Do you remember, in 2011, these really catchy stories about “Cambridge crude”?

Cambridge crude was that very thick, syrupy, energy-dense liquid, doped with nanoparticles, that was developed at MIT for use in a flow battery. It was going to revolutionize flow batteries because of its incredible energy density, and was aiming for a total system price point of $100/kWh – the famous DOE price point goal.

The technology was licensed by MIT to a A123 spinoff named 24M, which raised  $10M+ from Charles River Ventures, and got an ARPA-E contract for another $6M. The contract was for 3 years, and came to completion in summer 2013, at which time they were going to have a full working prototype.

24M has been awfully quiet ever since the Cambridge crude stories, and we did not hear a peep at ARPA-E contract completion either. I was always interested in the idea of a high-energy-density flow battery: after all, it’s like having your cake and eating it! I am trying to get more information on 24M progress. I hope no news is good news 🙂

Hopefully, I’ll be able to post some more information in a few weeks. So stay tuned!

How long can an energy storage module keep on powering the grid at its rated output?

The answer to this question is the Energy to Power Ratio:

E/P = MWh/ MW = hours (or minutes or seconds)

A funny thing is that it is such a basic question for all energy storage devices and technologies, but, strangely, it is rarely easily available information.

Most news releases will mention the nameplate capacity or power rating (in MW), without mentioning the energy capacity (in MWh) or the duration over which the power rating can be provided (in seconds, minutes or hours).

If you want to know as much as possible about a storage device in two numbers only, the best way to do it is to ask for its rated output and its energy to power ratio.

I wrote a more detailed discussion of the energy to power ratio here.

It is confusing, isn’t it? In some cases we use “energy” or “power” indifferently, and in other cases we don’t.

To be clear: what the electric company charges you for is energy, in kWh. It’s a kWh that costs $$. The rating on your appliance is a power rating, in kW: it defines the rate at which your appliance consumes energy.

In the same way, a generation plant’s nameplate capacity is a power rating in MW or GW, Its output, over a day, a month, or a year, is energy, in MWh or GWh.

I feel the need to mention this because I want to post about the energy to power ratio soon…

I wrote a detailed page on the difference between energy and power here.