eSolar Sierra SunTower: a History of Concentrating Solar Power Underperformance

8.5 GWh (GigaWatt-hour) nameplate electricity capacity reduced to 4.270 GWh.
“Operating” at 12.9% or less of initial 4.270 GWh capacity.

From eSolar Sierra SunTower Project offline – Again

Solar thermal startup eSolar still out there and raising $30M” by Katie Fehrenbacher at GigaOm attracted my attention. I’ve had a side project simmering trying to substantiate my observations and suspicions in eSolar Sierra SunTower offline – Again with actual electricity production data.

Encouraged by my FOIA (Freedom of Information Act) experience with GreenVolts, I initiated an FOIA request with the U.S. Department of Treasury for the eSolar Inc. Sierra SunTower CSP (Concentrating Solar Power) 1603 TGP (Treasury Grant Program) related Annual Performance Reports and Certifications in late August 2012. The FOIA process is slow for me, and I received a response in November 2012 with the performance data (Year 1, Year 2) redacted! Dissatisfied, I filed an appeal:

The entire performance portion of the reports in sections 4.1 and 4.2 was redacted. I contend the Sierra SunTower is misrepresented as an operating facility when in fact it operates infrequently and on an ad hoc basis. I further contend the Sierra SunTower does not meet the IRS requirement for “daily operation” to be considered in service. In order to prove these assertions and the ineligibility of eSolar for the 1603 TGP for the Sierra SunTower LLC project, please release the following information from the Year 1 and Year 2 Section 1603: Annual Performance Reports and Certifications:

Section 4.1
Annual Production (kWh)
If the actual production and estimated annual production (entered in section 4D of the applications) differ, explain the difference:

Section 4.2
Have there been any interruptions in production during the year, other than routine maintenance?
Provide dates and explanation:

On March 19, 2013, the Office of the Fiscal Assistant Secretary (FAS) said: “After carefully considering your appeal, I am releasing sections 4.1 and 4.2 in full.

Sierra SunTower Annual Performance Reports and Certifications
The eSolar Sierra SunTower generated 552.000 MWh (MegaWatt-hour) of electricity from July 23, 2009, to July 23, 2010. This was about 12.9% or just over one-eighth of the initial annual estimate of 4270 MWh! Furthermore, the Sierra SunTower was said to deliver up to 8.5 GWh (GigaWatt-hour) of electricity in official California Renewables Portfolio Standard (RPS) documentation when the actual initial estimated nameplate capacity is almost half that at 4270 MWh (4.270 GWh).

Here is the Section 4.1 and 4.2 text from the July 23, 2009, to July 23, 2010, first year report followed by the embedded documents:

4.1. Annual Production

A total of 552 MWh of gross electrical energy has been generated at Sierra (Appendix 1) during the period July 23, 2009, and July 23, 2010. It was initially estimated that 4270 MWh of gross electrical energy would be generated at Sierra during the same period. The actual generated electrical energy was less than the estimated value due to the following reasons:

4.2 Have there been any interruptions in production during the year, other than routine maintenance?

There were scheduled and unscheduled forced outages experienced surrounding the required commercial boiler and turbine testing, turbine testing, turbine oil system failure and operational restrictions imposed by the LA County Fire Department. The boiler and mirror testing was to establish calibration set points for reflecting the sun flux accurately onto the boiler to for steam production. The turbine lube oil pump system failure required remanufacturing the entire lube oil pump system to precise

In both cases, the text was cutoff and limited to the visible area of the .pdf document provided by Treasury.

The eSolar Sierra SunTower generated 539.124 MWh (MegaWatt-hour) of electricity from August 1, 2010, to July 31, 2011 [Ed note: what ever happened to July 24, 2010 through July 31, 2010?]. This was about 12.6% or just over one-eighth of the initial estimate of 4270 MWh, now unmentioned, over the year period.

