Digester Monitor and Control Systems - dmcs-link.comdmcs-link.com/SysDiscription_E-k1.pdf · that...

Digester Monitor and Control System

System Description

PERFORMANCE SYSTEMS Melbourne, Florida

FEB 15, 2010

2220 OHIO STREET • P.O. BOX 120086 • MELBOURNE, FLORIDA 32904

Email: info@per-sys.com ∙ PH: (321) 728-1338 • FAX: (321) 728-2732

Feb 15, 2010

DIGESTER MONITOR AND CONTROL SYSTEM

PERFORMANCE SYSTEMS 2220 OHIO STREET · P.O. BOX 120086 · MELBOURNE, FLORIDA 32904

Email: info@per-sys.com ∙ PH: (321) 728-1338 · FAX: (321) 728-2732

1.0 SYSTEM OVERVIEW

The Digester Monitor & Control System (DMCS)

provides a turnkey solution for monitoring, controlling

and collecting gas flow rate, volume and flare activity

at remote bio-digester sites. The system, which is

normally solar powered, can also be optionally

powered via universal shore power where available.

The basic system consists of six main components,

Data Logger, Power Conditioning Sub-system, Gas

Flow Sensor, Flare Temperature Sensor, Ignition

Control Unit and Automated Gas Control Valve.

Optionally, the system may also include the capability

for Remote Monitoring, Alarming and Control

(RMAC). The RMAC option periodically uploads

collected data and system health information to a

dedicated server. The server inserts the data in a

relational database, formats it and makes it available to users via the World Wide Web.

Additionally, it has the capability of alerting users via email or text messaging when user-

specified parameters are exceeded.

The system includes an Uninterruptable Power Supply (UPS) which will typically operate

the system for up to five consecutive days without solar or shore power.

To reduce the effects of sun load and minimize the internal temperature, the system

incorporates a temperature threshold activated enclosure cooling fan. If the temperature of

the electronics is allowed to exceed its design limits the operation of the system may

become undependable and possible damage to the electronics may result. When the

internal temperature of the enclosure reaches the set point temperature (~120 deg F) the

fan is activated.

To simplify the installation of the system, particular attention has been given to providing

a system that minimizes on-site fabrications of mounting hardware, cables and

components. Typically, the installer is only required to mount system components, run the

prefabricated interconnecting cables, plug the cables into their mating connectors, power

the system up and verify system operation.

An expansion path is provided to increase the number and type of sensors (Methane

content, digester temperature, digester pressure, blower control, mixer monitor and

control, rain water pump monitoring, electrical power consumed, power co-generation,

etc). On-site enhancements are greatly simplified through the use of industry standard

interfaces. When the optional RMAC is included, the system software can be updated or

re-programmed remotely. In many cases additional sensors can be configured, installed at

Feb 15, 2010

the site and plugged into existing connectors already available on the DMCS.

DIGESTER MONITOR & CONTROL SYSTEM

Feb 15, 2010

SYSTEM BLOCK DIAGRAM

2.0 SYSTEM COMPONENTS

2.1 Data Logger

The data logger is a rugged, low-power instrument that samples analog and digital inputs

from various sensors, formats the data, then stores it to memory for later uploading to a

central data storage facility. In addition to data acquisition and recording, the logger

simultaneously performs various control functions required for the operation of the

system. Threshold limits can be specified and alarms can be activated when a parameter

exceeds a specified limit. With its rugged design, it is well suited to outdoor

environments. As a low-power instrument, it is also well suited for battery operation.

Data is off-loaded from the data logger via an Ethernet enabled computer or via the

optional Remote Monitoring interface. Sensor values may also be viewed locally via the

built in Liquid Crystal Display.

A special automatic reset circuit is incorporated into the system design to add additional

reliability to the system. This circuit, called a Watch-Dog Timer will force the logger

microprocessor to reset and then continue operation from where it left off in the event

that an unforeseen hiccup or noise glitch (for example, from a nearby lightning strike)

causes the microprocessor to freeze. This circuit will restart the system in a controlled

manner without the lost of any data. Although this circuit does not operate under normal

conditions, it adds one more level of robustness to the system.

Feb 15, 2010

2.11 USER INTERFACE

Various front panel features are built into the logger to provide a local operator interface.

