May 17, 2020

U.S. power plant emissions down

Admin
4 min
Denver coal-fired plant
[email protected] Make sure to check out the latest issue of Energy Digital magazine Power plants that use natural gas and a new technology to squee...

Make sure to check out the latest issue of Energy Digital magazine 

Power plants that use natural gas and a new technology to squeeze more energy from the fuel release far less of the greenhouse gas carbon dioxide than coal-fired power plants do, according to a new analysis accepted for publication Jan. 8 in the journal Earth’s Future, a journal of the American Geophysical Union. The so-called “combined cycle” natural gas power plants also release significantly less nitrogen oxides and sulfur dioxide, which can worsen air quality.

“Since more and more of our electricity is coming from these cleaner power plants, emissions from the power sector are lower by 20, 30, even 40 percent for some gases, since 1997,” said lead author Joost de Gouw, an atmospheric scientist with NOAA’s Cooperative Institute for Research in Environmental Sciences (CIRES) at the University of Colorado Boulder.

De Gouw, who works at NOAA’s Earth System Research Laboratory (ESRL), and his NOAA and CIRES colleagues analyzed data from systems that continuously monitor emissions at power plant stacks around the country. Previous aircraft-based studies have shown these stack measurements are accurate for carbon dioxide CO2 and for nitrogen oxides and sulfur dioxide. Nitrogen oxides and sulfur dioxide can react in the atmosphere to form tiny particles and ozone, which can cause respiratory disease.

To compare pollutant emissions from different types of power plants, the scientists calculated emissions per unit of energy produced, for all data available between 1997 and 2012. During that period of time, on average:

Coal-based power plants emitted 915 grams (32 ounces) of CO2 per kilowatt hour of energy produced; Natural gas power plants emitted 549 grams (19 ounces) CO2 per kilowatt hour; and Combined cycle natural gas plants emitted 436 grams (15 ounces) CO2 per kilowatt hour.

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In combined cycle natural gas plants, operators use two heat engines in tandem to convert a higher fraction of heat into electrical energy. For context, U.S. households consumed 11,280 kilowatt hours of energy, on average, in 2011, according to the U.S. Energy Information Agency. This amounts to 11.4 metric tons per year of CO2 per household, if all of that electricity were generated by a coal power plant, or 5.4 metric tons if it all came from a natural gas power plant with combined cycle technology.

The researchers reported that between 1997 and 2012, the fraction of electric energy in the United States produced from coal gradually decreased from 83 percent to 59, and the fraction of energy from combined cycle natural gas plants rose from none to 34 percent.

That shift in the energy industry meant that power plants, overall, sent 23 percent less CO2 into the atmosphere last year than they would have, had coal been providing about the same fraction of electric power as in 1997, de Gouw said. The switch led to even greater reductions in the power sector’s emissions of nitrogen oxides and sulfur dioxide, which dropped by 40 percent and 44 percent, respectively.

The new findings are consistent with recent reports from the Energy Information Agency that substituting natural gas for coal in power generation helped lower power-related carbon dioxide emissions in 2012.

The authors noted that the new analysis is limited to pollutants emitted during energy production and measured at stacks. The paper did not address levels of greenhouse gases and other pollutants that leak into the atmosphere during fuel extraction, for example. To investigate the total atmospheric consequences of shifting energy use, scientists need to continue collecting data from all aspects of energy exploration, production and use, the authors concluded.

Authors of the new paper, “Reduced Emissions of CO2, NOx and SO2 from U.S. Power Plants Due to the Switch from Coal to Natural Gas with Combined Cycle Technology,” are Joost de Gouw (CIRES), David Parrish (NOAA ESRL), Greg Frost (CIRES) and Michael Trainer (NOAA).

CIRES is a joint institute of the National Oceanic and Atmospheric Administration (NOAA) and the University of Colorado Boulder.

Photo by Will von Dauster, NOAA

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Jun 12, 2021

Why Transmission & Distribution Utilities Need Digital Twins

digitaltwins
Technology
Utilities
Management
Petri Rauhakallio
6 min
Petri Rauhakallio at Sharper Shape outlines the Digital Twins benefits for energy transmission and distribution utilities

As with any new technology, Digital twins can create as many questions as answers. There can be a natural resistance, especially among senior utility executives who are used to the old ways and need a compelling case to invest in new ones. 

So is digital twin just a fancy name for modelling? And why do many senior leaders and engineers at power transmission & distribution (T&D) companies have a gnawing feeling they should have one? Ultimately it comes down to one key question: is this a trend worth our time and money?

The short answer is yes, if approached intelligently and accounting for utilities’ specific needs. This is no case of runaway hype or an overwrought name for an underwhelming development – digital twin technology can be genuinely transformational if done right. So here are six reasons why in five years no T&D utility will want to be without a digital twin. 

