Has anyone else read this yet? It backs up what's been talked about in here on the storage situation and timeline.
How Much Does Storage Really Cost? Lazard Weighs In.
BTW I really do like RMI very much. I think they do some of the smartest thinking in this space. My earlier reaction was to Lazard, which I don't trust. But the whole key to batteries is how you use them to create multiple value streams.
Stacked use understood as simultaneous may not be absolutely essential. You could also do serial stacking. For example, when you repurpose an EV battery for bulk utility storage, you can get solid lifetime value. In the car, you value high density for optimal range and acceleration, but you might not cycle frequently enough to get full value out of the battery. In utility storage, a battery with 20% less energy density is not a problem, and you can work it several cycles per day using up the cycle life more completely. For example, I only do two 50% charging cycles per week. So that could last more than 20 years. If I want to upgrade to a much better battery (twice the density) in 10 years, then there is still a lot of life in my original battery.
But more generally for stacking we can ask several question about a battery in a particular situation:
1 How does this battery create value when it charges?
2 How does this battery create value when it usually discharges?
3 How does this battery create value by providing available kW capacity?
4 How does the battery add reliability to other system?
These questions tap into different value stream and avoid single use thinking. For example, let's consider a Powerwall integrated with solar.
1 The battery usually charges when there is surplus solar. If the utility pays below the cost of the solar power, then charging with surplus avoids being under paid by the utility.
2 Discharging when there is deficit solar power, avoids paying the utility to import power from the grid.
3 In potential aggregation to provide peak power to the grid, the utility may pay for available kW with an option to discharge the battery at times of peak power. Under this kind of deal, the utility may pay a certain amount per kW per month and a special tariff for peak draws per kWh.
4 The battery provides back up to the solar system so that it can be used during disruption of utility service. This backup value is roughly worth having a back up generator for storms.
When you put all this value streams together, you may be able to arrive at a compelling total benefit that exceeds the cost.
Questions 1 and 2 may seem like overkill on time shift value, but there really is more too it. Apply these questions to an EV battery. People usually ignore question one just thinking of charging purely as a cost. But their are opportunities to use EV charging to create value. For example, utilities have explored dispatchable charging solutions. Suppose you plug your car in and simply need 10 kWh sometime over the next 10 hours. The utility can send charging signals that vary the rate of charge depending on the net load on the gird. In this way the utility can combine baseload generation with aggregated EV charging to eliminate the need for peakers. This will come as EVS penetrate the car market. Currently EVS are under utilized by the grid. We really can get rid of peakers.
