Cost Considerations

Technology Description

Normalized system cost ($/kWh) is one of the most important factors for stationary applications. System cost depends on many factors and includes all anicallary equipment necessary for the full storage system. While capital cost is important, total ownership cost (including O&M costs) is a much more meaningful index for a complete economic analysis. The concept of ‘present worth’ is used to express this total ownership cost in the graph below. A thorough discussion of the concept is provided in Benefit/Cost Framework for Evaluating Modular Energy Storage (SAND2008-0978); the information here has been updated to reflect the latest available information from various sources. In general, present worth is based on ownership of the device over 10 years and includes the following factors (as applicable)—

• Application,
• Efficiency,
• Cycle life,
• Initial capital costs,
• Operations and maintenance (O&M), and
• Storage-device replacement.

The ‘present worth’ concept is used so that the cost numbers provided here are directly comparable to the quantified benefits discussed in the Applications section. The costs in the graph are based on certain standard assumptions for the applications and for the technologies and expert opinion. They are meant to be used for illustration purposes only. The actual costs of any storage system depend on many factors and the assumptions and the means of calculating some of the values used are subjective and continue to be debated, even among experts in the field.

For certain applications the energy per unit volume (energy density) or per unit weight (specific energy) of the storage system are also important factors. Volume has a much greater impact on storage technology for automotive applications than for most of the stationary applications considered here. Weight is rarely a factor for stationary applications, so it is not included in this discussion.

The graph below compares storage technology volume to cost as a function of application.

April 2010