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Remote Performance Monitoring Systems

rpm-sat
Remote monitoring systems  are often deployed far from traditional power and communications infrastructure.
(Photo: NREL)

Remote performance monitoring of health facility power installations increases the speed, effectiveness and value of maintenance activities.

Remote performance monitoring describes an approach to tracking the operation of systems or processes, such as the charging and discharging of a battery bank, from a distance.  The advantages of a remote monitoring approach for are to enhance maintenance activities; to inform system designers of real-world environmental and operational conditions; and to generally promote the sustainability and replicability of backup power installations.

Remote monitoring is used in a wide range of industries to track the performance of industrial, scientific and power equipment.  Because of the diverse applications and design constraints associated with remote monitoring systems, a variety of technical solutions have been developed to make power and communications for such systems feasible.  This page provides a broad overview of remote monitoring applications, technologies and techniques.

 

IHFI Experience

rpm - satstation
IHFI’s “Satellite Station” is a compact and efficient remote monitoring solution.

To date, the IHFI project has deployed remote monitoring systems at three backup power installations in Haiti.  These three systems have provided valuable performance data at relatively low operational costs.  The heart of IHFI’s remote monitoring hardware configuration is a unit called the “Satellite Station”, developed by Upward Innovations, a Massachusetts company specializing in remote monitoring.  The Satellite Station is responsible for collating data from the backup system’s inverter and sending hourly averages to a remote server via satellite.  In addition to providing the on-site hardware, Upward Innovations also hosts the remote monitoring data on its internet servers and provides satellite service through the Iridium LEO satellite network.  This arrangement has resulted in a low power (1 W), low cost (US$1/day) remote monitoring system that requires minimal additional on-site hardware.

The Satellite Station comprises a data logger, a small satellite transceiver and a backup battery in case of power loss (the system is powered by the 12V auxiliary power supply of an Outback inverter).  Through specially modified software, the Satellite Station is able to communicate with IHFI system’s Outback inverters through an Outback MATE or MATE2 system display, which is already included in IHFI backup systems.  A common RS-232 cable is all that is needed to connect the Satellite Station to an Outback MATE.  The Satellite Station receives a continuous stream of data from the Outback system, which are averaged and transmitted via satellite on an hourly basis.  The system uses Iridium’s duplex LEO satellite network to transfer performance data to an Upward Innovations web server, where the data is stored and made available to interested parties via the internet.

From Upward Innovation’s data hosting site, DataGarrison, users can view and edit performance data graphs or download full data sets for further analysis.  The site also displays useful information such as the state of the transmitter battery and the bandwidth usage remaining on the Iridium service plan.  Due to the two-way (duplex) satellite link, users may also remotely control on-site software settings, such as changing data transmission intervals or restarting the data logger.  DataGarrison can also issue system alerts via e-mail, which can then be routed to technician cell phones through SMS messaging.

Upward Innovations has provided solutions for nearly all phases of the remote monitoring data stream: data logging and transmission hardware, software customization, satellite service and remote data hosting.  This arrangement has resulted in a relatively simple hardware configuration and has streamlined costs as only one payment is made for both the satellite service and data hosting.

 

Remote Monitoring Applications

Remote performance monitoring systems are used in a variety of applications and settings.  They are often used in the oil and gas industry, to monitor leaks in gas pipelines, for example, or in the telecommunications industry, to ensure cellular towers have backup power.  Remote monitoring is also frequently used to track industrial processes or weather stations.  This discussion of remote performance monitoring systems will focus on applications for rural health facilities.  In health facilities remote monitoring systems can be used to track a variety of important energy system components, some of which are described below.

 

ApplicationDescription
Battery Banks Battery banks are perhaps the most maintenance intensive aspect of a facility’s energy system.  Many factors influence the life of a battery bank, including depth of discharge, charge rate and temperature.  Making sure that these parameters are all within proper boundaries is essential to the battery bank’s sustainability.  Logging battery bank performance data can help technicians identify problems before they lead to costly battery failures and system downtime.  Important parameters that can be tracked through remote monitoring systems include:
  • State-of-charge (%)
  • Battery bank voltage (V)
  • Battery charging current (A)
  • Battery temperature (C)
  • Days since fully charged
PV Systems Photovoltaic (PV) systems are good candidates for remote monitoring systems.  PV systems are expensive, and are often deployed in areas without access to other energy sources like grid power, so ensuring that PV installations are working properly is important.  Remote performance monitoring systems can be used to track PV parameters such as:
  • Solar charging (kW)
  • Solar charging (A)
  • Solar radiation (W/m2)
Facility Consumption Tracking the energy consumed by a facility, or part of a facility (e.g. laboratory, server), can be extremely useful when designing or evaluating an energy system, such as a battery bank for backup power.  For instance, monitoring consumption will help to determine whether or not a battery bank is sized properly.  Consumption is usually tracked by:
  • Current draw (A)
  • Load (kW)
  • Energy consumption (kWh)

 

Remote Monitoring Design and Technologies

Remote monitoring is a valuable tool for a wide range of industrial, scientific and power applications.  A variety of technologies and techniques have been developed to perform remote monitoring for these diverse applications.  The cost, complexity, reliability and availability of features vary significantly between remote monitoring technologies and choosing the most appropriate approach for a specific application requires an understanding of the constraints (cost, power, etc.) that will be placed on the system.

