The range of combined heat and power plants (CHP) is quite large, as may be the high variance of different plant types. The distinction is made by the generated power/heat output on the one hand and by the energy source used on another. For several CHP plants, a large number of physical parameters are measured, evaluated and monitored to ensure the longest possible service life. This article offers information regarding which measuring instruments and principles this can be achieved with.
Combined heat and power plants ? environment-friendly power generators
In contrast to the traditional boiler or condensing boiler, the CHP plant generates both electricity and heat. Thus, CHP plants make a significant contribution to environment-friendly energy generation.
Wide variety of applications
The versatile application possibilities, from single or multi-family dwellings, through industrial and commercial, public facilities, around large district/local heat utilities and also biogas plants, require the use of very different measuring instruments. Key factors are: functionality, quality, long service life, fast availability and services. The price/performance ratio plays a special role in virtually any system ? large or small.
The physical measurands
Small nano plants from 1 kWel, micro and mini plants from 2.5 to 15-50 kWel, and also large plants up to 4,500 kWel need the right measuring instruments for high efficiency and environment-friendly energy generation. The measurands pressure, temperature and level are dominant. The energy source must be considered when selecting the instruments. The quantity of marking points in the schematic illustration of a CHP plant helps it be clear: There’s much to monitor to assure the longest possible service life.
Schematic illustration of a combined heat and power plant incl. measuring points
Monitoring and control tasks
The measuring instruments used fulfil important monitoring and control tasks and are generally electronic measuring instruments. They also enable remote monitoring.
For measuring the temperature, screw-in, insertion and contact probes are installed, matched to the design and the area available. On heat exchanger, in the cooling and heating circuits and also for measuring the engine oil temperature, Pt100, Pt1000, KTY and NTC measuring elements are used. With Ethical , temperatures on the exhaust pipe and on the cylinder head are monitored using thermocouples. This enables conclusions to be made about the effectivity of the engine.
Pressure switches and pressure sensors are accustomed to control the oil pressure and the pressure in the cooling water circuit. At the same time, they also fulfil a safety function. If you can find any deviations between the SET and ACTUAL value, depending on the concept, either a warning signal is triggered or the engine is switched off.
To monitor the oil level, with regards to the size of the machine, between one and three float switches are installed. Particularly in large engines, the sometimes very strong vibrations pose a challenge for the measurement technology. The utilization of optoelectronic level switches that tolerate high temperatures and that are not harmed, even by strong shocks, is therefore ideal. The respective level switch monitors the oil level in a reservoir and signals once the oil level drops too low.
Complete of measuring points and the widely differing measuring tasks require close cooperation between your CHP plant manufacturer and the manufacturer of the measurement technology. Therefore, it is worth ? both technically and economically ? choosing a supplier who offers everything from one source.
Note
WIKA supplies a large selection of reliable measuring instruments for pressure, temperature and level. You could find selected products for the CHP plant on the WIKA website in the Combined heat and power plants section. Do you want support with the compilation of your measuring instrument package for your CHP plant? Your contact person will be happy to assist you to.