Comments on: Does Energy Storage Compensate for Water-Thirsty Concentrating Solar Thermal Power?

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By: Wookey

Wookey — Mon, 24 Oct 2011 01:36:00 +0000

Interesting analysis, thank you.

The andasol 3 50MW plant that was just commissioned (and 1 & 2 that have been built over the last couple of years) have 7.5 hours of full-power thermal storage. That makes them ‘normal’ power stations from the POV of the grid/utility people, and it can run 24hrs in summer, which I think is the ‘killer feature’ which means there will be more of them. They quote a cost of 0.27€/kWh, which is 0.37$/kWh. That’s a lot more than you are quoting here- not sure if those costs are subject to any relevant adjustments.

By: Anonymous

Anonymous — Thu, 06 Oct 2011 16:34:00 +0000

An hour of storage seems either too little or too much. It’s not enough to shift power to cover the peak demand in the late afternoon & evening, but it’s more than enough to smooth the fluctuations in power as clouds go over the PV array.

By: John Farrell

John Farrell — Wed, 05 Oct 2011 14:14:00 +0000

Good points about the other renewable technologies. I may add some others in a future analysis.

On the issue of storage time for CSP, my comparison is spot on. Thermal storage capacity may be cheaper for a longer time period, but the existing CSP plants with storage do not have long-term storage. Thus, the comparison I did is an apples-to-apples comparison of commercially-deployed solar technologies, and it probably explains why a lot of CSP plans are being changed to PV.

I think CSP has the potential to work as you envision, but as it is currently deployed, PV is eating its lunch.

By: Breath on the Wind

Breath on the Wind — Wed, 05 Oct 2011 12:27:00 +0000

It would be good to bring in some other renewable technologies when comparing their water use. Dry well geothermal, also has a water use but the capacity factor is on a par with nuclear energy (90%). Solar downdraft towers actually can produce fresh water from seawater. Solar updraft towers won’t use water at all. Traditional wind also is not a water technology.

Your comparison of 1 hour of energy storage for both CSP and PV is a bit unfair as heat storage remains far cheaper than battery storage. Battery storage has yet to go below about $300/kwhr and installing this kind of multiple megawatt capacity to backup a utility scale PV installation absolutely can’t compare with the 8 to 14 hours that are presently being built into new CSP plants using molten salts. Using heat storage with PV is possible but less efficient as it requires at two additional changes in the energy form.

Such potentially long and inexpensive storage for CSP increases the capacity factor of a CSP plant beyond what PV can hope to achieve. It is not clear that this is adequately measured in your calculations.

Another advantage of CSP plants is that they can easily be made into a hybrid with traditional Rankine cycle thermal power plants. If the sun is not shining or at night the traditional fuels can be used as necessary and then during the day the same boiler and generation equipment can be used with CSP.

If a PV installation is not using water to regularly clean the panels they are using chemicals. Dirty panels suffer about a 10% efficiency loss.

For all of these reasons CSP continues in its utility.