Although there are many methods of conducting remote monitoring, they all must address three essential design aspects: on-site hardware, communications, and remote data access.  The following sections discuss the possible technological solutions underlying each of these areas.

On-site Hardware

rpm - rs232
An RS-232 serial data cable, a standard commonly used in remote monitoring systems.
(Photo: Faxe available under a Creative Commons Attribution-Share Alike license.)

The hardware installed at the target installation site is the heart of the remote monitoring system, generating, storing and transmitting a flow of data.  This hardware is made up of sensors, data acquisition systems and communications equipment which must interface with one another and the energy system hardware itself (e.g. inverters, charge controllers).  When specifying the on-site hardware of a remote monitoring system, compatibility is the key issue.  The installed systems must be able to communicate with one another in order to relay performance data to a remote location.

The most effective on-site hardware configuration will depend largely on the brand of inverter or charge controller used.  Different brands utilize different communications protocols, or language, when communicating operational parameters.  In many cases a proprietary language is used, but some brands utilize open source languages that allow more design flexibility for remote monitoring systems. 

Another important consideration influencing the on-site hardware configuration is the availability of data ports, or the way in which the inverter/charge controller interfaces with other machines.  This is typically accomplished with an RS-232 serial port (this is a standard format that has been largely replaced by USB ports on new computers).  Such a port must be included in the energy system’s hardware in order to communicate with a computer or other machine.  Therefore, both the communications protocol and data connection compatibility of the inverter/charge controller will define, to a large extent, the complexity of the remote monitoring hardware configuration.

 

TechnologyDescription
Power Supply Determining the source of power for the remote monitoring hardware is an important first step in understanding the system’s design constraints.  The availability of power will have an impact on the frequency of data logging and data transmission, as more frequent transmissions require more power.  Many remote monitoring systems rely on solar panels to provide power, as they are typically deployed in locations far from other power sources.  Other sources may be utilized, such as an auxiliary power supply on an inverter.
Sensors Sensors are devices that interact with the outside world in order to create data on the performance of a particular system component or the state of a specific system parameter or environmental condition.  Sensors are available for tracking any number of specific conditions, such as: water flow, air speed, or voltage.  In an off-grid solar installation, for example, the conditions of interest might be: DC voltage, solar irradiance, state-of-charge of the battery bank, etc.  Many types of system components, notably inverters and charge controllers, are already able to track basic electrical parameters such as voltage and amperage, so many of the sensors needed for remote performance monitoring are already integrated into the system.  Additional sensors may include:
  • solar radiation sensor
  • kWh logger
  • battery temperature monitor
Data Acquisition The data acquisition (DAQ) hardware is a key component to nearly any remote performance monitoring system.  This is the critical piece of equipment that receives data from the various sensors, including the inverter/charge controller.  Data acquisition hardware retrieves and stores data, but may also display data for a user or transmit data through the internet.  A data acquisition system may constitute more than one piece of equipment.   
  • System compatible DAQ hardware

Many manufacturers of solar system and battery bank power equipment, like inverter manufacturers, also make data acquisition systems that take advantage of sensors already included in their equipment.  The capabilities of manufacturer DAQ hardware will vary from manufacturer to manufacturer and may include such features as internet connectivity, display screens or additional data storage capacity.

  • PC based DAQ

Software is available for any normal PC that can manage, store and communicate performance data.  These options present relatively low cost ways to collect and share large volumes of information.  PC based remote monitoring systems transmit data through the internet, and are compatible with any form of internet service: wired, cellular or satellite.  This internet connection, however, is dependent on other on-site IT infrastructure and network settings, such as firewalls, that can disrupt data communications.

  • Independent DAQ Hardware

Third-party dedicated hardware that monitors and transmits performance data.  These systems differ from PC based systems in that they do not rely on the Windows operating system, but instead have their own internal operating system, making them generally more reliable.  They are typically not compatible with energy system hardware, meaning that the monitoring hardware cannot communicate with the system’s inverter and therefore cannot take advantage of any of the inverter’s built-in sensors or alarms.  Such systems are most commonly found in industrial settings, and many are designed for specific tasks (e.g. wind speed measurement or kWh logging).  More versatile systems can be configured for a wide range of sensor types, but are often comparatively complex.  While generally more reliable than PC based systems, they are also more expensive and most are still completely dependent on an internet connection for communications.

