When you’re running an electricity grid, the more renewable power you have in your mix, the more you fear unexpected ‘wind ramp events’. Tornadoes, ice storms or other extreme weather events can interrupt the spin of wind turbines, so that you have to ramp up baseload generation to meet demand. Highly-tuned next-day probabilistic forecasts for each precise location would let you integrate wind power more aggressively into your supply-side balancing act.
Which is just what US utility Xcel Energy will be getting from the National Center for Atmospheric Research (NCAR). Under a new two-year programme, a variational Doppler radar analysis system will combine radar data with computer simulations to forecast the weather conditions for individual wind farms. Xcel’s regional control centres can integrate these forecasts with a growing body of data on past output performance, for a much better indication of how much power the grid can count on from a source.
A further boost to NCAR’s capabilities for predicting sunshine will indicate the likely impact of all those solar panels on the supply and demand equation. Grid managers will be able to tell when customers with rooftop photovoltaics will meet their own demand, when they’ll be contributing excess electricity to the grid, and when they’ll need to pull power from utility sources.
Britain needs accurate forecasting for renewables just as much. Even if it’s less affected by extreme events, says Forum for the Future’s energy analyst Iain Watt, better mapping of the impact of the country’s notoriously complex weather patterns is critical in managing intermittency as the proportion of renewable power in the mix continues to rise. On a windy day, grid-connected wind farms may already be supplying 10% of the electricity the country’s using at a particular moment. Simultanously, the yield from solar panels is going up and down. And minute by minute, grid controllers are matching fluctuating demand against the sources they have available at that moment.
“Forecasts of intermittent generation are becoming increasingly critical to planning and operation of our transmission system”, says Isobel Rowley of the UK’s National Grid, “as the proportion of renewables increases.” – Roger East
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