Innovative Control Technology

SPECIAL PRINT

Smart Automation in Heat Generation Plants

Thomas HilbigSAMSON AG

Special print from
EuroHeat&Power 3/15

Special print from
EuroHeat&Power 3/15

Smart Automation inHeat Generation Plants“Smart automation” has become a buzzword, not only amongplanners and engineers of industrial applications. In heat supply, implementing smart, efficient control systems to economically operate plants is equally important.
The requirements placed on automation systems used in thermal plants are growing more and more complex. Today, thefocus no longer lies on controlling the instruments in the plants,i.e. valves, pumps and actuators: the market sets new challenges in terms of smart control systems for the manufacturers. For
example, reading data from smart heat meters, visualizing entire plants, and making logged data readable are basic requirements to be complied with when implementing projects.

Of course, the same requirements apply to district heating applications, particularly if they are installed in large properties
or entire residential areas. To distribute the heat generated in
the heating plant without wasting energy and thus cost effectively across the residential areas, more and more energy suppliers install heat exchanger applications in small transfer stations spread across the heating network. The district heat provided is routed through heat exchangers and distributed to theconsumers as required. If large-scale consumers, such as
property management companies, use central heat transfer
stations to distribute the delivered district heat to several
apartment blocks, they usually implement heat exchanger sequence control.

Fig. 1: Hydraulic scheme of the plant3

Special print fromEuroHeat&Power 3/15

SAMSON Controls supplied the customer with electric controlvalves, flow regulators, sensors, thermostats, and theTROVIS 6600 Automation System for smart automation of theheat exchanger sequence control loops. But what tasks exactly
does “smart automation” entail in heat supply?

Fig. 2: Central TROVIS 6610 CPU Module of the TROVIS 6600 Automation
SystemThis allows the received thermal output to be reduced in times
of weak loads by shutting off the heat exchanger connected insequence. In peak load times, however, the full capacity isrequired. As a result, the automation system releases the sequence heat exchanger, controls the flow temperature, monitors the return flow temperature – optionally for violation of a
fixed limit or a value depending on the outdoor temperature –,and controls shut-off butterfly valves and supply pumps.
These requirements make it necessary for manufacturers to nolonger act as mere suppliers of devices but to provide customers
with comprehensive turnkey solutions.
SAMSON has already completed a large number of projects inGermany and abroad. A current example is the residential
area scheme implemented in the English city of Nottingham byVital Energi, Enviroenergy and SAMSON Controls. Each of two
residential areas is connected to the existing district heating network using a heat transfer station.
At each station, heat exchanger sequence control is implemented but sized and configured differently to cater for thedifferent capacities consumed in the secondary circuit. The
first station comes with two heat exchangers each delivering
600 kW at a connection size of DN 65. In the primary circuit,the temperature ratio is 110 °C to 70 °C, in the secondary
circuit 85 °C to 65 °C. In the second station, delivery of eachheat exchanger is 1 MW with a connection size of DN 80
installed in the primary circuit and DN 125 in the secondarycircuit.
4Heat exchanger sequence
Each heat exchanger is fitted with an electric control valve inthe primary circuit and a shut-off butterfly valve in the secondary circuit. The flow and return flow temperatures are measured
in the supply line and in the customer circuit, and binary operating and fault messages are recorded. These messages aretransmitted to the TROVIS 6600 Automation System. The systemis scalable with the central TROVIS 6610 CPU Module performing the smart plant management. The CPU module is a freely
programmable control unit with 20 universal inputs to optionally record binary or analog signals. In addition, twelve binary
outputs and eight continuous voltage outputs are available. The
system can be extended using different I/O modules, i.e. it canbe adapted individually to match customer requirements.
Set points, parameters and characteristics are adjusted on thetouch panel in the switching cabinet or on a mobile device.
The implemented application calculates the secondary flowset point depending on the outdoor temperature, optionallybased on a gradient or four-point characteristic. Of course,operators can also adjust a fixed value. To ensure that theheat exchangers work for nearly the same time, all heat exchanger demands are routed through an operating hours
counter. If the operating time exceeds an adjustable threshold,the sequence of the heat exchangers is switched, causing theexchanger so far used on stand-by to take over control operation. The system detects faults occurring in a heat exchanger
branch and immediately releases the second heat exchanger.
Fault messages can be issued, for example, when the safety
temperature limiter has been triggered or when the butterfly
valve does not respond to a heat exchanger demand. The
shut-off butterfly valves installed in the secondary circuit prevent the medium from flowing through a heat exchanger without demand and thus stopping the loss of heat energy. The
primary return flow temperature is monitored for violation ofa limit. If the measured temperature exceeds this limit, the flow
set point is reduced accordingly. As a result, the system onlyintervenes in control operation to the degree required for theparticular situation.