Modem A modem is a device that converts analog signals (e.g. sounds, light, radio) into digital data that can be accessed by a computer, and vice versa.  Modems are a necessary piece of equipment for any remote monitoring system as they allow for performance data to be sent via an internet connection, a satellite uplink or even a radio transmission.  Different communication links rely on different types of analog signals (electrical signals, cellular signals, radio signals, etc.) and therefore require different types of modems to encode and decode those signals.



Configuration Options 
rpm - configuration
1In this configuration, the energy system’s existing inverter and system monitor are used to track operational data.  A data logger must then communicate with the system monitor before transmitting that operational data via a modem at scheduled intervals.  In the case of the IHFI installations, a 3rd party data logger and satellite modem, called the “Satellite Station”, was specially modified to communicate with Outback hardware.
2A PC can be utilized for data logging purposes, and to interface with the communications modem.  In this configuration, a computer, which must be constantly running, houses data on-site before sending it to a remote location via the communications link. 
3A similar arrangement to that described in configuration 2.  This configuration would require that the inverter/charge controller include a data port that is compatible with a PC (such as an RS-232 port).
4Depending on the type of communications link being utilized, it may be possible to transmit operational data continuously, without the need of on-site data logging.  Such a set-up, however, would require a lot of bandwidth, leading to slower internet connections and possibly higher service fees.  Transmitting data continuously will also increase the power demand of the modem.
5A data acquisition system, independent of the inverter/charge controller, is another hardware option.  Such an arrangement is able to circumvent the any software or hardware challenges due to the proprietary nature of the inverter/charge controller’s communications interface.  Many 3rd party data acquisition systems collect, store and transmit data in a single package.  They must, however, be wired into the energy system independently of the existing hardware, resulting in a more complex installation.

 

Communications

The next major piece of a RPM system is the communications infrastructure.  This aspect of system design is what makes remote performance monitoring possible.  When choosing an appropriate communications method the key issue is reliability.

TechnologyDescription
Internet Communication through the internet is, in many cases, an easy, cost effective and versatile approach.  The reliability of an internet data link, however, is dependent on the condition of available communications infrastructure and access to IT management.
  • Wired modem

Wired internet connections are a low cost option for transmitting large amounts of data.  The availability and reliability of such connections depend largely on the state of local infrastructure.  These systems are vulnerable to natural disasters or other interruptions of service.

  • Cellular modem

A wireless internet connection, via a cellular modem, is another data communication option.  The reliability and performance of a cellular connection depends largely on the cellular signal strength at the installation site, which varies based on the local carrier (service provider) and cellular technology.  These systems are also subject to interruptions of service due to natural disasters.  The necessary hardware, network settings, and contract type may differ from one carrier to the next, making the standardization of remote monitoring systems across multiple locations difficult if the local carrier varies by location.

  • Satellite modem

Satellite based internet connections are an option that is especially appealing for rural installations that do not have access to wired or cellular internet connections.  This type of connection is typically more expensive, but the final cost will depend on the amount of data being transferred.  These connections are reliable and are normally unaffected by natural disasters.  Setting up such systems, however, can be more complicated and expensive than setting up a wired or cellular connection.  Satellite internet connections, for instance, require a Very-Small-Aperture (VSA) satellite dish (like those used for Satellite television) on-site; incorrect installations can lead to reliability issues in satellite based internet connections.

LEO Satellite Low earth orbit (LEO) satellites present a dependable and increasingly low cost alternative to internet communication.  Unlike satellite based internet connections, which typically deliver all internet services to the facility, LOE satellites provide a direct and dedicated connection exclusive to the remote monitoring system.  This eliminates the potential for problems with firewalls or network configurations that can negatively affect internet based RPM systems.  The amount of data that can be sent through LEO satellite connections is less than that of internet connections, however.  LEO systems typically transfer data less frequently and may limit the number of system parameters that can be sent.  LEO satellite connections also may require a custom interface (as in the custom software modification in IHFI’s Satellite Stations) to connect the RPM system hardware to the dedicated satellite modem.  Among the LEO satellite services offered, there are two connection types:
  • Duplex

Duplex LEO satellite connections are a two-way connection where satellites can both send and receive data from remote monitoring transmitters.  This is the most common form of LEO satellite service.

  • Simplex

Simplex LEO satellite connections are a one-way connection that allows satellites to receive data from remote monitoring transmitters, but not to send data back.  Compared to duplex connections, simplex connections are less expensive, in terms of service plans and hardware requirements.  Simplex connections also have a lower data capacity than do duplex.