These functions are protected inside the locked, weather-tight enclosure.

LIQUID CRYSTAL DISPLAY

An extended temperature range 4-line by 20-character Liquid Crystal Display (LCD) is

provided. Information such as Operational Mode, System Status, Alarm Messages, and

sensor readings can all be displayed on the LCD.

PUSH BUTTONS

Located along the left edge of the front panel are five momentary push buttons providing

basic logger operational control. Details on the button functions follow:

● NEXT and SELECT

The NEXT and SELECT buttons are used for user control of the (LCD) menu

display. Pressing NEXT will advance the display to the next menu. Pressing the

SELECT button selects that menu item and a new menu or results are displayed.

● ENABLE

The ENABLE button initiates the execution of the current control program. The

display will normally change to ENABLED.

● STOP

Pressing STOP at any time causes the logger to finish sequencing through the

currently executing program. At its completion the display shows STOPPED.

● RESET

A hardware reset of the logger microprocessor can be performed by

Depressing and releasing both the STOP and RESET buttons at the same time.

This function is only available for diagnostic purposes. Under normal conditions

there is no requirement for the operator to initiate this sequence.

POWER SWITCH

An ON/OFF power switch is provided in the upper right corner of the logger. As in the

case of an unexpected power failure, cycling the power switch off while the logger is

logging will not result in any data loss. The logger circuitry detects the collapsing supply

voltage and closes out all logging operations before the voltage level drops to an unsafe

level. Upon return of power, the logger will awaken, assess its status prior to the power

failure and continue where it left off.

Feb 15, 2010

PROGRAMMABLE LED INDICATORS

Two green LED indicators (labeled Status) are located at the center top of the logger front

panel. These indicators are under program control and can be programmed for any

operational feedback.

LED INDICATORS

Front panel LED indicators provide feedback on status of relay outputs, Ethernet

connection and user-defined logic signals within the control program.

DMCS DATA LOGGER

Feb 15, 2010

2.2 POWER CONDITIONING SUB-SYSTEM

The Power Conditioning Sub-System consists of three main elements: (1) power source:

solar or shore power, (2) battery charge controller and (3) battery. Normally the power

for the system is provided by a 65 or 85 Watt high efficiency solar module. If shore power

is available, the solar module can be optionally replaced by a battery backed up universal

uninterruptable power supply (UPS). The solar module is sized to operate the system and

maintain the battery charge on a typical cloudy day for the location at which the system is

installed. Under normal conditions the system will operate continuously without any

operator intervention.

The charge controller is the core of the Power Sub-System. It is responsible for both

providing power for the system electronics and keeping the battery charged. The

controller is 100% solid state and provides a temperature compensated charging voltage

to the battery. To protect the battery from deep discharge, it includes a low voltage

disconnect feature that automatically disconnects the load when the battery voltage falls

below a predetermined low voltage set point.

The battery is a deep cycle 12 volt 35 or 75 Ah sealed AGM lead acid battery. It is sized

to provide operational power to the system for up to 5 consecutive days should the

charging source fail. The battery voltage and charge current is continually monitored and

recorded by the data logger.

2.3 GAS FLOW SENSOR

The gas flow sensor is an integral style industrial in-line mass flow meter. It is a thermal

dispersion type, using a constant temperature difference method of measuring Mass Flow

Rate. It contains two reference grade platinum Resistive Temperature Device (RTD)

sensors clad in protective 316 stainless steel sheaths. Features include direct mass flow

reading of gases, built in totalizer, wide range ability, low pressure drop, very low end

sensitivity and no moving parts.

The power dissipation is under 2.5 watts making it ideal for solar powered systems. The

electronics are housed in an Integral Style, Explosion Proof, NEMA 4X windowed dual

compartment enclosure with a local display. The display is a high contrast photo-emissive

Organic Light-Emitting Diode (OLED) display. It displays current Flow Rate, Totalized

Volume and Gas Temperature. A graphical representation of Flow Rate is depicted in a

horizontal bar graph format. In addition, the calibrated milliwatts (mW) value is

continuously displayed. All of these parameters are available to the data logger and can be

included in the logged data.

