EEN-E1040 Measurement and Control of Energy Systems Control II: Controlled devices, control in energy technology, complex systems Nov 7th 2016

Controlled devices Practically any device that can be adjusted Valves, dampers, heaters, motors, lights… During this lecture, devices importart in energy technology are presented

Valves and dampers Used for directing/regulating flows Valves for gas/liquid flows, dampers for air flow in ducts Can be manual or with hydraulic/electric actuators

Typical valves 2-way valve Flow rate control ON/OFF (shut-off valve) or proportional (flow control valve)

Typical valves 3-N way valve Mixing, flow direction ON/OFF (selector valve) or proportional (mixing valve)

Special valves Thermostatic mixing valve Typically used in heating applications (domestic hot water etc.) Mixes two flows at different temperatures and ensures output does not exceed a set temperature

Special valves Line balancing valve Used for balancing systems after commissioning Pressure measurement connections Well-defined characteristics for obtaining desired flow rate

Valve parts Stem Body Port A Port B Seat Disc

Valve operation and characteristics Valve operation described by Kv flow factor of the valve (m3/h) Δp pressure drop over valve gs specific gravity of liquid (one for water) Kvs = flow factor with fully open valve and pressure drop of 1 bar Provided by manufacturer, important when choosing a valve Main part of valve characteristics

Valve operation and characteristics Valve authority: Δpv,open/(Δpv,open + Δpsystem) Defines how well the valve can control the system Should be 0.5 – 1 for good controllability Estimate Δpsystem Calculate required Δpv,open to get a good authority Put the result in the equation from previous slide along with desired flow rate to get Kv for your valve Select a valve with Kvs at least 30% larger than the obtained Kv

Valve linearity Graph taken from http://www.maintenanceresources.com/referencelibrary/controlvalves/cashcoflowchar.htm

Heating elements Used for converting electric power into heat Metallic coil/wire heats up due to resistance Heating power directly proportional to electric current passed through the element

Controlling a heating element Most commonly ON/OFF control, proportionality achieved by rapidly switching the element on and off Cheap to construct Overshoot becomes problematic if the element is very powerful Exercise in this course a good example True proportional control with electric power limiters Tyristors, TRIACs etc. Small scale devices affordable, large power and/or 3-phase applications very costly

Motors Used to generate motion from electricity Based on electromagnetism: current loop in a magnetic field starts to rotate

Motors - applications Found in various sizes from micrometer to meter scale Typical applications in control and energy systems: Pumps Valve and damper actuators Cooling fans, air handling unit fans

Controlling motors Two main types of motors: DC and AC DC motors utilize similar controllers as electric heaters AC motors typically controlled with inverters Based on modifying the frequency of the AC

Control in Energy Technology: Building automation High-level controller Supervision of systems User interface Low-level controllers Subsystem control HVAC, lighting, safety, energy, security etc. Image from http://www.regelgroup.com/main/building-automation-systems-bas/

Control in Energy Technology: Nuclear power plant Reactor operation Control rods Pressure Temperature Steam Flow Cooling Reactor coolant Image from http://preview.flowserve.com/files/Files/Images/Industries/static/020-I-Nuclear-BWR.png

Control in Energy Technology: Nuclear power plant

Control in Energy Technology: Nuclear power plant

Control of complex systems: nZEB emulator in HVAC laboratory Process variable TE102 Brine return temperature to ground source heat pump Controlled by Brine-filled buffer tank 3-way valve FCV103 Plate heat exchanger connected to city water 2-way valve FCV105 Selector valve V106 Varying conditions Buffer tank temperature Long dead time Nonlinearity