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).

Picture 1
The three solar towers of the Ivanpah solar project.

How does the solar version of Ivanpah work

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 


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 potentialThe
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 


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 SRSG3)
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 Ivanpah5) 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.
Feedback
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