This is the report where you got that picture from. On page 44 are the assumptions for storage costs: 100 to 400 MWh of storage, assuming they are charged and discharged 315 times per year (so eg. 31’500 MWh storage output per year for 100 MWh capacity). Those do not need to be 100% cycles, but given that a year has hardly more days than 315 and some days even see no production, they need to be cycled pretty much every day the sun is shining. Anyway, what is my point? We need more than a few hours of storage to make it work. But the more storage you have, the less you actually use it, making it disproportionaly more expensive. Note what they say:
Lithium-ion batteries remain the most cost competitive short-term (i.e., 2 – 4-hour) storage technology
We need more than 2 or 4 hours. A single night is already far longer than that. The shorter the storage duration, the cheaper it is. Of course this skewes the numbers. It is like calculating the storage cost of nuclear waste for only 2 years. Of course it looks better.
This is the report where you got that picture from. On page 44 are the assumptions for storage costs: 100 to 400 MWh of storage, assuming they are charged and discharged 315 times per year (so eg. 31’500 MWh storage output per year for 100 MWh capacity). Those do not need to be 100% cycles, but given that a year has hardly more days than 315 and some days even see no production, they need to be cycled pretty much every day the sun is shining. Anyway, what is my point? We need more than a few hours of storage to make it work. But the more storage you have, the less you actually use it, making it disproportionaly more expensive. Note what they say:
We need more than 2 or 4 hours. A single night is already far longer than that. The shorter the storage duration, the cheaper it is. Of course this skewes the numbers. It is like calculating the storage cost of nuclear waste for only 2 years. Of course it looks better.