1. Smarter Asset Planning

A digital twin is a real-time digital counterpart of a utility’s real-world grid. A proper digital twin – and not just a static 3D model of some adjacent assets – represents the grid in as much detail as possible, is updated in real-time and can be used to model ‘what if’ scenarios to gauge the effects in real life. It is the repository in which to collect and index all network data, from images, to 3D pointclouds, to past reports and analyses.

With that in mind, an obvious use-case for a digital twin is planning upgrades and expansions. For example, if a developer wants to connect a major solar generation asset, what effect might that have on the grid assets, and will they need upgrading or reinforcement? A seasoned engineer can offer an educated prediction if they are familiar with the local assets, their age and their condition – but with a digital twin they can simply model the scenario on the digital twin and find out.

The decision is more likely to be the right one, the utility is less likely to be blindsided by unforeseen complications, and less time and money need be spent visiting the site and validating information.

As the energy transition accelerates, both transmission and distribution (T&D) utilities will receive more connection requests for anything from solar parks to electric vehicle charging infrastructure, to heat pumps and batteries – and all this on top of normal grid upgrade programs. A well-constructed digital twin may come to be an essential tool to keep up with the pace of change.

2. Improved Inspection and Maintenance

Utilities spend enormous amounts of time and money on asset inspection and maintenance – they have to in order to meet their operational and safety responsibilities. In order to make the task more manageable, most utilities try to prioritise the most critical or fragile parts of the network for inspection, based on past inspection data and engineers’ experience. Many are investigating how to better collect, store and analyze data in order to hone this process, with the ultimate goal of predicting where inspections and maintenance are going to be needed before problems arise.  

The digital twin is the platform that contextualises this information. Data is tagged to assets in the model, analytics and AI algorithms are applied and suggested interventions are automatically flagged to the human user, who can understand what and where the problem is thanks to the twin. As new data is collected over time, the process only becomes more effective.

3. More Efficient Vegetation Management

Utilities – especially transmission utilities in areas of high wildfire-risk – are in a constant struggle with nature to keep vegetation in-check that surrounds power lines and other assets. Failure risks outages, damage to assets and even a fire threat. A comprehensive digital twin won’t just incorporate the grid assets – a network of powerlines and pylons isolated on an otherwise blank screen – but the immediate surroundings too. This means local houses, roads, waterways and trees. 

If the twin is enriched with vegetation data on factors such as the species, growth rate and health of a tree, then the utility can use it to assess the risk from any given twig or branch neighbouring one of its assets, and prioritise and dispatch vegetation management crews accordingly. 

And with expansion planning, inspection and maintenance, the value here is less labor-intensive and more cost-effective decision making and planning – essential in an industry of tight margins and constrained resources. What’s more, the value only rises over time as feedback allows the utility to finesse the program.

4. Automated powerline inspection

Remember though, that to be maximally useful, a digital twin must be kept up to date. A larger utility might blanche at the resources required to not just to map and inspect the network once in order to build the twin, but update that twin at regular intervals.

However, digital twins are also an enabling technology for another technological step-change – automated powerline inspection.

Imagine a fleet of sensor-equipped drones empowered to fly the lines almost constantly, returning (automatically) only to recharge their batteries. Not only would such a set-up be far cheaper to operate than a comparable fleet of human inspectors, it could provide far more detail at far more regular intervals, facilitating all the above benefits of better planning, inspection, maintenance and vegetation management. Human inspectors could be reserved for non-routine interventions that really require their hard-earned expertise.

In this scenario, the digital twin provides he ‘map’ by which the drone can plan a route and navigate itself, in conjunction with its sensors. 

5. Improved Emergency Modelling and Faster Response

If the worst happens and emergency strikes, such as a wildfire or natural disaster, digital twins can again prove invaluable. The intricate, detailed understanding of the grid, assets and its surroundings that a digital twin gives is an element of order in a chaotic situation, and can guide the utility and emergency services alike in mounting an informed response.

And once again, the digital twin’s facility for ‘what-if’ scenario testing is especially useful for emergency preparedness. If a hurricane strikes at point X, what will be the effect on assets at point Y? If a downed pylon sparks a fire at point A, what residences are nearby and what does an evacuation plan look like?

6. Easier accommodation of external stakeholders

Finally, a digital twin can make lighter work of engaging with external stakeholders. The world doesn’t stand still, and a once blissfully-isolated powerline may suddenly find itself adjacent to a building site for a new building or road. 

As well as planning for connection (see point 1), a digital twin takes the pain out of those processes that require interfacing with external stakeholders, such as maintenance contractors, arborists, trimming crews or local government agencies – the digital twin breaks down the silos between these groups and allows them to work from a single version of the truth – in future it could even be used as part of the bid process for contractors.

These six reasons for why digital twins will be indispensable to power T&D utilities are only the tip of the iceberg; the possibilities are endless given the constant advancement of data collection an analysis technology. No doubt these will invite even more questions – and we relish the challenge of answering them. 

 

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