Calibration Self Check: The Flow Meter has built in diagnostics – the display of the

calibrated milliwatts (mW) can be used to check the sensor’s operational accuracy by

comparing its value to the original recorded “zero flow” value noted on the meter’s

Certificate of Conformance document (also depicted on meter’s identification label). As

Feb 15, 2010

long as these values match when there is zero flow the meter calibration should match

that when it was originally calibrated. The manufacturer’s quoted accuracy is +/- 0.5% of

Full Scale, +/- 1% of reading with a turn-down of up to 1000 to 1. Repeatability is 0.2%.

MASS FLOWMETER

2.4 FLARE TEMPERATURE SENSOR

A N-Type thermocouple is used to sense the combustion temperature of the flare.

It is physically mounted on the flare and is exposed to the flare’s internal flame.

N-Type thermocouples can measure temperatures up to approximately 1300°

Celsius making it well suited for measuring extremely high temperatures. It

consists of the junction of two dissimilar metals. When exposed to heat it

generates a small electrical current that is directly proportional to its temperature.

A thermocouple is a differential rather than an absolute measuring device. A

known reference temperature is required for one of the junctions if the absolute

temperature of the other is to be inferred from the output voltage. The data logger

has an internal temperature sensor that is used as the reference.

2.5 IGNITION CONTROL UNIT

Feb 15, 2010

The Ignition Control Unit (ICU) is used to ignite the flare when adequate gas flow

is present to sustain continued combustion. It is a microprocessor based electronic

ignition unit that is controlled by the data logger. Extreme care has been taken to

minimize any Radio Frequency Interference (RFI) generated by the unit. RFI can

cause unpredictable operation of nearby electronic devices and potentially could

cause the data logger to malfunction. When the data logger senses that an

adequate gas supply is present, it commands the ICU to initiate an ignition

sequence. This sequence consists of a “three try cycle”. Each cycle consist of a 6-

second firing period followed by a 20-second pause. During the pause, the ICU’s

flame sensing circuitry checks for the presence of a flame. If a flame is detected,

the ignition sequence is terminated. If not the cycle repeats a maximum of three

times. At completion, a status signal is updated to reflect the state of the flame and

made available to the data logger. This sequence repeats every three minutes until

the flare is lit.

IGNITION CONTROL UNIT

2.6 AUTOMATED GAS CONTROL VALVE

The Automated Gas Control Valve (AGCV) is used to control the flow of gas to

the flare and electric generator, if present. It consists of a 4” PVC ball valve, a

motorized actuator, an integral pressure sensor and a microprocessor-based

controller. It allows the data logger to monitor upstream gas pressure and adjust

the gas flow. When the available gas pressure is insufficient to produce a specified

combustion temperature, the system closes off the flow of gas. The pressure of the

gas within the digester is continually monitored. When adequate pressure is

sensed, the valve is opened and the flare is ignited. The temperature of the flare is

Feb 15, 2010

continually monitored. If its temperature drops below the specified value the valve

is closed and the cycle repeats.

This sequence not only guarantees that all the gas produced by the digester is

destroyed, but the resulting combustion temperature is sufficient to qualify for

Carbon Reduction Credits.

AUTOMATED GAS CONTROL VALVE

2.7 REMOTE MONTORING ALARM and CONTROL

The Remote Monitoring Alarm and Control option provides worldwide access to

the system’s operational status. This includes logged data, system health

parameters and weather information. Virtually all operations that can be

performed locally are available remotely, including programming and configuring

the system. If required for diagnostic purposes, system parameters can be

modified and monitored in real time (this is normally restricted because of the

increased data bandwidth requirements). The DMCS typically uploads the

collected data once a day to a dedicated server. To minimize bandwidth

requirements, this data is uploaded in a proprietary compressed binary format. The

server formats the data into standard engineering units. The data is then inserted

into a relational database. Once deposited in the database, standard queries can be

performed that allow the generation of various reports, graphs and alarms. The

data is then made available to users via the World Wide Web (Internet).

Additionally, the data is continually scanned for out-of-tolerance parameters and

other events that can be set to trigger alarms. If an alarm is generated it is

immediately sent to customers via email and/or text messages.

Feb 15, 2010

3.0 DATA COLLECTION AND DISSEMINATION

There are two classes of recorded data types, periodic and event driven. The periodic type

is sampled at regular intervals and typically includes the system operational parameters.

