IBM Sunflower (Welcome to the Thunder Dome II (part two)

IBM and Airlight team up to develop the Sunflower. HCPVT collector. (High Concentration Photovoltaic Thermal.)

Everything is better with a Swiss scientist to show you around, no?

I found this embedded here at Gizmag. A much better story than the others, thank goodness. The collector dish is more creative than the rest of their scheme, I think. They use a fibrous concrete for the dish. Vacuum shaped sheer sheets of metalized foils or the like for the compound primary (40 square meters!) There would need to be dynamic control of that vacuum as the atmospheric pressure changes you do not want a new focal length imposed as the weather and temperature changes....

This just in: a friend tracked down this EDN story. It is not too interested in the offboard bits (low temp implementations and balance of system stuff) but a nice juicy account of a voltage management scheme comes up late in the story, spoiler alert: something called a "Δ-converter" is important. As is putting this important voltage management gear pretty darn close to the cells. Or so it seems.

All of this is worrisome as these are the same cells that are sitting at a 2,000 suns focal point. I'm going to call this "putting all your eggs in one frying pan." Shows a whole lot of faith in the tracking and the cooling apparatus.

I also wonder which disconnections are requiring Flyback Diodes (freewheeling?) Dear readers, what do you see when you read that report. (The images on the EDN story seem to have been pulled. But the PDF still has them (download link here)

Japan rethinking distributed power

Like Hawaii before it, Japan is facing down "too much of a good thing" problem.

"Half of Japan's electric utilities move to restrict additional solar power"

 http://www.eenews.net/stories/1060006761

It will get worked out, but look for more of this kind of trouble before it settles down.

Cool tool to explore current energy use by buildings in the USofA

Take a look! they have about a million buildings (I wish it were not by state but by latitude) still lots and lots of cool data to play with.



www.buildingenergy.com

IBM - Welcome to the Thunder Dome II

I've been meaning to discuss and size up the IBM hybrid attempt. I saw their cell/module cooling device for large high concentration dishes awhile back. take a look:

 

Illustration from a Whitepaper on the IBM Sunflower (hybrid CPVT)

What do you see? you see water inlets and outlets for a mission critical back side cooling array. That is the left/bottom side plumbing bits. We cannot see the very smart way they put a high flow highly conductive network for flowing very close to the back of the cells (the 9 dark squares) For size you can see the thermocouple plugs (grey with two different sized and colored blades) they are about a half inch wide (just checked, .66 inches or 17 mm which means those cells are 10mm/10mm.


This needs to be really heat hardy as the cells are supposed to be exposed to some 2000 suns. The paper (or some-other source, they are starting to run-together, sorry) says they are backside conductor cells. Those black faces, unlined by traditional front-side conductors, are confirmation of that.

The two thermocouples are there to monitor the coolant temperature before and after to regulate the flow of coolant. This of course means they have the traditional tradeoff issues that I am trying to avoid with frequency splitting. If the temp goes up the voltage goes down and the electric yield drops. So they are stuck with a lot of very warm water as a product. The good news is they have a vision of this as a very large device and some ideas about what to do with the warm water. More on that in the next post.

I saw some confused notions about using this for boiling water for desalination. The description in that story is pretty vague and has a real units of measure problem. Maybe a deadline pressure meets domain knowledge weakness caused it. Anyhow, further looking shows they have a reverse osmosis scheme (in separate equipment) that uses pressure rather than brute force boiling (which is why reverse osmosis and the related technologies are being explored in general: less energy intensive.) The cooling circuit needs to be closed to keep the high purity and reliability going behind the cells.

We'll look at the collector's reflector array next time.

You get more of what you measure...

I had not noticed SolarThermalWorld until today. Looks like PVT is in a ghetto there too. Still some good coverage of PVT with a thermal emphasis. Fair enough. This story got my attention and maybe it should get yours.

Story here 

here is what jumped out for me:

• So far, PVT collectors have not been included in the standard. But there is already a so-called extended scope, which means that they may be included later in a second part of the standard.
• Fluid-based collectors will see some changes in their testing procedures compared to EN 12975-2. The new standard regards the collector gross area as the relevant reference for all area-specific data, e.g., the yield per area. Until now, the reference used in Germany has been the aperture area, which has presented some difficulties in comparing collector data on an international basis.

