Remote monitoring describes the monitoring of remote (usually off-grid) energy systems from a geographically distant location. Most remote monitoring systems (RMS) available today monitor the functionality and performance of energy generation systems (typically solar or wind energy), however end-user consumptive applications such as cookstoves can also be monitored.
RMS are an attractive option for technical cooperation and system operators as they facilitate maintenance operations in remote locations and allow evaluating the sustainability of off-grid renewable energy systems or end-user consumptive applications beyond project completion.
Basic System Architecture and Operation
In its most basic form, a Remote Monitoring System (RMS) consists of three distinct elements:
- On-site monitoring equipment installed at one or more sites,
- a data transfer solution (typically via satellite or a mobile network), and
- a central monitoring station with data storage, where information is aggregated and processed.
The heart of every on-site RM setup is the Data Acquisition System (DAS). The DAS consists of multiple sensors for data collection, attached to the system components to be monitored. This allows for the collection of a wide range of data, including information on generation / end-use equipment (e.g. power load, system temperature), storage (e.g. battery current) or ambient conditions (e.g. temperature, wind speed, solar irradiance).
The overall system complexity and measurement intervals can be adapted to factors such as installation size, intended data usage and local circumstances. A key difference is whether the purpose of the RMS is to monitor the basic functionality of an installation and its subsystems or whether sophisticated monitoring on performance is carried out. The interpretation of measurements can be conducted manually or automatically. Manual interpretation is possible via on-site displays which can visualize key data readings. Local availability of skills is necessary for on-site interpretation.
Two solutions are mainly applied for data transfer. These are satellite based systems and mobile networks.
Mobile network based solutions are used where network infrastructure with a sufficiently reliable signal is in place, as this method is usually linked to lower costs and less maintenance. A 2G mobile network is usually sufficient to achieve the necessary rates for data transfer, as the amount of data is limited.
Data-transfer can be carried out manually or automatically. Local operators or end-users can e.g. use SMS to transfer relevant data to a central monitoring station in case of failure, at regular intervals or on request. Again, this requires a certain amount of energy literacy.
Satellite based systems accrue higher costs for investment and operation. However, they are the only viable solution for many remote locations (see data transfer challenges). Collected data can be stored locally and transferred at intervals or be transmitted continuously (signal permitting).
Central Monitoring and Data Storage
Central monitoring systems consist of standard ICT solutions, connected to the internet. In-coming data is aggregated on servers and made available to authorized users via a web-browser based interface or a smartphone application. Before making information available to users, raw data is commonly processed to allow for improved accessibility. Current technical possibilities include automated alert functions, visualization of data in graphs, color coding etc.
Specific setups also allow for remote control functions through which the monitoring entity can interfere with operation on site (see operation and maintenance benefits).
Benefits of Remote Monitoring Systems
Opportunities arise mainly in two areas: Operation and maintenance (O&M) and monitoring and evaluation (M&E):
Operation and maintenance (O&M)
The availability of up-to-date information from RMS allows for more efficient handling of technical difficulties and maintenance issues. It becomes possible to detect faults and initiate troubleshooting at an early stage, potentially preventing more severe and costly system failures. Maintenance interventions can be planned beforehand, e.g. by identifying the required spare parts. The following are sample applications of RMS in O&M:
- An area where particular opportunity exists is electricity storage. Improper care and overuse of batteries is a common source for failure in electrical off-grid systems. By detecting the sustained overuse of batteries and initiating preventative measures, battery life – and thus overall system operation – could be prolonged.
- The improved availability of information can substitute or facilitate site visits. In particular lengthy visits to remote locations can be significantly simplified. Remote troubleshooting support to local operators and users can avoid a visit altogether (see country example Indonesia).
- Remote control options open further possibilities in the field of O&M. Remote operation options range from software updates to remote shutdown of the systems or parts thereof. Apart from damage prevention, this feature can also be used to provide theft protection for key system components or to facilitate pre-paid energy service provision models. Azuri Technologies, a provider of Solar Home Systems, for example, offers a pay as you go service for their product, in which customers can pay off their SHS over a number of months or even years. If a customer fails to make his / her agreed monthly payment, the technology is temporarily disabled via a remote control function until regular payments are resumed (Azuri Technologies).
Monitoring and Evaluation (M&E)
Remote Monitoring allows for the monitoring of system use and performance at changing ambient conditions. Such information can provide a range of insights for project evaluation. Besides the opportunity to monitor changes in system use, future interventions can be opt-mized by identifying weaknesses and bottlenecks in a given system design. The information collected from different sites can contribute towards improving the general understanding of an installed technology as well as its reliability.
Challenges for Implementers
RMS are fairly expensive. Tangible costs arise both from installation and operation. The main cost drivers for a RMS are the DAS and data transfer solutions. A key determinant of RMS cost is the choice between proprietary or open-source solutions. Where sufficient know-how and non-financial resources are available, the latter can decrease costs and dependency on commercial providers as well as allowing for more personalized solutions (see for example Jucá et al., 2011).
Data Collection Challenges
While RMS offer a valuable source for data e.g. on system failures, RMS also constitute an additional source for failure. This is especially the case when the system is highly complex. Furthermore, to ensure the correct collection of high quality and reliable data over sustained periods of time, a periodic calibration of sensors is required.
In designing a Data Acquisition System, it is therefore essential to weight complexity (e.g. number of sensors installed) and resulting data quality against its potential susceptibility to errors and the arising costs.
Data Transfer Challenges
Systems utilizing mobile networks require the necessary infrastructure to operate. Satellite based solutions are theoretically available even at the most distant and inaccessible locations.
In practice, however, careful consideration needs to be paid to the availability of a sufficiently strong signal for either transfer options. Apart from basic preconditions (e.g. an appropriately sized satellite dish and operational frequency) line-of-sight is commonly the most critical bar-rier for satellite based systems. A number of aspects need to be considered to avoid problems related to line-of-sight. These include vegetation coverage, cloud cover or rain attenuation.
Challenges for Manual RMS
Where an RMS relies on manual input to a significant degree, local skills become a critical factor for successful operation. Consequently, RMS capacity development / training need to be considered in case manual RM systems are installed.
Experiences from the field
As part of the ESCoBox project Practical Action have produced a series of technical notes on remote monitoring, management and payment methods for mini-grids:
- ↑ Dauenhauer, P.M. et al.: Remote Monitoring of Off-grid Renewable Energy. Case Studies in rural Malawi, Zambia, and Gambia. Global Humanitarian technology conference (GHTC), 2013
- ↑ 2.0 2.1 Casella, A.:Using Satellites To Remotely Managa PV Installations. Solar Industry Magazine. 6(10), 2013. available from: http://www.solarindustrymag.com/issues/SI1310/FEAT_01_Using-Satellites-To-Remotely-Manage-PV-Installations.html