When the sun dips below the horizon for the night, most solar panels become interesting roofing tiles, instead of valuable generation resources.
During the day, a single cloud can quickly send residential solar power generators back to a fossil fuel-based grid for their electricity. This intermittency in fuel resource availability, combined with the current lack of economic energy storage, impedes the ability of renewable energy technologies to compete with the existing fossil-fuel fleet. This provides a great opportunity area in research and development to find innovative solutions for storing energy. And, according to MIT researchers, one path to solving this competitiveness problem might be found at the molecular level – through their new understanding of fulvalene diruthenium.
The intermittent availability of fuel resources is not just a challenge for solar power. Other renewable power generation technologies suffer from the lack of control over fuel availability. In Texas – home to the most wind capacity in the nation – sudden drops in the West Texas wind have caused multiple electric grid emergencies. While Texas grid operators have become quite adept at managing these quick changes in wind power availability, including increased amounts of wind power in the generation mix has certainly added an additional level of complexity to the process.
When generation capacity is spread over large geographic areas – and connected to the nation’s electric grid – the intermittency of fuel resource availability can become a manageable problem. It is unlikely that clouds will cover a multi-state region for long periods of time, or that the wind will simultaneously stop blowing both on- and off-shore, for example. However, when communities wish to use local distributed generation, renewable fuel resource availability can become a more significant problem.
Energy Storage – Power and Heat
Problems associated with intermittent fuel resource availability are compounded by the current state of the energy storage market. Today, there are some limited technologies available for economic large-scale energy storage in the United States. For example, in Southern California they use pumped hydro (water) storage near the I-5 “grapevine” to store electricity during off-peak periods. In McIntosh, Alabama a 110 MW natural gas power plant is equipped with Compressed Air Energy Storage (CAES) to store off-peak power. And, in thermal storage, molten salts are being used in some limited projects. On a more exploratory level, investments are being made to determine the potential of flywheel technology (and many other possibilities) for large-scale energy storage.
But, for small-scale energy storage needs, the options are not only limited – but also expensive. Battery technology has yet to find the sweet spot for energy density – energy stored per unit of volume – at an economical cost. And, thermal energy storage is still largely in the R&D phase – the Ice Bear cooling system being one of the relatively few exceptions.
- Graphite + water = the future of energy storage (electronics-lab.com)
- A123, Joule Forge Ahead in Wind Energy Storage and Biofuels (xconomy.com)
- Doubled rates of hydrogen production is an advance to energy of surplus wind and solar power (nextbigfuture.com)
- 5 Smart Grid Startups to Watch via the Cleantech Open (nytimes.com)