Clean & Clean-burn: Renewable Energy & Natural Gas powered Electricity Grids

by John Brian Shannon

Clean and Clean-Burn: Energy, the way it should be

Planetary energy graphic courtesy of Perez and Perez.
Planetary energy graphic courtesy of Perez and Perez.

Of all the energy that is available to us, solar energy is by far the most available and the most evenly distributed energy resource on planet Earth.

Wind and Solar + natural gas = Synergy

  • Solar is available all day every day. But not at night.
  • Wind is available day and night, but it can produce variable power levels as the wind blows over the landscape.
  • Meanwhile, offshore wind turbines produce constant power, spinning at constant speeds for years at a time — except when an operator locks the blades during large storms or during the annual maintenance inspection.

Both solar power and wind power face varying levels of ‘intermittency‘ — which requires the use of ‘peaking power plants‘ or ‘load-following’ power plants — to meet total demand.

‘Catch my Fall’ — All electrical power generators are interdependent

How electricity grids use different power generators to meet total and constantly changing electricity demand.

In the case of renewable energy, the negatives include some variability in the total output of solar power or wind power generation due to temporary cloud cover or storms. At such times, natural gas-fired generation can ramp-up to cover any shortfall.

Note: This is a common and daily energy grid practice whether renewable energy is involved or not. Some gas-fired power plants are called peaking power plants which quickly ramp-up to meet output shortfalls. In fact, peaking power plants (which are almost always gas-fired) were created to meet temporary shortfalls — and were in widespread use long before renewable energy ever hit the market.

Also in the case of renewable energy, another negative is that the Sun disappears at night and solar panels stop contributing to the grid. And unless you have offshore wind turbines to make up the shortfall, onshore wind turbines may fall short of total demand. So at night, you need reliable power to make up shortfalls in primary generation.

Note: This is a common and daily energy grid practice whether renewable energy is involved or not. To cover this situation load-following power plants were designed to meet larger output shortfalls. In fact, load-following power plants were created to meet larger, daily, shortfalls — and were in widespread use long before renewable energy ever hit the market.

In the case of natural gas, the negative is that gas is subject to wild price swings, thereby making gas-fired generation very expensive. Which is why it evolved into peaking power plants, less often in the load-following role and almost never as a baseload power generator.

The other negative associated with natural gas is of course, the fact that gas turbines put out plenty of CO2. That we can deal with. Unlike coal, where the CO2 portion of the airborne emissions are almost the least of our worries — as coal emissions are loaded with toxic heavy metals, soot and other airborne toxins.

How can we deal with the CO2 emitted by gas-fired power plants?

As gas-fired peaking power plants typically fire up anywhere from a couple of dozen hours annually, to a few hours of every day (usually to cover the additional load of many air conditioners suddenly switching on during hot summer days, for example) we aren’t talking about a whole lot of CO2.

Gas-fired load-following power plants typically run for a few hours every day and to cover demand in case of primary generator (like hydro-electric or nuclear power plant) maintenance. In the case of load-following plants, much more CO2 is produced annually.

Carbon Capture and Sequestration (CCS) of gas-fired CO2 emissions via tree planting

  • Peaking power plants operate for a few hours per year. We’re not talking that much CO2.
  • Load-following power plants operate for many hours per year. More CO2.

But still, each mature tree absorbs (a low average of) 1 ton of CO2 from the atmosphere and keeps it in storage for many decades. Some trees, like the ancient Sequoia trees in California, are 3700 years old and store 26 tons of CO2 each! Certain trees native to Australia store even more carbon and live longer than Sequoia trees.

And, as anyone who has worked in the forest industry knows; Once that first planting hits maturity (in about 10 years) they will begin dropping their yearly seeds. Some trees like the cottonwood tree produce 1 million seeds annually for the life of the tree. American Elm trees set 5 million seeds per year. More trees. Always good.

It’s an easy calculation: “How many tons of CO2 did ‘ABC’ gas-fired power plant output last year?”
Therefore: “How many trees do we need to plant, in order to cover those emissions?”

Simply plant a corresponding number of trees and presto! gas-fired generation is carbon neutral

By calculating how many tons each gas-fired peaking power plant contributes and planting enough trees each year to cover their CO2 contribution, tree planting could allow gas-fired power plants to become as carbon neutral as solar power or wind power.

The total number of trees that we would need to plant in order to draw gas-fired peaking power plant CO2 emissions down to zero would be a relatively small number, per local power plant.

