Measurements Matter in Wind Energy Production – DAQ systems for Wind Farms
Locating and exploiting new and ever greater sources of oil, gas and coal is
increasingly difficult, as highlighted by the current problems in the Gulf of Mexico; the costs of extracting such fuels will inevitably continue to rise pushing prices to the consumer up.
Importing energy can also make a country vulnerable – for example a dispute in 2009 between Russia and the Ukraine led to gas pipelines being turned off resulting in supply outages across Europe.
Pollution and rising CO2 levels in the atmosphere, which many
scientists believe to be a major contributing factor to global warming, will only get worse as fast paced development in countries like China lead to more and more fossil fuel based power generation.
Nuclear energy offers a possible
alternative but there are pros and cons involved which I won't go into in here.
Harvesting the natural, ren - ewable energy from the world around us, however, will allow us to reduce our reliance on fossil fuels,
lower our collective carbon footprint and become more energy self sufficient.
The EU has set a binding target that 20% of its energy supply be renewable by 2020 and to meet this target a third of all electricity generation must come from renewable sources by that time.
However, selecting suitable sites, choosing the most appropriate technology and systems, monitoring output and forecasting energy generation all require accurate measurements of meteorological parameters to be made.
The Hunt For Suitable Sites – Wind Prospecting
Wind generated electricity is the fastest growing renewable energy sector and Europe remains at the forefront of the market. By 2020 it is predicted that between 12 and 14% of the EU's electricity demand will
be fulfilled by wind energy – this will save an amount of CO2 equivalent to taking 165 million cars off the roads. Measurements matter in wind energy as we seek new locations and improve efficiencies.
The starting point for expanding wind power capacity is finding suitable new sites for turbine installations. There are published maps giving estimated wind resource for many areas and 'wind prospecting', as this process is sometimes called, often starts with such maps. However, wind is notoriously fickle and whilst map accuracy is improving all the time site specific measurements remain a necessity for large and utility scale wind farm projects to ascertain the commercial viability of a site.
For domestic and even some small commercial projects however the cost of pre-installation assessment is prohibitive and so turbines are installed with only a limited understanding of the likely pay-back period using general wind maps and data from nearby airports or other calibrated weather stations.
Wind Resource Assessment
There are three technologies in use for such resource assessments – Lidar, Sodar and cup anemometry. Lidar and Sodar both work on a similar principal with one using pulses of light and the other of sound to measure wind speed and direction by monitoring the reflected signals. The advantage of these devices is that they give measurements at any height across a set range. However, these devices typically require generators where mains power is not available (i.e. most sites) and there are obvious issues with this - for example regular site visits to keep the generator fuelled and a risk of data gaps caused by mechanical breakdown. However, for many people it is the incongruous use of a diesel powered generator as part of green energy study which makes cup anemometry the preferred route.
Conditions at prospective sites are typically far from ideal – access is often difficult, and usually there is no mains electricity or fixed line communication systems, and sometimes no mobile network coverage either. The other thing about such sites is that, strangely, they tend to be very exposed and windy places making working conditions difficult, especially in winter. This means that a monitoring system has to be simple to install, be pre-tested off-site, offer outstanding reliability, include a viable telecommunication platform and operate autonomously 24/7/365 from a sustainable power source.
Solar Powered Data Acquisition.
A typical mast based set-up involves several cup anemometers and wind vanes mounted at various heights on a meteorological mast of up 80 – 100m tall. Sometimes two sensors will be positioned at each height to provide redundancy in case the primary sensor fails. Other parameters such as air temperature, relative humidity, vertical wind speed, barometric pre ssure and solar radiation can also be measured as these elements can be used in wind modelling. For large sites several identical towers (same sensors, same mounting heights) will be erected so that a full site profile can be built up using correlated data from all the masts. The use of multiple systems also serves to provide red undancy in case of data gaps in any single masts dataset. A pre- programmed data logger, back-up battery and comm -
Data loggers such as Campbell Scientific's CR1000 control the monitoring station and process and store the data on-board for later remote collection.
unications modem would be housed in an enclosure at the base of the tower to control the system and collect and process the data. The enclosure components will normally have been pre-wired to external connectors making on-site sensor connection as easy as possible – ideal for glove wearing engineers battling against icy cold winds. The whole system would be powered by a solar panel making it suitable in virtually any situation/location.
AUTHOR DETAILS Iain Thornton
Marketing Manager Campbell Scientific Europe Campbell Park 80 Hathern Road, Shepshed, Leicestershire, LE12 9GX, UK Tel: +44 (0)1509 601141 Fax: +44(0)1509 601091 Email:
iain.thornton@
campbellsci.co.uk Web:
www.campbellsci.eu
Sensors would normally be sampled every two seconds with 10 minute averages being recorded along with standard deviation and maximum and minimum data. A data logger such as the Campbell Scientific CR1000 would make these measurements and process the data, converting the sensors output into engineering units for final storage on-board for later retrieval. All data is date and time stamped.
Long Term Monitoring
Successful wind farms rely on pre-installation site measurements to prove the sites viability for profitable wind power generation.
Sites will be continuously monitored over 12 or 24 months in order to provide a detailed profile of the wind speed frequency distribution throughout the year. However, even 24 months of site specific data may not be representative of longer term wind patterns and so site data is often correlated with long term reference data taken from nearby calibrated weather stations such as those found at airports. Measurements really do matter here as just a few percentage points of error can mean the difference between profit and loss.
IET
Annual Buyers Guide 2010
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