Geothermal Power Station Monitoring

Application Background

Geothermal electric power stations are generally located where high temperature geothermal resources are available near the surface, often near areas where there are natural hot springs. Geothermal power stations pull hot water / steam from the ground, use it to run turbines and then return the water back to the original source. The three basic designs for the geothermal power stations are:
• Dry steam – steam goes directly from the ground to the turbine
• Flash steam – hot water is “depressurised” in to steam that then dives the turbine
• Binary cycle – hot water is used to heat secondary liquid, one with the lower boiling point than water. Using secondary liquid allows for production to be varied, can be increased or decreased multiple times each day, so energy produced can match actual demand.

Geothermal energy systems offer a cleaner, more sustainable renewable energy, that can supply regular, continuous power but it can still have negative impact on the environment, people and wildlife. Water, air and land can be affected. Water pumped from underground contains high levels of harmful chemicals like sulfur, so it is important to ensure that used water is not returned in to the environment. The power stations that have a loop air system emit gases from the extraction well, like hydrogen sulfide, known to smell like rotten eggs, into atmosphere.

The problem with hydrogen sulfide (H2S) is that when in contact with the oxygen in the air (O2) changes into sulfur dioxide (SO2). 2H2S + 3O2 «–» 2SO2 + 2H2O

Sulfur dioxide is found to cause heart and a lung disease, acid precipitation, which then damages plants, soils and acidifies water bodies. Pumping large amounts of water from the geothermal reservoir can cause land surface to sink and use of fracking process increases already high risk of earthquakes. The constant monitoring and reporting is imperative when a geothermal power station is located near populated areas.

Application Detail

Firstly, there will be a requirement to monitor the weather in the area using Tier 2 weather station equipment to record the ambient conditions, especially wind speed and direction, so there is good knowledge of the general wind conditions to make sure emissions from the plant are not being carried by the wind to areas of population, such as a local town or city. There may be the need for one Tier 2 to be installed at the plant and at each perimeter fence of the facility to get a good reading for the local area.

Unidata supplies various weather station instruments, either a multifunction ultrasonic weather transmitter, which is very convenient to install, as well as separate discrete weather instruments. For this application, the simpler ultrasonic weather transmitter would most likely be the best choice for the application. To provide telemetry option, a Neon Remote Logger can be connected to each weather station and be set up to read the instruments every minute, store the raw and average readings every 5 minutes, and then transmit the data to a central Neon Server every, say, 15 minutes.

As well as weather station equipment that measures weather conditions such as wind speed, direction, humidity, temperature, solar radiation etc, there would also be a requirement to add additional instruments to measure the presence of noxious gases and seismic activity. There are many manufacturers of gas monitoring equipment. One such manufacturer is Dräger and there are sensors to measure noxious gases such as CO, CO2, NO, H2S, SO2 as well as O2and N. These instruments typically provide a 4-20mA analog output or a Modbus output which can be read by Neon Remote Logger routinely, perhaps every minute and then routinely send the data to the Neon Server every 15 minutes. The system could also be equipped with a ground seismic monitor to take daily readings of seismic activity. This way, so a clear pattern of the base level of seismic activity can be determined, and then used as a reference for monitoring the effects of the geothermal power station activities.

The Neon Remote Logger scheme / program can also be set up to check parameters each minute and raise an alarm and an immediate transmission to the Neon Server in the event of any reading is outside it’s preset limits. The Neon Server can also be set up with alarm actions, to notify staff by email or text, with an escalation process, of any out of limits conditions. As well as the immediate actions to deal with for high / dangerous gas levels, data can be analysed and long term trends can be determined to help minimise environmental impacts and optimise production.

Finally, water quality measurements for any outflows can be important, so a water quality instrument on any outflows would allow outflows to be checked for quality, to maintain environmental compliance. These instruments can also be connected with a Neon Remote Logger to the central Neon Server, either with a radio link, or buy connecting directly into the plant network using an Ethernet cable.

