At the Intersolar Energy Storage Press Breakfast


Energy storage technologies have been a hot topic in the solar industry this year, and Intersolar North America was no exception. In thinking about the subject, it helps to understand how energy storage may help you. Yes, there is an energy storage option for you.

To get a handle on storage options, Intersolar North America put together this panel of prominent experts over breakfast:

  • Dr. Matthias Vetter, Head of the Department of PV Off-Grid Applications at the Fraunhofer Institute
  • Dr. James (Jim) Greenberger, Executive Director of the National Alliance for Advanced Technology (NAAT) Battteries
  • Chris Edgette, Senior Director at Strategen Consulting


We will sum up the discussion for you to enjoy from the comfort of your desk, and think about how energy storage will fit into your life in the coming years.

One can think of storage applications in four different scales:

Ancillary (10s of MW scale)

These storage systems are for the big boys — transmission operators — who would use these large storage systems to provide a quick response to changing supply and demand, providing consistent energy supply to you at your desk.

Generation (MWs scale)

Developers of large renewable energy projects can use energy storage to provide controlable renewable energy to the grid. This benefits developers by:

  1. Allowing the development of renewable energy projects in areas deemed to be saturated with renewable energy. Practically speaking, in these areas the grid operator would say, “We don’t want more renewable energy because we already have too much and it is ‘unstable’.” To which the clever developer would reply, “My renewable energy is not unstable, because I can guarantee supply with my storage system. Connect my project. Please.”
  2. Allowing the developer to get creative with their power purchase agreements (PPAs). With a storage system, the developer can feed energy to the grid at times when energy demand is highest, and energy is the most valuable.

Load management (100-1000 kW scale)

Commercial entities would use a storage system to help shave peak demand, and thus lessen peak demand charges.

To clarify demand charges, energy bills often have:

  1. Charges just to be connected (fixed costs)
  2. Charges for the quantity of energy used ($/kWh)
  3. Charges for peak demand ($/kW peak)

Let’s assume we had two identical factories (assume equal fixed costs) that used the same quantity of energy per day (eg., 1200 kWh/day). If you use all of your energy between 9:00 am and 11:00 am (that’s 600 kw at any moment in those two hours), and I use the same quantity of energy consistently over a 24-hour period (50 kW at any moment), my energy bill would be significantly lower than yours because my highest energy consumption at any one time was lower than yours.

A helpful analogy is to think of energy as water delivered by a pipe. Think of a kWh of electricity as a gallon of water. Having higher demand at any one time requires a larger pipe. If you want all 1200 gallons delivered between 9:00 am and 11:00 am, you need a big pipe for that time, so you pay a higher peak demand charge.

Oftentimes, a commercial building will see its peak demand at times when PV systems are producing peak energy. In this case, the PV system naturally reduces peak demand. However, if a facility’s peak demand period is evaluated over multiple days, and one of those days is cloudy (meaning low PV system output), then that one day will trigger high peak demand charges for the period. If your building had an energy storage system to supply energy, it would keep your peak demand low on cloudy days and reduce the peak demand charges on your bill.

Time shifting (kW scale)

Time of Day Graph

Following the example above, most residential homes have their highest energy demand in the evenings, when everyone is home. Clearly, there is a low PV system output at this time, so homeowners can install a storage system and program it to provide energy in the evenings, thus reducing their highest energy demand.

In the graph, the red curve is solar production, and the blue is an example of a home’s demand. (See an in-depth study by Tom Murphy, A case study for storage.)

For homeowners interested in the green aspect of this demand management strategy, the lower the peak demand of a community, the fewer fossil-fuel electric generation facilities the utility needs to have online at a given time.

The takeaway

Battery technology is not a new concept, but many energy storage companies are seeing longer battery lifetimes of 10+ years with lithium iron phosphate batteries.

Recycling for these newer types of batteries is evolving, but materials are plentiful, so unfortunately cost is not a driver to rapidly develop improved recycling processes.

While many people understand the benefits of storage, thorough numbers that quantify the financial benefits are hard to come by, and even harder to bank on.

What can be said for sure is that storage will be playing a role in our energy future. Germany is already moving in that direction.