The energy storage market is like a charging elephant: even if you can’t see what it looks like, you know it’s going to be big.

As energy shifts to become more distributed and with a greater emphasis on intermittent renewable resources, the need for temporary storage will expand significantly. Distributed storage increases energy efficiency by eliminating transmission losses, and wind and solar power require temporary storage to counteract the daily peaks and valleys in demand.

Entrepreneurs and researchers sensing the opportunity have been developing a wide variety of technologies to meet the expected surge in demand. Just like an elephant, which takes a relatively long time to gestate (22 months) the storage market has taken time to develop, but once it starts, it will keep growing and growing. According to Pike Research’s recent report “Energy Storage Technology Markets,” the market for stationary utility energy storage will grow by more than 10 fold between 2008 and 2018, to $4.1 billion.

Jim Woolsey, the former CIA director and current partner at Vantage Point Venture Partners, is one of the most vocal proponents of storage systems for renewable energy and will be speaking on the subject this week at Storage Week, which Pike Research will also be attending.

The wide-open field includes batteries, which are being adapted to be part of large energy storage systems, as well as compressed air, pumped hydro power, flywheel and supercapacitor systems.

Beacon Power just received a $43 million loan from the Department of Energy to continue work on a 20 megawatt flywheel storage system. Competing flywheel storage company, Pentadyne Power Corporation is expanding operations, raising $22 million last year, and making lists from Inc magazine and the Los Angeles Business Journal of fastest growing companies.

General Electric is taking another approach, betting that sodium batteries can play a role in energy storage. The company is partnering with New York to build a $100 million battery manufacturing facility.

While an open field encourages innovation, it complicates the task of grid operators on setting standards for adoption. According to the DOE’s National Council on Electricity Policy, no cohesive plan exists as to how storage technologies will be incorporated into the grid.

These technical issues will be sorted out over the next few years as the shakeout occurs and dominant and niche players are identified. Battery technologies may have an advantage as they are receiving the most investment because of their use in electric vehicles.