Typical Configuration

Options for Application Specific Instruments / InputsUnidata Part NumberDescription
Drager Gas Detection InstrumentsDrager MiniWarnCO2/CO Gas Monitor
Vaisala Weather Transmitter WXT5366501V-HVaisala Weather Transmitter measure barometric pressure, humidity, precipitation,
temperature and wind speed and direction
Temperature Thermistor Probes6507ERed Thermistor Probe 3K@25C with requested cable lengths
Linear Temperature Probe6535ATemperature Probe LM34 with requested cable lengths
Humidity and Temperature Probe6539BHumidity and Temperature Probe
Rain Gauge6506CRain Gauge/Tipping Bucket
Mounting Arrangement for Temperature Probes6704ARadiation Gill Screen and Mounting - Full Size
Mounting Arrangement for Temperature Probes6704BRadiation Gill Screen and Mounting - Half Size
Radiation Sensor7241C-APyranometer Sensor – Solar Energy
Mounting Arrangement for Pyranometers7241MPyranometer Sensor Instrument Mounting and Hardware
Four Electrode Conductivity Instrument6536E4EL Water Conductivity Instrument
Four Electrode Water Conductivity Probe6536P-2-X4EL Water Conductivity Probe with 10m, 20m, 30m or 50m of cable

Options for Neon Telemetry - NRL / NRT / RTU / Field UnitsUnidata Part NumberDescription
Neon Remote Logger 16 Channels3016AOptions Available: 3G/4G Cellular, Ethernet, Globalstar, Inmarsat, Iridium SBD and LoRa
Neon Remote Logger 8 Channels3008AOptions Available: 3G/4G Cellular, Ethernet, Globalstar, Inmarsat, Iridium SBD and LoRa
Neon Remote Logger 4 Channels3004AOptions Available: 3G/4G Cellular
Neon Remote Logger 4 Channels M Series3004A-MOptions Available: 3G/4G Cellular, Ethernet, Microsatellite, Iridium SBD and LoRa
Cellular RTU 3G/4G2013F-AB03 / 2013F-AB04Neon Metering Module 3G/4G with Antenna and Li Battery
Cellular RTU 3G/4G - Industrial2016F-AB03 / 2016F-AB04Neon Remote Terminal 3G/4G with Antenna and Li Battery
Low Earth Orbit Satellite Globalstar2015F-AB0NRT Satellite Globalstar Modem with Antenna and three Li Batteries
Ethernet2017F-0B0-1 or 3NRT Ethernet with single or triple Ethernet Ports with three Li Batteries
Equatorial Orbit Satellite - Inmarsat2018F-AB0-1 or 3NRT Ethernet with single or triple Ethernet Ports with three Li Batteries
LCD Display2500ENRT LCD Display
NRT Field Termination Strip2103F2015F,2016F,2017F, and 2018F NRT FTS
NRT Firmware Option2303A-8M8M Extended Memory Option
NRT Firmware Option2303A-8M-CAM8M Extended Memory & Serial Camera Option
NRT Firmware Option2303A-CAMSerial Camera Option

Options for Neon Application Software - Customer ServerUnidata Part NumberDescription
Neon Application Software2302ANeon Server Software Licence Incl 5 NAL
Neon Application Software2302A-10Additional 10 NRT Access Licences
Neon Application Software2302A-20Additional 20 NRT Access Licences
Neon Application Software2302A-50Additional 50 NRT Access Licences

Options for Neon Application Software - Unidata ServerUnidata Part NumberDescription
Neon Application Software2301ANeon Data Initial Subscription Setup Fee
Neon Hosting Service2301A-01Neon Data Service Fee for 1-50 NRTs
Neon Hosting Service2301A-02Neon Data Service Fee for 51-100 NRTs
Neon Hosting Service2301A-10Neon Data Service Fee Metering

Options for Conventional Dataloggers / Field UnitsUnidata Part NumberDescription
Neon Remote Logger 16 Analog Channels / Touch Screen Display3016A-00016 Ch NRL (Superseded Prologger 7001D)
Neon Remote Logger 8 Analog Channels / Touch Screen Display3008A-0008 Ch NRL (Superseded Stalogger 6004D)
Neon Remote Logger 4 Analog Channels / Touch Screen Display3004A-0004 Ch NRL (Superseded Micrologger 8010C)
Starlog V4 Management Software6308A-AUEStarlog V4 Full Licence Key