Double pumps
Pumps account for approximately ten percent of the worldwide energy consumption. The challenge in smart automation is to minimize the pumps’ operating hours and speeds inevery plant. Vital Energi opted for installing double pumps
controlled by the differential pressure into the heat transferstations. This plant section is controlled by the TROVIS 6600
Automation System as well. The differential pressure sensors
are connected to the automation system using a 4 to 20 mAsignal. Operators can flexibly adjust the differential pressure
set point on the graphical user interface. Based on the difference between set point and actual value, a control algorithm
calculates the perfect pump speed. Pump use is also switchedbased on the operating hours. Alternatively, pump control
can be configured in split-range operation. The web interface

Fig. 3: Electric control valve with flow regulator to control the primary
bypassadditionally allows for manual operation of all plant components at any time, even from remote locations. To ensure thatthe pumps achieve their minimum speeds during low-load
operation without having to transfer too much heat energy
into the heating network unnecessarily, Vital Energi included
a pump bypass. The pump bypass is opened based on alinear function when the calculated pump speed is lower thanthe pumps’ minimum speed. This enables the system to operate the double pumps in an efficient and economically viableway.
To also minimize the speeds of the network pumps for theheating network operator, an additional bypass has been integrated into the primary circuit of the system. This bypass
allows the heat exchanger sequence control to be shut off thenetwork entirely. The bypass can be closed when the network
temperature and heat demand are low during the summermonths. This prevents the flow from being routed through unused heat exchangers without demand.
Recording meter data
In addition to actually controlling the system, analyzing consumption data is becoming more and more important. In
most cases, these data are read from the smart heat meters
using the meter bus or M-Bus. The bus uses electric datatransmission and shows little susceptibility to faults, whichmakes it perfectly suited for use in thermal systems wherefrequency-driven pumps have meanwhile become the standard choice. In the heat transfer station in Nottingham, theheat meters are connected to the TROVIS 6600 Automation
System using SAMSON’s own gateway. The gateway converts the M-Bus signals into the TCP/IP protocol, which allows
the meter data to be read and processed by the smart automation system. The system automatically reads the meter address and saves the measured flow and return flow temperatures, flow rate, capacity and work with their associated units
into a file. Operators can use the web interface to configure
the interval at which data are saved. Possible options are
every 15 minutes as well as once per day, month or year.
Operators can also decide on the contents and format of thelog file. As the data can automatically be polled over the Internet, importing them into a billing software is possible without any problems. The recorded data can just as easily bevisualized on the automation system’s graphical web interface. As a result, consumption can be analyzed over the yearand savings potentials can be detected and exploited.
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Special print fromEuroHeat&Power 3/15

Fig. 4: Overview of parameters on the TROVIS 6616 Web Terminal

Plant visualization
To transparently illustrate the processes that go on for the operators, TROVIS 6616 Web Terminals fitted with a touch screen
are installed on site.
The web terminal has a 7” graphical touch screen with anAndroid-based operating system. On screen, all plant parameters can be adjusted, manual override is possible, andalarm messages can be checked. All logged data can additionally be shown in a historical trend graph. Unauthorizedaccess is prevented by different, password-protected user levels. This is why a function that automatically signs out users
after a certain period of inactivity is already preconfigured.
To minimize the wiring required, the web terminal comes witha Power over Ethernet connection. Plants are entirely visualized according to customer specifications and the visualization is saved in the TROVIS 6610 CPU Module. As the web
terminal also includes a fully fledged web browser, access tothe TROVIS 6610 CPU Module website is possible in addition
to plant visualization. This means that no computer is required on site to adjust or change plant settings or to configure alarm notification by e-mail or mobile text message, forexample.
All in all, smart automation in heat generation plants enables
systems to run efficiently. This helps reduce the operators’ costand get a return on the money invested into a new plant. For
manufacturers, there is the opportunity to convince customers
with tailor-made solutions as well as fortify their importantrole in implementing new energy policies.
6Thomas Hilbig, B.A.,
Product Management and Marketing,Instrumentation and Controls, SAMSON AG,
Frankfurt am Main, Germany
E-mail: thilbig@samson.de
Phone: +49 69 4009-1744

8SAMSON AG · MESS- UND REGELTECHNIK · Weismüllerstraße 3 · 60314 Frankfurt am Main, Germany
Phone: +49 69 4009-0 · Fax: +49 69 4009-1507 · E-mail: samson@samson.de · Internet: www.samson.de

2015-04 HD · WA 335 EN

SMART IN FLOW CONTROL.