PVT with its interaction between the energy streams is going to be tough to pin down. My design has low interaction between the "sides" which is great for me but all of the hybrids are going to need to represent the various modes of operation and the variety of operating temperatures is vexing.

Hawaii - way out font. In a bad way.

Greentech media has a pretty good intro to the current state of things in the USA's most built out PV market: Hawaii.

story here

Among the things that stand out are

1) Many circuits on Oahu that are 120% of Daytime Minimum Load.  Too much of a good thing?
2) Discussion of the end of Net Metering. (duh!)

Some more up to date comparisons...

I'm off to work on Rev 2 of the design but it seems appropriate to layout why it is worth the bother.

Here are some comparisons to two good examples to give context :

Kyocera 325W Polycrystalline Solar Panel KD325GX-LPB
and (the awesome)
SunPower SPR-X20-445-COM (445 watts!)

Fortunately they are both 2.19 square meters each so watts per square meter STC can be derived but a better gauge is PTC (avail here) which mostly accommodates the Temperature Coefficient in a more real world manner:

Kyocera's goes down to 290.4 for the panel and so 132.6 per square meter
Sunpower goes down to 412.7 for the panel and so 188.45 per square meter
vs
Hybrid V1 is 23 watts per tube and 128 per square meter

We could imagine those panels reformed as magic edge-less strips as long and wide as our tubes and get
23.9 watts per strip from the Kyocera
33.9 watts per strip from the Sunpower
vs
23.0 watts from our tube (setting aside the thermal for the moment) 

How to layout the hybrid value? Here is an attempt at a tote board, normalized to per square meter



Top scored cells BOLD

OR if you'd rather:
1 panel of 2.19 square meters (1.66m X 1.32 m = 2.19 m^2) ≈ 12 Hybrid Rev 1 tubes ( .18 m square each X 12 tubes  = 2.16m^2 of area)

More on Hybrid version 1:
The Hybrid collector's first design iteration was analyzed in part by BRO (http://www.bro.com/) This design revealed some shortcomings that I've attacked in the version two but the analysis of version 1 can serve as a "floor" for evaluation. The figures were good enough to keep going on... Some of the shortcomings of the rev one design and their easy resolution I'll cover later. But for now Rev 1 is the best understood as far as throughput. I think 20% of the losses in Version 1 can be clawed back but all of this post is about Version 1.

For a square meter of tubular collector 320 watts of visible light hit the PV cells in clear light. That light arrives on 10X10mm cells at 46,700 W/m^2 (46.7 Suns.) The 320 watts would hit 98 10mmX10mm concentrator cells in that design. and the cells should be able to operate at @66C or below. They could be expected to run at 40% (due to the rich diet and the high concentration/low temp.) that 320W*.40= 128w =12.8% efficient (started vs the 1000 Wm^2 total light) on the PV side in realistic atmospheric conditions. There are troubles with that 12.8% number but they cut both ways. The fraction of incident light captured in the heat components is about the same (340W) but the conversion is much more efficient ~80% at 160C output temp. So 340W*.80=272 or 27% on the thermal side for a net 39.8%

Some of the columns need explication:
Relative Performance on a Heat Load:
Cogenera (in a white paper) sees the _heat value_ as 25% of electric value in a Watt to Watt comparison when that heat is delivered at Domestic Hot Water Temps. Sounds fair. So 128+(272*.25)=196. I weighted them all at the Sunpower as 1 (the conversion losses in electric resistance heat being very low, these correspond to the Gross Efficiency number.)

Cooling Power in Watts:
Cogenra shows the way again in a paper "Cooling with Cogen" they find the value of high temp heat used in chilling service to be higher than plain old thermal DHW service due to the COP (coefficient of power) in double effect chillers. Thus we get the "Cooling power in Watts" comparison. In most cases I imagine those "Cooling Watts" would be Watts not used ("negawatts" generated at peak rates) and potentially freeing up watts from the electrical side to sell at those peak rates or to otherwise address demand charge problems. All subject to the particular installation conditions and metering contracts of course.