In this article from seekingalpha.com (intended for a U.S. audience), John Petersen gives fascinating analysis of the economics of storage — specifically, at what point storage becomes cost-effective.

Today, most power companies deal with highs and lows in the daily cycle of demand by simply having excess fossil fuel burning generating capacity sitting around idle, only to be fired up in peak demand moments. Maintaining that excess capacity at the ready costs money, and a certain amount of generated power simply not being used at all is also tolerable under current conditions.

“As long as waste is cheaper than storage, waste rules” Petersen writes, adding:

When you start layering in additional storage that will be needed to compensate for inherent variability in solar and wind alternatives, the demand for $1,000 per kW storage systems skyrockets.

When electric utilities were looking for a $700 per kW solution and storage technologies were less developed, there was no market. As the breakeven cost of storage increases; storage technologies improve and the installed cost of storage systems decline, historical revenues in the $20 billion domestic energy storage industry are likely to increase at staggering rates and nimble manufacturers of low-cost storage systems are likely to profit handsomely.

Continuing on the theme of “lesser-known bricks” of sustainable energy systems … let’s move from smart power grids to another essential: grid energy storage. It’s an increasingly hot topic, because some of the key renewable generation technologies that the world needs to build up, such as solar and wind power, are intermittent in nature — they need the grid to absorb and store their output, evening out gaps in the supply to satisfy a 24-7 demand pattern.

What are the best approaches for future sustainable systems? The first thing that comes to mind — batteries — aren’t necessarily well adapted for massive-scale central grid requirements, although some green advocates are calling for prioritization of R&D to improve battery technology, in the context of electric vehicles and home use.

The following wiki article lays out the main storage techniques that are possible, but each has strengths and weaknesses across the following:

- capital requirements (up-front cost)
- operating costs
- energy efficiency (what % of the kW put in do you get out?)
- capacity (scale)
- delivery time (responds in seconds, minutes or hours?)
- local geography

Take pumped storage hydroelectricity for example, a widely used technique based on a principle as low-tech as gravity: When there’s excess power onhand, use it to pump water uphill into an elevated reservoir — then tap it later by releasing downhill flows back through the turbines. The method boasts reasonable efficiency (75-80%), very high capacity and rapid delivery time. The drawbacks: Suitable geography is scarce, minimum scale quite high (not something you could use to manage the output of a solar array on your roof), and capital requirements are very high.

Upcoming posts will explore what options are generally in use in China and India today … and which are best-adapted for greening their energy systems.

(Image of Vanadium Redox battery courtesy of www.treehugger.com)