New Techniques for Sizing Solar Photovoltaic Panels for Environment Monitoring Sensor Nodes
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Date
2019
Journal Title
Journal ISSN
Volume Title
Publisher
Journal of Sensors
Abstract
The development of perpetually powered sensor networks for environment monitoring to avoid periodic battery replacement
and to ensure the network never goes offline due to power is one of the primary goals in sensor network design. In many
environment-monitoring applications, the sensor network is internet-connected, making the energy budget high because data
must be transmitted regularly to a server through an uplink device. Determining the optimal solar panel size that will deliver
sufficient energy to the sensor network in a given period is therefore of primary importance. The traditional technique of sizing
solar photovoltaic (PV) panels is based on balancing the solar panel power rating and expected hours of radiation in a given area
with the load wattage and hours of use. However, factors like the azimuth and tilt angles of alignment, operating temperature, dust
accumulation, intermittent sunshine and seasonal effects influencing the duration of maximum radiation in a day all reduce the
expected power output and cause this technique to greatly underestimate the required solar panel size.Themajority of these factors
are outside the scope of human control and must be therefore be budgeted for using an error factor. Determining of the magnitude
of the error factor to use is crucial to prevent not only undersizing the panel, but also to prevent oversizing which will increase the
cost of operationalizing the sensor network. But modeling error factors when there are many parameters to consider is not trivial.
Equally importantly, the concept of microclimate may cause any two nodes of similar specifications to have very different power
performance when located in the same climatological zone. There is then a need to change the solar panel sizing philosophy for
these systems. This paper proposed the use of actual observed solar radiation and battery state of charge data in a realistic WSNbased
automatic weather station in an outdoor uncontrolled environment.We then develop two mathematical models that can be
used to determine the required minimum solar PV wattage that will ensure that the battery stays above a given threshold given
the weather patterns of the area. The predicted and observed battery state of charge values have correlations of 0.844 and 0.935
and exhibit Root Mean Square Errors of 9.2% and 1.7% for the discrete calculus model and the transfer function estimation (TFE)
model respectively. The results show that the models perform very well in state of charge prediction and subsequent determination
of ideal solar panel rating for sensor networks used in environment monitoring applications.
Description
Keywords
Solar Photovoltaic Panels, Environment Monitoring Sensor Nodes
Citation
Byamukama, M., Bakkabulindi, G., Akol, R., & Sansa-Otim, J. (2019). New Techniques for Sizing Solar Photovoltaic Panels for Environment Monitoring Sensor Nodes. Journal of Sensors, 2019. https://doi.org/10.1155/2019/9835138