Ivanpah Unit 1 specifications on a square-field basis

Ivanpah Unit 1 sits on a 1995 m x 1995 m square of land.

The previous post makes me think it is necessary to pro-rate the specifications of CSP power tower's over the area of the square of land they take out of use. Here are the specifications of Ivanpah Unit 1 on that basis.

Peak Rating of Units 1 + 2 + 3 = 392 MW

Electricity Generation Expected from Units 1 + 2 + 3 = 1,079,232 MWh/yr

Overall Capacity Factor for Units 1 + 2 + 3 = 0.314

Peak Rating of Unit 1 = 126 MW

Area of Unit 1's Square Field = 3,980,000 m2

Peak Rating of Unit 1 per unit of square field area = 31.7 W/m2

Levelized (100% capacity factor) rating of Unit 1 per unit of square field area = 0.314 * 31.7 w/m2 = 9.96 W/m2

U.S. per capita electricity consumption is 1400 W/person (at 100% capacity factor)

Per capita land claim for electricity (per Ivanpah Unit 1) would be 1400/9.96 = 141 m2 per person

According to page 1-3 of the environmental impact statement, the power tower is 140 m tall, and Unit 1 has 55,000 heliostats, each having 14.08 m2 of reflective surface.

Mirror area of Unit 1 = 14.08 m2 * 55,000 = 774,400 m2

mirror-area / square-field-area = 0.195

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Telescopic heliostat fields are expected to produce 3 times the land yield of conventional heliostats, thereby reducing the land claim to 47 m2/person, increasing levelized (100% capacity factor) rating to 30 W/m2, and giving a 75% capacity factor (representative of a plant with half-day thermal storage) rating of 40 W/m2—all on the basis of square-field area.

75% capacity factor rating for a 1600 m x 1600 m unit would be 102 MW, or 920 MW on a quarter-township.

For these numbers to hold up, the mirror-area/square-field-area of a telescopic heliostat field must be better than 3 x 0.195 = 0.585

Starting from a covering factor of 0.91, and losing another 0.02 of covering factor around the lamp means that achieving 0.585 overall requires an intrinsic fill of 0.585/(0.91-0.02) = 0.66.

Comparison of conventional and telescopic heliostat fields at the same tower height

For the same height at the central receiver or beam-down optics, a telescopic heliostat field will have about twelve times the power rating of a conventional heliostat field. About a factor of three comes from increased field radius, and a about factor of four from improved land utilization.

For the same height at the central receiver or beam-down optics, a field of telescopic heliostats has about twelve times the power rating of a field of conventional heliostats. Of this factor of twelve, about a factor of three comes from increased field radius (the field radius is 14 times the tower height as opposed to 9 times) and about a factor of four comes from covering the land more densely with heliostat mirrors (81% mirror fill as opposed to 17%.)

Take for example the 160 m tower height of the solar plant now under construction in Crescent Dunes, Nevada. A telescopic heliostat field with beam-down optics topping out at a height of 160 m would have a heliostat field radius of 2225 m, and 81% mirror fill, giving an approximately 1.3 GW solar plant instead of the 110 MW the plant being built at Crescent Dunes. Significantly, with telescopic heliostats, this full-sized power plant would be ground-mounted rather than on a tower.

The radius/tower ratio of 14 for a field of telescopic heliostsats was calculated in a previous post.

The mirror fill of 81% for a field of telescopic heliostats was estimated as follows.

The packing efficiency of circles in a hexagonal arrangement on the plane is 0.907. Taking the mirror fill in the solid phase of the heliostat field to be 90%, the previous calculations assumed the mirror fill in the outermost ring of heliostats would be 0.6 of this value or 54%, so, on average, the mirror fill in the gas phase of the heliostat field will be roughly the mean of 54% and 90%, or 72%. Since the gas and solid phases of the heliostat field have equal areas, overall the mirror fill is the mean of 90% and 72%, or 81%.