My colleagues in the high tech world may not quite believe this, but electric power on the open market is occassionally priced at less than free - producers will actually pay you to take it.
Here's what happens: utilities or customers enter into power supply contracts including ones that feature "take or pay" clauses for base load capacity. Hydroelectric plants fall in this category because there is a minimum amount of flow through the dam to preserve habitat downstream.
So how do we get to negative pricing? Let's say a utility has 1000 megawatts of take-or-pay base load resources, but in certain times of the year customer load drops below that. Now the utility is faced with paying the generator for power that can't be used. (Easy enough for a hydro operator to back off on production by altering the pelton wheel profile or bypassing the turbines completely.)
Now the utility would be happy to pay a customer to take the power as long as the price was less than what he had to pay the generator (better to pay you a penny a kilowatt-hour than the generators two cents).
In my experience, this is a rare occurence, maybe happening on winter nights when loads are lowest.
But that situation is changing in interesting ways. In the Pacific Northwest, wind producers have contracts that feature take-or-pay clauses, and the operators receive favorable tax treatment based on the actual power delivered to the grid. Bonneville now has something like 30% of their portfolio coming from wind, with much of the rest hydro.
So now, even on some summer nights, customer load isn't enough for the power generated by the hydro and wind plants, and there are significant costs and impacts involved in curtailing the power production. The wind operators in particular don't want to be curtailed because of those tax breaks.
The four state region is grappling with this issue in a positive way - seeking opportunities to engage customers who could use power during these surplus events. They're looking at traditional load shifting strategies like precooling office buildings and refrigerated warehouses, and time shifting electric water heating loads.
And...we're trying to think about how data centers could participate. I personally don't see a pre-cooling strategy being viable, but I keep coming back to thermal energy storage as an exciting solution for data centers. You get load shifting capability (and might even get paid for taking off-peak power sometimes!) along with redundancy in your cooling infrastructure.
I know of only one data center that has implemented a thermal storage system, but I can't help but think this is a larger market opportunity.