By calculating how many tons each gas-fired load-following power plant contributes and planting enough trees annually to cover their CO2 contribution they too could become just as carbon neutral as solar panels or wind turbines. Many more trees, but still doable and a simple solution!

The total number of trees that we would need to plant in order to draw gas-fired load-following power plant CO2 emissions down to zero would be a much larger number. But not an impossible number.

So now is the time to get kids involved as part of their scholastic environmental studies, planting trees one day per month for the entire school year.

Let the gas-fired power plant operators contribute the tree seedlings as part of their media message that the local gas-fired power plant is completely carbon neutral (ta-da!) due to the combined forces of the power plant operator, the natural carbon storage attributes of trees, and students.

Up to one million trees could be planted annually if every school (all grades) in North America contributed to the effort — thereby sequestering an amount of CO2 equal to, or greater than, all gas-fired generation on the continent.

It’s so simple when you want something to work. Hallelujah!

Baseload, peaking, and load-following power plants

Historically, natural gas was too expensive to used in baseload power plants due to the wildly fluctuating natural gas pricing and high distribution costs, but it is in wide use around the world in the peaking power plant role, and less often, in the load following power plant role.

Renewable energy power plants can be linked to ‘peaking’ or ‘load-following’ natural gas-fired power plants to assure uninterrupted power flows.

Peaking power plants operate only during times of peak demand.

In countries with widespread air conditioning, demand peaks around the middle of the afternoon, so a typical peaking power plant may start up a couple of hours before this point and shut down a couple of hours after.

However, the duration of operation for peaking plants varies from a good portion of every day to a couple dozen hours per year.

Peaking power plants include hydroelectric and gas turbine power plants. Many gas turbine power plants can be fueled with natural gas or diesel. — Wikipedia

Using natural gas for baseload power

Natural gas has some strong points in its favour. Often it is the case that we can tap into existing underground gas reservoirs by simply drilling a pipe into naturally occurring caverns in the Earth which have filled with natural gas over many millions of years. In such cases, all that is required is some minor processing to remove impurities and adding some moisture and CO2 to enable safe transport (whether by pipeline, railway, or truck) to gas-fired power plants which may be located hundreds of miles away.

It is the natural gas market pricing system that prevents gas from becoming anything other than a stopgap energy generator (read: peaking or load-following) and almost never a baseload energy generator.

Let’s look at local solutions to that problem.

Waste-to-Fuels

Several corporations are working with local governments to find innovative ways to capture landfill methane gas to produce electricity from it.

Keep in mind that the methane gas that escapes from every single landfill in the world (whether still operating or having ceased operations long ago) is 23 times more damaging to the atmosphere than CO2.

Increasingly, landfills are now installing perforated pipes underground which draw the landfill gas (so-called ‘swamp methane’) to an on-site processing facility. It is a low-grade gas which is sometimes blended with conventional natural gas to create an effective transportation or power generation fuel. Visit the Caterpillar Gas Power Solutions website here.

Waste Management is a global leader in the implementation of this technology, using its own landfills and municipal landfills across North America to produce over 550 megawatts of electricity, which is enough to power more than 440,000 homes. This amount of energy is equivalent to offsetting over 2.2 million tons of coal per year. Many more similar operations are under construction as you read this. Read the Waste Management landfill bioreactor brochure (downloadable PDF) here.

Durban, South Africa, a city of 3.5 million people, has created a huge Waste-to-Fuel landfill power plant that provides electricity to more than 5000 nearby homes.

Durban Solid Waste receives 4000 tons of trash each weekday which produces some 2600 cubic metres of gas every day of the year.

The GE Clean Cycle Waste-to-Fuel power plant arrives in 4 large shipping containers, and once connected to the gas supply pipeline it is ready to power nearby buildings and to sell surplus power to the grid.

One GE Clean Cycle Waste-to-Fuel power plant unit can generate 1 million kWh per year from waste heat and avoid more than 350 metric tons of CO2 per year, equivalent to the emissions of almost 200 cars.

Blending Conventional Natural Gas with Landfill Gas

As conventional natural gas is expensive (and much of the cost is associated with transportation of the gas over long distances) when we blend it 50/50 with landfill gas, we drop the cost of the gas by half. Thereby making blended natural gas (from two very different sources) more competitive as a power generation fuel.

