Wind energy storage technologies - Wind Power Generation and Wind Turbine Design - page 672

4.3.3 Disadvantages of CAES
The major disadvantage of CAES facilities is their dependence on geographical
location. It is diffi cult to identify underground reservoirs where a power plant can
be constructed, is close to the electric grid, is able to retain compressed air and is
large enough for the specifi c application. As a result, capital costs are generally
very high for CAES systems. Also, CAES still uses a fossil fuel (gas) to generate
electricity. Consequently, the emissions and safety regulations are similar to con-
ventional GTs. Finally, only two CAES facilities currently exist, meaning it is still
a technology of potential not experience.

4.3.4 Future of CAES
Reservoir developments are expected in the near future due to the increased use
of natural gas storage facilities. The US and Europe are more likely to investigate
this technology further as they possess acceptable geology for an underground res-
ervoir (specifi cally salt domes). Due to the limited operational experience, CAES
has been considered too risky by many utilities [14].
A number of CAES storage facilities have been planned for the future including:

• 25 MW CAES research facility with aquifer reservoir in Italy

• 3 100 MW CAES plant in Israel

Norton Energy Storage LLC in America is planning a CAES with a limestone

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mine acting as the reservoir. The fi rst of four phases is expected to produce
between 200 and 480 MW at a cost of $50 to $480 million. The fi nal plant out-
put is planned to be 2500 MW.

Finally, proposals have also been put forward for a number of similar technologies
such as micro-CAES and thermal and compressed air storage (TACAS). However,
both are in the early stages of development and their future impact is not decisive.
Although Joe Pinkerton, CEO of Active Power , declared that TACAS “is the fi rst
true minute-for-minute alternative to batteries for UPS industry” [3].

4.4 Battery energy storage

There are three important types of large-scale BES. These are: lead-acid (LA);
nickel-cadmium (NiCd); sodium-sulphur (NaS). These operate in the same way
as conventional batteries, except on a large scale, i.e. two electrodes are immersed
in an electrolyte, which allows a chemical reaction to take place so current can be
produced when required.

4.4.1 LA battery
This is the most common energy storage device in use at present. Its success is due
to its maturity (research has been ongoing for an estimated 140 years), relatively
low cost, long lifespan, fast response, and low self-discharge rate. These batteries
are can be used for both short-term applications (seconds) and long-term applica-
tions (up to 8 h). There are two types of LA batteries; fl ooded lead-acid (FLA) and