**4. Internet of natural things**

Naturally occurring energy sources can be roughly classified as **environment energy sources** and **human energy sources** [16]. Examples of human energy sources could be kinetic energy coming from arms and legs movements, and thermal energy used to power wearable sensor [18, 19].

Nevertheless, there are some energy sources for energy harvesting applications that occur not precisely naturally, like those originated by electrical, magnetic, and electromagnetic fields, but they can be available in the environment. For example, radio frequency (RF) signal are being harvested to power sensor at a distance [20]. RF energy harvesting is become a good

**Figure 2** shows a basic structure of an energy harvesting system. Its main blocks consist of:

**I. Energy transducer**: it performs the conversion of a primary energy source to electrical energy. Examples: solar photovoltaic cell, in which electrical energy is obtained from solar light energy, thermoelectric generator (also called Peltier module), in which electrical energy is obtained from the difference of temperature on its sides (thermal energy),

**II. Energy conditioning circuit**: a group of subcircuits, which is capable of adjusting the voltage from the transducer in an adequate voltage for powering the target low-power

**III. Energy storage device**: it stores energy for two basics, namely: to accumulate energy which is enough to power the target device and to store the surplus energy. The main

Utilizing energy harvesting systems as main energy sources is turning to be one of the most promising systems for batteryless low-power electronic devices. However, energy harvesting systems can be combined to batteries (or other energy storages) as a solution to reduce the battery's lifetime limitations or to decrease the dependency of battery performance [21, 22].

device. Some subcircuits are rectifiers, filters, DC/DC converters, and so on.

examples are batteries, capacitors and supercapacitors.

**Energy harvester Power density** Solar panel (outdoor conditions) 10,000 μW/cm<sup>2</sup> Thermoelectric generator (30° C) 3500 μW/cm<sup>2</sup> Shoe inserts 330 μW/cm<sup>2</sup> Mechanical vibrations 200 μW/cm<sup>3</sup> Batteries (non-rechargeable lithium) 45 μW/cm<sup>3</sup> Solar panel (indoor conditions) 10 μW/cm<sup>2</sup> Ambient Radio Frequency 1 μW/cm<sup>2</sup>

**IV. Low-power device**: the target low-power device.

**Table 1.** Power density of different energy harvesting propositions [15, 23].

option to power IoT devices.

30 Energy Systems and Environment

and so on.

Even though IoT has gotten substantial attention recently and is a key factor in several paradigms like Smart City [24], Smart Building [25], Connected Cars [25] and Industry 4.0 (Smart Factory) [26], it does not have a standard or globally accepted definition.

Below are some of the concepts related to IoT, which are described taking into account considering:


Taking into consideration the abovementioned concepts, then the IoT can be defined as a network that links smart objects (Things) worldwide, which are capable of: processing, sensing, actuating and communicating with one another, originating directly data to the Internet without any human interaction and providing services to citizens, companies and public administrations.

As described at the beginning of this section, several paradigms related to "smartization" in a given context (e.g.*,* Smart City, Smart Building and Smart Factory) is taking place in the word. In this perspective and considering that the current environmental issues of the planet, it is very natural that the IoT revolution addresses these issues. Consequently, new paradigms as, for example, Smart Forest, Smart Plantation and Smart Farming arise and, as a result, Things can be trees, stones, submerged stones or floating logs in a river, fruits or their fruit trees, barns, cows or anything in a natural or rural environment.

• **Thermal sources**. In natural environments, this kind of energy is largely available since different materials or substances in these environments when near each other may produce different temperature levels providing a way to obtain heat. For example, under the soil, the temperature can be colder than above, so an energy harvesting solution may take place. Another example, under forest canopy, where solar light is not a good option, thermal sources exist in a variety of ways, for instance, it was proved that it is possible to obtain

Energy Resources in Agriculture and Forestry: How to be Prepared for the Internet of Things…

• **Mechanical movement or vibration**. Due to wind in a field or forest, or due to underwater currents in rivers or due to any natural movement, mechanical vibration of Things is an option where piezoelectricity can be used. For example, a small waterfall can be used to obtain rotational movement to rotate a dynamo. Another example, the tree leaf movement

and to take advantage of the natural temperature control of the trees, that maintains that gra-

It was proved that, as a tree trunk is a living organism, the temperature gradient ΔT between any annual ring and the external temperature can be slightly constant or presents slow increment or decrement as the external temperature varies, as shown in **Figure 3**. The explanation to this is that trees try to remain in a comfort zone despite its external temperature regulating

**Figure 4** shows the experimental results when the temperature was measured in three dif-

be noted, the deeper the depth, the bigger is the ΔT. This result indicates that the depth to install the energy harvesting transducer can be chosen accordingly to the voltage level that is required. An interesting point that worth to be highlight is that either at daylight or during the night, ΔT exists with an inversion at 18:00 (6 pm) and at 6:00 (6 am), the local twilight hours,

A possible implementation of the tree trunk energy harvesting transducer is shown in **Figure 5**.

Wireless sensor networks (WSNs) are an important technology for large-scale monitoring, providing sensor measurements at high temporal and spatial resolution [31–33]. In general, WSNs are composed of a large number of low-cost and low-power sensor nodes communicating at distance and sink nodes. Routing nodes and cluster head nodes are also used in WSNs.

Temperature gradients are the temperature difference between the two bodies over a specified distance between them.

The tree is of the species *Adenanthera pavonina*, commonly called red lucky seed, located in the City of João Pessoa, PB

: 100 mm, 75 mm and 50 mm and the external temperature. As can

at different tree trunk depths

http://dx.doi.org/10.5772/intechopen.74940

33

heat from tree trunk [13].

due to wind can be harnessing.

