Worldwatch Report #184: Powering the Low-Carbon Economy: The Once and Future Roles of Renewable Energy and Natural Gas
|Download the full report:||Size:|
|Worldwatch Report #184: Powering the Low-Carbon Economy: The Once and Future Roles of Renewable Energy and Natural Gas||1.46MB|
Author: Saya Kitasei
Publication Date: Dec. 2010
Over the past decade, renewable energy and natural gas have emerged as potential cornerstones of a low-carbon power sector. Wind and solar resources are abundant and can be converted into electricity using technologies that emit no greenhouse gases. Natural gas offers a cleaner alternative to coal that can deliver sharp, immediate reductions in carbon dioxide emissions from the power sector—if new supplies can be produced responsibly.
Important synergies between renewable energy and natural gas will allow for reduced dependence on coal, speeding the transition to a low-carbon economy. These synergies emerge when the power system is considered holistically, rather than with the one-solution-for-one-problem approach that electricity system operators have employed historically.
Natural gas can be used in a range of efficient, flexible, and scalable generating technologies, making it a natural partner for variable renewable energy sources such as wind and solar power. Because these renewable resources vary by the season, day, and even hour, wind and solar power plants cannot always generate electricity when it is needed, as other types of power plants can. Meanwhile, the coal and nuclear steam turbines that form the backbone of most electricity systems today are very slow to turn up and down and become much less efficient when they are running at less than full power. The inflexibility of these plants limits the amount of variable generation that the electricity grid can absorb.
Thanks to growing policy support for renewable energy, the costs of many renewables are falling, and renewable energy has started to penetrate power markets in a significant way. In 2008, the share of the world’s electricity generated from wind and solar power surpassed 1 percent, more than double the contribution in 2004. In some countries and regions, the share is considerably higher: several states in northern Germany now generate more than 30 percent of their electricity from wind energy alone, and two U.S. states generate more than 8 percent. In Denmark, wind power represents about 20 percent of total generation.
Yet the world could be generating much more renewable power than it is. The global installed capacity of wind and solar power is now growing by 30–50 percent per year. But electricity systems with growing shares of variable generation are sometimes unable to accommodate all of the power that is available, especially at times when demand is low. Although some regions are able to store limited amounts of excess electricity for later use or to share the power with neighboring regions, many system operators are forced to “curtail” or turn down wind and solar generators in such situations. Natural gas power plants can increase the grid’s flexibility as a whole and provide dedicated backup generation to individual wind and solar plants.
Renewable energy and natural gas can also power a transition away from inefficient centralized power. Natural gas power plants come in a range of scales, allowing them to generate electricity in both centralized and distributed power systems. Distributed power, produced from small generators located near electricity consumers, can reduce the expense and efficiency losses associated with long-distance transmission. Small solar, wind, and natural gas-fired cogeneration plants (also known as combined heat and power, or CHP, plants) can be integrated directly into distribution lines and networked together to create a diffuse, flexible, local, and low-carbon grid.
In order to play a sustainable role in a low-carbon future, natural gas itself can and must decarbonize. At the chemical level, natural gas consists primarily of methane, a molecule that can be produced or synthesized from a variety of renewable sources. Landfills and organic processes can create methane that otherwise enters the atmosphere, where it acts as a greenhouse gas some 25 times more potent than carbon dioxide. This methane or “biogas” can be used interchangeably with natural gas, and capturing and utilizing it can mitigate greenhouse gas emissions. In the future, methane supplies could be decarbonized further by blending in hydrogen gas, a zerocarbon fuel that can be produced from water through electrolysis using renewable energy.
Four key mechanisms can enable the combination of renewable energy and natural gas to displace coal and provide needed reductions in power-sector emissions. First, air pollutants such as nitrogen oxide, sulfur dioxide, and mercury must be tightly regulated. Second, a cost must be attached to emitting carbon dioxide. Third, electricity system operators should allow wind and solar plants to balance their own output with on-site resources. And finally, the markets on which system operators purchase electricity must be highly responsive, allowing them to react to fluctuations in electricity supply and demand as rapidly as possible. Working together, renewable energy and natural gas can accelerate the decarbonization of the world’s electricity system and form the foundation of tomorrow’s low-carbon economy.