Citation: Mahdi Elsiddig Haroun, F.;
Mohamad Deros, S.N.; Ahmed
Alkahtani, A.; Md Din, N. Towards
Self-Powered WSN: The Design of
Ultra-Low-Power Wireless Sensor
Transmission Unit Based on Indoor
Solar Energy Harvester. Electronics
2022, 11, 2077. https://doi.org/
10.3390/electronics11132077
Academic Editor: Federico Alimenti
Received: 24 January 2022
Accepted: 27 June 2022
Published: 2 July 2022
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Article
Towards Self-Powered WSN: The Design of Ultra-Low-Power
Wireless Sensor Transmission Unit Based on Indoor Solar
Energy Harvester
Fathi Mahdi Elsiddig Haroun
1,
*, Siti Noratiqah Mohamad Deros
1
, Ammar Ahmed Alkahtani
2
and Norashidah Md Din
1
1
Institute of Energy Infrastructure, Universiti Tenaga Nasional, Kajang 43000, Malaysia;
siti.noratiqah@uniten.edu.my (S.N.M.D.); norashidah@uniten.edu.my (N.M.D.)
2
Institute of Sustainable Energy, Universiti Tenaga Nasional, Kajang 43000, Malaysia; ammar@uniten.edu.my
* Correspondence: fathi.mahdi@uniten.edu.my
Abstract:
The current revolution in communication and information technology is facilitating the
Internet of Things (IoT) infrastructure. Wireless Sensor Networks (WSN) are a broad category of IoT
applications. However, power management in WSN poses a significant challenge when the WSN
is required to operate for a long duration without the presence of a consistent power source. In
this paper, we develop a batteryless, ultra-low-power Wireless Sensor Transmission Unit (WSTx)
depending on the solar-energy harvester and LoRa technology. We investigate the feasibility of
harvesting ambient indoor light using polycrystalline photovoltaic (PV) cells with a maximum power
of 1.4 mW. The study provides comprehensive power management design details and a description
of the anticipated challenges. The measured power consumption of the developed WSTx was 0.02109
mW during the sleep mode and 11.1 mW during the operation mode. The harvesting system can
harvest energy up to 1.2 mW per second, where the harvested energy can power the WSTx for six
hours with a maximum power efficiency of 85.714%.
Keywords: energy harvester; LoRa; solar power; ultra-low power; WSN
1. Introduction
The revolution in the microchips industry, especially in microcontrollers (MCUs),
helped integrate embedded systems with various types of daily used devices. The demand
to connect these devices to the internet became vital due to the emerging technologies in
information and communication infrastructure such as high-speed internet, cloud com-
puting, and big data. The Internet of Things (IoT) technology enables machines such as
home appliances, medical equipment, and industrial instruments to interact with users
and other machines through the internet [
1
,
2
]. Portable, Wireless Sensor Network (WSN)
represents a broad IoT application sector [
3
]. The role of WSN in IoT applications is to
convert and transfer environmental variables such as temperature, pressure, vibration,
and other variables through a wireless network of devices. This network can send and
receive data from the internet through a gateway node [
3
,
4
]. The WSN system usually
consists of four main units: sensing unit, processing unit, wireless communication unit, and
power management unit, as shown in Figure 1 [
5
]. Power management in WSN devices
is always a challenging issue. Such devices are required to operate in remote locations
for several years without charging or replacing the storage element, compared with other
battery-powered devices such as mobile phones [
6
,
7
]. Battery management techniques, low
power MCUs, and low power communication technologies are required to mitigate the
power consumption in WSN systems. The new emerging Long-Range (LoRa), low-energy
consumption radio modulation technology enables wireless sensor devices to communicate
through a low-power consumption profile, compared with other widely used wireless
Electronics 2022, 11, 2077. https://doi.org/10.3390/electronics11132077 https://www.mdpi.com/journal/electronics
