Comments on: California Storing Energy in Ice to Reduce Peak Demand

By: Doug Ziebell

Doug Ziebell — Mon, 01 Feb 2010 21:06:46 +0000

My original comment was meant to forestall any thoughts that one could think of this system as functioning like a battery (for example). This incorrect thought was further encouraged by the story’s description that the smart grid would intelligently dispatch the energy that had been stored. Both concepts are misleading at best.
To further clarify the Environmental Leader comment: This is not a way of storing thermal energy. Thermal energy is just heat, and this is certainly not a way to store heat. Your car analogy is a somewhat better one, since it relies on the concept of potential energy. In this case, it is the separation of heat energy, which otherwise tends to spread uniformly throughout any environment, into a cooler zone (the ice, with less heat energy) and a hotter zone (the environment outside of the ice storage container, with more heat energy). This separation of heat energy into zones is analogous to potential energy.
For Brion: It does tend to require less electricity to freeze the ice at night, since the refrigerating equipment dumps its excess heat into a relatively cooler nighttime environment. During daytime air conditioning, the refrigerator unit has to dump its heat into a relatively warmer daytime environment. That’s accomplished only at the price of reduced efficiency.
For Marc: There’s no real utility to a concept of negative potential energy. With respect to your capacitor analogy, what the capacitor really stores is a separation of charge, just like the separation of heat energy described above. To say that it stores “the absence of electrons” is in my opinion also misleading.

By: Marc Simmons

Marc Simmons — Sun, 31 Jan 2010 23:31:56 +0000

Doug, thank you for responding that question about “is it storage.” I think the other way to look at it is storing negative potential energy. Seems funny, but certainly SOMEthing is being stored and used later. It’s like storing a positive charge in a capacitor, since what is actually stored in that case is the absence of electrons.

By: Brion

Brion — Sat, 30 Jan 2010 01:20:17 +0000

How does this reduce greenhouse gas emissions? Just want to better understand. Does it require less electricity to freeze the ice, than it does to run the A/C system? If we’re just moving KWH to off-peak times, then there’s no environmental effect. If the combination of systems uses less KWH overall, then I see the savings.

By: Environmental Leader

Environmental Leader — Fri, 29 Jan 2010 13:27:11 +0000

Thank you for your comment Doug. While this is not the same as storing an electrical charge in a battery, it is a way of storing energy, thermal in this case. An analogy could be made to using electricity to push a car to the top of a hill during non-peak demand, then letting the car put the energy to use as it coasts down the hill at a later time.

By: Per Lorentzen

Per Lorentzen — Fri, 29 Jan 2010 01:42:26 +0000

Doug, if you feel that way, you will wish to modify the Wikepedia discussion of this technology under both “Thermal Energy Storage” (http://en.wikipedia.org/wiki/Thermal_energy_storage) and “Energy Storage” (http://en.wikipedia.org/wiki/Energy_storage“). It is this lay person’s understanding that the thermal energy used to make the ice (performed more efficiently at night due to the lower ambient temperatures, as well as less expensively with abundant off-peak baseload power such as nuclear) has been effectively stored until the period of peak demand during the day. Brilliantly simple load-shifting!

By: Doug Ziebell

Doug Ziebell — Thu, 28 Jan 2010 19:26:28 +0000

Let’s at least get the facts straight. These systems do not store energy. They simply use off-peak energy from the grid to pre-cool the water/ice. Later on, during peak energy consumption, the pre-cooled ice is then used to cool the attached building as an alternative to using grid electricity to do so.
And the smart grid will not intelligently dispatch stored energy (since no energy is stored). Instead, it will intelligently turn off air conditioners in the event that pre-cooled ice is available to take over the building cooling task.
This is a proven concept, and a good move. But I hate to see such lackadaisical reporting of factually incorrect material.