Natural Gas has an Imperative Role in the Ever Increasing Era of Solar and Wind Renewable Power Generation Resources

U.S. energy demand is forecast to increase by 27% between now and 2050.  All energy resources are needed to meet that demand, and renewables are a welcome resource to help meet that demand requirement.  Over the past decade, renewable energy sources like solar and wind have seen dramatic growth around the world. Major investments in solar panel and wind turbine installations have led to an exponential increase in renewable power generation capacity. In 2021 alone, over 280 gigawatts (GW) of renewable energy capacity was added globally, and is projected in the near term (by IEA) through 2026 to account for over 95% of all new power generation added. As of 2022, total global renewable power generation stands at 3,026 GW, in comparison to total global power generation of all types of 8,013 GW.

However, as renewables start providing an increasing share of total electricity generation in many regions, the inherent variability and intermittency of renewables poses new challenges for power system planning and operations. Solar and wind generation depends on weather and environmental conditions, which leads to fluctuations in output on hourly, daily and seasonal timescales. For instance, solar power drops off at night, while wind speeds are slower during the daylight hours, and also in summer months. This intermittency requires the grid to have sufficient power generation backup of other sources of energy, as well as storage solutions, to maintain round-the-clock reliability, and meet demand for power as that demand occurs.

The intermittency and variability of renewables requires a flexible grid with sufficient dispatchable generation capacity that can be ramped up or down quickly based on fluctuations in renewable output. Natural gas-fired power plants, with their rapid load-following abilities, low capital costs, abundant -natural gas resource supplies are an ideal complement to address renewable energy’s challenges. The natural gas pipeline infrastructure exists today, and is easily expanded. It is the natural gas infrastructure and fuel resource that is allowing renewables to rapidly expand, providing the grid with a stable reliable fuel resource to meet the electricity market demand.

In this article, we will explore the economic and environmental considerations of using natural gas as a complementary source of energy, its role in future-proofing the energy grid, and how it fits into the evolving landscape of energy policy and market trends.

Understanding Renewable Energy Intermittency

The Nature of Solar and Wind Power Generation

Solar and wind power have unique generation characteristics that lead to intermittency issues. Solar photovoltaic (PV) panels produce electricity only during daylight hours, with generation peaking around noon and falling off by early evening. Solar output also varies due to cloud cover, weather patterns, precipitation, snow accumulation, and seasonal changes in the sun’s position.

Wind turbines generate power when wind speeds are within their operational range. Wind speeds fluctuate minute to minute due to wind gusts, daily due to atmospheric pressure changes, and seasonally due to global wind patterns shifting. Locations with steady wind patterns see less hourly volatility but still have seasonal variability.

These variable and partially unpredictable generation profiles create complications for grid management. Solar and wind farms cannot be directly controlled or dispatched like traditional power plants. Instead, their output levels are dictated by the environmental conditions previously mentioned. This requires grid operators to forecast renewable generation and continuously balance power supply that meets variable power demand needs that also vary throughout the day and seasonally, through other power generation assets.

Impacts of Intermittency on Grid Stability

Due to the aforementioned variable nature of wind and solar resources, large swings in renewable power output can threaten short-term grid stability, and fall short of required power demand. Sudden drops in solar or wind generation lead to supply deficits that must be addressed within seconds to minutes to avoid grid failures. Likewise, surges in renewable output can also overload transmission lines and destabilize grid voltage and frequency.

As a result of the reliability component of renewable energy sources, grid operators must have in place sufficient “base” power generation, which includes efficient natural gas combined cycle gas turbine generation facilities (CCGT’s), nuclear, and hydroelectric power sources. This base power generation is a critical part of any stable and durable electric grid system. 

In addition to addressing the reliability component of renewables, the intermittency and variability component of renewables must also be addressed by grid operators.  To address this, quick-starting gas combustion turbines (GT’s), or “peaker plants”, are required, as well as nearby associated natural gas storage facilities, that can react within 10 to 15 minutes to compensate for renewable variability. Without these fast-responding power generation reserves, frequency and voltage fluctuations from intermittent renewables can trigger widespread outages and cascading faults.  

Detailed further, inertia, energy stored in large rotating generators which gives them the tendency to remain rotating, is essential for grid reliability.  Wind and solar generation do not provide inertia, so increasing those resources necessarily requires conventional generating facilities such as CCGTs to provide the system inertia, which compensates for fluctuations in intermittent resources and ensures grid stability.

In some cases, curtailing renewable generation may be necessary to maintain system balance. But curtailment may be an inefficient solution. Building adequate flexible generation capacity is a smarter long-term strategy for grid stability as renewables reach higher penetration levels.

The Role of Natural Gas in Modern Energy Infrastructure

Balancing the Grid: Natural Gas as a Reliable and Flexible Resource 

GT’s can ramp electricity production up and down quickly and at a lower capital cost, making them an ideal technology to balance the shorter term variability and intermittency of renewable resources. CCGTs start up more slowly, but are very efficient and more capital intensive, and are more suitable for base generation to address the reliability (as well as variability) of renewable resources.  

This load-following flexibility allows different types of natural gas plant technologies to fill short-term supply deficits, or alternatively long-term supply deficits, as well as meeting shorter term or longer term demand fluctuations, in the most efficient manner for the grid operator. Grid operators can dispatch natural gas generation with advanced notice to meet foreseeable ramps in demand and/or renewable downturns. Peaker plants can also quickly throttle down when renewable production spikes during windy or sunny periods. This ensures grid stability and avoids curtailing surplus renewable power. Furthermore, natural gas generators provide essential grid services like frequency regulation, voltage support, and operating reserves to counterbalance renewable intermittency. 

