by Vince & Mary Palermo

On Thursday, September 9, 2010, eight concerned residents from Saguache, Moffat, and Crestone visited Tessera’s first solar electric plant located in the northwest sector of the Phoenix, AZ, area (Maricopa County).  This trip was supported by Tessera as a result of an early commitment by them to sponsor a visit for interested residents of the area.  We thank Tessera for making possible this visit which provides an experience of their installation not possible by just reading about it.

The first and immediate observation is that the plant site is in the middle of an industrial zone.  It is bounded on the south side by a substation and an on-demand gas-fired electric generation plant; on the west side by a busy four lane highway; on the north side by a shipping company; and on the east side by a corn field.  It was a clear, sunny day and ideal for assessing the operation of their 60 Suncatchers and experiencing the noise generated by the units in full sun conditions.  We had the opportunity to have an indoor  presentation and then ask every question in our minds. The supervisor and servicemen were very responsive and fully answered our enquiries.

Significant is the fact that the application and approval process for their Maricopa plant took three months to complete.  There were no environmental or sound issues because of this location, and building the plant had no obstruction or complication.

Let’s now look at the technical sound observations at the Maricopa plant.  Unfortunately, on the last day before the trip, the management declined permission for Vince to take sound measurements within the boundaries of the plant.  That was a detractor from proper assessment of within-field sound because, as expected, the noise level varied greatly as we walked about the field near the Suncatchers.  Interestingly, the “quietest place” was standing immediately under the last Suncatcher of a row.  That is because the parabolic mirror on the Suncatcher reflects the sound upward just like the light.  Elsewhere, the sound becomes very loud, variable, and is maximum between rows. So, the HDR report of 73.6 dBA and 76.9 dBA within field are clearly two selected readings and do not reflect complete reporting of the sound field observations.   Obviously, HDR took many readings that are not shared in their report.  HDR is an architectural design and consulting firm chosen by Tessera to evaluate and report the assessment of the sound impact by their proposed Saguache plant.

All of our sound measurements were taken immediately outside the fence lines.  On the west side we read 66 dBA, which was the farthest distance from the Suncatchers. On the north side there  were six readings of  67 dBA to 72 dBA. This was over 100 feet from the rear of the Suncatchers since it was noon and the units were facing directly south.  On the east fence line we were closest to the Suncatchers and took eight readings from 71 dBA to 76 dBA, our loudest measured readings.  We took no readings at the south side because this was an electric substation and the gas electric plant which was not in operation at that time.  This could have been the loudest fence line because the Suncatchers were facing south.

What is equally, if not more significant, was the subjective sense of the noise.  The noise is a harsh mechanical sound generated by four cylinder engines running at a constant 1,800 rpm.  Vince’s own personal feeling is “an oppressive, monotonous drone.” He says he has a mild high frequency hearing loss usual with aging and yet “this is loud and objectionable to me. Quietude and natural sounds are a high value to me, so I am clearly biased against this noise quality.”  And Mary says, “The noise is very harsh to me.  The sound in each Suncatcher motor is very  noisy in contrast to the electric (PV) plant in Mosca.  Quietude is also of paramount importance to me, so I, too, object to this sound.”

Next, it is important that the residents of Saguache County know that the HDR noise report that Tessera has submitted as an assessment of sound impact in Saguache is, in our opinion and in the opinion of  Skip Ambrose, a professional environmental acoustic consultant, based on incomplete and erroneous baseline data, uses inappropriate application of standard acoustic metrics, and is totally misleading in its conclusion.  It was written to try to convince our Commissioners the noise would be no more than 10  dBA above ambient sound levels. This is not the case, since noise from the facility would be much greater than 10 dBA above ambient sound levels.

First, let’s look at baseline ambient sound at the Saguache site.  HDR chose a 24-hour period, April 15/16,2010, during which our spring winds are strongest, and during which there was rain recorded in Saguache County. HDR subtracted thunder peaks of 100 dBA but retained the wind sounds to give a reported ambient sound level of 42 dBA.  Standard measurement of ambient sound requires concomitant recording of wind speed so that sound readings are eliminated when wind speed exceeds 11 mph. HDR did not do this.   On three separate occasions we have recorded a baseline ambient of  27 dBA at the Saguache site in the absence of high winds.

Second, let’s look at HDR predicted sound level at the perimeter of the proposed plant here in Saguache.  Feeding their selected readings from Maricopa and Sandia into a German-based acoustic computer-modeling program which gives predictive sound levels, they state that at only one point on the perimeter will the noise level reach as high as 52 dBA!  They have met—on paper—our solar regulation requirement of no more than       10 dBA increase above ambient!

Tessera’s HDR report defies the laws of physics, as well as anyone’s common sense.   They are asking us to believe that adding 7,940 Suncatchers to 60 Suncatchers will produce 23 dBA less noise than at Maricopa!  This is impossible as well as not believable. Further, it is surprising that Tessera would publish this seriously flawed report. It is as though it was hoped the true facts would not be noticed under the veneer of professional acoustic jargon and the corporate HDR name. From our measurements, their Maricopa plant with only 60 Suncatchers is 49 dBA above the ambient sound level at the Saguache site.

In conclusion, the Tessera Suncatcher approach is a good solar technology that will help to counter global warming, and merits long  term operation and evaluation in the California desert where they have  two massive projects underway.  It is clearly, in our opinions, not appropriate for Saguache County where there is no equivalent industrial zone as in Maricopa County.

The quietude, which is our natural heritage, will be shattered if this plant would come to be.  The sun will continue to shine in our Valley and there will be many other choices of solar technologies.  It behooves us to make the best choice now because we will be living with it for a long time.  And hopefully, living in confidence that we have made the right choice, a choice that will satisfy our energy needs and preserve the beauty and quietude of our Valley.