*4.1.1. An example of IoNaT thing: a smart tree*

dient, and convert it into electric energy.

their temperature.

2

3

in Brazil.

ferent depths of a tree<sup>3</sup>

As described in [13], it is possible to get temperature gradients<sup>2</sup>

showing to be possible to harvest thermal energy all day long.

**4.2. WSN as a solution for communication in the IoNaT concept**

In this context, an Internet of Natural Things (IoNaT) takes places for rising smart natural or rural environments.

IoNaT can be defined as a network of natural Things capable of communicating each other and directly originating data to the Internet and providing services to benefit their environments.

A very interesting example could be a Smart Forest where a Smart Tree communicates with other trees. For example, if its temperature is too high (indicating possibly a fire), these data are passed throughout the network to a nearby fire department or the surrounding neighborhoods.

*Since 2000, on average, 18 firefighters have died each year fighting flames and the 2015 wildfire season was the costliest on record, with \$1.71 billion spent to fight the blazes, as said by the U.S. Forest Service. One of the worst problem battling wildfires is to not know rapid weather condition changing, as for example, wind direction, which can put fire towards firefighters giving no way they get away to a safe position. Therefore, having information about local weather and environmental conditions can save many lives.*

The main challengers for an IoNaT are:


#### **4.1. Energy harvesting as a solution for power supply in the IoNaT concept**

Over the last decades, due to the advancement in microelectronic technology, electronic devices are progressively getting smaller and achieve extremely low-power consumption enabling the design of energy autonomous systems (EAS), which are low-power systems that run without being connected to any power grid and are powered by small batteries [30].

In its turn, energy harvesting system either increase the battery's life cycle toward perpetual EAS [14] or marking self-powered batteryless EAS.

Therefore, with the purpose to avoid deploying the battery directly into the nature, the development of batteryless energy harvesting devices is an ideal alternative since they can be designed considering natural energy sources around the natural Thing in the IoNaT context.

Potential candidates of natural energy sources for batteryless energy harvesting devices could be:

• **Solar light**. Everywhere in natural environments as fields, deserts, water's surface, mountains, etc., solar light is a good option with the usage of small photovoltaic cell. However, at daylight, it works well, but at night, it needs some energy storage device to work where capacitor or supercapacitor may be used.


#### *4.1.1. An example of IoNaT thing: a smart tree*

very natural that the IoT revolution addresses these issues. Consequently, new paradigms as, for example, Smart Forest, Smart Plantation and Smart Farming arise and, as a result, Things can be trees, stones, submerged stones or floating logs in a river, fruits or their fruit trees,

In this context, an Internet of Natural Things (IoNaT) takes places for rising smart natural or

IoNaT can be defined as a network of natural Things capable of communicating each other and directly originating data to the Internet and providing services to benefit their environments. A very interesting example could be a Smart Forest where a Smart Tree communicates with other trees. For example, if its temperature is too high (indicating possibly a fire), these data are passed throughout the network to a nearby fire department or the surrounding

*Since 2000, on average, 18 firefighters have died each year fighting flames and the 2015 wildfire season was the costliest on record, with \$1.71 billion spent to fight the blazes, as said by the U.S. Forest Service. One of the worst problem battling wildfires is to not know rapid weather condition changing, as for example, wind direction, which can put fire towards firefighters giving no way they get away to a safe position. Therefore, having information about local weather and environmental conditions can* 

Over the last decades, due to the advancement in microelectronic technology, electronic devices are progressively getting smaller and achieve extremely low-power consumption enabling the design of energy autonomous systems (EAS), which are low-power systems that run without being connected to any power grid and are powered by small batteries [30].

In its turn, energy harvesting system either increase the battery's life cycle toward perpetual

Therefore, with the purpose to avoid deploying the battery directly into the nature, the development of batteryless energy harvesting devices is an ideal alternative since they can be designed considering natural energy sources around the natural Thing in the IoNaT context. Potential candidates of natural energy sources for batteryless energy harvesting devices could

• **Solar light**. Everywhere in natural environments as fields, deserts, water's surface, mountains, etc., solar light is a good option with the usage of small photovoltaic cell. However, at daylight, it works well, but at night, it needs some energy storage device to work where

barns, cows or anything in a natural or rural environment.

rural environments.

32 Energy Systems and Environment

neighborhoods.

be:

*save many lives.*

The main challengers for an IoNaT are:

**I.** Power supply to the Things without chemical batteries and

**4.1. Energy harvesting as a solution for power supply in the IoNaT concept**

**II.** Communications support in the presence of vegetation.

EAS [14] or marking self-powered batteryless EAS.

capacitor or supercapacitor may be used.

As described in [13], it is possible to get temperature gradients<sup>2</sup> at different tree trunk depths and to take advantage of the natural temperature control of the trees, that maintains that gradient, and convert it into electric energy.

It was proved that, as a tree trunk is a living organism, the temperature gradient ΔT between any annual ring and the external temperature can be slightly constant or presents slow increment or decrement as the external temperature varies, as shown in **Figure 3**. The explanation to this is that trees try to remain in a comfort zone despite its external temperature regulating their temperature.

**Figure 4** shows the experimental results when the temperature was measured in three different depths of a tree<sup>3</sup> : 100 mm, 75 mm and 50 mm and the external temperature. As can be noted, the deeper the depth, the bigger is the ΔT. This result indicates that the depth to install the energy harvesting transducer can be chosen accordingly to the voltage level that is required. An interesting point that worth to be highlight is that either at daylight or during the night, ΔT exists with an inversion at 18:00 (6 pm) and at 6:00 (6 am), the local twilight hours, showing to be possible to harvest thermal energy all day long.

A possible implementation of the tree trunk energy harvesting transducer is shown in **Figure 5**.