For the Bio-Digester systems this includes the Gas Flow Rate, Accumulated Gas Volume

(totalized value), Flare Combustion Temperature, Power Supply Voltage, etc. They are

typically sampled and recorded at 10 minute intervals.

Event data types are captured asynchronously as they occur. They depict when a

particular event happened; its value, and the value of any associated parameters. An

example would be to record the current accumulated Gas Volume whenever the Flare

temperature is above or below 500°C. This allows for an accurate determination of how

much gas was produced and burned when the combustion temperature was above 500°C,

a typical requirement for Carbon Reduction Credits.

3.1 LOCAL DATA RETRIEVAL

Logged data can be retrieved either locally or remotely via the World Wide Web.

In order to download the logged data locally an Ethernet-enabled Personal

Computer is required. Typically a Laptop Personal Computer is used.

The Data Logger has a built in Web Server that can be accessed by a standard

HTTP Web Browser application (i.e. Microsoft Explorer, Firefox, etc). The

automatically generated web pages allow the operator to view and download the

collected data to a file on the PC. The file is saved in a comma delimited format

(CSV extension) that can be directly loaded into a spreadsheet application such as

Microsoft Excel or free equivalents such as Open Office or Libre Office.

When the data is displayed in a spreadsheet, a row is generated for each record

with a unique column ID for each parameter. Each record is tagged with the date

and time it was collected.

Feb 15, 2010

Typical MS Excel Spreadsheet Display

3.2 REMOTE MONITORING and CONTROL

Remote Monitoring allows access to the collected data via the Internet. All that is

required is a computer with access to the Internet and a Web Enabled application.

A unique URL is provided that will direct the application to the DMCS server.

Once logged on, the User can view, plot and download the collected data for a

particular site for a specified period. In addition, unique alarm conditions can be

defined for each parameter for each user. When an alarm condition exists, an

email and/or text message can be sent to the User. To support offline analysis of

the data, customized reports can be generated and downloaded. An example

would be to generate a report indicating when and how much gas was produced

and destroyed when the flare combustion temperature was above 500°C.

Typically the logged data is uploaded to the server once every 24 hours. It is made

available on the Internet within one hour after it is uploaded. To facilitate high

priority events, real time alarms are also supported. High Priority Alarms (HPA)

can be programmed into the data logger itself. When HPA is activated, a special

message is generated and sent to the server. The server in turn notifies the

responsible User of the condition. These types of alarms are normally reserved for

conditions that are of a time-sensitive nature, such as a digester chemical

imbalance, an impending power failure or an equipment malfunction.

Feb 15, 2010

Example – Remote Data Access Display

Remote Monitoring allows the User to continually monitor the health of the

system. With the automatic and timely execution of real time diagnostics, data can

be collected that reflects the status of the system. By periodically comparing

collected data parameters to acceptable limits, pending failures can be detected

and diagnosed early. If required, specially programmed operations can be

remotely performed. If a service technician needs to be dispatched to the site, he

will have a good understanding of the existing or pending problem and also know

what replacement components he is likely to need.

Remote Monitoring eliminates the possibility that a malfunctioning site will go

undetected for an extended period. Remote Monitoring guards against potential

loss of revenue from a malfunctioning site.

Note: Remote Monitoring and Control requires Internet access and a data

plan with dmcs-link.com, a Performance Systems-hosted and managed web

server.

Feb 15, 2010

4.0 SUMMARY

The Digester Monitor and Control System is a cost-effective turnkey solution for the

monitoring and control of Bio-Digester sites that are typically located at cow and swine

farms. Its ability to accurately record the amount of Methane gas produced and destroyed

makes it well suited to collecting information for submission for Carbon Reduction

Credits. By measuring and recording various system health parameters, early detection of

pending system malfunctions can be recognized and technicians can be promptly and

automatically notified. The use of Solar Power and Wireless communication technology

greatly reduces installation costs and enhances system reliability. The use of industry

standard sensor interfaces provides an almost endless expansion capability. The Remote

Monitoring capability provides users world wide with near real-time performance data.

Digester Monitor and Control Systems - dmcs-link.comdmcs-link.com/SysDiscription_E-k1.pdf · that...

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