Does Energy Storage Compensate for Thirsty Concentrating Solar Thermal Power Plants?

Date: 28 Jul 2011 | posted in: Energy, Energy Self Reliant States | 1 Facebooktwitterredditmail

Concentrating solar thermal power has promised big additions to renewable energy production with the additional benefit of energy storage.  But with significant water consumption in desert locations, is the energy storage benefit of concentrating solar enough to compete with the dramatically falling cost of solar PV?

In May, I compared the water consumption of fossil fuel power plants to various solar technologies, noting that wet-cooled concentrating solar thermal power (think big mirrors) uses more water per megawatt-hour (MWh) than any other technology.  The following chart, from the earlier post, illustrates the amount of water used to produce power from various technologies. 

Water consumption can be cut dramatically by using “dry-cooling,” but this change increases the cost per kilowatt-hour (kWh) of power generated from concentrating solar power (CSP).  In the 2009 report Juice from Concentrate, the World Resources Institute reports that the reduction in water consumption adds 2-10 percent to levelized costs and reduces the power plant’s efficiency by up to 5 percent. 

Let’s see how that changes our original levelized cost comparison between CSP and solar PV.  First, here’s the original chart comparing PV projects to CSP projects, with no discussion of water use or energy storage.

To make the comparison tighter, we’ll hypothetically transform the CSP plants from wet-cooled to dry-cooled, adjusting the levelized cost of power.

Using the midpoint of each estimate from Juice from Concentrate (6 percent increase to levelized costs and 2.5 percent efficiency reduction), the change in the cost per kWh for dry-cooling instead of wet-cooling is small but significant.  For example, all three concentrating solar power projects listed in the chart are wet-cooled power plants.  With a 6% increase in costs from dry cooling and a 2.5% reduction in efficiency, the delivered cost of electricity would rise by approximately 1.7 cents per kWh.

The following chart, modified from our earlier post, illustrates the comparison.

With the increased costs to reduce water consumption, CSP’s price is much less competitive with PV.  In our May post, we noted that a distributed solar PV program by Southern California Edison has projected levelized costs of 17 cents per kWh for 1-2 MW solar arrays, and that a group purchase program for residential solar in Los Angeles has a levelized cost of just 20 cents per kWh.

In other words, while wet-cooled CSP already struggles to compete with low-cost, distributed PV, using dry cooling technology makes residential-scale PV competitive with CSP.

But there’s one more piece: storage.


While Nevada Solar One was built without storage, the PS10 and PS20 solar towers were built with 1 hour of thermal energy storage.  Let’s see how that changes the economics. 

To make the comparison comparable, we’ll add the cost of 1 hour of storage to our two PV projects, a cost of approximately $0.50 per Watt, or 2.4 cents per kWh.  The following chart illustrates a comparison of PV to CSP, with all projects having 1 hour of storage (Nevada Solar One has been removed as it does not have storage). 

When comparing CSP with storage (and lower water use) to PV with battery storage, we have a comparison that is remarkably similar to our first chart.  Distributed PV at a commercial scale (1-2 MW) is still cheaper than CSP, but residential PV is more expensive. 

Even though dry-cooled CSP competes favorably on price, it still uses much more water than PV.  That issue is probably why many solar project developers are switching from CSP to PV technology for their large-scale desert projects.

Without a significant cost advantage, the water use of CSP may mean an increasing shift to PV technology.

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U.S Grid Can Handle Lots of Solar PV with Low Integration Costs

Date: 10 Mar 2011 | posted in: Energy, Energy Self Reliant States | 0 Facebooktwitterredditmail

A state such as New York should be capable of absorbing and benefiting from well over 7 GW of high- value PV without having to incur significant integration costs beyond the cost of PV itself, further noting that the storage sizes involved could well be met with a smart deployment of interactive plug-in transportation...the low-cost penetration potential is large enough to allow for the development of a considerable localized, high-value PV generation market worth 100’s of GW in the US.

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Increasing On-Site Consumption of Distributed Solar

Date: 22 Nov 2010 | posted in: Energy, Energy Self Reliant States | 0 Facebooktwitterredditmail

It’s rarely mentioned that a home with a solar array still gets most of its electricity from the grid.  In fact, without storage, a typical home solar array might only serve one-third of a home’s electricity use, even if the … Read More

Will Solar PV Kill Concentrating Solar Thermal Power?

Date: 19 Oct 2010 | posted in: Energy, Energy Self Reliant States | 0 Facebooktwitterredditmail

The boon of concentrating solar thermal power plants is their ability to deliver more consistent electricity, and to offer thermal storage (cheaper than batteries) to expand their daily coverage. 

But it might be in serious trouble. And this time the culprit is not cheap natural gas, the Koch Brothers, nor the desert tortoise advocates.

…The relentless price declines of PV panels allows developers to build PV plants at a lower cost than their [concentrating solar thermal] CST cousins. This issue is illustrated in the following Capital Cost per watt chart (an excerpt from the upcoming GTM Research “CSP Report”). In 2010, the price to build a CSP park run by Troughs, Power Towers or Dish-Engines will cost between $5.00 and $6.55 per watt (AC). On the other hand, utility-scale PV projects can limbo below $3.50 a watt (DC).

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Pumped Hydro Storage Still Cheaper Than Batteries

Date: 19 Oct 2010 | posted in: Energy, Energy Self Reliant States | 0 Facebooktwitterredditmail

A nice, short comparison of the cost of electricity storage with pumped hydropower and batteries.

Using pumped hydro to store electricity costs less than $100 per kilowatt-hour and is highly efficient, Chu told his energy advisory board during a recent meeting. By contrast, he said, using sodium ion flow batteries — another option for storing large amounts of power — would cost $400 per kWh and have less than 1 percent of pumped hydro’s capacity.

Of course, you need to have a river with a likely reservoir location to have any significant quantity of pumped storage, making the article’s reference to Texas a bit ironic.

For those unfamiliar with the concept, here’s a nice diagram of pumped storage from Consumers Energy:

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Storage Potential of Electric Vehicles

Date: 19 Oct 2010 | posted in: Energy, Energy Self Reliant States | 0 Facebooktwitterredditmail

One of the keys to maximizing renewable energy production (decentralized or otherwise) is providing electricity storage to smooth out variabilities in wind and solar power production. Electric vehicles have a lot of promise, as the cars could provide roving storage and dispatchable power to help match supply and demand.

So could a large number of EVs actually help with the huge variations in wind that can occur? According to Claus Ekman, a researcher at the Risø National Laboratory for Sustainable Energy in Frederiksborgvej, Denmark, it can, to an extent. Ekman recently published a paper in the journal Renewable Energy that modeled how well EVs could handle increasing wind power generation. He found that in a scenario involving 500,000 vehicles and 8 gigawatts of wind power, various strategies would reduce the excess, or lost, wind power by as much as 800 megawatts — enough to power more than 200,000 homes. Ekman calls this a “significant but not dramatic” effect on the grid. Scenarios involving 2.5 million vehicles and even more wind power show an even greater impact.

The U.S. currently has around 35 gigawatts of wind power, so it would take 2.1 million EVs to provide a similar effect in the U.S. (reducing the lost wind capacity by 10 percent of total installed capacity).

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Policy to Maximize On-site Use from Distributed Generation

Date: 4 Oct 2010 | posted in: Energy, Energy Self Reliant States | 1 Facebooktwitterredditmail

Distributed generation (DG) puts energy production close to where it is consumed, often on people’s homes or in their backyards.  But just having a rooftop solar module doesn’t mean that every kilowatt-hour produced from sunlight is used in the home.  … Read More

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