UPDATE (Spring 2023) two important papers came out:

1) https://www.nature.com/articles/s41377-021-00465-1
​I was frankly thrilled when I found a paper this year from Gan Huang, Kai Wang & Christos N. Markides . Christos Markides is head of the Imperial College London’s Clean Energy Lab. 
It is an essential road map for anybody considering  spectral splitting and concentrating approaches. A must read paper. Markides’ inaugural lecture (video link) at ICL also addresses the domain.

The combination of spectrum splitting AND concentration AND PV cell species, taken all together are a pretty complex interactive domain. I had been working using a basic sense of the spectrum available and the response curves for different PV species (mostly Si and GaAs), together with the NREL research cell chart. Which, for my level of design thinking, was sufficient, or so I hoped. But that nature.com article is just the sort of fleshing out that is needed.

2) Here is a super comprehensive survey paper. Markides keeps piling on the good stuff! (with many co-authors) they really cover the hybrid landscape going back decades and up to today. Not just Spectrum Splitters but the whole rogues gallery of hybrid collection. 

Thanks Mini Maker Faire 2016 at Park Day School

Thanks everyone who came by for my show and tell. It was fun (my voice should be back tomorrow!)

Do hit me up if you had questions or suggestions of who to talk to to help me roll this project forward... More as I know it.

-Paul (paul@paulbostwick.com)

And a white paper (oldie but goodie) at www.solarspork.com

Since it was written, I have found some important loss mechanisms and buttoned them up. I have not had the funds to reanalyze the optic gains and "cash in" those improvements in a new analysis. The main new gain is from the enormous drop in the absorber(emitter) area. It is around .03 of the original area and the reemission is further suppressed by being aimed down into the mirror array rather than out to the cool sky directly. So together they should get our net efficiency of collection at 150C up. But the radiative exchanges are not the sort of things I intuit well - and why intuit when some physics (by smarter people) can do the trick.

The hunt for a suitable cell has hit a jackpot (but I am without funds to buy a small set) in three forms

Alta Devices: Gallium Arsenide thin film cells (I have to de-concentrate for now to use them) I have them in hand.

A small set of silicon concentrators rated for 70 suns (again de-concentrate to use them in prototyping/proof of concept work) that I got from a surplus.

An expensive in small quantities but right on the spec set of silicon "vertical Junction" cells of any size I need/want. I just have to give up $2000 for a minimum order (ugh.)

All of this is compromised by the un-patentability of the device: no monopoly on offer means the returns are compromised for me. I'll work it out, stay tuned!

Another hybrid... with huge heatpipes.

http://www.jetsongreen.com/2015/10/hybrid-solar-system-thats-very-efficient.html

here is the press release or whatever passes for one now... I don't see what they could have patented beyond the design. My main concern, looking now, is how material intensive it is. Those heat pipes are huge as they cover the whole exposed aperture. There are some black covers that may or may not be covering heat pipe material but even still the costs should be heroic - it is a copper one.

I'm jammed at work so finding the paper (if one exits) will have to wait. Check the comments - I'll add them there if and when I find it.

Hawaii is yet again giving us a look at the future

Here are some reports on the meaning and import of Hawaii ending net metering.

Rocky Mountain Institute has a report.

And here is a really good one from an investment blogging site seeking alpha.

Until now, net metering has amounted to protecting distributed generators from wholesale price fluctuations and the normal market price impacts of over-generation mid-day. Time Of Use pricing will follow the duck curve (duck curves actually) and solar will have to find new ways to cut costs and improve economic durability (delivering value in a way more independent of the grid).

The above stories plus my post from awhile back would make a fine primer on the near horizon of solar in early adopting states. California, I'm looking at you...

GE is jumping into empowering the utility user to participate in DR

This is interesting. GE is making a startup/relaunch/rebundle called Current.  They are committing huge resources to it.
(Dumb URL, imho, but whatever.)

I learned about it here.

Grid Edge? Demand Response? Demand Response 2.0? That is part of it, but they are also looking square in the face at energy as a service and that could be a potent, even "game changing" change. But their big company instincts and resources could doom them to sticking with a plan rather than scrap and pivot from one to the next.  Certainly one to watch.

Decloaking the High-Temperature Hybrid PVT collector

Long time no blog...

But I come with interesting news (or so I hope) so let's get started:

Back at the start of the High Temperature Hybrid PVT odyssey it was not even high temp, it was just an effort to cool the PV for higher performance in the summer. Then I started digging in to what to do with the heat. From there I moved onto the existing hybrids (discussed elsewhere in this blog).

In the early days, the theory was a mix of:
"This seems possible, but what am I missing?"
and
"Somebody must have already solved this problem..."

However, as time passed, I came to understand the compromises involved in cooling the photovoltaic components. Far more importantly, I've come to see the role of finance in shaping the evolution and distribution of solar systems. Much of this blog has been about that and the comings and goings within the concentrator and hybrid PVT segments of the solar collector industry.