Economic and Environmental Considerations

Cost-Effectiveness of Natural Gas for Grid Support

Natural gas offers an affordable way to provide grid flexibility compared to alternatives. Gas turbine plants are relatively inexpensive to construct, with capital costs as low as $700 per kW. Operating costs for natural gas plants are also competitive. Pumped hydro storage is generally only available in some geographic areas. And, renewables coupled with battery storage struggles to provide sustained backup for long-duration power demand spikes or power generation shortfalls.  

Natural gas capacity can be built faster than most alternatives too. Gas plants can start delivering grid services in just one to two years after approvals, versus three to five years for new pumped hydro plants. This enables planners to rapidly deploy gas capacity, along with new renewable projects.

Overall, natural gas power generation, and the required natural gas infrastructure of pipelines and storage, provides vital and cost-effective long-term and short-term grid stability that occurs with increasing renewable power generation penetration, integrating new projects seamlessly.

Environmental Impact of Using Natural Gas as a Complementary Source

While natural gas is a fossil fuel, it burns much cleaner than coal and oil, emitting 50-60% less CO2 when used for power generation. New high-efficiency gas turbines can minimize CO2 emissions to around 800 lbs/MWh, while a coal plant will have CO2 emissions around 2,000 lbs/MWh. 

As we’ve discussed here, as renewable penetration increases, natural gas generation, natural gas pipelines, and gas storage infrastructure also correspondingly is required to increase.  From an environmental perspective, natural gas complements renewables without markedly increasing electric sector emissions.  In fact, a recent EIA study projects that GDP will grow 2.4% in 2023, but carbon emissions are projected to drop by 3%, driven by replacing coal generation with gas generation.  With gas also displacing far more carbon-intensive coal generation, total grid emissions intensity keeps declining as renewables expand.  Meanwhile, innovations like renewable natural gas, hydrogen blending, and carbon capture can further reduce the environmental footprint of natural gas power generation.

Technological Innovations to Enhance Natural Gas Efficiency

Renewable technologies do offer hope in addressing the intermittency concerns in the coming decades, enabling renewable generation resources to continue to grow and be an important part of the generation resources. Natural gas power generation facilities are also incorporating advanced technologies like, that ensures natural gas can play its role in the development of renewables and grid reliability:

• Combined heat and power (CHP) to utilize waste heat for efficiency
• Advanced sensors and control systems to forecast and manage gas demand patterns in real-time
• Hybrid designs integrating battery storage to optimize flexibility
• Microgrids with on-site gas generation to strengthen resiliency
• Hydrogen-ready turbines are increasingly able to accept hydrogen/renewable gas blends over time
• Carbon capture projects to create near zero-emission gas plants

These innovations are further maximizing the efficiency and flexibility of the natural gas power generation value chain, while further minimizing the environmental impact of natural gas power generation. 

The Evolving Landscape of Energy Policy and Market Trends

Energy policies, carbon pricing mechanisms, clean energy mandates, and wholesale power market reforms will incentivize renewable growth, while still requiring increasing natural gas generation for reliability, flexibility, peaking services, and needed base generation. RTOs/ISOs are designing new ancillary service products and capacity markets to specifically compensate gas facilities. Policymakers recognize gas infrastructure enables renewable expansion near-term while maintaining affordability.

Corporate renewable energy procurement and utility clean energy standards ensure steady renewable energy additions. However, these are balanced with reliability safeguards and consideration for system costs – requiring a key role for natural gas. While the energy mix evolves, delivering electricity affordably and reliably remains an absolute requirement. Natural gas provides crucial insurance to achieve broad renewables adoption without cost and reliability consequences.

Frequently Asked Questions

1. What are the main drivers for converting coal power plants to natural gas?

The primary drivers for converting coal power plants to natural gas include environmental concerns, economic factors, and regulatory pressures. Natural gas burns cleaner than coal, producing fewer pollutants and greenhouse gases, which makes it an environmentally friendlier option for base generation needs. Economically, natural gas plants often have lower operational costs and are more efficient. Additionally, stricter environmental regulations and policies aimed at reducing carbon emissions and eliminating coal ash ponds are pushing the shift from coal to natural gas.

2. How does natural gas conversion reduce a power plant’s carbon footprint?

Converting a power plant from coal to natural gas significantly reduces its carbon footprint. Natural gas combustion emits about 50-60% less carbon dioxide compared to coal for the same amount of energy produced. Additionally, natural gas plants emit fewer pollutants like sulfur dioxide and particulate matter. Combined cycle gas power plants also enhance efficiency by using the heat generated from natural gas combustion to fuel a heat recovery steam generator (HRSG), increasing efficiency by generating incremental energy from the same amount of natural gas consumed.  This cleaner combustion process makes natural gas a more environmentally friendly option and helps in mitigating climate change impacts.

3. What are some of the success stories in coal to gas power plant conversions?

Around the world, there are numerous success stories of coal to gas power plant conversions. For instance, in the United States, utilities like Duke Energy and Southern Company have made significant strides in converting their coal plants to natural gas, resulting in reduced emissions and improved efficiency. Similarly, in Europe and Asia, several countries are transitioning from coal to natural gas as part of their energy policies, demonstrating both environmental and economic benefits.

4. How does natural gas fit into the future of renewable energy?

Natural gas is viewed as a critical, reliable, bridge fuel, enabling the transition to an increasingly renewable energy future. Its ability to provide flexible and reliable power makes it an ideal complement to intermittent renewable sources like solar and wind. As renewable technologies advance and become more widespread, natural gas helps maintain grid stability by providing voltage support that renewables currently are not capable of and meeting energy demands when renewable sources are not available. Over time, its role may evolve to support renewable energy more directly, possibly transitioning towards renewable gas options such as biogas and hydrogen.  Natural gas is an important part of our clean energy economy now and into the future.