Here is the Section 4.1 and 4.2 text from the August 1, 2010, to July 31, 2011, second year report:

4.1. Annual Production

A total of 539 WWh [Ed note: MWh] of gross electrical energy has been generated at Sierra during the period Aug 1, 2010 and July 31, 2011. The difference between the actual and estimated production is due to outages for maintenance and service as well as economic factors affecting the operating profile of the facility. In late 2010 it was determined that the plant should be operated less during non-peak solar resource periods and the operation of the plant was adjusted accordingly.

4.2 Have there been any interruptions in production during the year, other than routine maintenance?

Normal interruptions to production during the year for routine maintenance and service. Additional outages were due to an operating profile change at the plant. Due to cost constraints, the operation of the plant was reduced during non-peak solar resource periods.

I have two quick observations. The Sierra SunTower operated about four (4) maybe five (5) days per month over the 2009 to 2011 period or more often just during peak sun hours. eSolar decided the Sierra SunTower was too expensive to operate except under the highest solar resource periods and perhaps aligned with the best time of delivery utility rates. No wonder I have never seen it in operation. Did eSolar inform partners and customers the ACME Group, Penglai Electric, and GE Energy, a business group of the General Electric Company (NYSE:GE), of the operating profile change?

Southern California Edison data
When I contacted Southern California Edison (SCE), an Edison International (NYSE:EIX) company, one year after the eSolar Sierra SunTower dedication ceremony, SCE said: “Sierra SunTower produced 24 MWh in 2009 and is forecasted to produce 1,563 MWh in 2010.” I was directed to eSolar for further information.

Last week, I asked if SCE files a report with the CPUC (California Public Utilities Commission) on the actual amount of power purchased under the Sierra SunTower PPA (Power Purchase Agreement) on an annual basis? I expected to hear it was confidential and was wondering if an FOIA request would fly at the CPUC? The SCE spokesperson said: “Annually, SCE files an RPS compliance reports that indicate actual and forecast generation data that is not confidential. SCE filed its 2011 Preliminary Annual Compliance Report in Dec. 2012, see attached.

On page 37 (row 136) of the SCE 2011 RPS compliance report, the Sierra SunTower, LLC generated an actual 283 MWh in 2011 and forecasted 287 MWh under the Final Resolution E-4295 PPA. Though E-4295 approved a one year term, SCE said: “The original qualifying facility (QF) contract that is cited above was extended for approximately one year, per CPUC Decision 07-09-040, and later terminated. Thereafter, Sierra SunTower executed a new QF Standard Offer power purchase agreement, which is scheduled to end 6/1/2013.

E-4295 promulgated the 8.5 GWh production figure although the advice letter states: “The PPA is a short-term, bilateral contract for as-available output from a test facility that eSolar built in Lancaster, California to evaluate and demonstrate its solar tower technology.

While the date ranges differ, the SCE electricity production figures versus the performance reports submitted by eSolar to Treasury don’t seem to reconcile when eyeballing them. Perhaps the U.S. Department of Treasury should consider auditing the eSolar Sierra SunTower performance reports and reconcile them on an annual calendar basis with the data SCE has reported to the CPUC?

The $19.5 million eSolar 1603 Grant for the Sierra SunTower has been audited by Treasury once before:

RECOVERY ACT: Audit of Sierra SunTower LLC Payment Under 1603 Program
July 7, 2011

The Office of Inspector General, Department of the Treasury, concluded:

Sierra SunTower’s reported cost basis of $65,145,499 for the subject property included $117,497 for costs that we believe do not comply with Treasury Regulation (Treas. Reg.) §1.263A-1.

In the end, Treasury recommended and eSolar concurred to reimburse $35,249 for the excessive 1603 Program payment received because of the overstated Sierra SunTower cost basis.

As I’ve asked before, at what point does a specified energy property operated as a test facility on an ad hoc basis no longer qualify for a 1603 Treasury Grant at all?

Of course, I saw the eSolar Sierra SunTower offline as usual after the AVSR1 harassment experience during my southwest road trip.


  1. This is really a sorry state of affairs. I can not find any reasons for this situation but surely could help in reviving the plant to enhance the efficiency to a decent value.

  2. Matt says:

    I’ve never found a reference to the construction cost for this plant. Can anyone help me out?

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