Behind the scenes (the main subject of this post) I worked on filing (and the early arguments for) a patent on my version of a hybrid solar collector. The examiners were having none of it. Most of my accomplishments were (are) in the domain of radical simplification and substitution and I thought there was so much of that innovation that it constituted a new article... And it seemed that way at the start: the Korean examiner who did the WTO exam thought it was novel and useful - actually a subtly different standard for WTO but I passed that with flying colors. Anyhow, I knew from early on that Izumi was the high water mark for inventions in this domain:

that is just the first figure... Take a look at the whole thing, it is awesome:

"Hybrid solar collector for generating electricity and heat by separating solar rays into long wavelength and short wavelength"

He, Izumi, really understood the problem (long waves being counter-productive) and knew splitters could "save the day" and he mixed and matched in a variety of ways... so really look at them. In the weeds of the claims he does not gather the full value of what he shows, I believe. And he does not crack some practical problems and shows a lovely, fluid mind

Izumi's is THE best of the bunch. And I read all of these listed below (each number is a link) and many more not so on point to arrive at that conclusion.

22009 28264 32010 43208 102120 110811 120096 122010 0154865 201001 201001 201004 0251417 0252025 292010 292010 0432706 787145 980505 1068650 1220091 1386781 1663032 1683266 1837449 1855815 1946184 1989999 1989999 1993213 2133649 2141330 2205378 2243593 2247830 2277311 2460482 2687126 2872915 2872919 2906257 2907318 2920710 2969637 2969788 2969918 3125091 3171403 3227153 3245195 3262493 3273558 3514942 3861379 3868823 3884414 3889745 3915147 3952724 3960136 3982527 3985119 3988166 3990430 3995429 3999389 4002499 4003638 4016860 4018215 4024852 4027653 4027821 4033327 4036208 4038965 4043318 4045246 4048982 4048983 4059093 4064868 4069812 4074678 4080954 4088117 4108154 4119085 4120285 4122831 4126121 4127105 4129119 4133298 4142509 4149903 4149903 4150662 4151828 4153042 4171695 4186724 4198955 4213303 4217882 4232655 4234354 4240405 4262658 4273104 4275710 4282857 4303059 4304222 4306543 4307712 4319561 4355630 4377155 4426996 4474173 4553530 4559926 4644934 4653471 4687880 4687880 4700013 4723535 4723535 4834066 4892593 4911145 4949704 4987883 5123247 5309893 5309893 5365920 5466301 5466301 5468304 5555878 5653222 5727585 5927271 6047697 6057504 06080927 6705311 7142010 7388146 7607428 7688525 20041122 20082012 20082012 25082010 25082010 120100726 120100726 300200611

That is a copy/paste effort from my note file, so some look broken linkwise but take a look! There is some interesting stuff in there ... and this list excludes the foreign patents and the non patent art.. all of which is to say it was a BUNCH of stuff and Izumi's was the runaway best.

But even after some pointed back and forth with the patent examiners, my effort (coming in a moment) was seen as a mixture of many parts Izumi plus a few parts of other inventions.

California's Grid has overgeneration/curtailment problems too...

Check out this story at Breaking Energy.

in part:

Four times this past spring, the state’s grid operator had to shut off wind and solar power when it exceeded demand. The largest such curtailment was 1,100 megawatts during the morning of April 27, 2014.

Interesting, no?

That story comes from another source eenews.net and it is a pretty good report... down a bit there is this:

The plants that were curtailed likely received all of their contracted payments from the utilities, as contracts generally have a small curtailment provision built in. But as curtailment becomes more likely, contracts could become more flexible in the future, Bloom said.
"I think it means the contracts will allow for increased flexibility for dispatch by the utilities over time," he said. "There's a big change from the old days, when if you produced, they had to take it."
There will be a need to incorporate energy storage into renewables projects, as well. Right now, a solar project without storage would beat out one with storage solely on cost, even though utilities are under a new mandate as of last year to procure 1.3 gigawatts of storage by 2020.

The grid as free battery is on the way out as the importance of "when" grows. I've been wrapped up on Patent issues and missed the "Duck Curve" as a concept. Let's look into that shall we?

here is a "distributed generators fight back" read on the duck curve:

Solar supporters: Open season utilities duck on Ilsr.org:

"The duck is the perfect vehicle for utility complaints because it casts the growth of distributed solar as a major technical problem (an area where most policy makers defer to utilities) rather than an economic one, where utility complaints can be contrasted with their customer’s desires for more local control over their energy use and costs."

That 5 to 8 ramp is something else! It is certainly a call for west facing PV arrays... And some short-term storage too. What might many solar pre-chilling of HVAC condensers do to that picture? Could a daytime version of the Ice Bear eat the Utilities Duck? The Ice Energy people are used to marketing to utilities (smart) but the other side is also serviceable if you have surplus generation that would be curtailed during the day - better to shunt it to ice and then pull out that service during the peak charge time of 5 to 8...
"Short term storage, meet solar thermal, solar thermal, meet short term storage.