Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

NREL calculates emissions & costs of power plant cycling necessary for increased wind and solar

25.09.2013
New research from the Energy Department’s National Renewable Energy Laboratory (NREL) quantifies the potential impacts of increasing wind and solar power generation on the operators of fossil-fueled power plants in the West.

To accommodate higher amounts of wind and solar power on the electric grid, utilities must ramp down and ramp up or stop and start conventional generators more frequently to provide reliable power for their customers – a practice called cycling.

The study finds that the carbon emissions induced by more frequent cycling are negligible (

The study also finds that high levels of wind and solar power would reduce fossil fuel costs by approximately $7 billion per year across the West, while incurring cycling costs of $35 million to $157 million per year. For the average fossil-fueled plant, this results in an increase in operations and maintenance costs of $0.47 to $1.28 per megawatt-hour (MWh) of generation.

“Grid operators have always cycled power plants to accommodate fluctuations in electricity demand as well as abrupt outages at conventional power plants, and grid operators use the same tool to accommodate high levels of wind and solar generation,” said Debra Lew, NREL project manager for the study. “Increased cycling to accommodate high levels of wind and solar generation increases operating costs by 2% to 5% for the average fossil-fueled plant. However, our simulations show that from a system perspective, avoided fuel costs are far greater than the increased cycling costs for fossil-fueled plants.”

Phase 2 of the Western Wind and Solar Integration Study (WWSIS-2) is a follow up to the WWSIS released in May 2010, which examined the viability, benefits, and challenges of integrating high levels of wind and solar power into the western electricity grid. WWSIS found it to be technically feasible if certain operational changes could be made, but the first study raised questions about the impact of cycling on wear-and-tear costs and emissions.

To calculate wear-and-tear costs and emissions impacts for the new study, NREL designed five hypothetical scenarios to examine generating up to 33% wind and solar energy on the U.S. portion of the Western Interconnection power system for the year 2020. This is equivalent to a quarter of the power in the Western Interconnection (including Canada and Mexico) coming from wind and solar energy on an annual basis. The study models cycling impacts representing a range of wind and solar energy levels between none and 33%, and is not an endorsement of any particular level.

The study assumes a future average natural gas price of $4.60/MMBtu, significant cooperation between balancing authorities, and optimal usage of transmission capacity (i.e., not reserving transmission for contractual obligations). NREL modeled operations of the entire Western Interconnection for that year in five-minute intervals to understand potential impacts within every hour. With these assumptions, the study finds that the high wind and solar scenarios reduce CO2 emissions by 29%–34% across the Western Interconnection, with cycling having a negligible impact.

Cycling lessens the SO2 benefit by 2%–5%, so that SO2 emissions are reduced by 14%–24% in the high scenarios. These impacts are modeled on an overall Western Interconnection level, and changes on a regional basis could vary. Further, the study does not examine cycling impacts on mercury and air toxic control equipment now being retrofitted on coal units to comply with recent EPA regulations.

Cycling actually improves the NOx benefit by 1%–2%, so that NOx emissions are reduced by 16%–22% in the high scenarios. This is because the average coal plant in the West has a lower NOx emissions rate at partial output than at full output.

"Adding wind and solar to the grid greatly reduces the amount of fossil fuel — and associated emissions — that would have been burned to provide power,” Lew said. “Our high wind and solar scenarios, in which one-fourth of the energy in the entire western grid would come from these sources, reduced the carbon footprint of the western grid by about one-third. Cycling induces some inefficiencies, but the carbon emission reduction is impacted by much less than 1%.”

WWSIS-2 does not consider other factors such as capital costs of construction for wind, solar, fossil-fueled power plants, or transmission. These costs are significant, but outside the scope of this study, which focuses on operations.

“From a system perspective, high proportions of wind and solar result in lower emissions and fuel costs for utility operators,” Lew said. “The potential cycling impacts offset a small percentage of these reductions.”

