Wind and solar are too intermittent to comprise much of electric grid power now, according to Steven Chu, former US energy secretary.  In 2010, Chu said, “Without technological breakthroughs in efficient, large-scale energy storage, it will be difficult to rely on intermittent renewables for much more than 20-30% of electricity.”

Unless a major breakthrough in batteries happens, we will continue to require natural gas fueled power plants to ramp up and down quickly to cope with intermittent sources of power.  “When you ramp power plants up and down they lose efficiency” according to Haresh Kamath of the Electric Power Research Institute in Washington DC.

Some batteries cannot survive deep discharge cycles

An inability to withstand deep discharge cycles means, in effect, that additional capacity needs to be installed in order to provide effective capacity. Thus, if a technology were deployed that were limited to 50 percent discharge, it would be necessary to provide twice the capacity of a technology of one that had no such limit. Thus, a storage system with a 50 percent limit would in effect need 12,000 MWh of storage where the study had determined that a 3,000 MW, 2-hour unit was required (CEC).

And keep in mind, for the long run, these batteries need to have a positive EROEI over their entire life cycle from mining and crushing of rocks for metals to fabrication to delivery.  If they require more energy to construct across the life cycle than they more energy to create than at least 5 times the energy stored and discharged, our way of life can’t continue.

In addition, batteries must be composed of cheap and abundant materials.  Platinum, lithium, and many other metals are scarce and take too much energy to extract.

Without energy storage, conventional power generation plants are harmed

Without the use of storage, ramping of combustion turbine generators and hydro?electric generation is likely to increase. This may likely have detrimental effects on equipment maintenance costs and life of the equipment, and greenhouse gas emissions because the resources will be asked to generate more often at less than optimal production ranges as well as to remain committed-that is, on?line-in anticipation of ramping needs The 3,000 to 4,000 MW of storage which could be used to address renewables management requires a ramp rate capacity of 5 to 10 MW/second, or 0 to full power charging / discharging in 5 minutes. This equals or exceeds the ramping capabilities of most conventional generating units, and particularly the larger combustion turbines. Smaller combustion turbines in the California ISO database can meet this ramp rate requirement, but there are insufficient quantities of such units to provide the required 3,000 to 4,000 MW of fast ramping (CEC).

Concentrating Solar Power (CSP) storage

Existing molten salt thermal storage is both expensive and operationally challenging. New technologies are needed now before the large solar plants are all designed and built.

References

CEC. June 2010. Research evaluation of wind generation, solar generation, and storage impact on the California Grid. Prepared by KEMA, Inc for the California Energy Commission.

Hal Hodson. 2 Feb 2013. Greening the Grid. NewScientist.