By blending conventional natural gas 50/50 with landfill gas; We could produce baseload power with it — but more likely than that, we could use it to produce reasonably-priced load-following or peaking power to augment existing and future renewable energy power plants — rather than allow all that raw methane from landfills to escape into the atmosphere.

Best of Both Worlds — Renewable Energy and Natural Gas

Partnering renewable energy with natural gas in this way allows each type of power generator to work to their best strength — while countering negatives associated with either renewable energy or natural gas.

Renewable power generation and lower cost natural gas can work together to make coal-fired electrical power generation obsolete and accelerate progress toward our clean air goals.

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NREL Says Wind Energy Boosts Grid Reliability

by Silvio Marcacci

We’ve all heard the warnings about how intermittent renewables could “crash” the grid if for instance all of a sudden the wind stops blowing and grid operators are left in the lurch for power when they need it. But what if wind turbines actually improve grid reliability?

May sound far-fetched to some people, but that’s exactly what the U.S. Department of Energy’s National Renewable Energy Laboratory (NREL) reports in the new study Active Power Controls from Wind Power: Bridging the Gaps.

Previous studies have focused on wind energy forecasting as the key to balancing wind’s availability and the power grid’s demand, but this new hypothesis could vastly expand the relationship between wind turbines and the grid.

Wind farm in the snow. Image via CleanTechnica
The U.S. Department of Energy, National Renewable Energy Laboratory (NREL) says that wind power helps grid stability. Netherlans wind farm in the snow image via CleanTechnica. Image by T.W. van Urk on Shutterstock.
How Does Wind Perform With The Grid?

NREL undertook the study with the Electric Power Research Institute, an organization comprised of more than 1,000 members (most of whom are electric utilities) and the University of Colorado, so renewable energy naysayers will be hard pressed to dismiss this study as an environmentalist pipe dream.

Analysts studied multiple power system simulations, control simulations, and field tests at NREL’s National Wind Technology Center to determine how if wind could provide ancillary services in wholesale electricity markets, how wind farms affect system frequency in the Western U.S. grid system, and if using wind farms to actively provide power control to the grid affects turbine performance and structural integrity.

And the outcome of all these studies? Wind energy can not only support the grid by ramping power output up and down to enhance system reliability, but that using wind farms to provide active power control is economically beneficial, all with negligible damage to the turbines themselves.

Wind Energy, Making The Grid Stronger and Cheaper

These are potentially game-changing findings. “The study’s key takeaway is that wind energy can act in an equal or superior manner to conventional generation when providing active power control, supporting the system frequency response, and improving reliability,” said Erik Ela, NREL analyst.

Active power control helps grid operators balance system demand with generation at various times throughout the day, helping prevent power flow above or below the ideal grid frequency and involuntary load shedding – preventing both potential blackouts and turbine damage.

Making America’s grid more flexible and integrating renewables is an important imperative. Without long-overdue transmission system investments, grid operators are often forced to use high-cost (and typically fossil fuel) “peaker” power plants when demand surges or baseload power plants go offline.

Intermittency Mitigated By Recent Developments

The traditional issue facing wind energy in this context is that it can’t be “turned on” by grid operators whenever they need it. Unless the wind is blowing, turbines can’t generate electricity.

But wind has shown its chops in helping keep the lights on as extreme weather has hit the U.S. in recent memory – just consider the fact that wind energy was credited with preventing blackouts in Texas and parts of the Midwest when the polar vortex spiked power demand and forced some power plants offline.

NREL’s report also notes that almost all grid operators across the U.S., as well as many power systems outside the areas covered by regional grids, are using wind farms in dispatch procedures to manage transmission congestion at five-minute intervals – meaning it’s now a generation resource to be dispatched (for free) when needed.

“Utilities and independent system operators are all seeking strategies to better integrate wind and other variable generation into their electric systems,” said Ela. “Few have considered using wind power to support power system reliability.”

Wind energy has become one of the fastest-growing sources of electricity in America, and it’s a critical source of generation if we’re going to decarbonize our economy and slow climate change. With NREL’s report, perhaps grid operators will start to see wind energy as an energy system imperative, not just an environmental imperative.

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This article, Forget Intermittency: NREL Says Wind Energy Can Boost Grid Reliability, is syndicated from Clean Technica and is posted here with permission.

About the Author

Silvio Marcacci Silvio Marcacci Silvio is Principal at Marcacci Communications, a full-service clean energy and climate-focused public relations company based in Washington, D.C.