Data Radio Data radio is a technology that allows for the transfer of data across license free radio frequencies (those frequencies not reserved for government or commercial use).  Data radios are frequently used in remote monitoring applications because they provide a consistent and robust way to transfer data wirelessly, independent of internet and satellite service providers, local infrastructure and service fees.  The hardware associated with a data radio network includes a radio, a radio modem and an antenna for not only the installations being monitored, but also for a base station that would receive and remotely store data.  The range, reliability and transmission quality of such a network depends on the quality of the hardware used, the transmission power and the availability of uncongested, license free radio frequencies.

 

 rpm - communications

 

Data Access

The final critical component of a remote monitoring system is the user interface.  Data gathered from the remote installation is communicated, through either an internet, LEO satellite or radio based data link, and stored on a remote server.  From this server, the data can be made available through a variety of media.

TechnologyDescription
Internet Internet portals are a convenient and popular way to present RPM data.  Data can be downloaded and graphically presented through a secure internet portal.  System administrators and other interested parties with a username and password can access the data from anywhere.
Mobile Mobile applications can be designed to give users access to remote monitoring data through smart phones, tablets or other mobile devices.  Such applications provide technicians and administrators the ability to check system performance from virtually any location.  They may also issue alerts or alarms when system failures occur, or better yet, before they occur.
Periodic Reports Not all system stakeholders are concerned with real-time data analysis, but are interested in overall system performance and sustainability.  Periodic reporting of system data (on a weekly or monthly basis, for example) is made possible through remote monitoring.  Performance data over the period can be graphically represented for easy interpretation, and a discussion or analysis of that data may also be included.  Such reports can be automatically generated and sent via e-mail, or may be prepared by system managers.
Public Display Sometimes system performance data is displayed publicly.  When building owners wish to advertise the fact that they generate solar power for use on-site, a display showing real time energy output is an effective and interesting way to capture public attention.  Such displays are not meant to be used in a technical way, but rather to present data in an attractive and easy-to-understand format.

 

Remote Monitoring Data Analysis

The value of a remote performance monitoring system is in the data it provides to system stakeholders.  Once data has been collected, transmitted and distributed, it can be analyzed, reported, or acted upon.  Remote monitoring data helps system technicians, designers, administrators and financers to ensure the sustainability and replicability of energy system installations.

AnalysisDescription
Corrective and Preventative Maintenance Perhaps the most valuable advantage of remote performance monitoring is the ability to anticipate or identify faults or problems in a system’s functioning without frequent field visits by technicians.  Especially for remote installations, visits or inspections by trained technicians can be costly and time consuming.  Even regularly scheduled site visits can result in prolonged downtime if problems occur long before the scheduled visit or if the technician requires additional tools or parts to service the system should a problem be encountered.  By alerting technicians to system failures or problems as or before they occur, and by allowing them to diagnose the problem in advance, remote monitoring systems can significantly reduce or eliminate downtime.
System Design Beyond faults or problems with system operations, remote monitoring data can also help reveal flaws in system design.  Such problems may not arise from malfunctioning equipment or insufficient maintenance, but stem from the system’s basic design.  Such problems could affect the efficiency or sustainability of the system; for example a battery bank may be undersized for facility loads, leading to premature battery failure.  Remote monitoring data helps designers and technicians identify design flaws to refine future installations or correct existing installations.
Performance Reporting Remote performance monitoring has added value in that it gives piece of mind to managers at the institutions concerned with financing or administering energy system installations.  Energy systems are expensive to buy and install and power equipment typically has a long live span (greater than 10 years); therefore ensuring system longevity is important.  Remote monitoring data not only enhances system sustainability, through timely corrective maintenance, but also assures managers and financers that their resources are being used effectively.  Long term data on energy system performance helps administrators to replicate successful installations and encourages additional investment in health facility energy infrastructure.

 

Standards Relevant to Remote Monitoring Systems

The standards listed below describe some communications protocols and hardware components commonly used in remote monitoring.  These standards are not necessarily universally applicable as  many remote monitoring configurations will rely on proprietary, brand-specific communications and hardware.

 

Institute of Electrical and Electronics Engineers (IEEE)
CategoryStandard
Communications IEEE 802.11-2012: Telecommunications and information exchange between systems—Local and metropolitan area networks

 

Telecommunications Industry Association (TIA)
CategoryStandard
Hardware TIA TIA-232-F: Interface between Data Terminal Equipment and Data Circuit-Terminating Equipment Employing Serial Binary Data Interchange

 

MODBUS
CategoryStandard
Communications MODBUS V1.1b: MODBUS Protocol Specifications

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