Experts point out that there are two different stages in which CSP energy can be stored – heat can be stored before the generation of electricity and the same can be done after electricity generation.

Plus, various storage types can be co-located with the CSP plant except for pumped storage, and all can be located remotely, except for heat storage.

However, it is said that it is difficult to predict which system would have the largest overall efficiency (dispatchable electrical energy/captured solar heat.)

It is said that a thermal storage capacity of four hours increases the investment for a CSP unit by around 1.5-2 M€/Mwe.

According to Solar Southwest Initiative, which is working on creating the policy conditions that will allow CSP plant builders and utilities to work together to realise the potential of desert power through integrating solar thermal plants with 6 to 24 hours of thermal storage, paired with enough thermal storage and solar collectors, a CSP plant can operate as baseload power.

Alternatively, a CSP plant with storage can be built to scale up and down to follow the load, peaking its power output in mid-afternoon when power demand is highest on summer days.

With storage and with a steam generator and turbine already warmed up, a CSP plant with storage can be dispatched to meet peak demand within a few minutes.

The usefulness of CSP with storage as a coal and natural gas power plant replacement is then clear in an era of carbon-constraint and concern about climate stability.

It is being said that some CSP technologies can be dispatchable, delivering firm power during peak demand. Trough and tower plants using thermal storage or supplemental fossil-fired components are particularly suited to this purpose.

Assessing the situation, Plataforma Solar's Dr. Eduardo Zarza, who is scheduled to be a part of the 2nd Concentrated Solar Thermal Power Summit, to be held on 12-13 November in Seville, says thermal storage is a ''must'' if we want solar thermal power plants to play a significant role in the future energy market.

"Though hybridisation with fossil fuels (e.g., natural gas) is already posible and problem-free, cost-effective thermal storage systems must be available in order to achieve full sustainability concerning the environment," Dr. Zarza told CSPToday.com.

He added: "Though there are already cost-effective thermal storage systems for parabolic trough plants (i.e., molten-salt systems with two tanks) due to the tax incentives and feed-in tariffs, thermal storage for dish-stirlings and solar towers still needs significant R&D work, which is also required to significantly reduce the cost of molten-salt systems for parabolic trough plants."

"In my opinion, development of cheap and reliable thermal storage systems for CSP should be considered as a high priority target in R&D programmes related to solar thermal power plants."

In a recent interview, Artur Zawadski, manager, business development and project delivery, Wizard Power shared with CSPToday.com that the ammonia based thermochemical energy storage system is designed for utility scale power plants with tens to hundreds of megawatts capacity.  The storage solution is capable of providing load-following power on demand on a 24 x 7 basis.

Because the storage is done thermochemically and not thermally, the storage time is indefinite with no energy losses at the point of storage, says Zawadski.

The ammonia synthesis technology and its integration to steam turbine power generation systems is an industry standard technology used within the ammonia production industry. It is now being commercialised by Wizard Power. 

The ammonia based thermochemical energy system is expected to be commercially available in 2011. 

According to Zawadski, the Whyalla demonstration project is a key step in the optimisation of the storage component and integration of this with commercial-off-the-shelf ammonia synthesis technology. 

It is a key step in the commercialisation of this technology, according to Zawadski.

2nd Concentrated Solar Thermal Power Summit

Plataforma Solar's Dr. Eduardo Zarza and Artur Zawadski, manager, business development and project delivery, Wizard Power are scheduled to be a part of the 2nd Concentrated Solar Thermal Power Summit, to be held on 12-13 November in Seville.

For more information, click here: www.csptoday.com/eu/programme.shtml

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Contact Belen Gallego by email: belen@csptoday.com