Electrifying Ivanpah solar tower

Electrifying Ivanpah means actually electrifying the Ivanpah Solar Electric Generating System, which is a concentrated solar thermal power project currently under construction in the California Mojave Desert. It consists of three solar power towers, Ivanpah 1 (126 MW), Ivanpah 2 and 3 (each 133 MW). Their combined power output is 392 MW (gross) / 377 MW (net).

View of the 3 solar power towers at Ivanpah Picture 1

The three solar towers of the Ivanpah solar project.

How does the solar version of Ivanpah work

Diagram showing how Ivanpah concentrated solar power project works Picture 2

As picture 2 shows, sunlight is concentrated and reflected by mirrors at the wall of the SRSG (solar receiver steam generator), heating it to 1000 Celsius.

The SRSG consists of pipes through which water is pumped. Concentrated sun light heats the water, turning it into over 500 Celsius superheated steam.

This superheated steam is used to drive the turbine of a generator, producing electricity.

How to electrify Ivanpah solar tower

The electric emulation of the Ivanpah SRSG (solar receiver steam generator), the ESG (electric steam generator), is made by stacking electric furnaces, through which tubes for the water run. See picture 3 and 4. The electric furnaces are based on the one in picture 5.

Picture 3 Picture 4 Picture 5
Wall of eelctric furnaces functioning as SRSG Cross section view of wall made of electric furnaces Electric furnace 300 kW 1280 Celsius by Thermconcept
The Thermconcept  WK10000
Inside dimensions: 125 cm wide, 125 cm high, 700 cm deep, volume 10940 liters.
Power 300 kW. Maximum temperature 1280 Celsius.
Source: go here for brochure

According to this article, the Ivanpah SRSG is 17 meters high, unfortunately it does not mentions its width. Looking at picture 1 and 2, the SRSG has a rectangular shape, so it is safe to set its width at 17 meters.

In order to create the same heating surface for the ESG as the Ivanpah 2 SRSG, three WK10000 electric furnaces are needed to create the same width (actually two and half furnaces will do, since a furnace is 7 meters deep), and 17 electric furnaces have to be stacked in order to reach the same height (see picture 3). Resulting in a total of 51 (3 x 17) electric furnaces. Their combined energy consumption would be 15.300 kW (51 x 300 kW) or 15,3 MW.

Energy potential

The ESG has the same heating surface as the Ivanpah 2 SRSG and the temperature inside the ESG is the same as the temperature inside the Ivanpah 2 SRSG (1000 Celsius).

Ergo, the ESG should be able to heat the same quantity of water, produce the same quantity of superheated steam and consequently generate the same amount of energy (133 MW) as the Ivanpah 2 SRSG.

Efficiency of the ESG

Besides the energy for the electric furnaces, there is also energy needed to operate pumps etc. The combined gross output of the Ivanpah Solar Electric Generating System (consisting of three solar towers, each with one SRSG) is 392 MW, its net output is 377 MW. This means each solar tower / SRSG needs about 5 MW (392 MW - 377 MW / 3) to operate pumps etc.

This sets the power requirements of one ESG at ± 21 MW (15,3 MW for the electric furnaces + 5 MW for pumps etc.). This results in an ESG net output of 112 MW (133 MW - 21 MW).

Note: Even if four ESG's are needed to generate 133 MW, the net output would still be 49 MW (133 MW - 84 MW (4 x 21 MW)). Enough energy to power 30.000 homes.

Reasons the net output of the ESG might even be higher

1) The tubes of the Ivanpah SRSG are only heated from one side (see picture 2), the tubes in the ESG are heated from two sides (see picture 4). This means the surface of the tubes that is heated in the ESG is twice at large compared to the heated surface of the Ivanpah 2 SRSG tubes and water can be heated faster. Compare picture 6 and 7. This could result in more power being generated by the ESG.

For instance:
 A) Fewer loops are needed to pump water around, so the total volume of water being pumped around can be increased, resulting in a higher volume of steam.
B) If the same number of loops are maintained, the steam temperature will increase.

Picture 6 - cross section tube Ivanpah 2 SRSG Picture 7 - cross section tube ESG
Temperature profile of tube in Ivanpah SRSG Profile of tube in electric furnace heated from both sides
2) As picture 8 shows the heat distribution on the Ivanpah 2 SRSG is not homogeneous, also due to clouding there can be significant drops in temperature. Heat distribution in electric furnaces is more homogeneous because a fan is used to circulate the hot air, keeping it within the 5 Celsius range. Temperature fluctuations of are mainly due to hot swapping of electric heating elements during maintenance.

Picture 8  - temperature distribution on the Ivanpah SRSG

Temperature distribution on a Ivanpah 2 SRSG boiler

3) The example uses an off the shelf electric furnace. If the electric furnace and the boiler and piping would be designed as one unit, a higher efficiency rate would be possible.

4) Using thermoelectric generators to convert the heat that permeates the insulating and heat reflecting wall into electricity. See picture 9. The efficiency of thermoelectric generators increases every year and they can operate at ever higher temperatures. For instance thermoelectric generators made of tetrahedrite could reach 5 to 10 percent efficiency. 
E1 Thermoelectric Generator
E1 Thermoelectric Generator
E1 Thermoelectric Generator
E1 Thermoelectric Generator
In the future they might be integrated in or even replace the insulating and heat reflecting wall all together.

Picture 9 - Thermoelectric generators integrated in electric Ivanpah

Thermoelectric generators integrated in electric Ivanpah

5) The efficiency and potential calculations are conservative, this was done to be "on the safe side". If the exact measurements of the electric furnace are used, efficiency should be higher.

To give an indication:
The inner dimensions of the electric furnace are 700 cm wide, 125 cm high / deep. So to cover a width of 17 meters only 2.5 electric furnaces would be needed (17 / 7 = 2,5 (rounded)). Power requirement of one row of furnaces would be 750 kW (2.5 x 300 kW). Was 900 kW in conservative calculations.

The inner side is 125 cm high, to cover a height of  17 meters, 14 electric furnaces are needed  (17 / 1,25 = 14 (rounded)). Was 17 furnaces in conservative calculations.

Power requirement = 14 x 750 kW = 10500 kW = 10,5 MW. Previous power requirement was calculated at 15,3 MW. A difference in power requirement of 4,8 MW (for one side!).

Even if one looked at it from another angle, the margins are big.


Love to know what you think of this idea. Also, if you have more detailed technical information on the Ivanpah 2 SRSG, please tweet or email a link. Tried to look at it from another angle, but