My visit to EUCLIDES

This past December I spent two weeks on vacation on Tenerife, one of the Canary Islands (Spanish, about 150km off the north-west African coast). While I was there I visited the ITER (Institute of Renewable Energy Technology) which is host to the second stage of the EUCLIDES project. EUCLIDES uses concentration photovoltaic modules to produce electricity so it is pretty unique. ITER also has a fairly large wind farm of at least 20 tall 3-blade wind turbines generating about half a megawatt each.

I have been informed that there are a few inaccuracies with the data on this page, so until further notice, this is a work in progress. Fortunately there is eventually going to be more accurate information available at the website of the ITER.

My journal entry

Dec. 15, 1998 11h30: Christiane and I arrived late at the ITER (in the industrial zone of San Isidro) after getting stuck in a traffic jam in Puerto de la Cruz and lost in Santa Cruz.

We had to ask at least three people before we could find Julián Monedero, the guy I talked to on the phone yesterday. Julián is a young physicist who has been working at the ITER for the last 1.5 months with the team who assembled EUCLIDES.

He started by telling me the basic specifications of the plant: 480kWe, 14 long parabolic troughs oriented north-south, 7 inverters. [For more information, see http://www.iter.rcanaria.es/Euclides.htm (in Spanish) or http://www.users.globalnet.co.uk/~blootl/trackers/eucl.htm ]

He then went into detail about the aiming algorithms. The system dead-reckons to 0.2° precision using math and then uses a learning algorithm that adjusts the troughs by trial-and-error in +-0.1° steps to compensate for structural errors. This is done by first maximising the output from one of the concentrating PV modules and then maximising the output from whole line of modules. This learning algorithm is activated on clear days, based on the output of a small PV cell located at the south end of the trough.

The support structure is made of a network of steel beams and is heavy enough that it visibly sags in the middle. For this reason care must be taken to run the learning algorithm only around mid-day when the troughs are pointing at the zenith rather than at dawn or dusk.

The support structure is quite complicated and due to the large number of pieces that must be assembled by hand, it required a lot of work to put together. [From what I've seen in photographs, the Kramer Junction troughs are far more elegant in their use of steel, but perhaps their focusing requirements are not so stringent as the EUCLIDES power plant. In addition, the EUCLIDES site is near the sea, in a high-wind zone.]

The mirror panels are made by laminating a thin reflective surface (perhaps 1mm) to a thicker metal backing (perhaps 3mm). The lamination is snap-riveted to a frame and the frames are attached with long, hand-adjusted bolts to the trough support structure. [See the included email from Julian at the end of this note concerning mirror materials.] The mirror trough is constructed in sections with mirror plaques about 2 metres long and 1.5 metres wide (if flattened).

The tilt adjustment mechanism is a large wheel in the center of each long trough with a diameter about half the width of the trough. The wheel is supported on two small rollers and torqued by thick steel cables that are pulled by a heavy screw-jack mechanism. Tilt measurement is done with a magnetic sensor pair at the zenith mark and a system for counting motor turns (optical?). The motor is not a step motor.

Each trough has its own controller unit capable of manual input, local computer input (through a 9-pin RS-232 port?), and remote control. In addition, each controller has a GPS antenna for receiving the time signal.

Each trough half has a line of PV modules to receive flux. The PV cells are 4cm wide and each module is 1m long with 10 cells each (?). The modules are air-cooled with a set of aluminium fins on the back. Since the modules are connected in series, each line of modules develops 900VDC(?!?)

We next went to the inverter/control building (still under construction) where I talked to the guy in charge of the inverter system. Most of what he said went over my head except the following. Their system is all homebuilt to be quite modular with each inverter box handling 2 troughs. The inverters are in cabinets about 2m high, 1m wide, and 0.5m deep of which the high power electronics take very little space. The inverters feed well-conditioned current to the grid with less than 2% harmonic distortion. (He said that one usually sees at least 3% to 5% in household current.)

Email from Julián regarding mirror materials

Hi Erik,

    In response to your e-mail, I should say that the EUCLIDES project is
using three different type of mirrors in order to study the efficiency
of different technologies.  These materials are:

1) 4 out the 14 arrays of the plant are using a 0,4 mm. ANOFOL 1000.9
layer as the reflecting layer, over aluminium 5754 H111 base layer of
1,5 mm.

2) 9 arrays are using Sylverlux SS95P made by 3M (silver) of 1,2 mm. over
aluminium 5754 H111 base of 1,5 mm.

3) 1 array is using a silvered layer already laminated over an aluminium
layer made by ALCOA.

    I hope this information is good enough for you. If you would like to
know something else, do not hesitate to write to me. I couldn’t see your
web page because there is some problem with my server. I will tell you
my opinion once I take a look at it.  I wish you a Happy New Year.

Julián Monedero julian@iter.rcanaria.es

The photos

Hopefully the photos in this section will clarify the above journal entry. As usual, click on the thumbnail for an elarged view of the image.

	A view of one of the EUCLIDES parabolic troughs from the top of the control building. JPEG 37k
	Another view of the troughs from the control building, this time showing a few of the many wind turbines hosted by ITER. The man in the field gives an idea of the scale. JPEG 42k
	Yet another view of the troughs from the control building. JPEG 48k
	A close-up of the underside of one of the troughs. Note how the square-profile mirror frames are attached to the rest of the structure using long, thin adjustment bolts (four are visible). The snap rivets holding the mirror panels to the mirror frames are barely visible. JPEG 35k
	The tilt mechanism at the middle point of each trough. JPEG 44k
	A closer view of the tilt mechanism showing two of the steel cables that pull on the big tilt wheel. The cables are pulled using a screw-jack. JPEG 45k
	Julián and Christiane by the tilt mechanism. JPEG 52k
	Christiane beside the control module of one of the troughs. The GPS antenna is the bent pipe above module. JPEG 38k
	One of the seven inverter cabinets. JPEG 32k
	A trough actively tracking the sun. Notice the line of solar radiation focused on the PV modules. JPEG 30k
	An inactive trough, tilted to the west for a better view. Note the solar cell at the centerline of the trough and the wind turbines reflected in the upper half of the trough. JPEG 38k

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