According to the study, on average, 4 MWh of renewables displace 1 MWh of coal generation and 3 MWh of natural gas. The biggest potential cycling impact is the significant increase in ramping of coal units. Other findings include:
Because of sunset and sunrise, solar power creates the biggest ramping needs on the grid in this study. However, because we know the path of the sun through the sky every day of the year, system operators can predict these large ramping needs and plan accordingly. Solar variability due to fast-moving clouds is much less predictable, but it creates relatively smaller ramping needs.
Errors in day-ahead wind forecasts can make it challenging for operators to decide which power plants need to be online the next day. However, because forecast accuracy increases four hours ahead compared with 24 hours ahead, a four-hour-ahead decision on whether to start up those power plants that can be ramped up relatively quickly can help to mitigate these forecast errors.

Despite the differences between wind and solar in terms of grid operations, the study finds their impacts on system-wide operational costs are remarkably similar.

WWSIS-2 was supported by the Energy Department’s Office of Energy Efficiency and Renewable Energy, as well as its Office of Electricity Delivery and Energy Reliability. The study was undertaken by NREL, GE, Intertek-APTECH, and REPPAE, and underwent a rigorous technical review process that included utilities, researchers, and analysts. The study can be downloaded at www.nrel.gov/wwsis.

NREL is the U.S. Department of Energy's primary national laboratory for renewable energy and energy efficiency research and development. NREL is operated for the Energy Department by The Alliance for Sustainable Energy, LLC.

David Glickson | EurekAlert!
Further information:
http://www.nrel.gov

More articles from Power and Electrical Engineering:

nachricht The world's most powerful acoustic tractor beam could pave the way for levitating humans
22.01.2018 | University of Bristol

nachricht Siberian scientists learned how to reduce harmful emissions from HPPs
22.01.2018 | Siberian Federal University

All articles from Power and Electrical Engineering >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Optical Nanoscope Allows Imaging of Quantum Dots

Physicists have developed a technique based on optical microscopy that can be used to create images of atoms on the nanoscale. In particular, the new method allows the imaging of quantum dots in a semiconductor chip. Together with colleagues from the University of Bochum, scientists from the University of Basel’s Department of Physics and the Swiss Nanoscience Institute reported the findings in the journal Nature Photonics.

Microscopes allow us to see structures that are otherwise invisible to the human eye. However, conventional optical microscopes cannot be used to image...

Im Focus: Artificial agent designs quantum experiments

On the way to an intelligent laboratory, physicists from Innsbruck and Vienna present an artificial agent that autonomously designs quantum experiments. In initial experiments, the system has independently (re)discovered experimental techniques that are nowadays standard in modern quantum optical laboratories. This shows how machines could play a more creative role in research in the future.

We carry smartphones in our pockets, the streets are dotted with semi-autonomous cars, but in the research laboratory experiments are still being designed by...

Im Focus: Scientists decipher key principle behind reaction of metalloenzymes

So-called pre-distorted states accelerate photochemical reactions too

What enables electrons to be transferred swiftly, for example during photosynthesis? An interdisciplinary team of researchers has worked out the details of how...

Im Focus: The first precise measurement of a single molecule's effective charge

For the first time, scientists have precisely measured the effective electrical charge of a single molecule in solution. This fundamental insight of an SNSF Professor could also pave the way for future medical diagnostics.

Electrical charge is one of the key properties that allows molecules to interact. Life itself depends on this phenomenon: many biological processes involve...

Im Focus: Paradigm shift in Paris: Encouraging an holistic view of laser machining

At the JEC World Composite Show in Paris in March 2018, the Fraunhofer Institute for Laser Technology ILT will be focusing on the latest trends and innovations in laser machining of composites. Among other things, researchers at the booth shared with the Aachen Center for Integrative Lightweight Production (AZL) will demonstrate how lasers can be used for joining, structuring, cutting and drilling composite materials.

No other industry has attracted as much public attention to composite materials as the automotive industry, which along with the aerospace industry is a driver...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

10th International Symposium: “Advanced Battery Power – Kraftwerk Batterie” Münster, 10-11 April 2018

08.01.2018 | Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

 
Latest News

Rutgers scientists discover 'Legos of life'

23.01.2018 | Life Sciences

Seabed mining could destroy ecosystems

23.01.2018 | Earth Sciences

Transportable laser

23.01.2018 | Physics and Astronomy

VideoLinks Science & Research
Overview of more VideoLinks >>>