited to air temperature and humidity, and soil temperature, moisture, acidity and fertilizer profile (the relative content of each fertilizer component present in the soil). The sensor (10) also includes an analog to digital converter (12) for processing the analog measurement signal into one that is readily communicable to digital components. An energy harvester (40) is part of the mote (1) and is adapted to harvest ambient energy from the environment and convert that energy into electrical energy. Several different types of energy harvester (40) may be used, depending on the type of ambient energy to be harvested. The types of ambient energy that can be harvested in this invention include wind, solar, thermal, vibration and ambient radio frequency (RF), among others. The electrical energy required to power the sensor motes (1) is typically between 1 to 100 miliwatts (mW). A transmitter (50) is adapted to wirelessly transmit data signals received from the sensor (10). The transmitter (50) includes a system on a chip (SOC) design that allows for some signal processing prior to transmission of signal. Also included in the mote (1) is a rechargeable battery (30), which is charged by the energy harvester (40). Both the sensor (10) and the transmitter (50) as well as any associated electronics are powered by the rechargeable battery (30).

Referring now to Figure 2, there is shown an exploded view of a wireless sensor mote (1) in an embodiment of this invention. A sensor (10) is located at one end. This sensor can be any of several types including, but not limited to air temperature and humidity, and soil temperature, moisture, acidity and fertilizer profile. The sensor (10) also includes an analog to digital converter (12) for processing the analog measurement signal into one that is readily communicable to digital components. An energy harvester (40) is part of the mote (1) and is adapted to harvest ambient energy from the environment and convert that energy into electrical energy. Several different types of energy harvester (40) may be used, depending on the type of ambient energy to be harvested. The types of ambient energy that can be harvested in this invention include wind (402), solar (404), thermal, vibration and ambient radio frequency (RF), among others. The electrical energy required to power the sensor motes (1) is typically between 1 to 100 miliwatts (mW). A transmitter (50) is adapted to wirelessly transmit data signals received from the sensor (10). The transmitter (50) includes a system on a chip (SOC) design that allows for some signal processing prior to transmission of signal. Also included in the mote (1) is a rechargeable battery (30), which is charged by the energy harvester (40). Both the sensor (10) and the transmitter (50) as well as any associated electronics are powered by the rechargeable battery (30).

In an alternative embodiment, the wireless sensor mote (1) may operate without the rechargeable battery (30). In such an embodiment, the sensors (10) and transmitter (50) would only operate when the energy harvester (40) generates electrical energy from the ambient sources. Whenever there is no electrical energy generated, the wireless sensor mote (1) ceases to operate. This may be a feasible and cheaper alternative if there is no need for continuous monitoring of the environmental conditions, and intermittent monitoring is sufficient.

In yet another embodiment, the sensor mote (1) includes an extender (20) for extending the reach of the sensor (10). The extender (20) is fitted with a wire interface for communication of measured data signal from the sensor (10) as well as for providing the sensor (10) with electrical energy either from the rechargeable battery (30) or directly from the energy harvester (40).

Still with reference to Figures 1 and 2, the sensor (10) generates a signal corresponding to a sensed environmental condition or parameter and sends this signal to a transmitter (50), which then transmits a corresponding signal via a wireless communication. The wireless communication can be transmitted directly to a central collector, or to a relay such as a router. An energy harvester (40) is designed to generate and provide sufficient electrical energy to operate the sensor (10) and the transmitter (50). The energy harvester (40) is designed to generate electricity from the conversion of ambient energy available in the surrounding external environment. The electrical energy required to power the sensor motes (1) is typically between 1 to 100 miliwatts (mW). The energy harvester (40) may be any one of wind (402), solar (404), thermal, vibration and ambient radio frequency (RF) types, among others.

Referring now to Figure 3, there is shown several clouds (110) with each cloud (110) comprising of a plurality of wireless sensor motes (1). Each sensor mote (1) measures one or more of a particular environmental parameter such as air temperature or humidity, or soil temperature, acidity, moisture level or fertilizer profile. A data signal is generated based on the measurement and transmitted by each individual mote (1) to a router (120). The router (120) is powered by an energy harvester (140), said energy harvester (140) having a larger energy harvesting capacity than the energy harvester (40) used to power the individual sensor motes (1). The electrical energy required to power the routers (120) is typically between 0.1 to 1 watts (W).

The data signals are then transmitted by each of the routers (120) to a collector (130). This collector (130) will normally be located in a central location such as a farmhouse and thus will have access to power supply, hence not requiring any energy harvesters. In any case, the power typically required by the collector (130) is in the region of between 1 and 100 watts (W), which is a level that is difficult to generate exclusively from micro energy harvesting devices. The collector (130) can then be connected to an IP network (150) for further utilization of the data collected. Figure 4 shows a flow chart of an embodiment of this invention. Environmental energy sources such as wind (4020), solar (4040), vibration (4060), ambient radio frequency (4080, and thermal (4100) is harvested by source converters or energy harvesters (402, 404, 406, 408, 410) and converted into electrical energy. A charge controller (450) controls the charge flow of electric current to an energy storage device such as a rechargeable battery (40). In other embodiments, the energy storage device may be replaced by supercapacitors or micro fuel cells. Power management circuitry (42) then ensures proper power delivery to attached sensor components such as the sensor (10), transmitter (50) and microcontroller (55).

While several particularly preferred embodiments of the present invention have been described and illustrated, it should now be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. Accordingly, the following claims are intended to embrace such changes, modifications, and areas of application that are within the spirit and scope of this invention.