Storing Renewable Energy on the Smart Grid

What about converting energy from wind turbines to compressed air and feeding the compressed air to the air inlet of of a turbine.
Compressed air and fogging increase the efficiency of turbines. These are known and proven technologies.
An additional advantage is using distributed power generation. This leads to dependable power output irrespective of availability of wind, and to stable frequency.

Mr. Lacey:
You forgot the most imminent power storage of all the methods. It is hydrogen with fuel cell conversion of the hydrogen back to electricity at night. There is already a small hydrogen-fuel cell system (1/2 MWe) in operation in N. Dakota.
We are pursuing this route for a 2 MWe 24/7 solar-hydrogen power test facility.
Compressed air with cavern storage has been proven to be in efficient and very few places in the U.S. have the proper underground rocky formation to prevent leakage.
As far as fly wheels for large energy storage (>5 MWe), forget it ! Too expensive.
Warren, Eco-Engineers, Inc.

The pumped hydro electric energy storage uses lower and higher reservoirs, where the water is moved up by a pump, when energy is available and moves down to power the water turbine. Similar principle can be applied creating a solid mass version, where a heavy mass will be elevated by a motor, and the potential energy can be used to power the generator. This system does not require two strategically positioned lakes and does not suffer losses due to water evaporation. But the safety is an issue, if the heavy mass drops suddenly it will be equivalent to an earthquake. To avoid this the mass could be divided into smaller peaces and operated separately.

We will look at pumped storage in detail this summer, when we feature a series on hydropower technologies of all sorts.

It seems clear that the next stage of this discussion needs to address hydrogen production and storage. When you have excess capacity, you use it to produce hydrogen by electrolysis. When you need more capacity, you put the hydrogen through a fuel cell. Metal hydride storage is very well-suited to this type of application. It is a proven technology (in use for decades), and when not in use, basically will not leak down like other storage media can, since the hydrogen is temporarily bonded to the hydride. The metal alloys can also be customized to each particular situation. Stationary electolyzers and fuel cells can be very efficient and reliable, which are features utilties need. Batteries, flywheels and the like may have their own specialized applications, but hydrogen storage is universally applicable and has the least possibility of leaking out energy that has been stored. I think it highly likely that this will be the way utilities will go to even out production times for solar and wind, especially as these sources increase their percentage of the energy market.

4-24-09 Just read about your comments of storing energy.
I have been working on Storing Hi Values of Heat since the
late 1970. The heat can be stored in a very cheap material.
The heat can then be used to 1. Heat industry and homes;
2. Generate Electrical power. To finish my project I need
help from a Computer expert in "FEA" programing who
can set up all the Thermal; Chemical; and Structrual Prameters
to find Safety factors and Large Capicity or small Capacity usage.
The FEA program out come will tell if the Project will FLY without
building a large expensive model. Thanks ALAN

NREL did a study combining a year of a wind farm's data, a year of a city's load data, and several storage methods. They ran an optimizer to determine the most cost-efficient way to reach various levels of power availability.

The power storage methods included flow batteries (high energy capacity cost) and electrolysis of water, storing the hydrogen in the wind turbine towers, and converting back to electricity with fuel cells (low energy capacity cost, high power capacity cost).

The optimizer didn't choose to make any hydrogen. The researcher thought the cost of the fuel cells was the problem (power capacity cost) so made them free. The optimizer still didn't choose to make any hydrogen. The real problem was that the round-trip efficiency of electrolysis and and fuel cells is poor.

The ability to store energy is one issue confronting my community. The Electric company here pays for excess solar energy since it goes back to them. No provision for storage for later use.Today, I am happy to read of the Storage considere as "holy grail" of clean technologies. I hope my community in Nassau New York will benefit from this sensible innovation.
http://www.solarelectricityhome.net

I disagree with the premise that storage is the holy grail for renewables. We're still at just over 1% penetration for non-hydro renewables. Until renewables reach more than 20% penetration in the US, the best and cheapest kind of storage will be the coal pile, gas in the lines, or the hydro reservoir. Allow traditional generation to back off while letting renewables run full force. At this time, costly storage schemes are an answer searching for problem that doesn't exist.

How about 20 million 10-50KW free storage units, that gathere excess at night and put back into the grid during peaks. They are called plug-in vehicles with with the new lithium batteries have thousands of charging cycles.

ACPropulsion already makes one the eBox. You can drive, or charge or sell. It displaces oil/gas ,helps the grid at night buying and storing, then sells during the days.

With the right incentives and we all win. Feed In Tariff, Time of Use, Green REC metering.

Utilities always have a baseload of coal generating capacity. Since a wind farm or several wind farms are actually below the generating capacity of all the coal boilers, then it would make sense to let the wind farms go and let them produce at their full generating capacity. Some utilities have natural gas burning plants in their operating territory which serve as peaking plants. These natural gas boilers can come on line in a hurry (so I am told). But, here in America, each utility has the capability to buy and sell electricity on the market on a demand basis.

Those utilities that are weak cannot have a wind farm go from a full term production to a varied production output in a short time. This is mostly seen in island nations or third world countries.

Years ago, I was in a control room of a wind farm. The utility had called to tell the wind farm to slack the production due to the inductive reactive power that they were causing on the power lines. Of course, the wind farm developer was being paid for the power that they would have produced. I am sure that they have overcome this problem--since that was back in 1995. Too bad that the wind farm could not continue to produce power and store it in a alternative method as discussed here.

I am of the opinion that HYDROGEN is the common denominator that is
needed for all of the new renewable energies that are going to be coming
online. A while back I read in Scientific American about some physicists
that were working on the concept of sending electricity and cryogenic
hydrogen together.....say from one coast to the other (as DC current)
with almost no line-loss. You would be delivering electricity and
hydrogen at the same time.